CF3 H-bonding locked aromatic stacking of picric acid with mechanofluorochromic fluorophores: highly selective reusable sensor and rewritable fluorescence platform. Issue 10 (5th July 2022)

• Record Type: Journal Article
• Authors: Gayathri, Parthasarathy; Ravi, Sasikala; Nantheeswaran, Periyappan; Mariappan, Mariappan; Karthikeyan, Subramanian; Pannipara, Mehboobali; Al-Sehemi, Abdullah G.; Moon, Dohyun; Anthony, Savarimuthu Philip
• Is Part Of: Molecular Systems Design and Engineering. Volume 7:Issue 10(2022)
• Page Start: 1277
• Page End: 1286
• Publication Date: 2022-07-05
• Subjects: Chemistry -- Molecular aspects -- Periodicals; Chemical engineering -- Molecular aspects -- Periodicals; Nanotechnology -- Periodicals; 620.5
• DOI: 10.1039/d2me00075j
• Languages: English
• ISSNs: 2058-9689

Abstract

Abstract : Integrating the CF3 functional group into a mechanofluorochromic organic molecule facilitated the fabrication of a highly selective, reusable fluorescent sensor for PA in aqueous medium and rewritable fluorescence platforms. Abstract : Tailoring the molecular structure of organic fluorescent molecules is an important tool used to generate functional materials with the desired attributes for optical, opto-electronic and bio-imaging applications. Herein, we have prepared CF3 /CH3 functionalized mechanofluorochromic molecules (Cz-4-CF 3 and Cz-4-CH 3 ) and demonstrated functional group-dependent picric acid (PA) sensing and stimuli-responsive fluorescence switching. Cz-4-CF 3 and Cz-4-CH 3 exhibited strong fluorescence in solution as well as solid state. Cz-4-CF 3 showed mechanical force and heating-induced reversible fluorescence switching between two fluorescence states, whereas Cz-4-CH 3 displayed off–on fluorescence switching. Cz-4-CF 3 required scratching and annealing to revert to the initial-state fluorescence from melt state, but annealing alone transformed Cz-4-CH 3 to the initial state. Cz-4-CF 3 showed highly selective fluorescence sensing of picric acid (PA) among nitroaromatic compounds (NACs), including dinitrophenol (limit of detection = 51.4 nM). Dual-state fluorescent Cz-4-CF 3 was used to fabricate thin-film (filter paper and PVA/PMMA composite thin film) fluorescent sensors for PA in aqueous medium. Cz-4-CF 3 –PVA and free standing Cz-4-CF 3 –PMMA thin films showed highly selective fluorescence quenching upon immersion in aqueous PA solution (10 −9 to 10 −2 M). Importantly, the fluorescence was fully recovered upon dipping into pure water, and the film was reused for several cycles of PA sensing. Cz-4-CF 3 -coated filter paper also showed clear quenching of fluorescence in PA solution (10 −7 M) that could also be regenerated upon immersion in water. NMR studies indicated a possible interaction between CF3 and the hydroxyl group. Single-crystal structural analysis of Cz-4-CF 3 –PA co-crystals confirmed strong H-bonding between CF3 and the hydroxyl group of PA, which facilitated face-to-face aromatic π-stacking between carbazole and PA aromatic units and led to fluorescence quenching by charge transfer. Computational studies further support the charge transfer from Cz-4-CF 3 to PA. Highly selective fluorescence sensing of PA by other fluorophores (Cz-3-CF 3, TPA-4-CF 3 and TPA-3-CF 3 ) with CF3 substitution elucidated the broader scope of CF3 functionality for developing a PA sensor in aqueous medium. The thin-film fluorescence sensing, recyclability and contact mode detection of PA with high selectivity in aqueous medium demonstrate the practical utility for Cz-4-CF 3 for developing onsite detection of PA.