New fluorescent probes for visual proteins. Part II. 5-(Oxo)penta-2,4-dienyl-p-(N,N-dimethylamino)benzoate

Abstract

A new dual-fluorescent compound, 5-(oxo)penta-2,4-dienyl-p-(N,N-dimethylamino)benzoate (1), a derivative of dimethylaminobenzoic acid, has been synthesised and studied photophysically. This compound continues the series of potential fluorescent probes for visual and proton-pumping opsin proteins. The photophysical behaviour of this molecule, including charge-transfer interaction in the ground state and dual-fluorescence emission, is similar to that of the previously studied analogue cis-3-(oxo)propenyl-p-(N,N-dimethylamino)benzoate (cis-2). The presence of several theoretically calculated conformers of compound 2 was suggested to be responsible for the observed strongly red-shifted absorption and excitation wavelength dependence. These photophysical anomalies were also observed for molecule 1, though the models put forward to explain them in the cases of 1 and 2 are rather different. Based on theoretical calculations and experimental results, we propose that some of the stable conformers might be connected with either a charge-transfer complex or mesomeric interactions in the ground state. Upon changing the electronic nature of the oxo-pentadienyl acceptor moiety, e.g. protonation, chemical or biochemical reaction, the charge-transfer absorption disappears, which leads to a dramatic increase in the fluorescence quantum yield.

New Fluorophore Design

“…Among these mechanisms, twisted intramolecular charge transfer (TICT) remains one of the most well-studied and established photoprocesses to display two-color emission [24]. A number of applications have evolved from this two-color response, most notably in the area of fluorescent molecular probes for ions and molecules [25][26][27][28]. Some of the photophysical processes currently published that account for two-color emission from non-ICT systems also have potentially useful applications, particularly in the area of analytical response.…”

Structural peculiarities of configurational isomers of 1‐styrylpyrroles according to 1Н, 13С and 15N NMR spectroscopy and density functional theory calculations: electronic and steric hindrance for planar structure

“…[4,6] Recently, a transition metal-free hydroamination of arylacetylenes with substituted pyrroles in the superbasic system KOH/DMSO providing a general straightforward route to nitrogen analogs of stilbenes, diversely substituted 1-styrylpyrroles, has been developed. [7] The novel pyrrole analogs of stilbenes thus synthesized represent promising highly potent synthetic intermediates, building blocks for drug design [8] and precursors for optoelectronic advanced materials, particularly for molecular optical switches, [9] biological labels, [10] sensors, [11] ligands for metallocomplexes [12] and information recording/storage devices. [13] By using 1 H NMR spectroscopy, the E and Z isomers of the synthesized molecules have been identified.…”

First Photolysis of Benzidine Schiff Base in Non Aqueous Solvents

“…Morad eta al., 2007)and their uses as catalysts (J. Zhang, Y. Tang et al 2005) and as compounds of interesting photoluminescent(V. Papper et al ,2003) and electroluminescent (T. Maindron et al ,2004)properties.…”