Compounds for use in in vivo fluorescence-lifetime imaging

Abstract

The present invention concerns compounds for use in in vivo fluorescence-lifetime imaging. The compounds have the general formula (I) below:

Description

[0001] 1 COMPOUNDS FOR USE IN IN VIVO FLUORESCENCE-LIFETIME IMAGING The present invention concerns compounds for use in in vivo fluorescence-lifetime imaging. Said invention also concerns new compounds, process of preparation and use 5 thereof. Among the methods for visualising and / or identifying biological processes or biological tissues in vivo using contrast agents, optical imaging has shown itself to be promising and attractive, with its relatively low cost, high sensitivity, simple instrumentation and use of non-ionising radiations. One of the major applications of this type of imaging is 10 fluorescence guided surgery (FGS). Surgeons rely on visual inspection or palpation to determine the boundary between diseased tissue to be excised and healthy tissue, which does not always guarantee complete resection, thus increasing the risk of recurrence after tumour removal. In this context, fluorescence imaging makes it possible to highlight cancer cells and 15 provides intraoperative data enabling the surgeon to take the necessary margins for complete resection of the tumour mass. However, traditional optical imaging has its limitations. Conventional systems detect the total fluorescence intensity emitted by a sample. But fluorescence intensity depends on the quantity of fluorophore accumulated, which is related to the size and / or thickness of the 20 tumour, and detecting small lesions can thus be more complex. Fluorescence intensity is also strongly affected by the absorption / scattering of light by the tissues and by autofluorescence generated by the tissues themselves. A new optical imaging method, Fluorescence Lifetime Imaging (FLT), has emerged in this context, based not on the measurement of fluorescence intensity but on the 25 measurement of the time that a fluorophore spends in the excited state (lifetime). Fluorescence lifetime refers to the average time a fluorophore spends in its excited state before emitting a photon and returning to the ground state. FLT measures the decay of fluorescence over time, offering insights into the molecular environment and interactions of fluorophores. FLT uses time-correlated single photon counting (TCSPC) or other time- 30 resolved techniques to capture the time delay between the excitation pulse and the emission of each photon. FLT also provides spatial information by analysing the fluorescence lifetime on a pixel-by-pixel basis, allowing the creation of lifetime maps. 2 Compared with fluorescence intensity, the fluorescence lifetime provides a stable measurement method which is less susceptible to artifacts arising from tissue absorption and scattering, excitation intensity variations, probes photobleaching, or unknown tissue penetration depth. 5 It means that many of the limitations mentioned above can possibly be overcome. Measuring the lifetime of a compound in vivo is indeed independent of the concentration of the fluorescent probe and of the intensity of the excitation light source, and is often a unique indicator of the local tissue environment. Lifetime imaging has better sensitivity and specificity for distinguishing fluorescent tracers from tissue autofluorescence and non- 10 specific tracer accumulation. With this method, the depth of penetration is also increased with a measurement that is less subject to light scattering / absorption phenomena. Lifetime imaging shows a significant improvement in contrast between the targeted tumour and the background noise compared with conventional optical imaging based on measurements of the intensity of the emitted light. 15 However, a barrier to the clinical development of this technology is the lack of fluorescent probes with both near infrared (NIR) emission, which is a prerequisite for in vivo use, and a lifetime greater than 1 ns in the biological environment. Cameras developed for lifetime imaging are indeed generally used with fluorophores already approved for clinical applications, which are characterised by good properties in terms of brightness in the NIR 20 range, but lifetimes of less than a nanosecond. These short lifetimes make their detection complex, with a low differential compared with biological tissues. The development of fluorophores with lifetimes greater than 1.5 or 2 ns in a biological environment is therefore a prerequisite for the emerging use of this imaging method in clinical applications. Until now, research has focused on the development of more powerful camera 25 systems to measure the fluorescence lifetime of compounds in real time. Numerous devices, cameras and sensors have been developed for this application. In sharp contrast, little research has been carried out to identify and use compounds that are better suited to fluorescence lifetime in vivo. As tissue autofluorescence is less marked above 650 nm, it is desirable to use fluorescent probes emitting in the NIR. 30 Proofs of concept for FLT imaging began with the study of compounds that do not emit in the NIR, such as GFP (emission centred around 510 mm), but have a relatively long lifetime (> 2 ns), making it possible to discriminate between emitted fluorescence and tissue autofluorescence. 3 However, the organic fluorophores currently used in the NIR, such as ICG or IRDye800CW, have a lifetime of less than 1 ns in a biological environment, which makes their detection complex. There is a thus need for the development of new molecular tools for FLT. 5 Accordingly, it is an object of the present invention to provide NIR-emitting compounds aimed to be used in in vivo FLT, with lifetimes greater than 1, 1.5 or even 2, 3 or 4 ns. Such lifetimes, longer than those currently achieved by commercially available NIR fluorescent molecules, are particularly advantageous to facilitate their detection while injected in vivo for imaging. 10 Another aim of the invention is to provide compounds with good photophysical characteristics in the NIR (high quantum yield and molar absorption coefficient) under physiological conditions. Another aim of the invention is to provide compounds with improved photostability compared with reference products (ICG, IRDye800CW). 15 Another aim of the invention is to provide compounds that can be easily modified, so that they can: - have enhanced biocompatibility; - be encapsulated within nanoparticles; - exhibit a certain sensitivity in terms of fluorescence to different physiological 20 conditions (pH, oxygen content, presence of particular enzymes, polarity and viscosity of certain cell organelles, etc.) and become so-called 'responsive' probes to changes in its environment; and / or - be conjugated to a biological vector (antibodies, antibody fragments, peptide ligands, etc.) for specific targeting of tumours or other tissues in vivo, or to a chelator 25 (synthesis of bimodal imaging agents using optical (FLT) and nuclear (PET and / or SPECT) modalities, or multimodal imaging agents using classical optical, FLT and radio-imaging modalities). Thus, the present invention relates to a compound of following formula (I): (I), 4 wherein: R1, R2, R3 and R4, identical or different, represent a C5-C7 aryl or heteroaryl group, in particular a phenyl or a thiophenyl group, optionally substituted with at least one group chosen from halogen, nitro, -NRcRd, -ORd, hydrazine, -CF3, -CN, and groups constituted by 5 or comprising a linker L and at least one group V, R5 and R6, identical or different, represent a hydrogen, a halogen, a linear or branched (C1- C15)-group comprising an aldehyde, ketone, carboxylic acid or ester function, a nitrile, a sulfonate, a vinyl group optionally substituted by a ketone, ester or aromatic group, an imine substituted by an alkyl or aromatic group, an alkyne group optionally substituted by an alkyl10or aromatic group, SPh, an aromatic chalcogen (SePh, TePh), an amide, a C5-C7 aryl or heteroaryl group, optionally substituted by at least one group chosen from a halogen, - NRcRd, -ORd, hydrazine, -CF3 and -CN, optionally R4 and R5 and / or R3 and R6 are covalently bonded and together form a C5-C7 aryl or heteroaryl group, or a polycyclic aromatic group, optionally substituted by at least one 15 group chosen from (C1-C6)-alkyl, halogen, -NRcRd, -ORd, hydrazine, -CF3and -CN, Rc and Rd, identical or different, represent hydrogen or a linear or branched (C1-C50)-alkyl group, optionally interrupted by at least one atom or group chosen from -O-, -NR-, -S-, - C(=O)-, -O-C(=O)-, -C(=O)-O-, -NR-C(=O)-, -C(=O)-NR-, -NR-C(=O)-NR’-, -NR-C(=S)- NR’-, -NR-C(=O)-O-, -O-C(=O)-NR’-, -C(R)=C(R’)-, -C≡C-, arene diyl, in particular 20 benzene diyl, and heteroarene diyl, optionally substituted by at least one group comprising one or more heteroatoms chosen from O, N, P and / or S, in particular a group chosen from quaternary ammonium, sulphate, sulfonate, and phosphonate, Ra and Rb, identical or different, represent: - a linear or branched (C1-C50)-alkyl group, optionally interrupted by at least one atom25 or group chosen from -O-, -NR-, -N+RR’-, -S-, -C(=O)-, -O-C(=O)-, -C(=O)-O-, - NR-C(=O)-, -C(=O)-NR-, -NR-C(=O)-NR’-, -NR-C(=S)-NR’-, -NR-C(=O)-O-, -O- C(=O)-NR’-, -C(R)=C(R’)-, -C≡C-, arene diyl, in particular benzene diyl, and heteroarene diyl, - a group constituted by or comprising a linker L and at least one group V, 30 V is chosen from: - groups comprising one or more heteroatoms chosen from O, N, P and / or S, in particular a group chosen from quaternary ammonium, sulphate, sulfonate, and phosphonate, 5 - bioconjugable groups, in particular chosen from amine, ammonium, carboxylic acid, activated esters, in particular N-hydrosuccinimidyl, N-hydroxysulfosuccinimide, pentafluorophenyl, tetrafluorophenyl, squarate, in particular diethylsquarate, maleimide, thiol, isothiocyanate, isocyanate, oxadiazolyl methyl sulfone, azoture or 5 azide, optionally substituted tetrazine, triazole, alkyne, in particular terminal alkyne, trans-cyclooctene, cyclooctyne, in particular dibenzocyclooctyne and bicyclononyne, - fluorescence quencher groups, for example diazo groups or diazo-containing groups, - a biological vector, in particular a cyclic or linear peptide, an antibody, an antibody 10 fragment, a nanobody, an affibody, an aptamer, a short DNA or RNA sequence, a polysaccharide, a lipid, a sugar, an amino acid, a vitamin, a AMD3100 or AMD3100- type molecule, a prostate-specific membrane antigen (PSMA) ligand, a steroid, a fatty acid, a polyamine, a polyphenol, a DNA base or a caffeine derivative, - a nanoparticle, in particular a nanoparticle of 10 kDa or less or lipidic nanoparticles, 15 more particularly a gold nanocluster or a lipid nanoparticle, for example a lipidot, - a metal complex, in particular for therapeutic purposes, formed by a chelating agent and a metal, - a radiometallic complex, formed by a chelating agent, for example DOTA (1,4,7,10- tetraazacyclododecane-1,4,7,10-tetraacetic acid), and a radiometal, in particular for 20 therapeutic or diagnostic purposes, - a metal or radiometal chelating agent, for example DOTA, L is in particular a linear or branched (C1-C50)-alkyl group, optionally interrupted by at least one atom or group chosen from -O-, -NR-, -S-, -C(=O)-, -O-C(=O)-, -C(=O)-O-, -NR- C(=O)-, -C(=O)-NR-, -NR-C(=O)-NR’-, -NR-C(=S)-NR’-, -NR-C(=O)-O-, -O-C(=O)- 25 NR’-, -C(R)=C(R’)-, -C≡C-, arene diyl, in particular benzene diyl, and heteroarene diyl, R and R’, identical or different, represent hydrogen or a linear or branched (C1-C6)-alkyl group, or one of its tautomers, with the proviso that:30- at least one of R3 and R4, in particular R3 and R4, represent(s) a C5-C7 heteroaryl group, in particular a thiophenyl group, optionally substituted with at least one group chosen from halogen, -NRcRd, -ORd, hydrazine, -CF3, -CN, and groups constituted by or comprising a linker L and at least one group V, with, in this case, R1 and / or R2 6 being different from p-N(Me)2-phenyl, and optionally Raand / or