title: From pseudo to true C(3) symmetry: magnetic anisotropy enhanced by site-specific ligand substitution in two Mn(15)-carboxylate clusters.
abstract: Two new mixed-valence manganese-carboxylate clusters, [MnIII9MnIV6(O2CPh)12(micro3-O)13(micro-O)4(micro-OMe)5(MeOH)4(H2O)5]2.1.5PhCO2H.MeOH.6H2O (1, PhCO2H = benzoic acid) and [MnIII9MnIV6(O2CCh)12(micro3-O)13(micro-O)4(micro-OMe)5(MeOH)3(H2O)6].0.5MeOH.2.5H2O (2, ChCO2H= cyclohexanecarboxylic acid) contain new disklike Mn15 cores. Both 1 and 2 can be synthesized by the conventional manganese redox reaction (MnO4- oxidizing Mn2+) in methanol solution. 2 can be also synthesized via the site-specific ligand substitution reaction from 1. 1 crystallizes in the triclinic space group P, whereas 2 crystallizes in the trigonal space group P. Magnetic study shows that both 1 and 2 have the same ground spin states ST = 2. Compared to the silence of the out-of-phase ac susceptibility of 1, 2 shows clearly slow magnetic relaxation behavior above 1.8 K due to the dramatically enhanced axial magnetic anisotropy (D = -0.89 and -1.58 cm-1 for 1 and 2, respectively, which was obtained by fitting the plots of M vs H/T with the program ANISOFIT 2.0).
authors.affiliation: MOE Laboratory of Bioinorganic and Synthetic Chemistry/State Key Laboratory of Optoelectronic Materials and Technologies, School of Chemistry & Chemical Engineering, Sun Yat-Sen University, Guangzhou, China.
authors.forename: Yan-Zhen
authors.initials: YZ
authors.lastname: Zheng
authors.forename: Wei
authors.initials: W
authors.lastname: Xue
authors.forename: Wei-Xiong
authors.initials: WX
authors.lastname: Zhang
authors.forename: Ming-Liang
authors.initials: ML
authors.lastname: Tong
authors.forename: Xiao-Ming
authors.initials: XM
authors.lastname: Chen
mesh_terms: D016880:Anisotropy; D002244:Carbon / Q000737:chemistry*; D002264:Carboxylic Acids / Q000737:chemistry; D003460:Crystallization; D018360:Crystallography, X-Ray; D008024:Ligands; D008280:Magnetics; D008345:Manganese / Q000737:chemistry*; D000432:Methanol / Q000737:chemistry; D008958:Models, Molecular; D015233:Models, Statistical; D008968:Molecular Conformation; D010084:Oxidation-Reduction
chemical_list: D002264:Carboxylic Acids; D008024:Ligands; D008345:Manganese; D002244:Carbon; D000432:Methanol