D-f transition rare earth complex and application thereof as photoluminescent material

Abstract

The invention relates to a d-f transition rare earth complex, which has any one of the following structures: the rare earth complex can be used as fluorescent powder or a photoluminescent material.

Description

Technical Field

[0001] This invention belongs to the field of organic phosphors and organic photoluminescence. In particular, this invention relates to various multidentate chelate df transition rare earth complexes and their applications as light-converting phosphors and photoluminescent materials. Background Technology

[0002] Compared to ff-transition rare earth ions such as Eu(III) and Tb(III) with longer excited-state lifetimes and relatively fixed emission spectra, df-transition rare earth ions, represented by Ce(III) and Eu(II), have the characteristics of short excited-state lifetimes, high absorption intensity, and tunable spectra. In recent years, a series of Ce(III) and Eu(II) molecular complexes with high luminous efficiency have been synthesized and designed, and research on their electroluminescent devices has demonstrated the great potential of these materials in the display field. However, the emission of Ce(III) complexes is mostly concentrated in the blue to blue-green light region, and there are few reports on Ce(III) complexes that emit green light or even red light in the longer wavelength range, and their luminous efficiency and air stability are not satisfactory. In contrast, although the emission of Eu(II) is easier to adjust in the entire visible region, there are also fewer reports on Eu(II) molecular complexes that emit red light or even near-infrared light compared to inorganic systems. Summary of the Invention

[0003] The inventors of this invention recognized that Ce has a crustal abundance comparable to Cu and Zn, thus Ce-based materials offer the advantage of low cost. Furthermore, Ce(III) exhibits the highest air stability in df transition systems in terms of standard oxidation potential, making it easier to construct a series of stable luminescent materials. In addition, molecular complexes based on organic ligands achieve good solubility and handleability, have relatively mild synthesis processes, and good compatibility with organic systems, showing broad application prospects in photoluminescence and electroluminescence.

[0004] On the other hand, most current df transition rare earth complexes revolve around chelated N and O ligands, while complexes coordinated with S or softer nonmetals (such as Se and Te) are rarely reported. S's strong electron-donating ability and relatively high electronegativity offer the possibility of achieving both strong-field ligand and stability. Therefore, the synthesis and study of S-coordinated df transition rare earth complexes are of great significance to the development of the df transition field. In this invention, other soft base-coordinated and P-coordinate-assisted Ce(III) and Eu(II) complexes were also synthesized for further reference.

[0005] In recent years, a series of Ce(III) and Eu(II) complexes based on N-coordinate ligands have exhibited excellent photophysical properties and stability, demonstrating the great potential of df transition complexes in luminescent materials. Compared to Eu(II), Ce(III) is more likely to achieve higher luminous efficiency and better stability. However, limited by the high intrinsic 5d-4f energy difference of Ce(III), the emission of Ce(III) complexes is mostly located in the short-wavelength region. Although a few complexes can achieve yellow light emission, the use of cyclopentadienyl or amino ligands brings stability issues, limiting their further applications.

[0006] In the process of exploring the design and synthesis of S-coordinated df-transition rare earth complexes, the inventors of this application surprisingly discovered that using a class of multidentate chelating ligands based on P=S or C=S coordination sites can significantly modulate the emission of Ce(III) in the visible and near-infrared regions. Simultaneously, the external alkyl or aryl groups on the ligand backbone can effectively protect the metal center, further improving the stability of the complex to air. Furthermore, thiophenol-based CS-type anionic ligands exhibit good modifiability, and ortho-position modification can enhance the rigidity of the complex molecule, achieving high-efficiency long-wavelength emission. Based on this, by derivation of the ligand backbone and adjustment of external groups, and by using Ce(III), Eu(II), and other df-transition ions as metal centers, a series of novel df-transition luminescent materials with high luminous efficiency and tunable visible region can be obtained.

[0007] Embodiments of the present invention provide a df transition rare earth complex having any of the following structures:

[0008]

[0009] Among them, R 1 R 2 It is independently selected from any one of hydrogen, unsubstituted C1-C18 alkyl, substituted C1-C18 alkyl, alkoxy, unsubstituted C1-C18 alkenyl, halogenated C1-C18 alkenyl, unsubstituted C1-C18 alkynyl, halogenated C1-C18 alkynyl, unsubstituted aryl within C50, substituted aryl within C50, C1-C18 alkyl or heterocyclic containing O, N, or S coordination sites;

[0010] X is O, S, or NR, where R is any one of the following: unsubstituted C1-C18 alkyl, substituted C1-C18 alkyl, C1-C18 alkoxy, unsubstituted C1-C18 alkenyl, halogenated C1-C18 alkenyl, unsubstituted C1-C18 alkynyl, halogenated C1-C18 alkynyl, unsubstituted aryl within C50, substituted aryl within C50, C1-C18 alkyl or heterocyclic containing O, N, or S coordination sites.