Rbbeing further different from -C≡C-CH2-NH(CH3)2 and / or -C≡C-CH2-N+( CH3)3, in particular different from -C≡C-CH2-NH(CH3)2; - at least one of Raand Rbrepresents a group V’ of following formula -La-X-Lb-V, 5 wherein La and Lb, identical or different, represent a linear or branched (C1-C50)- alkyl group, optionally interrupted by at least one atom or group chosen from -O-, - S-, -C(R)=C(R’)-, -C≡C-, X represents -NR- or -N+RR’-, and V is as defined above; - at least one of R1, R2, R3 and R4, in particular one of R1, R2, R3 and R4, represents a C5-C7 aryl or heteroaryl group, substituted with at least one group chosen from 10 groups constituted by or comprising a linker L and at least one group V; and / or - R4 and R5 and / or R3 and R6 are covalently bonded and together form a C5-C7 aryl or heteroaryl group, or a polycyclic aromatic group, optionally substituted by at least one group chosen from (C1-C6)-alkyl, halogen, -NRcRd, -ORd, hydrazine, -CF3and - CN. 15 In a particular embodiment, R5 and / or R6, in particular R5 and R6, represent a hydrogen. In a particular embodiment, R1and / or R2, in particular R1and R2, represent a C5-C7aryl, optionally substituted with at least one group chosen from halogen, nitro, -NRcRd, - ORd, hydrazine, -CF3, -CN, and groups constituted by or comprising a linker L and at least 20 one group V. In a particular embodiment, R1 and / or R2, in particular R1 and R2, represent a C5-C7 aryl, optionally substituted with at least one group chosen from halogen, nitro, -NRcRd, - ORd, hydrazine, -CF3, -CN. In a particular embodiment, R1 and / or R2, in particular R1 and R2, represent a phenyl, 25 optionally substituted with at least one group chosen from halogen, nitro, -NRcRd, -ORd, hydrazine, -CF3, and -CN. In a particular embodiment, R3and / or R4, in particular R3and R4, represent a heteroaryl group, optionally substituted with at least one group chosen from halogen, nitro, -NRcRd, -ORd, hydrazine, -CF3, -CN, and groups constituted by or comprising a linker L and 30 at least one group V. In a particular embodiment, R3 and / or R4, in particular R3 and R4, represent a heteroaryl group, optionally substituted with at least one group chosen from halogen, nitro, -NRcRd, -ORd, hydrazine, -CF3, and -CN. 7 In a particular embodiment, R3and / or R4, in particular R3and R4, represent a heteroaryl group, optionally substituted with at least one group chosen from halogen, nitro, -NRcRd, -ORd, hydrazine, -CF3, and -CN, and Raand / or Rb, in particular Raand Rb, represent(s) -C≡C-CH2-NRR’ or -C≡C-CH2-N+RR’R’’, with R, R’ and R’’, identical or 5 different, representing hydrogen or a linear or branched (C1-C6)-alkyl group. In a particular embodiment, R3and / or R4, in particular R3and R4, represent a thiophenyl group, optionally substituted with at least one group chosen from halogen, nitro, -NRcRd, -ORd, hydrazine, -CF3, and -CN. In a particular embodiment, R3 and / or R4, in particular R3 and R4, represent a 10 thiophenyl group, optionally substituted with at least one group chosen from halogen, nitro, -NRcRd, -ORd, hydrazine, -CF3, and -CN, and Raand / or Rb, in particular Raand Rb, represent(s) -C≡C-CH2-NRR’ or -C≡C-CH2-N+RR’R’’, with R, R’ and R’’, identical or different, representing hydrogen or a linear or branched (C1-C6)-alkyl group. In a particular embodiment, R4 and R5 and / or R3 and R6, in particular R4 and R5, and 15 R3and R6, are covalently bonded and together form a C5-C7aryl or heteroaryl group, or a polycyclic aromatic group, optionally substituted by at least one group chosen from (C1-C6)- alkyl, halogen, -NRcRd, -ORd, hydrazine, -CF3 and -CN, R4and R5and / or R3and R6, in particular R4and R5, and R3and R6, forming for example a fluorene, optionally substituted by at least one group chosen from (C1-C6)-alkyl, halogen, - 20 NRcRd, -ORd, hydrazine, -CF3 and -CN. In a particular embodiment, R4 and R5 and / or R3 and R6, in particular R4 and R5, and R3and R6, are covalently bonded and together form a C5-C7aryl or heteroaryl group, or a polycyclic aromatic group, optionally substituted by at least one group chosen from (C1-C6)- alkyl, halogen, -NRcRd, -ORd, hydrazine, -CF3 and -CN, and Raand / or Rb, in particular Ra25 and Rb, represent(s) -C≡C-CH2-NRR’ or -C≡C-CH2-N+RR’R’’, with R, R’ and R’’, identical or different, representing hydrogen or a linear or branched (C1-C6)-alkyl group, R4and R5and / or R3and R6, in particular R4and R5, and R3and R6, forming for example a fluorene, optionally substituted by at least one group chosen from (C1-C6)-alkyl, halogen, -NRcRd, -ORd, hydrazine, -CF3 and -CN. In a particular embodiment, R1 and / or R2,30in particular R1 or R2, represent a C5-C7 aryl or heteroaryl group, substituted with at least one group Q constituted by or comprising a linker L and at least one group V. 8 In a particular embodiment, R1and / or R2, in particular R1or R2, represent a C5-C7aryl, substituted with at least one group Q constituted by or comprising a linker L and at least one group V. In a particular embodiment, R1and / or R2, in particular R1or R2, represent a phenyl, 5 substituted with at least one group Q constituted by or comprising a linker L and at least one group V. In a particular embodiment, R3and / or R4, in particular R3or R4, represent a C5-C7aryl or heteroaryl group, substituted with at least one group Q constituted by or comprising a linker L and at least one group V.10In a particular embodiment, R3 and / or R4, in particular R3 or R4, represent a C5-C7 aryl, substituted with at least one group Q constituted by or comprising a linker L and at least one group V. In a particular embodiment, R3 and / or R4, in particular R3 or R4, represent a phenyl, substituted with at least one group Q constituted by or comprising a linker L and at least one 15 group V. In a particular embodiment, Q is of formula -X-La-X’-Lb-V, wherein: X and X’ represent independently -O-, -NR-, -S-, -C(=O)-, -O-C(=O)-, -C(=O)-O-, -NR- C(=O)-, -C(=O)-NR-, -NR-C(=O)-NR’-, -NR-C(=S)-NR’-, -NR-C(=O)-O-, -O-C(=O)- NR’-, -C(R)=C(R’)-, -C≡C-, arene diyl, in particular benzene diyl, or heteroarene diyl, with20R and R’, identical or different, representing hydrogen or a linear or branched (C1-C6)-alkyl group, X being for example -O-, and / or X’ being for example -O-C(=O)-, -C(=O)-O-, -NR- C(=O)-, or -C(=O)-NR-, La and Lb, identical or different, represent a linear or branched (C1-C50)-alkyl group, optionally interrupted by at least one atom or group chosen from -O-, -S-, -C(R)=C(R’)-, - 25 C≡C-, La being for example a linear or branched (C1-C50)-alkyl group, and / or Lb being for example a linear or branched (C1-C50)-alkyl group, optionally interrupted by at least one atom -O-, V is as defined above, L being more particularly -O-CH2-C(=O)-NH-L’, with L’ being a linear or branched (C1-30C50)-alkyl group, optionally interrupted by at least one atom -O-. In a particular embodiment, R3and / or R4, in particular R3or R4, represent a C5-C7aryl or heteroaryl group, substituted with at least one group Q constituted by or comprising a linker L and at least one group V, 9 said group being in particular -X-La-X’-Lb-V, wherein: X and X’ represent independently -O-, -NR-, -S-, -C(=O)-, -O-C(=O)-, -C(=O)-O-, -NR- C(=O)-, -C(=O)-NR-, -NR-C(=O)-NR’-, -NR-C(=S)-NR’-, -NR-C(=O)-O-, -O-C(=O)- NR’-, -C(R)=C(R’)-, -C≡C-, arene diyl, in particular benzene diyl, or heteroarene diyl, with 5 R and R’, identical or different, representing hydrogen or a linear or branched (C1-C6)-alkyl group, X being for example -O-, and / or X’ being for example -O-C(=O)-, -C(=O)-O-, -NR- C(=O)-, or -C(=O)-NR-, Laand Lb, identical or different, represent a linear or branched (C1-C50)-alkyl group, optionally interrupted by at least one atom or group chosen from -O-, -S-, -C(R)=C(R’)-, -10C≡C-, La being for example a linear or branched (C1-C50)-alkyl group, and / or Lb being for example a linear or branched (C1-C50)-alkyl group, optionally interrupted by at least one atom -O-, V is as defined above, L being more particularly -O-CH2-C(=O)-NH-L’, with L’ being a linear or branched (C1- 15 C50)-alkyl group, optionally interrupted by at least one atom -O-, and Raand / or Rb, in particular Raand Rb, represent(s) -C≡C-CH2-NRR’ or -C≡C-CH2- N+RR’R’’, with R, R’ and R’’, identical or different, representing hydrogen or a linear or branched (C1-C6)-alkyl group. In a particular embodiment, Raand / or Rb, in particular Raand Rb, represent(s) -C≡20 C-CH2-NRR’ or -C ≡ C-CH2-N+RR’R’’, with R, R’ and R’’, identical or different,representing hydrogen or a linear or branched (C1-C6)-alkyl group. In a particular embodiment, at least one of Raand Rb, in particular Raor Raand Rb, represent(s) a group constituted by or comprising a linker L and at least one group V. In a particular embodiment, at least one of Raand Rb, in particular Raor Raand Rb, 25 represent(s) a group V’ of following formula -La-X-Lb-V, wherein La and Lb, identical or different, represent a linear or branched (C1-C50)-alkyl group, optionally interrupted by at least one atom or group chosen from -O-, -S-, -C(R)=C(R’)-, -C≡C-, X represents -NR- or - N+RR’-, and V is as defined above. In a more particular embodiment, La represents a linear or branched (C1-C50)-alkyl 30 group, interrupted by a -C≡C- group. In another more particular embodiment, Lbrepresents a linear or branched (C1-C50)- alkyl group, interrupted by at least one O atom, Lb representing in particular a PEG group. 10 In another more particular embodiment, Raand / or Rb, in particular Raand Rb, represent(s) a group of formula -C≡C-CH2-NR-Lb-V or -C≡C-CH2-N+RR’-Lb-V, wherein Lb, R, R’, and V are as defined above, being in particular -C≡C-CH2-NMe-Lb-V or -C≡C- CH2-N+(Me)2-Lb-V, Lb representing more particularly a linear or branched (C1-C50)-alkyl 5 group or a PEG group. In a particular embodiment: - R1 and / or R2, in particular R1 or R2, represent a C5-C7 aryl or heteroaryl group, notably a C5-C7aryl, for example a phenyl, substituted with at least one group constituted by or comprising a linker L and at least one group V; 10 - R3 and / or R4, in particular R3 or R4, represent a C5-C7 aryl or heteroaryl group, notably a C5-C7 aryl, for example a phenyl, substituted with at least one group constituted by or comprising a linker L and at least one group V; and / or, preferably or - at least one of Raand Rb, in particular Raor Raand Rb, represent(s) a group constituted 15 by or comprising a linker L and at least one group V, notably at least one of Raand Rb, in particular Raor Raand Rb, representing a group V’ of following formula -La- X-Lb-V, wherein La and Lb, identical or different, represent a linear or branched (C1- C50)-alkyl group, optionally interrupted by at least one atom or group chosen from - O-, -S-, -C(R)=C(R’)-, -C≡C-, X represents -NR- or -N+RR’-, and V is as defined 20 above, with La representing for example a linear or branched (C1-C50)-alkyl group, interrupted by a -C≡C- group, and / or Lb representing for example a linear or branched (C1-C50)-alkyl group, interrupted by at least one O atom, Lbrepresenting for instance a PEG group. In a particular embodiment, V is chosen from: 25 - groups comprising one or more heteroatoms chosen from O, N, P and / or S, in particular a group chosen from quaternary ammonium, sulphate, sulfonate, and phosphonate, in particular sulfonate, - bioconjugable groups, in particular chosen from amine, ammonium, carboxylic acid, activated esters, in particular N-hydrosuccinimidyl, N-hydroxysulfosuccinimide, 30 pentafluorophenyl, tetrafluorophenyl, squarate, in particular diethylsquarate, maleimide, thiol, isothiocyanate, isocyanate, oxadiazolyl methyl sulfone, azoture or azide, optionally substituted tetrazine, triazole, alkyne, in particular terminal alkyne, 11 trans-cyclooctene, cyclooctyne, in particular dibenzocyclooctyne and bicyclononyne, - fluorescence quencher groups, for example diazo groups or diazo-containing groups, - a metal or radiometal chelating agent, for example DOTA (1,4,7,10- 5 tetraazacyclododecane-1,4,7,10-tetraacetic acid). In a particular embodiment, the compound of the invention is chosen from:

