Spin crossover (SCO) iron(II) coordination polymer chain: Synthesis, structural and magnetic characterizations of [Fe(abpt)2(μ-M(CN)4)] (M = PtII and NiII)

New iron(II) coordination polymeric neutral chain of formula [Fe(abpt)2(μ-M(CN)4)], with M = PtII (1), NiII (2) and abpt = 4-amino-3,5-bis(pyridin-2-yl)-1,2,4-triazole, have been synthesized and characterized by infrared spectroscopy, X-ray diffraction and magnetic measurements. The two compounds are isostructural as deduced from a Rietveld analysis of X-ray powder diffraction data of 2 simulated from the single crystal structure of 1. The crystal packing of 1 is formed by regular chains running along the crystallographic [−1 0 1] direction where the planar [Pt(CN)4]2− anion acts as a μ2-bridging ligand via two nitrogen atoms of two different trans cyano groups, while the two abpt molecules act as chelating ligands. Along the neutral chains, the Fe⋯Pt distances are imposed by the cyano groups of the [Pt(CN)4]2− moiety (5.027 and 5.022 Å at 294 and 150 K, respectively), leading to Fe⋯Fe intrachain distances of 10.055 and 10.045 Å at 294 and 150 K, respectively. The thermal dependence of the product of the molar magnetic susceptibility times the temperature (χmT) for compound 1 shows a constant value close to 0.2 emu K mol−1 in the temperature range 10–300 K in the cooling and warming scans. Above 300 K, compound 1 shows a SCO transition from the LS to the HS configuration although the transition is not fully achieved at 400 K.

Graphical abstractTwo iron(II) coordination neutral chain of formula [Fe(abpt)2(μ-M(CN)4)] (M = PtII and NiII) have been synthesized and structurally characterized. Both compounds exhibit SCO transition transitions above room temperature.Figure optionsDownload full-size imageDownload as PowerPoint slide