Controlled Synthesis and Magnetic Properties of 2D and 3D Iron Azide Networks _(infinity)~2[Fe(N_3)_2(4,4'-bpy)] and _(infinity)~3[Fe(N_3)_2(4,4'-bpy)]

摘要

Controlled synthesis transition metal complexes with mixed ligands has led to two new compounds with the same empirical formula [Fe(N_3)_2(4,4'-bpy)] (4,4'-bpy = 4,4'-bipyridine). The compound 2D-[Fe(N_3)_2(4,4'-bpy)] (I) contains end-on (EO)bridging azido ligands. It crystallizes in the orthorhombic crystal system, space group Cmmm (No. 65): a = 11.442(2) A, b = 15.181(3) A, c = 3.458(1) A, V = 600.8(2) A~3, and Z = 2. The compound 3D-[Fe(N_3)_2(4,4'-bpy)] (II) contains end-to-end (EE) azido bridges. It belongs to the tetragonal crystal system, space group P4_12_12 (No. 92): a = 8.132(2) A, b = 8.132(1) A, c = 16.708(3) A, V = 1104.9(5) A~3, and Z = 4. Crystals of I and II 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 low-field region, multiple transitions at T_(N1) = 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.