[0011] Sol is a monodentate or polydentate coordinated organic solvent molecule; preferably, Sol is selected from at least one of acetonitrile, tetrahydrothiophene, tetrahydrofuran, diethyl ether, isopropyl ether, pyridine, ethylenediamine and ethylene glycol dimethyl ether;

[0012] Y is a monovalent negative ion; preferably, Y is selected from at least one of F, Cl, Br, I, SCN and CF3SO3;

[0013] E and E' are coordinating atoms, independently selected from O, S, Se or Te;

[0014] Pc is a coordinated group VA atom, independently selected from N, P or As;

[0015] A is an alkali metal ion with a countercharge, independently selected from Li, Na, K, Rb, or Cs;

[0016] M is selected from Ce(III), Pr(III), Tb(III), Eu(II), Yb(II), Sm(II) or Tm(II);

[0017] Preferred, R 1 R 2 R is independently selected from any one of methyl, ethyl, isopropyl, tert-butyl, cyclohexyl, and phenyl. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. However, those skilled in the art will understand that this invention is not limited to the following embodiments.

[0019] The following will further illustrate the df transition rare earth complexes of the present invention and their application as photoluminescent materials with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0020] This invention synthesizes various Ce(III) and Eu(II) complexes starting from several types of multidentate S-coordination chelating ligands, with structures shown in Formula 1 below. The obtained Ce(III) complexes exhibit bright blue and yellow-green light emission, along with high quantum yield. Based on this, by changing the ligand framework and introducing sterically hindered groups, a series of Ce(III) complexes with tunable emission from blue to red light were obtained, achieving spectral tuning of the Ce(III) complexes across the entire visible region.

[0021] Unless otherwise stated, all chemical reagents used in the synthesis were commercially available and ready for use without further purification. All synthesis and purification of the complexes were performed in a glove box. The starting material, cerium trifluoromethanesulfonate (Ce(OTf)3), was vacuum dried overnight at 180°C to remove residual water. Solvents used in the synthesis of the complexes underwent special treatment: tetrahydrofuran (THF), toluene, and n-hexane were dried with Na / NaH and purified by distillation under an argon atmosphere using benzophenone as an indicator; dichloromethane (DCM) and acetonitrile (MeCN) were dried with CaH2 and purified by distillation under an argon atmosphere. The NaH used in the reaction synthesis of the complexes was pre-washed with n-hexane (3 × 20 mL) in a glove box to remove mineral oil. All glassware was dried at 120°C for at least 1 hour before use.

[0022] 1 ¹H NMR was measured on a Bruker-400MHz NMR system. Tetramethylsilane (TMS) was used as an internal reference for chemical shift correction, with δ(TMS) = 0 ppm. Elemental analysis results were obtained on a VARIO EL analyzer. X-ray photoelectron spectroscopy was performed on an AXIS Supra X-ray photoelectron spectrometer. UV-vis absorption spectral data were obtained on a Shimadzu UV-3100 spectrometer. Steady-state / transient PL spectra were obtained on an Edinburgh FLS980 spectrometer equipped with a pulsed laser. Solid powder complexes were pre-placed between two clean quartz plates and sealed with paraffin wax before testing; solutions were placed in quartz dishes under a nitrogen atmosphere and protected with PTFE stopcocks. Photoluminescence quantum yield (PLQY) was measured using an absolute PLQY measurement system (C9920-02) from Hamamatsu. Buried volume (%V) bur The calculations are performed on the webpage (https: / / www.molnac.unisa.it / OMtools / sambvca2.1 / index.html).

