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Biomedical Materials (Bristol, England) Feb 2021Fluorescence imaging technology in the second near-infrared bio-channel (NIR-II) has the advantages of low light scattering and weak autofluorescence. It can obtain high... (Review)
Review
Fluorescence imaging technology in the second near-infrared bio-channel (NIR-II) has the advantages of low light scattering and weak autofluorescence. It can obtain high spatial resolution imaging in deeper biological tissues and realize accurate diagnosis in the lesion. As a new cancer treatment method, photothermal therapy has the characteristics of obvious curative effect and small side effects. However, the hydrophobicity and non-selectivity of many fluorescent materials, aggregation-induced fluorescence quenching, and other problems lead to undesirable imaging results. Here, we reviewed the structure of the NIR-II fluorescent molecules and these dyes whose fluorescence tail emission is in the NIR-II bio-channel, discussed in detail how to realize the redshift of the dye wavelength, including modifying the push-pull electron system, extending the conjugated chain, and forming J-aggregates and other methods. We also summarize some strategies to improve brightness, including responsiveness, targeting, adjustment of aggregation mode, and aggregation-induced emission effect, thereby improving the imaging performance and therapeutic effect of NIR-II fluorescent dyes.
Topics: Colorectal Neoplasms; Contrast Media; Fluorescent Dyes; Humans; Hydrophobic and Hydrophilic Interactions; Liver; Microscopy, Fluorescence; Nanocomposites; Nanoparticles; Optical Imaging; Photochemistry; Polymers; Reproducibility of Results; Signal Transduction
PubMed: 33186922
DOI: 10.1088/1748-605X/abca4a -
Annual Review of Chemical and... Jun 2023In the past two decades, we have witnessed a rapid emergence of new and powerful photochemical and photocatalytic synthetic methods. Although these methods have been... (Review)
Review
In the past two decades, we have witnessed a rapid emergence of new and powerful photochemical and photocatalytic synthetic methods. Although these methods have been used mostly on a small scale, there is a growing need for efficient scale-up of photochemistry in the chemical industry. This review summarizes and contextualizes the advancements made in the past decade regarding the scale-up of photo-mediated synthetic transformations. Simple scale-up concepts and important fundamental photochemical laws have been provided along with a discussion concerning suitable reactor designs that should facilitate scale-up of this challenging class of organic reactions.
Topics: Photochemical Processes; Photochemistry
PubMed: 36913716
DOI: 10.1146/annurev-chembioeng-101121-074313 -
Environmental Science & Technology Dec 2022Photocatalysis is regarded as one of the most promising technologies for indoor volatile organic compounds (VOCs) elimination due to its low cost, safe operation, energy... (Review)
Review
Photocatalysis is regarded as one of the most promising technologies for indoor volatile organic compounds (VOCs) elimination due to its low cost, safe operation, energy efficiency, and high mineralization efficiency under ambient conditions. However, the practical applications of this technology are limited, despite considerable research efforts in recent decades. Until now, most of the works were carried out in the laboratory and focused on exploring new catalytic materials. Only a few works involved the immobilization of catalysts and the design of reactors for practical applications. Therefore, this review systematically summarizes the research and development on photocatalytic oxidation (PCO) of VOCs, with emphasis on recent catalyst's immobilization and reactor designs in detail. First, different types of photocatalytic materials and the mechanisms for PCO of VOCs are briefly discussed. Then, both the catalyst's immobilization techniques and reactor designs are reviewed in detail. Finally, the existing challenges and future perspectives for PCO of VOCs are proposed. This work aims to provide updated information and research inspirations for the commercialization of this technology in the future.
