New alternating ferro- and antiferromagnetic, one-dimensional manganese(II) azide complex, [Mn(dpa)(N-3)(2)] - Crystal structure and spectroscopic and magnetic properties

The synthesis, crystal structure, and spectroscopic and magnetic properties of a new alternating ferro- and antiferromagnetic, one-dimensional mangane se(II) azide complex, [Mn(dpa)(N-3)(2)] (where dpa is the 2,2'-dipyridylami ne ligand), are reported. The compound's crystal structure has been resolve d at room temperature. The complex crystallizes in the monoclinic P2(1)/c s pace group, with a = 7.089(2), b = 19.090(4), and c = 9.682(4) Angstrom, be ta = 104.61(2) degrees, and Z = 4. The structure consists of neutral chains in which each Mn-II cation is alternatively bridged by two end-on and two end-to-end azido bridges. The octahedral coordination of the metallic catio n is completed by two dpa ligand nitrogen atoms. Reflectance measurements c onfirm the hexacoordination of the Mn-II ions in the complex. The ESR spect ra at room temperature and at 4.2 K are isotropic, with a mean g-value of 2 .010(1). Magnetic data were analyzed on the basis of an alternating ferro- and antiferromagnetic Heisenberg chain of Mn-II ions. The J-exchange parame ters found are 64.3 and -75.7 K. A spin canting phenomenon has been observe d in this compound, with a remnant magnetization which vanishes above 15 K. Magnetostructural correlations in manganese(II) systems of alternating mag netic sign are discussed.