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.