N-[2-(4-Methoxy-phenyl)-ethyl]-2-(quinolin-8-yloxy)acetamide:: a receptor for acid binding

Different hydrates of the receptor, N-[2-(4-methoxy-phenyl)-ethyl]-2-(quinolin-8-yloxy)acetamide(I), and its co-crystals with acetic acid and L(+)alpha-hydroxy-phenylacetic acid are synthesised and their structures are studied. The acids such as acetic acid, L(+)alpha-hydroxy-phenylacetic acid quench fluorescence of I. The receptor I shows a fluorescence quenching on interaction with perchloric acid in benzene, whereas in methanol the solution of I results in the generation of a new fluorescence emission at higher wavelengths. The crystal structure of the perchlorate salt is determined to explain the protonation behaviour of the receptor I and the perchlorate salt in methanol leads to fluorescence emission at a place different from that of the parent compound.