14172-90-8Relevant articles and documents
Ionic multi-component complexes containing TDAE·+ and C60·- radical ions and neutral D1 molecules: D1·TDAE·C60
Konarev, Dmitri V.,Neretin, Ivan S.,Saito, Gunzi,Slovokhotov, Yury L.,Otsuka, Akihiro,Lyubovskaya, Rimma N.
, p. 3886 - 3891 (2003)
New ionic complexes containing TDAE·+ and C60·- radical ions and neutral molecules: (TBPDA)2·TDAE·C60 (1); CTV·TDAE·C60 (2); and CoIITPP·TDAE·C60 (3) (TDAE: tetrakis(dimethylamino)ethylene; TBPDA: N,N,N′,N′-tetrabenzyl-p-phenylenediamine; CTV: cyclotriveratrylene and CoIITPP: tetraphenylporphyrinate cobalt (II)) were obtained as single crystals. The presence of TDAE·+, C60·- and neutral donors in 1-3 was proved by optical absorption spectra in the IR and UV-vis-NIR ranges. In the crystal structure of 1 studied by single crystal X-ray diffraction, TDAE·+ and C60·- are spatially separated by bulky TBPDA molecules. Magnetic susceptibilities of 1 and 2 follow the Curie-Weiss law with the negative Weiss temperatures (-2.3 and -2.0 K) and their magnetic moments decrease below 60 and 15 K, respectively. The EPR signals from 1 and 2 at the same temperatures are split into two components, which shift in the opposite directions to lower and higher fields with the temperature decrease. This phenomenon is explained by the formation of field-induced short-range magnetically ordered clusters. CoIITPP and C60·- form diamagnetic σ-bonded (CoIITPP·C60-) anions in 3 in the 1.9-190 K range. This allows one to observe the EPR signal from the isolated TDAE·+ radical cations (g = 2.0031 and halfwidth = ΔH = 3.22 mT at 4 K). Above 190 K the magnetic moment of 3 increases and the EPR signal is essentially broadened and shifted to a lager g-factor (g = 2.0194, ΔH = 24.2 mT at 290 K). This is attributed to the dissociation of the σ-bonded diamagnetic (CoIITPP·C60-) anions to non-bonded paramagnetic CoIITPP and C60·- components.
Concerning the deactivation of cobalt(III)-based porphyrin and salen catalysts in epoxide/CO2 copolymerization
Xia, Wei,Salmeia, Khalifah A.,Vagin, Sergei I.,Rieger, Bernhard
, p. 4384 - 4390 (2015)
Functioning as active catalysts for propylene oxide (PO) and carbon dioxide copolymerization, cobalt(III)-based salen and porphyrin complexes have drawn great attention owing to their readily modifiable nature and promising catalytic behavior, such as high selectivity for the copolymer formation and good regioselectivity with respect to the polymer microstructure. Both cobalt(III)-salen and porphyrin catalysts have been found to undergo reduction reactions to their corresponding catalytically inactive cobalt(II) species in the presence of propylene oxide, as evidenced by UV/Vis and NMR spectroscopies and X-ray crystallography (for cobalt(II)-salen). Further investigations on a TPPCoCl (TPP=tetraphenylporphyrin) and NaOMe system reveal that such a catalyst reduction is attributed to the presence of alkoxide anions. Kinetic studies of the redox reaction of TPPCoCl with NaOMe suggests a pseudo-first order in cobalt(III)-porphyrin. The addition of a co-catalyst, namely bis(triphenylphosphine)iminium chloride (PPNCl), into the reaction system of cobalt(III)-salen/porphyrin and PO shows no direct stabilizing effect. However, the results of PO/CO2 copolymerization by cobalt(III)-salen/porphyrin with PPNCl suggest a suppressed catalyst reduction. This phenomenon is explained by a rapid transformation of the alkoxide into the carbonate chain end in the course of the polymer formation, greatly shortening the lifetime of the autoreducible PO-ring-opening intermediates, cobalt(III)-salen/porphyrin alkoxides.
