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ORIGINAL RESEARCH article

Front. Chem.
Sec. Organic Chemistry
Volume 12 - 2024 | doi: 10.3389/fchem.2024.1473769
This article is part of the Research Topic Synthesis, Structural Analysis, and Conformational Behavior of BODIPY Dyes and Their Congeners View all 3 articles

Tetraarylpyrrolo[3,2-b]pyrrole-BODIPY dyad: A Molecular Rotor for FRET based Viscosity Sensing

Provisionally accepted
Richa Agrawal Richa Agrawal 1Sudip Gorai Sudip Gorai 1Sunil S. Yadav Sunil S. Yadav 2Amey P. Wadawale Amey P. Wadawale 1Soumyaditya Mula Soumyaditya Mula 1*
  • 1 Bhabha Atomic Research Centre (BARC), Mumbai, India
  • 2 National Centre for Nanoscience and Nanotechnology, University of Mumbai, Mumbai, Maharashtra, India

The final, formatted version of the article will be published soon.

    With the aim to develop a FRET based viscosity sensor, two dyad molecules, 4 and 5, comprising of tetraarylpyrrolo[3,2-b]pyrrole (TAPP) (donor) and naked boron-dipyrromethene (BODIPY) dyes (acceptor) were designed. Dyads were synthesized via acid catalysed multicomponent reactions followed by Sonogashira coupling. In both the dyads, BODIPY and TAPP moieties are linked through phenylethynyl groups which allow free rotation of the BODIPY dyes i.e. they can act as molecular rotors. This was supported by X-ray crystallographic and DFT optimized structures. Spectroscopic studies also confirmed the presence of both TAPP and BODIPY dyes in dyads with no electronic interactions which is suitable for fluorescence resonance energy transfer (FRET). Very high energy transfer efficiency (ETE >99%) from donor TAPP moiety to acceptor BODIPY moiety on excitation at the TAPP part was observed. But due to the non-fluorescent nature of naked BODIPY dyes, no fluorescence emission was observed from BODIPY moiety in both the dyads. But, with increasing solvent viscosities, emission from the BODIPY moieties increases due to restricted rotation of the BODIPY moieties. Plot of logarithms of fluorescent intensity of dyad 5 and viscosity of the solution showed a good linear correlation obeying Förster-Hoffmann equation. Non-fluorescent dyad 5 in methanol became greenish yellow fluorescent in methanol/glycerol (1:1) solvent. Further, with increase in temperature of methanol/glycerol (1:1) system, as the viscosity decreases, the fluorescence also starts decreasing. Thus, the dyad 5 is capable of sensing the viscosity of the medium via FRET based “Off-On” mechanism. This type of viscosity sensor with very large pseudo-Stokes shift and increased sensitivity will be useful for future advancement of chemo-bio sensing and imaging applications.

    Keywords: Tetraarylpyrrolo[3,2-b]pyrrole, BODIPY, Dyad, Viscosity sensor, Molecular rotor, FRET

    Received: 31 Jul 2024; Accepted: 11 Sep 2024.

    Copyright: © 2024 Agrawal, Gorai, Yadav, Wadawale and Mula. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

    * Correspondence: Soumyaditya Mula, Bhabha Atomic Research Centre (BARC), Mumbai, India

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