[0002] 15 , said compounds being optionally, if applicable, in the form of a formate or trifluoroacetate salt. In another aspect, the present invention also concerns a compound of following 5 formula (II), for use in a method of in vivo fluorescence-lifetime imaging: 16 ), wherein: W is chosen from B, PO2, Ga, Al, In, Ru, Fe, Pt, Pd, Zr, Zn, Cu, Bi, Sb, Au, Rh, Ge, Sn, Ti; W being in particular B; 5 Y is N or CZ, Y being in particular N; Z is chosen from: - H; - Halogens; - OR’’ and SR’’, wherein R’’ represents hydrogen or a linear or branched (C1-C6)- 10 alkyl group; - linear or branched (C1-C6)-alkyl group; - a C5-C7aryl or heteroaryl group being optionally substituted with at least one group chosen from halogen, nitro, -NRcRd, -ORd, hydrazine, -CF3, -CN, and groups constituted by or comprising a linker L and at least one group V, 15 R1, R2, R3and R4, identical or different, represent a linear or branched (C1-C6)-alkyl group, a C5-C7aryl or heteroaryl group, a -CH2=CH2-(C5-C7) aryl or -CH2=CH2-(C5-C7) heteroaryl group, said aryl or heteroaryl group being optionally substituted with at least one group chosen from halogen, nitro, -NRcRd, -ORd, hydrazine, -CF3, -CN, and groups constituted by or comprising a linker L and at least one group V, 20 R5 and R6, identical or different, represent a hydrogen, a halogen, a linear or branched (C1- C15)-group comprising an aldehyde, ketone, carboxylic acid or ester function, a nitrile, a sulfonate, a vinyl group optionally substituted by a ketone, ester or aromatic group, an imine substituted by an alkyl or aromatic group, an alkyne group optionally substituted by an alkyl or aromatic group, SPh, an aromatic chalcogen (SePh, TePh), an amide, a C5-C7 aryl or25 heteroaryl group, optionally substituted by at least one group chosen from a halogen, - NRcRd, -ORd, hydrazine, -CF3and -CN, optionally R4 and R5 and / or R3 and R6 are covalently bonded and together form a C5-C7 aryl or heteroaryl group, or a polycyclic aromatic group, optionally substituted by at least one group chosen from (C1-C6)-alkyl, halogen, -NRcRd, -ORd, hydrazine, -CF3and -CN, 17 Rcand Rd, identical or different, represent hydrogen or a linear or branched (C1-C50)-alkyl group, optionally interrupted by at least one atom or group chosen from -O-, -NR-, -S-, - C(=O)-, -O-C(=O)-, -C(=O)-O-, -NR-C(=O)-, -C(=O)-NR-, -NR-C(=O)-NR’-, -NR-C(=S)- NR’-, -NR-C(=O)-O-, -O-C(=O)-NR’-, -C(R)=C(R’)-, -C≡C-, arene diyl, in particular 5 benzene diyl, and heteroarene diyl, optionally substituted by at least one group comprising one or more heteroatoms chosen from O, N, P and / or S, in particular a group chosen from quaternary ammonium, sulphate, sulfonate, and phosphonate, Raand Rb, identical or different, are absent or represent: - a halogen, in particular -F or -Cl,10- a linear or branched (C1-C50)-alkyl group, optionally interrupted by at least one atom or group chosen from -O-, -NR-, -N+RR’-, -S-, -C(=O)-, -O-C(=O)-, -C(=O)-O-, - NR-C(=O)-, -C(=O)-NR-, -NR-C(=O)-NR’-, -NR-C(=S)-NR’-, -NR-C(=O)-O-, -O- C(=O)-NR’-, -C(R)=C(R’)-, -C≡C-, arene diyl, in particular benzene diyl, and heteroarene diyl, 15 - a group constituted by or comprising a linker L and at least one group V, Ra and Rb are absent when W is chosen from PO2, Ga, Al, In, Ru, Fe, Pt, Pd, Zr, Zn, Cu, Bi, Sb, Au, Rh, Ge, Sn, Ti; Raand Rbare present when W is B; V is chosen from: 20 - groups comprising one or more heteroatoms chosen from O, N, P and / or S, in particular a group chosen from quaternary ammonium, sulphate, sulfonate, and phosphonate, - bioconjugable groups, in particular chosen from amine, ammonium, carboxylic acid, activated esters, in particular N-hydrosuccinimidyl, N-hydroxysulfosuccinimide, 25 pentafluorophenyl, tetrafluorophenyl, squarate, in particular diethylsquarate, maleimide, thiol, isothiocyanate, isocyanate, oxadiazolyl methyl sulfone, azoture or azide, optionally substituted tetrazine, triazole, alkyne, in particular terminal alkyne, trans-cyclooctene, cyclooctyne, in particular dibenzocyclooctyne and bicyclononyne, 30 - fluorescence quencher groups, for example diazo groups or diazo-containing groups, - a biological vector, in particular a cyclic or linear peptide, an antibody, an antibody fragment, a nanobody, an affibody, an aptamer, a short DNA or RNA sequence, a polysaccharide, a lipid, a sugar, an amino acid, a vitamin, a AMD3100 or AMD3100- 18 type molecule, a prostate-specific membrane antigen (PSMA) ligand, a steroid, a fatty acid, a polyamine, a polyphenol, a DNA base or a caffeine derivative, - a nanoparticle, in particular a nanoparticle of 10 kDa or less or lipidic nanoparticles, more particularly a gold nanocluster or a lipid nanoparticle, for example a lipidot, 5 - a metal complex, in particular for therapeutic purposes, formed by a chelating agent and a metal, - a radiometallic complex, formed by a chelating agent, for example DOTA (1,4,7,10- tetraazacyclododecane-1,4,7,10-tetraacetic acid), and a radiometal, in particular for therapeutic or diagnostic purposes, 10 - a metal or radiometal chelating agent, for example DOTA, L is in particular a linear or branched (C1-C50)-alkyl group, optionally interrupted by at least one atom or group chosen from -O-, -NR-, -S-, -C(=O)-, -O-C(=O)-, -C(=O)-O-, -NR- C(=O)-, -C(=O)-NR-, -NR-C(=O)-NR’-, -NR-C(=S)-NR’-, -NR-C(=O)-O-, -O-C(=O)- NR’-, -C(R)=C(R’)-, -C≡C-, arene diyl, in particular benzene diyl, and heteroarene diyl, 15 R and R’, identical or different, represent hydrogen or a linear or branched (C1-C6)-alkyl group, or one of its tautomers. In a particular embodiment, more particularly when Raand Rbare absent, the coordination sphere of W may be completed with one or more ligands, for example a solvent 20 molecule, notably chosen from pyridine, water, methanol, ethanol, tetrahydrofuran (THF). In a particular embodiment, the present invention also concerns a compound of following formula (II1), for use in a method of in vivo fluorescence-lifetime imaging: (II1), wherein: 25 Y is N or CH; R1, R2, R3and R4, identical or different, represent a C5-C7aryl or heteroaryl group, optionally substituted with at least one group chosen from halogen, nitro, -NRcRd, -ORd, hydrazine, - CF3, -CN, and groups constituted by or comprising a linker L and at least one group V, 19 R5and R6, identical or different, represent a hydrogen, a halogen, a linear or branched (C1- C15)-group comprising an aldehyde, ketone, carboxylic acid or ester function, a nitrile, a sulfonate, a vinyl group optionally substituted by a ketone, ester or aromatic group, an imine substituted by an alkyl or aromatic group, an alkyne group optionally substituted by an alkyl 5 or aromatic group, SPh, an aromatic chalcogen (SePh, TePh), an amide, a C5-C7aryl or heteroaryl group, optionally substituted by at least one group chosen from a halogen, - NRcRd, -ORd, hydrazine, -CF3and -CN, optionally R4and R5and / or R3and R6are covalently bonded and together form a C5-C7aryl or heteroaryl group, or a polycyclic aromatic group, optionally substituted by at least one10group chosen from (C1-C6)-alkyl, halogen, -NRcRd, -ORd, hydrazine, -CF3 and -CN, Rcand Rd, identical or different, represent hydrogen or a linear or branched (C1-C50)-alkyl group, optionally interrupted by at least one atom or group chosen from -O-, -NR-, -S-, - C(=O)-, -O-C(=O)-, -C(=O)-O-, -NR-C(=O)-, -C(=O)-NR-, -NR-C(=O)-NR’-, -NR-C(=S)- NR’-, -NR-C(=O)-O-, -O-C(=O)-NR’-, -C(R)=C(R’)-, -C≡C-, arene diyl, in particular 15 benzene diyl, and heteroarene diyl, optionally substituted by at least one group comprising one or more heteroatoms chosen from O, N, P and / or S, in particular a group chosen from quaternary ammonium, sulphate, sulfonate, and phosphonate, Raand Rb, identical or different, represent: - a halogen, in particular -F or -Cl,20- a linear or branched (C1-C50)-alkyl group, optionally interrupted by at least one atom or group chosen from -O-, -NR-, -N+RR’-, -S-, -C(=O)-, -O-C(=O)-, -C(=O)-O-, - NR-C(=O)-, -C(=O)-NR-, -NR-C(=O)-NR’-, -NR-C(=S)-NR’-, -NR-C(=O)-O-, -O- C(=O)-NR’-, -C(R)=C(R’)-, -C≡C-, arene diyl, in particular benzene diyl, and heteroarene diyl, 25 - a group constituted by or comprising a linker L and at least one group V, V is chosen from: V is chosen from: - groups comprising one or more heteroatoms chosen from O, N, P and / or S, in particular a group chosen from quaternary ammonium, sulphate, sulfonate, and 30 phosphonate, - bioconjugable groups, in particular chosen from amine, ammonium, carboxylic acid, activated esters, in particular N-hydrosuccinimidyl, N-hydroxysulfosuccinimide, pentafluorophenyl, tetrafluorophenyl, squarate, in particular diethylsquarate, 20 maleimide, thiol, isothiocyanate, isocyanate, oxadiazolyl methyl sulfone, azoture or azide, optionally substituted tetrazine, triazole, alkyne, in particular terminal alkyne, trans-cyclooctene, cyclooctyne, in particular dibenzocyclooctyne and bicyclononyne, 5 - fluorescence quencher groups, for example diazo groups or diazo-containing groups, - a biological vector, in particular a cyclic or linear peptide, an antibody, an antibody fragment, a nanobody, an affibody, an aptamer, a short DNA or RNA sequence, a polysaccharide, a lipid, a sugar, an amino acid, a vitamin, a AMD3100 or AMD3100- type molecule, a prostate-specific membrane antigen (PSMA) ligand, a steroid, a 10 fatty acid, a polyamine, a polyphenol, a DNA base or a caffeine derivative, - a nanoparticle, in particular a nanoparticle of 10 kDa or less or lipidic nanoparticles, more particularly a gold nanocluster or a lipid nanoparticle, for example a lipidot, - a metal complex, in particular for therapeutic purposes, formed by a chelating agent and a metal, 15 - a radiometallic complex, formed by a chelating agent, for example DOTA (1,4,7,10- tetraazacyclododecane-1,4,7,10-tetraacetic acid), and a radiometal, in particular for therapeutic or diagnostic purposes, - a metal or radiometal chelating agent, for example DOTA, L is in particular a linear or branched (C1-C50)-alkyl group, optionally interrupted by at least20 one atom or group chosen from -O-, -NR-, -S-, -C(=O)-, -O-C(=O)-, -C(=O)-O-, -NR- C(=O)-, -C(=O)-NR-, -NR-C(=O)-NR’-, -NR-C(=S)-NR’-, -NR-C(=O)-O-, -O-C(=O)- NR’-, -C(R)=C(R’)-, -C≡C-, arene diyl, in particular benzene diyl, and heteroarene diyl, R and R’, identical or different, represent hydrogen or a linear or branched (C1-C6)-alkyl group, 25 or one of its tautomers. In a particular embodiment, said compound emits at a wavelength greater than or equal to 650 nm, in particular greater than or equal to 700 nm. In a particular embodiment, said use includes a step of measuring fluorescence variations linked to variations in physiological conditions chosen from pH, oxygen content, 30 presence of enzymes, polarity and viscosity of cell organelles. For example, said use includes a step of measuring fluorescence variations linked to variations in pH, said compound comprising, notably as Z, R1, R2, R3 or R4, a phenol group, in particular a o-Cl-phenol, a o-nitro-phenol, or a p-N(CH3)2-phenyl. 21 For example, said use includes a step of measuring fluorescence variations linked to the presence of enzymes, said compound comprising, notably as Z, R1, R2, R3 or R4, a phenol group, in particular a p-nitro-OCH3-phenyl. For example, said use includes a step of measuring fluorescence variations linked to 5 the presence of oxygen, said compound comprising, notably as Z, R1, R2, R3or R4, a phenol group, in particular a p-N(Et)2-phenyl. For example, said use includes a step of measuring fluorescence variations in viscosity of cell organelles, said compound comprising, notably as Z, R1, R2, R3or R4, a phenol group, in particular a (C1-C50)-alkyl-O-phenyl, in particular a p-(C1-C50)-alkyl-O- 10 phenyl. Said method of in vivo fluorescence-lifetime imaging may be used for fluorescence guided surgery (FGS). Said method of in vivo fluorescence-lifetime imaging or fluorescence guided surgery may concern a patient, which is notably a mammal, in particular chosen from a human, for 15 example a human child, a domestic livestock mammal, for example cattle (such as cows, beef, heifers and bulls), horses, donkeys, pigs, sheeps and goats, or a companion or research mammal, for example cats, horses, pigs, mice, rats, rabbits and ferrets, more particularly a dog or a mouse. In a preferred embodiment, the patient is a human. 20 Said patient may be afflicted with one or more diseases and / or conditions that are notably cancer, endometriosis, atherosclerosis, diabetes or wound healing. In vivo fluorescence-lifetime imaging is known from the skilled person in the art, as for example described by Peng, O. et al. (J. Fluorescence Lifetime Imaging of Cancer In Vivo. in In Vivo Fluorescence Imaging: Methods and Protocols (ed. Bai, M.) 55–66 25 (Springer, New York, NY, 2016) ; Smith, J. T. et al. (Optica 2022, 9 (5), pp. 532-544); or Kumar, A. T. et al. (Fluorescence lifetime-based contrast enhancement of indocyanine green-labeled tumors, JBO 22, 040501 (2017).All the embodiments defined above in relation with the compounds of formula (I) also apply here regarding compounds of formula (II), alone or in combinations. 30 In a particular embodiment, the compound of formula (II) is a compound of formula (I). In a particular embodiment, said compound is chosen from:

[0003] 27 DEFINITIONS The following terms and expressions contained herein are defined as follows: As used herein, a range of values in the form “x-y” or “x to y”, or “x through y”, 5 include integers x, y, and the integers there between. For example, the phrases “1-6”, or “1 to 6” or “1 through 6” are intended to include the integers 1, 2, 3, 4, 5, and 6. Preferred 28 embodiments include each individual integer in the range, as well as any subcombination of integers. For example, preferred integers for “1-6” can include 1, 2, 3, 4, 5, 6, 1-2, 1-3, 1-4, 1-5, 2-3, 2-4, 2-5, 2-6, etc. As used herein, the term “patient” or “subject” refers to a warm blooded animal 5 such as a mammal, notably a human, or a human child, which is in particular afflicted with, or has the potential to be afflicted with one or more diseases and conditions described herein. The mammal may also be domestic livestock mammal, or a companion or research mammal. 10 Domestic livestock mammals include cattle (cows, beef, heifers and bulls), horses, donkeys, pigs, sheeps and goats. Companion or research mammals include, without limitation thereto, dogs, cats, horses, pigs, mice, rats, rabbits and ferrets. Particularly contemplated companion or research mammals are a dog or a mouse. 15 By “diseases and conditions” are notably meant cancer, endometriosis, atherosclerosis, diabetes or wound healing. For the purpose of the invention, the term "pharmaceutically acceptable" is intended to mean what is useful to the preparation of a pharmaceutical composition, and what is generally safe and non-toxic, for a pharmaceutical use. 20 The term "pharmaceutically acceptable salt or solvate" is intended to mean, in the framework of the present invention, a salt or solvate of a compound which is pharmaceutically acceptable, as defined above, and which possesses the pharmacological activity of the corresponding compound. The pharmaceutically acceptable salts comprise: 25 (1) acid addition salts formed with inorganic acids such as hydrochloric, hydrobromic, sulfuric, nitric and phosphoric acid and the like; or formed with organic acids such as formic, acetic, benzenesulfonic, fumaric, glucoheptonic, gluconic, glutamic, glycolic, hydroxynaphthoic, 2-hydroxyethanesulfonic, lactic, maleic, malic, mandelic, methanesulfonic, muconic, 2-naphthalenesulfonic, propionic, succinic, dibenzoyl-L-tartaric, 30 tartaric, p-toluenesulfonic, trimethylacetic, and trifluoroacetic acid and the like, the salts being for example formates or trifluoroacetates, and (2) base addition salts formed when an acid proton present in the compound is either replaced by a metal ion, such as an alkali metal ion, an alkaline-earth metal ion, or an 29 aluminium ion; or coordinated with an organic or inorganic base. Acceptable organic bases comprise diethanolamine, ethanolamine, N-methylglucamine, triethanolamine, tromethamine and the like. Acceptable inorganic bases comprise aluminium hydroxide, calcium hydroxide, potassium hydroxide, sodium carbonate and sodium hydroxide. 5 Acceptable solvates for the therapeutic use of the compounds of the present invention include conventional solvates such as those formed during the last step of the preparation of the compounds of the invention due to the presence of solvents. As an example, mention may be made of solvates due to the presence of water (these solvates are also called hydrates) or ethanol. 10 It is also specified that all the formulae defined in the present specification include all the possible resonance structures, also called tautomers, being in particular noted that the structures represented herein may not be the most stable resonance structures. The term "alkyl", as used in the present invention, refers in particular to a straight or branched saturated hydrocarbon chain, or a saturated or partially saturated mono- or bicyclic 15 alkyl ring system. Unless stated otherwise, the term "alkyl" thus includes the term "cycloalkyl”, which refers in particular to a saturated or partially saturated mono- or bicyclic alkyl ring system. The term "(C1-CX)alkyl", as used in the present invention, refers in particular to a straight or branched saturated hydrocarbon chain containing from 1 to X carbon atoms.20For instance, the term "(C1-C7)alkyl", includes, but is not limited to, methyl, ethyl, n-propyl, iso-propyl, n-butyl, iso-butyl, sec-butyl, t-butyl, n-pentyl, n-hexyl, n-heptyl and the like, or a (C3-C7)cycloalkyl, such as cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, cyclooctyl, pinenyl, adamantanyl and the like. The term "alcoxy" as used in the present invention, refers in particular to alkyl-O- 25 group, wherein the term "alkyl" is as defined above. As used herein, the term "aryl" refers to a substituted or unsubstituted, mono- or bicyclic hydrocarbon aromatic ring system having 6 to 10 ring carbon atoms. Examples include phenyl and naphthyl. Preferred aryl groups include unsubstituted or substituted phenyl and naphthyl groups. Included within the definition of "aryl" are fused ring systems, 30 including, for example, ring systems in which an aromatic ring is fused to a cycloalkyl ring. Examples of such fused ring systems include, for example, indane, indene, and tetrahydronaphthalene. 30 The term "halogen", as used in the present invention, refers in particular to a bromine, chlorine or iodine atom. The term "alkenyl" refers in particular to any straight or branched hydrocarbon chain, carrying at least one carbon-carbon double bond, of 2 to 12 carbon atoms, preferably 2 to 6 5 carbon atoms, such as for example ethenyl, 2-propenyl, 2-butenyl, 3-butenyl, 2-pentenyl and its isomers, 2-hexenyl and its isomers, 2,4-pentadienyl. The term "alkynyl" refers in particular to any linear or branched hydrocarbon chain, carrying at least one carbon-carbon triple bond, of 2 to 12 carbon atoms, preferably of 2 to 6 carbon atoms, such as for example ethynyl, 2-propynyl, 2-butynyl, 3-butynyl, 2-pentynyl 10 and its isomers, 2-hexynyl and its isomers. By “optionally interrupted”, is in particular meant that the alkyl group comprises a given group, instead of a C-C bond, or in terminal position. DRAWINGS 15 Figure 1 illustrates, according to example 4, representative in vivo reflectance, fluorescence intensity and FLT images of mice bearing a EGFR+ subcutaneous tumor (right lateral view) acquired at 6, 24 and 48h after intravenous administration of cetux-rd or cetux- ss. On the reflectance images, ROIs drawn around the tumor (T), the tumor margin (TM) and the shoulder (S) (background normal tissue) are indicated. 20 EXAMPLES Example 1: synthesis of compounds according to the invention RP-HPLC separations System A: semi-preparative RP-HPLC (SiliCycle SiliaChrom C18 column, 10 μm, 20×250 25 mm) with MeCN and aq.0.1% TFA (pH 1.9) as eluents [10% MeCN (5 min), followed by a linear gradient from 10% to 100% MeCN (70 min)] at a flow rate of 20.0 mL / min. Quadruple UV-visible detection was achieved at 220, 260, 340 and 690 nm. System B: semipreparative RP-HPLC (SiliCycle SiliaChrom C18 column, 10 μm, 20×250 mm) with MeCN and aq. 0.1% formic acid (FA, pH 2.1) as eluents [0% MeCN (5 min), 30 followed by a linear gradient from 0% to 100% MeCN (70 min)] at a flow rate of 20.0 mL / min. Quadruple UV-visible detection was achieved at 220, 275, 640 and 670 nm. System C: semipreparative RP-HPLC (Shimadzu Shimpack GIS C18 column, 5 μm, 10×250 mm) with MeCN and aq. 0.1% TFA (pH 1.9) as eluents [10% MeCN (3 min), 31 followed by a linear gradient from 10% to 30% MeCN (4 min), followe by a linear gradient from 30% to 100% MeCN (40 min)] at a flow rate of 5.0 mL / min. Quadruple UV-visible detection was achieved at 220, 260, 340 and 690 nm. System D: semi-preparative RP-HPLC (SiliCycle SiliaChrom C18 column, 10 μm, 20×250 5 mm) with MeCN and aq.0.1% TFA (pH 1.9) as eluents [10% MeCN (5 min), followed by a linear gradient from 10% to 100% MeCN (70 min)] at a flow rate of 20.0 mL / min. Quadruple UV-visible detection was achieved at 220, 275, 640 and 670 nm. System E: semipreparative RP-HPLC (Shimadzu Shimpack GIS C18 column, 5 μm, 10×250 mm) with MeCN and aq.0.1% TFA (pH 1.9) as eluents [10% MeCN (3 min), followed by 10 a linear gradient from 10% to 30% MeCN (4 min), followed by a linear gradient from 30% to 100% MeCN (40 min)] at a flow rate of 5.0 mL / min. Quadruple UV-visible detection was achieved at 220, 275, 640 and 670 nm. Synthesis of Aza-1: 15 Aza-BOD-Th was synthesized according to a literature procedure (Tetrahedron, 2011; 67, 7148-7155). In Schlenk tube fetched with a magnetic stirring bar, N,N-dimethylpropargylamine (160 ^L, 0.148 mmol) was dissolved in dry THF (17 mL) and the solution was bubbled with argon gas for 5 minutes. A solution of ethylmagnesium bromide (1.81 mL, 0.9 M in THF, 1.63 20 mmol) was then added and the resulting reaction mixture was heated to reflux for 45 minutes. In a second Schlenk tube, Aza-BOD-Th (379 mg, 0.74 mmol) was dissolved in dry THF (17 mL). The mixture of the first Schlenk tube was transferred through a cannula to the second Schlenk tube. The final mixture was then refluxed for 45 minutes and the reaction was monitored by TLC, showing the complete consumption of the starting compound. The 25 reaction was cooled and quenched by adding EtOH (3 mL). Thereafter, solvents were evaporated under reduced pressure and the resulting residue was purified by column chromatography (SiO2, eluent = a step gradient of MeOH in DCM from 0% to 10%) to afford Aza-1 as glittery dark red-green powder (470 mg, yield 85%). 32 1H NMR (500 MHz, CDCl3): δ (ppm) = 8.83 (d, J = 3.8 Hz, 2H), 8.05 (d, J = 7.1 Hz, 4H), 7.61(d, 2H, J = 5.2 Hz), 7.47-7.41 (multiplet, 6H), 7.27 (overlapping with residual signal of non-deuterated CHCl3, d, 2H), 7.22 (s, 2H), 3.20 (s, 4H), 2.15 (s, 12H). HRMS (ESI) (Da): m / z calcd.318.6247 for [M + 2H]2+, found 318.62460. 5 Synthesis of Waza-1 and Waza-2: Waza-1: In a round bottom flask fetched with a magnetic stirring bar, Aza-1 (30 mg, 0.047 mmol) was dissolved in DCM (2 mL) followed by the addition of methyl iodide (MeI, 1 mL, 16 10 mmol, 340 equiv.). The resulting reaction mixture was stirred at room temperature for 30 minutes. Then, volatiles (DCM and MeI) were evaporated under reduced pressure. Waza-1 was obtained in a quantitative yield (43 mg). 1H NMR (500 MHz, CD3OD): δ (ppm) = 8.67 (d, J = 3.8 Hz, 2H), 8.12 (d, J = 7.1 Hz, 4H), 8.00 (d, J = 5.2 Hz, 2H), 7.57 (s, 2H), 7.52-7.44 (m, 6H), 7.45 (t, J = 4.6 Hz, 2H), 4.17 (s, 15 4H), 2.94 (s, 18H). HRMS (ESI) (Da): m / z calcd.332.64036 for [M-2I]2+, found 332.64032. Waza-2: In a round bottom flask fetched with a magnetic stirring bar, Aza-1 (30 mg, 0.047 mmol) was dissolved in MeCN (2 mL) followed by the addition of 1,3-propanesultone (12 mg, 0.1 20 mmol, 21 equiv.) and anhydrous K2CO3 (25 mg, 0.19 mmol, 4 equiv.). The resulting reaction mixture was stirred at 50 °C for 4 hours. The reaction was monitored by LC-MS showing the formation of Waza-2 as the major product. Thereafter, the mixture was filtered to remove inorganic salts, and directly purified by semi-preparative RP-HPLC (System A, Rt= 33 – 35 mins). The product containing fractions were lyophilized to give TFA salt of Waza-2 as a 25 dark green amorphous powder (18 mg, yield 40% based on TFA mass = 20% determined by ion chromatography). 33 1H NMR (500 MHz, CD3OD): δ (ppm) = 8.71 (d, J = 3.8 Hz, 2H), 8.11 (d, J = 7.2 Hz, 4H), 8.01 (d, J = 5.1 Hz, 2H), 7.56 (s, 2H), 7.52-7.46 (m, 8H), 4.10 (s, 4H), 3.43 (m, 4H), 2.91(s, 12H), 2.78 (t, J = 6.2 Hz, 4H), 2.11 (m). HRMS (ESI) (Da): m / z calcd.462.61042 for [M + 2Na]2+, found 462.60993 5 Waza-BC1: H Steps 1 (N-alkylation) and 2 (Boc removal): In a round bottom flask fetched with a magnetic stirring bar, Aza-1 (100 mg, 0.15 mmol) was dissolved in MeCN (10 mL) followed by the addition of N-Boc-PEG4-bromide 10 (purchased from BroadPharm company, 190 mg, 0.47 mmol, 3.1 equiv.) and NaHCO3 (66 mg, 0.78 mmol, 5.2 equiv.). The reaction mixture was heated under refluxed overnight. The reaction was monitored by LC-MS showing the complete consumption of starting Aza-1 and formation of the bis-PEGylated product. Then, the crude mixture was filtered to remove inorganic salts and concentrated under reduced pressure. The resulting residue was dissolved 15 in MeCN (3 mL) and aq. 1.0 M HCl was added (1 mL, 6.7 equiv.). The mixture was left under stirring at room temperature overnight. LC-MS analysis showed the formation of the mono-deprotected derivative as the major product with the full-deprotected product as the side product. The mono N-Boc derivative was purified by semi-preparative RP-HPLC (System A, Rt = 33 – 35 mins). The product containing fractions were lyophilized to give 20 TFA salt of mono-amine intermediate which was used directly in the next step (80 mg, yield 44%). 34 Steps 3 (N-acylation with DOTA-tris(tBu) ester NHS ester followed by Boc removal) and 4 (introduction of reactive handle for bioconjugation): TFA salt of mono-amine (40 mg, 0.041 mmol) was dissolved in dry DMF (2 mL) followed by the addition of DOTA-tris(tBu) ester NHS ester (provided by CheMatech company, 42 5 mg, 0.051 mmol, 1.2 equiv.) and triethylamine (TEA, 24 ^L, 0.17 mmol, 5 equiv.). The resulting reaction mixture was stirred at 40 °C for 1 hour to reach completion (confirmed by LC-MS analyses). Thereafter, volatiles were evaporated under reduced pressure. The crude residue was redissolved in MeCN (2 mL) and aq.4.0 M HCl (1 mL, 117 equiv.) was added. The reaction mixture was stirred at 40 °C for 48 hours. LC-MS analysis showed the only 10 formation of Waza-BC1. This later one was purified by semi-preparative RP-HPLC (System A, Rt = 25 – 27 mins). The product containing fractions were lyophilized to give TFA salt of Waza-BC1 as a dark blue spongy solid (32 mg, yield 34% based on TFA mass = 38% determined by ion chromatography). 1H NMR (500 MHz, CD3OD): δ (ppm) 8.66 = (d, J = 3.9 Hz, 2H), 8.14 (d, J = 7.1 Hz, 4H), 15 8.02 (d, J = 5.2 Hz, 2H), 7.62 (s, 2H), 7.54-7.48 (m, 6H), 7.43 (t, J = 4.7 Hz, 2H), 4.22 (s, 2H), 4.21(s, 2H), 3.81(broad peak, 5H), 3.73 (broad peak, 5H), 3.59 (t, J = 4.7 Hz, 3H), 3.53-3.33 (m, 40H), 3.25 (2 broad peaks, 8H), 3.04 (t, 3H, Jc= 4.6 Hz), 2.95 (broad singlet, 12H). HRMS (ESI) (Da): m / z calcd.487.57699 for [M-3TFA]3+, found 487.55702. 20 Waza-BC1-Sq:

