Synthesis and Characterization of Side-Chain Liquid-Crystalline Block Copolymers Containing Cyano-Terminated Phenyl Benzoate Moieties.

Block copolymers, known for their capacity to undergo microphase separation, spontaneously yield various periodic nanostructures. These precisely controlled nanostructures have attracted considerable interest due to their potential applications in microfabrication templates, conducting films, filter membranes, and other areas. However, it is crucial to acknowledge that microphase-separated structures typically exhibit random alignment, making alignment control a pivotal factor in functional material development. To address this challenge, researchers have explored the use of block copolymers containing liquid-crystalline (LC) polymers, which offer a promising technique for alignment control. The molecular structure and LC behavior of these polymers significantly impact the morphology and alignment of microphase-separated structures. In this study, we synthesized LC diblock copolymers with cyano-terminated phenyl benzoate moieties and evaluated the microphase-separated structures and molecular alignment behaviors. The LC diblock copolymers with a narrow molecular weight distribution were synthesized by atom transfer radical polymerization. Small angle X-ray scattering measurements revealed that the block copolymers exhibit smectic LC phases and form cylinder structures with a lattice period of about 18 nm by microphase separation. The examination of block copolymer films using polarized optical microscopy and polarized UV-visible absorption spectroscopy corroborated that the LC moieties were uniaxially aligned along the alignment treatment direction.

Enhanced Electrocatalytic CO2 Reduction Reactivity of S- and N-Doped Fe-Embedded Graphene.

In this work, we studied the reaction mechanisms for CO2 reduction reaction (CRR) on the iron-doped graphene and its coordinating sulfur (S) and nitrogen (N) variants, FeNn S4-n (n=1-4), using density functional theory calculations. Our results revealed that the electronic property and catalytic reactivity of the surfaces can be tuned by varying the N and S atoms ratio. The CRR activities of the mixed surfaces, FeN3 S1 , FeN2 S2 , and FeN1 S3 , were better than FeN4 and FeS4 , where the absolute value of the limiting potential of the mixed surface decreased by 0.3 V. Considering the stability, we suggest FeN3 S surface to be favorable for CRR. For the bare surfaces, we found a positive linear correlation between the magnetic moment and the charge of Fe metal. For these surfaces, the reduction of CO (*CO+(H+ +e- )→*CHO) was important in deciding the limiting potential. We found that the adsorption energy of CO displayed a volcano relationship with the magnetic moment of the Fe atom. The study showed that the change of local coordinating structure around the Fe atom could modify the electronic and magnetic properties of the active Fe center and improve the CRR activity performance.

Kinetics of the Simplest Criegee Intermediate Reaction with Water Vapor: Revisit and Isotope Effect.

The kinetics of the simplest Criegee intermediate (CH2OO) reaction with water vapor was revisited. By improving the signal-to-noise ratio and the precision of water concentration, we found that the kinetics of CH2OO involves not only two water molecules but also one and three water molecules. Our experimental results suggest that the decay of CH2OO can be described as d[CH2OO]/dt = -kobs[CH2OO]; kobs = k0 + k1[water] + k2[water]2 + k3[water]3; k1 = (4.22 ± 0.48) × 10-16 cm3 s-1, k2 = (10.66 ± 0.83) × 10-33 cm6 s-1, k3 = (1.48 ± 0.17) × 10-50 cm9 s-1 at 298 K and 300 Torr with the respective Arrhenius activation energies of Ea1 = 1.8 ± 1.1 kcal mol-1, Ea2 = -11.1 ± 2.1 kcal mol-1, Ea3 = -17.4 ± 3.9 kcal mol-1. The contribution of the k3[water]3 term becomes less significant at higher temperatures around 345 K, but it is not ignorable at 298 K and lower temperatures. By quantifying the concentrations of H2O and D2O with a Coriolis-type direct mass flow sensor, the kinetic isotope effect (KIE) was investigated at 298 K and 300 Torr and KIE(k1) = k1(H2O)/k1(D2O) = 1.30 ± 0.32; similarly, KIE(k2) = 2.25 ± 0.44 and KIE(k3) = 0.99 ± 0.13. These mild KIE values are consistent with theoretical calculations based on the variational transition state theory, confirming that the title reaction has a broad and low barrier, and the reaction coordinate involves not only the motion of a hydrogen atom but also that of an oxygen atom. Comparing the results recorded under 300 Torr (N2 buffer gas) with those under 600 Torr, a weak pressure effect of k3 was found. From quantum chemistry calculations, we found that the CH2OO + 3H2O reaction is dominated by the reaction pathways involving a ring structure consisting of two water molecules, which facilitate the hydrogen atom transfer, while the third water molecule is hydrogen-bonded outside the ring. Furthermore, analysis based on dipole capture rates showed that the CH2OO(H2O) + (H2O)2 and CH2OO(H2O)2 + H2O pathways will dominate in the three water reaction.

