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Chemphyschem : a European Journal of... May 2024The properties of sub-nano metal clusters are governed by quantum confinement and their large surface-to-bulk ratios, atomically precise compositions and... (Review)
Review
The properties of sub-nano metal clusters are governed by quantum confinement and their large surface-to-bulk ratios, atomically precise compositions and geometric/electronic structures. Advances in metal clusters lead to new opportunities in diverse aspects of sciences including chemo-sensing, bio-imaging, photochemistry, and catalysis. Naked metal clusters having synergic multiple active sites and coordinative unsaturation and tunable stability/activity enable researchers to design atomically precise metal catalysts with tailored catalysis for different reactions. Here we summarize the progress of ligand-free naked metal clusters for catalytic applications. It is anticipated that this review helps to better understand the chemistry of small metal clusters and facilitates the design and development of new catalysts for potential applications.
PubMed: 38450926
DOI: 10.1002/cphc.202300715 -
Nature Chemistry May 2024During the past 15 years, an increasing number of research groups have embraced visible-light-mediated synthetic transformations as a powerful strategy for the... (Review)
Review
During the past 15 years, an increasing number of research groups have embraced visible-light-mediated synthetic transformations as a powerful strategy for the construction and functionalization of organic molecules. This trend has followed the advent and development of photocatalysis, which often operates under mild visible-light irradiation. Nowadays, the general perception of UV-light photochemistry is often as an out-of-fashion approach that is difficult to perform and leads to unselective reaction pathways. Here we wish to propose an alternative and more realistic point of view to the scientific community. First, we will provide an overview of the use of UV light in modern photochemistry, highlighting the pivotal role it still plays in the development of new, efficient synthetic methods. We will then show how the high levels of mechanistic understanding reached for UV-light-driven processes have been key in the implementation of the related visible-light-driven transformations.
PubMed: 38429343
DOI: 10.1038/s41557-024-01472-6 -
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 -
Frontiers in Chemistry 2024Since the dawn of photochemistry 150 years ago, photoreactions have been conducted under polychromatic light. However, despite the pivotal role that photokinetics should...
Since the dawn of photochemistry 150 years ago, photoreactions have been conducted under polychromatic light. However, despite the pivotal role that photokinetics should naturally play for such reactive photosystems, the literature lacks a comprehensive description of that area. Indeed, one fails to identify explicit model integrated rate laws for these reactions, a characteristic type for their kinetic behavior, or their kinetic order. In addition, there is no consensus in the community on standardized investigative tools to evaluate the reactivity of these photosystems, nor are there venues for the discussion of such photokinetic issues. The present work is a contribution addressing some of these knowledge gaps. It proposes an unprecedented general formula capable of mapping out the kinetic traces of photoreactions under polychromatic light irradiation. This article quantitatively discusses several reaction situations, including the effects of initial reactant concentration and the presence of spectator molecules. It also develops a methodology for standardizing actinometers and defines and describes both the spectral range of highest reactivity and the photonic yield. The validity of the model equation has been proven by comparing its results to both theoretical counterparts and those generated by fourth-order Runge-Kutta numerical calculations. For the first time, a confirmation of the -order character of the kinetics under polychromatic light was established.
