An electron paramagnetic resonance study of spin site variations in Cu(hfac)2 complexes with 5-(3-N-tert-butyl-N-aminoxylphenyl)pyrimidine

Abstract

The X- and Q-band EPR spectra of coordination compounds of 5-(3-N-tert-butyl-N-aminoxylphenyl)pyrimidine (3PPN) with Cu(hfac)2 show peaks in the g≈2.3 region attributable to parallel component transitions of Cu(II) axially coordinated to pyrimidine, and in the g≈2.0–2.2 region attributable to Cu(II) directly coordinated with the aminoxyl NO· radical unit plus perpendicular component transitions of the Cu(II) coordinated to pyrimidine. The spectral region with the Cu(II)–aminoxyl resonance can show temperature dependent behavior attributable to reversible Jahn–Teller distortions, analogous to behavior seen in Ovcharenko’s “breathing crystal” Cu(II) complexes with nitronylnitroxides (e.g., Veber et al. (2008) [5]).