SwePub - sökning: L773:2367 0932

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1.	Benitez-Martin, Carlos, 1994, et al. (författare) Fluorescent Molecular Photoswitches for the Generation of All-Optical Encryption Keys 2023 Ingår i: Chemphotochem. - 2367-0932. Tidskriftsartikel (refereegranskat)abstract Herein, we report a tri-component photochromic molecular cocktail that can be used to encrypt and decrypt information. The time-dependent fluorescent response of this cocktail is highly non-linear with respect to the set of inputs used (concentrations of the three photochromic components, excitation- and emission wavelengths), a property required for the generation of so-called encryption keys. The all-optical system can generate more than 80 million unique fluorescence responses by applying different input combinations and is operated using a conventional fluorimeter.
2.	Björk, Linnea, et al. (författare) Amino-Acid Side-Chain Nanoarchitectonics for Tuning the Chiroptical Properties and Supramolecular Structure of Pentameric Oligothiophenes 2024 Ingår i: ChemPhotoChem. - : WILEY-V C H VERLAG GMBH. - 2367-0932. Tidskriftsartikel (refereegranskat)abstract Oligothiophenes with specific photophysical properties and molecular organization are of great interest, since this class of materials are used in organic electronics and bioelectronics, as well as biosensing. Herein, 8 different pentameric oligothiophenes, denoted proteophenes, with different amino acid substitution patterns at distinct positions along the thiophene backbone were investigated. Spectroscopic and microscopic studies of the ligands revealed the formation of optically active self-assembled materials under acidic or basic conditions. The distinct photophysical characteristics, including induced circular dichroism, as well as the supramolecular structures of the assemblies deduced from light scattering and transmission electron microscopy, were highly influenced by the positioning of distinct amino acid moieties along the thiophene backbone. Proteophenes functionalized with only glutamate residues or these functionalities in combination with hydrophobic valine moieties formed fibrillar structures with excellent chiroptical properties under acidic conditions. In addition, the amino acid functionality at the beta-position of distinct thiophene moieties influenced the induced circular dichroism pattern observed from the proteophenes. Overall, the obtained results demonstrate how changes in the position of various amino acid functionalities, as well as the chemical nature of the amino acid side chain functionality greatly affect the optical properties as well as the architecture of the self-assembled materials. Self-assembled Proteophenes. Oligothiophenes with distinct amino acid side-chain functionalities along the conjugated backbone displayed distinct chiroptical and structural properties in acidic or alkaline solutions. The distinct photophysical characteristics, as well as the supramolecular structures of the assemblies were highly influenced by the chemical nature of the amino acid, as well as the positioning of distinct amino acid moieties along the thiophene backbone.image
3.	Blaise, Nadine, et al. (författare) Isomerization dynamics of a novel cis/trans-only merocyanine 2024 Ingår i: ChemPhotoChem. - 2367-0932. ; 8:3 Tidskriftsartikel (refereegranskat)abstract Merocyanines (MC) usually adopt ring opened zwitterionic structures that are interconvertible with their ring-closed spiropyran photoisomers. By methylating the phenolate oxygen, and thereby blocking the ring-closure reaction, a cis/trans-only MC photoswitch was obtained, yielding a perfect candidate for a detailed examination of the cis/trans isomerization mechanism for this class of compounds. This photoswitch displays outstanding properties including excellent photoreaction quantum yields and photoswitching turnovers. Due to the central polymethine bridge of MC, in principle eight cis (C)/trans (T) isomers are possible. Density Functional Theory (DFT) calculations revealed the CCT and TTT-isomers of the studied compound as most stable cis and trans ground state isomers, respectively. UV/vis transient absorption studies combined with conical intersection computations with the complete active space self-consistent field (CASSCF) method show that both trans/cis- and cis/trans-photoisomerizations are initiated by a rotation of the central doubled bond fragment. A hot ground state species is then formed, which undergoes a second isomerization. Thus, the cis/trans reaction proceeds via a CCT-CTT-TTT sequence and the reverse reaction via TTT-TCT-CCT.