[0023] Example 1: Complex Ce-Bm iPr Ce-Bm tBu Ce-Tm iPr Ce-TmtBu With Eu-Tm iPr Synthesis

[0024] Sodium dihydrodi(3-isopropyl-2-imidazolium-1-yl)borohydride (NaBm) iPr Synthesis of 1-isopropyl-2-imidazolium thione: NaBH4 (567 mg, 15.0 mmol) and 1-isopropyl-2-imidazolium thione (4.27 g, 30.0 mmol) were added to 60 mL of ultradry THF and refluxed overnight. After the reaction was complete, the system was cooled, NaBH4 was removed by filtration, and the solvent was removed from the filtrate under reduced pressure. The residue was washed with near-boiling toluene to give a white powder. Yield: 1.60 g (33.5%). 1 H NMR (400MHz, DMSO-d6): δ7.03(d,2H), 6.80(d,2H), 5.00-4.79(m,2H), 1.19(d,12H).

[0025] Sodium dihydrodi(3-tert-butyl-2-imidazolium-1-yl)borate (NaBm) tBu Synthesis of ) : Using a similar method, NaBH4 (567 mg, 15.0 mmol) and 1-tert-butyl-2-imidazolium thione (4.69 g, 30.0 mmol) were added to 80 mL of ultra-dry THF to obtain 4.21 g of white powder, with a yield of 81.0%. 1 H NMR (400MHz, DMSO-d6): δ6.97(d,2H), 6.75(d,2H), 1.70(s,18H).

[0026] Ce-Bm iPr Synthesis: Ce(OTf)3 (0.587 g, 1.00 mmol) was dispersed in 15 mL of THF, and then NaBm was slowly added dropwise to the suspension. iPr 15 mL of THF solution (0.954 g, 3.00 mmol) was added. The system gradually turned into a pale yellow solution, and stirring was continued at room temperature for 1 day. The solvent was then removed under vacuum, and the white residue was extracted with 25 mL of toluene and filtered to remove NaOTf. The solvent in the toluene filtrate was removed under reduced pressure to obtain a white powder. Yield: 485 mg (45.2%). Elemental analysis calculated C 36 H 60 B3CeN 12 S6+0.25C7H8(1071.94): C, 43.22%, H, 5.96%, N, 16.02%. Measured values: C, 43.67%, H, 6.11%, N, 15.71%.

[0027] Ce-Bm tBu Synthesis: using a method similar to Ce-Bm iPrThe synthesis method uses NaBm tBu (1.04 g, 3.00 mmol) was reacted with Ce(OTf)3 (587 mg, 1.00 mmol) to give 945 mg of a white powder, yield 78.6%. Elemental analysis calculated C 42 H 72 B3CeN 12 S6+C7H8(1202.16), C, 48.95%, H, 6.71%, N, 13.98%. Measured values: C, 48.56%, H, 6.67%, N, 13.79%.

[0028] Sodium trihydrotris(3-isopropyl-2-imidazolium-1-yl)borohydride (NaTm) iPr Synthesis of 3-Isopropyl-2-imidazolium ionone (3.56 g, 25.0 mmol) was prepared under a nitrogen atmosphere by mixing NaBH4 (303 mg, 8.0 mmol) and 3-isopropyl-2-imidazolium ionone (3.56 g, 25.0 mmol), followed by the addition of 50 mL of toluene. The mixture was stirred and heated at 135 °C for 2 days. After the reaction was complete, the mixture was cooled and filtered. The obtained solid was dissolved in DCM and filtered again. The filtrate was evaporated to dryness, and the resulting solid was washed with near-boiling toluene to obtain an almost white powder. Yield: 2.34 g (63.7%). 1 H NMR (400MHz, DMSO-d6): δ6.79(d,3H), 6.41(d,3H), 3.38(s,9H).

[0029] Sodium trihydrotris(3-tert-butyl-2-imidazolium-1-yl)borate (NaTm) tBu Synthesis of NaTm: using a method similar to NaTm iPr The synthetic method involves adding NaBH4 (378 mg, 10.0 mmol) and 1-tert-butyl-2-imidazolium thione (4.84 g, 31.0 mmol) to 50 mL of anhydrous toluene, yielding 2.88 g of a white powder with a yield of 57.5%. 1 HNMR (400MHz, DMSO-d6): δ6.83(d,3H),5.91(d,3H),1.72(s,27H).

[0030] Ce-Tm iPr Synthesis: Ce(OTf)3 (0.293 g, 0.500 mmol) was dispersed in 15 mL MeCN, and then NaTm was slowly added to the suspension. iPr A solution of (0.458 g, 1.00 mmol) in 15 mL of MeCN rapidly changed from colorless to bright yellow. The reaction mixture was stirred at room temperature for one day and then filtered. The solid was washed with THF (3 × 10 mL) to obtain a bright yellow powder. Yield: 360 mg (62.1%). Elemental analysis calculated C.37 H 56 B2CeN 12 S7O3F3(1160.09): C, 38.31%, H, 4.87%, N, 14.49%. Measured values: C, 38.42%, H, 4.64%, N, 14.36%.

