Localized molecular orbitals for polyatomic molecules: Part VII. The tetracyanoquinodimethan molecule and its anions

Abstract

Wavefunctions for TCNQ, TCNQ −1 and TCNQ −2 have been obtained in the approximation of partial retention of diatomic differential overlap (PRDDO). For TCNQ and TCNQ −2 the geometries were partially optimized. Localized molecular orbitais (LMO's) have been obtained for TCNQ and TCNQ −2 using the Boys' criterion. For TCNQ these LMO's give the usual description of the bonding in the molecule. However, for TCNQ −2 the LMO's show an unexpected bonding pattern of a benzenoid ring and lone pairs on C7 and C8. The rotation barrier about the C1–C7 bond in TCNQ −2 is calculated to be 12 kcal mole −1, the maximum value for the conjugative effect in this bond.