SYNTHESES WITH NITRILES .97. PUSH-PULL DIARYLBUTADIENES AND DIARYLPENTADIENES - KNOWN CHROMOPHORES - NEW FACTS

The syntheses and properties of 1,1-dicyano-1,3-butadienes and 3-dicya nomethylene- 1,4-pentadienes, readily obtained by Knoevenagel condensa tions of benzaldehydes with alpha-methylbenzylidenemalononitriles and 1,1-dicyano-2-methyl-4-phenyl-1,3-butadienes, respectively, are descri bed Color-constitution relationships and their possible use for nonlin ear optics are discussed. Calculations of excitation energies using th e PPP method are in good agreement with experimental values. In contra st, the INDO/S procedure only leads to a satisfactory correlation if s olvent effects are included in the calculations.