[0031] Ce-Tm tBu Synthesis: using a method similar to Ce-Tm Me The synthesis method uses NaTm tBu (500 mg, 1.00 mmol) was reacted with Ce(OTf)3 (293 mg, 0.50 mmol) to give 324 mg of a yellow-green powder, yield 52.0%. Elemental analysis calculated C... 43 H 68 B2CeN 12 S7O3F3 (1244.25%), C, 41.51%, H, 5.51%, N, 13.51%. Measured values: C, 41.02%, H, 5.63%, N, 13.16%.

[0032] Eu-Tm iPr Synthesis: EuI2 (0.203 g, 0.500 mmol) was dissolved in 15 mL of THF, and then NaTm was slowly added to the solution. iPr A solution of (0.458 g, 1.00 mmol) in 15 mL of THF quickly turned bright yellow. The reaction mixture was stirred at room temperature for one day, then the solvent was removed under reduced pressure. The residual solid was extracted with 25 mL of DCM and filtered. The solvent in the orange filtrate was removed under reduced pressure. The residual solid was recrystallized from 25 mL of toluene to give a bright yellow powder. Yield: 171 mg (29.6%). Elemental analysis calculated C. 36 H 56 B2EuN 12 S6 + CH2Cl2 + 0.5C7H8 (1153.86%): C, 42.15%, H, 5.42%, N, 14.57%. Measured values: C, 41.59%, H, 5.05%, N, 14.32%.

[0033] Other substituents, such as methyl, ethyl, cyclohexyl, phenyl, or heterocyclic compounds with oxazole, thiazole, or coordinating atoms of oxygen, selenium, or tellurium, can be synthesized similarly.

[0034]

[0035] Example 2: Complex Ce-S2ip tBu Ce-Se2ip tBuWith Eu-S2ip tBu Synthesis

[0036] Preparation of the intermediate bis(di-tert-butylphosphine)imine ((tBu2P)2NH) toluene solution: NaNH2 (1.95 g, 50.0 mmol) was dispersed in 50 mL of THF and stirred. Then, tBu2PCl (9.00 g, 49.8 mmol) in 50 mL of THF solution was slowly added dropwise over approximately 30 min. The yellow turbid liquid was then heated at 60 °C for 3 h. After the reaction was complete, the system was cooled and the solvent was removed under reduced pressure. The resulting gelatinous white solid was dissolved in 50 mL of toluene and filtered to remove NaCl. The resulting yellow filtrate did not require further purification and could be used in the next step.

[0037] Synthesis of bis(di-tert-butylphosphine sulfide)imine ((tBu2PS)2NH): In a glove box, sublimed sulfur powder (1.60 g, 6.25 mmol) was added to a 25.0 mmol (tBu2P)2NH toluene solution. After the sulfur powder dissolved, the flask was sealed, removed from the glove box, and then connected to a condenser and a Schlenk line. The mixture was refluxed overnight at 130 °C under an argon atmosphere. After the reaction was complete, the solution was cooled and the solvent was removed under reduced pressure. The residue was dissolved in DCM and filtered to remove excess sulfur. The residue was then recrystallized from DCM and n-hexane to give a white crystalline powder. Yield: 5.11 g (55.3%). 1 H NMR (400MHz, CDCl3): δ3.21 (s, 1H), 1.47 (d, 36H).

[0038] Synthesis of bis(di-tert-butylphosphine selenide)imine ((tBu2PSe)2NH): A similar synthesis method to (tBu2PS)2NH was used, with the intermediate solution (24.9 mmol) refluxed overnight with selenium powder (3.95 g, 50.0 mmol). The solvent was then removed under reduced pressure, and the remaining yellow solid was recrystallized from DCM and n-hexane to give a white crystalline powder. Yield: 7.02 g, yield 60.9%. 1 H NMR (400MHz, CDCl3): δ3.34 (s, 1H), 1.50 (d, J = 16.0Hz, 36H).