Substituent Dependence on the Reactions of Criegee Intermediates with Carbon Dioxide and Carbon Monoxide.

Criegee intermediates (CIs), R1 R2 COO, are active molecules produced in the atmosphere from the ozonolysis of alkenes. Here, we systematically evaluated the reactivity of ten CIs with carbon monoxide and carbon dioxide using CCSD(T)-F12/cc-pVTZ-F12//B3LYP/6-311+G(2d,2p) energies and transition state theory. Many previous studies focused on alkyl substitution, but here we evaluated both alkyl and vinyl substitution toward the reactivity by studying five anti-type CIs: CH2 OO, anti-CH3 CHOO, anti-cis-C2 H5 CHOO, anti-trans-MACRO, anti-cis-MACRO; and five syn-type CIs: syn-CH3 CHOO, (CH3 )2 COO, syn-trans-C2 H5 CHOO, syn-trans-MVKO, and syn-cis-MVKO. Our study showed that reactions involving CO2 have a large substituent dependence varying nearly five orders of magnitude, while those involving CO have a much smaller two orders of magnitude difference. Analysis based on the strain interaction model showed that deformation of the CI is an important feature in determining the reactivity with CO2 . On the other hand, we used the OO and CO bond ratios to analyze the zwitterionic character of the CIs. We found that vinyl substitution with π-conjugation results in smaller zwitterionic character and lower reactivity with CO. Lastly, the reactivity of CIs with CO as well as CO2 were found to be not fast enough to be important in an atmospheric context.

Reconfigurable Logic-in-Memory Constructed Using an Organic Antiambipolar Transistor.

We demonstrate an electrically reconfigurable two-input logic-in-memory (LIM) using a dual-gate-type organic antiambipolar transistor (DG-OAAT). The attractive feature of this device is that a phthalocyanine-cored star-shaped polystyrene is used as a nano-floating gate, which enables the electrical switching of individual logic circuits and stores the circuit information by the nonvolatile memory effect. First, the DG-OAAT exhibited Λ-shaped transfer curves with hysteresis by sweeping the bottom-gate voltage. Programming and erasing operations enabled the reversible shift of the Λ-shaped transfer curves. Furthermore, the top-gate voltage effectively tuned the peak voltages of the transfer curves. Consequently, the combination of dual-gate and memory effects achieved electrically reconfigurable two-input LIM operations. Individual logic circuits (e.g., OR/NAND, XOR/NOR, and AND/XOR) were reconfigured by the corresponding programming and erasing operations without any variations in the input signals. Our device concept has the potential to fulfill an epoch-making organic integration circuit with a simple device configuration.

Sex Difference in the Impact of Dual Antiplatelet Therapy using Cilostazol for Secondary Stroke Prevention: A Sub-Analysis of CSPS.com.

