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Site Directed Spin Labeling and EPR Spectroscopic Studies of Pentameric Ligand-Gated Ion Channels
Published on: July 4, 2016
Pressure effects on a spin-crossover monomeric compound [Fe(pmea)(SCN)(2)] (pmea =
Bao Li1, Rong-Jia Wei, Jun Tao
1State Key Laboratory of Physical Chemistry of Solid Surfaces and Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University, Xiamen 361005, People's Republic of China.
Abstract:
Spin-crossover (SCO) compounds are a sort of bistable material whose electronic and magnetic properties can be tuned by external physical stimuli, such as heat, light, and pressure. The title SCO compound [Fe(pmea)(NCS)(2)] (1; pmea = bis[(2-pyridyl)methyl]-2-(2-pyridyl)ethylamine) undergoes spin transition in such a way that it is an ideal candidate to investigate pressure effects on the SCO behavior. First, the spin transition is complete and abrupt so that the pressure-dependent spin transition should be remarkable. Second, the T(1/2) value under ambient pressure is 184 K, which guarantees that the SCO temperature under various pressures does not exceed that restrained by high-pressure devices. The magnetic data of compound 1 under different external pressures were analyzed through a known method, as reported by Gutlich, which gave an interaction parameter Gamma of 264(5) cm(-1) and a volume change DeltaV degrees (HL) of 32(3) A(3) molecule(-1) [HL represents a high-spin (HS) <--> low-spin (LS) transition], respectively. Meanwhile, the calculated entropy change DeltaS degrees (HL)(T) at 1 bar is 59.79 J mol(-1) K(-1), which is a typical value that drives the spin transition from a LS to HS state. The pressure effects on the SCO behavior of compound 1 reported here may provide information for a deep understanding of the correlation between pressure and spin transition.
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