Electronic Structure and Related Properties of DNA-Molecular Light-Switch Complex [Ru(bpy)2(bopp)]2+

Abstract

The electronic structure and related properties of a novel DNA-molecular light-switch complex [Ru(bpy)₂(bopp)]²⁺ (bpy = 2,2'-bipyridine; bopp = 2-benzoxazolyl-pyrazino[2,3-f][1,10]phenanthroline) (1) has been investigated applying DFT/TDDFT (density functional theory and time-dependent DFT) methods. The comparison with well-accepted DNA-molecular light-switch complex [Ru(bpy)₂(dppz)]²⁺ (dppz = dipyrido-[3,2-a:2',3'-c]phenazine) (2), the important geometric and electronic structural characteristics of complex 1 which can be expected to be an excellent DNA-molecular light-switch complex, were theoretically revealed. Moreover, it is further shown that such geometric and electronic structural characteristics can be obtained via introducing some heteroatoms (N and O atoms) with stronger electronegativity into the ring skeleton of main ligand. In particular, the ¹MLCT spectra of complex 1 in aqueous solution were calculated and simulated by the TDDFT method in a satisfying agreement with experimental results. Based on the electric structure, the experimental three main UV-visible bands (~448, ~363 and ~284 nm) were theoretically explained in detail and some regularities regarding strong absorption spectral bands were also presented. These theoretical results help to designing novel DNA-molecular light-switch complexes and understanding the spectral properties.