Synthesis,crystal structure studies and solvatochromic behaviour of two 2‐{5‐[4‐(dimethylamino)phenyl]penta‐2,4‐dien‐1‐ylidene}malononitrile derivatives

The synthesis, crystal structure studies and solvatochromic behavior of 2‐{(2E,4E)‐5‐[4‐(dimethylamino)phenyl]penta‐2,4‐dien‐1‐ylidene}malononitrile, C₁₆H₁₅N₃ (DCV[3]), and 2‐{(2E,4E,6E)‐7‐[4‐(dimethylamino)phenyl]hepta‐2,4,6‐trien‐1‐ylidene}malononitrile, C₁₈H₁₇N₃ (DCV[4]), are reported and discussed in comparison with their homologs having a shorter length of the π‐conjugated bridge. The compounds of this series have potential use as nonlinear materials with second‐order effects due to their donor–acceptor structures. However, DCV[3] and DCV[4] crystallized in the centrosymmetric space group P2₁/c which excludes their application as nonlinear optical materials in the crystalline state. They both crystallize with two independent molecules having the same molecular conformation in the asymmetric unit. The series DCV[1]–DCV[4] demonstrated reversed solvatochromic behavior in toluene, chloroform, and acetonitrile.