201230-82-2Relevant articles and documents
A Ru(II)-Mn(I) Supramolecular Photocatalyst for CO2 Reduction
Fabry, David C.,Koizumi, Hiroki,Ghosh, Debashis,Yamazaki, Yasuomi,Takeda, Hiroyuki,Tamaki, Yusuke,Ishitani, Osamu
, p. 1511 - 1518 (2020)
Supramolecular photocatalysts for CO2 reduction, constituted of redox photosensitizer, catalyst, and bridging ligand, play crucial roles in constructing hybrid systems with solid materials and photoelectrochemical cells for artificial photosynthesis. We report the first supramolecular photocatalysts with a Mn(I) catalyst [MnBr(CO)3(BL)] and photosensitizer unit(s) [Ru(dmb)2(BL)]2+ (dmb = 4,4′-dimethyl-2,2′-bipyridine, BL = bridging ligand). A 1:1 ratio between the redox photosensitizer and catalyst units showed higher activity for HCOOH formation in comparison to the corresponding mixed system of mononuclear complexes.
Atmospheric sink of methyl chlorodifluoroacetate and ethyl chlorodifluoroacetate: Temperature dependent rate coefficients, product distribution of their reactions with Cl atoms and CF2ClC(O)OH formation
Blanco, María B.,Barnes, Ian,Wiesen, Peter,Teruel, Mariano A.
, p. 51834 - 51844 (2016)
Rate coefficients as a function of temperature have been measured for the first time for the gas-phase reactions of chlorine atoms with methyl chlorodifluoracetate (k1) and ethyl chlorodifluoroacetate (k2) using the relative rate technique. The experiments were carried out in a 1080 L photoreactor over the temperature range 287-313 K at a total pressure of 1000 ± 10 mbar of synthetic air using in situ FTIR spectroscopy to monitor reactants and products. The following Arrhenius expressions were obtained: k(MCDFA+Cl) = (9.6 ± 5.1) × 10-12exp[-(1363 ± 79)/T] and k(ECDFA+Cl) = (64.4 ± 29.7) × 10-12exp[-(1110 ± 68)/T]. The kinetic results are compared with previous experimental and theoretical studies. In addition, a product study of the reactions of Cl with methyl chlorodifluoracetate and ethyl chlorodifluoroacetate is reported. The results indicate that in the absence of NOx the main fate of the alkoxy radicals formed after H-atom abstraction by Cl from the -CH3 group in methyl chlorodifluoroacetate is reaction of the radical with O2 to form the mixed anhydride CF2ClC(O)OC(O)H. In the case of ethyl chlorodifluoroacetate the main fate of the alkoxy formed via H-atom abstraction by Cl from the -CH2- entity in the ethyl group is α-ester rearrangement to produce chlorodifluoroacetic acid and the corresponding radical. The yields of chlorofluoracetic acid (CF2ClC(O)OH) obtained were as follows: (34 ± 5)% and (86 ± 8)% for the reactions of Cl with CF2ClC(O)OCH3 and CF2ClC(O)OCH2CH3, respectively. The measured yields are rationalized in terms of mechanisms consisting of competitive reaction channels for the formed products in the oxidation, i.e. reaction with O2, α-ester rearrangement and a decomposition pathway. Atmospheric implications are discussed according to the rate coefficients obtained as a function of temperature and altitude, and regarding the formation of chlorofluorocarboxylic acid.
Investigation of the thermal decomposition of ketene and of the reaction CH2 + H2 ? CH3 + H
Friedrichs, Gernot,Wagner, Heinz Gg.
, p. 1601 - 1623 (2001)
Using frequency modulation (FM) spectroscopy singlet methylene radicals have been detected for the first time behind shock waves. The thermal decomposition of ketene served as source for metylene radicals at temperatures from 1905 to 2780 K and pressures around 450 mbar. For the unimolecular decomposition reaction, (1) CH2CO+M → CH2 +CO+M, the rate constants obtained are: k1 = (9.5±5.7) · 1015 · exp[(-244±25) kJ mol-1/RT] cm3mol-1 s-1. As a first study of a methylene reaction at high temperatures by diretly tracing methylene the reaction of methylene with hydrogen, (8+9) 1.3CH2 + H2 → CH3 + H, was investigated at temperatures from 1930 to 2455 K and pressures around 500 mbar. For the total rate constant of the singlet and triplet methylene reaction a temperature independent value was obtained: log(kg+9/(cm3mol-1s-1)) = 13.89±0.26. A comparison with low temperature literature data and the systematics of activation energies of triplet methylene reactions allowed a consistent description of singlet and triplet contributions and of the forward and reverse reaction. by Oldenbourg Wissenschaftsverlag, Muenchen.
