N,N′-Dicyanoquinone Diimide-Derived Donor–Acceptor Chromophores: Conformational Analysis and Optoelectronic Properties

A formal [2 + 2] cycloaddition–cycloreversion (CA–CR) between N,N′-dicyanoquinone diimides (DCNQIs) and electron-rich alkynes was explored, providing a new class of π-conjugated donor–acceptor chromophores. These DCNQI adducts exist in the solid state as single diastereoisomers, but as two interconverting diastereoisomers in solution. Solid- and solution-state evidence for intramolecular charge transfer (CT) was obtained; additionally, the DCNQI adducts exhibit positive solvatochromism and significant solution-state third-order polarizabilities.