In:
Photochemistry and Photobiology, Wiley, Vol. 91, No. 3 ( 2015-05), p. 654-659
Abstract:
The photophysical properties of fluorescent Hammett acidity indicator derived from 3,4,5,6‐tetrahydrobis(pyrido[3,2‐ g ]indolo)[2,3‐ a :3′,2′‐ j ]acridine (1a), 6‐bis(pyrido[3,2‐ g ]indol‐2′‐yl)pyridine (1b) and their analogues have been investigated in sulfuric acid solutions by means of absorption, fluorimetry, relaxation dynamics and computational approach. These new indicators undergo a reversible protonation process in the Hammett acidity range of H 0 〈 0, accompanied by a drastic increase of the bright blue‐green (1a) or yellow (1b) fluorescence intensity upon increasing the acidity. For 1a in H 2 SO 4 , the emission yield increases as large as 200 folds from pH = −0.41 to the Hammett acidity range of −5.17, the results of which are rationalized by a much increase of the steric hindrance upon third protonation toward the central pyridinic site, together with their accompanied changes of electronic configuration from charge transfer to a delocalized ππ * character in the lowest lying excited state. The combination of 1a and 1b renders a wide and linear range of H 0 measurement from −1.2 to −5.1 detected by highly intensive fluorescence.
Type of Medium:
Online Resource
ISSN:
0031-8655
,
1751-1097
DOI:
10.1111/php.2015.91.issue-3
Language:
English
Publisher:
Wiley
Publication Date:
2015
detail.hit.zdb_id:
2048860-9
SSG:
12
Bookmarklink