A rhenium(i) tricarbonyl dinuclear complex and a process for preparation thereof

Abstract

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Description

FIELD OF THE INVENTIONThe present invention relates to the field of inorganic chemistry and rhenium complexes. Particularly, the present inventionrelates to rhenium (I) tricarbonyl dinuclear complex and a process of preparation thereof.BACKGROUND OF THE INVENTIONNumerous studies have investigated organic molecules containing phosphonate groups in medicinal chemistry, highlightingtheir potential antibacterial, antiviral, and anticancer activities. The development of new anticancer agents is a long-termprocess, which involves the acquisition of new compounds, screening for antitumor activity, production and formulation,animal toxicology and finally, evaluation of toxicity and antitumor activity of the compound inside animal body.Developing effective anticancer metal complexes requires a multi-faceted approach, focusing on optimizing the metalligand interactions, enhancing selectivity for cancer cells, and minimizing toxicity to healthy tissues.Key considerations include the choice of metal center, the design of ligands that promote cellular uptake and DNAinteraction, and strategies to exploit the unique metabolic environmentof cancer cells. The design and synthesis of conventional and clinical platinum (II)-based metallodrugs, cisplatin, and itsderivatives, are widely recognized for their potent chemotherapeutic effectiveness in cancer treatment. These Pt-basedinorganic complexes are the most effective agents in improving patient longevity.However, there is an increasing need for alternative anti-cancer metal complexes to address their limitations, such as drugresistance and toxic side effects on healthy tissues. In this context, several metal ion-based complexes are known for theirpromising anti-cancer activity. Moreover, considerable research has been focused on developing rhenium (I) tricarbonylcore-based metal complexes as one of the leading candidates in the biological field as anticancer agents due to theirintriguing properties, including kinetic inertness, thermodynamic stability, and rich photophysical properties. In severalliterature, the anti-cancer activity of Re(I) complexes has been reported which highlighted a mechanism of action differentfrom that of Pt-based metal complexes. Organic molecules containing phosphonate groups are well-known in medicinalchemistry for their antibacterial, antiviral and anticancer activity. Also, several reports based on dinuclear Re(I) tricarbonylcomplexes have been subjected to anticancer studies.In a recent literature, a two dinuclear Re(I) metallocycles (C1 and C2) comprising sulphato-bridged bischelating ligand andnitrogen-donor ditopic ligands (L1 or L2) are reported [Sathiyendiran et al., Chem Asian J., 2025, 0, e202401656]. Thesemetallocycles interact with DNA, inducing cancer cell death via apoptosis. Metallocycles also generate reactive oxygenspecies (ROS) and cause alterations in mitochondrial membrane potential. The cytotoxicity of Re(I) complex, fac-[{Re(CO)3}2(μ-SO4)(L1)2] (C1) was evaluated against skin cancer (B16) cell line which displayed moderate cytotoxicitywith IC50 of 25 μM. Thus, the search for potential Re(I) anticancer drug molecules to combat skin cancer with more potencyis ongoing.Therefore, there exist a need in the art to develop a transition metal complex, acting as an anticancer drug offering apromising approach to combat cancerous cells with minimal cytotoxic effect to healthy tissues.OBJECTS OF THE INVENTIONAn objective of the present invention is to provide a rhenium (I) tricarbonyl dinuclear complex having an anticancer effect.Another objective of the present invention is to provide a rhenium (I) tricarbonyl dinuclear complex havingphenylphosphonate and neutral nitrogen donor-based ligands.Still another objective of the present invention is to provide a process for synthesis of a rhenium (I) tricarbonyl dinuclearcomplex having anticancer properties.Yet another objective of the present invention is to provide a process for synthesis of a rhenium (I) tricarbonyl dinuclearcomplex with a simple one-pot synthetic approach.These and other objects and advantages of the present subject matter will be apparent to a person skilled in the art afterconsideration of the following detailed description taking into consideration accompanying drawings in which preferredembodiments of the present subject matter are illustrated.SUMMARY OF THE INVENTIONAn aspect of the present invention provides a rhenium (I) tricarbonyl dinuclear complex having the structural Formula I,Formula Iwherein X is independently selected from the group consisting of,., and.Another aspect of the present invention provides a process for synthesis of a rhenium (I) tricarbonyl dinuclear complexhaving the structural Formula I,Formula Iwherein X is independently selected from the group consisting of, andcomprising;a) mixing dirhenium decacarbonyl, phenylphosphonic acid, and a ligand in a solvent to obtain a reaction mixture;b) heating the reaction mixture at a temperature range of 140-170°C for 48-50 hours and cooling to roomtemperature to obtain colourless crystals;c) washing the colourless crystals and drying to obtain the rhenium(I) tricarbonyl dinuclear complex having thestructural Formula I.These and other aspects of the disclosed subject matter, as well as additional novel features, will be apparent from thedescription provided herein. The intent of this summary is not to be a comprehensive description of the claimed subjectmatter, but rather to provide a short overview of some of the subject matter's functionality. Other systems, methods, featuresand advantages here provided will become apparent to one with skill in the art upon examination of the following figuresand detailed