Phase transition study of bathophenanthroline and bathocuproine: a multitechnique approach

The thermal behaviour of bathophenanthroline and bathocuproine has been studied using several techniques, namely, differential scanning calorimetry and thermogravimetry. To determine their respective enthalpies of sublimation, vapor pressure measurements were carried out using different methods, such as Knudsen effusion mass loss/mass spectrometry, isothermal thermogravimetry, and a quartz crystal microbalance technique. Furthermore, the enthalpies of sublimation were determined by measuring the heat change of the sublimation process using high-temperature Calvet microcalorimetry. The results obtained in this work allowed the determination of the standard molar enthalpies of sublimation at 298.15 K, for bathophenanthroline and bathocuproine. The values obtained were (183.8 ± 2.2) kJ⋅mol−1 and (206.2 ± 2.8) kJ⋅mol−1, respectively. Additionally, the standard molar enthalpies of fusion were determined to be (30.4 ± 0.4) kJ⋅mol−1 and (26.5 ± 1.6) kJ⋅mol−1 for bathophenanthroline and bathocuproine, respectively. The analysis of the results allows a deeper understanding of the phase transition behavior for these compounds from the condensed to the gaseous phases, elucidating molecular decomposition and the inherent intermolecular forces governing the species.