Photochemistry of chrysene adsorbedon several types of particle

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Synthesis and photochemistry of novel bromo substituted stilbene derivatives as triplet state sensitizers for the generation of singlet oxygen

We have presented the synthesis and characterization of three new bromo substituted stilbene derivatives, p-3,4,5-trimethoxy-p′- 2,3,4,5,6-pentabromostilbene （C1）, p-N,N-dimethylamino-p′-2,3,4,5,6-pentabromostilbene （C2） and p-N,N-diphenylamino-p′- 2,3,4,5,6-pentabromostilbene （C3） in this letter. The UV/vis absorption and photoluminescence were investigated in various solvents. The maximal absorption wavelength of C1 exhibited blue-shift to those of C2 and C3 in different solvents. No florescence emission could be detected for these compounds at room temperature. Singlet oxygen could be efficiently produced with these sensitizers under near-ultraviolet and visible light irradiation.

Synthesis and Photochemistry of Diphenylchlorin and Diphenylbacteriochlorin

Diphenylchlorin (DPC) and diphenylbacteriochlorin (DPBC) were synthesized for the first time from reduction of 5,10-diphenylporphyrin (DPP). As photosensitizers they have sizable absorption in the red region of the visible spectrum. The high yield of DPC.-photosensitized generation Of O-1(2), and the EPR studies in homogenerous solution showed that the photodynamic action of DPP-based photosensitizers may proceed via type I and type II machanisms.

Impact of surface Albedo on Martian photochemistry

Solar energy is the primary driving force behind a planet’s climate system,and surface albedo plays a key role in determining the energy budget of the planet.Coupling the Snow,Ice,and Aerosol Radiation(SNICAR)with the Laboratoire de Météorologie Dynamique(LMD)Mars General Circulation Model(MGCM)to create a new coupled model leads to an approximately 4%drop in the net CO2 ice deposition on Mars.Newly simulated surface albedo affects the concentration of gaseous species in the Martian atmosphere(condensation-sublimation cycle).The new set-up also impacts the solar energy available in the atmosphere.These two effects together lead to subsequent and significant changes in other chemical species in the Martian atmosphere.Compared with results of the MGCM model alone,in the new coupled model CO2(gas)and O3 show a drop of about 1.17%and 8.59%in their respective concentrations,while H2O(vapor)and CO show an increase of about 13.63%and 0.56%in their respective concentrations.Among trace species,OH shows a maximum increase of about 29.44%,while the maximum drop of 11.5%is observed in the O concentration.Photochemically neutral species such as Ar and N2 remain unaffected by the albedo changes.

Photochemistry of Styrene Oxide: A Triplet Pathway in the Singlet Excitation of a Monoaryl Oxirane

Direct photolysis and quenching experiments with styrene oxide support the existence of an efficient triplet photochemical pathway to benzyl radical formation. Similar photolytic behavior for styrene glycol carbonate strongly supports the 1,3-diradical, resulting from the scission of the benzylic C-O bond, as the geometric source of the triplet pathway. Primary photoproducts were determined by both NMR and HPLC analysis and we observed that toluene and bibenzyl were both primary photoproducts, not secondary photoproducts.

Photoinduced transposed Paternò-Büchi reaction for effective synthesis of high-performance jet fuel

High-energy-density fuels are important for volume-limited aerospace vehicles,but the increase in fuel energy density always leads to poor cryogenic performance.Herein,we investigated the transposed Paternò-Büchi reaction of biomass cyclic ketone and cyclic alkene to synthesize a new kind of alkyl-substituted polycyclic hydrocarbon fuel with high energy density and good cryogenic performance.The triplet-energy-quenching results and phosphorescent emission spectra reveal the sensitization mechanism of the reaction,including photosensitizer excitation,triplettriplet energy transfer,cyclization,and relaxation,and the possible reaction path was revealed by the density functional theory(DFT)calculations.The reaction conditions of photosensitizer type and addition,molar ratio of substrates,reaction temperature,and incident light intensity were optimized,with the target product yield achieving 65.5%.Moreover,the reaction dynamics of the reaction rate versus the light intensity are established.After the hydrogenation-deoxygenation reaction,three fuels with a high density of 0.864-0.938 g·ml^(-1) and a low freezing point of<-55℃ are obtained.This work provides a benign and effective approach to synthesize high-performance fuels.

