Mn4, Mn6, and Mn11 clusters from the use of bulky diphenyl(pyridine-2-yl)methanol.
The synthesis, crystal structure, and magnetochemical characterization are reported of three new Mn clusters [Mn(4)O(2)(O(2)CBu(t))(5)(dphmp)(3)] (1), [Mn(6)O(4)(OMe)(2)(O(2)CPh)(4)(dphmp)(4)] (2), and [Mn(11)O(7)(OMe)(7)(O(2)CPh)(7)(dphmp)(4)(MeOH)(2)] (3). They were obtained from the use of diphenyl(pyridine-2-yl)methanol (dphmpH), a bulkier version of the 2-(hydroxymethyl)pyridine (hmpH) reagent commonly employed previously in Mn chemistry. The reaction of dphmpH with MnCl(2) x 4 H(2)O and NaO(2)CBu(t) in MeCN/MeOH (30 mL, 5:1 v/v) led to the isolation of tetranuclear complex 1, whereas the analogous reaction with NaO(2)CPh gave hexanuclear complex 2. When the 5:1 solvent ratio in the latter reaction was changed to 1:29, the isolated product was now undecanuclear complex 3. Complexes 1-3 all possess rare or unprecedented Mn(x) topologies: Complex 1 possesses a [Mn(4)(mu(3)-O)(2)](8+) (4 Mn(III)) butterfly core, one edge of which is additionally bridged by an alkoxide arm of a dphmp(-) chelate; complex 2 possesses a [Mn(6)(mu(4)-O)(2)(mu(3)-O)(2)(mu(3)-OMe)(2)](8+) (6 Mn(III)) core with a face-sharing double cubane topology; and complex 3 (Mn(II), 10 Mn(III)) possesses a [Mn(4)(mu(4)-O)(3)(mu(3)-OMe)](5+) cubane unit, attached on one side to a Mn(II) atom by a mu(4)-O atom and alkoxide groups, and on the other side to a [Mn(5)(mu(4)-O)(mu(3)-O)(3)(mu(3)-OMe)(mu-OR)(3)](3+) unit consisting of three face-sharing defective cubanes linked to an additional Mn(III) atom by a mu(3)-O atom. Solid-state dc and ac magnetic susceptibility measurements on 1-3 establish that they possess S = 0, 3, and 5/2 ground states, respectively. ac susceptibility studies on 2 and 3 reveal weak non-zero frequency-dependent out-of-phase (chi(M)'') signals at temperatures below 3 K, possibly indicative of single-molecule magnets with very small barriers. The combined results demonstrate a ligating difference between bulky dphmp(-) and hmp(-), and the resulting usefulness of the former to provide access to a variety of Mn(x) molecular species not known with the latter.
Taguchi
Taketo
T
Department of Chemistry, University of Florida, Gainesville, Florida 32611-7200, USA.
Daniels
Matthew R
MR
Abboud
Khalil A
KA
Christou
George
G
D008280:Magnetics; D008345:Manganese / Q000737:chemistry*; D000432:Methanol / Q000737:chemistry*; D008956:Models, Chemical; D008958:Models, Molecular; D015394:Molecular Structure; D010100:Oxygen / Q000737:chemistry; D011725:Pyridines / Q000737:chemistry
D011725:Pyridines; D008345:Manganese; D010100:Oxygen; D000432:Methanol