Multi-state efficient luminogens with solvatochromic features based on a conjugation induced twisted framework for highly selective dual channel detection of mercury ion

Abstract

In several practical sectors, it has been demonstrated that multistate emissive materials have far wider applications than single state emissive fluorophore materials; yet, this remains an extremely challenging undertaking. It has been thought that adding rigid and twisted moieties to the D-A-D core will be appropriate to allow for both solid state and solution emission. By developing a donor-acceptor-donor pattern in a twisted molecule, herein we design and synthesize triphenylamine based two novel luminogens MSE1 and MSE2 with dual-state emission (DSEgens) which are brilliantly luminous equally at the liquid and solid phase, with positive solvatochromic features. The triphenylamine molecule's bulkiness can limit intramolecular movement in the liquid phase, thereby diminishing the non-radiative emission. Additionally, the twisted structure of the molecule reduce the negative effects of close π-π stacking in the solid state resulting high emission at aggregated state. In poor solvent like H₂O and extremely condensed solvent like polyethylene glycol, compound MSE1 and MSE2 exhibit aggregation-caused redshift emission (ACRE), which are supported by DLS and SEM investigations. The compound MSE1 in THF solution is able to recognize mercury selectively over other competitive cation through UV–vis and fluorescence channel. An eight fold suppression of fluorescence intensity and a change in absorbance of 115 nm were noted at the addition of 0–8 equivalent mercury to MSE1. Additionally, MSE1 has been used to create a low-cost, portable test paper strip that may be used to selectively monitor mercury in real time.