Electronic structure of donor-spacer-acceptor molecules of potential interest for molecular electronics. III. Geometry and absorption spectrum of CH3-αP3CNQ Original Research Article

The geometry of Z-β-(1-methyl-2-pyridinium)-α-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 geometry is obtained with a multi-determinant approach. Good agreement with experiment is obtained only when consideration of the media is taken into account. Absorption spectra in the solid and state in solution were calculated and the results compare very well with the experimental spectra. The solvatochromic shift of the absorption spectrum was calculated using a self-consistent reaction field approach. We also discuss the question of whether the title molecule is best described as a zwitterion.