Topics: Volatile Organic Compounds; Air Pollution, Indoor; Photochemistry; Catalysis; Oxidation-Reduction
PubMed: 36367480
DOI: 10.1021/acs.est.2c05444 -
Macromolecular Rapid Communications Sep 2020Bioorthogonal chemistry is revolutionizing the fields of biological chemistry and nanomedicine, providing tools to actively probe and perturb native biochemical... (Review)
Review
Bioorthogonal chemistry is revolutionizing the fields of biological chemistry and nanomedicine, providing tools to actively probe and perturb native biochemical processes. Photochemistry provides the opportunity to actively and non-invasively control bioorthogonal reactions, providing sophisticated optochemical tools. Despite the opportunities in bioorthogonal photochemistry, there remain many significant challenges to the clinical translation of current research. This review aims to provide an overview of these challenges and highlight recent examples from the literature that are providing revolutionary solutions to overcoming these barriers. It will highlight new photochemical systems that can be triggered by near infrared light in aqueous solutions and have been demonstrated to function in complex biological systems, including in living animals. It will cover diverse classes of photochemical reactions including photopolymerization, uncaging, conjugation, and photoswitching. The discussion will detail how new approaches are being integrated into polymers or highlight unexploited opportunities. This review intends to showcase how the unique synergy of bioorthogonal photochemistry and polymer science provides vast opportunities in the fields of biomaterials, nanomedicine, and theranostics. This will hopefully provide inspiration to material scientists to integrate bioorthogonal photochemistry into new adaptable materials and ensure translation to solve clinical challenges.
Topics: Animals; Photochemistry; Polymers; Water
PubMed: 32656958
DOI: 10.1002/marc.202000305 -
Chem Sep 2023Recently, organic synthesis has seen a renaissance in radical chemistry due to the accessibility of mild methods for radical generation using visible light. While...
Recently, organic synthesis has seen a renaissance in radical chemistry due to the accessibility of mild methods for radical generation using visible light. While renewed interest in synthetic radical chemistry has been driven by the advent of photoredox catalysis, a resurgence of electron donor-acceptor (EDA) photochemistry has also led to many new radical transformations. Similar to photoredox catalysis, EDA photochemistry involves light-promoted single-electron transfer pathways. However, the mechanism of electron transfer in EDA systems is unique wherein the lifetimes of radical intermediates are often shorter due to competitive back-electron transfer. Distinguishing between EDA and photoredox mechanisms can be challenging since they can form identical products. In this perspective, we seek to provide insight on the mechanistic studies which can distinguish between EDA and photoredox manifolds. Additionally, we highlight some key challenges in EDA photochemistry and suggest future goals which could advance the synthetic potential of this field of research.
PubMed: 37873033
DOI: 10.1016/j.chempr.2023.06.013 -
Accounts of Chemical Research May 2022Cyclometalated iridium(III) complexes are frequently employed in organic light emitting diodes, and they are popular photocatalysts for solar energy conversion and... (Review)
Review
Cyclometalated iridium(III) complexes are frequently employed in organic light emitting diodes, and they are popular photocatalysts for solar energy conversion and synthetic organic chemistry. They luminesce from redox-active excited states that can have high triplet energies and long lifetimes, making them well suited for energy transfer and photoredox catalysis. Homoleptic tris(cyclometalated) iridium(III) complexes are typically very hydrophobic and do not dissolve well in polar solvents, somewhat limiting their application scope. We developed a family of water-soluble sulfonate-decorated variants with tailored redox potentials and excited-state energies to address several key challenges in aqueous photochemistry.First, we aimed at combining enzyme with photoredox catalysis to synthesize enantioenriched products in a cyclic reaction network. Since the employed biocatalyst operates best in aqueous solution, a water-soluble photocatalyst was needed. A new tris(cyclometalated) iridium(III) complex provided enough reducing power for the photochemical reduction of imines to racemic mixtures of amines and furthermore was compatible with monoamine oxidase (MAO-N-9), which deracemized this mixture through a kinetic resolution of the racemic amine via oxidation to the corresponding imine. This process led to the accumulation of the unreactive amine enantiomer over time. In subsequent studies, we discovered that the same iridium(III) complex photoionizes under intense irradiation to give hydrated electrons as a result of consecutive two-photon excitation. With visible light as energy input, hydrated electrons become available in a catalytic fashion, thereby allowing the comparatively mild reduction of substrates that would typically only be reactive under harsher conditions. Finally, we became interested in photochemical upconversion in aqueous solution, for which it was desirable to obtain water-soluble iridium(III) compounds with very high triplet excited-state energies. This goal was achieved through improved ligand design and ultimately enabled sensitized triplet-triplet annihilation upconversion unusually far into the ultraviolet spectral range.Studies of photoredox catalysis, energy transfer catalysis, and photochemical upconversion typically rely on the use of organic solvents. Water could potentially be an attractive alternative in many cases, but photocatalyst development lags somewhat behind for aqueous solution compared to organic solvent. The purpose of this Account is to provide an overview of the breadth of new research perspectives that emerged from the development of water-soluble -[Ir(ppy)] complexes (ppy = 2-phenylpyridine) with sulfonated ligands. We hope to inspire the use of some of these or related coordination compounds in aqueous photochemistry and to stimulate further conceptual developments at the interfaces of coordination chemistry, photophysics, biocatalysis, and sustainable chemistry.
