title: Photomagnetism of a sym-cis-dithiocyanato iron(II) complex with a tetradentate N,N'-bis(2-pyridylmethyl)1,2-ethanediamine ligand.
abstract: A comprehensive study of the magnetic and photomagnetic behaviors of cis-[Fe(picen)(NCS)(2) ] (picen = N,N'-bis(2-pyridylmethyl)1,2-ethanediamine) was carried out. The spin-equilibration was extremely slow in the vicinity of the thermal spin-transition. When the cooling speed was slower than 0.1 K  min(-1), this complex was characterized by an abrupt thermal spin-transition at about 70 K. Measurement of the kinetics in the range 60-70 K was performed to approach the quasi-static hysteresis loop. At low temperatures, the metastable HS state was quenched by a rapid freezing process and the critical T(TIESST) temperature, which was associated with the thermally induced excited spin-state-trapping (TIESST) effect, was measured. At 10 K, this complex also exhibited the well-known light-induced excited spin-state-trapping (LIESST) effect and the T(LIESST) temperature was determined. The kinetics of the metastable HS states, which were generated from the freezing effect and from the light-induced excitation, was studied. Single-crystal X-ray diffraction as a function of speed-cooling and light conditions at 30 K revealed the mechanism of the spin-crossover in this complex as well as some direct relationships between its structural properties and its spin state. This spin-crossover (SCO) material represents a fascinating example in which the metastability of the HS state is in close vicinity to the thermal spin-transition region. Moreover, it is a beautiful example of a complex in which the metastable HS states can be generated, and then compared, either by the freezing effect or by the LIESST effect.
authors.affiliation: CNRS, Université Bordeaux, ICMCB, Groupe des Sciences Moléculaires, 87 Av. Doc. A. Schweitzer, 33608 Pessac, France. letard@icmcb-bordeaux.cnrs.fr
authors.forename: Jean-François
authors.initials: JF
authors.lastname: Létard
authors.forename: Saket
authors.initials: S
authors.lastname: Asthana
authors.forename: Helena J
authors.initials: HJ
authors.lastname: Shepherd
authors.forename: Philippe
authors.initials: P
authors.lastname: Guionneau
authors.forename: André E
authors.initials: AE
authors.lastname: Goeta
authors.forename: Naohiko
authors.initials: N
authors.lastname: Suemura
authors.forename: Ryuta
authors.initials: R
authors.lastname: Ishikawa
authors.forename: Sumio
authors.initials: S
authors.lastname: Kaizaki