Solvent influence on dipole moment and charge-transfer effects in π-electron systems. N,N-dimethyl-p-nitrosoaniline

Abstract

The dipole moment of N,N-dimethyl-p-nitrosoaniline (NDMA) has been determined in 11 solvents of electric permittivity in the range 2–20. It has been found that the dipole moment of the intramolecular electron donor–acceptor interaction, Δµ_int strongly depends on solvent polarity. The increases acceptor interaction, in Δµ_int correlates well with the solvent–induced changes in n→π* and π→π* transition energies, the frequency of the ν_NO stretching vibration, and with the i.r. intensity of the ν₈ mode band. The solvent effect has been interpreted in terms of the increase of the contribution of the polar-resonance structure of the NDMA molecule, resulting from solute–solvent interactions. An attempt to explain the mechanism of the solute–solvent interaction leading to the electronic structure disturbance has been proposed.