Dynamic and electrooptical non-equivalency of amino group NH bonds of anisidines in H-bonded 1:1 and 1:2 complexes with proton acceptors

IR spectra of 1:1 and 1:2 complexes of meta-, ortho- and paraanisidines with various proton accepters were studied in aprotic solvents in the region of stretching and deformational vibrations of NH2 group. The spectral moments M-(0), M-(1), M-(2) and effective halfwidth (2M((2)))(1/2) of valence nu(NH) bands as well as frequencies of deformation modes of free and hydrogen-bonded NH2 groups have been determined. 1:1 complexes formation constants of anisidines with DMF, DMSO, HMPA as well as dynamic parameters and valence angles gamma(HNH) of free and hydrogen-bonded molecules have been found. Dynamic and electrooptical non-equivalence of N-H bonds in 1:1 and 1:2 complexes were studied. It was shown that electrooptical non-equivalency N-H bonds increase more distinctly with the growth of the hydrogen bond strength than the dynamic one. The correlation has been established between spectroscopic, dynamic and electrooptical characteristics of NH2 groups in free and hydrogen-bonded molecules of anisidines. (C) 1998 Elsevier Science B.V.