The development of polymeric materials that exhibit blue thermally activated delayed fluorescence(TADF)is of great interest for optoelectronic applications.However,achieving TADF in polymers often requires an elaborat...The development of polymeric materials that exhibit blue thermally activated delayed fluorescence(TADF)is of great interest for optoelectronic applications.However,achieving TADF in polymers often requires an elaborate monomer design.The high-energy local triplet state(^(3)LE)of carbazole complicates its application despite the molecular orbital arrangement being suitable for blue emission.Here,we present an approach to polymer design that makes it possible to solve this problem.We demonstrate the in situ formation of a TADF donor-acceptor system during Suzuki polycondensation,creating an extended carbazole-based donor matrix coupled with a triazine acceptor.The resulting polymer exhibited efficient TADF with a low energy gap(ΔE_(ST))value if a phenyl N-substituent,enabling essential electron delocalization,was present in the carbazole moiety.This work establishes a versatile platform for developing carbazole-based TADF polymers,overcoming the fundamental limitations that hinder their widespread application.展开更多
New complexes of europium,gadolinium and terbium trinitrates with N,N,N’,N’-tetraalkyl substituted phenanthroline diamides were synthesized.The europium complexes were found to be highly efficient in terms of lumine...New complexes of europium,gadolinium and terbium trinitrates with N,N,N’,N’-tetraalkyl substituted phenanthroline diamides were synthesized.The europium complexes were found to be highly efficient in terms of luminescence properties(max quantum yield=67%).The significant influence of the structure of the ligands on the photophysical characteristics of their complexes was demonstrated.Thus,the incorporation of various substituents(Cl,F,O,OH)into the phenanthroline core causes significant changes in the luminescent behavior of the obtained coordination compounds.We observed significant differences in the energy gap between the excited states S_(1)and T_(1),especially in the L2H.Eu(NO_(3))_(3)and L2FOH.Eu(NO_(3))_(3)complexes,which both demonstrated high overall quantum yields(66%and 67%,respectively).Study of the diffuse reflection spectra of terbium complexes suggested the phenomenon of charge transfer,potentially ligand-to-ligand(LLCT)or intra-ligand(ILCT),rather than ligand-to-metal charge transfer(LMCT).These results highlight the complicated relationship between ligand structure,energy transfer mechanisms and quantum yield in rare earth element complexes,shedding light on ways to optimize their luminescent properties.展开更多
The reaction of 4-nitro-N'-(pyridin-2-ylmethylene)benzohydrazide(HL) with Ln(OAc)_(3)·4H_(2)O in MeOH makes it possible to synthesize mononuclear complexes [Ln(L)_(2)(OAc)(MeOH)]·2H_(2)O(Ln=Tb^(Ⅲ)(1),E...The reaction of 4-nitro-N'-(pyridin-2-ylmethylene)benzohydrazide(HL) with Ln(OAc)_(3)·4H_(2)O in MeOH makes it possible to synthesize mononuclear complexes [Ln(L)_(2)(OAc)(MeOH)]·2H_(2)O(Ln=Tb^(Ⅲ)(1),Eu^(Ⅲ)(2) and Gd^(Ⅲ)(3)) with chelate acetate and L^(-)anions.Compound 1 can be crystallized in reaction with molar ratio HL:Ln=1:1,2:1,3:1,and we successfully synthesized complex with three chelate L anions[Tb(L)_(3)]_(2)·2MeOH·H_(2)O(4) by interaction of TbCl_(3)·6H_(2)O with deprotonated HL(HL:Ln=3:1).Terbium(Ⅲ) compound 1 starts to decompose at~323 K and becomes stable up to 552 K according to the STA.Compound 1 shows slow magnetic relaxation with parameters Δ_(eff)/k_B=(6.75±0.02) K,τ_(0)=(1.71 × 10^(-6)±1 × 10^(-8)) s.Complexes 1 and 2 exhibit only fluorescence and phosphorescence of the L^(-).Ion-centered luminescence of the Tb^(3+)or Eu^(3+)ion is not observed.Using the tangent method at the high-energy edge of the phospho rescence spectrum of Gd^(3+),complex 3 T_(1) energy level of L^(-)is estimated to be 19700 cm^(-1).Reasons of luminescence quenching are discussed.Structures of 1 and 4 were determined by single crystal X-ray diffraction,and compounds 1-3 were characterized by powder X-ray diffraction(PXRD).展开更多
