Effect of the fifth coordination site on the spin states of bis(benzoylacetylacetanato)bispyridinedicopper(II) complex

Abstract

The spin and charge excitation gap and spin density have been calculated for bis(benzoylacetylacetanato)bispyridinedicopper(II) using a valence bond basis and model Hamiltonian based on the Pariser-Parr-Pople (PPP) approximation. The singlet-triplet energy gap depends upon the exchange interaction (K_oo) of the bridging oxygen atom. The results of this 12-orbital, 18-electron system are compared with those of a 10-orbital, 14-electron system, viz. bis(benzoylacetylacetanato)dicopper(II), the latter without axial ligation. Changing the nitrogen to oxygen in the fifth coordination site does not seem to affect the singlet-triplet energy gap and spin and charge density on the copper(II) atoms. The results indicate that K_oo, which is sensitive to geometry, plays a decisive role in determining the excitation gap.