Observation of the First Spin Crossover in an Iron(II) Complex with an S6 Coordination Environment: Tris[bis(N, N‐diethylamino)carbeniumdithiocarboxylato]iron(II) Hexafluorophosphate. Issue 68 (26th November 2018)

• Record Type: Journal Article
• Authors: Sugaya, Tomoaki; Fujihara, Takashi; Naka, Takashi; Furubayashi, Takao; Matsushita, Akiyuki; Isago, Hiroaki; Nagasawa, Akira
• Is Part Of: Chemistry. Volume 24:Issue 68(2018)
• Page Start: 17955
• Page End: 17963
• Publication Date: 2018-11-26
• Subjects: iron -- magnetic properties -- spin crossover -- sulfur -- zwitterions; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201803330
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: For the first time, the spin‐crossover (SCO) phenomenon has been observed in an Fe II –S6 system in a tris(chelate)‐type iron(II) complex with a zwitterionic sulfur donor bidentate, bis( N, N ‐diethylamino)carbeniumdithiocarboxylate (EtL), [Fe II (EtL)3 ](PF6 )2 (1 ), as synthesized by the reaction of a precursor complex [Fe II (CH3 CN)6 ](PF6 )2 with EtL. In the solid state, the high‐spin (HS) d 6 state at ambient temperature and the low‐spin (LS) d 6 state at temperatures lower than approximately 240 K were evidenced by magnetic measurements with SQUID and Mössbauer spectra in the temperature range 4–290 K. X‐ray analyses of the crystals at various temperatures disclosed that the distorted trigonal prismatic coordination environments essentially do not change; however, contraction of Fe−S distances by approximately 10 % (0.22 Å), ordering of alkyl groups in EtL and PF6 − counteranions, and formation of significant intermolecular S⋅⋅⋅S interactions between adjacent molecules (average distances of 3.59 Å) take place during the transition from the HS to the LS state. A large decrease in the volume of the formula unit (78.1 Å 3 ) might be responsible for the large activation barrier, thereby resulting in a slow phase transition upon cooling. Abstract : Taking iron(II) for a spin : The spin‐crossover (SCO) behavior of iron(II) complexes with an S6 coordination sphere is presented for the first time. A significant feature is a large volume contraction (78.1 Å 3 per formula unit at 150 K versus that at 298 K), which is not caused by the intrinsic structural change in the cationic iron(II) complex itself.