Proton transfer reaction of 4-methyl-2,6-diamidophenol in some non-polar solvents at room temperature and 77 K

The fluorescence properties of 4-methyl-2,6-diamidophenol (MDOH) are examin ed in some non-polar solvents in relation to 4-methyl-2,6-diformyl phenol ( MFOH) and quantum yield measurements are made at room temperature and 77 K. The excited state intramolecular proton transfer (ESIPT) is evidenced by a large Stokes-shifted emission (similar to 9000 cm(-1)) which is likely to originate from the enol tautomer. From nanosecond measurements and quantum yields of fluorescence, we have determined proton transfer rates. It is obs erved that the non-radiative channels are always dominant in the decay proc esses of the excited state of MDOH. At 77 K, MDOH exhibits, like MFOH, phos phorescence in all the non-polar solvents studied here and the conversion o f fluorescence into phosphorescence in the case of MDOH is relatively slow compared to that of MFOH. (C) 1999 Elsevier Science B.V. All rights reserve d.