title: Mixed-valence tetra- and hexanuclear manganese complexes from the flexibility of pyridine-containing beta-diketone ligands.
abstract: The reactions of [Mn3O(O2CCCl3)6(H2O)3] with 1-phenyl-3-(2-pyridyl)propane-1,3-dione (HL(1)) and 1-(2-pyridly)-3-(p-tolyl)propane-1,3-dione (HL(2)) in CH2Cl2 afford the mixed-valence Mn(II)2Mn(III)2 tetranuclear complexes [Mn4O(O2CCCl3)6(L(1))2] (1) and [Mn4O(O2CCCl3)6L2(2)] (2), respectively. Similar reactions employing [Mn3O(O2CPh)6(H2O)(py)2] with HL(1) and HL(2) give the Mn(II)3Mn(III)3 hexanuclear complexes [Mn6O2(O2CPh)8(L(1))3] (3) and [Mn6O2(O2CPh)8L3(2)] (4), respectively. Complexes 1.2CH2Cl2, 2.2CH2Cl2.H2O, 3.1.5CH2Cl2.Et2O.H2O, and 4.2CH2Cl2 crystallize in the triclinic space group P1, monoclinic space group P2(1)/c, monoclinic space group P2 1/ n, and monoclinic space group P2(1)/n, respectively. Complexes 1 and 2 consist of a trapped-valence tetranuclear core of [Mn(II)2Mn(III)2(mu4-O)](8+), and complexes 3 and 4 represent a new structural type, possessing a [Mn(II)3Mn(III)3(mu4-O)2](11+) core. The magnetic data indicate that complexes 3 and 4 have a ground-state spin value of S = 7/2 with significant magnetoanisotropy as gauged by the D values of -0.51 cm (-1) and -0.46 cm (-1), respectively, and frequency-dependent out-of-phase signals in alternating current magnetic susceptibility studies indicate their superparamagnetic behavior. In contrast, complexes 1 and 2 are low-spin molecules with an S = 1 ground state. Single-molecule magnetism behavior confirmed for 3 the presence of sweep-rate and temperature-dependent hysteresis loops in single-crystal M versus H studies at temperatures down to 40 mK.
authors.affiliation: Department of Chemistry, National Cheng Kung University, Tainan, 701, Taiwan, Republic of China.
authors.forename: Chen-I
authors.initials: CI
authors.lastname: Yang
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Wernsdorfer
authors.forename: Yu-Jhe
authors.initials: YJ
authors.lastname: Tsai
authors.forename: George
authors.initials: G
authors.lastname: Chung
authors.forename: Ting-Shen
authors.initials: TS
authors.lastname: Kuo
authors.forename: Gene-Hsiang
authors.initials: GH
authors.lastname: Lee
authors.forename: Minghuey
authors.initials: M
authors.lastname: Shieh
authors.forename: Hui-Lien
authors.initials: HL
authors.lastname: Tsai
mesh_terms: D007659:Ketones / Q000737:chemistry*; D007700:Kinetics; D008024:Ligands; D017895:Manganese Compounds / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D011407:Propane / Q000737:chemistry; D011725:Pyridines / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013816:Thermodynamics
chemical_list: D007659:Ketones; D008024:Ligands; D017895:Manganese Compounds; D011725:Pyridines; D011407:Propane