4.	Bozal-Ginesta, Carlota, et al. (författare) Self-Recovery of Photochemical H2 Evolution with a Molecular Diiron Catalyst Incorporated in a UiO-66 Metal-Organic Framework 2020 Ingår i: ChemPhotoChem. - : Wiley. - 2367-0932. ; 4:4, s. 287-290 Tidskriftsartikel (refereegranskat)abstract Photochemical hydrogen evolution from a UiO‐66‐incorporated Fe2(dcbdt)(CO)6 catalyst in conjunction with a ruthenium photosensitizer and an ascorbate donor ceases after a period of irradiation, but is restored after a 60 min. resting period in the dark. Control experiments show that neither product inhibition nor pore clogging is responsible for this surprising behaviour, and intra‐crystal linker scrambling is proposed as a potential explanation.
5.	Colas, Kilian, et al. (författare) Photophysical Characteristics of Polarity-Sensitive and Lipid Droplet-Specific Phenylbenzothiadiazoles 2021 Ingår i: ChemPhotoChem. - : Wiley. - 2367-0932. ; 5:7, s. 632-643 Tidskriftsartikel (refereegranskat)abstract In this study, we present a series of solvatochromic phenylbenzothiadiazoles that display dual emission from the locally excited (LE) and intramolecular charge transfer (ICT) excited states. The donor-acceptor derivatives are highly sensitive to polarity changes, which can be monitored by differences in emission efficiency, spectroscopic shifts and variations of the LE/ICT ratio. One of the compounds in the series, containing a thiomethyl substituent, emerged as an excellent blue emitting stain for intracellular lipid droplets, a biomarker for various types of cancer. In addition, a non-emissive nitro derivative becomes fluorescent upon bioreduction in hypoxic cancer cells and accumulates in lipid droplets with a high signal-to-background ratio.
6.	Corbella, Marina, et al. (författare) Spectral Variability in Phycocyanin Cryptophyte Antenna Complexes is Controlled by Changes in the alpha-Polypeptide Chains 2019 Ingår i: ChemPhotoChem. - : WILEY-V C H VERLAG GMBH. - 2367-0932. ; 3:9, s. 945-956 Tidskriftsartikel (refereegranskat)abstract Quantitative models of light harvesting in photosynthetic antenna complexes depend sensitively on the challenging determination of the relative site energies of the pigments. Herein we analyze the basis of the light harvesting properties of four antennae from cryptophyte algae, phycocyanines PC577, PC612, PC630 and PC645, by comparing two alternative theoretical strategies to derive the excitonic Hamiltonian. The first is based on molecular dynamics simulations and subsequent polarizable quantum/molecular mechanics (QM/MMPol) calculations, whereas the second is based on three-layer QM/MMPol/ddCOSMO calculations performed on optimized geometries of the pigments, where the water solvent is described using the ddCOSMO continuum model. We find the latter approach to be remarkably accurate, suggesting that these four phycobiliproteins share a common energetic ordering PCB82 < PCB158 < DBV51/61 for pigments located in the highly-conserved beta chains, whereas bilins in the more divergent alpha chains cause their spectral differences. In addition, we predict a strong screening of the coupling among central dihydrobiliverdins (DBVs) in "open" form complexes PC577 and PC612 compared to "closed" form ones, which together with the increased interpigment separation explains the attenuation of coherence beatings observed for these complexes.
7.	Doloczki, Susanne, et al. (författare) An Indolin-3-imine Photobase and pH Sensitive Fluorophore 2023 Ingår i: ChemPhotoChem. - : John Wiley & Sons. - 2367-0932. Tidskriftsartikel (refereegranskat)abstract This work presents the pH sensing ability of a fluorescent indolin-3-imine derivative. Protonation of the weakly basic imine (pKa = 8.3 of its conjugate acid) results in a significant redshift of the absorption band. The fluorophore acts as a photobase, with a basicity increase of approximately 6 units upon photoexcitation. This behavior promotes excited state proton transfer from weak acids such as protic solvents. The characteristics of the fluorophore enable sensing of water fractions in organic solvents and differentiation between methanol, ethanol, and longer chain alcohols. Initial cell studies indicated the future potential of indolin-3-imines as fluorophores for bioimaging applications.
