Structures and spin states of crystalline [Fe(NCS)(2)L-2] and [FeL3](2+) complexes (L = an annelated 1,10-phenanthroline derivative)

摘要

The phase behaviour and spin states of [Fe(NCS)(2)(dpq)(2)] (1; dpq = dipyrido[3,2-f: 2',3'-h] quinoxaline), [Fe(NCS)(2)(dppz)(2)] (2; dppz = dipyrido[3,2-a: 2'3'-c] phenazine) and [Fe(NCS)(2)(dppn)(2)] (3; dppn = dipyrido[3,2-a:2'3'-c] benzophenazine) have been investigated. Solvent-free 1 and 2 are isostructural and low-spin in the crystalline state, in contrast to previously published 2 center dot py (py = pyridine) which exhibits a hysteretic spin-crossover (SCO) transition near 140 K. The inactivity of 1 and 2 towards SCO may relate to their more crowded intermolecular lattice environment, particularly two very short intermolecular anion center dot center dot center dot pi contacts involving the NCS- ligands. Two solvate phases of 1 are also described, including 1.2py which undergoes gradual SCO with T-1/2 ca. 188 K. Bulk samples of 2 and 3 are predominantly low-spin and isostructural with the crystals of 2 by powder diffraction, but bulk samples of 1 contain an extra phase that exhibits hysteretic SCO, but was not crystallographically characterised. Crystal structures of low-spin [Fe(dppz)(3)][ClO4](2) (4) and a solvate of [Fe(dppn)(3)][BF4](2) (5) are also described, which are the first homoleptic complexes of these ligands to be crystallographically characterised.