SPECTROSCOPIC EVIDENCE OF HYDROGEN-BONDING AND INTRAMOLECULAR CHARGE-TRANSFER COOPERATION IN POLAR M-AMINOPHENOL CRYSTAL

The polarized infrared (IR) and Raman spectra of the m-aminophenol (m-AP) single crystal and the vibrational spectra of its solutions and powders in the 200-4000 cm-1 and 5000-7000 cm-1 regions as well as the electronic spectra were measured. on the basis of previous data and the oriented gas-model calculations, assignments of the internal vibrations are proposed. Discrepancies from the model relative intensities are explained with the help of quantum chemical INDO calculations by vibronic couplings and by the delocalization of charge through the chain of molecules connected by intermolecular OH⋯N bonding. The possibility of proton transfer in the excited state was excluded. The findings were considered in view of the non-linear electrooptic properties of the m-AP crystal. © 1990.