8.	Falklöf, Olle, 1986-, et al. (författare) Computational Identification of Pyrrole Ring C as the Preferred Donor for Excited-State Proton Transfer in Bacteriophytochromes 2018 Ingår i: ChemPhotoChem. - Weinheim, Germany : Wiley-VCH Verlagsgesellschaft. - 2367-0932. ; 2:6, s. 453-457 Tidskriftsartikel (refereegranskat)abstract The engineering of bacteriophytochrome photoreceptors into near-infrared fluorescent proteins is a promising route toward deep-tissue imaging of living cells with many challenges ahead. One key objective is to increase the fluorescence quantum yields, which are limited by competing non-radiative relaxation processes involving not only the well-known double-bond photoisomerization of the tetrapyrrole chromophore, but also a potential excited-state proton transfer from the chromophore to the protein. Motivated by the lack of mechanistic knowledge about this proton transfer, we here use hybrid quantum mechanics/molecular mechanics methods to investigate three possible scenarios for how the process is initiated. Through calculated excited-state pKa values of the chromophore inside the protein matrix of Deinococcus radiodurans bacteriophytochrome, it is found that pyrrole ring C is a much more likely donor for excited-state proton transfer than rings A and B, which are also possible donors discussed in the literature. This finding offers a starting point for establishing a strategy to strengthen the fluorescence of engineered bacteriophytochromes through biochemical inhibition of the proton transfer.
9.	Fernández Galván, Ignacio, 1977-, et al. (författare) Chemiexcitation without the Peroxide Bond? : Replacing oxygen with other heteroatoms 2019 Ingår i: ChemPhotoChem. - : Wiley. - 2367-0932. ; 3:9, s. 957-967 Tidskriftsartikel (refereegranskat)abstract Chemiexcitation is the population of electronic excited states from the electronic ground state via radiationless non-adiabatic transitions upon thermal activation. The subsequent emission of the excess of energy in the form of light is called chemiluminescence or bioluminescence when occurring in living organisms. Key intermediates in these reactions have been shown to contain a high-energy (often cyclic) peroxide which decomposes. The simplest molecules, 1,2-dioxetane and 1,2-dioxetanone, have thus been used extensively both theoretically and experimentally as model systems to understand the underlying mechanisms of chemiexcitation. An outstanding question remains whether the peroxide bond is a necessity and whether equivalent processes could happen in other simple molecules not containing an OO bond. In the present work, the decomposition reactions of four analogs of 1,2-dioxetane not containing a peroxide bond, the 1,2-oxazetidine anion, the 1,2-diazetidine anion, (neutral) 1,2-oxazetidine and 1,2-dithietane, have been studied theoretically using ab initio multicongurational methods. In particular, the reaction energy barriers and spin-orbit coupling strengths were calculated; the electronic degeneracy was studied and compared to the case of 1,2-dioxetane to assess the potentiality of chemiexcitation in the analog molecules.
10.	Fleming, Cassandra L., et al. (författare) On-Command Regulation of Kinase Activity using Photonic Stimuli 2019 Ingår i: ChemPhotoChem. - : Wiley. - 2367-0932. ; 3:6, s. 318-326 Forskningsöversikt (refereegranskat)abstract The underlying role that many kinases play in complex cellular pathways as well as disease remains unclear. To better understand the role that kinases play in both health and disease states, the use of light as an external stimulus to modulate kinase activity with high spatiotemporal resolution has gained increasing interest over the years. Herein we highlight the progress made towards the development of light-responsive kinase enzymes and small molecule inhibitors. In these examples, photolabile caging groups and photoswitchable entities have been utilised to modulate either kinase activation or inhibition in a light-controlled manner.
