Antiferromagnetic Alternating and Homogeneous Manganese−Azido Chains:  Structural Characterization and Magnetic Behavior of Two New One-Dimensional [Mn(L)2(μ1,3-N3)2] n Compounds (L = 3-Ethylpyridine and 2-Hydroxypyridine)

The X-ray structures of the two monodimensional systems of formula [Mn(L)2(N3)2] n in which L = 3-ethylpyridine (1) or 2-hydroxypyridine (2) have been determined. Crystal data: 1, formula C14H18MnN8, monoclinic P21/n, a = 10.210(5) Å, b = 15.460(6) Å, c = 10.880(4) Å, β = 95.86(3)°, Z = 4; 2, formula C10H10MnN8O2, triclinic P1̄, a = 5.218(2) Å, b = 6.841(3) Å, c = 9.469(4) Å, α = 79.30(4)°, β = 87.85(4)°, γ = 75.85(4)°, Z = 1. The two compounds consist of chains 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 antiferromagnetic interaction with J values −13.8/−11.7 and −7.0 cm-1 for 1 and 2, respectively. The deformation of the Mn2(N3)2 eight-membered rings from planarity to chair conformation has been correlated to the magnitude of the antiferromagnetic coupling constant by means of extended Hückel MO calculations.