[Crystal structures and luminescence property of d10 transition metal complexes]

Five Zn( [II)) and Cd(II) coordination complexes, [Zn(NA)2 (H2O)4](1), [Zn(INA)2 (H2O)4](2), [Zn(2,2'-bi-py)2 (SCN)2](3), [Cd(INA)2 (H2O)4](4) and [Cd(phen)2(NO3)](5) (HNA=nicotinic acid, HINA=isonicotinic acid, 2, 2'-bipy=2,2'-bipyridine, phen=1,10-phenanthroline), were synthesized through constant temperature magnetic stirrer or hydrothermal method, and their single-crystal structures were determined by X-ray diffraction. The authors measured the IR, UV-Vis-NIR and fluorescence spectra of the complexes and analyzed their photophysical properties. At room temperature in the solid state the five complexes can show strong fluorescence, i.e., lamdamax(em)=362 nm (lamda(ex)=330 nm), (1); lamdamax(em)=424 nm (lamda(ex)=330 nm), (2); lamdamax(em)=442 nm (lamda(ex)=380 nm), (3); lamdamax(em)=424 nm (lamda(ex)=330 nm), (4); lamda(em max)=456 nm (lamda(ex)=360 nm), (5), and complex (5) can emit phosphorescence upon excitation at 360 nm (lamdamax (pl)=546 nm, tau=10 ms). But the organic ligands are different, which lead to the luminescence property of complexes originating from different charge transfer. Compared with the relevant ligands (lamdamax (em)=380 nm, HNA; lamda(em max)=541 nm, 2,2'-bipy), the fluorescence emissions of complex (1) and (3) show a blue-shift which mainly comes from the ILCT (intraligand charge transfer) and at the same time exists L-->M(4S) transfer. The emissions of complex (2) and (4) come from LMCT (ligand-to-metal charge transfer) and show red-shift compared to that of free ligand (lamdamax(em)=337 nm, HINA). For complex (5), the appearance and position of its emission are different from those of the ligand (lamdamax(em)=381 nm, phen), which is attributed to LLCT (ligand-to-ligand charge transfer) and LMCT.