Structural characterization and magnetic behaviour of the ferro-antiferromagnetic alternating manganese-azido chain [Mn(3-Et,4-Mepy)(2)(mu-N-3)(2)](n) (3-Et,4-Mepy = 3-ethyl-4-methylpyridine)

The ligands 3-ethyl-4-methylpyridine (3-Et,4-Mepy) and azide coordinate to Mn-II forming an alternating chain with the formula [Mn(3-Et,4-Mepy)(2)(mu- N-3)(2)](n). This compound crystallizes in the space group P-1. The compoun d consists of chains of octahedrally coordinated manganese atoms alternatel y bridged by double end-to-end (mu(1,3)) and double end-on (mu(1,1)) azido bridges, which results in a structurally and magnetically alternating chain . The 3-ethyl-4-methylpyridine ligands are arranged trans, completing the s ix-fold coordination spheres of the manganese atoms. The Mn-Mn distances ar e distinctly different: Mn(1)-Mn(1A) = 5.149(3) Angstrom (double end-to-end azido bridge) and Mn(1)Mn(1B) = 3.402(2) Angstrom (double end-on azido bri dge). The magnetic properties of the compound, as studied in the temperatur e range 300-4 K, show bulk antiferromagnetic interaction. Fitting of the ma gnetic data by using an equation for alternating ferro-antiferromagnetic S = 5/2 1-D systems gives the parameters J(AF) = -13.7(1) cm(-1), J(F) = 2.4( 1) cm(-1), g = 2.036(2).