[0004] 35 O CFCF3H In a round bottom flask fetched with a magnetic stirring bar, Waza-BC1 (15.4 mg, 10 ^mol) was dissolved in absolute EtOH (2 mL) followed by the addition of diethyl squarate (17.86 ^L, 91 ^mol, 9.1 equiv.) and N,N-diisopropylethylamine (DIPEA, 17.85 ^L, 105 ^mol, 10.5 5 equiv.). The reaction mixture was stirred at 35 °C for 1 hour. LC-MS analysis showed the complete consumption of the starting amine and the only formation of the desired product. Volatiles were then evaporated under reduced pressure. The resulting residue was purified by semi-preparative RP-HPLC (System C, Rt= 17 – 19 mins), The product containing fractions were lyophilized to give TFA salt of Waza-BC1-Sq as a dark blue sponge (10 mg, 10 yield 62%, calculated without counting TFA counterions). HRMS (ESI) (Da): m / z calcd.528.91567 for [M+H-2TFA]3+, found 528.91553. Synthesis of waza-3, waza-4, waza-5, and waza-pH-1 Aza-OMe was prepared according to a literature procedure. (Bioconjugate Chem.2019; 30, 1061-1066). 15 37 Aza-OH: In a round bottom flask fetched with a magnetic stirring bar, Aza-OMe (0.5 g, 0.7 mmol) was dissolved in dry DCM (100 mL) followed by the slow addition of a solution of boron tribromide (3.65 mL, 3.65 mmol, 1.0 M in DCM). The reaction mixture was stirred at room 5 temperature overnight. A further amount of boron tribromide solution in dichloromethane (3.65 mL) was added to reach reaction completion (monitored by LC-MS analyses). Thereafter, the reaction mixture was quenched by adding methanol (5 mL) and stirring for 30 minutes. Solvents were then evaporated under reduced pressure. The resulting residue was purified by column chromatography (SiO2, eluent = DCM / MeOH 90:10, v / v) to afford 10 Aza-OH as a dark blue glittery powder (220 mg, yield 45%). 1H NMR (500 MHz, CD3OD) δ (ppm): 8.29 (d,3J = 8.7 Hz, 4H), 8.11 (d,3J = 8.1 Hz, 4H), 7.50-7.44 (m, 6H), 7.31 (s, 2H), 6.98 (d, 4H,3J = 8.7 Hz), 3.75 (s, 4H), 2.58 (s, 12H). HRMS (ESI) (Da): m / z calcd.326.66320 for [M + 2H]2+, found 326.66315. Waza-3 15 In a round bottom flask fetched with a magnetic stirring bar, Aza-OH (83 mg, 0.126 mmol) was dissolved in MeCN (10 mL) followed by the addition of MeI (5 mL) and NaHCO3 (160 mg, 1.9 mmol, 15 equiv.). The reaction mixture was stirred for at room temperature overnight. LC-MS analysis showed the complete consumption of starting Aza-OH and the complete formation of waza-3. The mixture was then filtrated to remove inorganic salts and 20 evaporated under reduced pressure. The resulting residue was purified by semi-preparative RP-HPLC (System D, Rt= 23 – 27 mins) to afford TFA salt of wasa-3(95 mg, 82% yield, calculated assuming each waza-3 contains 2 TFA counterions). 1H NMR (500 MHz, CD3OD): δ (ppm) = 8.29 (d,3J = 8.8 Hz, 4H), 8.11 (d,3J = 8.1 Hz, 4H), 7.49-7.41 (m, 6H), 7.34 (s, 2H), 6.92 (d,3J = 8.8 Hz, 4H), 4.01 (s, 4H), 2.89 (s, 18H). 25 HRMS (ESI) (Da): m / z calcd.342.67885 for [M-2TFA]2+, found 342.67871. Aza-3: In a round bottom flask fetched with a magnetic stirring bar, wasa-3 (95 mg, 0.1 mmol) was dissolved in MeCN (10 mL) followed by the addition of anhydrous K2CO3(138.2 mg, 1 mmol, 10 equiv.). The reaction mixture was stirred 5 minutes before adding tert-butyl 30 bromoacetate (8 ^L, 0.052 mmol, 0.5 equiv.). The reaction was left stirring at 40 °C overnight. LC-MS analysis showed the formation of the desired mono-O-alkylated product as the major product. Then, the mixture was filtered to remove inorganic salts and concentrated under reduced pressure. The resulting residue was purified by semi-preparative 38 RP-HPLC (System D, Rf= 32-37 mins, System B, Rt= 27 – 30 mins) to give TFA salt of waza-4 as a dark green solid (45 mg, yield 48%, based on HCOOH mass = 6.25 % determined by ion chromatography). Please note: the minor product was the starting bis- phenolic compound which was recovered during the RP-HPLC purification step to be reused 5 for further synthesis of waza-4. Only product purified RP-HPLC (System B) works in the next step. 1H NMR (500 MHz, DMSO-d6): δ (ppm) = 8.34 (d,3J = 8.8 Hz, 2H), 8.30 (d,3J = 8.8 Hz, 2H), 8.15 (t,3J = 6.5 Hz, 4H), 7.65 (s, 2H), 7.56-7.45 (m, 6H), 7.13 (d,3J = 8.8 Hz, 2H), 6.99 (d,3J = 8.8 Hz, 2H), 4.83 (s, 2H), 4.03 (s, 4H), 2.80 (s, 18H), 1.48 (s, 9H).10HRMS (ESI) (Da): m / z calcd.399.71289 for [M-2HCOOH]2+, found 399.71275. Waza-5: In a round bottom flask fetched with magnetic stirring bar, Waza-4 (45 mg, 0.043 mmol) was dissolved in MeCN (4 mL) and the resulting solution heated at 85 °C. In parallel, KNO3 (4.85 mg, 0.048 mmol, 1.1 equiv.) and KHSO4(8.85 mg, 0.043 mmol, 1 equiv.) was 15 dissolved in ultrapure water (0.4 mL) and added slowly to the warm mixture. After 10 minutes, the solution turned blue. The reaction was immediately quenched by cooling it down to room temperature. LC-MS analysis showed the formation of the desired ortho-nitro product with some impurities. The reaction mixture was directly purified by semi- preparative RP-HPLC (System D, Rt = 27 – 30 mins) to give TFA salt of Waza-5 as a dark 20 green solid (15 mg, yield 32%, based on TFA mass = 20 % determined by ion chromatography). 1H NMR (500 MHz, DMSO-d6): δ (ppm) = 9.15 (d,4J = 2.2 Hz, 1H), 8.44 (d,3J = 9.0 Hz, 2H), 8.35 (dd,3J = 9.0 Hz,4J = 2.3 Hz, 1H), 8.17 (d,3J = 7.01 Hz, 2H), 8.14 (d,3J = 7.01 Hz, 2H), 7.71 (s, 1H), 7.67 (s, 1H), 7.56-7.47 (m, 6H), 7.27 (d,3J = 9.0 Hz, 1H), 7.18 (d,3J 25 = 9.0 Hz, 2H), 4.87 (s, 2H), 4.04 (s, 4H), 2.82 (s, 18H), 1.48 (s, 9H). HRMS (ESI) (Da): m / z calcd.422.20543 for [M-2TFA]2+, found 422.20634. Waza-pH-1: Step 1 In a round bottom flask fetched with a magnetic stirring bar, wasa-5 (15 mg, 0.014 mmol) 30 was dissolved in MeCN (3 mL) followed by the addition of TFA (0.2 mL). The reaction mixture was stirred at 40 °C until complete deprotection of Wasa5(complete tert-butyl ester removal checked by LC-MS analyses). Thereafter, the reaction mixture was co-evaporated 39 several times with DCM to completely remove traces of TFA. The resulting free carboxylic acid derivative was used in the next step without further purification. Step 2 This compound was then dissolved in dry DMF followed by the addition of (12 mg, 0.088 5 mmol, 6.2 equiv.), HBTU (33 mg, 0.088 mmol, 6.2 equiv.), and DIPEA (14.8 ^L, 0.088 mmol, 6.2 equiv.) and left stirring for 30 minutes. Then, Boc-TOTA (28 mg, 0.088 mmol, 6.2 equiv., purchased from Iris Biotech GmbH) was added and the mixture was stirred at room temperature for 1 hour. The reaction was checked for completion by LC-MS and the mixture was concentrated under reduced pressure. The coupling product was used in the next 10 step without further purification. Step 3 This N-Boc derivative was dissolved in MeCN (1 mL) and aq.1.0 M HCl (1 mL) was added. The reaction mixture was stirred at room temperature overnight. The reaction was checked for completion by LC-MS anlaysis. The reaction mixture was directly purified by semi- 15 preparative RP-HPLC (System E, Rt= 14 – 16 mins) to give TFA salt of Aza-4 as a dark green solid (10 mg, yield 63% based on TFA mass = 16.57 % determined by ion chromatography). 1H NMR (500 MHz, CD3OD): δ (ppm) = 9.35 (d,4J = 2.2 Hz, 1H), 8.44 (d,3J = 9.0 Hz, 2H), 8.28 (dd,2J = 9.0 Hz,3J = 2.3 Hz, 1H), 8.13 (multiplet, 2H), 7.53-7.47 (multiplet + 20 singlet, 7H), 7.38 (s, 1H), 7.33 (d,3J = 9.0 Hz, 1H), 7.22 (d,3J = 9.0 Hz 2H), 4.72 (s, 2H), 4.04 (s, 4H), 3.67-3.60 (multiplet, 10H), 3.55 (t,3J = 6.6 Hz, 2H), 3.38 (t,3J = 6.6 Hz, 2H), 3.09 (t,3J = 6.6 Hz, 2H) , 2.91 (s, 18H), 1.92 (multiplet, 2H), 1.84 (multiplet, 2H). HRMS (ESI) (Da): m / z calcd.330.50789 for [M-3TFA]3+, found 330.50796. 25 The following compound has been obtained in a analogous way to compound Aza-1: . 