AIM: Although some sex differences in stroke have been reported, differences in the effects of antiplatelet therapy for secondary stroke prevention have not been clarified. METHODS: In the Cilostazol Stroke Prevention Study combination trial, patients with high-risk, non-cardioembolic ischemic stroke between 8 and 180 days after onset treated with aspirin or clopidogrel alone were recruited and randomly assigned to receive either monotherapy or dual antiplatelet therapy (DAPT) using cilostazol and followed up for 0.5-3.5 years. The primary efficacy outcome was recurrence of ischemic stroke. The safety outcome was severe or life-threatening hemorrhage. Outcomes were analyzed by sex. RESULTS: A total of 1,320 male patients and 558 female patients were included. The male patients had more risk factors than the female patients. In male patients, the primary endpoint occurred at a rate of 2.0 per 100 patient-years in the DAPT group and 5.1 per 100 patient-years in the monotherapy group (hazard ratio (HR), 0.40; 95% confidence interval (CI), 0.23-0.68). In male patients, DAPT prolonged the time to recurrent stroke by 4.02-fold (95% CI, 1.63-9.96) compared with monotherapy. In female patients, the average annual event rates were 2.7 per 100 patient-years in the DAPT group and 3.3 per 100 patient-years in the monotherapy group (HR, 0.82; 95% CI, 0.37-1.84). Safety outcomes did not differ significantly in both male and female patients. CONCLUSIONS: Long-term DAPT using cilostazol reduced the recurrence of ischemic stroke and prolonged the recurrence-free time in male patients, but not in female patients.

Sequential therapy with once-weekly teriparatide injection followed by alendronate versus monotherapy with alendronate alone in patients at high risk of osteoporotic fracture: final results of the Japanese Osteoporosis Intervention Trial-05.

In this randomized, controlled trial, sequential therapy with once-weekly subcutaneous injection of teriparatide for 72 weeks, followed by alendronate for 48 weeks resulted in a significantly lower incidence of morphometric vertebral fracture than monotherapy with alendronate for 120 weeks in women with osteoporosis at high risk of fracture. PURPOSE: To determine whether the anti-fracture efficacy of sequential therapy with teriparatide, followed by alendronate is superior to that of monotherapy with alendronate, a prospective, randomized, open-label, blinded-endpoint trial was performed. METHODS: Japanese women aged at least 75 years were eligible for the study, if they had primary osteoporosis and if they were at high risk of fracture. Patients were randomly assigned (1:1) to receive the sequential therapy (once-weekly subcutaneous injection of teriparatide 56.5 µg for 72 weeks, followed by alendronate for 48 weeks) or monotherapy with alendronate for 120 weeks. The primary endpoint in the final analysis was the incidence of morphometric vertebral fracture during the 120-week follow-up period. RESULTS: Between October 2014 and June 2020, 505 patients in the sequential therapy group and 506 in the monotherapy group were enrolled. Of these, 489 and 496, respectively, were included in the main analysis. The incidence of morphometric vertebral fracture during the 120-week follow-up period in the sequential therapy group (64 per 627.5 person-years, annual incidence rate 0.1020) was significantly lower than that in the monotherapy group (126 per 844.2 person-years, annual incidence rate 0.1492), with a rate ratio of 0.69 (95% confidence interval 0.54 to 0.88, P < 0.01). After 72 weeks, no patient had a severe adverse event that was considered related to the study drug. CONCLUSION: Once-weekly injection of teriparatide, followed by alendronate resulted in a significantly lower incidence of morphometric vertebral fracture than alendronate monotherapy in women with osteoporosis who were at high risk of fracture. TRIAL REGISTRATION NUMBER, DATE OF REGISTRATION: jRCTs031180235 and UMIN000015573, March 12, 2019.

Association of Urinary Pentosidine Levels With the Risk of Fractures in Patients With Severe Osteoporosis: The Japanese Osteoporosis Intervention Trial-05 (JOINT-05).

