High-Spin Mn Wheels Maria Manoli, ² Alessandro Prescimone, ² Rashmi Bagai, ‡ Abhudaya Mishra, ‡ Muralee Murugesu, ‡ Simon Parsons, ² Wolfgang Wernsdorfer, § George Christou, ‡ and Euan K. Brechin* ,² School of Chemistry, The UniVersity of Edinburgh, West Mains Road, Edinburgh EH9 3JJ, 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, 2007 The syntheses, structures, and magnetic properties of the complexes [Mn IV 4 Mn III 10 Mn II 2 O 2 (OCH 3 ) 12 (tmp) 8 (O 2 CCH 3 ) 10 ]‚ 3Et 2 O(1‚3Et 2 O), [Mn IV 2 Mn III 18 Mn II 2 O 6 (OCH 3 ) 14 (O 2 CCH 3 ) 16 (tmp) 8 (HIm) 2 ]‚2CH 3 OH (2·2CH 3 OH), and [Mn IV 2 Mn III 18 Mn II 2 O 6 - (OCH 3 ) 14 (O 2 CCH 3 ) 16 (Br-mp) 8 (HIm) 2 ]‚2C 6 H 14 ‚5CH 3 OH (3‚2C 6 H 14 ‚5CH 3 OH) are reported. The unusual wheel-like complexes were prepared by the treatment of [Mn 3 O(O 2 CCH 3 ) 6 (HIm) 3 ](O 2 CCH 3 ) (HIm ) imidazole) with 1,1,1-tris- (hydroxymethyl)propane (H 3 tmp) (1 and 2) or 2-(bromomethyl)-2-(hydroxymethyl)-1,3-propanediol (Br-mpH 3 )(3) in the presence of sodium methoxide (NaOCH 3 , 2, and 3) in CH 3 OH. Complex 1‚3Et 2 O crystallizes in the triclinic space group P1h, while complexes 2‚2CH 3 OH and 3‚2C 6 H 14 ‚5CH 3 OH crystallize in the orthorhombic space group Pbca. Direct current magnetic susceptibility data, collected for 1-3 in the respective 1.8-300 K and 0.1-7 T temperature and magnetic-field ranges, afford spin ground-state values of S ) 14 ± 1 for complex 1 and S ) 9 ± 1 for complexes 2 and 3. Alternating current susceptibility measurements performed on all three complexes in the 1.8-10 K temperature range in a 3.5 G oscillating field at frequencies between 50 and 1000 Hz reveal out- of-phase l′′ M signals below approximately 3 K. Single-crystal hysteresis loop and relaxation measurements confirm single-molecule magnetism behavior. Introduction The synthesis of polynuclear manganese clusters consti- tutes an important modern facet of chemistry and physics, with the advent of single-molecule magnetism a catalyst for the resurgence of worldwide interest. 1 Single-molecule magnets (SMMs) are molecules that display magnetization hysteresis that is purely intramolecular in origin and as such potentially represent a technologically important family of complexes. Many polynuclear clusters containing 3d transi- tion metals have since been reported to be SMMs despite the relative difficulty in obtaining molecules that contain relatively high spin ground-state values in combination with Ising-type anisotropy. 2 Isotropic high-spin polynuclear clus- ters cannot function as nanoscale magnets but are candidates to act as very low-temperature magnetic refrigerants. 3 The vast majority of SMMs contain manganese and are mixed- valent clusters containing multiple Mn III ions whose Jahn- * To whom correspondence should be addressed. E-mail: ebrechin@ staffmail.ed.ac.uk. ² University of Edinburgh. ‡ University of Florida. § Laboratoire Louis Ne´el. (1) (a) 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. (b) Sessoli, R.; Gatteschi, D.; Caneschi, A.; Novak, M. A. Nature 1993, 365, 141. (c) Gatteschi, D.; Sessoli, R. Angew. Chem., Int. Ed. 2003, 42, 268. (d) Caneschi, A.; Gatteschi, D.; Sessoli, R.; Barra, A. L.; Brunel, L. C.; Guillot, M. J. Am. Chem. Soc. 1991, 113, 5873. (2) Aromı ´, G.; Brechin, E. K. Struct. Bonding (Berlin, Ger.) 2006, 122, 1. (3) (a) Evangelisti, M.; Luis, F.; Jongh, L. J.; Affronte, M. J. Mater. Chem. 2006, 16, 2534. (b) Evangelisti, M.; Candini, A.; Ghirri, A.; Affronte, M.; Brechin, E. K.; McInnes, E. J. L. Appl. Phys. Lett. 2005, 87, 072504. Chart 1. Structures of 1,1,1-tris(hydroxymethyl)propane (H3tmp) and 2-(bromomethyl)-2-(hydroxymethyl)-1,3-propanediol (Br-mpH3) Inorg. Chem. 2007, 46, 6968-6979 6968 Inorganic Chemistry, Vol. 46, No. 17, 2007 10.1021/ic7007528 CCC: $37.00 © 2007 American Chemical Society Published on Web 07/21/2007