40 Example 2: Photophysical studies Photophysical studies of synthesized compounds, details are summarized in the table below. Stock solution of each compound (final concentration 1 mg / mL) was prepared in DMSO (UV spectroscopy grade). Lifetime M ) D P (1 p 15 p P (5 P (5 5 pKa Determination of Waza-4, Waza-5 Aza-pH-1 and lifetime measurements: pKa was determined using UV-Vis absorption measurements. The stock solution of each compound (final concentration = 1 mg / mL) was prepared in DMSO (UV spectroscopy grade), then diluted in the needed buffer solution (final concentration = 5 ^M). Visible 10 absorption spectrum (300-900 nm) of each solution was recorded at 25 °C. Variation of pH was done using different aq. buffer solutions (pH = 2, 0.1% TFA in ultrapure water; pH = 3.48 to pH = 5.68, aq.0.1 M acetate buffer; pH = 5.9 to pH = 8.12, aq.0.66 mM phosphate buffer; pH = 8.63 to 9.7, aq.0.2 M borate buffer). In the three different cases ; i.e. for Waza- 4, Waza-5, and Aza-pH-1, upon basification of the solution the absorption band at 650 nm 15 vanishes and a new band centered at 700 nm appears. The absorbance at 700 nm was noted 41 and plotted versus the buffer pH value. Curve fitting was achieved with OriginPro 8 software (fit sigmoidal, Boltzmann function) that also provided the inflection point whose x- coordinate corresponds to the pKa of phenol. FLT was measured for the different compounds at different pH in order to show the influence 5 of protonation / deprotonation state on this photophysical parameter. Lifetime M ) D (f D S v / p FLT of Waza-4, Waza-5, and Waza-pH-1 in aq. buffers at different pH. p nm) 10 Example 3: Bioconjugation on whole antibodies 42 Deglycosylation of antibodies: Antibody (2 mg / mL) in PBS pH 7.4 was incubated with 500 U / mg (one unit is defined as the amount of enzyme required to remove > 95% of the carbohydrate from 10 µg of denatured RNase B in 1 hour at 37°C in a total reaction volume of 10 µL) of protein of N-glycosidase F (PNGase F from NEB, New England Biolabs) 5 overnight at 37 °C. The enzyme was then removed and the deglycosylated antibody was concentrated by centrifugation (Amicon Ultra-2 Centrifugal Filter Unit MWCO 50 kDa from Merck, three cycles of centrifugation at 4000 rpm for 15 min). The reaction was checked by LC-MS. Recovery yield: 90%. Site-specific conjugation: deglycosylated antibody (4 mg / mL) in PBS was incubated with 10 20 equivalents of Waza-BC1 (30 mM in DMSO) and with 3 U / mg of antibody of microbial transglutaminase (MTGase from Zedira). The resulting solution was stirred overnight (16 h) in a thermomixer (900 rpm) at 37 °C. The reaction was checked by LC-MS. Excess of probes and MTGase were removed by FPLC purification. The degree of labeling (DOL) was calculated based on LC-MS analysis. 15 Random conjugation: bioconjugation was optimized to get a degree of labeling (DOL) around two for comparison purpose with site specific method. On this account, 7 equivalents of Waza-BC1-Sq at 15 mM (DMSO) was added to a solution of native antibody (2 mg / mL ) in 0.2 M bicarbonate buffer pH 9.2.The reaction mixture was then stirred in a thermomixer (900 rpm) for 6 h at 37 °C. The free probe was removed by FPLC. The degree of labeling 20 (DOL) was calculated based on MALDI-TOF analysis. Fast protein liquid chromatography (FPLC) purification: FPLC purification of the conjugates was performed on an ÄKTA™25 M system (GE Healthcare Life Sciences) with a Hitrap Mabselect™ column (MabSelect resin, Protein A, cross-linked agarose, column I.D. 7 mm, bed dimensions 7 x 25 mm, bed volume 1 mL). After deposition of the product, the 25 conjugate was washed with 5 CV of PBS pH 7.4 (1 mL / min) followed by 5 CV of PBS 0.1 %Tween20 (1 mL / min) and 5 CV of PBS pH 7.4 (1 mL / min). The conjugate was then eluted with 25 mM acetic acid (1 mL / min) and collected. Purification was monitored at 280 and 700 nm. Thereafter, the solution was transferred to an ultra-centrifugal filter device (Amicon Ultra 2 mL, Ultracel cut-off 50 kDa from Merck Millipore) and centrifuged at 4000 rpm for 30 3x15 min in order to condition the mixture in PBS (pH 7.4). Purification monitoring was performed using UNICORN™ 7.2 interface software (GE Healthcare). 43 The recovered yield and masses of antibody engaged in each reaction are listed in the table bellowed with the corresponding DOL determined thanks to LC-ESI-MS analysis (for site- specific conjugation) or MALDI-TOF analysis (for random conjugation) after purification. LC-ESI-MS: Site-specific bioconjugation reactions were followed by reverse phase HPLC 5 (Vanquish, Thermo Fisher Scientific) coupled to a high-resolution Orbitrap mass spectrometer (Exploris 240, Thermo Fisher Scientific) using an ESI source (positive mode). MALDI-TOF mass spectrometry: Analysis of random conjugates were performed by matrix- assisted laser desorption ionization mass spectrometry on a MALDI-ToF Microflex LRF instrument (Bruker). Samples were prepared with a saturated matrix of sinapinic acid: 3,5- 10 dimethoxy-4-hydroxycinnamic acid (Sigma Aldrich), in a 4 / 6 water / acetonitrile mixture (H2O + 0.1% TFA / CH₃CN + 0.1% TFA). ). Degree of labeling (DOL) ratios were determined by comparison of native and conjugated antibody masses, using mMass 5.5.0 software. For more accurate DOL calculation (neglecting local signal variations) a Gaussian smoothing was applied (5 cycles, size 800 m / z). B T T C C 15 Results of the bioconjugation reactions Example 4: In vivo studies All in vivo experiments were performed according to the EU Directive 2010 / 63 / EU and Belgian legislation and were approved by the Ethical Commission for Animal 20 Experimentation of the Vrije Universiteit Brussel, Belgium (project nr.23-272-15). Female Crl:NU-Foxn1nu mice (Charles River, UK) were housed in individually ventilated cages (n= 3 mice / cage) and received standard diet, and water, ad libitum (SAFE® 105, Safe Diet, Augy, France). Mice were inoculated with FaDu cells (2.5*106cells in 150 µL PBS; purchased from ATCC) above the right hind leg and imaged when the FaDu tumors had reached a size 25 of approximately 500 mm3. FLT imaging was conducted with the VUB tauCAM, a 44 macroscopic FLT imaging system with a 128x128-pixel custom fast time-gated CMOS image sensor. The tauCAM was synchronized to a pulsed supercontinuum laser (Rock 500- 6, Leukos, Limoges, France) with custom optical filter setup providing 240 mW of illumination power through an excitation filter centered around 670 nm (ET670 / 50m, 5 Chroma Technology Corp., Vermont, US). On the day of the experiment, the instrument response function of the tauCAM was determined by measuring reflected excitation light with a neutral density filter (Thorlabs, Newton, NJ, USA) and an exposure time of 5 ms. Thereafter, the neutral density filter was replaced by an emission filter centered around 740 nm (ET740 / 40m, Chroma Technology Corp., Vermont, US) to block excitation light and 10 capture the fluorescent emission of the bioconjugates. Mice were imaged under isoflurane anaesthesia (5% for induction, 2% for maintenance and 1.5 L / min oxygen flow rate) prior to injection of the tracer to evaluate autofluorescence. Thereafter, mice were intravenously injected via the lateral tail vein with either cetux-ss (n=3) or cetux-rd (n=3) (100 µg in 200 µL). FLT imaging was conducted at 6, 24, 48 hours post-injection (p.i.), with an 15 acquisition time of 500 ms in left lateral decubitus. Before analyzing the images in ImageJ, curve fitting of the fluorescent decay was performed using custom-built software, with the IRF implemented in the curve fitting model, and the FLTs per pixel were extracted. Thereafter, the fluorescence intensity (FI) and FLT images were further processed in ImageJ. FI values are represented in arbitrary units, whereas FLT values are represented in the 20 picosecond-nanosecond range. ROIs were drawn for the tumors, surrounding tumor margins and at the level of the shoulders based on reflectance images, and average FLT values for the ROIs were calculated. In addition, histograms depicting the normalized pixel counts within each ROI in function of the measured FLT values were generated to visualize the FLT distribution in the drawn ROIs. 25 Example 5: other compounds according to the invention Synthesis of Waza-6, Waza-pH-2 and Waza-always-on: 45 Waza-pH-2: Step 1 TFA (0.6 mL) was added to a solution of Waza-4 (20 mg, 0.019 mmol) in MeCN (5 ml) and 5 the solution was stirred at 40°C for two days. The solvent was removed under vacuo and the residual TFA was removed with serial additions of MeCN and subsequent removal under reduce pressure. The crude product was directly engaged in the next reaction without further purification or characterization. Step 2 10 This previous product was next dissolved in dry DMF (3 mL) followed by the addition of HOBt (13 mg, 0.096 mmol, 5 equiv.), HBTU (36 mg, 0.096 mmol, 5 equiv.), and DIPEA (17 µL, 0.096 mmol, 5 equiv.) and the solution was stirred for 30 minutes at RT. Then, Boc- TOTA (31 mg, 0.096 mmol, 5 equiv., purchased from Iris Biotech GmbH) was added and the mixture was further stirred at RT for 30 minutes. After completion, the mixture was 15 concentrated under reduced pressure to obtain the crude intermediate. Step 3 The crude product was dissolved in MeCN (1 mL) and aq. HCl 1.0 M (1 mL) was added. The resulting solution was stirred at RT overnight. The complete deprotection of the amine 46 was checked by RP-HPLC-MS analysis. The reaction mixture was directly purified by semi- preparative RP-HPLC (System A) and lyophilized to obtain Waza-pH-2 as a dark green powder (15 mg, 61% yield over two steps). 