Synthesis, Structure and Photophysical Properties of Dinuclear Zinc(II) Complexes with Schiff Base Bearing p–Phenylenediamine
摘要
Four new dinuclear complexes Zn1-Zn4 were synthesized by the interaction of Zn(NO3)2.4H2O with Schiff bases containing p-phenylenediamine. The data of ESI–MS, IR and 1H NMR spectroscopy showed that the ligands coordinated with Zn(II) via two sets of O, Nimine atoms. In DMSO, ligands exhibit weak luminescence while the complex solutions emit strongly at maximum wavelength in the range 409-513 nm. Notably, electron-donating groups enhance the quantum yield of the complex solutions. Particularly, Zn2 containing NEt2 substitutes has outstanding quantum yields of 74%. Besides, the lifetimes of the complexes increase in the order Zn2 < Zn4 < Zn1 < Zn3 in DMSO. Along with the experiment, the structure, absorption and emission spectra of Zn1-Zn4 have been investigated by TD-DFT calculation. The result reproduces well the experimental absorption wavelengths and shows that the absorptions of the complexes are due to the singlet S0 → S1* transition from the π to the π* orbital of the ligand in complexes and the emission occurs from minimum of the S1 state to the ground singlet state S0. The calculation results also support for the fact that Zn2 has profoundly quantum yields.