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Bloom, B. P.; Lu, Y.; Metzger, Tzuriel; Yochelis, Shira; Paltiel, Yossi; Fontanesi, Claudio; Mishra, Suryakant; Tassinari, Francesco; Naaman, Ron; Waldeck, D. H.
doi: 10.1039/d0cp03129apmid: 32697241
Essential aspects of the chiral induced spin selectivity (CISS) effect and their implications for spin-controlled chemistry and asymmetric electrochemical reactions are described. The generation of oxygen through electrolysis is discussed as an example in which chirality-based spin-filtering and spin selection rules can be used to improve the reaction's efficiency and selectivity. Next the discussion shifts to illustrate how the spin selectivity of chiral molecules (CISS properties) allows one to use the electron spin as a chiral bias for inducing asymmetric reactions and promoting enantiospecific processes. Two enantioselective electrochemical reactions that have used polarized electron spins as a chiral reagent are described; enantioselective electroreduction to resolve an enantiomer from a racemic mixture and an oxidative electropolymerization to generate a chiral polymer from achiral monomers. A complementary approach that has used spin-polarized, but otherwise achiral, molecular films to enantiospecifically associate with one enantiomer from a racemic mixture is also discussed. Each of these reaction types use magnetized films to generate the spin polarized electrons and the enantiospecificity can be selected by choice of the magnetization direction, North pole versus South pole. Possible paths for future research in this area and its compatibility with existing methods based on chiral electrodes are discussed.
Derr, James B.; Tamayo, Jesse; Clark, John A.; Morales, Maryann; Mayther, Maximillian F.; Espinoza, Eli M.; Rybicka-Jasińska, Katarzyna; Vullev, Valentine I.
doi: 10.1039/d0cp01556cpmid: 32785306
Charge transfer and charge transport are by far among the most important processes for sustaining life on Earth and for making our modern ways of living possible. Involving multiple electron-transfer steps, photosynthesis and cellular respiration have been principally responsible for managing the energy flow in the biosphere of our planet since the Great Oxygen Event. It is impossible to imagine living organisms without charge transport mediated by ion channels, or electron and proton transfer mediated by redox enzymes. Concurrently, transfer and transport of electrons and holes drive the functionalities of electronic and photonic devices that are intricate for our lives. While fueling advances in engineering, charge-transfer science has established itself as an important independent field, originating from physical chemistry and chemical physics, focusing on paradigms from biology, and gaining momentum from solar-energy research. Here, we review the fundamental concepts of charge transfer, and outline its core role in a broad range of unrelated fields, such as medicine, environmental science, catalysis, electronics and photonics. The ubiquitous nature of dipoles, for example, sets demands on deepening the understanding of how localized electric fields affect charge transfer. Charge-transfer electrets, thus, prove important for advancing the field and for interfacing fundamental science with engineering. Synergy between the vastly different aspects of charge-transfer science sets the stage for the broad global impacts that the advances in this field have.
doi: 10.1039/d0cp02994gpmid: 32969457
In describing the dynamics of electron transfer or charge transport, the reorganization energy and the spectral density function describe the influence of nuclei motion to the transporting electron. The spectral density can be obtained using various theoretical approaches: from a model of dielectric response, or calculated with various computational means. With the vast advancement of modern computational techniques, many details in vibronic coupling can be obtained, including those described in the early literature. In this work, we provide a comprehensive understanding of the nature of vibronic coupling in light of some early literature. The theoretical connection among different quantities for vibronic coupling is discussed, followed by a brief review of the spectral density function. Various approaches and some of the results for the spectral density function are also reviewed. The importance of low-frequency bands in nonpolar systems that can be overlooked is also discussed, for both Holstein and Peierls types of electron–phonon couplings.
Mollart, Catherine; Trewin, Abbie
doi: 10.1039/d0cp03539dpmid: 32968748
Conjugated microporous polymers (CMPs) synthesised in different solvents give different surface areas dependent on the solvent choice. No one solvent results in a high surface area across a range of different CMP materials. Here, we present an investigation into how the porosity of CMPs is affected by solvent polarity. It is seen that the trends differ depending on the respective monomer dipole moments and whether hydrogen bonding groups are present in the monomers and are able to interact with the respective solvent via hydrogen bonding. It is believed that this methodology could be used to influence future materials design of both structure and synthesis strategy.
Takahashi, Hiroaki; Yanamisawa, Aya; Kajimoto, Shinji; Nakabayashi, Takakazu
doi: 10.1039/d0cp03805apmid: 32985622
We report the dynamics of lipid droplet formation induced by introducing cis- and/or trans-fatty acids into cells. Raman imaging allows the chemical analysis of each droplet, showing that exogenous fatty acids initially enter original endogenous droplets, then induce additional droplets containing endogenous lipids, and finally form their droplets.
Panchagnula, Sanjana; Bouwman, Jordy; Rap, Daniël B.; Castellanos, Pablo; Candian, Alessandra; Mackie, Cameron; Banhatti, Shreyak; Brünken, Sandra; Linnartz, Harold; Tielens, Alexander G. G. M.
doi: 10.1039/d0cp02272apmid: 32729589
The vibrationally resolved spectra of the pyrene cation and doubly-dehydrogenated pyrene cation (C16H10˙+; Py+ and C16H8˙+; ddPy+) are presented. Infrared predissociation spectroscopy is employed to measure the vibrational spectrum of both species using a cryogenically cooled 22-pole ion trap. The spectrum of Py+ allows a detailed comparison with harmonic and anharmonic density functional theory (DFT) calculated normal mode frequencies. The spectrum of ddPy+ is dominated by absorption features from two isomers (4,5-ddPy+ and 1,2-ddPy+) with, at most, minor contributions from other isomers. These findings can be extended to explore the release of hydrogen from interstellar PAH species. Our results suggest that this process favours the loss of adjacent hydrogen atoms.
Wang, Kang-Kyun; Song, Sanggeun; Jung, Seung-Jin; Hwang, Jung-Wook; Kim, Min-Goo; Kim, Ji-Hyun; Sung, Jaeyoung; Lee, Jin-Kyu; Kim, Yong-Rok
doi: 10.1039/d0cp00739kpmid: 32608420
Singlet oxygen is a toxic chemical but powerful oxidant, exploited in many chemical and biological applications. However, the lifetime of singlet oxygen in air under atmospheric conditions is yet to be known. This has limited safe usage of singlet oxygen in air, despite being a strong antimicrobial agent with the unique property of relaxing to breathable oxygen after serving its purpose. Here, we solve this long-standing problem by combining experimental and theoretical research efforts; we generate singlet oxygen using a photosensitizer at a local source and monitor the time-dependent extent of singlet oxygen reaction with probe molecules at a detector, precisely controlling the detector distance from the source. To explain our experimental results, we employ a theoretical model that fully accounts for singlet oxygen diffusion, radiative and nonradiative relaxations, and the bimolecular reaction with probe molecules at the detector. For all cases investigated, our model, with only two adjustable parameters, provides an excellent quantitative explanation of the experiment. From this analysis, we extract the lifetime of singlet oxygen in the air to be 2.80 s at 23 °C under 1 atm, during which time singlet oxygen diffuses about 0.992 cm. The correctness of this estimation is confirmed by a simple mean-first-passage time analysis of the maximum distance singlet oxygen can reach from the source. We also confirm the sterilization effects of singlet oxygen for distances up to 0.6–0.8 cm, depending on the bacteria strain in question, between the bacteria and the singlet oxygen source.
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