A novel mixed-valence manganese(II,III) complex of [Mn 4(sal) 4(H 2O) 4(py) 8] n[salH] 2 n·4 npy in an infinite chain (salH 2 = salicyclic acid; py = pyridine)

Abstract

A novel mixed-valence (II, III) infinite chain manganese complex [Mn 4(sal) 4(H 2O) 4(py) 8] n [salH] 2 n ·4 npy with salicyclate bridging ligands has been prepared and characterized by X-ray crystallography and magnetic spectroscopic measurements. It crystallizes in the triclinic system, space group P 1 with a = 12.248(2), a = 14.045(2), c = 15.606(2) A ̊ , α = 94.15(1), β = 92.14(1), γ = 112.03(1)°, Z = 1 and V = 2476.0(6) A ̊ 3 . The structure was solved by direct methods (MULTAN) and refined by lest-squares methods to residual R( R w) values of 0.059(0.064). The structure consists of a mixed-valence (II, III) manganese infinite chain of chemical formula [MN 4(sal) 4(H 2O 4(py) 8] n 2 n+ containing a tetranuclear repeat unit, together with 2 nsalH − and 4 npy. In the chain structure, all Mn(II) and Mn(III) ions bridged by salicylate carboxylate groups in a syn-anti configuration are arranged alternately and are six-coordinate with O 4N 2 atoms. Both Mn2 and Mn3 are located in symmetric centers. The sal 2− groups linking the Mn(II) and MN(III) ions have a μ− η 3-bridgin mode. Magnetic susceptibility data have been measured in the temperature range 1.6–301 K. The carboxylate bridge could only mediate a very weak antiferromagnetic exchange interaction and the magnetic behavior is better explained by a single-ion zero-field splitting model. The X-band EPR spectrum of the complex exhibits a six-line manganese hyperfine pattern centered at g = 1.998, A = 97 G.