Two-dimensional coordination polymers with one-dimensional magnetic chains: Hydrothermal synthesis, crystal structure, and magnetic and thermal properties of (2)(infinity)[MCl2(4,4 '-bipyridine)] (M = Fe, Co, Ni, Co/Ni)

Two-dimensional transition-metal coordination polymers (2)(infinity)[MCl2(b py)] (M = Fe, Co, Ni; Co/Ni, bpy = 4, 4'-bipyridine) have been synthesized in superheated water solutions. The hydrothermal routes resulted in four co mpounds (2)(infinity)[FeCl2(bpy)](I), (2)(infinity)[CoCl2(bpy)](II), (2)(in finity)[NiCl2(bpy)](III), and (2)(infinity)[(Co/Ni)Cl-2(bpy)](IV). Compound s I-IV are isostructural and belong to orthorhombic crystal system, spate g roup Cmmm (No. 65). Crystal data for I: a = 11.929(2) Angstrom, b = 11.447( 2) Angstrom, c = 3.638(1) Angstrom, V = 496.77(18) Angstrom(3), Z = 2 Cryst al data for II: a 11.993(2) Angstrom, b = 11.374(2) Angstrom, c = 3.611(1) Angstrom, V = 492.57(18) Angstrom(3), Z = 2. The structure is a noninterpen etrating two-dimensional network containing transition-metal centers octahe drally coordinated by four bridging chlorine and two bpy ligands at trans p ositions. The adjacent bpy ligands within a single layer are parallel to ea ch other at a distance of 3.6 Angstrom. Spontaneous antiferromagnetic order ing was found in all compounds from the magnetic susceptibility chi(T) meas urements under low fields. The transition temperatures are 10.0, 5.0, 8.5, and 7.5 K, for I, II, III, and IV, respectively. The mu(eff) values yielded from fitting the high temperature chi(T) indicate the high spin states of metal ions. In addition, a metamagnetic transition was observed in the fiel d-dependent magnetization measurement for all four compounds. The magnetic properties observed in this system are attributed to the ferromagnetic intr achain M-M exchange interaction through the Cl-2 bridges along the c axis a nd the antiferromagnetic interchain interaction between the M ions. TGA stu dies indicate that all four compounds are thermally stable with an on-set t emperature of weight loss greater than 400 degrees C.