ELECTRONIC-STRUCTURE OF DONOR-SPACER-ACCEPTOR MOLECULES OF POTENTIAL INTEREST FOR MOLECULAR ELECTRONICS .3. GEOMETRY AND ABSORPTION-SPECTRUM OF CH3-ALPHA-P3CNQ

The geometry of 2-pyridinium)-alpha-cyano-4-styryldicyanomethanide was optimized using semi-empirical and ab initio quantum chemical methods . The predicted geometries using a one determinant description do not compare well with the observed geometry. A better description of the g eometry is obtained with a multi-determinant approach. Good agreement with experiment is obtained only when consideration of the media is ta ken into account. Absorption spectra in the solid state and in solutio n were calculated and the results compare very well with the experimen tal spectra. The solvatochromic shift of the absorption spectrum was c alculated using a self-consistent reaction field approach. We also dis cuss the question of whether the title molecule is best described as a zwitterion.