Discovery of a sensitive Cu(ii)-cyanide “off–on” sensor based on new C-glycosyl triazolyl bis-amino acid scaffold

Abstract

A new functional glycosyl peptidomimetic, featuring a C-glucosyl 1,4-dimethoxynaphthalene backbone in conjugation with two triazolyl phenylalanine moieties on its adjacent C3,4-positions, was readily synthesized via click chemistry. Primary optical measurements indicated that the fluorescence of the ester form of this probe (4) could be selectively quenched by Pb²⁺. In contrast, the fluorescence intensity of its analog 5 with released carboxylic groups was uniquely diminished by Cu²⁺ with remarkably enhanced sensitivity and selectivity. Moreover, subsequent addition of cyanide to the methanol solution of the resulting Cu²⁺-5 complex induced its fluorescence recovery with a nanomolar detection limit, which was two orders of magnitude smaller than the regulated concentration limit of CN⁻ in drinking water. This suggests the promising applicability of C-glycosyl bis-triazolyl amino acid scaffold in the future design and exploration of sensitive “off–on” Cu(II)-cyanide chemosensors.