Infrared spectra and protonation of 1,8-bis(dimethylamino)naphthalene in acetonitrile

Abstract

Fourier-transform infrared studies on 1,8-bis(dimethylamino)naphthalene (DMAN) salts in acetonitrile have been performed. In contrast to solid salts very broad ‘continua’ of protonic absorption are observed typical of the usual NHN⁺ homoconjugated cations formed by the hydrogen bases. The deuterium isotopic ratio ν(NHN)/ν(NDN), estimated from the positions of the band weighted centres, is equal to ca. 1. For some salts a deprotonization of DMANH⁺ and formation of homoconjugated anions were detected. The tendency to form the homoconjugated anions can be arranged in the sequence C₆ClO^–₅ > NO^–₃ > NCS^– > Cl^– > ClO^–₄. in the case of pentachlorophenolate free DMAN, protonated DMAN and homoconjugated anions are present in the solution in the proportion 1 : 1 : 1.