Luminescence spectral analysis for Eu(III), and the dinuclear (Zn(II), Cu(II)) complexes with organic ligands by quantum chemical methods

Abstract

We are very interested in elucidating the theoretical reason why the luminescence of Eu(III)-organo-ligand complexes is enhanced in the presence of Zn(II)-Schiff base complexes, or quenched in the addition of Cu(II) ones. The reason for luminescence enhanced and quenching spectra is deduced from the dynamic (time-dependent) and static (time-independent) standpoints. In the dynamic behavior, we describe that such luminescence spectra depend upon the lifetimes of electron populations at the excited state for their metal-complexes by considering experimental investigations of Eu(III), Zn(II), Cu(II), and dinuclear Eu(III)-(Zn(II), or Cu(II)) complexes with organo-ligands. We also consider the chemical rate equations to form the dinuclear metal complexes, and derive the new equation for the ratio of quantum yields to estimate lifetimes of the Zn(II)- and Cu(II)-saltn complexes. From the static viewpoint, electronic states of septet Eu(III) (as an electron donor), singlet Zn(II) {(or doublet Cu(II)) as an electron acceptor}, and the dinucleus septet Eu(III)⋅Zn(II) (or octet Eu(III)⋅Cu(II)) complexes with organo-ligands are calculated by using DFT and TD-DFT methods. We discuss that the simulated UV–Vis spectra in the range of 450–700 nm reflect to the enhanced Eu(III)⋅Zn(II) and quenching Eu(III)⋅Cu(II) peaks with the experimental ones.