Jahn-Teller tunneling in copper(II)-doped hexaimidazole zinc(II) dichloride tetrahydrate

Abstract

Single crystal electron paramagnetic resonance study on Cu(II)-doped in hexaimidazole zinc(1I) dichloride tetrahydrate gives an isotropic quartet spectrum at room temperature with g iso = 2.1702 and Cu A iso. = −57.67 gauss. The 77 K spectrum of the same system gives a one-ion-per-unit-cell-type EPR spectrum with g | = 2.2995, g ⊥ = 2.0878, Cu A | = −158.3 G and A ⊥ = −37.5 G. From the two spectra it has been inferred that the Cu complex undergoes dynamic Jahn-Teller distortion at RT and at 77 K the one-ion-per-unit-cell spectrum is indicative of tunneling between the three Jahn-Teller configurations. The ground state has been identified as the tunneling quartet. The possibility of “vanishing Jahn-Teller” effect in this system has been ruled out, on the basis of the angular variation of the EPR spectra.