ANTIFERROMAGNETIC ALTERNATING AND HOMOGENEOUS MANGANESE-AZIDO CHAINS - STRUCTURAL CHARACTERIZATION AND MAGNETIC-BEHAVIOR OF 2 NEW ONE-DIMENSIONAL [MN(L)(2)(MU(1,3)-N-3)(2)](N) COMPOUNDS (L = 3-ETHYLPYRIDINE AND 2-HYDROXYPYRIDINE)

The X-ray structures of the two monodimensional systems of formula [Mn (L)(2)(N-3)(2)](n) in which L = 3-ethylpyridine (1) or 2-hydroxypyridi ne (2) have been determined. Crystal data: 1, formula C14H18MnN8, mono clinic P2(1)/n, a = 10.210(5) Angstrom, b = 15.460(6) Angstrom, c = 10 .880(4) Angstrom, beta = 95.86(3)degrees, Z = 4; 2, formula C10H18MnN8 O2, triclinic P (1) over bar, a = 5.218(2) Angstrom, b = 6.841(3) Angs trom, c = 9.469(4) Angstrom, alpha = 79.30(4)degrees, beta = 87.85(4)d egrees, gamma = 75.85(4)degrees, Z = 1. The two compounds consist of c hains of manganese atoms bridged by double end-to-end azido bridges. 1 consists of a structurally and magnetically alternated chain whereas 2 is a homogeneous system. Magnetic measurements show antiferromagneti c interaction with J values -13.8/-11.7 and -7.0 cm(-1) for 1 and 2, r espectively. The deformation of the Mn(N-3)(2) eight-membered lines fr om planarity to chair conformation has been correlated to the magnitud e of the antiferromagnetic coupling constant by means of extended Huck el MO calculations.