Associations between urinary pentosidine, one of the advanced glycation end products in collagen, and the risk of fracture in patients with severe osteoporosis are unknown. In this study, we investigated whether the urinary pentosidine level is associated with the incidence of morphometric vertebral fracture and nonvertebral fracture using data of a randomized, controlled trial, JOINT-05. JOINT-05 enrolled Japanese women aged 75 years or older with primary osteoporosis. Patients were randomly assigned (1:1) to receive sequential therapy (teriparatide followed by alendronate) or monotherapy with alendronate for 120 weeks. Incidences of vertebral and nonvertebral fractures were assessed morphologically. During treatment, urinary levels of pentosidine and serum levels of bone turnover markers (osteocalcin, procollagen type I amino-terminal propeptide, and tartrate-resistant acid phosphatase 5b) were measured. A total of 967 patients with baseline pentosidine levels were included in the study. Of these, 137 had vertebral fractures, and 42 had nonvertebral fractures. The rate ratios for vertebral fracture for the second (30-39 pmol/mL), third (40-49 pmol/mL), and fourth quartile (≥50 pmol/mL) groups divided by pentosidine level compared with the first quartile (<30 pmol/mL) group were 1.65 (95% confidence interval [CI] 0.99-2.75, p = 0.06), 1.51 (95% CI 0.87-2.61, p = 0.14), and 1.69 (95% CI 1.01-2.83, p = 0.05), respectively. The corresponding rate ratios for nonvertebral fracture were 3.07 (95% CI 0.88-10.70, p = 0.08), 2.34 (95% CI 0.61-8.95, p = 0.22), and 3.95 (95% CI 1.14-13.67, p = 0.03), respectively. The association of the urinary pentosidine level with the incidence of nonvertebral fracture was the strongest among the biomarkers assessed in the study. In conclusion, the urinary pentosidine level was associated with the risk of fracture in patients with severe osteoporosis receiving teriparatide or alendronate. © 2022 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.

Reaction Kinetics of Criegee Intermediates with Nitric Acid.

This work investigated the reaction kinetics of HNO3 with four Criegee intermediates (CIs): CH2OO, (CH3)2COO, methyl vinyl ketone oxide (MVKO), and methacrolein oxide (MACRO). Our results show that these reactions are extremely fast with rate coefficients of (1.51 ± 0.45) × 10-10, (3.54 ± 1.06) × 10-10, (3.93 ± 1.18) × 10-10, and (3.0 ± 1.0) × 10-10 cm3 s-1 for reactions of HNO3 with CH2OO, (CH3)2COO, syn-MVKO, and anti-MACRO, respectively. This is consistent with previous results for the reactions between CIs and carboxylic acids, but the rate coefficient of CH2OO + HNO3 in the literature [Foreman Angew. Chem. 2016, 128, 10575] was found to be overestimated by a factor of 3.6. In addition, we did not observe any significant pressure dependence in the HNO3 reactions with CH2OO and (CH3)2COO under 100-400 Torr. Our results indicate that in a dry area with severe NOx pollution, the reactions of CIs with HNO3 and their products may be worthy of attention, but these reactions may be insignificant under high-humidity conditions. However, CI reactions with HNO3 may not play an important role in the atmospheric removal processes of HNO3 because of the low concentrations of CIs.

Wave Packet Calculation of Absolute UV Cross Section of Criegee Intermediates.

Criegee intermediates, R1R2COO, are reactive species formed in the atmosphere through the ozonolysis of alkenes. They have an intense ultraviolet (UV) adsorption between 300 to 400 nm. However, experimentally determining the absolute cross sections is not easy. We used wave packet propagation on an one-dimensional adiabatic potential energy curve (PEC) along the OO bond to simulate the UV spectra for various Criegee intermediates. Our results showed a very fast, ∼20 fs, decay out of the Franck-Condon region. This gives justification for using the semiclassical approach which was utilized in previous studies. From the comparison of various quantum chemistry methods, we found that multireference methods can give spectra with a width and cross section reproducing the experimental results, while single reference methods tend to give narrower skewed peaks with a larger cross section. From the test using wave packet propagation on various approximated PECs and transition moment functions, we show that the Gaussian approximation within the reflection method is valid. In addition, we found that we can obtain peak positions that reproduce the experimental results by shifting those obtained by MRCI+Q, CASSCF, EOMCCSD, and TDCAMB3LYP by -0.2, -1.0, -0.3, and -0.5 eV, respectively. The Gaussian approximation using peak position, oscillator strength, and peak width from MRCI+Q is a cost-effective way to simulate the UV spectra of Crigee intermediates for which experimental determination may be hard.

Mechanism and kinetics of the reaction of the Criegee intermediate CH2OO with acetic acid studied using a step-scan Fourier-transform IR spectrometer.