Interactive Effects of Drought Stresses and Elevated CO_2 Concentration on Photochemistry Efficiency of Cucumber Seedlings

To reveal and quantify the interactive effects of drought stresses and elevated CO2 concentration [CO2] on photochemistry efficiency of cucumber seedlings, the portable chlorophyll meter was used to measure the chlorophyll content, and the Imaging-PAM was used to image the chlorophyll fluorescence parameters and rapid light response curves （RLC） of leaves in two adjacent greenhouses. The results showed that chlorophyll content of leaves was reduced significantly with drought stress aggravated. Minimal fluorescence （Fo） was increased while maximal quantum yield of PSII （Fv/Fm） decreased significantly by severe drought stress. The significant decrease of effective quantum yield of PSII （Y（Ⅱ）） accompanied by the significant increase of quantum yield of regulated energy dissipation （Y（NPQ）） was observed under severe drought stress condition, but there was no change of quantum yield of nonregulated energy dissipation （Y（NO））. We detected that the coefficient of photochemical quenching （qP） decreased, and non-photochemical quenching （NPQ） increased significantly under severe drought stress. Furthermore, we found that maximum apparent electron transport rate （ETRmax） and saturating photosynthetically active radiation （PPFDsat） decreased significantly with drought stress aggravated. However, elevated [CO2] significantly increased FvlFm, qP and PPFDsat, and decreased NPQ under all water conditions, although there were no significant effects on chlorophyll content, Fo, Y（Ⅱ）, Y（NPQ）, Y（NO） and ETRmax. Therefore, it is concluded that CO2-fertilized greenhouses or elevated atmospheric [CO2] in the future could be favorable for cucumber growth and development, and beneficial to alleviate the negative effects of drought stresses to a certain extent.

The gravity wave instability induced by photochemistry in summer polar mesopause region

The effect of diabatic process due to the photochemical heating and cooling on the gravity wave propagation in middle atmosphere is studied. A linear gravity wave model which considers the diabatic process is established. The unstable region and the growth rate of the gravity wave caused by photochemistry are calculated. And the comparison between the model and the adiabatic gravity wave theory of pure dynamics is made. The results indicate that the photochemical heating process can induce the instability of gravity wave at mesopause. The intensity of the instability becomes stronger as the temperature decreases. The temperature feature and the altitude characteristics of the instability are consistent with the observation. Therefore, the instability of the gravity wave induced by photochemistry may be an important mechanism in polar mesopause region in summer.

Photophysics,photochemistry and photobiology of hypocrel-lin photosensitizers

Hypocrellins are novel photosensitizers from China, which are demonstrated to have significant anti-tumor and anti-virus activity and to be potential photo-dynamic therapy (PDT) agents. As compared with hemato-porphyrin, the only approved photosensitizer, hypocrellins have several advantages, such as easy preparation and easy purification, high triplet quantum yield, high singlet-oxygen quantum yield, high phototoxicity but low dark toxicity, and rapid clearance from normal issues. This article reviews briefly the photophysics, photochemistry and photobiology of hypocrellins on the basis of the domestic and international research results.

Continuous-flow photochemistry: An expanding horizon of sustainable technology

Understanding the unique characteristics of continuous-flow photochemistry will lead to a paradigm shift in the way we enhance sustainability and wellbeing.In this mini-review,we first provide a succinct overview of working principles of this technique and discuss several recent synthetic protocols.Then,emphasis is given to those representative examples which address environmental issues such as indoor air pollutants and water contamination.Finally,recent progress made using this technique to deal with rising CO2 emission,solar energy utilization and biomedical equipment is described.It is believed that this mini-review could inspire more chemists to utilize this technique in their research,either in the academic or industrial field.

