Bicyclic-Ammonium-Incorporated Ylidic Nitrogen Groups for Strong π-Electron Donation in Push–Pull Benzene π-Conjugated Systems

Ylidic nitrogen-based π-electron-donating groups, (quinuclidinio)amidyl (QA) and (1-azanorbornanio)amidyl (ANA) groups, were developed to shift the absorption of push-pull benzenes toward longer wavelengths. Changing the pyrrolidinyl group to the QA or ANA group achieved a bathochromic shift of 45-100 nm in the maximum absorption wavelength, depending on the push-pull π-conjugated system investigated (<i>p</i>-nitrobenzene, 1,8-naphthalimide, and an azo dye).