Influence of High Pressure on the Local Order and Dynamical Properties of the Selected Azole Antifungals

Dielectric studies under various temperature (T) and pressure (p) conditions on five active pharmaceutical ingredients (APIs) with antifungal properties-itraconazole (ITZ), posaconazole (POS), terconazole (TER), ketoconazole (KET), and fluconazole (FLU)-were carried out. We have thoroughly studied the connection between the pressure coefficient of the glass transition temperature (dTg/dp) and the activation volume of both relaxation modes (ΔVα, ΔVδ/α') with respect to the molecular weight (Mw) or molar volume (Vm) in these systems. Besides, high pressure data revealed that the time scale separation between α- and δ- or α'-processes increases with pressure in ITZ and TER. What is more, the activation entropy, which is a measure of cooperativity, calculated from the Eyring model for the secondary (β)-relaxation in ITZ and POS, increased and decreased, respectively, in the compressed samples. To understand these peculiar results, we have carried out X-ray diffraction (XRD) measurements on the pressure-densified glasses and found that pressure may induce frustration in molecular organization and destroy the medium-range order while enhancing the short-range correlations between molecules. This finding allowed us to conclude that varying molecular spatial arrangement is responsible for the extraordinary dynamical behavior of ITZ, POS, and TER at high pressure.