Electronic and electron spin resonance spectra of diamminocopper(II) trithiocyanatoargentate(I) and iodobis-(2,2′-bipyridyl)copper(II) iodide

Abstract

The polarised single-crystal electronic and e.s.r. spectra of [Cu(NH₃)₂]Ag(SCN)₃ and [Cu(bipy)₂I]I (bipy = 2,2′-bipyridyl) are reported. The former is assigned in D_3h symmetry, including the effect of spin–orbit coupling, and the latter in C_2v and D₂ effective symmetries. Reasons are given for preferring the assignment in C_2v symmetry. Both complexes are consistent with a one-electron orbital sequence in D_3h symmetry of d_z² > d_xz,d_yz > d_xy,d_x²–y² an order different from that normally predicted by simple crystal-field calculations. This sequence is consistent with substantial out-of-plane π-bonding from the thiocyanate ligands in [Cu(NH₃)₂]Ag(SCN)₃ and from the iodide ligand in [Cu(bipy)₂I]I. A simple method for the measurement of single-crystal g-values is described and applied.