description. It is intended that all such additional systems, methods, features and advantages that are includedwithin this description, be within the scope of any claims.BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGSThe illustrated embodiments of the subject matter will be best understood by reference to the drawings. The followingdescription is intended only by way of example, and simply illustrates certain selected embodiments of composite andprocesses that are consistent with the subject matter as claimed herein, wherein:Figure 1 shows a 1H NMR spectra of the synthesized L3 ligand in CDCl3 (* = CDCl3);Figure 2. shows ATR-IR spectra of complexes 1-3;Figure 3. shows 1H-NMR spectrum of 1 in DMSO-d6 (# = DMSO-d6, * = Toluene, $ = residual H2O);Figure 4. shows 1H-NMR spectrum of 2 in DMSO-d6 (# = DMSO-d6, * = Toluene, $ = residual H2O);Figure 5. shows 1H-NMR spectrum of 3 in DMSO-d6 (# = DMSO-d6, * = Toluene, $ = residual H2O);Figure 6. shows Molecular structures of 2 ((A). front and (B) side views). Color code: C = grey ; O = red, N = blue, F =green, P = orange, Re = tea;Figure 7. shows (a-b) Biocompatibility of RB5-50, RB5-90, and RB5-94 on L929 cell line. (c -h) Cytotoxicity studies ofRB5-50, RB5-90, and RB5-94 on B16, HeLa, and 4T1 cell lines;Figure 8. shows (a) Live / Dead assay of RB5-50, where untreated cells served as a negative control and 5-FU served as apositive control (Scale bar: 50 μm. (b) DCFDA assay on B16F10 cell line (Scale bar: 100 μm). (c) Spheroid assay onB16F10 cells (Scale bar: 100 μm);Figure 9 shows 1H NMR spectra of complex 1-3, recorded at various intervals of time; andFigure 10 shows 1H NMR spectra of complex C1-C2 of prior arts, recorded at various intervals of time.DETAILED DESCRIPTION OF THE INVENTIONA detailed description of various exemplary embodiments of the disclosure is described herein. It should be noted that theembodiments are described herein in such detail as to communicate the disclosure. However, the amount of details providedherein is not intended to limit the anticipated variations of embodiments; on the contrary, the intention is to cover allmodifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure.The terminology used herein is to describe particular embodiments only and is not intended to be limiting to the invention.As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the contextindicates otherwise. It will be further understood that the terms "comprises" and / or "comprising", or "includes" and / or"including" or "has" and / or "having" when used in this specification specify the presence of stated features, regions,integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more otherfeatures, regions, integers, steps, operations, elements, components, and / or groups thereof.Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning ascommonly understood by one of ordinary skill in the art to which example embodiments belong. It will be furtherunderstood that terms, e.g., those defined in commonly used dictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formalsense unless expressly so defined herein.The term "further" is used in the embodiments and claims of the present application. The said term is a well-accepted termto narrow down any principal feature. Therefore, the person skilled in the art would clearly understand the scope of the saidterm in the context of the present disclosure.As used herein, the term "transition metal" refers to a group of elements characterized by having partially filled d orbitalsin their atomic structure or in one or more of their common ions. They are located in the d-block of the periodic table,specifically in groups 3-12. These metals exhibit a variety of unique chemical and physical properties due to their electronicconfigurations, including high melting and boiling points, good electrical conductivity, and the ability to form coloredcompounds and complex ions.As used herein, the term "ligand" refers to an ion or molecule that binds to a central atom or ion, forming a coordinationcomplex. This binding typically involves the donation of an electron pair from the ligand to the central atom, creating acoordinate covalent bond. Ligands can be classified based on their charge (anionic, cationic, or neutral) and the number ofatoms they use to bind (mono-, bi-, or polydentate).As used herein, the term "tricarbonyl complexes" refers to coordination compounds where a metal atom is bonded to threecarbonyl (CO) ligands.The present invention is directed towards a rhenium(I) tricarbonyl dinuclear complex having the chemical structure ofFormula I,Formula Iwherein X is independently selected from the group consisting of,., and.In an embodiment of the present invention, there is provided a rhenium(I) tricarbonyl dinuclear complex having thechemical structure of Formula I, wherein the rhenium(I) tricarbonyl dinuclear complex is selected from the group consistingof:fac-[{Re(CO)3}2(μ-PhPO3)(1,1'-((2,4,6-trimethyl-1,3-phenylene)bis(methylene))bis(1H-benzo[d]imidazole))2],fac-[{Re(CO)3}2(μ-PhPO3)(1,1'-((2,4,6-trimethyl-1,3-phenylene)bis(methylene))bis(5,6-difluoro-1Hbenzo[d]imidazole))2], andfac-[{Re(CO)3}2(μ-PhPO3)(1,1'-((2,4,6-trimethyl-1,3-phenylene)bis(methylene))bis(1H-naphtho[2,3-d]imidazole))2].In another embodiment of the present invention, there is provided a rhenium(I) tricarbonyl dinuclear complex having thechemical structure of Formula I, wherein the rhenium(I) tricarbonyl dinuclear complex is fac-[{Re(CO)3}2(μ-PhPO3)( 1,1'-((2,4,6-trimethyl-1,3-phenylene)bis(methylene))bis(1H-benzo[d]imidazole))2] having the chemical structure,.In yet another embodiment of the present invention, there is provided a rhenium(I) tricarbonyl dinuclear complex havingthe chemical structure of Formula I, wherein the rhenium(I) tricarbonyl dinuclear complex is