PYRIDOXAL DERIVATIVES AS PROBES FOR WATER CONCENTRATION IN NONAQUEOUSSOLVENTS

In order to provide a basis for the design of spectofluorimetric indic ators for water activity or concentration in organic solvents a series of 0- and N-alkylated pyridoxal derivatives has been prepared. The co mpounds were examined for their ability to exhibit a shift in fluoresc ence emission wavelength on complexation with water. The shift in fluo rescence on complexation with water previously observed (Yunxiang and Xin, Talanta, 1984, 31, 556) was confirmed for pyridoxal itself but al kylation of the oxygen functionalities blocked the fluorescence shift. In contrast, a strong enhancement in emission intensity but no shift in emission wavelength was observed with the N-methylpyridoxal. From t hese studies, it appears that modification at the nitrogen or, presuma bly, at C-2 or C-6 are the only available sites for the development of useful compounds from the pyridoxal prototype.