[0039] Ce-S2ip tBuSynthesis: (tBu2PS)2NH (555 mg, 1.50 mmol) was mixed with NaH (36 mg, 1.50 mmol), and then 15 mL of THF was added to prepare the sodium ligand in situ. The sodium ligand was then added to a 15 mL THF suspension of Ce(OTf)3 (293 mg, 0.50 mmol), at which point the system changed from colorless to bright green. After stirring overnight at room temperature, the reaction system was filtered, and the solid was washed successively with MeCN and THF to obtain a light green powder. Yield: 378 mg (60.7%). Elemental analysis calculated C 48 H 108 N3P6S6Ce(1245.73): C, 46.28%, H, 8.74%, N, 3.37%. Measured values: C, 46.22%, H, 8.71%, N, 3.32%.

[0040] Ce-Se2ip tBu Synthesis: using a method similar to Ce-S2ip tBu The synthetic method used (tBu2PSe)2NH (695 mg, 1.50 mmol), NaH (36 mg, 1.50 mmol), and Ce(OTf)3 (293 mg, 0.50 mmol) were stirred overnight and then filtered to obtain 460 mg of a bright yellow powder, with a yield of 60.2%. Elemental analysis calculated C... 48 H 108 N3P6Se6Ce(1527.13), C, 37.75%, H, 7.13%, N, 2.75%. Measured values: C, 37.66%, H, 7.26%, N, 2.64%.

[0041] Eu-S2ip tBu Synthesis: (tBu2PS)2NH (365 mg, 1.50 mmol) was mixed with NaH (24 mg, 1.50 mmol), and then 15 mL of THF was added to prepare the sodium ligand in situ. The sodium ligand was then added to 15 mL of THF solution of EuI2 (203 mg, 0.50 mmol). After stirring overnight at room temperature, the solvent was removed under reduced pressure, and the residual solid was extracted with 25 mL of toluene. The resulting green filtrate was filtered to remove the solvent under reduced pressure, and the residual solid was recrystallized from THF-n-hexane to give a bright green powder. Yield: 259 mg (50.2%). Elemental analysis calculated C 40 H 88 N2P4S4O2Eu(1033.26): C, 46.50%, H, 8.58%, N, 2.71%. Measured values: C, 46.78%, H, 9.00%, N, 2.70%.

[0042] Eu-Se2ip tBuSynthesis: using a method similar to Eu-S2ip tBu The synthetic method used (tBu2PSe)2NH (463 mg, 1.00 mmol), NaH (24 mg, 1.00 mmol), and EuI2 (203 mg, 0.50 mmol) yielded 282 mg of a yellow powder, with a yield of 46.1%. Elemental analysis calculated C... 40 H 88 N₂P₄Se₄O₂Eu(1220.86): C, 39.35%, H, 7.27%, N, 2.30%. Measured values: C, 39.54%, H, 7.55%, N, 2.22%.

[0043] Complexes of Ce(III), Eu(II), Yb(II) and Sm(II) with other substituents such as methyl, ethyl, isopropyl, cyclohexyl, phenyl, or coordinating atoms such as oxygen, selenium, and tellurium can be synthesized similarly.

[0044]

[0045] Example 3: Complex Ce-ptp Ph,Me Synthesis

[0046] Synthesis of 4-methyl-2-diphenylphosphine-thiophenol: Under an argon atmosphere, a 1.6 M n-butyllithium solution in n-hexane (50 mL, 80 mmol) was slowly added dropwise to a mixed solution of tetramethylethylenediamine (12.0 mL, 80 mmol) and 4-methylphosphine (4.52 g, 36.4 mmol) over approximately 30–60 min. Initially, a large amount of white solid was formed in the system, which subsequently dissolved to form a yellow solution. The solution was stirred at room temperature for 22 h, after which a large amount of white powder precipitated. The reaction system was filtered, and the filter cake was washed with n-hexane to obtain a white lithium salt powder. Then, 30 mL of pre-cooled THF was added to the system, followed by the slow addition of 15 mL of diphenylphosphine chloride (5.20 g, 29.0 mmol) in THF solution at -78 °C over approximately 30 min. The system was then slowly brought back to room temperature and stirred overnight. The following day, the deep red system was quenched with a 10% sulfuric acid aqueous solution at 0°C, followed by extraction of the organic phase with DCM. The organic phases were combined and washed with saturated brine, then dehydrated with anhydrous sodium sulfate and filtered. The filtrate was evaporated to dryness to obtain an orange-yellow viscous solid, which was recrystallized from a mixed solution of diethyl ether and n-hexane to give 6.03 g (67.4%) of a nearly white crystalline powder. 1 H NMR (400MHz, CDCl3): δ7.41-7.20 (m, 11H), 7.03 (dd, J=7.9, 2.0Hz, 1H), 6.59 (dd, J=3.8, 2.0Hz, 1H), 2.15 (s, 3H).