fac-[{Re(CO)3}2(μ-PhPO3)(1,1'-((2,4,6-trimethyl-1,3-phenylene)bis(methylene))bis(5,6-difluoro-1H-benzo[d]imidazole))2] having thechemical structure,In yet another embodiment of the present invention, there is provided a rhenium(I) tricarbonyl dinuclear complex havingthe chemical structure of Formula I, wherein the rhenium(I) tricarbonyl dinuclear complex is fac-[{Re(CO)3}2(μPhPO3)(1,1'-((2,4,6-trimethyl-1,3-phenylene)bis(methylene))bis(1H-naphtho[2,3-d]imidazole))2)2] having the chemicalstructure,Another embodiment of the present invention provides a process for synthesis of a rhenium (I) tricarbonyl dinuclearcomplex having the structural Formula I,Formula Iwherein X is independently selected from the group consisting of, andcomprising;a) mixing dirhenium decacarbonyl, phenylphosphonic acid, and a ligand in a solvent to obtain a reaction mixture;b) heating the reaction mixture at a temperature range of 140-170°C for 48-50 hours and cooling to roomtemperature to obtain colourless crystals; andc) washing the colourless crystals and drying to obtain the rhenium(I) tricarbonyl dinuclear complex having thestructural Formula I.In an embodiment of the present invention there is provided a process for synthesis of a rhenium (I) tricarbonyl dinuclearcomplex having the structural Formula I, wherein the ligand is selected from the group consisting of 1,1'-((2,4,6-trimethyl1,3-phenylene)bis(methylene))bis(1H-naphtho[2,3-d]imidazole), 1,1'-((2,4,6-trimethyl-1,3-phenylene)bis(methylene))bis(5,6-difluoro-1H-benzo[d]imidazole) and 1,1'-((2,4,6-trimethyl-1,3-phenylene)bis(methylene))bis(1H-benzo[d]imidazole).In an embodiment of the present invention there is provided a process for synthesis of a rhenium (I) tricarbonyl dinuclearcomplex having the structural Formula I, wherein the ligand is 1,1'-((2,4,6-trimethyl-1,3-phenylene)bis(methylene))bis(1Hbenzo[d]imidazole).In an embodiment of the present invention there is provided a process for synthesis of a rhenium (I) tricarbonyl dinuclearcomplex having the structural Formula I, wherein the ligand is 1,1'-((2,4,6-trimethyl-1,3-phenylene)bis(methylene))bis(5,6-difluoro-1H-benzo[d]imidazole).In an embodiment of the present invention there is provided a process for synthesis of a rhenium (I) tricarbonyl dinuclearcomplex having the structural Formula I, wherein the ligand is 1,1'-((2,4,6-trimethyl-1,3-phenylene)bis(methylene))bis(1Hnaphtho[2,3-d]imidazole).In another embodiment of the present invention there is provided a process for synthesis of a rhenium (I) tricarbonyldinuclear complex having the structural Formula I, wherein the solvent is selected from the group consisting of toluene,and acetone or a mixture thereof.In still another embodiment of the present invention there is provided a process for synthesis of a rhenium (I) tricarbonyldinuclear complex having the structural Formula I, wherein the solvent is a mixture of toluene and acetone.In yet another embodiment of the present invention there is provided a process for synthesis of a rhenium (I) tricarbonyldinuclear complex having the structural Formula I, wherein the colourless crystals are washed with hexane.Still another aspect of the present invention provides a process for synthesis of a rhenium (I) tricarbonyl dinuclear complexhaving the structural Formula I, comprising:a. mixing dirhenium decacarbonyl, phenylphosphonic acid, and a ligand in a mixture of toluene and acetone to obtaina reaction mixture;b. heating the reaction mixture at a temperature of 160°C for 48 hours and cooling to room temperature to obtaincolourless crystals; andc. washing the colourless crystals with hexane and drying to obtain the rhenium(I) tricarbonyl dinuclear complexhaving the structural Formula I,Formula Iwherein X is independently selected from the group consisting of, andYet another aspect of the present invention provides a process for synthesis of a fac-[{Re(CO)3}2(μ-PhPO3)(1,1'-((2,4,6-trimethyl-1,3-phenylene)bis(methylene))bis(1H-benzo[d]imidazole))2] (1) complex having the structuralFormula,comprising;a. mixing dirhenium decacarbonyl, phenylphosphonic acid and 1,1'-((2,4,6-trimethyl-1,3-phenylene)bis(methylene))bis(1H-benzo[d]imidazole) in a mixture of toluene and acetone to obtain a reactionmixture;b. heating the reaction mixture at a temperature of 160°C for 48 hours and cooling to room temperature to obtaincolourless crystals; andc. washing the colourless crystals with hexane and drying to obtain the fac-[{Re(CO)3}2(μ-PhPO3)(1,1'-((2,4,6-trimethyl-1,3-phenylene)bis(methylene))bis(1H-benzo[d]imidazole))2] (1) complex.Yet another embodiment of the present invention provides a process for synthesis of a fac-[{Re(CO)3}2(μ-PhPO3)(1,1'-((2,4,6-trimethyl-1,3-phenylene)bis(methylene))bis(5,6-difluoro-1H-benzo[d]imidazole))2] (2) complex having thestructural Formula,comprising:a. mixing dirhenium decacarbonyl, phenylphosphonic acid, and 1,1'-((2,4,6-trimethyl-1,3-phenylene)bis(methylene))bis(5,6-difluoro-1H-benzo[d]imidazole) in a mixture of toluene and acetone to obtain areaction mixture;b. heating the reaction mixture at a temperature of 160°C for 48 hours and cooling to room temperature to obtaincolourless crystals; andc. washing the colourless crystals with hexane and drying to obtain the fac-[{Re(CO)3}2(μ-PhPO3)(1,1'-((2,4,6-trimethyl-1,3-phenylene)bis(methylene))bis(5,6-difluoro-1H-benzo[d]imidazole))2] (2) complex.Yet another embodiment of the present invention provides a process for synthesis of a fac-[{Re(CO)3}2(μ-PhPO3)(1,1'-((2,4,6-trimethyl-1,3-phenylene)bis(methylene))bis(1H-naphtho[2,3-d]imidazole))2] (3) complex having the structuralFormula,comprising:a. mixing dirhenium decacarbonyl, phenylphosphonic acid, and 1,1'-((2,4,6-trimethyl-1,3-phenylene)bis(methylene))bis(1H-naphtho[2,3-d]imidazole) in a mixture of toluene and acetone to obtain areaction mixture;b. heating the reaction mixture at a temperature of 160°C for 48 