Abstract
A polymeric chain spin-crossover (SCO) compound [Fe(NH2trz)3](NO3)2 was embedded in the pores of mesoporous silica MCM-41, which yielded an M@S composite. The obtained material was characterized by infrared spectrometry, powder X-ray diffractometry, gas sorption studies, electron microscopy, and atomic absorption. The temperature-induced SCO behavior of the composite was monitored by temperature-variable magnetic measurement. The results indicate that the spin transition curve of the composite was evidently shifted to a higher temperature in comparison to bulk [Fe(NH2trz)3](NO3)2. The shift in the transition temperature for M@S [versus bulk [Fe(NH2trz)3](NO3)2] amounted to Tc↑ = 362 K [347 K] and Tc↓ = 327 K [314 K] (magnetic data). The significant difference in the SCO behavior of [Fe(NH2trz)3](NO3)2 when embedded in the MCM-41 matrix may be attributed to the strengthened cooperativity of compound S and the nano-confinement pressure of SiO2 walls.
Highlights
(S)chains chainswere were embedded in cylindrical the cylindrical of MCM-41 and
The amount of SCO compound S was determined from the Fe analysis by atomic absorption spectroscopy (AAS)
A composite material M@S comprised of the 1D SCO complex [Fe(NH2 trz)3 ](NO3 )2 and MCM-41 was successfully prepared
Summary
The magnetic properties of spin-crossover (SCO) compounds [1,2,3] are affected by physical and chemical conditions, such as light, heat, pressure, magnetic field, or solvent (guest) molecules [4,5,6]. Several Fe(II) SCO compounds were synthesized or embedded in matrices, such as MOFs [18], SiO2 [19], and Ni [20] These investigations indicated that the spin transition behavior of an SCO compound is dependent on its own natural character, but is influenced by the matrix surrounding the particles. It was shown that the spin transition behavior of SCO complexes shifted to a lower temperature through the encapsulation of MIL-101 [18] or C70 [24]. The presence of crystal H2O strongly influenced the confinement effect of MCM-41, and the dehydration of trapped [Fe(Htrz)3](BF4)2∙H2O in the MCM-41 pores would largely raise the spin of trappedtemperature. [Fe(Htrz)3 ](BF in the MCM-41 pores would largely to raise theSCO spincompounds transition This matrix effect is applicable other temperature.
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