Spin crossover properties of the [Fe(PM-BiA)2(NCS)2] complex -: Phases I and II

被引:113
作者
Létard, JF
Chastanet, G
Nguyen, O
Marcén, S
Marchivie, M
Guionneau, P
Chasseau, D
Gütlich, P
机构
[1] CNRS, UPR 9048, Grp Sci Mol, Inst Chim Mat Condensee, F-33608 Pessac, France
[2] Johannes Gutenberg Univ Mainz, Inst Anorgan Chem & Analyt Chem, D-55099 Mainz, Germany
来源
MONATSHEFTE FUR CHEMIE | 2003年 / 134卷 / 02期
关键词
spin crossover; iron(II); photomagnetism; kinetic relaxation;
D O I
10.1007/s00706-002-0537-0
中图分类号
O6 [化学];
学科分类号
0703 ;
摘要
In the present review, we reexamine the photomagnetic properties of the [Fe(PMBiA)(2)(NCS)(2)], cis-bis(thiocyanato)-bis[(N-2'-pyridylmethylene)-4-(aminobiphenyl)]iron(H), compound which exhibits, depending on the synthetic method, an exceptionally abrupt spin transition (phase I) with a very narrow hysteresis (T-1/2 down arrow = 168 K and T-1/2 up arrow = 173 K) or a gradual spin conversion (phase II) occurring at 190K. In both cases, light irradiation in the tail of the (MLCT)-M-1-LS absorption band, at 830 nm, results in the population of the high-spin state according to the light-induced excited spin-state trapping (LIESST) effect. The capacity of a compound to retain the light-induced HS information, estimated through the T(LIESST) experiment, is determined for both phases. Interestingly, the shape of the T(LIESST) curve is more gradual for the phase II than for the phase I and the T(LIESST) value is found considerably lower in the case of the phase II. The kinetics parameters involved in the photoinduced high-spin --> low-spin relaxation process are estimated for both phases. From these data, the experimental T(LIESST) curves are simulated and the particular influence of the cooperativity as well as of the parameters involved in the thermally activated and tunneling regions are discussed. The Light-Induced Thermal Hysteresis (LITH), originally described for the strongly cooperative phase I, is also reinvestigated. The quasi-static LITH loop is determined by recording the photostationary points in the warming and cooling branches.
引用
收藏
页码:165 / 182
页数:18
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