Journal Highlight: Donor-substituted distyrylpyrazines: influence of steric congestion on UV–Vis absorption and fluorescence

Donor-substituted distyrylpyrazines: influence of steric congestion on UV–Vis absorption and fluorescence

Journal of Physical Organic Chemistry, 2013, 26, 137-143
Christoph Wink, Heiner Detert

Abstract: Di(p-aminostyryl)pyrazines with voluminous substituents on the nitrogen and in the adjacent positions were prepared via twofold aldol condensation. Absorption and emission spectra are influenced by increasing steric hindrance because the orbital overlap between nitrogen and π-system is modulated by voluminous groups. Strong solvatochromism of the fluorescence and huge Stokes shifts result from amplified donor–acceptor interaction in the excited state. Protonation occurs at the terminal amino groups first, followed by protonation of the central pyrazine. With increasing strength of acid, absorption and emission spectra are first shifted to the blue followed by a redshift.

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