Hoshino, Mikio
, p. 50 - 52 (1985)
Olefin oxidation with dioxygen catalyzed by porphyrins and phthalocyanines intercalated in α-zirconium phosphate
Ni?o, Martha E,Giraldo, Sonia A,Páez-Mozo, Edgar A
, p. 139 - 151 (2001)
Oxidation of cyclohexene and cis-stilbene with dioxygen in presence of metal phthalocyanines or metal tetraphenylporphyrins complexes intercalated in α-zirconium phosphate and isobutyraldehyde were studied. The degradation of free metal complexes in solution in the reaction media was verified. It was observed that the matrix protects the metal complexes from degradation and the activity of the catalytic system is preserved. Oxidation of cyclohexene with intercalated complexes gave epoxide as the predominant product, while allylic oxidation products were obtained in smaller proportion and the product distributions depended on the identity of the individual metal complexes. Since the addition of a free radical inhibitor stops the reaction, a free radical mechanism should be present. Oxidation of cis-stilbene with intercalated metal complexes gives different ratios of cis- to trans-stilbene oxide and of benzaldehyde which depend on the intercalated metal complex, suggesting that in addition to the free radicals there is another active oxidizing agent.
Direct synthesis of a metalloporphyrin complex on a surface
Gottfried, J. Michael,Flechtner, Ken,Kretschmann, Andreas,Lukasczyk, Thomas,Steinrueck, Hans-Peter
, p. 5644 - 5645 (2006)
We demonstrate that well-defined monolayers of a metal complex on a surface can be prepared by direct vapor deposition of the metal atoms on monolayers of the ligand. In particular, ordered monolayers of adsorbed tetraphenylporphyrin (2H-TPP) on a silver surface were exposed to cobalt vapors, resulting in the complexation of the metal by the porphyrin. The formation of the metal complexes was monitored by means of X-ray photoelectron spectroscopy (XPS), which reveals that this metalation reaction leads to a chemical equivalence of all four nitrogen atoms. The described in situ metalation provides a convenient way to produce adsorbed monolayers of more reactive (e.g., air- or solvent-sensitive) or thermally unstable metalloporphyrins that are difficult to evaporate or even to obtain as pure compounds at room temperature. Copyright
Dye-sensitizer effects on a Pt/KTa(Zr)O3 catalyst for the photocatalytic splitting of water
Hagiwara, Hidehisa,Ono, Naoko,Inoue, Takanori,Matsumoto, Hiroshige,Ishihara, Tatsumi
, p. 1420 - 1422 (2006)
(Figure Presented) Back to the elements: The activity of Pt/K 0.95Ta0.92Zr0.08O3 for the photocatalytic splitting of water into H2 and O2 is greatly improved by dye sensitization (see picture). Among the organic dyes examined, the highest photocatalytic activity is obtained with cyanocobalamin (vitamin B12) as a sensitizer.
Axial Modification of Cobalt Complexes on Heterogeneous Surface with Enhanced Electron Transfer for Carbon Dioxide Reduction
Huang, Xiang,Wang, Jiong,Wang, Xin,Xi, Shibo,Xu, Hu
, p. 19162 - 19167 (2020)
Efficient electron communication between molecular catalyst and support is critical for heterogeneous molecular electrocatalysis and yet it is often overlooked during the catalyst design. Taking CO2 electro-reduction on tetraphenylporphyrin cobalt (PCo) immobilized onto graphene as an example, we demonstrate that adding a relay molecule improves the interfacial electron communication. While the directly immobilized PCo on graphene exhibits relatively poor electron communications, it is found that diphenyl sulfide serves as an axial ligand for PCo and it improves the redox activity of PCo on the graphene surface to facilitate the generation of [PCo].- active sites for CO2 reduction. Thus, the turnover frequencies of the immobilized Co complexes are increased. Systematic structural analysis indicates that the benzene rings of diphenyl sulfide exhibit strong face-to-face stacking with graphene, which is proposed as an efficient medium to facilitate the interfacial electron communication.
A flexible bis-Co(III) porphyrin cage as a bimetallic catalyst for the conversion of CO2 and epoxides into cyclic carbonates
Schoepff, Laetitia,Monnereau, Laure,Durot, Stéphanie,Jenni, Sébastien,Gourlaouen, Christophe,Heitz, Valérie
, p. 5826 - 5833 (2020)
A molecular cage consisting of two free-base porphyrins connected by four flexible linkers was metalated with Co(III) to afford in good yield a bimetallic catalyst. The catalytic activity of the bis-Co(III) porphyrin molecular cage (CoCl)2-1 was studied for the formation of cyclic carbonates from CO2 and propylene oxide (PO) or styrene oxide (SO) with pyridine as cocatalyst. Various reaction parameters such as the molar ratio of the catalyst and the co-catalyst, the time of reaction, the temperature and CO2 pressure were investigated. The molecular cage was shown to be a catalyst of high selectivity for the studied reactions and much more efficient to convert the epoxides to the corresponding cyclic carbonates than the monomeric Co(III)Cl meso-tetraphenylporphyrin (CoCl-TPP) model. When quantitative conversion of PO into propylene carbonate (PC) was reached (0.1 mol% catalyst, 1.2 mol% pyridine, 120 °C, 30 bar of CO2) only 23 % of PC was obtained with CoCl-TPP (0.2 mol%). This enhanced catalytic activity is attributed to the synergistic effect of the two metal sites incorporated in the framework of the molecular cage.
