Synthesis, crystal structures, and magnetic properties of three new iron complexes derived from 3,5-bis(pyridin-2-yl)-1,2,4-triazole

Two new iron(III) complexes and one iron(II) complex have been synthesized from the solvothermal reactions of FeCl3 center dot 6H(2)O with 3,5-bis(pyridin-2-yl)-1,2,4-triazole (Hbpt) in methanol or acetonitrile. KSCN acted as the reducing agent in the synthesis of iron(II) complex of 3. [FeCl3(Hbpt)(H2O)]center dot H2O (1) crystallizes in the triclinic space group P (1) over bar with a = 7.475(1), b = 9.468(2), c = 12.309(2) angstrom: alpha = 73.880(2), beta - 74.746(2), gamma = 81.849(2)degrees, V = 805.2(2) angstrom(3), Z = 2. [Fe-2(bpt)(2)Cl-4] (2): orthorhombic space group Pnnm with a = 9.895(2), b = 10.632(2), c = 13.195(2) angstrom, V = 1388.1(4) angstrom(3) Z = 2. [Fe-2(bpt)(2)(MeOH)(2)Cl-2](3): orthorhombic space group Pbca with a = 14.4204(16), b = 9.8737(11), c = 19.792(2) angstrom, V = 2818.1(5) angstrom 3, Z = 4. 1 features the first structurally characterized metal complex of the neutral Hbpt ligand in which the Hbpt ligand adopts an unprecedented zwitterionic form. 2 shows a neutral dinuclear iron(III) complex and the [Fe-2(bpt)(2)](4+) unit is ideally planar. The two iron(III) ions separated by a distance of 4.408(2) angstrom are doubly triazolate-bridged. Each dimeric unit is connected with six other dimeric ones via the bifurcated C-H... Cl hydrogen bonds, these connections extend the dimeric moieties into a three-dimensional molecular architecture. 3 is a neutral centrosymmetric dinuclear Fe-II complex, in which intermolecular moderate O-H center dot center dot center dot N hydrogen bonding interactions between the methanol molecules and 4-position nitrogen atoms of the triazolato groups extend the dinuclear species into a two-dimensional supramolecular architecture of (4,4) topology. Magnetic studies indicate there exists an antiferromagnetic spin coupling in Fe-2(III) and Fe-2(II) units via the double triazolate bridges in 2 and 3.