Abstract

The isolation and characterization of a new pair of Jahn-Teller isomers of [Mn12O12(O2CCH2Bu')(16)(H2O)(4)] (3) are reported: complex 3.CH2Cl2.MeNO2 (3a) and 3.CH2Cl2.MeCN (3b). These Jahn-Teller isomers have been crystallized in the same triclinic space group, and differ only in one abnormally oriented Jahn-Teller axis in 3a and in the identity of one solvent molecule of crystallization. Magnetic data show much faster magnetization relaxation for 3a (the low-temperature, LT, form) compared with 3b (the high-temperature, HT, form), exhibiting a peak in the out-of-phase magnetic susceptibility in the 2-4 and 5-7 K ranges, respectively. Magnetization vs. DC field scans on aligned crystals of 3a and 3b display hysteresis with coercivities that vary with temperature, as expected for single-molecule magnets. The hysteresis loops also exhibit the step features that are the signature of quantum tunneling of magnetization. (C) 2003 Elsevier Science Ltd. All rights reserved.