SYNTHESIS, CRYSTAL-STRUCTURE AND MAGNETIC-PROPERTIES OF AN ISOPHTHALATE-BRIDGED MANGANESE(II) CHAIN COMPLEX

An isophthalate-bridged manganese(II) chain complex of [Mn-2(phen)(4)( m-phth)](n)[ClO4](2n). 2nH(2)O, where phen is 1,10-phenanthroline and m-phth is isophthalate (dianion of benzene-1,3-dicarboxylic acid), has been prepared and characterized by X-ray crystallography and magnetic measurements, It crystallizes in the triclinic system, space group <P (1)over bar>, with a = 14.651(1), b = 16.679(7), c = 13.561(4) Angstro m, alpha = 101.46(3), beta = 113.91(2), delta = 65.52(3)degrees and Z = 2. The structure consists of cationic isophthalate-bridged [Mn-2(phe n)(4)(m-phth))](2+) chains, non-coordinated perchlorate anions and cry stallized water molecules. Each isophthalate is bound to four manganes e atoms through carboxylate oxygens with the syn-syn bridging mode, af fording manganese(II) pairs which are Linked by the isophthalate group to yield a one-dimensional chain running along the a axis. The intrac hain Mn ... Mn separations are 4.86 and 4.66 Angstrom (through the dou ble carboxylate bridges) and 7.16 Angstrom (the shortest distance thro ugh the bridging isophthalate), respectively. The manganese(II) ion di splays a distorted octahedral coordination being linked to four nitrog en atoms of two phen ligands and two oxygen atoms of two carboxylate g roups from two isophthalate ligands. The variable temperature magnetic susceptibility of the title complex in the temperature range 1.5-300 K has been interpreted in terms of an Mn(II) dimer with a molecular he ld approximation, the values obtained for J, g(fixed) and zJ' being 3. 23 cm(-1), 2.00 and -0.35 cm-(1), respectively, indicating a weakly fe rromagnetic exchange coupling within the Mn(II) dimer with double carb oxylates in syn-syn conformation.