Thiourea‐ and Amino‐Substituted Benzoxadiazole Dyes with Large Stokes Shifts as Red‐Emitting Probe Monomers for Imprinted Polymer Layers Targeting Carboxylate‐Containing Antibiotics

Abstract

Bifunctional fluorescent molecular oxoanion probes based on the benzoxadiazole (BD) chromophore are described which integrate a thiourea binding motif and a polymerizable 2‐aminoethyl methacrylate unit in the 4,7‐positions of the BD core. Concerted charge transfer in this electron donor‐acceptor‐donor architecture endows the dyes with strongly Stokes shifted (up to >250 nm) absorption and fluorescence. Binding of electron‐rich carboxylate guests at the thiourea receptor leads to further analyte‐induced red‐shifts of the emission, shifting the fluorescence maximum of the complexes to ≥700 nm. Association constants for acetate are ranging from 1–5×105 M−1 in acetonitrile. Integration of one of the fluorescent probes through its polymerizable moiety into molecularly imprinted polymers (MIPs) grafted from the surface of submicron silica cores yielded fluorescent MIP‐coated particle probes for the selective detection of antibiotics containing aliphatic carboxylate groups such as enoxacin (ENOX) at micromolar concentrations in highly polar solvents like acetonitrile.

Red-Emitting Polymerizable Guanidinium Dyes as Fluorescent Probes in Molecularly Imprinted Polymers for Glyphosate Detection

“…As recently described by us [45], 2-((7-aminobenzo[c][1,2,5]oxadiazol-4-yl)(methyl) amino)ethyl methacrylate (0.50 g, 1.81 mmol) was dissolved in acetone (5.0 mL) before benzoyl isothiocyanate (0.25 mL, 1.81 mmol) was added. The solution was stirred at room temperature and a red precipitate was formed.…”

Polymerizable BODIPY probe crosslinker for the molecularly imprinted polymer-based detection of organic carboxylates via fluorescence

“…In addition, analyte-induced spectral band shifts, as opposed to intensity-only changes, are favoured. So far, this narrowed down the available options to benzoxadiazoles, [21][22][23][24] naphthalimides, [25][26][27] phenazines 28,29 and phenoxazinones. 30 Although BODIPY units have been incorporated into various types of polymers used in optoelectronic materials, sensors, biotherapy and imaging, [31][32][33] MIPs containing BODIPY-type probes have not yet been reported, despite their popularity, versatility and performance.…”