Synthesis and spectral properties of cobalt(II) and cobalt(III) tetraarylporphyrinates
Chizhova,Kumeev,Mamardashvili, N. Zh.
, (2013)
Reactions of 5,10,15,20-tetraphenylporphin, 5,10,15,20-tetra(4′- methoxyphenyl)porphyrin, and 5,10,15,20-tetra(4′-chlorophenyl)porphyrin with cobalt(II) acetate in dimethylformamide were studied by spectrophotometry. The corresponding cobalt(II) porphyrin
A biomimetic photoelectrocatalyst of Co-porphyrin combined with a g-C3N4 nanosheet based on π-π Supramolecular interaction for high-efficiency CO2 reduction in water medium
Liu, Jibo,Shi, Huijie,Shen, Qi,Guo, Chenyan,Zhao, Guohua
, p. 5900 - 5910 (2017)
Aiming at high-efficiency biomimetic CO2 photoelectrochemical conversion, a photoelectrocatalyst with excellent CO2 catalytic activity was designed and prepared by immobilizing CoTPP (cobalt meso-tetraphenylporphyrin) onto g-C3N4 conveniently via self-assembly based on π-π supramolecular interaction. The quasi 3-D structure of CoTPP showed a suitable hole with a size of 3.8 ? × 9.6 ? which favoured CO2 adsorption. The pores formed by the π-π stacking of CoTPP and g-C3N4 also provided additional space for CO2 adsorption, which was confirmed by the appearance of a desorption peak at 250 °C in the temperature programmed desorption measurement for CoTPP/g-C3N4. As a normal efficient homogeneous catalyst in organic media, CoTPP commendably maintained outstanding CO2 photoelectrocatalytic activity in heterogeneous aqueous solution, even at a low overpotential of -0.6 V (vs. normal hydrogen electrode, NHE). Under 8 h PEC CO2 reduction, formic acid generation on CoTPP/g-C3N4 reached 154.4 μmol with a TON of 137 and high selectivity of nearly 100% in liquid products. The formation of CoTPP-COO- and CoTPP-COOH intermediates by the Co(ii) active site and CO2 was investigated by in situ UV-vis and Raman spectra. Moreover, an isotopic labelling experiment indicated that water supplied abundant protons for the production of formic acid.
A Br-regulated transition metal active-site anchoring and exposure strategy in biomass-derived carbon nanosheets for obtaining robust ORR/HER electrocatalysts at all pH values
Lv, Xuehui,Chen, Yanli,Wu, Yanling,Wang, Haoyuan,Wang, Xinlong,Wei, Chuangyu,Xiao, Zuoxu,Yang, Guangwu,Jiang, Jianzhuang
, p. 27089 - 27098 (2019)
A novel Br-regulated "Transition Metal Active-site Anchoring and Exposure" (TMAAE) strategy is reported, for the first time, to fabricate a hierarchical porous Co/N-doped bio-carbon bifunctional electrocatalyst (CoTBrPP?bio-C) for an all-pH ORR and HER by using a simple one-pot co-pyrolysis over a mushroom (MR) template with adsorbed Br-substituted porphyrinato cobalt (CoTBrPP). Introduction of CoTBrPP onto the MR template not only leads to a larger specific area of 604 m2 g-1 in CoTBrPP?bio-C relative to that of CoTPP?bio-C (CoTPP = Br-free CoTBrPP), 98 m2 g-1, but more importantly also regulates the oriented distribution of pores precisely which promotes effective exposure of multiple active sites depending on the departure of Br-species attached to the Co-N4 macrocycle periphery. Impressively, CoTBrPP?bio-C with a Co loading down to 0.77 at% exhibits higher all-pH ORR and HER performance compared to CoTPP?bio-C with a Co loading of 3.5 at%. An efficient TMAAE makes CoTBrPP?bio-C possess higher onset and half-wave potentials of 0.93 and 0.85 V for the ORR, and a smaller Tafel slope of 80 mV dec-1 for the HER in an alkaline medium. CoTBrPP?bio-C also had a superior all-pH long-term stability and outstanding methanol tolerance, surpassing commercial Pt/C and most non-precious-metal catalysts reported to date. Furthermore, Zn-air batteries assembled with CoTBrPP?bio-C exhibited a higher peak power density of 100 mW cm-2 and excellent durability than Pt/C.