11.	Gotfredsen, Henrik, et al. (författare) Donor-Acceptor-Functionalized Subphthalocyanines for Dye-Sensitized Solar Cells 2018 Ingår i: ChemPhotoChem. - : Wiley-VCH Verlagsgesellschaft. - 2367-0932. ; 2:11, s. 976-985 Tidskriftsartikel (refereegranskat)abstract Boron subphthalocyanines (SubPcs) are attractive as light harvesting materials in photovoltaic devices. Here we present the synthesis, optical and electrochemical properties, and device performances of a series of donor-acceptor-functionalized SubPc derivatives incorporating a carboxylic acid for anchoring onto TiO2. Liquid- and solid-state dye-sensitized solar cells (DSCs) were prepared from three compounds, and a triad system consisting of two aniline donor moieties and a benzothiadiazole acceptor moiety was found to exhibit the highest power conversion efficiency (PCE) in the series (PCE=1.54 %; solid-state device). The compounds were prepared by stepwise acetylenic coupling reactions. In addition, we present the synthesis and optical properties of a SubPc derivative incorporating three anilino-substituted 1,1,4,4-tetracyanobutadiene units, prepared by the [2+2] cycloaddition between three ethynyl units at the SubPc periphery and three tetracyanoethylene molecules followed by electrocyclic ring-opening reactions.
12.	Gryszel, Maciej, et al. (författare) Water-Soluble Cationic Perylene Diimide Dyes as Stable Photocatalysts for H2O2 Evolution 2023 Ingår i: ChemPhotoChem. - : WILEY-V C H VERLAG GMBH. - 2367-0932. ; 7:9 Tidskriftsartikel (refereegranskat)abstract Photocatalytic generation of hydrogen peroxide, H2O2, has gained increasing attention in recent years, with applications ranging from solar energy conversion to biophysical research. While semiconducting solid-state materials are normally regarded as the workhorse for photogeneration of H2O2, an intriguing alternative for on-demand H2O2 is the use of photocatalytic organic dyes. Herein we report the use of water-soluble dyes based on perylene diimide molecules which behave as true molecular catalysts for the light-induced conversion of dissolved oxygen to hydrogen peroxide. In particular, we address how to obtain visible-light photocatalysts which are stable with respect to aggregation and photochemical degradation. We report on the factors affecting efficiency and stability, including variable electron donors, oxygen partial pressure, pH, and molecular catalyst structure. The result is a perylene diimide derivative with unprecedented peroxide evolution performance using a broad range of organic donor molecules and operating in a wide pH range.
13.	Hageberg, Ingvild U., et al. (författare) Photophysics of Glycosylated Ring-Fused Chlorin Complexes and Their Photosensitizing Effects on Cancer Cells 2023 Ingår i: ChemPhotoChem. - : WILEY-V C H VERLAG GMBH. - 2367-0932. ; 7:8 Tidskriftsartikel (refereegranskat)abstract The future of photodynamic therapy (PDT) as a promising cancer treatment relies on the development of new selective and effective photosensitizers (PS) with improved photophysical and biochemical qualities. Herein, we present the synthetic procedure, photophysical properties and photosensitizing effects of novel glycosylated 4,5,6,7-tetrahydropyrazolo[1,5-a]pyridine] fused chlorin agents featuring either glucose, galactose, or N-acetyl glucosamine. It is shown that both the proto- and Zn2+-ion forms of the ring-stabilized glycochlorins exhibit the required photophysical properties in terms of triplet excited states and singlet oxygen generation, the latter more than 50 % in organic solvents such as CHCl3. Employing the rat AY-27 and human T24 cancer cell models, it was found that these are superior to the corresponding unglycosylated chlorin in biological activity, and moreover, the proto form is 2-3 times superior to the Zn-stabilized variant. Provisional flow cytometry and cell localization studies of the proto-form indicate both necrotic and apoptotic biological activity, and that the photosensitizer localizes in the mitochondria, cell membrane and lysosomes. However, the localization into the lysosomes is dominating and increases substantially with time. We anticipate the findings will aid in the development of photosensitizers for targeted cancer PDT.