Acetic acid, CH3C(O)OH, plays an important role in the acidity of the troposphere. The reactions of Criegee intermediates with CH3C(O)OH have been proposed to be a potential source of secondary organic aerosol in the atmosphere. We investigated the detailed mechanism and kinetics of the reaction of the Criegee intermediate CH2OO with CH3C(O)OH. The time-resolved infrared absorption spectra of transient species produced upon irradiation at 308 nm of a flowing mixture of CH2I2/O2/CH3C(O)OH at 298 K were recorded using a step-scan Fourier-transform infrared spectrometer. The decrease in the intensity of the bands of CH2OO was accompanied by the appearance of bands near 886, 971, 1021, 1078, 1160, 1225, 1377, 1402, 1434, and 1777 cm-1, assigned to the absorption of hydroperoxymethyl acetate [CH3C(O)OCH2OOH, HPMA], the hydrogen-transferred adduct of CH2OO and CH3C(O)OH. Two types of conformers of HPMA, an open form and an intramolecularly hydrogen-bonded form, were identified. At a later reaction period, bands of the open-form HPMA became diminished, and new bands appeared at 930, 1045, 1200, 1378, 1792, and 1810 cm-1, assigned to formic acetic anhydride [CH3C(O)OC(O)H, FAA], a dehydrated product of HPMA. The intramolecularly hydrogen-bonded HPMA is more stable. From the temporal profiles of HPMA and FAA, we derived a rate coefficient k = (1.3 ± 0.3) × 10-10 cm3 molecule-1 s-1 for the reaction CH2OO + CH3C(O)OH to form HPMA and a rate coefficient k = 980 ± 40 s-1 for the dehydration of the open-form HPMA to form FAA. Theoretical calculations were performed to elucidate the CH2OO + CH3C(O)OH reaction pathway and to understand the distinct reactivity of these two forms of HPMA.

Understanding the interaction between transition metal doping and ligand atoms of ZnS and ZnO monolayers to promote the CO2 reduction reaction.

Single-atom catalysts (SACs) obtained by doping transition metal (TM) atoms into stable monolayers are a promising way to improve the CO2 reduction reaction (CRR) performance. In this work, we theoretically investigated the effect of ligand atoms around the doped TM (TM = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu) in ZnO and ZnS for promoting the CRR performance. We found that the ligand atoms around the TM can influence its oxidation state and the electronic properties of the SACs, thus affecting their CRR activity. Due to the smaller charge transfer between the TM and substrate for TM-ZnS compared to TM-ZnO, the TM binding is weaker for the former. In addition, the more negatively charged oxygen ligand atoms in TM-ZnO interact with reaction intermediates, resulting in CRR products with less electron transfer. Pristine ZnS and ZnO monolayers can produce HCOOH but require a high limiting potential (UL) of about -1.2 V. Doping with TMs can reduce UL compared to the pristine surface. At the same time, the ligand can alter the preferred CRR pathway and product selectivity. We found that Mn-ZnS is selective to the CH4 product with a UL of only -0.29 V, which is a nearly 1 V improvement in the UL compared to ZnS.

Absolute photodissociation cross sections of thermalized methyl vinyl ketone oxide and methacrolein oxide.

Methyl vinyl ketone oxide (MVKO) and methacrolein oxide (MACRO) are resonance-stabilized Criegee intermediates which are formed in the ozonolysis reaction of isoprene, the most abundant unsaturated hydrocarbon in the atmosphere. The absolute photodissociation cross sections of MVKO and MACRO were determined by measuring their laser depletion fraction at 352 nm, which was deduced from their time-resolved UV-visible absorption spectra. After calibrating the 352 nm laser fluence with the photodissociation of NO2, for which the absorption cross section and photodissociation quantum yield are well known, the photodissociation cross sections of thermalized (299 K) MVKO and MACRO at 352 nm were determined to be (3.02 ± 0.60) × 10-17 cm2 and (1.53 ± 0.29) × 10-17 cm2, respectively. Using their reported spectra and photodissociation quantum yields, their peak absorption cross sections were deduced to be (3.70 ± 0.74) × 10-17 cm2 (at 371 nm, MVKO) and (3.04 ± 0.58) × 10-17 cm2 (at 397 nm, MACRO). These values agree fairly with our theoretical predictions and are substantially larger than those of smaller, alkyl-substituted Criegee intermediates (CH2OO, syn-CH3CHOO, (CH3)2COO), revealing the effect of extended conjugation. With their cross sections, we also quantified the synthesis yields of MVKO and MACRO in the present experiment to be 0.22 ± 0.10 (at 299 K and 30-700 torr) and 0.043 ± 0.019 (at 299 K and 500 torr), respectively, relative to their photolyzed precursors. The lower yield of MACRO can be related to the high endothermicity of its formation channel.

