Abstract
Herein we report on a straightforward access method for boron dipyrromethene dyes (BODIPYs)-coumarin hybrids linked through their respective 8- and 6- positions, with wide functionalization of the coumarin fragment, using salicylaldehyde as a versatile building block. The computationally-assisted photophysical study unveils broadband absorption upon proper functionalization of the coumarin, as well as the key role of the conformational freedom of the coumarin appended at the meso position of the BODIPY. Such free motion almost suppresses the fluorescence signal, but enables us to apply these dyads as molecular rotors to monitor the surrounding microviscosity.
Highlights
Salicyladehyde was attached to boron dipyrromethene dyes (BODIPYs) via the Liebeskind-Srogl cross-coupling (LSCC)
Salicylaldehyde was efficiently functionalized with a BODIPY unit via a Liebeskind-Srogl cross-coupling reaction
The low fluorescence response of the reported dyads is attributed to the conformational freedom of the coumarin around the key meso position and the activation of electron transfer processes when electron-rich groups are tethered at the coumarin subunit
Summary
The design of molecules featuring two or more chromophoric units is of great interest [1,2,3,4]. These multichromophores is the low absorbance of the coumarin core [26], which falls in the ultraviolet (UV) region and it is usually masked (or at least overlapped) under the more energetic transitions of the BODIPY unit This feature hampers the application of these dyads, for instance as broadband energy. One of the main drawbacks of these multichromophores is the low absorbance of the coumarin core [26], which falls in the ultraviolet (UV) region and it is usually masked (or at least overlapped) under the more energetic transitions of the BODIPY unit This feature hampers the application of these dyads, for instance as broadband energy transfer cassettes since, while the energy transfer from the coumarin. We have conducted additional measurements at different temperatures and controlled viscosities (increasing the amount of ethylene glycol in the medium) to test the viability of these hybrids as fluorescent sensors to monitor the viscosity of the surrounding environment
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