Phenyl-grafted carbon nitride semiconductor for photocatalytic CO2-reduction and rapid degradation of organic dyes
Vidyasagar, Devthade,Manwar, Nilesh,Gupta, Akanksha,Ghugal, Sachin G.,Umare, Suresh S.,Boukherroub, Rabah
, p. 822 - 832 (2019)
Molecular engineering of graphitic carbon nitride (g-C3N4) is achieved by the copolymerization of π-conjugated phenyl urea, melamine, and urea. Integration of aromatic phenyl rings into the heptazine network of g-C3N4 alters its structural, optical and electronic properties. The fusion of the polymeric g-C3N4 core with aromatic phenyl groups induces band gap tuning, which greatly improves the separation and lifetime of charge-carriers. As a result, CO2 photoreduction experiments conducted by using phenyl-grafted g-C3N4 afford methane and formic acid in high yields. Furthermore, a selective model organic pollutant rhodamine B dye is rapidly decomposed under visible-light irradiation. This work suggests that pyrolysis of a suitable aromatic π-deficient molecular dopant such as phenyl urea can drastically alter the photo-response of the carbon nitride photocatalyst and may enhance its photocatalytic activity. Hence, the present work is expected to be of significant value in sustainable energy production and environmental remediation.
Photoactivity of mono- and dicarbonyl complexes of ruthenium(II) bearing an N,N,S-donor ligand: Role of ancillary ligands on the capacity of CO photorelease
Gonzalez, Margarita A.,Carrington, Samantha J.,Chakraborty, Indranil,Olmstead, Marilyn M.,Mascharak, Pradip K.
, p. 11320 - 11331 (2013)
One monocarbonyl and one dicarbonyl complex of ruthenium(II), namely, [Ru(Cl)(CO)(qmtpm)(PPh3)]BF4 (2) and [Ru(Cl)(CO) 2(qmtpm)]ClO4 (3), derived from the tridentate ligand 2-quinoline-N-(2′-methylthiophenyl)methyleneimine (qmtpm) have been synthesized and structurally characterized. The qmtpm ligand binds in a meridional fashion in these carbonyl complexes, and in 3, the two carbon monoxide (CO) ligands are cis to each other. Solutions of 2 in ethanol, chloroform, or acetonitrile rapidly release CO upon illumination with low-power (3-15 mW) light in the 300-450 nm range. Loss of CO from 2 brings about a dramatic color change from yellow to magenta because of the formation of [Ru(Cl)(MeCN)(qmtpm)(PPh3)]BF4 (4). In acetonitrile, photorelease of CO from 3 under 360 nm light occurs in two steps, and the violet photoproduct [Ru(Cl)(MeCN)2(qmtpm)]+ upon reaction with Ag+ and PPh3 affords red [Ru(MeCN)2(qmtpm) (PPh3)](ClO4)2 (5). The structure of 5 has also been determined by X-ray crystallography. Reduced myoglobin assay confirms that 2 and 3 act as photoactive CO-releasing molecules (photoCORMs) that deliver 1 and 2 equiv of CO, respectively. The results of density functional theory (DFT) and time-dependent DFT studies confirm that electronic transitions from molecular orbitals with predominantly Ru-CO character to ligand-based π* orbitals facilitate CO release from these two photoCORMs. Complexes 2-5 have provided an additional opportunity to analyze the roles of the ancillary ligands, namely, PPh3, Cl-, and MeCN, in shifting the positions of the metal-to-ligand charge-transfer bands and the associated sensitivity of the two photoCORMs to different wavelengths of light. Collectively, the results provide helpful hints toward the future design of photoCORMs that release CO upon exposure to visible light.
The p-Orbital Delocalization of Main-Group Metals to Boost CO2 Electroreduction
He, Sisi,Ni, Fenglou,Ji, Yujin,Wang, Lie,Wen, Yunzhou,Bai, Haipeng,Liu, Gejun,Zhang, Ye,Li, Youyong,Zhang, Bo,Peng, Huisheng
, p. 16114 - 16119 (2018)
Enhancing the p-orbital delocalization of a Bi catalyst (termed as POD-Bi) via layer coupling of the short inter-layer Bi?Bi bond facilitates the adsorption of intermediate *OCHO of CO2 and thus boosts the CO2 reduction reaction (CO2RR) rate to formate. X-ray absorption fine spectroscopy shows that the POD-Bi catalyst has a shortened inter-layer bond after the catalysts are electrochemically reduced in situ from original BiOCl nanosheets. The catalyst on a glassy carbon electrode exhibits a record current density of 57 mA cm?2 (twice the state-of-the-art catalyst) at ?1.16 V vs. RHE with an excellent formate Faradic efficiency (FE) of 95 %. The catalyst has a record half-cell formate power conversion efficiency of 79 % at a current density of 100 mA cm?2 with 93 % formate FE when applied in a flow-cell system. The highest rate of the CO2RR production reported (391 mg h?1 cm2) was achieved at a current density of 500 mA cm?2 with formate FE of 91 % at high CO2 pressure.
