The powerful hydrogen bonding capability of adenine makes it a key component of the DNA double helix, while as a crystalline molecular material, these hydrogen bond donors and acceptors make it a good potential cocrystal component possessing distinct physical properties. Here, we report the preparation and structure determination of four adenine-based multicomponent adducts formed with a number of dicarboxylic acids: an anhydrous cocrystal with succinic acid (1), anhydrous salts with fumaric acid (2) and maleic acid (3), and a methanolated salt with maleic acid (4). The supramolecular behavior of adenine in these materials is discussed in terms of strong hydrogen-bonded bidentate motifs formed between the adenine and acid components and the homomeric adenine synthons retained in these structures. The additional formation of a CH···N interaction on the Watson–Crick site in (3) enables the stabilization of the unusual 3H,7H adeninium tautomer within a purely molecular material.

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.

The principles of social and biological evolution have been combined in a Cultural Differential Evolution hybrid global optimization technique and applied to crystal structure solution.

The crystal structure of a previously unknown triclinic polymorph of adipamide has been solved from laboratory X-ray powder diffraction data using a new direct space global optimisation method based on differential evolution.

The crystal structure of an organic cocrystal, 1,2,3-trihydroxybenzene–hexamethylenetetramine (1/1), has been solved from conventional laboratory X-ray powder diffraction data that are significantly affected by preferred orientation, using a direct space structure solution approach based on the Monte Carlo method.