The Effects of Heteroatoms Si and S on Tuning the Optical Properties of Rhodamine‐ and Fluorescein‐Based Fluorescence Probes: A Theoretical Analysis. Issue 19 (9th August 2016) - Zhou, Panwang
Abstract: The effects of the incorporated heteroatoms Si and S on tuning the optical properties of rhodamine‐ and fluorescein‐based fluorescence probes is investigated using DFT and time‐dependent DFT with four different functionals. As previously proposed, the large redshift (90 nm) produced by a Si atom in both the absorption and emission spectra can be attributed to the σ*–π* conjugation between the σ* orbital of the Si atom and the π* orbital of the adjacent carbon atoms. However, the presence of a Si atom does not alter the fluorescence quenching mechanism of the nonfluorescent forms of the investigated compounds. For the first time, these theoretical results indicate that the n orbital of the S atom plays an important role in determining the optical properties of the nonfluorescent form of rhodamine‐based fluorescence probes. It alters the fluorescence quenching mechanism by lowering the energy of the dark nπ* state, which is due to breakage of the C10−S52 bond upon photoexcitation. Abstract : Calculated brightness : An enormous range of fluorescence probes have been developed based on fluorescein and rhodamine, and incorporation of the heteroatoms Si and S can tune the optical properties of these fluorophores. By using DFT and TD‐DFT methods with four different functionals, a theoretical analysis is provided on the optical properties of Si and S analogues of fluoresceins and rhodamines. The fluorescence quenching mechanism of the nonfluorescent forms of these compounds is elucidated.