Collect. Czech. Chem. Commun. 1998, 63, 1485-1497

Spin-Orbit Coupling in Biradicals. 3. Heavy Atom Effects in Carbenes

Zdeněk Havlasa and Josef Michlb

a Institute of Organic Chemistry and Biochemistry, Academy of Sciences of the Czech Republic, 166 10 Prague 6, Czech Republic
b Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309-0215, U.S.A.


CASSCF(8,6)/cc-pVDZ calculations of electron spin-spin dipole interaction tensor in the lowest triplet state of CH2, CHF, CHCl, and CHBr, spin-orbit coupling of each of the three sublevels with the lowest singlet, and the triplet zero-field-splitting parameters are reported as a function of the valence angle, with bond lengths optimized for the triplet state at the B3LYP/cc-pVTZ level of approximation. Both the one- and the two-electron parts of the spin-orbit coupling Hamiltonian are used, and the contributions to spin-orbit coupling provided by each atom and orbital pair in Weinhold's natural hybrid orbital basis are evaluated separately. This provides intuitive insight into the origin of spin-orbit coupling in carbenes and especially, the heavy atom effect of the substituent.

Keywords: Carbenes; Spin-orbit coupling; Spin-spin dipolar coupling; Zero-field-splitting parameters; Ab initiocalculations.