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Photoconvertible tracking strategies assess the dynamic migration of cell populations. Here we develop

Water-soluble photosensitizers based on covalently grafted nitrogen-doped graphene quantum dot–BODIPY for cellular imaging and photodynamic therapy.

A new photochemical mechanism, termed proton-coupled energy transfer (PCEnT), was recently discovered in anthracene-phenol-pyridine triads (Pettersson Rimgard et al., Science 2022, 377, 742). It couples an electronic transition to nuclear motions allowing Förster (dipole-dipole) energy transfer even though there is no overlap of the donor emission and acceptor absorption spectra. Here, we extend this concept to triplet-triplet energy transfer (TEnT) from light-harvesting porphyrin to a covalently bound flavonol group. While direct TEnT to the flavonol acceptor would be highly endergonic, it becomes feasible thanks to the flavonol energy stabilization upon intramolecular proton transfer in the triplet state. We describe the overall mechanism as proton-coupled TEnT (PCTEnT) – a one-photon process that enables the activation of a UV-absorbing chromophore by visible light. Several porphyrin-flavonol hybrids containing 4 flavonol units attached to the porphyrin meso positions were designed as photoactivatable carbon monoxide (CO)-releasing molecules (photoCORMs). The photoreaction mechanism was studied by steady-state and transient absorption spectroscopy techniques and complementary quantum-chemical calculations. While intrinsically toxic, CO is an endogenous signaling molecule with therapeutic potential that regulates various physiological processes, and photoCORMs offer precise spatial and temporal control of CO administration. We evaluated the viability of the human hepatoblastoma HepG2 cells in the presence of the studied hybrids and tested the effects associated with the intracellular release of CO and the production of singlet oxygen. We demonstrate that the PCTEnT process could be used to devise new photoactivatable molecular devices with potential biological applications.

Fluorescein, eosin Y, and rose bengal are dyes used in clinical medicine and considered (photo-)chemically stable. Upon extensive irradiation with visible light in aqueous solutions, we found that these compounds release carbon monoxide (CO) - a bioactive gasotransmitter - in 40-100% yields along with the production of low-mass secondary photoproducts, such as phthalic and formic acids, in a multistep degradation process. Such photochemistry should be considered in applications of these dyes, and they could also be utilized as visible-light activatable CO-releasing molecules (photoCORMs) with biological implications.

We report the design of easily accessible, photocleavable meso-methyl BODIPY monomers suitably functionalised for incorporation into macromolecules. Firstly a BODIPY-diol as a novel AA-type bifunctional monomer is reported. Secondly, from the same common BODIPY precursor, a clickable, azide functionalised AB-type hetero-bifunctional monomer was prepared. Photochemical studies of model compounds confirmed the ability of these compounds to undergo photocleavage in green light (lambda > 500 nm). Their usefulness for photoclippable macromolecular systems is then demonstrated: firstly by incorporating the diols into polyurethane hydrogels shown to undergo photocleavage and hence dissolution under visible light irradiation and secondly, the preparation of water-soluble macromolecular photocages able to photorelease small molecules. Thus the results presented herein describe a proof-of-principle for BODIPY-based photoresponsive materials, for example, for use as degradable polymers, sacrificial materials for lithography or for the delivery of caged pharmaceuticals.

The photochemistry of bilirubin has been extensively studied due to its importance in the phototherapy of hyperbilirubinemia. In the present work, we investigated the ultrafast photodynamics of a bilirubin dipyrrinone subunit, vinylneoxanthobilirubic acid methyl ester. The photoisomerization and photocyclization reactions of its (E) and (Z) isomers were studied using femtosecond transient absorption spectroscopy and by multireference electronic structure theory, where the nonadiabatic dynamics was modeled with a Landau-Zener surface hopping technique. The following picture has emerged from the combined theoretical and experimental approach. Upon excitation, dipyrrinone undergoes a very fast vibrational relaxation, followed by an internal conversion on a picosecond time scale. The internal conversion leads either to photoisomerization or regeneration of the starting material. Further relaxation dynamics on the order of tens of picoseconds was observed in the ground state. The nonadiabatic simulations revealed a strong conformational control of the photodynamics. The ultrafast formation of a cyclic photochemical product from a less-populated conformer of the studied subunit was predicted by our calculations. We discuss the relevance of the present finding for the photochemistry of native bilirubin. The work has also pointed to the limits of semiclassical nonadiabatic simulations for simulating longer photochemical processes, probably due to the zero-point leakage issue.

