Density Functional Study of Molecular Orbitals of Ferrocene and Cobaltocene Molecules

The electronic structure and geometry optimization of ferrocene and cobaltocene molecules are calculated using DFT/B3LYP with the basis set of 6-31G (d). The Eigen values, Eigen vector and population analysis of the molecules show that the first 13 molecular orbitals in ferrocene and 12 in cobaltocene have contribution from 2pz orbitals of carbon of (C5H5)- and 4s, 4p and 3d orbitals of iron and cobalt respectively. We found that the extent of involvement of metal orbitals in the two cases is different. In ferrocene the maximum involvement out of 4s and 4p orbital is in the order 4pz>4py>4s>4px and out of 3d orbitals the order of involvement is 3dyz>3dxz>3d2z>3dx2-y2>3dxy. The involvement of corresponding orbital in cobaltocene with respect to the 4s and 4p orbitals is in the order of 4s>4pz>4py>4px and in 3d orbitals the order is 3dx2-y2>3dxz>3d2z>3dx2-y2 and 4py>4px>4s>4pz molecules. The total involvement of 3d, 4s and 4porbitals of metal and 2pz orbitals of the ten carbon atoms of both ligands of (C5H5)- in ferrocene and cobaltocene respectively are 42.2528 and 40.2388 hence we can conclude that ferrocene is more stable than cobaltocene. Similar results are found from calculation of parameters like dipole moment, HOMO-LUMO gap and Mullikan charge distribution. The population analysis shows that only 2pz orbitals of carbon of (C5H5)- and 3d orbitals of metal provide electrons to MOs of ferrocene and cobaltocene.