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Colourimetric Sensing of Anions with Bis(indolyl)methane based on Donor Acceptor Interaction: A Study based on Experimental and Computational Evidences
Author(s) -
Pegu Rupa,
Pratihar Sanjay
Publication year - 2016
Publication title -
chemistryselect
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.437
H-Index - 34
ISSN - 2365-6549
DOI - 10.1002/slct.201600468
Subject(s) - chemistry , deprotonation , naked eye , fluoride , indole test , acceptor , molecule , dissociation (chemistry) , substituent , solvent , homo/lumo , photochemistry , aryl , ion , selectivity , medicinal chemistry , inorganic chemistry , stereochemistry , organic chemistry , catalysis , condensed matter physics , physics , alkyl , chromatography , detection limit
In this report, different bis(indolyl)methane ( BIM ) derivatives based on their different donor and acceptor ability were designed and synthesized via facile synthetic route and successfully utilized as an efficient colourimetric and selective sensors for fluoride and acetate via naked eye detection. The in‐situ NMR, UV‐vis, and theoretical study confirms that fluoride induced 1:2 binding interaction between BIM and fluoride followed by deprotonation to its corresponding di‐anion, in which lower HOMO‐LUMO energy gap of the di‐anion compared to its neutral molecule is responsible for corresponding color and spectral change in the absorption properties of the molecule. The H‐bonded association‐dissociation equilibrium between BIM and its corresponding di‐anion is favorable in highly polar aprotic solvent and will be favorable in the order of DMF>DMSO>THF>acetone. The interaction between anion and indole N−H of BIM is likely to be depends upon the acidity of N−H and interaction between most basic fluoride and most acidic N−H is favorable over least or moderately acidic N−H. The appropriate tuning of both the substituent at aryl and indole moieties of BIM may direct sensitivity and selectivity of BIM towards different anion.