The crystal structures and melting point properties of isonicotinamide cocrystals with alkanediacids HO2C(CH2)n−2CO2Hn = 7–9

Abstract

The tunability of physiochemical properties of crystalline materials through controlled cocrystal formulation is an aim for both the pharmaceutical industry and crystal engineers. In this paper we report that the melting point alternation behaviour of odd and even alkanedicarboxylic acids is mimicked in a set of cocrystals in which isonicotinamide is combined in a 1 : 1 stoichiometry with pimelic acid, suberic acid and azelaic acid. All three structures contain hydrogen bonded chains of alternating acid and amide molecules between which acid–pyridine and acid–amide synthons are formed. Both isonicotinamide : pimelic acid and isonicotinamide : azelaic acid form structures in which the acid moiety adopts a twisted alkyl backbone conformation similar to that observed in the pure odd alkanediacid materials. The isonicotinamide : suberic acid cocrystal differs from the others reported here retaining both the elevated melting point and the planar acid conformation displayed by even alkanediacid materials in this series.