Enhancing the Viscosity-Sensitive Range of a BODIPY Molecular Rotor by Two Orders of Magnitude |
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Authors: | Dr Stepas Toliautas Dr Jelena Dodonova Audrius ?virblis Ignas ?iplys Artūras Polita Dr Andrius Devi?is Prof Sigitas Tumkevi?ius Prof Juozas ?ulskus Dr Aurimas Vy?niauskas |
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Institution: | 1. Institute of Chemical Physics, Faculty of Physics, Vilnius University, Saul?tekio av. 9-III, 10222 Vilnius, Lithuania;2. Institute of Chemistry, Faculty of Chemistry and Geosciences, Vilnius University, Naugarduko str. 24, 03225 Vilnius, Lithuania;3. Center of Physical Sciences and Technology, Saul?tekio av. 3, Vilnius, 10257 Lithuania |
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Abstract: | Molecular rotors are a class of fluorophores that enable convenient imaging of viscosity inside microscopic samples such as lipid vesicles or live cells. Currently, rotor compounds containing a boron-dipyrromethene (BODIPY) group are among the most promising viscosity probes. In this work, it is reported that by adding heavy-electron-withdrawing ?NO2 groups, the viscosity-sensitive range of a BODIPY probe is drastically expanded from 5–1500 cP to 0.5–50 000 cP. The improved range makes it, to our knowledge, the first hydrophobic molecular rotor applicable not only at moderate viscosities but also for viscosity measurements in highly viscous samples. Furthermore, the photophysical mechanism of the BODIPY molecular rotors under study has been determined by performing quantum chemical calculations and transient absorption experiments. This mechanism demonstrates how BODIPY molecular rotors work in general, why the ?NO2 group causes such an improvement, and why BODIPY molecular rotors suffer from undesirable sensitivity to temperature. Overall, besides reporting a viscosity probe with remarkable properties, the results obtained expand the general understanding of molecular rotors and show a way to use the knowledge of their molecular action mechanism for augmenting their viscosity-sensing properties. |
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Keywords: | fluorescence spectroscopy molecular rotors time-dependent density functional theory (TD-DFT) viscosity sensing |
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