Mn8 and Mn16 clusters from the use of 2-(hydroxymethyl)pyridine, and comparison with the products from bulkier chelates: a new high nuclearity single-molecule magnet.
The synthesis, crystal structures, and magnetochemical characterization of two new Mn clusters [Mn(8)O(2)(O(2)CPh)(10)(hmp)(4)(MeOH)(2)] (1; 6Mn(II), 2Mn(III)) and [Mn(16)O(8)(OH)(2)(O(2)CPh)(12)(hmp)(10)(H(2)O)(2)](O(2)CPh)(2) (2; 6Mn(II), 10Mn(III)) are reported. They were obtained from the use of 2-(hydroxymethyl)pyridine (hmpH) under the same reaction conditions but differing in the presence or absence of added base. Thus, the reaction of hmpH with Mn(O(2)CPh)(2) in CH(2)Cl(2)/MeOH led to isolation of octanuclear complex 1, whereas the analogous reaction in the presence of NEt(3) gave hexadecanuclear complex 2. Complexes 1 and 2 possess either very rare or unprecedented core structures that are related to each other: that of 1 can be described as a linked pair of incomplete [Mn(4)O(3)] cubanes, while that of 2 consists of a linked pair of complete [Mn(4)O(4)] cubanes, on either side of which is attached a tetrahedral [Mn(4)(μ(4)-O)] unit. Solid-state direct current (dc) and alternating current (ac) magnetic susceptibility measurements on 1 and 2 establish that they possess S = 5 and 8 ground states, respectively. Complex 2 exhibits frequency-dependent out-of-phase (χ(M)") ac susceptibility signals at temperatures below 3 K suggestive of a single-molecule magnet (SMM). Magnetization versus applied dc field sweeps on single crystals of 2·10MeOH down to 0.04 K exhibited hysteresis, confirming 2 to be a new SMM. Comparison of the structure of 2 (Mn(16)) with Mn(12) or Mn(6) clusters previously obtained under the same reaction conditions but with two Me or two Ph groups, respectively, added next to the alkoxide O atom of hmp(-) indicate their influence on the nuclearity and structure of the products as being due to the overall bulk of the chelate plus the decreased ability of the O atom to bridge.
Department of Chemistry, University of Florida, Gainesville, Florida 32611-7200, USA.
Taketo
T
Taguchi
Wolfgang
W
Wernsdorfer
Khalil A
KA
Abboud
George
G
Christou
D002614:Chelating Agents / Q000138:chemical synthesis* / Q000737:chemistry; D056831:Coordination Complexes / Q000138:chemical synthesis* / Q000737:chemistry; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D008280:Magnetics; D008345:Manganese / Q000737:chemistry*; D015394:Molecular Structure; D011725:Pyridines / Q000737:chemistry*
D002614:Chelating Agents; D056831:Coordination Complexes; D011725:Pyridines; D008345:Manganese