14.	Harriman, Anthony, et al. (författare) Capturing the Light Fantastic 2018 Ingår i: ChemPhotoChem. - : Wiley-VCH Verlagsgesellschaft. - 2367-0932. ; 2:3, s. 110-111 Tidskriftsartikel (refereegranskat)
15.	Hertzog, Manuel, 1989, et al. (författare) The Effect of Coupling Mode in the Vibrational Strong Coupling Regime 2020 Ingår i: Chemphotochem. - : Wiley. - 2367-0932. ; 4:8, s. 612-7 Tidskriftsartikel (refereegranskat)abstract Hybrid light-matter states, known as polaritons, are the result of strong coupling between light and matter. The formation of polaritons yields a new method to tune the energetics of molecular systems, thus enabling the modification of physical and chemical properties without the need for chemical synthesis. To date, only proof-of-principle studies have been demonstrated, and, to increase the relevance of earlier achievements, bridging the gap between quantum electrodynamic length scales and chemical synthesis length scales is necessary. In the present study, we show that the coupling strength of the light-matter interaction is independent of the thickness of the Fabry-Perot cavity used, and that the energy dissipation rate falls with increasing cavity thickness. Using planar microcavities of different thicknesses, we have shown that the size of the cavities can be upscaled without reducing the strength of the strong interaction between light and matter. This can be done up to a length scale commonly used in flow chemistry, thus paving the way for a new optofluidic method that may help to overcome challenges in organic chemistry.
16.	Liu, Peng, et al. (författare) Cross-linked sulfur-selenium polymers as hole transporting materials in dye-sensitized solar cells and perovskite solar cells 2017 Ingår i: ChemPhotoChem. - : Wiley-VCH Verlagsgesellschaft. - 2367-0932. ; 1:8, s. 363-368 Tidskriftsartikel (refereegranskat)abstract Novel inverse-vulcanized polymeric sulfur–selenium materials (SeS2:S:DIB, where DIB=1,3-diisopropenylbenzene) have been prepared and utilized for solid-state dye-sensitized solar cellsand perovskite solar cells. Under standard AM 1.5G illumination (1000 Wm-2), a power conversion efficiency of 1.70% was recorded for polymeric sulfur–selenium–based (SeS2:S:DIB) solidstate solar cells, which is higher than that of polymeric sulfurbased (S:DIB) devices (1.09 %). For perovskite solar cells, a relatively high efficiency has been achieved for polymeric sulfur–selenium-based (SeS2:S:DIB) solar cells (10.21%) and polymeric sulfur-based (S:DIB; 7.32%) solar cells, respectively. The conductivity of the polymeric SeS material has been determined to 2.2410-4 Scm-1, which is higher than for the polymeric sulfur material under the same doping conditions. Photoinduced absorption and steady-state photoluminescence measurements were performed to investigate the charge-transfer properties relevant for the solar cells. The results in the present study qualify the new polymeric sulfur–selenium materials as candidates for low-cost hole-transport materials for photovoltaic devices.
17.	Mallo, Neil, et al. (författare) Hydrogen-Bonding Donor-Acceptor Stenhouse Adducts 2020 Ingår i: ChemPhotoChem. - : Wiley. - 2367-0932. ; 4:6, s. 407-412 Tidskriftsartikel (refereegranskat)abstract The binding of donor-acceptor Stenhouse adducts (DASAs) bearing hydrogen-bond recognition groups by Hamilton-type receptors significantly influenced their photoswitching properties by altering thermal barriers to isomerization. The thermal barrier between the most stable linear isomer and the photogenerated isomer is lowered on binding to a receptor, and this barrier is crucial for switching properties. The thermal isomerization was shown to proceed via a stepwise linear-enol-keto mechanism in DMSO where the tautomerisation barrier is within 2 kJ . mol(-1) of that of the rate-determining step, which may be important for analyzing switching properties.
