STUDIES OF HYDROGEN-BONDED COMPLEXES OF 4-METHOXYBENZONITRILE IN-GROUND AND LOWEST TRIPLET-STATES BY IR, PHOSPHORESCENCE, AND N-15 NMR-SPECTRA

The formation of hydrogen-bonded complexes between 4-methoxybenzonitri le and various OH proton donors was studied in solution in the ground electronic state by means of IR absorption spectra, and the Delta H va lues were measured. The upfield shift of purely electronic 0-0 transit ion is observed in low temperature phosphorescence spectra under the i nteraction, the values of this shift for different proton donor molecu les being correlated with the chemical shifts of N-15 NMR signals unde r the complex formation. The nature of observed anomalous N signal shi ft in NMR spectra was explained by a decrease of paramagnetic deshield ing because of the mixing of ground and lowest triplet electronic stat es of the nitrile studied. (C) 1998 Elsevier Science B.V.