The Hydrogen Bonding and Proton Transfer between 4-Amino-2-methyl-6-oxabenz[f]isoquinolin-5-one and Acetic Acid

Abstract

The hydrgen Bonding and proton transfer between 4-amin-2-methyl-6-xabenz(f)is-quiolin-5rone (1) and acetic acid were discussed in detailo When (1) was recrystallized fromacetic acid white needles (4) were Qbtained, The elementalanalysis, DTA ana TGA of (4) gave that acetic acid vvas linked by hydrogen bond to e(1) in a 1:1 molar ratio, ln this case, the presence of hydrogen bonding between the amino group of (1) and the carbonyl group of acetic acid was found by means of IR spectra. From the UV spectral data it may be concluded that the hydroxy group of acetic acid is also bonded tb nitrogen atem of isoquinoline, since the enthalpy change of hydrogen bond formation between 4-amino-6-oxabenz(f)isoquinolin-5-one derivative and carboxylic acid is about 13kca1/mo1 in a non-polar so1vent. The results of fluorescence spectra revealed that ion pair was formed by proton transfer from the hydroxy group acetic acid to nitrogen atom of isoquinoline in the lowest excited state. ln addition, (4) fiuoresced very intensely in this state.