1H NMR (500 MHz, 298 K, CD3OD) δ (ppm): 8.36 – 8.26 (m, 4H), 8.16 – 8.09 (m, 4H), 5 7.54 – 7.46 (m, 6H), 7.41 (s, 1H), 7.28 (s, 1H), 7.17 (d,3J = 8.9 Hz, 2H), 7.00 (d,3J = 8.9 Hz, 2H), 4.69 (s, 4H), 4.01 (s, 2H), 3.67 – 3.60 (m, 10H), 3.55 (t,3J = 6.6 Hz, 2H), 3.42 – 3.35 (m, 2H), 3.08 (t,3J = 6.6 Hz, 2H), 2.89 (s, 18H), 1.92 (p,3J = 6.6 Hz, 2H), 1.84 (m,3J = 6.6 Hz, 2H). HRMS (ESI+): m / z calcd.315.51286 for [M+3H]3+, found 315.51280. 10 Synthesis of Waza-6 Waza-4 (0.8 g, 0.08 mmol, 1 eq.) was dissolved in MeCN (3 mL). MeI (1 mL, 16.3 mmol, 210 equiv.) was added in large excess and the reaction stirred at 40°C overnight. The solvents were evaporated under reduce pressure and the crude product was purified by semi- preparative RP-HPLC (System C) and lyophilized to obtain pure Waza-6 as a dark green 15 powder (67 mg, 83% yield). 1H NMR (500 MHz, 298 K, CD3OD): δ (ppm) 8.35 (d,3J = 9.0 Hz, 2H), 8.29 (d,3J = 9.0 Hz, 2H), 8.15 – 8.10 (m, 4H), 7.53 – 7.45 (m, 6H), 7.37 (s, 1H), 7.32 (s, 1H), 7.15 (d,3J = 9.0 Hz, 2H), 7.10 (d,3J = 9.0 Hz, 2H), 4.79 (s, 2H), 3.99 (s, 4H), 3.93 (s, 3H), 2.89 (s, 18H), 1.54 (s, 9H).20HRMS (ESI+): m / z calcd.406.72072 Th for [M+2H]2+, found 406.72064. Synthesis of Waza-always-on Step 1 TFA (0.3 mL) was added to a solution of compound Waza-6 (30 mg, 0.029 mmol) in MeCN (3 mL) and the solution was stirred at 40°C for two days. The solvent was removed under 25 vacuo and the residual TFA was removed with serial additions of MeCN and subsequent removal under reduce pressure. The crude product was directly engaged in the next reaction without further purification or characterization. Step 2 The previous product was next dissolved in dry DMF (5 mL) followed by the addition of 30 HOBt (19 mg, 0.144 mmol, 5 equiv.), HBTU (54 mg, 0.144 mmol, 5 equiv.), and DIPEA (25 µL, 0.144 mmol, 5 equiv.) and the solution was stirred for one hour at RT. Then, Boc- TOTA (46 mg, 0.096 mmol, 5 equiv., purchased from Iris Biotech GmbH) was added and 47 the mixture was further stirred at 40°C for one hour. After completion, the mixture was concentrated under reduced pressure. Step 3 The crude product was dissolved in MeCN (3 mL) and aq. HCl 1.0 M (2 mL) was added. 5 The solution was stirred at 40°C for two hours. The complete deprotection of the amine was checked by RP-HPLC-MS analysis. The reaction mixture was directly purified by semi- preparative RP-HPLC (System A) and lyophilized to obtain pure Waza-always-on as a dark green powder (25 mg, 67% yield over three steps). 1H NMR (500 MHz, 298 K, CD3OD) δ (ppm): 8.40 (d,3J = 9.0 Hz, 2H), 8.34 (d,3J = 9.0 10 Hz, 2H), 8.15 – 8.11 (m, 4H), 7.52 – 7.45 (m, 6H), 7.40 (s, 1H), 7.33 (s, 1H), 7.20 – 7.15 (m, 4H), 4.69 (s, 2H), 4.00 (s, 4H), 3.93 (s, 3H), 3.68 – 3.60 (m, 10H), 3.55 (t,3J = 6.2 Hz, 2H), 3.41 – 3.36 (m, 2H), 3.09 (t,3J = 6.2 Hz, 2H), 2.89 (s, 18H), 1.95 – 1.90 (m, 2H), 1.84 (p,3J = 6.2 Hz, 2H). HRMS (ESI+): m / z calcd.320.52069 for [M+3H]3+, found 320.51965. 15 Synthesis of Waza-7 and Waza-pO-1 S ynthesis of Waza-7: Waza-4 (105 mg, 0.10 mmol) was dissolved in MeCN (10 mL) followed by the addition of 4-nitro benzyl bromide (24 mg, 0.11 mmol, 1.1 equiv.) and K2CO3 (140 mg, 1.02 mmol, 10 20 equiv.). The reaction mixture was heated at 50°C for one hour. Then, the crude mixture was filtered to remove inorganic salts and concentrated under reduced pressure. The resulting residue was purified by semi-preparative RP-HPLC (System A). The product containing fractions were lyophilized to give TFA salt of Waza-7 (35 mg, yield 37%). 1H NMR (500 MHz, CD3OD): δ (ppm) 8.35 (d,3J = 9.0 Hz, 2H), 8.31 (dd,3J = 9.0 Hz,4J = 25 1.7 Hz, 4H), 8.16 – 8.10 (m, 4H), 7.76 (d,3J = 9.0 Hz, 2H), 7.55 – 7.43 (m, 6H), 7.35 (d,3J 48 = 3.7 Hz, 2H), 7.25 (d,3J = 9.0 Hz, 2H), 7.10 (d,3J = 9.0 Hz, 2H), 5.39 (s, 2H), 4.80 (s, 2H), 3.99 (s, 4H), 2.89 (s, 18H), 1.54 (s, 9H). Synthesis of Waza-pO-1: Step 1 5 TFA (0.5 mL) was added to a solution of compound Waza-7 (35 mg, 0.037 mmol) in MeCN (5 mL) and the solution was stirred at 40°C for three days. The solvent was removed under vacuo and the residual TFA was removed with serial additions of MeCN and subsequent removal under reduce pressure. The crude product was directly engaged in the next reaction without further purification or characterization. 10 Step 2 The previous product was next dissolved in dry DMF (3 mL) followed by the addition of HOBt (25 mg, 0.185 mmol, 5 equiv.), HBTU (70 mg, 0.185 mmol, 5 equiv.), and DIPEA (64 µL, 0.370 mmol, 10 equiv.) and the solution was stirred for one hour at RT. Then, Boc- TOTA (60 mg, 0.185 mmol, 5 equiv., purchased from Iris Biotech GmbH) was added and 15 the mixture was further stirred at 40°C for one hour. After completion, the mixture was concentrated under reduced pressure. Step 3 The crude product was dissolved in MeCN (3 mL) and aq. HCl 1.0 M (2 mL) was added. The solution was stirred at 40°C for two hours. The complete deprotection of the amine was20 checked by RP-HPLC-MS analysis. The reaction mixture was directly purified by semi- preparative RP-HPLC (System A) and lyophilized to obtain pure Waza-pO-1 as a dark green powder (13 mg, 32% yield over three steps). 1H NMR (500 MHz, CD3OD): δ (ppm) 8.42 (d,3J = 9.0 Hz, 2H), 8.38 (d,3J = 9.0 Hz, 2H), 8.30 (d,3J = 9.0 Hz, 2H), 8.12 (dd,3J = 9.0 Hz,4J = 1.7 Hz, 4H), 7.77 (d,3J = 9.0 Hz, 2H), 25 7.53 – 7.43 (m, 6H), 7.39 (s, 1H), 7.36 (s, 1H), 7.28 (d,3J = 9.0 Hz, 2H), 7.20 (d,3J = 9.0 Hz, 2H), 5.39 (s, 2H), 4.70 (s, 2H), 3.98 (s, 4H), 3.69 – 3.59 (m, 10H), 3.56 (t,3J = 6.1 Hz, 2H), 3.39 (t,3J = 6.1 Hz, 2H), 3.10 (t,3J = 6.1 Hz, 2H), 2.89 (s, 18H), 1.96 – 1.90 (m, 2H), 1.84 (p,3J = 6.1 Hz, 2H). HRMS (ESI+): m / z calcd.360.52354 for [M+3H]3+, found 360.52357. 30 Synthesis of Waza-OMe and Waza-pO-2: 49 Sy nthesis of Waza-OMe Aza-OMe (0.7 g, 1.0 mmol, 1 equiv) was dissolved in DCM (25 mL). MeI in large excess (10 mL, 164.3 mmol, 160 equiv) was added and the reaction was stirred for 15 minutes at RT. The solvents were then evaporated to give pure Waza-OMe as a green solid (0.93 g, 5 93% yield). 1H NMR (500 MHz, 298 K, CD3OD) δ (ppm): 8.37 (d,3J = 8.9 Hz, 4H), 8.11 – 8.04 (m, 4H), 7.51 – 7.45 (m, 6H), 7.36 (s, 2H), 7.15 (d,3J = 8.9 Hz, 4H), 4.01 (s, 4H), 3.93 (s, 6H), 2.89 (s, 18H). HRMS (ESI+): m / z calcd.356.69450 for [M+2H]2+, found 356.69493. 10 Synthesis of Waza-pO-2: Step 1 Waza-OMe (50 mg, 0.073 mmol) was dissolved in MeCN (5 mL) followed by the addition of N-Boc-PEG4-bromide (purchased from BroadPharm company, 292 µL of a solution at 0.25 M in MeCN, 0.073 mmol, 1 equiv.) and NaHCO3(61 mg, 0.73 mmol, 10 equiv.). The15 reaction mixture was heated under refluxed overnight. The reaction was monitored by LC- MS showing the formation of the mono-PEGylated product. Then, the crude mixture was filtered to remove inorganic salts and concentrated under reduced pressure. The crude product was purified by semi-preparative RP-HPLC (System A).The product containing fractions were lyophilized to give TFA salt of mono-substituted intermediate which was used 20 directly in the next step (17 mg, yield 23%). Step 2 The previous product was next dissolved in MeCN (3 mL) followed by the addition of 4- [(1E)-2-[4-(Bromomethyl)phenyl]diazenyl]-N,N-dimethylbenzenamine (7 mg, 0.022 mmol, 50 1.3 equiv.) and NaHCO3(14 mg, 0.17 mmol, 10 equiv.). The reaction mixture was heated under refluxed for two hours. After completion, the mixture was concentrated under reduced pressure. Step 3 5 The crude product was dissolved in MeCN (3 mL) and aq. HCl 1.0 M (2 mL) was added. The solution was stirred at 40°C for two hours. The complete deprotection of the amine was checked by RP-HPLC-MS analysis. The reaction mixture was directly purified by semi- preparative RP-HPLC (System A) and lyophilized to obtain pure Waza-pO-2 as a dark green powder (5 mg, 6% yield over three steps).10 1H NMR (500 MHz, CD3OD): δ (ppm) 8.42 (d,3J = 9.0 Hz, 4H), 8.18 – 8.11 (m, 4H), 7.80 – 7.73 (m, 4H), 7.53 – 7.43 (m, 6H), 7.42 (s, 2H), 7.40 (d,3J = 8.4 Hz, 2H), 7.16 (d,3J = 9.0 Hz, 4H), 6.80 (d,3J = 9.0 Hz, 2H), 4.18 (s, 2H), 4.16 (s, 2H), 3.87 (s, 6H), 3.83 (s, 2H), 3.78 – 3.72 (m, 2H), 3.65 – 3.57 (m, 2H), 3.55 – 3.47 (m, 12H), 3.36 – 3.33 (m, 2H), 3.12 (s, 6H), 3.04 (t,3J = 5.1 Hz, 2H), 2.97 (s, 6H), 2.81 (s, 6H). 15 HRMS (ESI+): m / z calcd.570.81568 for [M+2H]2+, found 570.81506. Photophysical characterization: N o . p a . 20

