Influence of the ligands and solvents on the magnetic properties of the single molecule magnets:: [Mn12O12(O2CR)16(L)4]•nS (R = 3-Cl-C6H4, L = 3-Cl-C6H4CO2H and water, n = 1, S = 3-Cl-C6H4CO2H(1); R = CH2Cl, L = water, n = 0 (2))

The syntheses and magnetochemical properties of the title complexes are reported. The crystal structure of complex 1 has been characterized by X-ray diffraction. It is shown that the central core of complex 1 consists of a central cubane-like [Mn-4(IV) O-4](8+) held within a nonplanar ring of eight Mn-III ions by eight mu(3)-O2- ions. The ligations of complex 1 are provided by 16 eta(2)-mu-carboxylate groups and three water ligands as well as one terminal ligand 3-Cl-C6H4CO2H. For both complexes 1 and 2 the chi "(m) signals are observed in the region 2-10 K, measured at frequencies of 133, 1333, 9333 Hz, and exhibit two frequency-dependent chi "(m) peaks with a predominant peak in the 4-10 K region. The magnetization hysteresis loops for complexes 1 and 2 show a step-like character. These steps are attributable to resonant magnetization tunneling. Both the DC and AC susceptibility measurements indicate the difference in the ground-stare spin S = 9 and S = 10 for complexes 1 and 2, respectively. The effects of ligands and solvents on the magnetic properties of the title complexes are briefly discussed. (C) 2000 Elsevier Science S.A. All rights reserved.