Photo-luminescent hetero-trinuclear Zn2Ln (Ln = Nd, Yb, Er or Gd) complexes based on the binuclear Zn2L precursor
文摘
With the binuclear Zn2L ([Zn2L(OAc)2(H2O)], 1) compound from the Salen-type Schiff-base ligand H2L (H2L: N,N¡ä-bis(salicylidene)cyclohexane-1,2-diamine) with the flexible linker as the precursor, a series of hetero-trinuclear Zn2Ln complexes (Ln = Nd (2), Ln = Yb (3), Ln = Er (4) or Ln = Gd (5)) have been obtained by further reaction with Ln(OAc)3¡¤6H2O. The result of their photophysical properties shows that the strong and characteristic NIR luminescence with emissive lifetimes in the ranges of microseconds for each of the complexes 2-4, has been sensitized from the excited state (1LC and 3LC) of the Salen-type Schiff-base ligand with the flexible linker. Especially, the almost planar arrangement of two energy donors of ZnL components around the Ln3 + ion for the larger conjugation effect, endowing the energy level's good match between the excited state (3LC) of the chromophore to the corresponding Ln3 + ion's exciting state, results in the enhancement of their NIR luminescence.