GEOMETRY OPTIMIZATION AND EXCITED-STATES OF TRIS(2,2-BIPYRIDINE)RUTHENIUM(II) USING DENSITY-FUNCTIONAL THEORY

During the last two decades, many investigations have been performed o n molecules belonging to the family of tris(2,2'-bipyridine)ruthenium( II). In this work, a theoretical approach of the [Ru(bpy)(3)](2+) comp lex using Density Functional Theory and in particular the Amsterdam De nsity Functional (ADF) program package, is presented. The geometry of the [Ru(bpy)(3)](2+) complex has been optimized using the local densit y approximation (LDA). The optimization has been made within D-3 symme try and it leads to good agreement with the X-ray structure. As the ph otochemical and photophysical data suggest, two sets of low-lying empt y molecular orbitals are found. In a first study, we dealt with the fi rst set of levels, which correspond to Metal-to-Ligand Charge-Transfer states (MLCT), and calculated the positions of these MLCT states as w ell as the intensities of the transitions, using the Generalized Gradi ent Approximations (GGA). The results obtained are in good agreement w ith the experiment. In a second part, we focus on the upper set of uno ccupied orbitals, which are metal-centered. Thus, we calculated the en ergy of the transition corresponding to the Lowest Ligand Field state, which has been suggested to be responsible for the photoracemization and photosubstitution.