hours and cooling to room temperature to obtaincolourless crystals; andc. washing the colourless crystals with hexane and drying to obtain the fac-[{Re(CO)3}2(μ-PhPO3)(1,1'-((2,4,6-trimethyl-1,3-phenylene)bis(methylene))bis(1H-naphtho[2,3-d]imidazole))2] (3) complex.Yet another aspect of the present invention provides a process for synthesis of 1,1'((2,4,6-trimethyl-1,3-phenylene)bis(methylene))bis(1H-naphtho[2,3-d]imidazole) having the structural Formula,comprising:i. mixing 2,3-diaminonaphthalene, NaH and THF by stirring for 3 hours at 25°C to obtain a mixture;ii. adding 1,3-bis(bromomethyl) 2,4,6-trimethylbenzene in the mixture and stirring for 48 hours to obtain a solution;iii. evaporating the solvent to half and quenching by adding water to obtain a white powder in the solution;iv. separating the white powder and drying to obtain the 1,1'((2,4,6-trimethyl-1,3-phenylene)bis(methylene))bis(1Hnaphtho[2,3-d]imidazole).The present invention describes the synthesis of three novel dinuclear heteroleptic phenylphosphonate bridgedmetallocycles fac-[{Re(CO)3}2(μ-PhPO3)(L1)2] (1), fac-[{Re(CO)3}2(μ-PhPO3)(L2)2] (2), and fac-[{Re(CO)3}2(μPhPO3)(L3)2] (3). The synthesis is based on coordination-driven self-assembly of the predesigned neutral organic ligandsL1 or L2 or L3, phenylphosphonic acid, and Re2(CO)10 via one-pot solvothermal approach at 160°C in toluene: acetonesolvent combination (Scheme 1). The metallocycles comprise two fac-[Re(CO)3] cores, two molecules of 5,6-benzimidazolyl- / difluorobenzimidazolyl- / naphthanoimidazolyl-based ditopic nitrogen donor ligands (L1 or L2 or L3), andone anionic phenyl phosphonate motif.Structures of L1, L2 and L3Scheme 1The stability of the synthesized complex in dimethylsulphoxide (DMSO) is crucial to ensure it maintains its structuralintegrity and accurate concentration for biological testing. These complexes demonstrate excellent stability in solution over2 weeks, surpassing the stability of previously reported analogous complexes (C1-C3) containing sulfate anionic ligands,[Sathiyendiran et al., Chem Asian J., 2025, 0, e202401656] which remained stable for up to 48 hours without liganddissociation.The complexes of the present invention are synthesized straightforwardly without requiring an oxidation step. Thecomplexes 1-3 of the present invention are formed directly through coordination with phenylphosphonic acid, resulting inphenylphosphonate complexes with better stability and solubility. Complexes 1-3 are evaluated for their anticancer activity,revealing the influence of the phenylphosphonate-bridged motif on cytotoxicity. Notably, metallocycle 2, featuring afluorine-decorated phenylphosphonate bridge, displays potent activity against skin cancer cells (B16), with an IC50 value of7 μM, significantly outperforming the fluorine-decorated sulfate-bridged metallocycle C1 [Sathiyendiran et al., Chem AsianJ., 2025, 0, e202401656], which has an IC50 value of 25 μM.The present invention also describes the synthesis of a new neutral nitrogen donor motif 1,1'-((2,4,6-trimethyl-1,3-phenylene)bis(methylene))bis(1H-naphtho[2,3-d]imidazole) (L3).Complex 1: fac-[{Re(CO)3}2(μ-PhPO3)(L1)2] : fac-[{Re(CO)3}2(μ-PhPO3)(1,1'-((2,4,6-trimethyl-1,3-phenylene)bis(methylene))bis(1H-benzo[d]imidazole))2].Complex 2: fac-[{Re(CO)3}2(μ-PhPO3)(L2)2]: fac-[{Re(CO)3}2(μ-PhPO3)(1,1'-((2,4,6-trimethyl-1,3-phenylene)bis(methylene))bis(5,6-difluoro-1H-benzo[d]imidazole))2].Complex 3: fac-[{Re(CO)3}2(μ-PhPO3)(L3)2]: fac-[{Re(CO)3}2(μ-PhPO3)(1,1'-((2,4,6-trimethyl-1,3-phenylene)bis(methylene))bis(1H-naphtho[2,3-d]imidazole))2].Ligand 1: L1: 1,1'-((2,4,6-trimethyl-1,3-phenylene)bis(methylene))bis(1H-benzo[d]imidazole).Ligand 2: L2: 1,1'-((2,4,6-trimethyl-1,3-phenylene)bis(methylene))bis(5,6-difluoro-1H-benzo[d]imidazole).Ligand 3: L3: 1,1'-((2,4,6-trimethyl-1,3-phenylene)bis(methylene))bis(1H-naphtho[2,3-d]imidazole).EXAMPLESFollowing examples are given by way of illustration, therefore, should not be construed to limit the scope of the invention.Material and MethodsRe2(CO)10, 1,3-bis(bromomethyl)benzene, 4,5-difluoro-1,2-phenylenediamine, paraformaldehyde, 30-33% HBr in AcOH,glacial acetic acid, formic acid, sodium hydride, and phenylphosphonic acid were obtained from commercial sources andused as received. Toluene, mesitylene, acetone, and DMF were used as received. Nitrogen donor ligands (L1 and L2), 1,3-bis(bromomethyl)-2,4,6-trimethylbenzene, 5,6-difluorobenzimidazole, and 2,3-naphthalenediamine were prepared by using conventional procedures. THF and hexane were distilled by conventional procedure. ATR-IR spectra were recorded on aNicolet iS5 ATR- spectrometer. NMR spectra were recorded on a BrukerAvance III 500 MHz spectrometer.Thiazolyl Blue Tetrazolium Bromide (MTT) was acquired from Sigma Aldrich, USA. Roswell Park Memorial Institute(RPMI), Dulbecco's Modified Eagle Medium (DMEM), Fetal Bovine Serum (FBS), Phosphate-buffered Saline (PBS), andPenicillin / Streptomycin were acquired from HiMedia Chemicals, Mumbai, India. Propidium Iodide (PI), FluoresceinDiacetate (FDA), and 2'-7'-Dichlorodihydrofluorescein Diacetate (DCFH-DA) were procured from Sigma Aldrich, USA.The reagents employed in the studies were of analytical grade.Cell Lines and MaintenanceThe L929 mouse fibroblast cell line, NIH3 / T3 mouse embryonic fibroblast cell line, 4T1 murine mammary carcinoma cellline, B16F10 human melanoma cancer cell line, and HeLa human cervical cancer cell line were procured from the NationalCentre for Cell Sciences (NCCS), Pune, Maharashtra, India. The cell lines were cultivated in DMEM / RPMI media enrichedwith 10% (v / v) fetal bovine serum (FBS), 1% L-Glutamine, and 100 U / mL penicillin / streptomycin, and were sustained at37°C in a humidified environment with 5% CO2 under sterile circumstances.Example 1SYNTHESIS OF