Calculations of g Tensors and Hyperfine Splitting Tensors for Molecules in Their Triplet States

Abstract

Abstract The g tensors and hyperfine splitting (hfs) tensors of simple organic radicals in their triplet states have been calculated by using an all valence electron SCF MO method with a first order perturbation treatment. The molecular orbital spin density is partitioned into the σ- and π-electron spin delocalization (SD) terms and the rest terms of spin polarization (SP) which arise from the CI effect. The g tensors for CH2 and several other carbenes which have triplet ground states and for formaldehyde in its nπ* and nσ* excited triplet states are evaluated. The calculated α-proton hfs constants of CH2 contributing from the π orbital well compare with the observed hfs constants of the triplet naphthalene and the doublet malonic acid radical. The anisotropic carbon-13 hfs constants of CH2 are determined almost completely by the SD contribution and their absolute values are in good accord with those observed for CD2. Contribution of the SP terms to the isotropic hfs constant is found to be fairly large. Prediction of the hfs constants in CF2 and CHF is made.