Paramagnetic anisotropy of planar cobalt(II) and copper(II) phthalocyanine, bis(pentane-2,4-dionato)copper(II), and bis(pentane-2,4-dithionato)cobalt(II)

Abstract

The principal crystalline and molecular susceptibilities, and their orientations, of cobalt(II) phthalocyanine, [Co(pc)], bis(pentane-2,4-dithionato)cobalt(II). [Co(pdt)₂]. copper(II) phthalocyanine, [Cu(pc)], and bis-(pentane-2,4-dionato)copper(II), [Cu(pd)₂], are reported. The diamagnetic anisotropy of the two pc derivatives makes a significant contribution to the observed anisotropy, especially in the cooper compound. The resulting paramagnetic anisotropy {and e.s.r. data in the case of [Co(pdt)₂]} is then used to confirm the S=½ ground state of each compound [⋯ d_z²¹ in both the cobalt(II) derivatives and d_xy¹ in both the copper(II) derivatives]. The marked in-plane anisotropy in [Co(pdt)₂], compared with the in-plane isotropy of [Co(pc)], is shown to arise from both the abnormally large splitting of the d_xz, d_yz pair of orbitals and the mixing of the d_xy and d_z² orbitals in low symmetry. An unambiguous assignment of two of the excited states in [Cu(pc)] can be made but ambiguities remain in [Cu(pd)₂].