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Photomagnetism of a sym‐cis ‐Dithiocyanato Iron(II) Complex with a Tetradentate N , N ′‐Bis(2‐pyridylmethyl)1,2‐ethanediamine Ligand
Author(s) -
Létard JeanFrançois,
Asthana Saket,
Shepherd Helena J.,
Guionneau Philippe,
Goeta André E.,
Suemura Naohiko,
Ishikawa Ryuta,
Kaizaki Sumio
Publication year - 2012
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201102637
Subject(s) - spin crossover , metastability , excited state , spin transition , spin states , chemistry , crystallography , atmospheric temperature range , atomic physics , thermodynamics , physics , inorganic chemistry , organic chemistry
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.