Imidazolium Based Probes for Recognition of Biologically and Medically Relevant Anions

Abstract

The imidazolium derivatives due to their positive charge possess one of the most polarized and positively charged proton at C2-H to form strong ionic hydrogen bond (also termed as double ionic hydrogen bond) with anions and also provide opportunities for anion - π interactions with electron-deficient imidazolium ring. In the present review article, imidazolium based molecular probes for their ability to recognize inorganic anions like halides, cyanide, perchlorate, carboxylic acids, phosphate, sulfate etc. and their derived molecules viz. nucleotides, DNA, RNA, surfactants, proteins, etc have been discussed. The review covers the literature published after year 2009 and has > 130 references. The previous literature has already been discussed by Yoon et al. in two review articles published in Chem. Soc. Rev. 2006 and 2010.

The Fluorescence Behavior Studies and Applications of Two D‐π‐A Type Imidazolium Analogs

“…reported imidazolium probes that gave the fluorescence turn‐off response in aggregation . Unlike TPI‐1 , the addition of UTP also caused the aggregation of TPI‐2 in PBS buffer (Figure S5), but the fluorescence spectra showed the tiny change (Figure S6).…”

“…It has been widely used in constructing the conjugated cationic luminophores . In addition, imidazolium moiety was an excellent recognition group for some anions or biomolecules that used in fluorescence probes . The cationic probes were facile to interact with and enter into living cells because of the electrostatic interaction .…”

Luminescent Imidazolium Salts as Bright Multi‐Faceted Tools for Biology

“…Anion receptors commonly use functional groups such as amide, pyrrole, ammonium or guanidinium to form N−H−A − type‐hydrogen bonds [14] . As a result of their excellent hydrogen bond donor character (C−H) + −A − , imidazolium fragments bearing aromatic rings constitute very efficient receptors that can most notably interact with the phosphate groups of nucleic acids and nucleotides [13,15,16] . Anion differentiation at physiological pH is often hindered due to competitive hydrogen bonds with the solvent and complementary functional groups such as the hydroxyl groups of ATP and GTP [17] .…”

“…[14] As a result of their excellent hydrogen bond donor character (CÀ H) + À A À , imidazolium fragments bearing aromatic rings constitute very efficient receptors that can most notably interact with the phosphate groups of nucleic acids and nucleotides. [13,15,16] Anion differentiation at physiological pH is often hindered due to competitive hydrogen bonds with the solvent and complementary functional groups such as the hydroxyl groups of ATP and GTP. [17] It was demonstrated that the coupling of acridine-, naphthalene-, pyrene-or anthracene-like chromophores with imidazolium rings improves receptor selectivity towards biomacromolecules, while enabling the detection of the interaction by spectrofluorimetry.…”

“…In a nutshell, the development of new luminescent tools comes as an answer to the growing need for visualizing the infinitely small, and associated dynamic phenomena in a non‐invasive way. Luminescent molecular salts, especially based on imidazolium moieties, [6–9] and the supramolecular self‐assemblies they can form, [10–12] exhibit exceptional properties which predispose them to be used as probes to explore living and inert matter [13] . Here, we propose a review of the recent investigations of the interactions engaged by luminescent imidazolium salts (IMs) with biological entities and systems, as well as their potential applications in detection, imaging, and theranostics.…”