Decoding the ICT–PET–ESIPT liaison mechanism in a phthalimide-based trivalent transition metal ion-specific chromo-fluorogenic probe†
Abstract
Properly fusing various photophysical processes in a single chromo-fluorophore platform is crucial for developing a highly selective and sensitive chromo-fluorogenic probe to detect various target analytes. Moreover, deciphering the mechanistic approach for understanding the detection mechanism for any target analyte is paramount to facilitate the construction and development of new efficient probes for the selective detection and quantification of different target analytes. In this report, we introduce a phthalimide-based chromo-fluorogenic scaffold, DAID, fusing intramolecular charge transfer (ICT), photoinduced electron transfer (PET), and excited-state intermolecular proton transfer (ESIPT) processes in a single molecular platform. DAID showed turn-on and ratiometric chromo-fluorogenic behaviors toward trivalent transition metal ions Al3+, Fe3+, and Cr3+ in a 20% (v/v) water–DMSO mixture. A visual colorimetric change was detected in the DAID solution by incorporating trivalent transition metal ions. A remarkable turn-on green color emission enhancement was noticed in the DAID solution in the presence of these trivalent ions. The limit of detection and limit of quantification for these trivalent transition metal ions were in the nM range and were superior to those of other methods reported in the literature. Time-resolved fluorescence-lifetime-decay, 1H-NMR titration, and high-resolution mass spectrometric analysis were carried out to elucidate the detailed mechanistic aspects to understand the detection mechanism for the identification of the trivalent transition metal ions employing the DAID probe. The successful demonstration of DAID for practical applications is encouraging for its further application in a variety of fields, fusing and deciphering the various photophysical processes in a single chromo-fluorophore platform, which would enable researchers to develop new efficient probes to selectively detect various target analytes.