Heptamethine cyanines (Cy7) are fluorophores essential for modern bioimaging techniques and chemistry. Here, we systematically evaluated the photochemical and photophysical properties of a library of Cy7 derivatives containing diverse substituents in different positions of the heptamethine chain. A single substitution allows modulation of their absorption maxima in the range of 693-805 nm and photophysical properties, such as quantum yields of singlet-oxygen formation, decomposition, and fluorescence or affinity to singlet oxygen, within 2-3 orders of magnitude. The same substituent in different positions of the chain often exhibits distinctly contradictory effects, demonstrating that both the type and position of the substituent are pivotal for the design of Cy7-based applications. The combination of experimental results with quantum-chemical calculations provides insights into the structure-property relationship, the elucidation of which will accelerate the development of cyanines with properties tailored for specific applications, such as fluorescent probes and sensors, photouncaging, photodynamic therapy, or singlet-oxygen detection.

Many serious diseases are associated with degenerative changes caused by oxidative stress triggered by elevated concentrations of reactive oxygen species (ROS) in cells. Therefore, the development of suitable probes for monitoring such processes is of great importance. Here, we introduce a series of sulfur- and selenium-substituted BODIPY derivatives as reversible redox sensors for ROS and enzymatic redox processes. Significant differences in emission maxima and fluorescence quantum yields between the reduced and oxidized forms make them excellent ratiometric turn-on/off probes. Installation of polar sulfonate groups improved their aqueous solubility while retaining their sensing properties, which allowed the probes to monitor the enzymatic activity of enantioselective methionine sulfoxide reductase.

Carbon monoxide (CO) is an endogenous signaling molecule that regulates diverse physiological processes. The therapeutic potential of CO is hampered by its intrinsic toxicity, and its administration poses a significant challenge. Photoactivatable CO-releasing molecules (photoCORMs) are an excellent tool to overcome the side effects of untargeted CO administration and provide precise spatial and temporal control over its release. Here, we studied the CO release mechanism of a small library of derivatives based on 3-hydroxy-2-phenyl-4

Irradiation of coumarin-3-carboxylic acid in acetonitrile and methanol solutions at 355 nm results in complex multistep photochemical transformations, strongly dependent on the solvent properties and oxygen content. A number of reaction intermediates, which themselves undergo further (photo)chemical reactions, were identified by steady-state and transient absorption spectroscopy, mass spectrometry, and NMR and product analyses. The triplet excited compound in acetonitrile undergoes decarboxylation to give a 3-coumarinyl radical that traps molecular oxygen to form 3-hydroxycoumarin as the major but chemically reactive intermediate. This compound is oxygenated by singlet oxygen, produced by coumarin-3-carboxylic acid sensitization, followed by a pyrone ring-opening reaction to give an oxalic acid derivative. The subsequent steps lead to the production of salicylaldehyde, carbon monoxide, and carbon dioxide as the final products. When 3-coumarinyl radical is not trapped by oxygen in degassed acetonitrile, it abstracts hydrogen from the solvent and undergoes triplet-sensitized [2 + 2] cycloaddition. The reaction of 3-coumarinyl radical with oxygen is largely suppressed in aerated methanol as a better H-atom donor, and coumarin is obtained as the primary product in good yields. Because coumarin derivatives are used in many photophysical and photochemical applications, this work provides detailed and sometimes surprising insights into their complex phototransformations.

Bilirubin (BR) is an essential metabolite formed by the catabolism of heme. Phototherapy with blue-green light can be applied to reduce high concentrations of BR in blood and is used especially in the neonatal period. In this work, we studied the photochemistry of (

Xanthene derivatives are organic dyes, some of which are routinely used in different chemical and biological applications, including human medicine. In this work, we investigated the photochemistry of some of the most common ones, fluorescein, eosin Y, and rose bengal, and major products of their photodegradation using optical spectroscopy, NMR, chromatography and mass spectroscopy techniques. These substances, usually considered (photo)chemically stable, were found to liberate carbon monoxide (CO) in 40–80% chemical yields upon extensive irradiation with visible light in aqueous solutions during their multistep concomitant degradation processes. In addition, a number of low-mass secondary photoproducts, such as phthalic and formic acids, were identified in the irradiated mixtures. We demonstrate that these common fluorescent dyes can also be considered as visible-light activatable carbon monoxide (CO)-releasing molecules (photoCORMs) under specific conditions with potential biological implications.

