Structure and Spin State of Iron(II) Assembled Complexes Using 9,10-Bis(4-pyridyl)anthracene as Bridging Ligand

Abstract

Assembled complexes, [Fe(NCX) 2 (bpanth) 2 ] n (X = S, Se, BH 3 ; bpanth = 9,10-bis (4-pyridyl)anthracene), were synthesized.The iron for the three complexes was in temperature-independent high spin state by 57 Fe Mössbauer spectroscopy and magnetic susceptibility measurement. X-ray structural analysis revealed the interpenetrated structure of [Fe(NCS) 2 (bpanth) 2 ] n . In the local structure around the iron atom, the coordinated pyridine planes were shown to be a parallel type, which is in accordance with the results investigated by density functional theory (DFT) calculation. This complex (X = S) has CH-π interactions between the H atom of coordinated pyridine and the neighboring anthracene of the other 2D grid. It was suggested that the interpenetrated structure was supported by the stabilization of CH-π interaction, and this intermolecular interaction forced the relatively unstable parallel structure. That is, the unstable local structure is compensated by the stabilization due to intermolecular interaction, which controlled the spin state as high spin state.

Spin-Crossover Complexes

“…For polynuclear SCO complex assemblies, Kosone and co-workers [17] investigate the substitution effect on the axial pyridine ligands in the 2D bilayer Hofmann-type Fe(II) coordination polymer and reveal steric and chemical pressure effects on SCO cooperativity and transition temperature. Iwai and co-workers [18] report a series of Fe(II) assembled complexes from a bidentate bridging ligand with different co-ligands. They indicate that the parallel configuration of coordinated pyridine rings in an FeN 6 coordination core favors the HS state.…”

Threefold Spiral Structure Constructed by 1D Chains of [[M(NCS)2(bpa)2]·biphenyl]n (M = Fe, Co; bpa = 1,2-bis(4-pyridyl)ethane)

“…Among them, we became interested in the complexes bridged by bis(pyridyl) type ligands, because these complexes easily form vacancies. We have studied SCO phenomenon for the complexes bridged by 1,2-bis(4-pyridyl)ethane [14][15][16][17][18], 1,3-bis(4-pyridyl)propane [19,20], 1,4-bis(4-pyridyl)benzene derivatives [21], and 1,4-bis(4-pyridyl)anthracene [22]. By changing the bridging ligand and guest molecule, the local structure is controlled to propeller, parallel type, or distorted propeller (Scheme 1).…”