Intramolecular charge transfer (ICT) is a fundamental mechanism that enables the development of numerous fluorophores and probes for bioimaging and sensing. However, the electron-withdrawing targets ...(EWTs)-induced fluorescence quenching is a long-standing and unsolved issue in ICT fluorophores, and significantly limits the widespread applicability. Here we report a simple and generalizable structural-modification for completely overturning the intramolecular rotation driving energy, and thus fully reversing the ICT fluorophores' quenching mode into light-up mode. Specifically, the insertion of an indazole unit into ICT scaffold can fully amplify the intramolecular rotation in donor-indazole-π-acceptor fluorophores (fluorescence OFF), whereas efficiently suppressing the rotation in their EWT-substituted system (fluorescence ON). This molecular strategy is generalizable, yielding a palette of chromophores with fluorescence umpolung that spans visible and near-infrared range. This strategy expands the bio-analytical toolboxes and allows exploiting ICT fluorophores for light-up sensing of EWTs including N-acetyltransferases and nerve agents.
Photoacoustic imaging (PAI), a state‐of‐the‐art noninvasive in vivo imaging technique, has been widely used in clinical disease diagnosis. However, the design of high‐performance PAI agents with ...three key characteristics, i.e., near‐infrared (NIR) absorption (λabs>800 nm), intense PA signals, and excellent photostability, remains a challenging goal. Herein, we present a facile but effective approach for engineering PAI agents by amplifying intramolecular low‐frequency vibrations and enhancing the push‐pull effect. As a demonstration of this blended approach, we constructed a PAI agent (BDP1‐NEt2) based on the boron‐dipyrromethene (BODIPY) scaffold. Compared with indocyanine green (ICG, an FDA‐approved organic dye widely utilized in PAI studies; λabs=788 nm), BDP1‐NEt2 exhibited a UV/Vis‐NIR spectrum peaked at 825 nm, superior in vivo PA signal intensity and outstanding stability to offer improved tumor diagnostics. We believe this work provides a promising strategy to develop the next generation of PAI agents.
In this work, we present a facile but effective approach for engineering photoacoustic imaging (PAI) agents by amplifying intramolecular low‐frequency vibrations and enhancing the push‐pull effect. As a demonstration of this blended approach, we constructed a PAI agent (BDP1‐NEt2) based on the boron‐dipyrromethene (BODIPY) scaffold, which met key requirements of high‐quality PAI.
Excited‐state intramolecular proton transfer (ESIPT)‐based solid luminescent materials with multiple hydrogen bond acceptors (HBAs) remain unexplored. Herein, we introduced a family of Janus‐type ...ESIPT chromophores featuring distinctive hydrogen bond (H‐bond) selectivity between competitive HBAs in a single molecule. Our investigations showed that the central hydroxyl group preferentially forms intramolecular H‐bonds with imines in imine‐modified 2‐hydroxyphenyl benzothiazole (HBT) chromophores but tethers the benzothiazole moiety in hydrazone‐modified HBT chromophores. Imine‐derived HBTs generally exhibit higher fluorescence efficiency, while hydrazone‐derived HBTs show a reduced overlap between the absorption and fluorescence bands. Quantum chemical calculations unveiled the molecular origins of the biased intramolecular H‐bonds and their impact on the ESIPT process. This Janus‐type ESIPT chromophore skeleton provides new opportunities for the design of solid luminescent materials.
A new family of Janus‐type ESIPT chromophores with distinctive hydrogen bonding selectivity between competitive hydrogen bond acceptors (HBAs) were reported. Single‐crystal structures and theoretical studies unveiled the molecular origins of the biased intramolecular hydrogen bonds (H‐bonds) and their impact on the ESIPT process. This Janus‐type ESIPT chromophore skeleton provides new opportunities for the design of solid luminescent materials.
A fluorescent probe (
COU-LIP-1
) for monitoring labile Fe(
ii
) pools (LIP) with high selectivity and sensitivity was developed utilizing coumarin 343 as the fluorophore and 3-nitrophenylazanyl ...ester as both the reactive group and the fluorescence quenching group. Fe(
ii
)-induced reductive cleavage of the N-O bond results in a turn-on response
via
a photo-induced photon transfer (PET) mechanism. The probe was applied for monitoring labile iron(
ii
) changes in M1 and M2a macrophage activations and also erastin-induced ferroptosis, providing a powerful tool for selectively sensing LIP under both physiological and stressed conditions.
Reductive cleavage of a coumarin 3-nitrophenylazanyl ester allows turn-on fluorescence detection of ferrous ions in macrophage activation and ferroptosis induction.
Three new derivatives of (4-methoxyphenyl) ethynyl-naphthalimide were synthesized by Sonogashira coupling reaction. These compounds showed robust and strong fluorescent signals, which shift from blue ...to orange as the solvent polarity increases. Computational calculations revealed that in low-polarity solvents, the molecules preferred a 90° rotation between the naphthalimide and ethynyl benzene fragments. In high-polarity solvents, where the energy barrier for rotation of the alkyne bond was higher, the molecules favored the 0° conformer, leading to longer emission wavelengths. The compound with a 2-methoxyethyl group tethered to the naphthalimide nitrogen demonstrated sensitivity to water presence in the ranges of 0–30 % (v/v) in THF, 0–15 % (v/v) in DMSO, 0–30 % (v/v) in MeCN, 0–15 % (v/v) in acetone, and 0–40 % (v/v) in EtOH. The detection limits for water were determined to be 0.0523 %, 0.1365 %, 0.0337 %, 0.0570 %, and 0.1170 % (v/v) in THF, DMSO, MeCN, acetone, and EtOH, respectively. The effectiveness of this compound in quantifying ethanol content in spirit samples was successfully demonstrated.