[0047] Ce-ptp Ph,Me Synthesis: 4-Methyl-2-diphenylphosphinothiophenol (308 mg, 1.00 mmol) was dissolved in 20 mL of THF, and NaH (36 mg, 1.50 mmol) was added to the solution to prepare the ligand salt in situ. Powdered Ce(OTf)3 (293 mg, 0.50 mmol) was then added to the system and stirred; the solution gradually turned orange-yellow. The reaction mixture was stirred at room temperature for 1 day. The solvent was removed under reduced pressure, and the mixture was extracted with 15 mL of DCM and filtered to obtain an orange solution. The solution was concentrated to approximately 2 mL, and 15 mL of n-hexane was added. After stirring for 5 min, the mixture was filtered, and the filter cake was washed with n-hexane (3 × 5 mL) to obtain an orange powder. Yield: 242 mg (51.4%). Elemental analysis calculated C 114 H 96 P6S6Ce2+0.5CH2Cl2 (2166.92%), C, 63.46%, H, 4.51%. Measured value: C, 63.21%, H, 4.86%.

[0048] Other substituents, such as methyl, ethyl, isopropyl, tert-butyl, or aryl groups, or coordinating atoms, such as nitrogen, arsenic, oxygen, selenium, and tellurium, can be synthesized similarly for Ce(III), Eu(II), Yb(II), and Sm(II) complexes.

[0049]

[0050] Example 4: Complex Ce-dtu Cy4 With Ce-dtu iPr4 Synthesis

[0051] 1,1,5,5-Tetracyclohexyl dithiobiuret (Hdtu) Cy4 Synthesis of Cy2NC(S)Cl (3.90 g, 15.0 mmol), KSCN (1.46 g, 15.0 mmol), and 50 mL of MeCN were mixed and refluxed for 2 h. After cooling, the solution was filtered, and Cy2NH (3.62 g, 20.0 mmol) was added to the filtrate, immediately producing a white crystalline solid. The mixture was stirred overnight, and the turbid liquid was then filtered and washed with MeCN (3 × 15 mL) to give a pale yellow solid. Yield: 5.25 g (75.4%). 1 H NMR (400MHz, CDCl3): δ2.55(tt,4H), 1.95-1.54(m,16H), 1.48-0.90(m,24H).

[0052] 1,1,5,5-Tetraisopropyldithiobiuret (Hdtu) iPr4Synthesis of [a specific compound]: A similar synthetic method was used, employing iPr₂C(S)Cl (3.49 g, 20.0 mmol), KSCN (1.95 g, 20.0 mmol), and 50 mL MeCN. Diisopropylamine (4.05 g, 40.0 mmol) was then slowly added to the resulting yellow filtrate and stirred overnight, gradually precipitating a white crystalline solid. The next day, the reaction system was filtered, and the solid was washed with MeCN (3 × 5 mL) to obtain a nearly white crystalline powder. Further concentration of the filtrate yielded more product, ultimately yielding 4.99 g of a white crystalline solid, with a yield of 82.1%. 1 H NMR (400MHz, CDCl3): δ2.92 (hept, J=6.3Hz, 4H), 1.05 (d, J=6.2Hz, 24H).

[0053] Ce-dtu Cy4 Synthesis of Hdtu Cy4 (696 mg, 1.50 mmol) was mixed with NaH (36 mg, 1.50 mmol), and then 15 mL of THF was added to prepare the sodium ligand in situ. The sodium ligand was then added to a 15 mL THF suspension of Ce(OTf)3 (293 mg, 0.50 mmol), at which point the system changed from colorless to orange-red. After stirring overnight at room temperature, the solvent was removed under reduced pressure, and the residual solid was extracted with 25 mL of toluene. The mixture was filtered to obtain a ruby-red solution. After removing the toluene under reduced pressure, 20 mL of n-hexane was added, and the mixture was filtered. The filtered solid was washed with n-hexane (3 × 15 mL) to obtain a magenta powder. Yield: 475 mg (60.5%). Elemental analysis calculated C 78 H 132 N9S6Ce+0.5CH2Cl2(1570.91): C, 60.01%, H, 8.53%, N, 8.03%. Measured values: C, 60.25%, H, 8.74%, N, 7.49%.

