Fluorescence enhancement of quinolines by protonation. Issue 49 (12th August 2020)

• Record Type: Journal Article
• Authors: Tervola, Essi; Truong, Khai-Nghi; Ward, Jas S.; Priimagi, Arri; Rissanen, Kari
• Is Part Of: RSC advances. Volume 10:Issue 49(2020)
• Page Start: 29385
• Page End: 29393
• Publication Date: 2020-08-12
• Subjects: Chemistry -- Periodicals; 540.5
• DOI: 10.1039/d0ra04691d
• Languages: English
• ISSNs: 2046-2069

Abstract

Abstract : The acid–base interactions of quinolines are studied in both liquid and solid-state to explore efficient tools for fluorescence enhancement. Abstract : A study of the fluorescence enhancement of isoquinoline, acridine (benzo[ b ]quinoline) and benzo[ h ]quinoline is reported with six organic acids of different p K a values. Protonation was found to be an effective tool in the fluorescence enhancement of quinolines. A significant increase in the fluorescence intensity is observed only when strong acids are used, resulting in an over 50-fold increase in fluorescence with trifluoroacetic or benzenesulfonic acid and isoquinoline in a 1.5 : 1 ratio. The benzenesulfonic acid was found to be the most effective in the protonation of the bases despite its higher p K a value compared to trifluoro- and trichloroacetic acid. The X-ray crystal structures of 14 salts reveal the charge-assisted hydrogen bond O⋯N distances to vary very little, from 2.560(2)–2.714(3) Å, with the exception of the isoquinolinium benzenesulfonate where the O⋯N distance of 2.862(7) Å is caused by additional intermolecular interactions in the solid-state.