The Effect of ω-Substituted Acceptors in 4-Dimethylamino-trans-Styrenes on the Polarity in the Ground and Excited Singlet State

The electric dipole moment in the ground (μ g ) and in the first excited singlet state (μ e ) of ω-substituted acceptors in 4-dimethylamino-trans-styrenes (Z=P(S)Ph 2 , P(O)Ph 2 , SO 2 CH 3 ) were determined by solvatochromic and thermochromic methods. The obtained values of μ e and μ g and the values for Z=CN and Z=NO 2 known from the literature [2] fulfill the linear relation between the dipole moments (μ e or μ g ) and the Hammett constants σ p of the substituents. On increasing the electron-acceptor power of Z, μ e grows faster than μ g