Fluorescein is a fluorescent dye used as a diagnostic tool in various fields of medicine. Although fluorescein itself possesses low toxicity, after photoactivation, it releases potentially toxic molecules, such as singlet oxygen (O-1(2)) and, as we demonstrate in this work, also carbon monoxide (CO). As both of these molecules can affect physiological processes, the main aim of this study was to explore the potential biological impacts of fluorescein photochemistry. In our in vitro study in a human hepatoblastoma HepG2 cell line, we explored the possible effects on cell viability, cellular energy metabolism, and the cell cycle. We observed markedly lowered cell viability (approximate to 30%, 75-2400 mu M) upon irradiation of intracellular fluorescein and proved that this decrease in viability was dependent on the cellular oxygen concentration. We also detected a significantly decreased concentration of Krebs cycle metabolites (lactate and citrate < 30%; 2-hydroxyglutarate and 2-oxoglutarate < 10%) as well as cell cycle arrest (decrease in the G2 phase of 18%). These observations suggest that this photochemical reaction could have important biological consequences and may account for some adverse reactions observed in fluorescein-treated patients. Additionally, the biological activities of both O-1(2) and CO might have considerable therapeutic potential, particularly in the treatment of cancer. Fluorescein is a fluorescent dye used as a diagnostic tool in various fields of medicine. Although fluorescein itself possesses low toxicity, after photoactivation, it releases potentially toxic molecules, such as singlet oxygen (O-1(2)) and, as we demonstrate in this work, also carbon monoxide (CO). As both of these molecules can affect physiological processes, the main aim of this study was to explore the potential biological impacts of fluorescein photochemistry. In our in vitro study in a human hepatoblastoma HepG2 cell line, we explored the possible effects on cell viability, cellular energy metabolism, and the cell cycle. We observed markedly lowered cell viability (approximate to 30%, 75-2400 mu M) upon irradiation of intracellular fluorescein and proved that this decrease in viability was dependent on the cellular oxygen concentration. We also detected a significantly decreased concentration of Krebs cycle metabolites (lactate and citrate < 30%; 2-hydroxyglutarate and 2-oxoglutarate < 10%) as well as cell cycle arrest (decrease in the G2 phase of 18%). These observations suggest that this photochemical reaction could have important biological consequences and may account for some adverse reactions observed in fluorescein-treated patients. Additionally, the biological activities of both O-1(2) and CO might have considerable therapeutic potential, particularly in the treatment of cancer.

Carbon monoxide (CO) is a cell-signaling molecule (gasotransmitter) produced endogenously by oxidative catabolism of heme, and the understanding of its spatial and temporal sensing at the cellular level is still an open challenge. Synthesis, optical properties, and study of the sensing mechanism of Nile red Pd-based CO chemosensors, structurally modified by core and bridge substituents, in methanol and aqueous solutions are reported in this work. The sensing fluorescence "off-on" response of palladacycle-based sensors possessing low-background fluorescence arises from their reaction with CO to release the corresponding highly fluorescent Nile red derivatives in the final step. Our mechanistic study showed that electron-withdrawing and electron-donating core substituents affect the rate-determining step of the reaction. More importantly, the substituents were found to have a substantial effect on the Nile red sensor fluorescence quantum yields, hereby defining the sensing detection limit. The highest overall fluorescence and sensing rate enhancements were found for a 2-hydroxy palladacycle derivative, which was used in subsequent biological studies on mouse hepatoma cells as it easily crosses the cell membrane and qualitatively traces the localization of CO within the intracellular compartment with the linear quantitative response to increasing CO concentrations.

Cyanine dyes play an indispensable and central role in modern fluorescence-based biological techniques. Despite their importance and widespread use, the current synthesis methods of heptamethine chain modification are restricted to coupling reactions and nucleophilic substitution at the meso position in the chain. Herein, we report the direct transformation of Zincke salts to cyanine dyes under mild conditions, accompanied by the incorporation of a substituted pyridine residue into the heptamethine scaffold. This work represents the first general approach that allows the introduction of diverse substituents and different substitution patterns at the C3'-C5' positions of the chain. High yields, functional tolerance, versatility toward the condensation partners, and scalability make this method a powerful tool for accessing a new generation of cyanine derivatives.

Monitoring enzymatic activities at pH ranges compatible with their physiological optimum using fluorescent assays is important for high-throughput screening and engineering of novel biocatalysts as...

