Self-Organization of 2-Acylaminopyridines in the Solid State and in Solution

Aggregation of 2-acylaminopyridines and their 6-methyl derivatives in chloroform solution was studied by 1H, 13C, and 15N NMR spectroscopies. The results were compared with 13C and 15N CPMAS NMR and IR spectral as well as with X-ray structural data. Intermolecular interactions in solution and in solid state were found to have a similar nature. Relatively strong Namide−H···Npyridine intermolecular hydrogen bonds enable dimerization to take place. Steric interactions in N-pivaloyl- and N-1-adamantylcarbonyl as well as that caused by the 6-methyl group hinder formation of the dimeric aggregates stabilized by the Namide−H···Npyridine intermolecular hydrogen bonds. In general, the DFT optimized geometries of the aggregates in chloroform solution are in agreement with the X-ray crystal structures. Wavenumbers of the stretching vibration band of the CO group were also found indicative of the type of hydrogen bond present in the solid state.