The cocrystal nicotinamide-succinic acid (2/1).

In the asymmetric unit of the crystal structure of nicotinamide-succinic acid (2/1), 2C(6)H(6)N(2)O x C(4)H(6)O(4), there are two independent nicotinamide molecules in general positions and two half succinic acid molecules which lie about inversion centres. The structure contains acid-pyridine and amide-amide synthons with nicotinamide molecules forming ladders of alternating R(2)(2)(8) and R(4)(2)(8) rings linked through succinic acid to generate a corrugated hydrogen-bonded sheet. This sheet is a common supramolecular unit found in other 2:1 nicotinamide-dicarboxylic acid cocrystals, but the presence of two crystallographically distinct nicotinamides with anti and syn conformations, forming two distinct sheets within the same structure, is a novel packing feature in this type of material.