The sensitization of lanthanide-doped upconversion nanocrystals (UCNCs) using organic dyes with a broad and intense optical absorption is an interesting approach for efficient excitation-energy harvesting and enhancing the upconversion luminescence of such UCNCs. In this work, an ultrasmall (∼6.5 nm in diameter) β-NaGdF$_{4}$:Yb$^{3+}$,Er$^{3+}$ core and related core@shell UCNCs were sensitized using six NIR-excitable cyanine dyes with a wide range of functional groups and optical properties. The greatest UC enhancement of 680-times was observed for the conjugate between the Cy 754 dye and β-NaGdF$_{4}$:Yb$^{3+}$,Er$^{3+}$@NaGdF$_{4}$:10%Yb$^{3+},30%Nd$^{3+} core@shell UCNCs excited using a 754 nm laser. The enhancement was estimated relative to NaGdF$_{4}$:Yb$^{3+}$,Er$^{3+}$@NaGdF$_{4}$:10%Yb$^{3+},30%Nd$^{3+} core@shell UCNCs capped with oleic acid and excited using a similar intensity (75 W cm$^{-2}$) of a 980 nm laser. UC intensity measurements for identical dye-sensitized UCNCs carried out in methanol and in deuterated methanol under argon, as well as in air, allowed us to reveal the connection of the dye triplet states with UCNC sensitization as well as of the hydroxyl groups with quenching of the excited states of lanthanide ions. For UCNCs dispersed in methanol, the strong quenching UC luminescence was always observed, including core@shell UCNCs (with a shell of ∼2 nm). A strong influence of the triplet states of the dyes was observed for the two dyes Cy 754 and Cy 792 that bind firmly to UCNCs and allow the distances between the dye and the UCNC to be reduced, whereas the contribution of this sensitization pathway is very insignificant for Cy 740 and Cy 784 dyes that bind weakly to UCNCs.

Phototherapy is a standard treatment for severe neonatal jaundice to remove toxic bilirubin from the blood. Here, the wavelength-dependent photochemistry of vinylneoxanthobilirubic acid methyl ester, a simplified model of a bilirubin dipyrrinone subunit responsible for a lumirubin-like structural rearrangement, was thoroughly investigated by liquid chromatography and mass and absorption spectroscopies, with the application of a multivariate curve resolution analysis method supplemented with quantum chemical calculations. Irradiation of the model chromophore leads to reversible Z → E photoisomerization followed by reversible photocyclization to a seven-membered ring system (formed as a mixture of diastereomers). Both the isomerization processes are efficient (ΦZE ∼ ΦEZ ∼ 0.16) when irradiated in the wavelength range of 360-410 nm, whereas the E-isomer cyclization (Φc = 0.006-0.008) and cycloreversion (Φ-c = 0.002-0.004) reactions are significantly less efficient. The quantum yields of all processes were found to depend strongly on the wavelength of irradiation, especially when lower energy photons were used. Upon irradiation in the tail of the absorption bands (490 nm), both the isomers exhibit more efficient photoisomerization (ΦZE ∼ ΦEZ ∼ 0.30) and cyclization (Φc = ∼0.07). In addition, the isomeric bilirubin dipyrrinone subunits were found to possess important antioxidant activities while being substantially less toxic than bilirubin.

Aromatic amines are aquatic contaminants for which phototransformation in surface waters can be induced by excited triplet states of dissolved organic matter (3DOM*). The first reaction step is assumed to consist of a one-electron oxidation process of the amine to produce its radical cation. In this paper, we present laser flash photolysis investigations aimed at characterizing the photoinduced, aqueous phase one-electron oxidation of 4-(dimethylamino)benzonitrile (DMABN) as a representative of this contaminant class. The production of the radical cation of DMABN (DMABN˙+) after direct photoexcitation of DMABN at 266 nm was confirmed in accord with previous experimental results. Moreover, DMABN˙+ was shown to be produced from the reactions of several excited triplet photosensitizers (carbonyl compounds) with DMABN. Second-order rate constants for the quenching of the excited triplet states by DMABN were determined to fall in the range of 3 × 107–5 × 109 M−1 s−1, and their variation was interpreted in terms of electron transfer theory using a Rehm–Weller relationship. The decay kinetics of DMABN˙+ in the presence of oxygen was dominated by a second-order component attributed to its reaction with the superoxide radical anion (O2˙−). The first-order rate constant for the transformation of DMABN˙+ leading to photodegradation of DMABN was estimated not to exceed ≈5 × 103 s−1.

