Assembly of iron(II)-triazole polymers from 1D chains to 3D interpenetrated frameworks: Syntheses, structures, and magnetic properties

By the reactions of FeX2 with alpha,omega-bis(1,2,4-triazol-1-yl)alkane ligands (X = ClO4-, BF4-, NCS-, and NCSe-), a series of novel iron(II) coordination, polymers have been synthesized and characterized. Complexes [Fe(btP)(3)](ClO4)(2) (1a), [Fe(btP)(3)](BF4)(2) (1b), and [Fe(btP)(2)(NCS)(2)] (2) (btp = 1,3-bis(1,2,4-triazol-1-yl)propane) are infinite 1D-linear chains. [Fe(btb)(3)](ClO4)(2) (3a) and [Fe(btb)(3)](BF4)(2) (3b) (btb = 1,4-bis(1,2,4-triazol-1-yl)butane) are 3-fold interpenetrated alpha-polonium cubic frameworks. The two sorts of btb ligands with different conformations alternately link to the Fe(II) centers in [Fe(btb)(2)(NCS)(2)]center dot H2O (4) to form a 3D interpenetrating architecture of CdSO4-like topology. When NCSe- instead of NCS- was used as the framework-regulator, a 2D grid layer [Fe(btb)(2)(NCSe)(2)]center dot 2H(2)O (5) was obtained. The counteranions, spacer length, and conformation of the alpha,omega-bis(1,2,4-triazol-1-yl)alkane ligands are responsible for the assembled topological architectures. Magnetic studies indicate that all of these iron(II) polymers retain a high-spin ground state upon cooling from 300 to 4 K.