Pressure effects on a spin-crossover monomeric compound [Fe(pmea)(SCN) ₂] (pmea = bis[(2-pyridyl)methyl]-2-(2-pyridyl)ethylamine)

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 highpressure devices. The magnetic data of compound 1 under different external pressures were analyzed through a known method, as reported by G̈utlich, which gave an interaction parameter Γ of 264(5) cm^-1 and a volume change △V^o-HL of 32(3) Å 3 molecule^-1 [HL represents a high-spin (HS)↔low-spin (LS) transition], respectively. Meanwhile, the calculated entropy change △S-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.