Substitution Pattern Reverses the Fluorescence Response of Coumarin Glycoligands upon Coordination with Silver (I)

Abstract

Development of sugar-based fluorescence (FL) chemo-probes is of much interest since sugars are biocompatible, water-soluble and structurally rigid natural starting materials. We report here that fluorescent glycoligands with two triazolyl coumarin moieties installed onto the different positions of an identical glucosyl nucleus exert completely reversed optical response to a metal ion. C3,4-, C2,3- and C4,6-di-substituted coumarin glucosides synthesized by a click reaction similarly showed a selective FL variation in the presence of silver (I) among a range of metal cations in an aqueous solution. However, the variation was determined to be converse: the FL of the C3,4-ligand was quenched whereas that of the C2,3/C4,6-ligand tangibly enhanced. FL and NMR titrations suggested that this divergence was due to the distinct complexation modes of the conformationally constrained ligands with the ion. The optimal motifs of the ligand-ion complexation were predicted by a computational simulation. Finally, the C2,3-ligand was determined to be of low cytotoxicity and applicable in the FL imaging of silver ions internalized by live cells.

Photophysics and photochemistry of 1,2,3-triazole-based complexes

“…Bis-triazolyl coumarin glucoside 148 ( Figure 18) responds to Ag(I) with increased emission intensity with λmax ranging from 425 to 475 nm. [176] The bis-triazole-BODIPY sensor 149 selectively binds Ag(I) ions with a binding constant of 8.3 x10 6 M -1 with emission at λem = 510 nm. [177] The methylanthracene triazole-tetraazacyclododecane 150 can form a complex with Cu(II) ions which quenches the ligand fluorescence (λmax = 415 and 435 nm).…”

Spectroscopic investigation of bis-appended 1,2,3-triazole probe for the detection of Cu(II) ion

“…(29) Previous work with bis-triazoles has targeted cation sensing, particularly HTMs. (11,(30)(31)(32)(33)(34)(35)(36)(37)(38)(39)(40)(41)(42) A number of studies have employed a "turn-off" response, taking advantage of fluorescence quenching properties of metals such as Ni 2+ , Ag + , Pb 2+ , Hg 2+ and of course, Cu 2+ . (30-34, 37, 39-41) With respect to Cu 2+…”

Fluorescent glycoconjugates and their applications

“…The 7-hydroxy-coumarin substitution pattern around the glucopyranose ring has then been studied with the 3,4-and 2,3disubstituded derivatives (Figure 76). 207 Upon selective complexation with Ag + , while the 3,4-disubstituted glycoligand displayed a quenched fluorescence due to a heavy metal effect, the fluorescence of the 2,3-disubstituted counterpart largely enhanced probably because of chelation-enhanced fluorescence (CHEF). The intracellular imaging in HepG2 cells with incubation of Ag + have also been conducted (Figure 76), further proving the sensitivity of the compound in biological conditions.…”