[0054] Ce-dtu iPr4 Synthesis: Using a similar method, Hdtu iPr4 (910 mg, 3.00 mmol), NaH (72 mg, 3.00 mmol), and Ce(OTf)₃ (587 mg, 1.00 mmol) were used to collect 312 mg of a pink powder, with a yield of 29.8%. Elemental analysis calculated C 42 H 84 N9S6Ce (1047.69%), C, 48.15%, H, 8.08%, N, 12.04%. Measured values: C, 48.26%, H, 8.07%, N, 11.90%.

[0055] Other substituents such as methyl, ethyl, phenyl, substituted or unsubstituted piperidine, morpholine groups or coordinating atoms such as oxygen, selenium, tellurium Ce(III), Eu(II), Yb(II) and Sm(II) complexes can be synthesized similarly.

[0056]

[0057] Crystal structure of the complex in Example 5

[0058] Table 1. Typical coordination compounds Ce-Bm iPr Ce-Tm iPr Eu-S2ip tBu Ce-S2ip tBu With Ce-dtu Cy4 Crystal data sheet

[0059]

[0060]

[0061] The molecular structures of the illustrated complexes were characterized by single-crystal X-ray diffraction, among which Ce-Bm iPr With Ce-Tm iPr Ce-ptp forms nine-coordinate, three-capped triangular prism and eight-coordinate, two-capped anti-triangular prism structures respectively, from the S and BH ligands. Ph,Me It exhibits an asymmetric, binuclear, triple-bridged structure (the two Ce centers form heptagonal and octagonal structures, respectively), while the other three complexes all form hexagonal, twisted triangular prism configurations. Furthermore, Eu-S2ip... tBu Eu coordinates with two ligands, while the remaining two sites are occupied by the solvent THF. Meanwhile, in these Ce(III) complexes, the average Ce-S bond lengths are... and As the electronegativity of the S coordination sites on the ligands increases, the Ce-S bond length shows a significant decreasing trend, indicating that the covalent nature of the bonding at the S coordination sites gradually increases in this series of complexes, resulting in a gradually increasing Ce(III)5d centroid shift. Combined with the modulation of the 5d lowest energy level by ligand field splitting, the df transition energy of the complexes decreases accordingly.

[0062] Photophysical properties of the complex in Example 6

[0063] The structure of the complex is shown below:

[0064]

[0065] The luminescence of Eu(II) complexes in different S and Se coordination systems can be modulated from green light to near-infrared emission, with a luminescence quantum yield (PLQY) of up to 75%. The luminescence of Ce(III) complexes in different systems can span the visible region and shift to the near-infrared region. The test results for these representative complexes are shown in the table below:

[0066]

[0067] Among them, Ce-Bm R In this complex, the ligands have a relatively small number of chelating teeth and relatively weak coordination ability. The complexes all exhibit blue to blue-green light emission, with emission peaks between 450-480 nm, and a PLQY of up to 86%. When the inventors replaced the alkyl substituents, the emission of the complexes did not change significantly. With increasing chelating teeth, Ce-Tm... R The emission further redshifts into the yellow-green region, with the emission peak located at approximately 520 nm. The introduction of the rigid framework also allows the highest PLQY to reach 97%. When the substituent is replaced by tert-butyl, the maximum emission only redshifts from 518 nm to 520 nm. This is because the steric hindrance effect of the peripheral substituent is small and does not significantly affect the Ce-S bond in the inner sphere of the coordination. Similarly, for the double-S chelate ligand, when using P=S coordination, the emission of the complex will redshift further, Ce-S2ip R The series of complexes exhibit emission peaks in the 460-500 nm range. The steric hindrance provided by the disubstituted phosphine effectively protects the central ion, achieving high luminescence efficiency (PLQY ~100%) and good air stability (no significant PLQY decay after 3 months in air). Furthermore, by replacing the coordinating atoms with softer Se and Te, the combined effect of electron cloud effect and ligand field splitting results in Ce-Se2ip... tBu With Ce-Te2ip tBu The emission peaks were further redshifted to 520 nm and 610 nm. By introducing P and S coordination sites into the ligand, the complex Ce-ptp... Ph,Me The emission peak shifts to the red region, with maximum emission at 650 nm, where PLQY reaches 73%. When the benzene ring or the substituent attached to the P atom is replaced by an alkyl group, the maximum emission of the complex is located at 620-650 nm, and PLQY exceeds 70%. Furthermore, when using dithiobiuret ligands, the electron-donating effect of the amino group further enhances the coordination ability of the S coordination site, resulting in a further shortening of the Ce-S bond length, an increased centroid shift, and a Ce-dtu complex. Cy4 The emission peak shifts to the near-infrared region (725 nm). When the substituent is replaced by isopropyl instead of cyclohexyl, the maximum emission remains unchanged, with only a slight decrease in PLQY. Meanwhile, Ce-dtu... Cy4The PLQY can still reach 31%, which is among the highest in near-infrared emission of the df transition.