基金supported by the Russian Science Foundation (No. 25-13-00300)the Centre for Optical and Laser Materials Research (SPbSU) and Saint Petersburg State University for measuring the quantum yields of luminescence within the framework of research project(No.125021902439-8)。
文摘The development of polymeric materials that exhibit blue thermally activated delayed fluorescence(TADF)is of great interest for optoelectronic applications.However,achieving TADF in polymers often requires an elaborate monomer design.The high-energy local triplet state(^(3)LE)of carbazole complicates its application despite the molecular orbital arrangement being suitable for blue emission.Here,we present an approach to polymer design that makes it possible to solve this problem.We demonstrate the in situ formation of a TADF donor-acceptor system during Suzuki polycondensation,creating an extended carbazole-based donor matrix coupled with a triazine acceptor.The resulting polymer exhibited efficient TADF with a low energy gap(ΔE_(ST))value if a phenyl N-substituent,enabling essential electron delocalization,was present in the carbazole moiety.This work establishes a versatile platform for developing carbazole-based TADF polymers,overcoming the fundamental limitations that hinder their widespread application.
基金support from M.V.Lomonosov Moscow State University Program of Development。
文摘New complexes of europium,gadolinium and terbium trinitrates with N,N,N’,N’-tetraalkyl substituted phenanthroline diamides were synthesized.The europium complexes were found to be highly efficient in terms of luminescence properties(max quantum yield=67%).The significant influence of the structure of the ligands on the photophysical characteristics of their complexes was demonstrated.Thus,the incorporation of various substituents(Cl,F,O,OH)into the phenanthroline core causes significant changes in the luminescent behavior of the obtained coordination compounds.We observed significant differences in the energy gap between the excited states S_(1)and T_(1),especially in the L2H.Eu(NO_(3))_(3)and L2FOH.Eu(NO_(3))_(3)complexes,which both demonstrated high overall quantum yields(66%and 67%,respectively).Study of the diffuse reflection spectra of terbium complexes suggested the phenomenon of charge transfer,potentially ligand-to-ligand(LLCT)or intra-ligand(ILCT),rather than ligand-to-metal charge transfer(LMCT).These results highlight the complicated relationship between ligand structure,energy transfer mechanisms and quantum yield in rare earth element complexes,shedding light on ways to optimize their luminescent properties.
基金supported by the Russian Science Foundation (2273-10199)。
文摘The reaction of 4-nitro-N'-(pyridin-2-ylmethylene)benzohydrazide(HL) with Ln(OAc)_(3)·4H_(2)O in MeOH makes it possible to synthesize mononuclear complexes [Ln(L)_(2)(OAc)(MeOH)]·2H_(2)O(Ln=Tb^(Ⅲ)(1),Eu^(Ⅲ)(2) and Gd^(Ⅲ)(3)) with chelate acetate and L^(-)anions.Compound 1 can be crystallized in reaction with molar ratio HL:Ln=1:1,2:1,3:1,and we successfully synthesized complex with three chelate L anions[Tb(L)_(3)]_(2)·2MeOH·H_(2)O(4) by interaction of TbCl_(3)·6H_(2)O with deprotonated HL(HL:Ln=3:1).Terbium(Ⅲ) compound 1 starts to decompose at~323 K and becomes stable up to 552 K according to the STA.Compound 1 shows slow magnetic relaxation with parameters Δ_(eff)/k_B=(6.75±0.02) K,τ_(0)=(1.71 × 10^(-6)±1 × 10^(-8)) s.Complexes 1 and 2 exhibit only fluorescence and phosphorescence of the L^(-).Ion-centered luminescence of the Tb^(3+)or Eu^(3+)ion is not observed.Using the tangent method at the high-energy edge of the phospho rescence spectrum of Gd^(3+),complex 3 T_(1) energy level of L^(-)is estimated to be 19700 cm^(-1).Reasons of luminescence quenching are discussed.Structures of 1 and 4 were determined by single crystal X-ray diffraction,and compounds 1-3 were characterized by powder X-ray diffraction(PXRD).