Claims

51 CLAIMS 1. A compound of following formula (I): ),5 wherein: R1, R2, R3and R4, identical or different, represent a C5-C7aryl or heteroaryl group, optionally substituted with at least one group chosen from halogen, nitro, -NRcRd, -ORd, hydrazine, - CF3, -CN, and groups constituted by or comprising a linker L and at least one group V, R5and R6, identical or different, represent a hydrogen, a halogen, a linear or branched (C1- 10 C15)-group comprising an aldehyde, ketone, carboxylic acid or ester function, a nitrile, a sulfonate, a vinyl group optionally substituted by a ketone, ester or aromatic group, an imine substituted by an alkyl or aromatic group, an alkyne group optionally substituted by an alkyl or aromatic group, SPh, an aromatic chalcogen (SePh, TePh), an amide, a C5-C7aryl or heteroaryl group, optionally substituted by at least one group chosen from a halogen, - 15 NRcRd, -ORd, hydrazine, -CF3and -CN, optionally R4and R5and / or R3and R6are covalently bonded and together form a C5-C7aryl or heteroaryl group, or a polycyclic aromatic group, optionally substituted by at least one group chosen from (C1-C6)-alkyl, halogen, -NRcRd, -ORd, hydrazine, -CF3 and -CN, Rcand Rd, identical or different, represent hydrogen or a linear or branched (C1-C50)-alkyl20 group, optionally interrupted by at least one atom or group chosen from -O-, -NR-, -S-, - C(=O)-, -O-C(=O)-, -C(=O)-O-, -NR-C(=O)-, -C(=O)-NR-, -NR-C(=O)-NR’-, -NR-C(=S)- NR’-, -NR-C(=O)-O-, -O-C(=O)-NR’-, -C(R)=C(R’)-, -C≡C-, arene diyl, in particular benzene diyl, and heteroarene diyl, optionally substituted by at least one group comprising one or more heteroatoms chosen from O, N, P and / or S, in particular a group chosen from 25 quaternary ammonium, sulphate, sulfonate, and phosphonate, Raand Rb, identical or different, represent: - a linear or branched (C1-C50)-alkyl group, optionally interrupted by at least one atom or group chosen from -O-, -NR-, -N+RR’-, -S-, -C(=O)-, -O-C(=O)-, -C(=O)-O-, - NR-C(=O)-, -C(=O)-NR-, -NR-C(=O)-NR’-, -NR-C(=S)-NR’-, -NR-C(=O)-O-, -O-52 C(=O)-NR’-, -C(R)=C(R’)-, -C≡C-, arene diyl, in particular benzene diyl, and heteroarene diyl, - a group constituted by or comprising a linker L and at least one group V, V is chosen from: 5 - groups comprising one or more heteroatoms chosen from O, N, P and / or S, in particular a group chosen from quaternary ammonium, sulphate, sulfonate, and phosphonate, - bioconjugable groups, in particular chosen from amine, ammonium, carboxylic acid, activated esters, in particular N-hydrosuccinimidyl, N-hydroxysulfosuccinimide, 10 pentafluorophenyl, tetrafluorophenyl, squarate, in particular diethylsquarate, maleimide, thiol, isothiocyanate, isocyanate, oxadiazolyl methyl sulfone, azoture or azide, optionally substituted tetrazine, triazole, alkyne, in particular terminal alkyne, trans-cyclooctene, cyclooctyne, in particular dibenzocyclooctyne and bicyclononyne, 15 - fluorescence quencher groups, for example diazo groups or diazo-containing groups, - a biological vector, in particular a cyclic or linear peptide, an antibody, an antibody fragment, a nanobody, an affibody, an aptamer, a short DNA or RNA sequence, a polysaccharide, a lipid, a sugar, an amino acid, a vitamin, a AMD3100 or AMD3100- type molecule, a prostate-specific membrane antigen (PSMA) ligand, a steroid, a 20 fatty acid, a polyamine, a polyphenol, a DNA base or a caffeine derivative, - a nanoparticle, in particular a nanoparticle of 10 kDa or less or lipidic nanoparticles, more particularly a gold nanocluster or a lipid nanoparticle, for example a lipidot, - a metal complex, in particular for therapeutic purposes, formed by a chelating agent and a metal, 25 - a radiometallic complex, formed by a chelating agent, for example DOTA (1,4,7,10- tetraazacyclododecane-1,4,7,10-tetraacetic acid), and a radiometal, in particular for therapeutic or diagnostic purposes, - a metal or radiometal chelating agent, for example DOTA, L is in particular a linear or branched (C1-C50)-alkyl group, optionally interrupted by at least30 one atom or group chosen from -O-, -NR-, -S-, -C(=O)-, -O-C(=O)-, -C(=O)-O-, -NR- C(=O)-, -C(=O)-NR-, -NR-C(=O)-NR’-, -NR-C(=S)-NR’-, -NR-C(=O)-O-, -O-C(=O)- NR’-, -C(R)=C(R’)-, -C≡C-, arene diyl, in particular benzene diyl, and heteroarene diyl,53 R and R’, identical or different, represent hydrogen or a linear or branched (C1-C6)-alkyl group, or one of its tautomers, with the proviso that: 5 - at least one of R3and R4, in particular R3and R4, represent(s) a C5-C7heteroaryl group, in particular a thiophenyl group, optionally substituted with at least one group chosen from halogen, -NRcRd, -ORd, hydrazine, -CF3, -CN, and groups constituted by or comprising a linker L and at least one group V, with, in this case, R1and / or R2being different from p-N(Me)2-phenyl, and optionally Raand / or Rbbeing further 10 different from -C≡C-CH2-NH(CH3)2and / or -C≡C-CH2-N+( CH3)3, in particular different from -C≡C-CH2-NH(CH3)2; - at least one of Raand Rb, represents a group V’ of following formula -La-X-Lb-V, wherein Laand Lb, identical or different, represent a linear or branched (C1-C50)- alkyl group, optionally interrupted by at least one atom or group chosen from -O-, - 15 S-, -C(R)=C(R’)-, -C≡C-, X represents -NR- or -N+RR’-, and V is as defined above; and / or - at least one of R1, R2, R3and R4, in particular one of R1, R2, R3and R4, represents a C5-C7 aryl or heteroaryl group, substituted with at least one group chosen from groups constituted by or comprising a linker L and at least one group V; and / or 20 - R4and R5and / or R3and R6are covalently bonded and together form a C5-C7aryl or heteroaryl group, or a polycyclic aromatic group, optionally substituted by at least one group chosen from (C1-C6)-alkyl, halogen, -NRcRd, -ORd, hydrazine, -CF3 and - CN. 25 2. The compound according to claim 1, wherein R5 and / or R6, in particular R5 and R6, represent a hydrogen.

3. The compound according to anyone of the preceding claims, wherein R1 and / or R2, in particular R1 and R2, represent a C5-C7 aryl, optionally substituted with at least one group 30 chosen from halogen, nitro, -NRcRd, -ORd, hydrazine, -CF3, and -CN.

4. The compound according to anyone of the preceding claims, wherein:54 - R3and / or R4, in particular R3and R4, represent a heteroaryl group, optionally substituted with at least one group chosen from halogen, nitro, -NRcRd, -ORd, hydrazine, -CF3, and - CN; or - R3and / or R4, in particular R3or R4, represent a C5-C7aryl or heteroaryl group, substituted 5 with at least one group constituted by or comprising a linker L and at least one group V.

5. The compound according to anyone of the preceding claims, wherein at least one of Raand Rb, in particular Raor Raand Rb, represent(s) a group constituted by or comprising a linker L and at least one group V. 10 6. The compound according to anyone of the preceding claims, wherein at least one of Raand Rb, in particular Raor Raand Rb, represent(s) a group V’ of following formula -La-X- Lb-V, wherein La and Lb, identical or different, represent a linear or branched (C1-C50)-alkyl group, optionally interrupted by at least one atom or group chosen from -O-, -S-, - 15 C(R)=C(R’)-, -C≡C-, X represents -NR- or -N+RR’-, and V is as defined above.

7. The compound according to anyone of the preceding claims, wherein Ra and / or Rb, in particular Raand Rb, represent(s) a group of formula -C≡C-CH2-NR-Lb-V or -C≡C- CH2-N+RR’-Lb-V, wherein Lb, R, R’, and V are as defined in claim 1, being in particular -C20≡C-CH2-NMe-Lb-V or -C≡C-CH2-N+(Me)2-Lb-V.

8. The compound according to claim 1, chosen from:58, said compounds being optionally, if applicable, in the form of a formate or trifluoroacetate salt. 5 9. A compound of following formula (II), for use in a method of in vivo fluorescence- lifetime imaging:59 ), wherein:W is chosen from B, PO2, Ga, Al, In, Ru, Fe, Pt, Pd, Zr, Zn, Cu, Bi, Sb, Au, Rh, Ge, Sn, Ti;W being in particular B; 5 Y is N or CZ, Y being in particular N; Z is chosen from: - H; - Halogens; - OR’’ and SR’’, wherein R’’ represents hydrogen or a linear or branched (C1-C6)- 10 alkyl group; - linear or branched (C1-C6)-alkyl group; - a C5-C7 aryl or heteroaryl group being optionally substituted with at least one group chosen from halogen, nitro, -NRcRd, -ORd, hydrazine, -CF3, -CN, and groups constituted by or comprising a linker L and at least one group V, 15 R1, R2, R3 and R4, identical or different, represent a linear or branched (C1-C6)-alkyl group, a C5-C7 aryl or heteroaryl group, a -CH2=CH2-(C5-C7) aryl or -CH2=CH2-(C5-C7) heteroaryl group, said aryl or heteroaryl group being optionally substituted with at least one group chosen from halogen, nitro, -NRcRd, -ORd, hydrazine, -CF3, -CN, and groups constituted by or comprising a linker L and at least one group V, 20 R5and R6, identical or different, represent a hydrogen, a halogen, a linear or branched (C1- C15)-group comprising an aldehyde, ketone, carboxylic acid or ester function, a nitrile, a sulfonate, a vinyl group optionally substituted by a ketone, ester or aromatic group, an imine substituted by an alkyl or aromatic group, an alkyne group optionally substituted by an alkyl or aromatic group, SPh, an aromatic chalcogen (SePh, TePh), an amide, a C5-C7aryl or25 heteroaryl group, optionally substituted by at least one group chosen from a halogen, - NRcRd, -ORd, hydrazine, -CF3 and -CN, optionally R4and R5and / or R3and R6are covalently bonded and together form a C5-C7aryl or heteroaryl group, or a polycyclic aromatic group, optionally substituted by at least one group chosen from (C1-C6)-alkyl, halogen, -NRcRd, -ORd, hydrazine, -CF3 and -CN,60 Rcand Rd, identical or different, represent hydrogen or a linear or branched (C1-C50)-alkyl group, optionally interrupted by at least one atom or group chosen from -O-, -NR-, -S-, - C(=O)-, -O-C(=O)-, -C(=O)-O-, -NR-C(=O)-, -C(=O)-NR-, -NR-C(=O)-NR’-, -NR-C(=S)- NR’-, -NR-C(=O)-O-, -O-C(=O)-NR’-, -C(R)=C(R’)-, -C≡C-, arene diyl, in particular 5 benzene diyl, and heteroarene diyl, optionally substituted by at least one group comprising one or more heteroatoms chosen from O, N, P and / or S, in particular a group chosen from quaternary ammonium, sulphate, sulfonate, and phosphonate, Raand Rb, identical or different, are absent or represent: - a halogen, in particular -F or -Cl,10- a linear or branched (C1-C50)-alkyl group, optionally interrupted by at least one atom or group chosen from -O-, -NR-, -N+RR’-, -S-, -C(=O)-, -O-C(=O)-, -C(=O)-O-, - NR-C(=O)-, -C(=O)-NR-, -NR-C(=O)-NR’-, -NR-C(=S)-NR’-, -NR-C(=O)-O-, -O- C(=O)-NR’-, -C(R)=C(R’)-, -C≡C-, arene diyl, in particular benzene diyl, and heteroarene diyl, 15 - a group constituted by or comprising a linker L and at least one group V, Ra and Rb are absent when W is chosen from PO2, Ga, Al, In, Ru, Fe, Pt, Pd, Zr, Zn, Cu, Bi, Sb, Au, Rh, Ge, Sn, Ti; Raand Rbare present when W is B; V is chosen from: 20 - groups comprising one or more heteroatoms chosen from O, N, P and / or S, in particular a group chosen from quaternary ammonium, sulphate, sulfonate, and phosphonate, - bioconjugable groups, in particular chosen from amine, ammonium, carboxylic acid, activated esters, in particular N-hydrosuccinimidyl, N-hydroxysulfosuccinimide, 25 pentafluorophenyl, tetrafluorophenyl, squarate, in particular diethylsquarate, maleimide, thiol, isothiocyanate, isocyanate, oxadiazolyl methyl sulfone, azoture or azide, optionally substituted tetrazine, triazole, alkyne, in particular terminal alkyne, trans-cyclooctene, cyclooctyne, in particular dibenzocyclooctyne and bicyclononyne, 30 - fluorescence quencher groups, for example diazo groups or diazo-containing groups, - a biological vector, in particular a cyclic or linear peptide, an antibody, an antibody fragment, a nanobody, an affibody, an aptamer, a short DNA or RNA sequence, a polysaccharide, a lipid, a sugar, an amino acid, a vitamin, a AMD3100 or AMD3100-61 type molecule, a prostate-specific membrane antigen (PSMA) ligand, a steroid, a fatty acid, a polyamine, a polyphenol, a DNA base or a caffeine derivative, - a nanoparticle, in particular a nanoparticle of 10 kDa or less or lipidic nanoparticles, more particularly a gold nanocluster or a lipid nanoparticle, for example a lipidot, 5 - a metal complex, in particular for therapeutic purposes, formed by a chelating agent and a metal, - a radiometallic complex, formed by a chelating agent, for example DOTA (1,4,7,10- tetraazacyclododecane-1,4,7,10-tetraacetic acid), and a radiometal, in particular for therapeutic or diagnostic purposes, 10 - a metal or radiometal chelating agent, for example DOTA, L is in particular a linear or branched (C1-C50)-alkyl group, optionally interrupted by at least one atom or group chosen from -O-, -NR-, -S-, -C(=O)-, -O-C(=O)-, -C(=O)-O-, -NR- C(=O)-, -C(=O)-NR-, -NR-C(=O)-NR’-, -NR-C(=S)-NR’-, -NR-C(=O)-O-, -O-C(=O)- NR’-, -C(R)=C(R’)-, -C≡C-, arene diyl, in particular benzene diyl, and heteroarene diyl, 15 R and R’, identical or different, represent hydrogen or a linear or branched (C1-C6)-alkyl group, or one of its tautomers.

10. The compound for use according to claim 9, wherein said compound emits at a 20 wavelength greater than or equal to 650 nm, in particular greater than or equal to 700 nm.

11. The compound for use according to claim 9 or 10, wherein said use includes a step of measuring fluorescence variations linked to variations in physiological conditions chosen from pH, oxygen content, presence of enzymes, polarity and viscosity of cell organelles. 25 12. The compound for use according to anyone of claims 9 to 11, wherein said compound is chosen from:

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