Isoconversional analysis of thermally stimulated events on pillared cyanometallates

Abstract

We report the analysis, by the advanced isoconversional method of Vyazovkin, of the thermal events of pyridine molecule loss and spin crossover occurring in the two-dimensional compounds of molecular formulas: Fe(Pyridine)2[Fe(CN)5NO] and Fe(Pyridine)2[Ni(CN)4]. Experimental thermogravimetric data were used to analyze the thermal evolution of pyridine molecules in both compounds. Calorimetry was used to study the spin crossover in Fe(Pyridine)2[Ni(CN)4], while SQUID magnetometric for Fe(Pyridine)2[Fe(CN)5NO]. The analysis of the effective activation energy of the pyridine loss process suggested that, in both compounds, the thermal evolution of these molecules is highly influenced by the particle size due to the occurrence of a structural transformation of the gate-opening type. The effective activation energy of the latter technique applied to compound Fe(Pyridine)2[Ni(CN)4] showed a behavior very similar to that expected for a solid–solid transition that occurs by the nucleation mechanism. The results obtained shed light on the way towards the application of the studied compounds in sensors and switches devises for molecular detection.