Unusual Chemical Ratio, Z″ Values, and Polymorphismin Three New N-Methyl Aminopyridine–4-NitrophenolAdducts.

Cocrystallization of 4-nitrophenol(I) with N-methyl substituted aminopyridines,4-N-methylaminopyridine 1, 2-N-methylaminopyridine 2, and 2-N,N-dimethylaminopyridine 3, resultedin three novel adducts 1·2(I), 2·3(I), and 3·3(I), one of which, 2·3(I), wasfound in three polymorphic forms, A, B,and C. The single crystals were grown by slowevaporation from ethanol. The proton transfer from the phenoxy tothe pyridine moieties was registered in all compounds. The adductscomprise pyridinium cations, 4-nitrophenolate anions, and varyingin number neutral 4-nitrophenol molecules. Though the asymmetric hydrogen-bondednetwork involving the −N+H groups of pyridiniumcations and the −C–O–and −C–OHgroups of 4-nitrophenol moieties is registered in the adducts, thedelicate balance of noncovalent interactions that include CH···Ohydrogen bonds and face-to-face stacking interactions between theextended antiparallel arrays of components controls the centrosymmetricpacking. Although three polymorphs of 2·3(I) share several structural common features, they reveal significantdifferences in the conformation of the pyridinium cation, and thehydrogen-bonding patterns. [ABSTRACT FROM AUTHOR]