[0068] The excited-state lifetimes of these Ce(III) complexes are tens of nanoseconds, which is closely related to their spin-allowed doublet transitions. Furthermore, as the coordinating atoms become heavier or the emission of the complex redshifts, the excited-state lifetimes gradually increase, indicating a lower radiative transition rate under long-wavelength emission.

[0069] To characterize the air stability of the complex, the inventors exposed the complex to air and monitored the change in its PLQY over exposure time to measure its stability in air. Ce-S2ip tBu It exhibits remarkably good stability in air: initially, the sample's PLQY was 74% due to solvent molecule adsorption in the glove box, slightly lower than the freshly prepared sample (100%). To confirm this hypothesis, the sample was further vacuum-dried before testing, at which point the PLQY returned to 100%. Ce-Se2ip... tBu Due to the relatively unstable P=Se bond, PLQY gradually decreases with increasing test time. Furthermore, although the Ce-O bond is relatively stable, Ce-O2ip, as a typical "hard acid-hard base" combination... tBu The PLQY also gradually decreased, indicating that in addition to N coordination, S coordination is also a good choice for constructing air-stable complexes.

[0070] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. Regarding the synthesis section, appropriately replacing the reactants can yield compounds not given in the embodiments. Regarding the spectral section, considering that the emission of the complex is mainly related to the coordinating atoms, it can be expected that replacing the outer substituents in the embodiments will not significantly affect the inner coordination space due to steric hindrance, and therefore will not lead to a significant change in luminescence performance. As for the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant details can be found in the method section.

[0071] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A df transition rare earth complex, characterized in that, The df transition rare earth complex has any of the following structures: Among them, R 1 R 2 It is independently selected from any one of hydrogen, unsubstituted C1-C18 alkyl, substituted C1-C18 alkyl, alkoxy, C1-C18 alkoxy, unsubstituted C1-C18 alkenyl, halogen-substituted C1-C18 alkenyl, unsubstituted C1-C18 alkynyl, halogen-substituted C1-C18 alkynyl, unsubstituted aryl within C50, substituted aryl within C50, C1-C18 alkyl or heterocyclic containing O, N, or S coordination sites; X is O, S, or NR, where R is any one of the following: unsubstituted C1-C18 alkyl, substituted C1-C18 alkyl, C1-C18 alkoxy, unsubstituted C1-C18 alkenyl, halogenated C1-C18 alkenyl, unsubstituted C1-C18 alkynyl, halogenated C1-C18 alkynyl, unsubstituted aryl (within C50), substituted aryl (within C50), C1-C18 alkyl or heterocyclic containing O, N, or S coordination sites. Sol is an organic solvent molecule with monodentate or polydentate coordination; Y is a negatively charged ion; E and E' are coordinating atoms, independently selected from O, S, Se or Te; Pc is a coordinated group VA atom, independently selected from N, P or As; A is an alkali metal ion with a countercharge, independently selected from Li, Na, K, Rb, or Cs; M is selected from Ce(III), Pr(III), Tb(III), Eu(II), Yb(II), Sm(II) or Tm(II).

2. The df transition rare earth complex according to claim 1, characterized in that, Sol is selected from at least one of acetonitrile, tetrahydrothiophene, tetrahydrofuran, diethyl ether, isopropyl ether, pyridine, ethylenediamine, and ethylene glycol dimethyl ether.

3. The df transition rare earth complex according to claim 1, characterized in that, Y is selected from at least one of F, Cl, Br, I, SCN and CF3SO3.

4. The df transition rare earth complex according to claim 1, characterized in that, R 1 R 2 R is independently selected from any one of methyl, ethyl, isopropyl, tert-butyl, cyclohexyl, and phenyl.

5. The application of the df transition rare earth complex according to any one of claims 1-4 as a phosphor.

6. The application of the df transition rare earth complex according to any one of claims 1-4 as a photoluminescent material.

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