SYNTHESIS, CRYSTAL-STRUCTURE AND MAGNETIC-BEHAVIOR OF A LINEAR TRINUCLEAR AND AN INFINITE CHAIN MIXED-VALENCE MANGANESE(II,III) COMPLEX

Two mixed valence manganese(II,III) salicylate complexes [Mn-3(sal)(2) (salH)(2)(H2O)(4)(4-Me-py)(6)] [Mn(sal)(2)(4-Me-py)(2)].2(4-Mepy) (1) and [{Mn-2 al)(2)(im)(2)(CH3OH)(4)}(n)][Mn(sal)(2)(py(2))](n) (2), whe re H(2)sal = salicylic acid, im = imidazole and py = pyridine, have be en prepared and characterized by means of X-ray crystallography and ma gnetic measurements. Complex 1 crystallizes in the monoclinic system, space group C2/c, with a = 36.737(4), b = 10.595(4), c = 28.041(5) Ang strom, beta = 111.337(9)degrees, V = 10166(3) Angstrom(3) and Z = 4, w hile 2 crystallizes in the triclinic system, space group P1, with a = 9.060(1), b = 10.238(2), c = 15.693(5) Angstrom, alpha = 103.07(2), be ta = 100.50(2), gamma = 109.47(1)degrees, V = 1283.1(2) Angstrom(3) an d Z = 1. The structures were solved by direct methods and refined by l east-squares methods to R (Rw) values of 0.046 (0.046) and 0.040 (0.04 2) for 1 and 2, respectively, The structure of 1 is composed of a line ar trinuclear mixed valence manganese( II,III,II) cationic unit [Mn-3( sal)(2)(salH)(2)(H2O)(4)(4-Me-py)(6)](+) with two bridging sal(2-) lig ands, a monomeric manganese(III) anionic unit [Mn(sal)(2)(4-Me-py)(2)] (-) and two 4-Me-py molecules. The structure of 2 consists of two dist inct ionic units, One of them is a polymeric chain formed by the catio nic unit [Mn-2(sal)(2)(im)(2)(CH3OH)(4)](+), and in the chain Mn(II) a nd Mn(III) ions are arranged alternately and bridged with sal(2-) liga nds. The other is a monomeric anionic unit [Mn(sal)(2)(py(2))](-). All Mn ions of the structures are six-coordinate and each sal(2-) group h as a mu-eta(3)-sal bridging mode, The magnetic behavior of the two com plexes shows that the salicylate carboxylate bridge mediates a weakly antiferromagnetic exchange interaction.