Topics: Amines; Electrons; Energy Transfer; Iridium; Ligands; Organometallic Compounds; Photochemistry; Solvents; Water
PubMed: 35414170
DOI: 10.1021/acs.accounts.2c00075 -
Chemical Communications (Cambridge,... Sep 2021We explore the photochemistry of polymeric carbon nitride (CN), an archetypal organic photocatalyst, and derivatives of its structural monomer unit, heptazine (Hz).... (Review)
Review
We explore the photochemistry of polymeric carbon nitride (CN), an archetypal organic photocatalyst, and derivatives of its structural monomer unit, heptazine (Hz). Through spectroscopic studies and computational analysis, we have observed that Hz derivatives can engage in non-innocent hydrogen bonding interactions with hydroxylic species. The photochemistry of these complexes is influenced by intermolecular nπ*/ππ* mixing of non-bonding orbitals of each component and the relative energy of intermolecular charge-transfer (CT) states. Coupling of the former to the latter appears to facilitate proton-coupled electron transfer (PCET), resulting in biradical products. We have also observed that Hz derivatives exhibit an extremely rare inverted singlet/triplet energy splitting (Δ). In violation of Hund's multiplicity rules, the lowest energy singlet (S) is stabilized relative to the lowest triplet (T) electronic excited state. Exploiting this unique inverted Δ character has obvious implications for transformational discoveries in solid-state OLED lighting and photovoltaics. Harnessing this inverted Δ, paired with light-driven intermolecular PCET reactions, may enable molecular transformations relevant for applications ranging from solar energy storage to new classes of non-triplet photoredox catalysts for pharmaceutical development. To this end, we have explored the possibility of optically controlling the photochemistry of Hz derivatives using ultrafast pump-push-probe spectroscopy. In this case, the excited state branching ratios among locally excited states of the chromophore and the reactive intermolecular CT state can be manipulated with an appropriate secondary "push" excitation pulse. These results indicate that we can predictively redirect chemical reactivity with light in this system, which is an avidly sought achievement in the field of photochemistry. Looking forward, we anticipate future opportunities for controlling heptazine photochemistry, including manipulating PCET reactivity with a diverse array of substrates and optically delivering reducing equivalents with, for example, water as a partial source of electrons and protons. Furthermore, we wholly expect that, over the next decade, materials such as Hz derivatives, that exhibit inverted Δ character, will spawn a significant new research effort in the field of thin-film optoelectronics, where controlling recombination triplet excitonic states can play a critical role in determining device performance.
PubMed: 34528956
DOI: 10.1039/d1cc02745j -
Journal of Chemical Theory and... Jan 2024The tuning mechanism of pH can be extremely challenging to model computationally in complex biological systems, especially with respect to the photochemical properties....
The tuning mechanism of pH can be extremely challenging to model computationally in complex biological systems, especially with respect to the photochemical properties. This article reports a protocol aimed at modeling pH-dependent photodynamics using a combination of constant-pH molecular dynamics and semiclassical nonadiabatic molecular dynamics simulations. With retinal photoisomerization in Anabaena sensory rhodopsin (ASR) as a testbed, we show that our protocol produces pH-dependent photochemical properties, such as the isomerization quantum yield or decay rates. We decompose our results into single-titrated residue contributions, identifying some key tuning amino acids. Additionally, we assess the validity of the single protonation state picture to represent the system at a given pH and propose the most populated protein charge state as a compromise between cost and accuracy.
