Crystal structure of [Fe(L-1)(2)](ClO4)(2).H2O having (FeN6)-N-II coordination [L-1=2,6-bis(pyrazol-1-ylmethyl)pyridine]

The structure of the compound [Fe(L-1)(2)](ClO4)(2).H2O (1) [L-1 = 2,6-bis( pyrazol-1-ylmethyl)pyridine] has been determined by X-ray crystallography a t approximate to 130 K. Temperature-dependent magnetic susceptibility and M ossbauer spectral studies reveal that the iron atom in I is in the high-spi n state at room temperature and in the low-spin state at low temperature, w hereas in [Fe(L-2)(2)] (ClO4)(2).H2O (2) and [Fe(L-3)(2)](ClO4)(2).H2O (3) [L-2 = 2,6-bis(3,5-dimethylpyrazole-1-ylmethyl)pyridine and L-3 = 2-(pyrazo l-lylmethyl)-6-(3,5-dimethylpyrazol-1-ylmethyl)pyridine] the iron atom is i n the high-spin state at both the temperatures [Mahapatra S, Mukherjee R, P olyhedron 12 (1993) 1603]. The metal-ligand bond distances in 1 have been c ompared with those of 3, determined at approximate to 173 K [ Mahapatra S, Butcher R J, Mukherjee, R, J chem Soc, Dalton Trans (1993) 3723]. The Fe-N- pyridine and Fe-N-pyrazole bond distances in I are shorter by similar to0.2 3 Angstrom and similar to0.14 Angstrom, respectively, than those for the hi gh-spin complex 3, revealing its low-spin character. Moreover, a noticeable variation of the N-Fe-N angles, leading to a more regular shape of the (Fe N6)-N-II octahedron in 1, is observed.