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Updated: Apr 23, 2026

Microwave-assisted Intramolecular Dehydrogenative Diels-Alder Reactions for the Synthesis of Functionalized Naphthalenes/Solvatochromic Dyes
Published on: April 1, 2013
Synthesis and spectroscopic characterization of 1,8-naphthalimide derived "super" photoacids
Tatu Kumpulainen1, Bert H Bakker, Michiel Hilbers
1Van 't Hoff Institute for Molecular Sciences, Faculty of Science, University of Amsterdam , P.O. Box 94157, 1090 GD Amsterdam, The Netherlands.
Abstract:
The ground- and excited-state acid-base properties of three novel naphthalimide-based “super” photoacids were studied using steady-state and time-resolved spectroscopy. The compounds exhibit pKa = 8.8-8.0 and pKa* = -1.2 to -1.9. The decrease in both ground- and excited-state pKa is achieved by attachment of an electron withdrawing group (sulfonate) on the aromatic system. All compounds are deprotonated upon excitation in alcohols and DMSO. Good correlation is established between the pKa* and the ratio of the neutral and anion emission intensities in a certain solvent. The excited-state intermolecular proton transfer to solvent (H2O and DMSO) is explained by a two-step model. In the first step, short-range proton transfer takes place, resulting in the formation of a contact ion pair. Free ion pairs are formed in the diffusion controlled second step.
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