Charge transfer effects on the paramagnetic properties of the [M(C ₈H ₈) ₂] and M(C ₅H ₅)(C ₈H ₈); M = Ti, Zr, Hf and Th, complexes

A systematic study of a series of (19e) [M(COT) ₂] ⁿ, (n = -1 for Th and n = +1 for Ti, Zr, Hf) and (17e) MCpCOT, where Cp and COT represent cyclopentadienyl [C ₅H ₅] ^- and cyclooctatetraene [C ₈H ₈] ^-2, respectively, has been performed using relativistic density functional theory with the two components ZORA Hamiltonian for the inclusion of scalar and spin-orbit effects. The EPR parameters were obtained as second order properties employing the EPR/NMR algorithms with an inclusion of spin-orbit coupling. The obtained g tensor values are in good agreement with the experimental results and the calculations reveals that each ground state in all systems are nonbonding and of mostly of d _z ² character. There is a low spin density at protons site resulting from a direct delocalization of the unpaired electron spin on the 1s orbitals.