General Design Strategy to Precisely Control the Emission of Fluorophores via a Twisted Intramolecular Charge Transfer (TICT) Process

Abstract

Fluorogenic probes for bioimaging have become essential tools for life science and medicine, and the key to their development is a precise understanding of the mechanisms available for fluorescence off/on control, such as photoinduced electron transfer (PeT) and Forster resonance energy transfer (FRET). Here we establish a new molecular design strategy to rationally develop activatable fluorescent probes, which exhibit a fluorescence off/on change in response to target biomolecules, by controlling the twisted intramolecular charge transfer (TICT) process. This approach was developed on the basis of a thorough investigation of the fluorescence quenching mechanism of N-phenyl rhodamine dyes (commercially available as the QSY series) by means of timedependent density functional theory (TD-DFT) calculations and photophysical evaluation of their derivatives. To illustrate and validate this TICT-based design strategy, we employed it to develop practical fluorogenic probes for HaloTag and SNAP-tag. We further show that the TICT-controlled fluorescence off/on mechanism is generalizable by synthesizing a Si−rhodamine-based fluorogenic probe for HaloTag, thus providing a palette of chemical dyes that spans the visible and near-infrared range.

Single‐Component 0D Metal–Organic Halides with Color‐Variable Long‐Afterglow toward Multi‐Level Information Security and White‐Light LED

“…Thus, we suspect that BPT could accommodate the twisted intramolecular charge transfer (TICT) process. Theoretically, TICT state can increase nonradiative decays ( k nr ) to shorten the afterglow, [ 37 ] but TICT also is a well‐known prerequisite for TADF due to the efficient separation of HOMO and LUMO orbitals. [ 38 ] The thermal activation energy (DEst) between singlet and triplet states can be counted as 0.21 eV based on the Equation (1), which is low enough to realize the RISC process (Figure S16d, Supporting Information).…”

Development and Characterization of a Highly Selective Turn-On Fluorescent Ligand for β3-Adrenergic Receptor

“…Fluorescence spectra in solvents with different polarity were obtained using a BMG CLARIOstar microplate reader at 40 μM. The relative fluorescence quantum yield was measured following this method with minor modification . PERSEE TU-1950 spectrophotometer and HITACHI F-2700 fluorescence spectrophotometer were used to obtain the max absorbance (less than 0.05) and fluorescent spectra.…”

“…The relative fluorescence quantum yield was measured following this method with minor modification. 28 PERSEE TU-1950 spectrophotometer and HITACHI F-2700 fluorescence spectrophotometer were used to obtain the max absorbance (less than 0.05) and fluorescent spectra. Fluorescein with a quantum yield of 92% in 1 M NaOH solution was used as the standard.…”

Fluorescent Probes with Variable Intramolecular Charge Transfer: Constructing Closed-Circle Plots for Distinguishing D2O from H2O

“…Intramolecular charge transfer (ICT) molecules are sensitive to the pH or solvent polarity by methods of wavelength variation in the absorption and fluorescence spectra. − Due to the solvent effect, the luminescence of ICT molecules can show a red shift in polar solvents due to the enlarging transient dipole . Benefited by the environment-sensitive fluorescence character, ICT molecules show good sensing capacities for temperature, ions, small molecules, pressures, biomacromolecules, − and so on. Previously, we designed several triphenylimidazole-based molecules with carboxylic groups, namely, TPI-COOH-2R (R represents the para-substituted groups, including H, F, and OH, on the phenyl rings at 4- and 5-positions of the imidazole ring), which showed pendulum-type fluorescence variation during the increase of water content ( f w , v/v) in mixed tetrahydrofuran (THF) and H 2 O solvent (Figure ).…”