Structure–Property Relationships and Nonlinear Optical Effects in Donor-Substituted Dicyanopyrazine-Derived Push–Pull Chromophores with Enlarged and Varied π-Linkers†

Thirteen new, stable, push–pull systems featuring dimethylamino and pyrazine-2,3-dicarbonitrile moieties as the donor and acceptor, respectively, and systematically extended and varied π-linkers were prepared and investigated. Evaluation of the measured UV/Vis spectra, electrochemical data (cyclic voltammetry, rotating disc voltammetry, and polarography), X-ray data, and experimentally determined and calculated hyperpolarizability values enabled structure–property studies; these revealed some important structural features that affected the efficiency of intramolecular charge-transfer and nonlinear optical properties in this class ofheterocyclic push–pull chromophores. The charge-transfer transition was most significantly affected by structuralfeatures such as π-linker length, chromophore planarity, and the number of 1,4-phenylene/ethynylene subunits in the π-linker.