Molecular dynamics simulations of sulfone derivatives in complex with DNA topoisomerase IIα ATPase domain.

Human topoisomerase II alpha (TopoIIα) is a crucial enzyme involved in maintaining genomic integrity during the process of DNA replication and mitotic division. It is a vital therapeutic target for designing novel anticancer agents in targeted cancer therapy. Sulfones, members of organosulfur compounds, have been reported to possess various biological activities such as antimicrobial, anti-inflammatory, anti-HIV, anticancer, and antimalarial properties. In the present study, a series of sulfones was selected to evaluate their inhibitory activity against TopoIIα using computational approaches. Molecular docking results revealed that several sulfone analogs bind efficiently to the ATPase domain of TopoIIα. Among them, sulfones 18a, 60a, *4 b, *8 b, *3c, and 8c exhibit higher binding affinity than the known TopoII inhibitor, salvicine. Molecular dynamics simulations and free energy calculations based on MM/PB(GB)SA method demonstrated that sulfone *8 b strongly interacts with amino acid residues in the ATP-binding pocket (E87, N91, D94, I125, I141, F142, S149, G161, and A167), driven mainly by an electrostatic attraction and a strong H-bond formation at G161 residue. Altogether, the obtained results predicted that sulfones could have a high potential to be a lead molecule for targeting TopoIIα.Communicated by Ramaswamy H. Sarma.

Experimental and Computational Studies of Criegee Intermediate syn-CH3CHOO Reaction with Hydrogen Chloride.

Hydrogen chloride (HCl) contributes substantially to the atmospheric Cl; both species could affect the composition of Earth's atmosphere and the fate of pollutants. Here, we present the kinetics study for syn-CH3CHOO reaction with HCl using experimental measurement and theoretical calculations. The experiment was conducted in a flow tube reactor at a pressure of 10 Torr and temperatures ranging from 283 to 318 K by using the OH laser-induced fluorescence (LIF) method. Transition-state theory and quantum chemistry calculations with QCISD(T) were used to calculate the rate coefficients. Weak negative temperature dependence was observed with a measured activation energy of -(2.98 ± 0.12) kcal mol-1 and a calculated zero-point-corrected barrier energy of -3.29 kcal mol-1. At 298 K, the rate coefficient was measured to be (4.77 ± 0.95) × 10-11 cm3 s-1, which was in reasonable agreement with 2.2 × 10-11 cm3 s-1 from the theoretical calculation.

Substituent Effect in the Reactions between Criegee Intermediates and 3-Aminopropanol.

Via intramolecular H atom transfer, 3-aminopropanol is more reactive toward Criegee intermediates, in comparison with amines or alcohols. Here we accessed the substituent effect of Criegee intermediates in their reactions with 3-aminopropanol. Through real-time monitoring the concentrations of two Criegee intermediates with their strong UV absorption at 340 nm, the experimental rate coefficients at 298 K (100-300 Torr) were determined to be (1.52 ± 0.08) × 10-11 and (1.44 ± 0.22) × 10-13 cm3 s-1 for the reactions of 3-aminopropanol with (CH3)2COO (acetone oxide) and CH2CHC(CH3)OO (methyl vinyl ketone oxide), respectively. Compared to our previous experimental value for the reaction with syn-CH3CHOO, (1.24 ± 0.13) × 10-11 cm3 s-1, we can see that the methyl substitution at the anti position has little effect on the reactivity while the vinyl substitution causes a drastic decrease in the reactivity. Our theoretical calculations based on CCSD(T)-F12 energies reproduce this 2-order-of-magnitude decrease in the rate coefficient caused by the vinyl substitution. Using the activation strain model, we found that the interaction of Criegee intermediates with 3-aminopropanol is weaker for the case of vinyl substitution. This effect can be further rationalized by the delocalization of the lowest unoccupied molecular orbital for the vinyl-substituted Criegee intermediates. These results would help us better estimate the impact of similar reactions like the reactions of Criegee intermediates with water vapor, some of which could be difficult to measure experimentally but can be important in the atmosphere. We also found that the B2PLYP-D3BJ/aug-cc-pVTZ calculation can reproduce the CCSD(T)-F12 reaction barrier energies within ca. 1 kcal mol-1, indicating that the use of the B2PLYP-D3BJ method is promising for future predictions of the reactions of larger Criegee intermediates.