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•Three new naphthalimides exhibited strong fluorescence transitioning from blue to orange based on solvent polarity.•Computational calculations identified conformational preferences influencing emission wavelengths.•One of these compounds was effective for quantifying ethanol in spirit samples.
Pentamethyl cyanine dyes are promising fluorophores for fluorescence sensing and imaging. However, advanced biomedical applications require enhanced control of their excited‐state properties. Herein, ...a synthetic approach for attaching aryl substituents at the C2’ position of the thio‐pentamethine cyanine (TCy5) dye structure is reported for the first time. C2’‐aryl substitution enables the regulation of both the twisted intramolecular charge transfer (TICT) and photoinduced electron transfer (PET) mechanisms to be regulated in the excited state. Modulation of these mechanisms allows the design of a nitroreductase‐activatable TCy5 fluorophore for hypoxic tumor photodynamic therapy and fluorescence imaging. These C2’‐aryl TCy5 dyes provide a tunable platform for engineering cyanine dyes tailored to sophisticated biological applications, such as photodynamic therapy.
This work reports a promising pentamethyl cyanine platform using C2’‐aryl substitutions. It is found that electron‐withdrawing groups enhanced twisted intramolecular charge transfer (TICT), resulting in efficient fluorescence quenching. The electron‐donating groups make the TICT tendency weaken significantly, while photoinduced electron transfer is enhanced. This change improves both the fluorescence quantum yield and the intersystem crossing (ISC) efficiency.
Abstract
Excited‐state intramolecular proton transfer (ESIPT)‐based solid luminescent materials with multiple hydrogen bond acceptors (HBAs) remain unexplored. Herein, we introduced a family of ...Janus‐type ESIPT chromophores featuring distinctive hydrogen bond (H‐bond) selectivity between competitive HBAs in a single molecule. Our investigations showed that the central hydroxyl group preferentially forms intramolecular H‐bonds with imines in imine‐modified 2‐hydroxyphenyl benzothiazole (HBT) chromophores but tethers the benzothiazole moiety in hydrazone‐modified HBT chromophores. Imine‐derived HBTs generally exhibit higher fluorescence efficiency, while hydrazone‐derived HBTs show a reduced overlap between the absorption and fluorescence bands. Quantum chemical calculations unveiled the molecular origins of the biased intramolecular H‐bonds and their impact on the ESIPT process. This Janus‐type ESIPT chromophore skeleton provides new opportunities for the design of solid luminescent materials.
Photoacoustic imaging (PAI), a state‐of‐the‐art noninvasive in vivo imaging technique, has been widely used in clinical disease diagnosis. However, the design of high‐performance PAI agents with ...three key characteristics, i.e., near‐infrared (NIR) absorption (λabs>800 nm), intense PA signals, and excellent photostability, remains a challenging goal. Herein, we present a facile but effective approach for engineering PAI agents by amplifying intramolecular low‐frequency vibrations and enhancing the push‐pull effect. As a demonstration of this blended approach, we constructed a PAI agent (BDP1‐NEt2) based on the boron‐dipyrromethene (BODIPY) scaffold. Compared with indocyanine green (ICG, an FDA‐approved organic dye widely utilized in PAI studies; λabs=788 nm), BDP1‐NEt2 exhibited a UV/Vis‐NIR spectrum peaked at 825 nm, superior in vivo PA signal intensity and outstanding stability to offer improved tumor diagnostics. We believe this work provides a promising strategy to develop the next generation of PAI agents.
In this work, we present a facile but effective approach for engineering photoacoustic imaging (PAI) agents by amplifying intramolecular low‐frequency vibrations and enhancing the push‐pull effect. As a demonstration of this blended approach, we constructed a PAI agent (BDP1‐NEt2) based on the boron‐dipyrromethene (BODIPY) scaffold, which met key requirements of high‐quality PAI.
Understanding the mechanisms of aggregation-induced emission (AIE) is essential for the rational design and deployment of AIEgens toward various applications. Such a deep mechanistic understanding ...demands a thorough investigation of the excited-state behaviors of AIEgens. However, because of considerable complexity and rapid decay, these behaviors are often not experimentally accessible and the mechanistic comprehension of many AIEgens is lacking. Herein, utilizing detailed quantum chemical calculations, we provide insights toward the AIE mechanism of 1-(N,N-dialkylamino)-naphthalene (DAN) derivatives. Our theoretical analysis, corroborated by experimental observations, leads to the discovery that modulating the formation of the twisted intramolecular charge transfer (TICT) state (caused by the rotation of the amino groups) and managing the steric hindrance to minimize solid-state intermolecular interactions provides a plausible explanation for the AIE characteristics of DAN derivatives. These results will inspire the deployment of the TICT mechanism as a useful design strategy toward AIEgen development.
Cyclooctatetraene (COT) attachment to fluorophores (“self-healing” dyes) is known for quenching reactive triplet states via triplet-state energy transfer (TET), enhancing photostability. However, ...COT's impact on singlet states remains unclear. Quantum calculations reveal that COT induces energy transfer to dark states in deep blue dyes while promoting photoinduced electron transfer (PET) and intersystem crossing (ISC) in visible dyes, potentially compromising brightness and/or photostability. To address this, we propose the use of ΔE descriptor to optimize COT's effects. Our findings uncover COT's multifaceted impact. These insights will guide the development of superior triplet state quenchers and photostable dyes.
Cyclooctatetraene (COT) plays a pivotal role in enhancing fluorophore photostability. However, it can also induce energy transfer to a dark state (ETDS) and photo-induced electron transfer (PET), leading to diminished brightness or compromised photostability. In this context, we introduce a ΔE descriptor to optimize the impact of the COT attachment to dyes.
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