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).