PubMed: 38711947
DOI: 10.3389/fchem.2024.1367276 -
Chemical Reviews Aug 2023When molecules are coupled to an optical cavity, new light-matter hybrid states, so-called polaritons, are formed due to quantum light-matter interactions. With the... (Review)
Review
When molecules are coupled to an optical cavity, new light-matter hybrid states, so-called polaritons, are formed due to quantum light-matter interactions. With the experimental demonstrations of modifying chemical reactivities by forming polaritons under strong light-matter interactions, theorists have been encouraged to develop new methods to simulate these systems and discover new strategies to tune and control reactions. This review summarizes some of these exciting theoretical advances in polariton chemistry, in methods ranging from the fundamental framework to computational techniques and applications spanning from photochemistry to vibrational strong coupling. Even though the theory of quantum light-matter interactions goes back to the midtwentieth century, the gaps in the knowledge of molecular quantum electrodynamics (QED) have only recently been filled. We review recent advances made in resolving gauge ambiguities, the correct form of different QED Hamiltonians under different gauges, and their connections to various quantum optics models. Then, we review recently developed ab initio QED approaches which can accurately describe polariton states in a realistic molecule-cavity hybrid system. We then discuss applications using these method advancements. We review advancements in polariton photochemistry where the cavity is made resonant to electronic transitions to control molecular nonadiabatic excited state dynamics and enable new photochemical reactivities. When the cavity resonance is tuned to the molecular vibrations instead, ground-state chemical reaction modifications have been demonstrated experimentally, though its mechanistic principle remains unclear. We present some recent theoretical progress in resolving this mystery. Finally, we review the recent advances in understanding the collective coupling regime between light and matter, where many molecules can collectively couple to a single cavity mode or many cavity modes. We also lay out the current challenges in theory to explain the observed experimental results. We hope that this review will serve as a useful document for anyone who wants to become familiar with the context of polariton chemistry and molecular cavity QED and thus significantly benefit the entire community.
PubMed: 37552606
DOI: 10.1021/acs.chemrev.2c00855 -
The Review of Scientific Instruments Aug 2023Every material experiences atomic and molecular motions that are generally termed vibrations in gases and liquids or phonons in solid state materials. Optical...
Every material experiences atomic and molecular motions that are generally termed vibrations in gases and liquids or phonons in solid state materials. Optical spectroscopy techniques, such as Raman, infrared absorption spectroscopy, or inelastic neutron scattering (INS), can be used to measure the vibrational/phonon spectrum of ground state materials properties. A variety of optical pump probe spectroscopies enable the measurement of excited states or elucidate photochemical reaction pathways and kinetics. So far, it has not been possible to study photoactive materials or processes in situ using INS due to the mismatch between neutron and photon penetration depths, differences between the flux density of photons and neutrons, cryogenic temperatures for INS measurements, vacuum conditions, and a lack of optical access to the sample space. These experimental hurdles have resulted in very limited photochemistry studies using INS. Here we report on the design of two different photochemistry sample sticks that overcome these experimental hurdles to enable in situ photochemical studies using INS, specifically at the VISION instrument at Oak Ridge National Laboratory. We demonstrate the use of these new measurement capabilities through (1) the in situ photodimerization of anthracene and (2) the in situ photopolymerization of a 405 nm photoresin using 405 nm excitation as simple test cases. These new measurement apparatus broaden the science enabled by INS to include photoactive materials, optically excited states, and photoinitiated reactions.
PubMed: 37540123
DOI: 10.1063/5.0154605 -
The Journal of Physical Chemistry. B Dec 2023A DNA strand can encapsulate a silver molecule to create a nanoscale, aqueous stable chromophore. A protected cluster that strongly fluoresces can also be weakly...
A DNA strand can encapsulate a silver molecule to create a nanoscale, aqueous stable chromophore. A protected cluster that strongly fluoresces can also be weakly photolabile, and we describe the laser-driven photochemistry of the green fluorophore CACTCGT/Ag. The embedded cluster is selectively photoexcited at 490 nm and then bleached, and we describe how the efficiency, products, and route of this photochemical reaction are controlled by the DNA cage. With irradiation at 496.5 nm, the cluster absorption progressively drops to give a photodestruction quantum yield of 1.5 (±0.2) × 10, ∼10× less efficient than fluorescence. A new λ = 335 nm chromophore develops because the precursor with 4 Ag is converted into a group of clusters with 2 Ag - Ag, Ag, Ag, and Ag. The 4-7 Ag in this series are chemically distinct from the 2 Ag because they are selectively etched by iodide. This halide precipitates silver to favor only the smallest Ag cluster, but the larger clusters re-develop when the precipitated Ag ions are replenished. DNA-bound Ag decomposes because it is electronically excited and then reacts with oxygen. This two-step process may be state-specific because O quenches the red luminescence from Ag. However, the rate constant of 2.3 (±0.2) × 10 M s is relatively small, which suggests that the surrounding DNA matrix hinders O diffusion. On the basis of analogous photoproducts with methylene blue, we propose that a reactive oxygen species is produced and then oxidizes Ag to leave behind a loose Ag-DNA skeleton. These findings underscore the ability of DNA scaffolds to not only tune the spectra but also guide the reactions of their molecular silver adducts.