Leaving groups attached to the meso-methyl position of many common dyes, such as xanthene, BODIPY, or pyronin derivatives, can be liberated upon irradiation with visible light. However, the course of phototransformations of such photoactivatable systems can be quite complex and the identification of reaction intermediates or even products is often neglected. This paper exemplifies the photochemistry of a 9-dithianyl-pyronin derivative, which undergoes an oxidative transformation at the meso-position to give a 3,6-diamino-9H-xanthen-9-one derivative, formic acid, and carbon monoxide as the main photoproducts. The course of this multi-photon multi-step reaction was studied under various conditions by steady-state and time-resolved optical spectroscopy, mass spectrometry and NMR spectroscopy to understand the effects of solvents and molecular oxygen on individual steps. Our analyses have revealed the existence of many intermediates and their interrelationships to provide a complete picture of the transformation, which can bring new inputs to a rational design of new photoactivatable pyronin or xanthene derivatives. Odstupující skupiny připojené k meso-methyl pozici mnoha běžných barviv (např. xanthen, BOPIDY nebo deriváty pyroninu) mohou odstupovat při ozáření viditelným světlem. Nicméně proces fototransformace takových fotoaktivovatelných systémů může být poměrně složitý a tak identifikace reakčních meziproduktů nebo dokonce produktů je často opomíjena. Tato publikace osvětluje fotochemii derivátu 9-dithianylpyroninu, který podléhá oxidativní transformaci na meso-pozici za vzniku 3,6-diamino-9H-xanthen-9-onu, kyseliny mravenčí a oxidu uhelnatého jako hlavních fotoproduktů. Průběh této multifotonové vícestupňové reakce byl studován za různých podmínek optickou spektroskopií v ustáleném a časově rozlišeném spektru, hmotnostní spektrometrií a NMR spektroskopií za účelem pochopení vlivu rozpouštědel a molekulárního kyslíku na jednotlivé kroky. Naše analýzy odhalily existenci mnoha meziproduktů a jejich vztahy poskytují celkový obraz transformace, která může přinést nové informace pro desing nových fotoaktivovatelných derivátů pyroninu a xanthenu.

Nucleosides, nucleotides and 2'-deoxyribonucleoside triphosphates (dNTPs) containing 5-(hydroxy-methyl) uracil protected with photocleavable groups (2-nitrobenzyl-, 6-nitropiperonyl or 9-anthrylmethyl) were prepared and tested as building blocks for the polymerase synthesis of photocaged oligonucleotides and DNA. Photodeprotection (photorelease) reactions were studied in detail on model nucleoside mono-phosphates and their photoreaction quantum yields were determined. Photocaged dNTPs were then tested and used as substrates for DNA polymerases in primer extension or PCR. DNA probes containing photocaged or free 5-hydroxymethylU in the recognition sequence of restriction endonucleases were prepared and used for the study of photorelease of caged DNA by UV or visible light at different wavelengths. The nitropiperonyl-protected nucleotide was found to be a superior building block because the corresponding dNTP is a good substrate for DNA polymerases, and the protecting group is efficiently cleavable by irradiation by UV or visible light (up to 425 nm).

A combined experimental and computational approach was used to investigate the spectroscopic properties of three different aniline derivatives (aniline, N,N-dimethylaniline, and N,N-diethylaniline) in aqueous solutions and at the air–ice interface in the temperature range of 243–298 K. The absorption and diffuse reflectance spectra of ice samples prepared by different techniques, such as slow or shock freezing of the aqueous solutions or vapor deposition on ice grains, exhibited unequivocal bathochromic shifts of 10–15 nm of the absorption maxima of anilines in frozen samples compared to those in liquid aqueous solutions. DFT and SCS-ADC(2) calculations showed that contaminant–contaminant and contaminant–ice interactions are responsible for these shifts. Finally, we demonstrate that irradiation of anilines in the presence of a hydrogen peroxide/O2 system by wavelengths that overlap only with the red-shifted absorption tails of anilines in frozen samples (while having a marginal overlap with their spectra ...

