Theoretical prediction of g tensors and hyperfine coupling tensors of triplet molecules

Abstract

This is the first time that all-valence-electron SCF MO calculations of g tensors and hyperfine coupling (HFC) tensors of some triplet molecules have been carried out. The molecular orbital spin density is partitioned into the σ and π-electron spin delocalization (SD) terms and the remaining terms of spin polarization (SP) which arise from the CI effect. The g tensors for CH2 and some other carbenes which have ground triplet states and the excited triplet formaldehyde are evaluated. The origin of HFC in CH2 is analyzed in detail by using the partitioning method for spin density matrices. The absolute values of the isotropic and anisotropic 13C HFC tensors of CH2 calculated by taking into account the SD terms only are in good agreement with those observed for CD2. The contribution of the SP terms to the isotropic HFC tensors is fairly large, while the contribution to the anisotropic HFC tensors is negligibly small.