PubMed: 38054435
DOI: 10.1021/acs.jpcb.3c06358 -
Physical Chemistry Chemical Physics :... Jul 2023The elusive hydrogen-bonded radical complex (˙SH⋯NH) consisting of ammonia (NH) and a mercapto radical (˙SH) has been generated through the 193 nm laser photolysis...
The elusive hydrogen-bonded radical complex (˙SH⋯NH) consisting of ammonia (NH) and a mercapto radical (˙SH) has been generated through the 193 nm laser photolysis of the molecular complex between NH and hydrogen sulfide (HS) in solid Ar- and N-matrixes at 10 K. The identification of ˙SH⋯NH with matrix-isolation IR spectroscopy and UV-vis spectroscopy is supported by N- and D-isotope labeling experiments and quantum chemical calculations at the B3LYP-D3(BJ)/6-311++G(3df,3pd) level of theory. In line with a large red shift of -172.2 cm for the frequency of the S-H stretching mode observed in ˙SH⋯NH ( free ˙SH), the radical ˙SH acts as a hydrogen donor, and NH acts as an acceptor. According to the calculations at the CCSD(T)/aug-cc-pVTZ level, the SH⋯N bonded structure ˙SH⋯NH (binding energy = 3.9 kcal mol) is more stable than the isomeric amidogen radical complex HSH⋯˙NH ( = 2.8 kcal mol) by 16.6 kcal mol. This is in sharp contrast to the photochemistry of the closely related HOH⋯NH complex, since the water-amidogen radical complex HOH⋯˙NH ( = 5.1 kcal mol) was generated under similar photolysis conditions, whereas the ammonia-hydroxyl radical complex ˙OH⋯NH ( = 7.9 kcal mol) is higher in energy by 9.3 kcal mol.
PubMed: 37387234
DOI: 10.1039/d3cp01689g -
Chemical Record (New York, N.Y.) Sep 2023In the last few years, many reagents and protocols have been developed to allow for the efficient fluorofunctionalization of a diverse set of scaffolds ranging from... (Review)
Review
In the last few years, many reagents and protocols have been developed to allow for the efficient fluorofunctionalization of a diverse set of scaffolds ranging from alkanes, alkenes, alkynes, and (hetero)arenes. The concomitant rise of organofluorine chemistry and visible light-mediated synthesis have synergistically expanded the fields and have mutually benefitted from developments in both fields. In this context, visible light driven formations of radicals containing fluorine have been a major focus for the discovery of new bioactive compounds. This review details the recent advances and progress made in visible light-mediated fluoroalkylation and heteroatom centered radical generation.
PubMed: 37212421
DOI: 10.1002/tcr.202300104 -
Chemical Communications (Cambridge,... Oct 2023Photochromic conducting molecules have emerged because of their unique capacity to modulate electrical conductivity upon exposure to light, toggling between high and low... (Review)
Review
Photochromic conducting molecules have emerged because of their unique capacity to modulate electrical conductivity upon exposure to light, toggling between high and low conductive states. This unique amalgamation has unlocked novel avenues for the application of these materials across diverse areas in optoelectronics and smart materials. The fundamental mechanism underpinning this phenomenon is based on the light-driven isomerization of conjugated π-systems which influences the extent of conjugation. The photoisomerization process discussed here involves photochromic switches such as azobenzenes, diarylethenes, spiropyrans, dimethyldihydropyrenes, and norbornadiene. The change in the degree of conjugation alters the charge transport in both single molecules and bulk states in solid samples or solutions. This article discusses a number of recent examples of photochromic conducting systems and the challenges and potentials of the field.
PubMed: 37814882
DOI: 10.1039/d3cc04269c