This work is focused on the theoretical study of photophysical properties of ruthenium polypyridyl complexes using DFT and TDDFT calculations. The first part is an introduction of the photophysical and electrochemical properties usually encountered for such systems. We also stress how each type of ligand can interplay with the metal fragment and modify the photophysical properties. In the second section, we present how we employed DFT, TDDFT, NBO analysis and Orca_asa program for our study. The third and fourth chapters are centered on [Ru(tpy)(bpy)L]n+ and [Ru(bpy)2L2]n+ complexes where L is a phosphorus ligand of L, L+ or L- type. Beyond thermodynamic considerations, we highlight the importance to consider and determine the kinetic properties to well understand the experimentally observed luminescence. In the next part, we modelize electrochemical and photophysical properties of two [Ru(bpy)2(LL')]2+ complexes where LL' is a nitrogen ligand which plays the role of electron acceptor in the formation of the 3MLCT state. The last chapter concerns the influence exerted by successive protonation of [Ru(bpy)(CN)4]2- and Ru(bpy)2(CN)2 complexes on the relative positions of 3MLCT, 3LC and 3MC states and hence on the observed emissive properties in acidic media.
