N-Methylquinolinium derivatives for photonic applications: Enhancement of electron-withdrawing character beyond that of the widely-used N-methylpyridinium
styryl quinolinium push–pull chromophores have been designed and synthesized in order to examine the electron-withdrawing strength of various quinolinium electron acceptor groups, and their influence on the photophysical properties and in particular on the second-order nonlinear optical response. The static molecular first hyperpolarizabilities measured by long-wavelength hyper-Rayleighscattering are