The preparation and physical characterization are reported for a family of novel Mn12 single-molecule magnets having diphenylphosphate (labeled dppH) bridges, [Mn12O12(O2CR) 16 - x(dpp)x(H2O)y] (R = CH 3: x = 4, y = 0 (1); x = 8, y = 2 (2), R = Ph: x = 4, y = 4 (5); x = 8, y = 4 (6), and R = Et: x = 4, y = 4 (9)) and their tetraphenylphosphate salts [Ph4P][Mn12O12(O2CR) 16 - x(dpp)x(H2O)4] (R = CH 3: x = 4 (3); x = 8 (4) and R = Ph: x = 4 (7); x = 8 (8)). The crystal structures of 1 and 5 were characterized by X-ray. The X-ray structure analysis of 1 reveals that there are four five-coordinate MnIII ions with Mn⋯H approaches and without coordinating water molecules. The 1H NMR measurements show H2O can coordinate to a vacant site of 1 in CD2Cl2 solution. Ac magnetic susceptibility measurements indicate that nine complexes are single-molecule magnets. The increase of the number of dpp- ligands resulted in a decrease of the Ueff values of neutral Mn12 SMMs estimated from ac measurements. Complexes 1 and 5 show a quantum tunneling behavior, whose ground states were tentatively assigned to S = 10 with g = 1.78, and D = -0.60 K; S = 10 with g = 1.92, and D = -0.63 K, respectively.
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