sudden polarization
The occurrence of a large @I03130@ @C00999@ in the singlet @E02257@ of polyenes and their derivatives twisted about a double bond. Non-symmetrical substitution or geometrical distortion is effective in polarizing the system. An example is the stabilization of the zwitterionic structure of 90° twisted ethene with one @M03881@ group pyramidalized:
PAC, 1999, 71, 1919. (Glossary of terms used in theoretical organic chemistry) on page 1964 [Terms] [Paper]