Crystal structure and fluorescence behavior of N,N'-bis (1-naphthylmethyl)-diazonia-18-crown-6 diisothiocyanate.

N,N'-bis (1-naphthylmethyl)-diaza-18-crown-6 (1) showed weak emissions, suggesting that photoinduced electron transfer (PET) from the amine group to the excited naphthalene occurs. The PET fluoroionophore (1) was found to display unique photophysical properties in the presence of a guest cation. Single crystals of the HNCS salt of 1 were grown from 1 and NH(4)SCN. The crystal structure of the HNCS salt of 1 was elucidated by X-ray crystallographic analysis. The HNCS salt of 1 consists of a 1·2H(+) and 2NCS(-) ion pair. The 1·2HNCS salt gave an emission band at 332 nm. Complexation of 1 with HNCS increased the fluorescence intensity of the host by a factor of 29. The emission enhancement of 1 with HNCS was caused by the proton which dissociates from HNCS.