fac-[{Re(CO)3}2(μ-PhPO3)(L1)2] (1): [fac-[{Re(CO)3}2(μ-PhPO3)(1,1'-((2,4,6-trimethyl-1,3-phenylene)bis(methylene))bis(1H-benzo[d]imidazole))2]A mixture of Re2(CO)10 (50.33 mg, 0.077 mmol), PhPO3H2 (12.32 mg, 0.078 mmol), L1 [1,1'-((2,4,6-trimethyl-1,3-phenylene)bis(methylene))bis(1H-benzo[d]imidazole)] (58.56 mg, 0.154 mmol), toluene (6 mL) and acetone (1 mL), wassealed in a Teflon-lined stainless-steel bomb and heated at 160°C for 48 hours. Upon cooling the bomb to room temperature,colourless crystals were obtained. The crystals were washed with hexane and air-dried to obtain the fac-[{Re(CO)3}2(μPhPO3)( 1,1'-((2,4,6-trimethyl-1,3-phenylene)bis(methylene))bis(1H-benzo[d]imidazole))2] (1).Yield: 72% (82 mg).1H NMR (500 MHz, DMSO-d6): δ 9.96 (s, 2H, Ha), 8.00-7.93 (m, 6H, Hb,b',e), 7.68 (broad, 2H, Hphenyl), 7.62 (t, J = 7.48 Hz,2H, Hc), 7.57 (t, J = 7.70 Hz, 2H, Hc'), 7.41 (s, 1H, Hf), 7.31 (t, J = 7.62 Hz, 2H, Hd), 7.25-7.12 (m, 2H, Hphenyl and Htoluene),6.95 (s, 1H, Ha'), 6.87 (t, J = 7.81 Hz, 2H, Hd'), 6.62 (s, 1H, Hf'), 6.27 (d, J = 8.39 Hz, 2H, He' ), 5.68 (d, J = 14.26 Hz, 2H,-CH2-), 5.48-5.41 (m, 4H, -CH2-), 4.63 (d, J = 14.27 Hz, 2H, -CH2-), 2.40 (s, 6H, -CH3), 2.26 (s, 3H, -CH3), 1.86 (s, 3H, -CH3), and 1.00 (s, 6H, -CH3).ATR-IR (cm-1): 2008 (C=O), 1899 (C=O). and 1833 (C=O).Example 2SYNTHESIS OF fac-[{Re(CO)3}2(μ-PhPO3)(L2)2] (2): [fac-[{Re(CO)3}2(μ-PhPO3)(1,1'-((2,4,6-trimethyl-1,3-phenylene)bis(methylene))bis(5,6-difluoro-1H-benzo[d]imidazole))2]A mixture of Re2(CO)10 (51.2 mg, 0.078 mmol), PhPO3H2 (12.20 mg, 0.077 mmol), L2 [1,1'-((2,4,6-trimethyl-1,3-phenylene)bis(methylene))bis(5,6-difluoro-1H-benzo[d]imidazole)] (62.90 mg, 0.153 mmol), toluene (6 mL) and acetone(1 mL), was sealed in a Teflon-lined stainless-steel bomb and heated at 160°C for 48 hours. Upon cooling the bomb to roomtemperature, light colourless crystals were obtained. The crystals were washed with hexane and air dried to obtain the fac-[{Re(CO)3}2(μ-PhPO3)( 1,1'-((2,4,6-trimethyl-1,3-phenylene)bis(methylene))bis(5,6-difluoro-1H-benzo[d]imidazole))2](2).Yield: 73.43% (91 mg).1H NMR (500 MHz, DMSO-d6): δ 9.99 (s, 2H, Ha ), 8.29 (t, J = 7.88 Hz, 2H, Hb ), 8.18 (t, J = 7.58 Hz, 2H, He ), 7.81 (t, J =7.75 Hz, 2H, Hb'), 7.73-7.58 (m, 2H, Hphenyl), 7.41 (s, 1H, Hd ), 7.25-7.12 (m, 8H, Hphenyl and Htoluene), 6.98 (s, 2H, Ha'), 6.69(s, 1H, Hd'), 6.13-6.09 (m, 2H, Hc'), 5.69 (d, J = 14.5 Hz, 2H, -CH2-), 5.50 (d, J = 14.5 Hz, 2H, -CH2-), 5.42 (d, J = 14.3Hz, 2H, -CH2-), 4.87 (d, J = 14.5 Hz, 2H, -CH2-), 2.36 (s, 6H, -CH3), 2.25 (s, 3H, -CH3), 1.93 (s, 3H, -CH3), and 1.13 (s,6H, -CH3).ATR-IR (cm-1 ): 2014 (C=O), 1903 (C=O). and 1861 (C=O).Example 3SYNTHESIS OF fac-[{Re(CO)3}2(μ-PhPO3)(L3)2] (3): [fac-[{Re(CO)3}2(μ-PhPO3)(1,1'-((2,4,6-trimethyl-1,3-phenylene)bis(methylene))bis(1H-naphtho[2,3-d]imidazole))2]A mixture of Re2(CO)10 (50.7 mg, 0.078 mmol), PhPO3H2 (12.00 mg, 0.076 mmol), L3 [1,1'-((2,4,6-trimethyl-1,3-phenylene)bis(methylene))bis(1H-naphtho[2,3-d]imidazole)] (73.62 mg, 0.153 mmol), toluene (5 mL) and acetone (1 mL)were sealed in a Teflon-lined stainless-steel bomb and heated at 160°C for 48 hours. Upon cooling the bomb to roomtemperature, light colourless crystals were obtained. The crystals were washed with hexane and air dried to obtain fac-[{Re(CO)3}2(μ-PhPO3)( 1,1'-((2,4,6-trimethyl-1,3-phenylene)bis(methylene))bis(1H-naphtho[2,3-d]imidazole))2] (3).Yield: 64% (82 mg).1H NMR (500 MHz, DMSO-d6): δ 10.26 (s, 2H, Ha ), 8.65 (s, 2H, Hb ), 8.48 (s, 2H, Hg ), 8.47 (s, 2H, Hg'), 8.33 (d, J = 7.93Hz, 2H, Hc ), 8.19 (d, J = 8.06 Hz, 2H, Hc'), 8.04 (d, J = 8.60 Hz, 2H, Hf ), 7.78 (broad, 2H, Hphenyl), 7.67-7.61 (m, 2H, He,e'),7.48 (s, 1H, Hh ), 7.38 (t, 2H, J = 7.66 Hz, Hd ), 7.37 (s, 1H, Ha'), 7.28-7.13 (m, Hd',phenyl,toluene), 6.69 (s, 2H, Hb' ), 6.58 (s, 1H,Hh'), 6.57 (d, J = 8.00 Hz, 2H, Hf'), 5.82 (d, J = 14.18 Hz, 2H, -CH2-), 5.54 (d, J = 14.18 Hz, 2H, -CH2-), 5.44 (d, J = 14.28Hz, 2H, -CH2-), 4.54 (d, J = 14.42 Hz, 2H, -CH2-), 2.45 (s, 6H, -CH3), 2.34 (s, 3H, -CH3), 1.95 (s, 3H, -CH3), and 0.60 (s,6H, -CH3).ATR-IR (cm-1 ): 2008 (C=O), 1889 (C=O) and 1848 (C=O).EXAMPLE 4PROCESS FOR SYNTHESIS OF L3 [1,1'-((2,4,6-trimethyl-1,3-phenylene)bis(methylene))bis(1H-naphtho[2,3-d]imidazole)]2,3-diaminonaphthalene (127 mg, 0.757 mmol), NaH (75 mg, 1.13 mmol), and THF (20 ml) were mixed and stirred for 3hours at room temperature to obtain a mixture. 1,3-bis(bromomethyl) 2,4,6-trimethylbenzene (101 mg, 0.378 mmol) wasadded to the mixture and allowed to stir for 48 hours to obtain a solution. The solvent in the solution was evaporated to halfand quenched by adding water (~200 mL) to obtain a white powder. The resulting white powder was collected by filtration,washed several times with water, and air-dried.Yield: 93% (170.00 mg).1H NMR (500 MHz, CDCl3): δ 8.30 (s, 2H, Ha ), 8.02 (d, 2H, Hc ), 7.97 (d, 2H, Hf ), 7.87 (s, 2H, Hb ), 7.61 (s, 2H, Hg ), 7.47-7.41 (m, 4H, Hd,e), 7.20 (s, 1H, Hh ), 5.39 (s, 4H, -CH2-), 2.40 (s, 6H, -CH3) and 2.21 (s, 3H, -CH3).Figure 1 shows a 1H NMR spectra of the synthesized L3 ligand in CDCl3 (* = CDCl3), confirming the synthesis of L3.Example 5CHARACTERIZATION5.1 Attenuated Total Reflectance-Fourier Transform Infrared (ATR-IR) SpectroscopyATR-IR spectra were recorded on a Nicolet iS5 ATR- spectrometer.Figure 2. shows ATR-IR spectra of complexes 1-3.The IR spectra of the metallocycles displayed three intense bands in the range of 2008-1861 cm-1, characteristic of the fac[Re(CO)3] core in an asymmetric environment (Figure 1).The results reveal / confirms that fac-[Re(CO)3] core is present in the metallocycles, which is possible only when the metalprecursor (Re2(CO)10) in reaction with the ligand results in the formation of metallocycles containing two fac-[Re(CO)3]cores.5.2 1H-NMR spectraNMR spectra were recorded on a Bruker Avance III 500 MHz spectrometer.Figure 3. shows 1H-NMR spectrum of 1 in DMSO-d6 (# = DMSO-d6, * = Toluene, $ = residual H2O).Figure 4. shows 1H-NMR spectrum of 2 in DMSO-d6 (# = DMSO-d6, * = Toluene, $ = residual H2O).Figure 5. shows 1H-NMR spectrum of 3 in DMSO-d6 (# = DMSO-d6, * = Toluene, $ = residual H2O).The complexes were characterized by 1H-NMR spectra in DMSO-d6 (Figure 3, 4, 5). Two sets of well-resolved chemicalresonances with equal intensity were observed for the benzimidazolyl / 5,6-fluorobenzimidazolyl / naphthanoimidazolyl andthe central mesitylene spacer. The spectra indicated that the metallocyclic structure was retained in the solution.5.3 Single crystal X-ray Diffraction AnalysisSingle crystals suitable for SCXRD analysis were obtained from a solvothermal bomb upon cooling.Figure 6. shows Molecular structures of 2 ((A). front and (B) side views). Color code: C = grey ; O = red, N = blue, F =green, P = orange, Re = tea.The molecular structure of 2 was confirmed using single-crystal X-ray diffraction analysis (Figure 6). The Re(I) complex2 crystallize in Pnma space group. The metallocycle comprises of two fac-[Re(CO)3]+cores, a bidentate phenyl phosphonateanionic ligand that bridges the two rhenium centers, and two neutral ditopic nitrogen-donor ligands (L2), resulting in acyclic cage-like structure. The crystal structure is stabilized by a range of intermolecular non-covalent interactions,including C-H···O, C-H···π, and lone pair···π interactions.Proton NMR spectra recorded from the powder sample confirmed the formation of complex 1 and 3. SCXRD analysis wascarried out only for complex 2.Example 6Biocompatibility StudiesThe biocompatibility of rhenium (I) tricarbonyl dinuclear complexes (1-3) were assessed utilizing two murine cell models:L929 mouse fibroblasts and NIH 3T3 mouse embryonic fibroblasts.Complex 1: RB5-50Complex 2: RB5-90Complex 3: RB5-94Cells were inoculated in 96-well plates at a density of 1x104cells per well and permitted to adhere during a 24-hour preincubation period under standard culture conditions (37°C, 5% CO2). Complexes RB5-50, RB5-90 and RB5-94 wereserially diluted in full growth medium to doses of 1, 5, 10, 25, and 50 μg, and thereafter incubated with adherent cellmonolayers for 24 hours. Post-treatment, viability was assessed using the MTT test, in which mitochondrial dehydrogenaseactivity converts tetrazolium salts to formazan crystals in proportion to metabolic activity. This standardized procedurefacilitates systematic comparison of chemical cytotoxicity among various cell types.Figure 7. (a-b) shows Biocompatibility of RB5-50, RB5-90, and RB5-94 on L929 cell line.To establish preliminary therapeutic indices, the cytocompatibility of rhenium(I) tricarbonyl dinuclear complexes (1-3)(RB5-50, RB5-90, and RB5-94, respectively) was systematically evaluated. Under conventional culture conditions, cellswere subjected to a concentration gradient of 1-50 μg (1, 5, 10, 25, and 50) of each complex for 24 hours. Dose-responseassessments showed minimal cytotoxicity (cell viability > 80%) at doses ≤ 20 μg for all cell types (Figure 6 a, b), with IC50values above 25 μg, indicating biocompatibility at therapeutically relevant dosages. This early profiling in multiple normalcell models supports these complexes for anticancer screening and suggests their potential selectivity for malignant versusnon-transformed tissues.Example 7Cytotoxicity StudiesThe cytotoxicity of rhenium(I) tricarbonyl dinuclear complexes (1-3) was assessed in vitro using murine mammarycarcinoma (4T1), human melanoma (B16F10), and human cervical cancer (HeLa) cell lines by the MTT method.Cells were inoculated in 96-well plates at a density of 1 x 104 cells per well and incubated at 37°C with 5% CO2 for 24hours to facilitate cell adherence. Cells were subsequently treated with different concentrations (1, 5, 10, 25, and 50 μg) ofthe complexes (RB5-50, RB5-90, and RB5-94). Untreated cells function as the negative control. Following 24 hours ofchemical exposure, the media was substituted with fresh DMEM or RPMI containing MTT reagent (5 mg / mL), and thecells were cultured for an additional 3 hours to facilitate formazan crystal formation. The resultant crystals were solubilizedin DMSO, and absorbance was quantified at 570nm and 630nm via a multimode plate reader to evaluate cell viability.Figure 7. (c -h) shows cytotoxicity studies of RB5-50, RB5-90, and RB5-94 on B16, HeLa, and 4T1 cell lines. The testsshowed that RB5-50 and RB5-94 had the highest IC50 potency in B16F10 cells (25 ± 1.23 μg), while RB5-90 had optimalactivity (30 ± 1.63μM) (Figure 6 c, d). Viability was 100% for untreated cells as negative controls. Selectivity indices (SI)were calculated to measure treatment specificity: SI = (IC50 value in normal cells) / (IC50 value in cancer cells).The thresholds for SI are: SI < 1 (normal cell toxicity), SI = 1 (equal toxicity), SI > 1 (cancer cell selectivity), and SI >> 1(high specificity). RB5-50 had a SI of 2 in B16F10 compared to L929 mouse fibroblasts, while RB5-90 had a SI of 1.6(Tables 1 and 2). Their specific cytotoxicity toward malignant cells suggests they could be selective chemotherapeutic drugswith a wider treatment window. Therefore, RB5-50 was selected for future testing because it has the best selectivity index.Table 1:Table 2:Example 82',7'-dichlorofluorescin diacetate (DCFDA) AnalysisReactive oxygen species (ROS) are extremely reactive entities originating from molecular oxygen. Under physiologicalconditions, reactive oxygen species (ROS) are crucial in regulating cellular functions including proliferation, migration,and differentiation. Excessive formation of reactive oxygen species (ROS) can induce oxidative stress, causing cellulardamage and contributing to numerous pathological diseases, including cancer, neurodegeneration, and aging. Reactiveoxygen species (ROS) are produced endogenously by cellular metabolism, chiefly inside the mitochondrial