Electronic spectrum and d-orbital energies of the planar CuCl42– ion in bis(creatininium) tetrachlorocuprate

Abstract

The low temperature, polarized electronic spectrum of the (100) crystal face of (creatininium)₂CuCl₄ is reported and interpreted in terms of a d-orbital energy sequence d_x2–y2 > > d_xy > d_xz > d_yz > d_z2 for the planar CuCl₄^2– ion present in this compound; the marked temperature dependence of the spectrum and its comparison with that of the similar compound (PhCH₂CH₂NH₂Me)₂CuCl₄ suggests that coupling both with lattice modes and an out-of-plane bonding mode of very low energy is important in the mechanism by which the electronic transition gain intensity in compounds of this kind.