Synthesis, structure and magnetism of {[Mn(m-OH)(m-OAc) 2 ] × /HOAc × / H 2 O} n and the facilitation of long-range magnetic order through hydrogen bonding David J. Price, Stuart R. Batten, Boujemaa Moubaraki, Keith S. Murray * School of Chemistry, Monash University, P.O. Box 23, Clayton, Vic. 3800, Australia Received 6 October 2002; accepted 23 October 2002 Abstract The manganese(III) complex {[Mn(m-OH)(m-OAc) 2 ] × /HOAc × /H 2 O} n (1 × /HOAc × /H 2 O) has a structure in which linear chains, containing three bridges made up of one hydroxide and two acetates, are linked together by hydrogen bonds to form 2D sheets. These hydrogen bonds exist between the m-OH  , the solvated acetic acid and water molecules, and the m-OAc  ligands on adjacent chains. The complex has particularly interesting magnetic properties that include weak intra-chain antiferromagnetic coupling at higher temperatures and a magnetic phase transition, at T N /6.1 K, to an ordered antiferromagnetic phase. This ordering is probably brought about by the hydrogen-bonding pathways joining the chains. Removal of water and acetic acid solvate molecules results in the loss of the long-range order. Detailed DC and AC magnetization studies, made over a wide range of applied magnetic fields and temperatures, show that below T N , there is a metamagnetic transition at approximately 1000 Oe, brought about by increasing the applied fields, from the antiferromagnetic phase to a canted-spin antiferromagnetic (weak ferromagnetic) phase. # 2003 Elsevier Science Ltd. All rights reserved. Keywords: Manganese(III); Carboxylate chain structures; Hydrogen-bonded sheets; Metamagnetism; Crystal structures 1. Introduction Studies of covalent ligand bridging in extended net- work coordination polymers and how this influences magnetic coupling and long-range order have increased enormously in recent years. The bridging groups CN  , C 2 O 4 2 , RCO 2  [1  /6] and poly-cyano ligands such as N(CN) 2  [7 /9] have received most attention. Less well studied, however, is magnetic order occurring via hydrogen-bonding pathways, but this is a growing field within supramolecular magnetochemistry, and a num- ber of examples have been discovered recently [10  /13]. Generally, the J values and T C (or T N ) values in such systems are very low with the ordering temperatures less than 10 K. However, we have noted a T C value of 23 K in a heterobimetallic Ni 3 Fe 2 cluster system in which well-ordered hydrogen-bonded (H 2 O) 7 arrays join the clusters [14]. We describe here a new polymeric carboxylate- bridged complex, {[Mn(m-OH)(m-OAc) 2 ] × /HOAc × /H 2 O} n (1 × /HOAc × /H 2 O), which displays long-range antiferro- magnetic order (T N /6.1 K) facilitated by hydrogen bonding, together with a field-induced metamagnetic transition. The desolvated material, 1, does not order magnetically. The solvated complex was discovered during attempts to link Mn 3 and Mn 4 carboxylate cluster complexes with pseudo-halide ligands, in this case dicyanonitrosomethanide (ONC(CN) 2  , dcnm  ), to form extended networks of clusters. The dcnm  group was not contained in the product. Similar work with dicyanamide (N(CN) 2  ) recently led to the simul- taneous discovery of a large manganese(III/IV) carbox- ylate-alkoxo cluster, [Mn 16 O 16 (OMe) 6 (OAc) 16 (MeOH) 3 - (H 2 O) 3 ] × /6H 2 O, which is a new example of a single molecule magnet (SMM), and a linear chain Mn III * Corresponding author. Tel.:  /61-3-9905-4512; fax:  /61-3-9905- 4597. E-mail address: keith.s.murray@sci.monash.edu.au (K. Murray). Polyhedron 22 (2003) 2161  /2167 www.elsevier.com/locate/poly 0277-5387/03/$ - see front matter # 2003 Elsevier Science Ltd. All rights reserved. doi:10.1016/S0277-5387(03)00180-3