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Li+-induced Fluorescent Metallogel: a case of ESIPT-CHEF and ICT phenomenon

Abstract

A fluorescent metallogel (1%, w/v) has been synthesized from the non fluorescent ingredients viz. smallest possible low molecular weight aromatic symmetrical ligand H2SA (1) and LiOH in chloroform and methanol mixture. The chelation of Li+ is not only responsible for the inhibition of Excited State Intramolecular Proton Transfer (ESIPT) or origin of fluorescence through Chelation Enhanced Fluorescence (CHEF) in 1, but also for aggregation leading to gelation. Metallogel obtained from 1/Li+ reveals the fibrous morphology while 1 with other bigger size alkali metal ions like Na+/K+/Cs+ demonstrates the crystals growth with different shapes. Effect of size of alkali metal ions over gel formation are well explored by FTIR, UV-vis, fluorescence, average lifetime measurments, SEM and PXRD. Metallogel shows multi-stumuli responsive behaviour towards thermal and mechanical stress as well as reswelling property. Regioisomer H2PBA (2) also shows emission upon treatment with LiOH due to presence of intramolecular charge transfer (ICT) is well established by various experiments. Mechanism of gel formation is well established by FTIR, 1H NMR, UV-vis, fluorescence, life time measurements, SEM, single crystal and powder XRD intrumental techniques. The involvement of various phenomenon in gel formation has been further supported by other synthesized model coumpounds viz. H2MBA (3) and PMO (4), H2SEA (5) and H2SPA (6). True gel phase material is proved by a detailed rheological experiments.

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Publication details

The article was accepted on 10 Aug 2018 and first published on 10 Aug 2018


Article type: Paper
DOI: 10.1039/C8CP04579H
Citation: Phys. Chem. Chem. Phys., 2018, Accepted Manuscript
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    Li+-induced Fluorescent Metallogel: a case of ESIPT-CHEF and ICT phenomenon

    M. Dubey and M. K. Dixit, Phys. Chem. Chem. Phys., 2018, Accepted Manuscript , DOI: 10.1039/C8CP04579H

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