Photophysical properties and immobilisation of fluorescent pH responsive aminated benzimidazo[1, 2-a]quinoline-6-carbonitriles

Horak, Ema; Babić, Darko; Vianello, Robert; Perin, Nataša; Hranjec, Marijana; Steinberg, Ivana (2019) Photophysical properties and immobilisation of fluorescent pH responsive aminated benzimidazo[1, 2-a]quinoline-6-carbonitriles. Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy, 227 . ISSN 1386-1425

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Abstract

This work presents a systematic evaluation of 2-amino, 5-amino and 2, 5-diamino substituted benzimidazo[1, 2 a]quinoline-6-carbonitriles as novel pH probes with a potential application in pH sensing materials or as H+ fluoroionophores in bulk optode membranes. The study was carried out by varying the length, type and position of amino substituents in ten fluorescent dyes with the same benzimidazo[1, 2-a]quinoline-6- carbonitrile core. The photophysical and acid- base properties of the dyes were investigated by the UV/Vis absorption and fluorescence spectroscopies, and interpreted by the electronic structure DFT calculations. pH sensing mechanisms and structure-property relations affecting the fluorescence response were discussed through a detailed analysis of the piperidine substituted derivatives 1–4. Push–pull donor–acceptor interactions stimulate strong fluorescence in the visible spectral range (up to Φ = 0.65 for 7) and induce significant changes in the photophysical properties associated with the acid-base equilibria (up to a 50-fold increase in the fluorescence intensity). pKa values in aqueous and mixed solutions (v/v H2O:EtOH 99:1, 50:50), appear suitable for monitoring acidic pH in solution. The most promising candidates were immobilised in thin polymer matrices by the spin coating technique to form fluorescent sensing materials – optodes, and examined as novel pH-sensitive fluoroionophores. In the liquid membrane environment, dyes exhibited significant increase of the apparent pKas by almost 4 units. Bright and blue emissive thin films showed pH response and dynamic range around pKa = 5, making them suitable for a wide range of optical sensing applications.

Item Type:	Article
Uncontrolled Keywords:	benzimidazole ; quinoline ; pH probe ; pH sensor ; fluorescence ; fluoroionophore
Subjects:	NATURAL SCIENCES > Chemistry NATURAL SCIENCES > Chemistry > Physical Chemistry NATURAL SCIENCES > Chemistry > Theoretical Chemistry NATURAL SCIENCES > Chemistry > Analytic Chemistry NATURAL SCIENCES > Chemistry > Organic Chemistry NATURAL SCIENCES > Chemistry > Applied Chemistry
Divisions:	Division of Organic Chemistry and Biochemistry Division of Physical Chemistry
Projects:	Project title Project leader Project code Project type Dizajn i sinteza novih dušikovih heterocikličkih fluorofora i fluorescentnih nanomaterijala kao kemijskih senzora za pH i metalne ione Vianello, Robert IP-2014-09-3386 HRZZ
Depositing User:	Robert Vianello
Date Deposited:	17 Nov 2021 08:16
URI:	http://fulir.irb.hr/id/eprint/6736
DOI:	10.1016/j.saa.2019.117588

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