Geometry Optimization and Excited States of Tris(2,2'-bipyridine)ruthenium(ll) Using Density Functional Theory

Abstract

During the last two decades, many investigations have been performed on molecules belonging to the family of tris(2,2'-bipyridine)ruthenium(II). In this work, a theoretical approach of the [Ru(bpy)₃]²⁺ complex using Density Functional Theory and in particular the Amsterdam Density Functional (ADF) program package, is presented. The geometry of the [Ru(bpy)₃]²⁺ complex has been optimized using the local density approximation (LDA). The optimization has been made within D₃ symmetry and it leads to good agreement with the X-ray structure. As the photochemical and photophysical data suggest, two sets of low-lying empty molecular orbitals are found. In a first study, we dealt with the first set of levels, which correspond to Metal-to-Ligand Charge- Transfer states (MLCT), and calculated the positions of these MLCT states as well as the intensities of the transitions, using the Generalized Gradient Approximations (GGA). The results obtained are in good agreement with the experiment. In a second part, we focus on the upper set of unoccupied orbitals, which are metal-centered. Thus, we calculated the energy of the transition corresponding to the Lowest Ligand Field state, which has been suggested to be responsible for the photoracemization and photosubstitution.