Regarding Initial Ring Opening of Propylene Oxide in its Copolymerization with CO2 Catalyzed by a Cobalt(III) Porphyrin Complex
Xia, Wei,Vagin, Sergei I.,Rieger, Bernhard
, p. 15499 - 15504 (2014)
Cobalt(III) tetraphenylporphyrin chloride (TPPCoCl) was experimentally proved to be an active catalyst for poly(propylene carbonate) production. It was chosen as a model catalyst in the present work to investigate the initiation step of propylene oxide (PO)/CO2 copolymerization, which is supposed to be the ring opening of the epoxide. Ring-opening intermediates (1-7) were detected by using 1HNMR spectroscopy. A first-order reaction in TPPCoCl was determined. A combination of monometallic and bimetallic ring-opening pathways is proposed according to kinetics experiments. Addition of onium salts (e.g., bis(triphenylphosphine)iminium chloride, PPNCl) efficiently promoted the PO ring-opening rate. The existence of axial ligand exchange in the cobalt porphyrin complex in the presence of onium salts was suggested by analyzing collected 1HNMR spectra. Monometallic or bimetallic? Ring-opening intermediates of propylene oxide (PO) catalyzed by a cobalt(III) porphyrin complex were identified by using 1HNMR spectroscopy. The generated metal alkoxides underwent hydrolysis in the presence of trace amounts of water. A combined bimetallic and monometallic ring-opening pathway was suggested from the kinetics results. Addition of onium salts accelerated the PO ring opening. Ligand exchange on the cobalt center in the presence of onium salts was also detected.
Reaction, structure and spectroscopic properties of bis(cyano) cobalt(III) porphyrin complexes
Zhao, Jianping,He, Mingrui,Yao, Zhen,Cao, Hongli,Yuan, Yiwen,Bian, Yongzhong,Li, Jianfeng
, p. 825 - 834 (2021/06/18)
Cyanocobalamin and analogues have drawn much attention for the promising applications in photovoltaic and photocatalytic systems. In this study, two low spin bis(cyano) cobalt(III) porphyrin complexes [K(222)][CoIII(TPP)(CN)2] and [K(222)][CoIII(TMP)(CN)2] (222 = 4,7,13,16,21,24-hexaoxo-1,10-diazabicyclo[8.8.8]hexacosane, TPP = meso-tetraphenylporphyrin dianion, TMP = meso-tetramesitylporphyrin dianion), which were isolated from the reactions between [CoII(Porph)] (Porph = Porphyrin) and [K(222)(CN)], are characterized by a single crystal X-ray diffraction, FT-IR and UV-vis spectroscopies. Combined UV-vis and electron paramagnetic resonance (EPR) investigations have been conducted to understand the reaction mechanisms. The work gives new insights into the reactivities and spectroscopic properties of cyano cobalt macrocyclic complexes.
Efficient oxidation of cycloalkanes with simultaneously increased conversion and selectivity using O2 catalyzed by metalloporphyrins and boosted by Zn(AcO)2: A practical strategy to inhibit the formation of aliphatic diacids
Shen, Hai-Min,Wang, Xiong,Ning, Lei,Guo, A-Bing,Deng, Jin-Hui,She, Yuan-Bin
, (2020/11/20)
The direct sources of aliphatic acids in cycloalkanes oxidation were investigated, and a strategy to suppress the formation of aliphatic acids was adopted through enhancing the catalytic transformation of oxidation intermediates cycloalkyl hydroperoxides to cycloalkanols by Zn(II) and delaying the emergence of cycloalkanones. Benefitted from the delayed formation of cycloalkanones and suppressed non-selective thermal decomposition of cycloalkyl hydroperoxides, the conversion of cycloalkanes and selectivity towards cycloalkanols and cycloalkanones were increased simultaneously with satisfying tolerance to both of metalloporphyrins and substrates. For cyclohexane, the selectivity towards KA-oil was increased from 80.1% to 96.9% meanwhile the conversion was increased from 3.83 % to 6.53 %, a very competitive conversion level with higher selectivity compared with current industrial process. This protocol is not only a valuable strategy to overcome the problems of low conversion and low selectivity lying in front of current cyclohexane oxidation in industry, but also an important reference to other alkanes oxidation.