Spin Crossover and High-Spin State in Fe(II) Anionic Polymorphs Based on Tripodal Ligands.

Two new mononuclear Fe(II) polymorphs, [(CH)N][Fe(pyC-OEt)(NCS)] () and [(CH)N][Fe(pyC-OEt)(NCS)] () (pyC-OEt = tris(pyridin-2-yl)ethoxymethane), have been synthesized and characterized by single-crystal X-ray diffraction, by magnetic and photomagnetic measurements, and by detailed variable-temperature infrared spectroscopy. The molecular structure, in both complexes, is composed of the same anionic [Fe(pyC-OEt)(NCS)] complex (two units for and one unit for ) generated by coordination to the Fe(II) metal center of one tridentate pyC-OEt tripodal ligand and three terminal κ-SCN coligands. Magnetic studies revealed that polymorph displays a high-spin (HS) state over the entire studied temperature range (300-10 K), while complex exhibits an abrupt and complete spin crossover (SCO) transition at ca.

One-Dimensional Thiocyanato-Bridged Fe(II) Spin Crossover Cooperative Polymer With Unusual FeNS Coordination Sphere.

We present here a novel example of spin crossover phenomenon on a Fe(II) one-dimensional chain with unusual NS coordination sphere. The [{Fe(tpc-OMe)(NCS)(μ-NCS)} ] (1) compound was prepared using the tridentate tpc-OMe ligand (tpc-OMe = tris(2-pyridyl)methoxymethane), FeCl·4HO, and the KSCN salt. Crystallographic investigations revealed that the Fe(II) ions are connected by a single bridging NCS ligand (μ-κN:κS-SCN coordination mode) to afford a zigzag neutral chain running along the [010] direction, in which the thiocyanato bridging groups adopt a cis head-to-tail configuration.

On the Magnetic Coupling and Spin Crossover Behavior in Complexes Containing the Head-to-Tail [Fe(μ-SCN)] Bridging Unit: A Magnetostructural Experimental and Theoretical Study.

A new dinuclear complex [{Fe(tpc-OBn)(NCS)(μ-NCS)}] (1) based on the tripodal tpc-OBn ligand (tpc-OBn = tris(2-pyridyl)benzyloxymethane), containing bridging μ-κN:κS-SCN and terminal κN-SCN thiocyanate ligands, has been prepared and characterized by single crystal X-ray diffraction, magnetic studies, and DFT theoretical calculations. This complex represents the first example of dinuclear Fe complex with double μ-κN:κS-SCN bridges in a head-to-tail configuration that exhibits ferromagnetic coupling between metal ions (J = +1.08 cm).