CO2 hydrogenation to methanol on Ga2O3-Pd/SiO2 catalysts: Dual oxide-metal sites or (bi)metallic surface sites?
Collins, Sebastián E.,Baltanás, Miguel A.,Delgado, Juan José,Borgna, Armando,Bonivardi, Adrian L.
, p. 154 - 162 (2021)
A series of palladium (2 wt.%) catalysts supported on silica (301 m2/g) and loaded with increasing amount of gallium – ratio of Ga/Pd = 2, 4 and 8 atom/atom – were investigated for CO2 hydrogenation to methanol. The turnover frequency to methanol (H2/CO2 = 3; 523 K, 3 MPa), based on surface palladium, showed a 200-fold enhancement as compared to the monometallic Pd/SiO2 catalyst. Additionally, the apparent activation energy for methanol synthesis decreased from 60 kJ/mol on Pd/SiO2 to ～40 kJ/mol on the supported Ga-Pd catalysts. Characterization of the Pd-Ga catalyst series by X-ray absorption spectroscopy and high resolution transmission electron microscopy indicates the formation of Pd2Ga bimetallic nanoparticles partially covered by a thin layer of Ga2O3 on the silica surface. In situ infrared spectroscopy was employed to examine the reaction mechanism during the CO2 adsorption and hydrogenation at 0.7 MPa. It is proposed a bifunctional pathway where the carbonaceous species bound to the gallium oxide surface are hydrogenated, stepwise, to formate and methoxy groups by atomic hydrogen, which spillovers from the Pd-Ga bimetallic nanoparticles.
Dynamic Changes in the Structure, Chemical State and Catalytic Selectivity of Cu Nanocubes during CO2 Electroreduction: Size and Support Effects
Grosse, Philipp,Gao, Dunfeng,Scholten, Fabian,Sinev, Ilya,Mistry, Hemma,Roldan Cuenya, Beatriz
, (2018)
In situ and operando spectroscopic and microscopic methods were used to gain insight into the correlation between the structure, chemical state, and reactivity of size- and shape-controlled ligand-free Cu nanocubes during CO2 electroreduction (
Click and Release: A Chemical Strategy toward Developing Gasotransmitter Prodrugs by Using an Intramolecular Diels–Alder Reaction
Ji, Xingyue,Zhou, Cheng,Ji, Kaili,Aghoghovbia, Robert E.,Pan, Zhixiang,Chittavong, Vayou,Ke, Bowen,Wang, Binghe
, p. 15846 - 15851 (2016)
Prodrug strategies have been proven to be a very effective way of addressing delivery problems. Much of the chemistry in prodrug development relies on the ability to mask an appropriate functional group, which can be removed under appropriate conditions. However, developing organic prodrugs of gasotransmitters represent unique challenges. This is especially true with carbon monoxide, which does not have an easy “handle” for bioreversible derivatization. By taking advantage of an intramolecular Diels–Alder reaction, we have developed a prodrug strategy for preparations of organic CO prodrugs that are stable during synthesis and storage, and yet readily release CO with tunable release rates under near physiological conditions. The effectiveness of the CO prodrug system in delivering a sufficient quantity of CO for possible therapeutic applications has been studied using a cell culture anti-inflammatory assay and a colitis animal model. These studies fully demonstrate the proof of concept, and lay a strong foundation for further medicinal chemistry work in developing organic CO prodrugs.
Changing the Product Selectivity for Electrocatalysis of CO2 Reduction Reaction on Plated Cu Electrodes
Li, Hong,Qin, Xianxian,Jiang, Tianwen,Ma, Xian-Yin,Jiang, Kun,Cai, Wen-Bin
, p. 6139 - 6146 (2019)
Electrochemical reduction of carbon dioxide (CO2RR) on various types of Cu electrodes to useful chemicals and fuels has attracted much attention. Herein, we comparatively investigate the distributions of CO2RR products over electroplated Cu, chemically plated boron-doped Cu (Cu?B) and electroplated phosphorus-doped Cu (Cu?P) electrodes. A global Faradaic efficiency of more than 50 % can be reached for the C2+ (ethylene, ethanol and n-propanol) products on both plated Cu?B and Cu?P electrodes at ～?1.15 V vs. RHE in 0.1 M KHCO3 electrolyte. Moreover, in situ surface enhanced infrared spectroscopy results together with quantitative analysis of the CO2RR products reveal a more facile conversion/depletion of the *CO intermediate after B- and P-doping, for which Cu?B promotes the C2+ products while Cu?P enhances both C2+ generation and CH4 evolution at faster *CO consumption. The present work suggests the vital role of *CO in the step of C?C bonding formation and highlights that the metalloid doping may alter the reactivity and selectivity of the intermediate.