PEG-stabilized coaxial stacking of two-dimensional covalent organic frameworks for enhanced photocatalytic hydrogen evolution.

Two-dimensional covalent organic frameworks (2D COFs) featuring periodic frameworks, extended π-conjugation and layered stacking structures, have emerged as a promising class of materials for photocatalytic hydrogen evolution. Nevertheless, the layer-by-layer assembly in 2D COFs is not stable during the photocatalytic cycling in water, causing disordered stacking and declined activity. Here, we report an innovative strategy to stabilize the ordered arrangement of layered structures in 2D COFs for hydrogen evolution. Polyethylene glycol is filled up in the mesopore channels of a ß-ketoenamine-linked COF containing benzothiadiazole moiety. This unique feature suppresses the dislocation of neighbouring layers and retains the columnar π-orbital arrays to facilitate free charge transport. The hydrogen evolution rate is therefore remarkably promoted under visible irradiation compared with that of the pristine COF. This study provides a general post-functionalization strategy for 2D COFs to enhance photocatalytic performances.

Evaluation of Ar tagging toward the vibrational spectra and zero point energy of X-HOH, X-DOH, and X-HOD, for X = F, Cl, Br.

In this study, we theoretically evaluated the effect of argon tagging toward the binding energy and vibrational spectra of water halide anion complexes Ar.X-HOH, Ar.X-HOD, and Ar.X-DOH (X = F, Cl, Br). The ionic hydrogen bond (IHB) OH stretching mode was calculated to have a strong peak in the vibrational spectra, and coupling to intermolecular modes as well as bending modes was observed as combination bands and Fermi resonances. We found that the argon tagging affected the IHB OH stretching peak position in Ar.F-H2O, but not in Ar.Cl-H2O and Ar.Br-H2O. Furthermore, D-binding is favored for Cl and Br based on zero point energies, but for F our calculated zero point energies did not show a preference between H- and D-binding. We show that the competition of the energy lowering in the zero point energy of the anharmonic IHB OH (OD) stretching mode versus the intermolecular out-of-plane IHB OH (OD) wagging mode is important for determining the preference between H- and D-binding for these monohydrated halide clusters. We also found that for X-HOD the HOD bending fundamental peak is blue shifted compared to bare HOD, but is redshifted for F-DOH.

Surprisingly long lifetime of methacrolein oxide, an isoprene derived Criegee intermediate, under humid conditions.

Ozonolysis of isoprene, the most abundant alkene, produces three distinct Criegee intermediates (CIs): CH2OO, methyl vinyl ketone oxide (MVKO) and methacrolein oxide (MACRO). The oxidation of SO2 by CIs is a potential source of H2SO4, an important precursor of aerosols. Here we investigated the UV-visible spectroscopy and reaction kinetics of thermalized MACRO. An extremely fast reaction of anti-MACRO with SO2 has been found, kSO2 = (1.5 ± 0.4) × 10-10 cm3 s-1 (±1σ, σ is the standard deviation of the data) at 298 K (150 - 500 Torr), which is ca. 4 times the value for syn-MVKO. However, the reaction of anti-MACRO with water vapor has been observed to be quite slow with an effective rate coefficient of (9 ± 5) × 10-17 cm3 s-1 (±1σ) at 298 K (300 to 500 Torr), which is smaller than current literature values by 1 or 2 orders of magnitude. Our results indicate that anti-MACRO has an atmospheric lifetime (best estimate ca. 18 ms at 298 K and RH = 70%) much longer than previously thought (ca. 0.3 or 3 ms), resulting in a much higher steady-state concentration. Owing to larger reaction rate coefficient, the impact of anti-MACRO on the oxidation of atmospheric SO2 would be substantial, even more than that of syn-MVKO.