Ab initio Study of the Geometrical and Electronic Structures of Sc(MDA)2 and Sc(MDA)3 Molecules

Abstract

The geometrical parameters, force fields, and vibrational spectra of various geometrical configurations of Sc(MDA)2 and Sc(MDA)3 molecules were calculated using the restricted Hartree—Fock method taking into account electron correlation by second–order Moller–Plesset perturbation theory. The calculations were performed using effective pseudopotentials for describing atomic cores and valence double zeta basis sets supplemented by polarization functions. It was shown that the configurations of D 3 [Sc(MDA)3] and D 2h [Sc(MDA)2] symmetry correspond to the minimum on the potential energy surface of the ground electronic state. The configurations of D 3h symmetry for Sc(MDA)3 and D 2d for Sc(MDA)2 correspond to first–order saddle points. The ground electronic states of Sc(MDA)2 and Sc(MDA)3 molecules are the states of 2 A g and 1 A 1 symmetries, respectively. For both configurations (D 2h and D 2d of the Sc(MDA)2 molecule, the energies of vertical electron transitions were calculated using the CASSCF method. The formation of chemical bonding in the compounds considered was analyzed. It was shown that the Sc–O bond is predominantly ionic and the π conjugation is characteristic only of the oxygen–carbon skeleton of the chelate fragment. The results obtained are compared with literature experimental and theoretical data for related compounds.