Single-molecule magnets: site-specific ligand abstraction from [Mn12O12(O2CR)16(H2O)4] and the preparation and properties of [Mn12O12(NO3)4(O2CCH2Bu(t))12(H2O)4].

Site-selective carboxylate abstraction has been achieved from [Mn12O12(O2CR)16(H2O)4] complexes by treatment with HNO3 in MeCN. The reaction of the R = Ph or CH2But complexes with 4 equiv of HNO3 gives [Mn12O12(NO3)4(O2CR)12(H2O)4] (R = CH2But (6) or Ph (7)) in analytical purity. Complex 6·MeNO2 crystallizes in monoclinic space group C2/c with the following cell parameters at −168 °C:  a = 21.280(5), b = 34.430(8), c = 33.023(8) A, β = 104.61(1)°, V = 23413 A, and Z = 8. The four NO3- groups are not disordered and are bound in bridging modes at axial positions formerly occupied by bridging carboxylate groups. 1H NMR spectroscopy in CD2Cl2 and CDCl3 shows retention of the solid-state structure on dissolution in these solvents. DC magnetic susceptibility (χM) and magnetization (M) studies have been carried out in the 2.00−300 K and 1.0−7.0 T ranges. Fits of M/NμB versus H/T plots gave S = 10, g = 1.92, and D = −0.40 cm-1, where D is the axial zero-field splitting parameter. AC magnetic susceptibility studie...