Theoretical study on photophysical property of cuprous bis-phenanthroline coordination complexes

The electronic structures and photophysical properties of phenathroline ligands coordinated to Cu(I), which are substituted in the 2,9-positions with methyl, phenyl, trifluoromethyl and tert-butyl groups, has been studied by density functional theory (DFT) and time-dependent DFT (TDDFT). To investigate the role played by counteranion in these complexes, the highest occupied orbital energies (HOMO), the lowest virtual orbital energies (LUMO), Delta(H-L) (the energies difference between the HOMO and LUMO), the lowest excitation energies (E-S1), ionization potentials (IPs), electron affinities (EAs) and reorganization energies (lambda) were computed. And through the study of the geometric relaxations, d-orbital splitting and spin-orbit couplings (SOC) at their optimized So and T-1 geometries, non-radiative and radiative decay rate constants (k(nr) and k(r)) were determined, for comparing and analyzing the different size and push/pull substituents effect on the luminescence quantum yield. Considering these factors, the dtbpdmp complex with tert-butyl group in the 2,9-positions has faster k(r) and singlet-triplet intersystem crossing (ISC) but slower k(nr), which leads to its higher photoluminescent quantum efficiency as compared to the methyl-, phenyl- and trifiuoromethyl-based complexes. (C) 2012 Elsevier B.V. All rights reserved