Controlled synthesis and magnetic properties of 2D and 3D iron azide networks ∞2[Fe(N3)2(4,4′-bpy)] and ∞3[Fe(N3)2(4,4′-bpy)]

Controlled synthesis of transition metal complexes with mixed ligands has led to two new compounds with the same empirical formula [Fe(N-3)(2)(4,4'-bpy)1 (4,4'-bpy = 4,4'bipyridine). The compound 213[Fe(N-3)(2)(4,4'-bpy)1 (1) contains end-on (EO) bridging azido ligands. It crystallizes in the orthorhombic crystal system, space group Cmmm (No. 65): a = 11.444(2) Angstrom. b = 15.181(3) Angstrom. c = 3.458(1) Angstrom, V = 600.8(2) Angstrom(3), and Z = 2. The compound 3D-[Fe(N-3)(2)(4,4'-bpy)] (11) contains end-to-end (EE) azido bridges. It belongs to the tetragonal crystal system, space group P4(1)2(1)2 (No. 92): a = 8.132(t) Angstrom. b = 8.132(1) Angstrom, c = 16.708(3) Angstrom, V = 1104.9(5) Angstrom(3), and Z = 4. Crystals of I and 11 have been grown by the diffusion method. Phase-pure samples of both compounds have been obtained by means of an optimal solution synthesis. Spontaneous long-range magnetic ordering was found in both I and II, with I being a metamagnet, and II being a ferromagnet. For I, in the lowfield region, multiple transitions at T-NI 41 = 20 K and T-N2 = 5 K were observed, and these indicated the existence of Fe moment reorientation. Heat capacity measurements on II confirmed ferromagnetic transition at T-c = 20 K.