Theoretical studies on the electronic structure and spectroscopic properties of zinc(II) bis(dipyrrinate)s

Geometric characteristics using density functional theory (three-parameter hybrid functional B3LYP) and the basis set 6–31G(d,p) were obtained, NBO analysis (CAM-B3LYP/6-31G) was performed, energy values of the electronic transitions from the general to the nearest electronic states, oscillator strength values and corresponding wavelength values (TD-DFT/B3LYP/cc-pVTZ) were calculated for the homoleptic binuclear zinc(II) helicates with decamethylsubstituted 2,2′-, 2,3′- or 3,3′-bis(dipyrrin) ligands ([Zn2L2]). The effect of changes in the geometry of the electronically excited state of the luminophores on their kinetic and thermal stability was considered. The interpretation of dependence between spectral-luminescent properties of complexes and HOMO and LUMO energy gap’s width was done. It was shown that regularities obtained from the results of quantum chemical calculations of [Zn2L2] helicates molecular structures reliably reflects experimentally founded trends of changing the quantum yield depending on the structure of chelating ligands. Thus, based on the results of a comprehensive theoretical study can be validly assessed the fluorescent ability of new structurally modified [Zn2L2] helicates and prospectivity of their use as a fluorescent dyes for optical devices.