Structure and spectral and luminescence properties of the trinuclear zinc complex with (E)-5-((2,6-diethylphenylimino)methyl)-2-methylquinolin-8-ol: Experimental and DFT study

Abstract

Quantum chemical optimization of the equilibrium structure of the trinuclear zinc complex with (E)-5-((2,6-diethylphenylimino)methyl)-2-methylquinolin-8-ol at the density functional theory level followed by Bader analysis of the electron density distribution function was performed on the basis of X-ray diffraction data for the molecular crystals of the complex. Interpretation of the topological parameters of electron density in the critical points of the Zn–O and Zn–N coordination bonds was carried out and the energies of these bonds were estimated using the Espinosa formula. Calculations in terms of the non-stationary density functional theory were used to simulate the absorption spectra of the complex and the structure-forming quinoline ligand. The S ₀ → S ₁ transition subsequently responsible for generation of fluorescence is practically forbidden in the spectrum of the quinoline ligand and becomes allowed in the spectrum of the complex, which is observed experimentally as a fivefold enhancement of the quantum yield of fluorescence of the complex as compared with the ligand.