Topics: Photochemistry; Rhodopsin; Anabaena; Hydrogen-Ion Concentration
PubMed: 38198619
DOI: 10.1021/acs.jctc.3c00980 -
Chemical Society Reviews Oct 2021The progress of drug discovery and development is paced by milestones reached in organic synthesis. In the last decade, the advent of late-stage functionalization (LSF)... (Review)
Review
The progress of drug discovery and development is paced by milestones reached in organic synthesis. In the last decade, the advent of late-stage functionalization (LSF) reactions has represented a valuable breakthrough. Recent literature has defined these reactions as the chemoselective modification of complex molecules by means of C-H functionalization or the manipulation of endogenous functional groups. Traditionally, these diversifications have been accomplished by organometallic means. However, the presence of metals carries disadvantages related to their cost, environmental hazard and health risks. Fundamentally, green chemistry directives can help minimize such hazards through the development of metal-free LSF methodologies. In this review, we expand the current discussion on metal-free LSF reactions by providing an overview of C(sp)-H, and C(sp)-H functionalizations, as well as the utilization of heteroatom-containing functional groups as chemical handles. Selected topics such as metal-free cross-dehydrogenative coupling (CDC) reactions, organocatalysis, electrochemistry and photochemistry are also discussed. By writing the first review on metal-free LSF methodologies, we aim to highlight current advances in the field with examples that reveal specific challenges and solutions, as well as future research opportunities.
Topics: Drug Discovery; Metals; Photochemistry
PubMed: 34382989
DOI: 10.1039/d1cs00380a -
Proceedings of the National Academy of... Mar 2021Hole hopping through tryptophan/tyrosine chains enables rapid unidirectional charge transport over long distances. We have elucidated structural and dynamical factors...
Hole hopping through tryptophan/tyrosine chains enables rapid unidirectional charge transport over long distances. We have elucidated structural and dynamical factors controlling hopping speed and efficiency in two modified azurin constructs that include a rhenium(I) sensitizer, Re(His)(CO)(dmp), and one or two tryptophans (W, W). Experimental kinetics investigations showed that the two closely spaced (3 to 4 Å) intervening tryptophans dramatically accelerated long-range electron transfer (ET) from Cu to the photoexcited sensitizer. In our theoretical work, we found that time-dependent density-functional theory (TDDFT) quantum mechanics/molecular mechanics/molecular dynamics (QM/MM/MD) trajectories of low-lying triplet excited states of Re(His)(CO)(dmp)-W(-W) exhibited crossings between sensitizer-localized (*Re) and charge-separated [Re(His)(CO)(dmp)/(W or W)] (CS1 or CS2) states. Our analysis revealed that the distances, angles, and mutual orientations of ET-active cofactors fluctuate in a relatively narrow range in which the cofactors are strongly coupled, enabling adiabatic ET. Water-dominated electrostatic field fluctuations bring *Re and CS1 states to a crossing where *Re(CO)(dmp)←W ET occurs, and CS1 becomes the lowest triplet state. ET is promoted by solvation dynamics around *Re(CO)(dmp)(W); and CS1 is stabilized by Re(dmp)/W electron/hole interaction and enhanced W solvation. The second hop, W←W, is facilitated by water fluctuations near the W/W unit, taking place when the electrostatic potential at W drops well below that at W Insufficient solvation and reorganization around W make W←W ET endergonic, shifting the equilibrium toward W and decreasing the charge-separation yield. We suggest that multiscale TDDFT/MM/MD is a suitable technique to model the simultaneous evolution of photogenerated excited-state manifolds.
Topics: Azurin; Electron Transport; Electrons; Molecular Dynamics Simulation; Oxidation-Reduction; Photochemistry; Pseudomonas aeruginosa; Quantum Theory; Rhenium; Static Electricity; Tryptophan; Water
PubMed: 33836608
DOI: 10.1073/pnas.2024627118