Triplet-State Zero-Field Splitting Calculations in Aromatic Hydrocarbons and Heterocycles

Abstract

Zero‐field splitting in the lowest triplet states of aromatic hydrocarbons and heterocycles is calculated using several molecular orbital schemes. The most reliable results are obtained using closed‐shell SCF molecular orbitals with configuration interaction between all triplet states singly excited relative to the ground state. Slater‐type atomic orbitals are used and the two‐center Coulomb integrals involving these orbitals are evaluated exactly. Results calculated using best Slater‐type orbitals are consistently higher than experimental values, but good agreement with experiment is obtained when two‐zeta of four‐zeta atomic orbitals are used.