A low spin d7 Rh2+ center with nearly axial symmetry was studied by using Q-band electron nuclear double resonance. An analysis of the interaction of the unpaired electron, with first-shell Cl- ions along the gz-axis of the complex, proved that the center had C2v symmetry. This strongly supported its status as a [RhCl6]4- complex, accompanied by 2 next-nearest neighbor cation vacancies in a cis configuration. Moreover, the 2-fold symmetry axis of this complex was identified as being the g-tensor axis corresponding to the largest principal g-value. The magnetic resonance properties of this center could be explained by assuming that the central Rh2+ ion exhibited an off-center displacement toward the cation vacancies.

Q-Band Electron Nuclear Double-Resonance Detection of the Cation Vacancies near the cis-[RhCl6]4– 2Vac Complex in NaCl. H.Vrielinck, F.Callens, P.Matthys: Physical Review B, 2001, 64[21], 214105 (6pp)