Excitation wavelength and solvent dependent emission spectra in weakly polar aprotic solvents at room temperature and 77 K

Excitation wavelength-dependent emission spectra of 4-methyl-2,6-diformylphenol (MFOH) and o-hydroxybenzaldehyde (OHBA) have been examined both in pure weakly polar aprotic solvents and in the presence of a base at room temperature and 77 K. It is shown that fluorescence quantum yield shape, position of the spectra, and number of conformers are dependent upon the excitation energy and also on the proton-accepting ability of the solvents. Fluorescence spectra cannot be correlated with the solvent dielectric properties. At 77 K, deactivation occurs via phosphorescence only at a particular experimental condition in all the solvents studied here. The decay rates are relatively slower in an environment where the probability of hydrogen bonding interaction is stronger.