Atmospheric photochemistry and secondary aerosol formation of urban air in Lyon,France

Photochemical aging of volatile organic compounds(VOCs)in the atmosphere is an important source of secondary organic aerosol(SOA).To evaluate the formation potential of SOA at an urban site in Lyon(France),an outdoor experiment using a Potential Aerosol Mass(PAM)oxidation flow reactor(OFR)was conducted throughout entire days during JanuaryFebruary 2017.Diurnal variation of SOA formations and their correlation with OH radical exposure(OHexp),ambient pollutants(VOCs and particulate matters,PM),Relative Humidity(RH),and temperature were explored in this study.Ambient urban air was exposed to high concentration of OH radicals with OHexp in range of(0.2-1.2)×10^12 molecule/(cm^3·sec),corresponding to several days to weeks of equivalent atmospheric photochemical aging.The results informed that urban air at Lyon has high potency to contribute to SOA,and these SOA productions were favored from OH radical photochemical oxidation rather than via ozonolysis.Maximum SOA formation(36μg/m^3)was obtained at OHexp of about 7.4×10^11 molecule/(cm^3·sec),equivalent to approximately 5 days of atmospheric oxidation.The correlation between SOA formation and ambient environment conditions(RH&temperature,VOCs and PM)was observed.It was the first time to estimate SOA formation potential from ambient air over a long period in urban environment of Lyon.

Interplay of Supramolecular Chemistry and Photochemistry with Palladium-Catalyzed Ethylene Polymerization

Metal–metal cooperativity effects have been extensively explored in olefin polymerization,along with the design and preparation of many binuclear transition metal catalysts.However,their synthesis and the tuning of metal–metal distance are complicated and time-consuming.In this contribution,a supramolecular chemistry strategy was used to construct multinuclear olefin polymerization catalysts.Urea functional groups were installed into severalα-diimine palladium catalysts to enable hydrogenbonding-induced self-assembly.

Recent progress in supramolecular chiral photochemistry

Chiral photochemistry appears to be a highly challenging topic and still very much in its infancy, especially if comparing to its well-developed thermochemical counterpart.Significant efforts have been devoted in order to improve stereoselectivity of chiral photoreactions,among which,the supramolecular strategy proven the most promising.The present review,motivated by the rapid progress in the supramolecular chiral photochemistry,concentrates on advancements achieved mainly in the last decade.The features and advantages of supramolecular chiral photochemistry are exemplified by representative photoreactions in terms of the chiral hosts/assemblies.

Nickel-Catalyzed Reductive Cross-Couplings:New Opportunities for Carbon-Carbon Bond Formations through Photochemistry and Electrochemistry

Metal-catalyzed cross-electrophile couplings have become a valuable tool for carbon-carbon bond formation.This minireview provides a comprehensive overview of the recent developments in the topical field of cross-electrophile couplings,provides explanations of the current state-of-the-art,and highlights new opportunities arising in the emerging fields of photoredox catalysis and electrochemistry.

Photo-regulation of 2D supramolecular self-assembly：On-surface photochemistry studied by STM

During the past few years,regulation and controlling of the two-dimension（2D） self-assembled supramolecular structure on surface have drawn increasing attention in nanoscience and technology.External stimuli have been widely used to regulate these 2D nanostructures.Among various external stimuli approaches,photo-regulation as one of the most outstanding means of regulation has been extensively studied because different wave bands can lead to molecular conformation variation and new bonds to gain new molecules.In this review,the photo-regulated self-assembled structure on solid surface as well as the photo-reactions of different molecules substituted with photo-sensitive groups are introduced to give us an insight into on-surface photochemistry,which plays an important role on the nano-devices fabrication.Notably,these photo-sensitive behaviors as well as the formed structures on surface were probed at sub-molecule level by unique scanning tunneling microscopy（STM） technique.

Photochemistry of phenothiazine in benzene and cyclohexane

IN the last few years phenothiazine(PTH)and its derivatives have captured much attention inthe fields of medicines,biology,and microelectronic materials due to their ability to ef-ficiently photosensitize acid production in the presence of vicinal dibromides and hence tochange the solubilization of polymer films.The photophysical and photochemical properties re-lated to the processes have been studied.Monica Barra et al.found that the triplet

CIDNP study of the photochemistry of 1-acetylindole-2,3-dione

Chemically Induced Dynamic Nuclear Polarization (CIDNP) technique is applied to study the photochemical reactions of 1-acetylindole-2,3-dione (AID) with several hydrogen do- nors (1—13). These reactions take place by direct hydrogen abstraction of triplet excited AID from the corresponding 1—13 to give neutral radical pair intermediates, which afford polarized starting materials by back hydrogen transfer and give polarized coupling products by radical pair recombination.