PREPARATION, CRYSTAL-STRUCTURE, MAGNETIC AND EPR PROPERTIES OF A HEPTACOORDINATED MANGANESE(II) CHAIN OF [MN(BIPY) (H2O) (TBD)](N) (H2TBD EQUALS TRANS-2-BUTENE DIACID, BIPY EQUALS 2,2'-BIPYRIDINE)

An infinite zigzag chain manganese(II) complex [Mn(bipy) (H2O) TBD)](n ) (bipy = 2,2'-bipyridine; H2TBD = trans-2-butene diacid) has been pre pared and characterized by single-crystal X-ray diffraction, and magne tic measurements. The structure was solved by direct methods and refin ed by least-squares methods to R(Rw) values of 0.031 (0.042). Each TBD is bound to two manganese(II) ions through carboxylate oxygens, affor ding the manganese(II) ions bridged by TBD group to yield a infinite c hain running along the n axis. The intrachain Mn...Mn separation is 9. 05 Angstrom, while the shortest interchain Mn...Mn distance is 5.86 An gstrom. The manganese(II) ion displays a distorted pentagonal bipyrami d coordination by virtue of a bidentate bipyridine, two carboxylate gr oups of two TBD and a H2O molecule. The variable temperature magnetic susceptibility of the title complex in the temperature range 3.3-302 K has been interpreted in terms of Heisenberg chain model with a molecu lar field, the values obtained for J,g and zJ' being: 0.58 cm(-1), 2.0 1, and -0.09 cm(-1), respectively, indicating weakly antiferromagnetic intra-and interchain exchange interactions. The x-band EPR spectrum o f the complex exhibits a six-line manganese hyperfine pattern centered at g = 2.001, A = 94.5 G, together with five ''forbidden'' hyperfine doublets. Copyright (C) 1996 Elsevier Science Ltd