CRYSTAL-STRUCTURES AND CHARGE-DISTRIBUTIONS IN 2-PHENYL-IMIDAZO[1,2-A]-PYRIDINE AND 2 RELATED SALTS

X-ray structural investigations of 2-phenylimidazo[1,2-a]pyridine and two of its salts: 1-methyl-2-phenyl-imidazo[1 ,2-a]pyridinium iodide a nd 1-methyl-2-phenyl-6-nitro-imidazo[1,2-a]pyridinium iodide (R = 0.04 0, 0.032, 0.034 respectively), together with semi-empirical calculatio ns of charge distribution, have been carried out. The insertion of nit ro-group does not cause any fundamental changes in geometry, but induc es changes in the electron density distribution in the bicyclic unit. As a result rather short cation-anion contacts (I...C = 3.52 Angstrom) are observed in structure III.