A Family of [Mn 6 ] Complexes Featuring Tripodal Ligands Constantinos J. Milios, † Maria Manoli, † Gopalan Rajaraman, ‡ Abhudaya Mishra, § Laura E. Budd, † Fraser White, † Simon Parsons, † Wolfgang Wernsdorfer, | George Christou, § and Euan K. Brechin* ,†,‡ School of Chemistry, The UniVersity of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, U.K., Department of Chemistry, The UniVersity of Manchester, Oxford Road, Manchester M13 9PL, U.K., Department of Chemistry, UniVersity of Florida, GainesVille, Florida 32611-7200, and Laboratoire Louis Ne ´ el, CNRS, 38042 Grenoble Cedex 9, France Received April 20, 2006 The synthesis and magnetic properties of four new Mn complexes containing tripodal alcohol ligands are reported: [Mn 6 (OAc) 6 (H 2 tea) 2 (tmp) 2 ]‚2MeCN (1‚2MeCN), [Mn 6 (acac) 4 (OAc) 2 (Htmp) 2 (H 2 N-ep) 2 ](2), [Mn 6 (OAc) 8 (tmp) 2 (py) 4 ]‚2py (3‚2py), and [Mn 6 (OAc) 8 (thme) 2 (py) 4 ]‚2py (4‚2py) [H 3 tea, triethanolamine; H 3 tmp, 1,1,1-tris(hydroxymethyl)propane; H 2 N-H 2 ep, 2-amino-2-ethyl-1,3-propanediol; H 3 thme, 1,1,1-tris(hydroxymethyl)ethane]. All complexes are mixed- valent with a [Mn III 2 Mn II 4 ] oxidation assignment and are constructed from four edge-sharing triangles but differ slightly in that complexes 1 and 2 display a [Mn III 2 Mn II 4 (µ 2 -OR) 6 (µ 3 -OR) 4 ] 4+ core, while complexes 3 and 4 feature [Mn III 2 Mn II 4 (µ 2 -OR) 2 (µ 3 -OR) 4 ] 8+ and [Mn III 2 Mn II 4 (µ 2 -OR) 4 (µ 3 -OR) 4 ] 6+ cores, respectively. dc and ac magnetic susceptibility studies in the 2-300 K range for complexes 1-4 reveal the presence of dominant antiferromagnetic exchange interactions, leading to ground states of S ) 0 for 1 and 2, while complexes 3 and 4 display S ) 4 ground states with D ) -0.44 and -0.58 cm -1 , respectively. Single-molecule magnetism behavior was confirmed for 3 and 4 by the presence of sweep-rate and temperature-dependent hysteresis loops in single-crystal M vs H studies at temperatures down to 40 mK. Theoretical density functional calculations were used to evaluate the individual pairwise exchange interactions present, confirming the diamagnetic ground states for 1 and 2 and the S ) 4 ground states for 3 and 4. Introduction One of the most intriguing recent developments in mo- lecular magnetism is the discovery that simple coordination compounds containing paramagnetic metal ions can function as single-domain magnetic particles at low temperatures in the absence of an external magnetic field. Such molecules, now termed “single-molecule magnets” (SMMs), exist if two criteria are met, namely, a large (or at least nonzero) spin ground state (S) and a large magnetoanisotropy of the Ising (easy-axis) type (as measured by the (negative) zero-field- splitting parameter, D). 1 As such, these molecules represent the ultimate down-limit in the scale of magnetic materials and potentially promise unique applications in information storage and quantum computation. 2 Since the discovery of the phenomenon, 3 many complexes have been found to possess such behavior, and while the vast majority of these contain Mn ions in various oxidation states, 4 there have been reported examples of Fe, V, Co, Ni, and, very recently, combinations of 3d with 4d, 5d, and 4f paramagnetic ions. 5-9 An important future development for the SMM field is the discovery of synthetic schemes that can yield new molecules and families of related molecules with large spins and/or significant magnetoanisotropies. Toward this end, two successful methodologies have emerged: the first is based on “serendipitous self-assembly”, whereby suitable flexible * To whom correspondence should be addressed. E-mail: ebrechin@ staffmail.ed.ac.uk. † The University of Edinburgh. ‡ The University of Manchester. § University of Florida. | Laboratoire Louis Ne ´el, CNRS. (1) (a) Gatteschi, D.; Sessoli, R. Angew. Chem., Int. Ed. 2003, 42, 268. (b) Christou, G.; Gatteschi, D.; Hendrickson, D. N.; Sessoli, R. MRS Bull. 2000, 25, 66. (2) Representative references include: (a) Tejada, J.; Chudnovsky, E. M.; del Barco, E.; Hernadez, J. M.; Spiller, T. P. Nanotechnology 2001, 12, 181. (b) Stamp, P. C. Nature 1996, 383, 125. (c) Wernsdorfer, W.; Sessoli, R. Science 1999, 284, 133. (3) (a) Lis, T. Acta Crystallogr. 1980, B36, 2042. (b) Caneschi, A.; Gatteschi, D.; Sessoli, R.; Barra, A. L.; Brunel, L. C.; Guillot, M. J. Am. Chem. Soc. 1991, 113, 5873. (c) Sessoli, R.; Tsai, H. L.; Schake, A. R.; Wang, S. Y.; Vincent, J. B.; Folting, K.; Gatteschi, D.; Christou, G.; Hendrickson, D. N. J. Am. Chem. Soc. 1993, 115, 1804. (d) Sessoli, R.; Gatteschi, D.; Caneschi, A.; Novak, M. A. Nature 1993, 365, 141. Inorg. Chem. 2006, 45, 6782-6793 6782 Inorganic Chemistry, Vol. 45, No. 17, 2006 10.1021/ic060676g CCC: $33.50 © 2006 American Chemical Society Published on Web 07/27/2006