electrontransport chain, as well as by the action of enzymes such as NADPH oxidases and in reaction to external stimuli.The quantification and examination of reactive oxygen species (ROS) production are essential for comprehending its dualfunctions in cellular signaling and oxidative injury. Various analytical methods have been established to identify andmeasure reactive oxygen species in biological systems. Fluorogenic probes, like DCFDA, are frequently utilized for theirsensitivity and capacity to deliver real-time evaluations of intracellular ROS levels. The production of reactive oxygenspecies by rhenium-based metallic complexes was evaluated using the DCFDA staining test.Subsequent to the seeding and adherence of B16F10 human melanoma cells (1x105 cells / well) in well plates, the cells weresubjected to the complex 1 (RB5-50 (IC50 concentration 25 μg)). Following a 24-hour incubation period, 10 μM DCFDAwas added to each well, and fluorescence imaging was conducted utilizing a fluorescence microscope. Untreated cellsfunctioned as the negative control, whereas 5-FU-treated cells were utilized as a positive control for the study of ROSproduction.Figure 8. shows (b) DCFDA assay on B16F10 cell line (Scale bar: 100 μm)Intracellular esterases de-esterify the cell-permeable probe to non-fluorescent DCFH, which ROS oxidize to fluorescentdichlorofluorescein. DCF-derived green fluorescence intensity (ex / em: 488 / 530 nm) in treated cells was significantly higherthan in untreated controls and other treatment groups (Figure 8b). B16F10 cells treated with RB5-50 had a much higherfluorescence signal than controls, indicating complex-dependent ROS buildup. Untreated cells showed low fluorescence,indicating endogenous antioxidant mechanisms maintain basal ROS levels. RB5-50's pro-oxidant potency in altering redoxhomeostasis matches its lethal effects.Example 9Live Dead AssayThe live / dead assay employing fluorescein diacetate (FDA) and propidium iodide (PI) labeling is an expedient anddependable technique for evaluating cell viability. In the experiment, FDA, a non-fluorescent chemical, readily penetratesintact cell membranes and is degraded by intracellular esterases in viable cells to provide green-fluorescent fluorescein,which acts as a signal of metabolic activity and cell viability. Conversely, PI is a red-fluorescent nucleic acid stain that isunable to traverse the intact membranes of live cells, yet easily infiltrates cells with compromised membranes, attaching toDNA and marking dead or membrane-damaged cells red.B16F10 cells were pre-treated with complex 1 (RB5-50 (IC50 concentration 25 μg)) and incubated for 24 hours for theprocess. Subsequent to the treatment, the cells were treated with both FDA and PI, generally by introducing the dyes directlyinto the cell culture medium and incubating for 10 minutes at ambient temperature, shielded from light. Followingincubation, cells were promptly examined utilizing a fluorescent microscope (Zoe Microscope). Viable cells emit greenfluorescence, whilst non-viable cells exhibit red fluorescence, facilitating distinct two-color differentiation and enablingqualitative or quantitative evaluation of cell viability inside the complexes.Figure 8 shows (a) Live / Dead assay of RB5-50, where untreated cells served as a negative control and 5-FU served as apositive control (Scale bar: 50 μm).Upon testing for anti-cancer activity using FDA / PI dual staining, FDA was digested by live cells to give green fluorescence(488 / 530 nm), indicating metabolic activity, while PI preferentially labeled membrane damaged cell nuclei red (535 / 617nm). Fluorescence microscopy showed that RB5-50 treated B16F10 cultures had more PI-positive cells (bright redfluorescence) than untreated controls and other treatment groups (Figure 8a). Untreated groups showed green fluorescence,indicating >90% vitality, while 5-FU-positive controls showed intermediate PI staining. These findings support previouscytotoxicity studies that RB5-50 selectively induces cell death in a cell line-dependent way.Example 103D Spheroids ModelCancer research relies on the 3D spheroid model because the model better replicates a solid tumor architecture,microenvironment, and physiological circumstances than 2D cell cultures. Spheroids mimic in vivo tumors by replicatingcell-cell and cell-matrix interactions, oxygen and nutrition gradients, and proliferative, quiescent, and necrotic cellpopulations. This model helps researchers examine tumor biology, drug penetration, and resistance mechanisms, offeringmore predictive and clinically meaningful data for chemotherapeutic efficacy and toxicity. Thus, 3D spheroid culturesconnect conventional cell culture and animal models, improving preclinical drug screening and minimizing animal testing.Ultra-low attachment (ULA) 96-well plates with hydrophilic, non-adhesive surfaces enable scaffold-free self-assembly ofB16F10 cells into 3D spheroids. Incubating B16F10 cells at 3-4x103 cells / well for 5 days at 5% CO2 and 37°C resulted incompact, hypoxic-core spheroids that mimic solid tumor physiology.Figure 8c shows spheroid assay on B16F10 cells (Scale bar: 100 μm).Rhenium(I) tri-carbonyl complex (RB5-50 (IC50 concentration 25 μg) treated spheroids for 24 hours after assembly showedantineoplastic action in 3D models. Dual FDA / PI staining measured cell viability 24 hours post-treatment. FDA (5 μg / mL)showed metabolic activity in live cells by hydrolyzing intracellular esterases by green fluorescence, while PI (2 μg / mL)bound nuclear DNA in membrane-compromised cells and emitted red fluorescence. A Zoe microscope was used forfluorescent imaging, and viability indices were calculated by comparing FDA+ / PI- cells to total cells, adjusted againstuntreated controls. The technique preserved spheroid structural integrity while assessing chemotherapeutic