Carbon monoxide is a naturally occurring gasotransmitter combining inherent toxicity with a remarkable therapeutic potential and arduous administration. Photoactivatable carbon monoxide-releasing molecules (photoCORMs) are chemical agents that allow for precise spatial and temporal control over the CO release. In this work, we present a comprehensive mechanistic study of the photochemical CO release from 3-hydroxy-2-phenyl-4H-chromen-4-one, a π-extended 3-hydroxyflavone photoCORM, in methanol using steady-state and transient absorption spectroscopies and quantum chemical calculations. The multiplicity of the productive excited states and the role of oxygen (O2) in the CO production are emphasized, revealing a photoreaction dichotomy of the 3-hydroxyflavone acid and base forms. The utilization of three major orthogonal mechanistic pathways, all of which lead to the CO release, can fuel future endeavors to improve the CO release efficacy of 3-hydroxyflavone-based derivatives and refine their potential medical applications as photoCORMs.

Natural ice and snow are always contaminated by diverse inorganic and organic species, many of which can undergo photochemical transformations under solar radiation or react with photochemically produced reactive species. The courses of these reactions are often phase-specific and strongly depend on many factors, such as phase properties of a frozen aqueous matrix, the wavelength and intensity of light, the absorption properties and concentrations of chromophoric impurities, the presence of other species in the same phase or air above it, or the location of impurities within ice or snowpack. This lecture deals with some aspects of experimental spectroscopy and photochemistry of organic contaminants of ice and emphasizes the specific aspects of their photoreactions.

Photoactivatable (alternatively, photoremovable, photoreleasable, or photocleavable) protecting groups (PPGs), also known as caged or photocaged compounds, are used to enable non-invasive spatiotemporal photochemical control over the release of species of interest. Recent years have seen the development of PPGs activatable by biologically and chemically benign visible and near-infrared (NIR) light. These long-wavelength-absorbing moieties expand the applicability of this powerful method and its accessibility to non-specialist users. This review comprehensively covers organic and transition metal-containing photoactivatable compounds (complexes) that absorb in the visible- and NIR-range to release various leaving groups and gasotransmitters (carbon monoxide, nitric oxide, and hydrogen sulfide). The text also covers visible- and NIR-light-induced photosensitized release using molecular sensitizers, quantum dots, and upconversion and second-harmonic nanoparticles, as well as release via photodynamic (photooxygenation by singlet oxygen) and photothermal effects. Release from photo-activatable polymers, micelles, vesicles, and photoswitches, along with the related emerging field of photopharmacology, is discussed at the end of the review.

Although phototherapy (PT) is a standard treatment for neonatal jaundice, no validated clinical methods for determination of bilirubin phototherapy products are available. Thus, the aim of our study was to establish a such method for clinical use. To achieve this aim, a LC-MS/MS assay for simultaneous determination of Z-lumirubin (LR) and unconjugated bilirubin (UCB) was conducted. LR was purified after irradiation of UCB at 460 nm. The assay was tested on human sera from PT-treated neonates. Samples were separated on a HPLC system with a triple quadrupole mass spectrometer detector. The instrument response was linear up to 5.8 and 23.4 mg/dL for LR and UCB, respectively, with submicromolar limits of detection and validity parameters relevant for use in clinical medicine. Exposure of newborns to PT raised serum LR concentrations three-fold (p vs. 10.3 ± 3.3 mg/dL, p

We designed and studied the structure, dynamics, and photochemistry of photoswitchable reverse micelles (RMs) composed of azobenzene-containing ammonium amphiphile 1 and water in chloroform at room and subzero temperatures by NMR spectroscopy and molecular dynamics simulations. The NMR and diffusion coefficient analyses showed that micelles containing either the E or Z configuration of 1 are stable at room temperature. Depending on the water-to-surfactant molar ratio, the size of the RMs remains unchanged or is slightly reduced because of the partial loss of water from the micellar cores upon extensive E → Z or Z → E photoisomerization of the azobenzene group in 1. Upon freezing at 253 or 233 K, E-1 RMs partially precipitate from the solution but are redissolved upon warming whereas Z-1 RMs remain fully dissolved at all temperatures. Light-induced isomerization of 1 at low temperatures does not lead to the disintegration of RMs remaining in the solution; however, its scope is influenced by a precipitation process. To obtain a deeper molecular view of RMs, their structure was characterized by MD simulations. It is shown that RMs allow for amphiphile isomerization without causing any immediate significant structural changes in the micelles.

Photochemical generation of dibenzosilacyclohept-4-yne 3 from the corresponding cyclopropenone 1 and its copper-free click reactions are reported. Steady-state irradiation, kinetic, and transient absorption spectroscopy studies revealed that strained alkyne 3 is rapidly (