18.	Singh, Veena, et al. (författare) Scalable InkJet-Based Additive Fabrication of Photocatalytic TiO2 Thin Films 2022 Ingår i: ChemPhotoChem. - : Wiley. - 2367-0932. ; 6:3 Tidskriftsartikel (refereegranskat)abstract Photocatalysts for water purification and energy production belong to the class of materials for which there is an urgent need for more environmentally friendly manufacturing. Here we report a high throughput method for inkjet printing of nanostructured photocatalytically active TiO2 films and a detailed analysis of their properties and photocatalytic performance. We show that the inkjet dispersion of TiO2 particles is highly reproducible which leads to a close to linear relation between the number of printed single layers and the thickness of the films. The films here obtained have uniform surfaces and the interfaces with the substrates are free from defects such as grain boundaries, ripples, or discontinuities. This contrasts with films obtained with the traditional doctor blade method. The inkjet printed films have higher photocatalytic performance than the doctor blade films which results in higher catalytic activity per mass of material used. Lifetime tests with wet and dry cycles show that the inkjet films subjected to 10 photocatalytic cycles of 100 minutes each have a loss of performance of only 7 %, while the films made via the doctor blade method have a performance loss of 66 %. These tests revealed additionally that the mechanical stability of the inkjet films is higher than that of the films manufactured via the traditional casting method. This set of results shows that inkjet printing can be an efficient method for the large-scale production of TiO2 photocatalysts.
19.	Skov, Anders B., et al. (författare) Excited‐State Topology Modifications of the Dihydroazulene Photoswitch Through Aromaticity 2019 Ingår i: ChemPhotoChem. - : Wiley. - 2367-0932. ; 3:8, s. 619-629 Tidskriftsartikel (refereegranskat)abstract The gain and loss of aromaticity plays a key role in organic chemistry and in the prediction of rate‐determining steps. Herein, we explore the concept of aromaticity in photoisomerization reactions. Benzannulated derivatives of the dihydroazulene‐vinylheptafulvene (DHA‐VHF) photoswitch were investigated using transient absorption spectroscopy and time‐dependent density functional theory to elucidate the effect of built‐in aromaticity on the switching properties. We found that benzannulation hampered the switching ability by enhancing an already existing barrier on the excited state surface. This enhancement was found to arise from a significant loss of aromaticity in the DHA‐to‐VHF transition state on the excited state potential energy surface. The VHF was found to be highly aromatic on the excited state surface, showing a reversal of aromaticity compared to the ground state. The barrier was found to be dependent on the position of benzannulation, since one derivative was found to switch as fast as the non‐benzannulated molecule although with lower efficiency, whereas another derivative completely lost the ability to undergo reversible photoswitching. The findings herein provide novel principles for the design of molecular photoswitches, shedding new light on excited state aromaticity, as previous discussions have mainly considered excited state aromaticity to be beneficial to switching. Our findings show that this view must be reconsidered.
20.	Thillaiarasi, T., et al. (författare) Polycyclic Heteroaromatic p-Linkers Provide Dithienylethene Switches with Favorable Thermal and Photochemical Properties for Solar-Energy Storage 2024 Ingår i: ChemPhotoChem. - : WILEY-V C H VERLAG GMBH. - 2367-0932. Tidskriftsartikel (refereegranskat)abstract Dithienylethene photoswitches with an aromatic pi-linker as the bridge between the two thiophene units are attractive starting materials for developing molecular solar thermal energy (MOST) storage systems, partly because the aromaticity of their ring-open forms is a favorable feature with regard to the energy-storage densities of their ring-closed forms produced by photoinduced electrocyclization (photocyclization) reactions. At the same time, this typically leads to small barriers for their thermal cycloreversion reactions, which are not desirable in this context. Here, we use computational methods to show that this problem can be circumvented with polycyclic heteroaromatic pi-linkers. Specifically, through the tuning of the aromatic character of the individual rings of such a pi-linker (like indole or isoindole), it is shown to be possible to strike a delicate balance between the seemingly contrasting requirements of simultaneously achieving both a high energy-storage density and a large