DYNAMIC AND STATIC JAHN-TELLER DISTORTIONS IN A CUN6 CAGE COMPLEX

EPR studies of pure and doped (in an isostructural diamagnetic zinc la ttice) polycrystalline [Cu(di(amH)sar)](NO3)(4) over a wide range of t emperature (7-280 K) show that both undergo a transition from dynamic to static Jahn-Teller distortions. The spectra were simulated to get t he g- and A-tensors. The transition temperature for the pure polycryst alline sample is less than or equal to 120 K and for the doped one it is above room temperature. There is evidence for the existence of coop erative and localized Jahn-Teller distortions respectively in pure and doped crystals. From the g-tensors of the pure polycrystalline sample there is evidence, supported by single-crystal results, of rapid elec tronic exchange between two inequivalent Cu(II) sites.