Self-assembly of a Mng nanoscopic mixed-valent cluster:: Synthesis, crystal structure, and magnetic Behavior

A rare Mn-9 mu(3)-oxo-centered mixed-valent cluster [Mn9O7(O2CPh)(11)(thmn)(py)(2) (H2O)(3)] (1) is prepared by assembling an oxo-centered (MnMn2III)-Mn-II triangle, [Mn3O(O2CPh)(6)(py)(2)(H2O)]center dot 0.5MeCN, as the secondary building unit in the presence of a tripodal alcohol, 1,1,1-tris(hydroxymethyl) nitromethane (H(3)thmn), as the capping ligand. Complex 1 was formed along with a minor byproduct, [Mn6O2(O2CPh)(10)(MeCN)(4)] (2). Complex 1 was characterized by X-ray single-crystal structure analysis and was crystallized in a monoclinic system, space group P2(1)/n, a = 16.214(6) angstrom, b = 25-874(10) angstrom, c = 26.497(10) angstrom, and beta = 94.214(7)degrees. The Manganese-oxo-carboxyl ate core in 1 looks like a funnel. Variable-temperature magnetic studies down to 2 K reveal the existence of dominant ferromagnetic interaction within the cluster. Alternating current susceptibility data of the cluster show strong frequency dependence of both the real and imaginary. parts of susceptibility chi ' and chi '' below 5 K. Moreover, the calculated relaxation time, tau(0) = 1.2 x 10(-7) s, and the energy barrier, Delta E = 25 K, are consistent with the single-molecule magnetic behavior of 1.