cycloreversion barrier. Furthermore, this design is also found to provide for a quick and efficient photocyclization reaction, owing to the onset of excited-state antiaromaticity in the pi-linker upon light absorption of the ring-open form. Altogether, dithienylethenes with polycyclic heteroaromatic pi-linkers appear to have both thermal and photochemical properties suitable for further development into future MOST systems. Through the incorporation of a polycyclic heteroaromatic pi-linker between their thiophene units, dithienylethene switches are shown computationally to exhibit a photocyclization reaction well exploitable for solar-energy storage, while also occupying a sweet spot for such applications where contrasting requirements on energy-storage densities and thermal cycloreversion barriers can be met. image
21.	Wang, Jun, 1983-, et al. (författare) A Straightforward Route to Aromatic Excited States in Molecular Motors that Improves Photochemical Efficiency 2019 Ingår i: ChemPhotoChem. - Weinheim, Germany : Wiley-VCH Verlagsgesellschaft. - 2367-0932. ; 3:6, s. 450-460 Tidskriftsartikel (refereegranskat)abstract The many successful efforts to optimize the thermal steps that are part of the reaction cycles of most light-driven rotary molecular motors have not been followed by studies providing a similarly detailed understanding of how the efficiency of the photochemical steps that actually power the motors can be improved. Against this background, we herein use computational methods to investigate the merits of an approach to increase the quantum yields of E/Z-photoisomerization-based motors by enabling one of their two moieties to become aromatic in the photoactive excited state. Through quantum chemical calculations, a straightforward route to excited states of this type is found for motors where one moiety can be transformed into an aromatic anion by an electron donor at the other moiety. Furthermore, through molecular dynamics simulations, motors operated in such excited states are indeed predicted to be much more efficient than similar motors operated in the absence of excited-state aromaticity.
22.	Wang, Jun, et al. (författare) Thermal Fluctuations in Conjugation and their Effect on Calculated Excitation Energies : A Case Study on the Astaxanthin Carotenoid 2022 Ingår i: ChemPhotoChem. - Weinheim, Germany : Wiley-VCH Verlagsgesellschaft. - 2367-0932. ; 6:1 Tidskriftsartikel (refereegranskat)abstract A popular approach to the calculation of molecular excitation energies is to consider only equilibrium geometries and neglect the effects of thermal motion. Although this static approach is sensible for molecules with distinct potential-energy minima, its adequacy relative to dynamical approaches appears not to have been thoroughly tested. Here, we report a case study investigating how thermal motion accounted for by molecular dynamics simulations influences the optically bright state of astaxanthin, a carotenoid of broad photobiological interest that features 13 conjugated double bonds. Employing several different density functional methods, it is shown that thermal fluctuations in the conjugation result in the Boltzmann-weighted average excitation energies for this state being shifted by up to 0.05 eV relative to those obtained from purely static calculations. Accordingly, it is concluded that the effects of thermal motion on excitation energies of conjugated systems can be quite large even for molecules with distinct potential-energy minima.
23.	Zobel, J. Patrick, et al. (författare) Nonadiabatic Dynamics Simulation Predict Intersystem Crossing in Nitroaromatic Molecules on a Picosecond Time Scale 2019 Ingår i: ChemPhotoChem. - : Wiley. - 2367-0932. ; 3:9, s. 833-845 Tidskriftsartikel (refereegranskat)abstract Previous time-resolved spectroscopic experiments and static quantum-chemical calculations attributed nitronaphthalene derivatives one of the fastest time scales for intersystem crossing within organic molecules, reaching the 100 fs mark. Nonadiabatic dynamics simulations on three nitronaphthalene derivatives challenge this view, showing that the experimentally observed ∼100 fs process corresponds to internal conversion in the singlet manifolds. Intersystem crossing, instead, takes place on a longer time scale of ∼1 ps. The dynamics simulations further reveal that the spin transitions occur via two distinct pathways with different contribution for the three systems, which are determined by electronic factors and the torsion of the nitro group. This study, therefore, indicates that the existence of sub-picosecond intersystem crossing in other nitroaromatic molecules should be questioned.

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