Hydrogen-bonded supramolecular manganese(II) complexes with network and sheet structures bridged by terephthalate unit
摘要:
Two ID complexes [Mn(4-methylpyrazole)(3)(H2O)(tp)](n) (2) and [Mn(4-methylpyrazole)(4)(tp)](n) (3) (tp = terephthalate) were synthesized and characterized by means of X-ray analysis and magnetic studies. The molecular structure of 2 reveals that Mn(II) centers with asymmetric coordination surroundings are bridged by crystallographically different tp ligands, forming a ID chain. The ID coordination chains are interconnected by hydrogen bonds between free carboxylate oxygen atoms in a chain and hydrogens of pyrazole nitrogen atoms in neighboring chains, leading to a 3D framework. Compound 3 also exhibits a 1D coordination chain which is hydrogen-bonded to adjacent chains, providing a 2D sheet structure. Interestingly, the structures include intra- and interchain hydrogen bonds contributed from N-H groups of the capping 4-methylpyrazole ligands. Magnetic measurements show weak antiferromagnetic interactions with exchange coupling parameters of J = -0.018 cm(-1) for 2 and J = -0.062 cm(-1) for 3 through the extended tp ligand on the basis of an infinite chain model (H = -J Sigma S-i (.) Si+1). (c) 2005 Elsevier B.V. All rights reserved.