activity.Qualitative examination showed that treated spheroids had lower cellular viability than untreated controls and other controlgroups, as seen by increased PI penetration and decreased fluorescein signal intensity (Figure 8c). The cytotoxic responsein 3D cultures matched 2D monolayer experiments, proving chemical effectiveness in both models. This consistency showsthat the spheroid microenvironment retains drug penetration and biological activity, despite 3D systems' greaterphysiological relevance than monolayer cultures.Example 11Stability of the complexes 1-3The complexes 1-3 demonstrate excellent stability in solution for over 2 weeks, surpassing the stability of previouslyreported analogous complexes (C1-C3) containing sulfate anionic ligands, [Sathiyendiran et al., Chem Asian J., 2025, 0,e202401656] which remained stable for up to 48 hours without ligand dissociation. Furthermore, complexes 1-3 exhibitenhanced solubility in DMSO compared to previously reported sulfate complexes C1 and C2.To study the stability of the complexes, 1H NMR spectra of complex 1-3 were recorded at various intervals of time asdepicted in Figure 8, wherein 1H NMR spectra of C1 and C2 are also provided in Figure 9 for comparison basis.Figure 9 shows 1H NMR spectra of complex 1-3, recorded at various intervals of time.Figure 10 shows 1H NMR spectra of complex C1-C2 of prior arts, recorded at various intervals of time.Complexes 1-3 of the present invention exhibited improved solubility, being readily soluble in DMSO without the need forrigorous heating, unlike the previously reported complex C1 and C2 which requires extensive heating to dissolve.It should be noted that the description and figures merely illustrate the principles of the present subject matter. It should beappreciated by those skilled in the art that conception and specific embodiment disclosed may be readily utilized as a basisfor modifying or designing other structures for carrying out the same purposes of the present subject matter. The novelfeatures which are believed to be characteristic of the present subject matter, both as to its organization and method ofoperation, together with further objects and advantages will be better understood from the following description whenconsidered in connection with the accompanying figures.It will be further appreciated that functions or structures of a plurality of components or steps may be combined into a singlecomponent or step, or the functions or structures of one-step or component may be split among plural steps or components.The present invention contemplates all of these combinations. Unless stated otherwise, dimensions and geometries of thevarious structures depicted herein are not intended to be restrictive of the invention, and other dimensions or geometries arepossible. In addition, while a feature of the present invention may have been described in the context of only one of theillustrated embodiments, such feature may be combined with one or more other features of other embodiments, for anygiven application. It will also be appreciated from the above that the fabrication of the unique structures herein and theoperation thereof also constitute methods in accordance with the present invention. The present invention also encompassesintermediate and end products resulting from the practice of the methods herein.

Claims

1. A rhenium(I) tricarbonyl dinuclear complex having the structural Formula I, Formula I wherein X is independently selected from the group consisting of , , and .

2. The complex as claimed in claim 1, wherein the rhenium(I) tricarbonyl dinuclear complex is selected from the group consisting of: fac-[{Re(CO)3}2(μ-PhPO3)(1,1'-((2,4,6-trimethyl-1,3-phenylene)bis(methylene))bis(1Hbenzo[d]imidazole))2], fac-[{Re(CO)3}2(μ-PhPO3)(1,1'-((2,4,6-trimethyl-1,3-phenylene)bis(methylene))bis(5,6-difluoro-1Hbenzo[d]imidazole))2], and fac-[{Re(CO)3}2(μ-PhPO3)(1,1'-((2,4,6-trimethyl-1,3-phenylene)bis(methylene))bis(1H-naphtho[2,3- d]imidazole))2].

3. A process for synthesis of a rhenium(I) tricarbonyl dinuclear complex having the structural Formula I Formula I wherein X is independently selected from the group consisting of , . , and comprising; a) mixing dirhenium decacarbonyl, phenylphosphonic acid, and a ligand in a solvent to obtain a reaction mixture; b) heating the reaction mixture at a temperature range of 140-170°C for 48-50 hours and cooling to room temperature to obtain colourless crystals; and c) washing the colourless crystals and drying to obtain the rhenium(I) tricarbonyl dinuclear complex having the structural Formula I.

4. The method as claimed in claim 3, wherein the ligand is selected from the group consisting of 1,1'-((2,4,6-trimethyl1,3-phenylene)bis(methylene))bis(1H-naphtho[2,3-d]imidazole), 1,1'-((2,4,6-trimethyl-1,3- phenylene)bis(methylene))bis(1H-benzo[d]imidazole) and 1,1'-((2,4,6-trimethyl-1,3- phenylene)bis(methylene))bis(5,6-difluoro-1H-benzo[d]imidazole).

5. The method as claimed in claim 3, wherein the solvent is selected from the group consisting of toluene, and acetone or a mixture thereof.

6. The method as claimed in claim 3, wherein the colourless crystals are washed with hexane.

7. A process for preparing the ligand 1,1'-((2,4,6-trimethyl-1,3-phenylene)bis(methylene))bis(1H-naphtho[2,3- d]imidazole) as claimed in claim 4 having the structural Formula, comprising: i. mixing 2,3-diaminonaphthalene, NaH and THF by stirring for 3 hours at 25°C to obtain a mixture; ii. adding 1,3-bis(bromomethyl) 2,4,6-trimethylbenzene in the mixture and stirring for 48 hours to obtain a solution; iii. evaporating the solvent to half and quenching by adding water to obtain a white powder in the solution; iv. separating the white powder and drying to obtain the 1,1'((2,4,6-trimethyl-1,3- phenylene)bis(methylene))bis(1H-naphtho[2,3-d]imidazole).