Spectral manifestations of non-additivity of hydrogen bonds in complexes of substituted anthranilic acids

Abstract

In IR spectra of complexes of N-methyl- and N-phenylanthranilic acids with acceptors of the RCOOH ⋯ B type, the νNH band of the group taking part in the intramolecular hydrogen bond NH ⋯ OC shifts to lower frequencies with an increase of the proton accepting ability of B. The intermolecular hydrogen bond of the C  O ⋯ HX type of methyl esters of these acids with proton donors results in a decrease of the νNH frequency. The strengthening (weakening) of the intramolecular bond is caused by a shift of electron density towards (from) the proton accepting site under the influence of the external proton acceptor (donor). The whole effect of the cooperative and anticooperative influence of the intermolecular hydrogen bond on the intramolecular hydrogen bond reaches 100–130 cm −1.