Single-crystal electronic and electron spin resonance spectra of thiocyanatotriethylenetetraminecopper(II) thiocyanate

The polarised single-crystal electronic spectra and e.s.r. spectra of thiocyanatotriethylenetetraminecopper(II) thiocyanate have been measured. The correlation of the single-crystal g-values and the crystallographic data suggest a dxy ground-state for the approximately square-pyramidal CuN4S chromophore present. The electronic spectra are interpreted in C2v effective symmetry and yield a tentative partial one-electron orbital sequence: dxy > dz2 > dxz′≈dyz. The concept of varying tetragonal distortion, introduced to discuss the stereochemistry of six-co-ordinate copper(II) complexes, is extended to cover a five-co-ordinate square-pyramidal stereochemistry.