This thesis will be divided in two parts, each of them will talk about coordination chemistry of heavy atoms. The first part concerns the study of lanthanides and actinides hydration using molecular dynamics and ab initio calculations. Hydration properties such as coordination number of water molecules around cations and distances between cations and oxygen water molecules are extracted from our calculation and compared to previous results obtained experimentally and theoretically. The approaches use to generate pair potential for lanthanides are reported. A methodology to build accurate force field will also be discussed. In the second part, some organic ligands designed by our collaborators to complex trivalent lanthanide cation into a dinuclear luminescent compound are studied. Our collaborators show that the quantum yield of these complexes is affected by the excitation transition of the ligands. That is why we perform a density functional theory study of HOMO and LUMO of these ligands. We are interested to their localization on the ligands and the HOMO-LUMO energy gap. Then we studied the effect of electronic modification of the ligand by functionalizing the ligands with electronwithdrawing and electron donating groups on these energies. The structural conformations of the ligands are also treated. From our results, our experimentalist collaborators get ideas for the strategy to design new ligands in order to form luminescent dinuclear lanthanide complexes.