Tetraphenylethylene AIEgen bearing thiophenylbipyridine receptor for selective detection of copper(ii) ion

Abstract

Highly emissive tetraphenylethylene chromophore appended thiophenylbipyridine pendant as a receptor (1) site has been successfully synthesized via a multistep reaction pathway. The synthesized chromophore 1 was well characterized by modern spectroscopy. In particular, the solid sample of 1 exhibits significant mechanochromic behavior upon grinding, fuming and heating. The yellow emissive chromophore 1 exhibits remarkable selectivity and sensitivity towards copper(II) perchlorate ions via a photoinduced electron transfer (PET) ‘turn off–turn on’ mechanism. When compared with competing metal ions, 1 shows little to no interference in selectivity towards Cu²⁺ ions in acetonitrile. Detailed colorimetric, UV-visible, emission, and ¹H NMR spectral studies have been employed to understand the sensing mechanism of 1 towards Cu²⁺ ion interaction which is responsible for PET ‘turn-on’. The binding constant of 1 with Cu²⁺ was shown to be 2.34 × 10⁻⁵ M with a limit of detection as low as 7.93 nM. The binding constant prompted us to explore chromophore 1 as a paper strip sensor for Cu²⁺ to develop kits for real-world practical utility.