DYNAMIC AND ELECTROOPTICAL NON-EQUIVALENCY OF NH BONDS IN AMINO-GROUPS OF ANILINE, AMINOTOLUENES AND MONOHALOGEN-SUBSTITUTED ANILINES IN THEIR H-BONDED 1/1 AND 1/2 COMPLEXES

The spectra of 1 : 2 H-bonded complexes of aniline, aminotoluene and mono- (F, Cl, Br)-substituted anilines with acetonitrile, tetrahydrofuran, dimethyl formamide, dimethyl sulphoxide and hexamethylphosphoramide were studied in the region of the stretching and deformation vibrations of the amino group. The spectral moments M(0) and M(1) and the effective half-width 2(M(2))1/2 of the absorption bands of the amino group valence vibrations and the frequencies of the deformational vibrations of the 1 : 2 complexes were determined taking into account Fermi resonance phenomena. Force constants, valence angles gamma(HNH) and electro-optical parameters partial derivative mu/partial derivative q and partial derivative mu/partial derivative q' of the NH-bonds of the amino group were calculated. A comparative investigation of the parameters of the amino group of free molecules and of 1 : 1 and 1 : 2 complexes was carried out. The force constants and electro-optical parameters of bonded NH groups in 1 : 1 and 1 : 2 complexes were shown to be non-equivalent. Dynamic and electro-optical non-equivalence of the bonds increase with the growth of H-bond stability. The transition from free molecules to bonded ones in 1 : 2 complexes is accompanied by a significant increase in the valence angles gamma(HNH). The parameters of linear regression equations combining geometric, dynamic and spectral characteristics of the aniline amino group in H-bonded complexes are defined. The amino group electro-optical parameters of substituted anilines, partial derivative mu/partial derivative q and partial derivative mu/partial derivative q' depend significantly on the character and position of the substituents in the aniline aromatic ring and on the properties of the proton-accepting molecules.