Quantitative comparisons between α, β, γ, and δ pyrazinamide (PZA) polymorphs

Abstract

The quantitative visualizations and comparisons between the four pyrazinamide (PZA) polymorphs (α, β, γ and δ) have been investigated by graphical tools based on three-dimensional Hirshfeld surfaces and two-dimensional fingerprint plots. The comparisons were performed in terms of crystal structure, d e, Shape index, Curvedness and d norm surfaces, and fingerprint plots. The results revealed that the α and γ forms featured with 1D chains and the π···π stacking motifs belong to γ-motif, rich in π···π interactions and form infinite face-to-face stacks, β and δ forms featured with dimer unit and the π···π stacking motifs belong to γ- and herringbone–motif, respectively, the herringbone motif of δ form rich in C–H···π and edge-to-face interactions. We also correlated the phase transformation points of α, β, and δ PZA forms with the ratio of the percentage surface coverage of the N–H···O hydrogen bonds over that of the N–H···N hydrogen bonds, and found a negative correlation.