A MESOSCOPIC MOLECULAR SUPERPARAMAGNET - PREPARATION, CRYSTAL-STRUCTURE AND MAGNETIC-PROPERTIES OF 12)(H2O)(4)]CENTER-DOT-2H(2)O-CENTER-DOT-4ETCO(2)H WITH AN S=9 GROUND-STATE

The first dodecanuclear manganese aggregate containing heterocarboxyla te ligands [Mn12O12(O-2 CMe)(4)(O(2)CEt)(12)(H2O)(4)] (1) has been pre pared and structurally characterized. The single crystal X-ray diffrac tion of 1 shows that it is similar to [Mn12O12(O(2)CR)(16)(H2O)(4)] (2 a, R = Me or 2b, R = Ph) in its skeletal structure but it has a differ ent crystal structure. Primary magnetism studies imply that 1 has an S = 9 spin ground state. A clear hysteresis loop was also observed for a polycrystalline sample of 1 . 2H(2)O . 4EtCOOH, but there was no ano maly in susceptibility down to 1.5 K. The cluster 1 represents another example of nanometre-sized molecular superparamagnets without particl e size distribution. (C) 1997 Elsevier Science Ltd.