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1.
Modular optimization of metal–organic frameworks (MOFs) was realized by incorporation of coordinatively unsaturated single atoms in a MOF matrix. The newly developed MOF can selectively capture and photoreduce CO2 with high efficiency under visible‐light irradiation. Mechanistic investigation reveals that the presence of single Co atoms in the MOF can greatly boost the electron–hole separation efficiency in porphyrin units. Directional migration of photogenerated excitons from porphyrin to catalytic Co centers was witnessed, thereby achieving supply of long‐lived electrons for the reduction of CO2 molecules adsorbed on Co centers. As a direct result, porphyrin MOF comprising atomically dispersed catalytic centers exhibits significantly enhanced photocatalytic conversion of CO2, which is equivalent to a 3.13‐fold improvement in CO evolution rate (200.6 μmol g?1 h?1) and a 5.93‐fold enhancement in CH4 generation rate (36.67 μmol g?1 h?1) compared to the parent MOF.  相似文献   

2.
A conjugated copper(II) catecholate based metal–organic framework (namely Cu‐DBC) was prepared using a D2‐symmetric redox‐active ligand in a copper bis(dihydroxy) coordination geometry. The π‐d conjugated framework exhibits typical semiconducting behavior with a high electrical conductivity of ca. 1.0 S m?1 at room temperature. Benefiting from the good electrical conductivity and the excellent redox reversibility of both ligand and copper centers, Cu‐DBC electrode features superior capacitor performances with gravimetric capacitance up to 479 F g?1 at a discharge rate of 0.2 A g?1. Moreover, the symmetric solid‐state supercapacitor of Cu‐DBC exhibits high areal (879 mF cm?2) and volumetric (22 F cm?3) capacitances, as well as good rate capability. These metrics are superior to most reported MOF‐based supercapacitors, demonstrating promising applications in energy‐storage devices.  相似文献   

3.
We report the gas‐phase synthesis of stable 20‐electron carbonyl anion complexes of group 3 transition metals, TM(CO)8? (TM=Sc, Y, La), which are studied by mass‐selected infrared (IR) photodissociation spectroscopy. The experimentally observed species, which are the first octacarbonyl anionic complexes of a TM, are identified by comparison of the measured and calculated IR spectra. Quantum chemical calculations show that the molecules have a cubic (Oh) equilibrium geometry and a singlet (1A1g) electronic ground state. The 20‐electron systems TM(CO)8? are energetically stable toward loss of one CO ligand, yielding the 18‐electron complexes TM(CO)7? in the 1A1 electronic ground state; these exhibit a capped octahedral structure with C3v symmetry. Analysis of the electronic structure of TM(CO)8? reveals that there is one occupied valence molecular orbital with a2u symmetry, which is formed only by ligand orbitals without a contribution from the metal atomic orbitals. The adducts of TM(CO)8? fulfill the 18‐electron rule when only those valence electrons that occupy metal–ligand bonding orbitals are considered.  相似文献   

4.
Proton‐coupled electron‐transfer oxidation of a RuII?OH2 complex, having an N‐heterocyclic carbene ligand, gives a RuIII?O. species, which has an electronically equivalent structure of the RuIV=O species, in an acidic aqueous solution. The RuIII?O. complex was characterized by spectroscopic methods and DFT calculations. The oxidation state of the Ru center was shown to be close to +3; the Ru?O bond showed a lower‐energy Raman scattering at 732 cm?1 and the Ru?O bond length was estimated to be 1.77(1) Å. The RuIII?O. complex exhibits high reactivity in substrate oxidation under catalytic conditions; particularly, benzaldehyde and the derivatives are oxidized to the corresponding benzoic acid through C?H abstraction from the formyl group by the RuIII?O. complex bearing a strong radical character as the active species.  相似文献   

5.
Tripodal cadmium complex of hydrotris(3‐phenyl‐5‐methylpyrazolyl)borate (I1) and macrocyclic ligand 5,7 : 12,14 : 19,21 : 26,28‐Bzo4‐[28]‐5,13,19,27‐tetraene‐8,11,22,25‐N4–1,4,15,18‐O4 (I2), have been synthesized and characterized by IR, 1H NMR, Mass and elemental analysis. Spectroscopic investigations indicate high affinity of these receptors for dihydrogen phosphate ion. Polyvinyl chloride (PVC) based membranes of (I1) and (I2) using hexadecyl trimethylammonium bromide (HTAB) as cation discriminator and dibutylpthalate (DBP), tributyl phosphate (TBP), dioctylsebacate (DOS), and o‐nitrophenyloctyl ether (o‐NPOE), as plasticizing solvent mediators were prepared and investigated as H2PO selective sensors. The best performance was shown by the membrane of composition (w/w) (I2) (5%):PVC (31%) : DBP (61.5%):HTAB (2.5%). This sensor works well over a wide concentration range 2.1×10?7 to 1.0×10?2 M with Nernstian compliance (59.0 mV decade?1 of activity) with a fast response time of 14 s and showed good selectivity for dihydrogen phosphate ion over a number of anions. The sensor exhibits good reproducibility (SD±0.3 mV) and could be used successfully for the determination of phosphate in soil water samples.  相似文献   

6.
The electrochemical reduction reaction of carbon dioxide (CO2RR) to carbon monoxide (CO) is the basis for the further synthesis of more complex carbon‐based fuels or attractive feedstock. Single‐atom catalysts have unique electronic and geometric structures with respect to their bulk counterparts, thus exhibiting unexpected catalytic activities. A nitrogen‐anchored Zn single‐atom catalyst is presented for CO formation from CO2RR with high catalytic activity (onset overpotential down to 24 mV), high selectivity (Faradaic efficiency for CO (FECO) up to 95 % at ?0.43 V), remarkable durability (>75 h without decay of FECO), and large turnover frequency (TOF, up to 9969 h?1). Further experimental and DFT results indicate that the four‐nitrogen‐anchored Zn single atom (Zn‐N4) is the main active site for CO2RR with low free energy barrier for the formation of *COOH as the rate‐limiting step.  相似文献   

7.
Half‐sandwich manganese methylenephosphonium complexes [Cp(CO)2Mn(η2‐R2P?C(H)Ph)]BF4 were obtained in high yield through a straightforward reaction sequence involving a classical Fischer‐type manganese complex and a secondary phosphine as key starting materials. The addition of various nucleophiles (Nu) to these species took place regioselectively at the double‐bonded carbon center of the coordinated methylenephosphonium ligand R2P+?C(H)Ph to produce the corresponding chiral phosphine complexes [Cp(CO)2Mn(κ1‐R2P? C(H)(Ph)Nu)], from which the phosphines were ultimately recovered as free entities upon simple irradiation with visible light. The synthetic potential of this umpolung approach is illustrated herein by the preparation of novel chiral pincer‐type phosphine–NHC–phosphine ligand architectures.  相似文献   

8.
The reactivity of palladium complexes of bidentate diaryl phosphane ligands (P2) was studied in the reaction of nitrobenzene with CO in methanol. Careful analysis of the reaction mixtures revealed that, besides the frequently reported reduction products of nitrobenzene [methyl phenyl carbamate (MPC), N,N′‐diphenylurea (DPU), aniline, azobenzene (Azo) and azoxybenzene (Azoxy)], large quantities of oxidation products of methanol were co‐produced (dimethyl carbonate (DMC), dimethyl oxalate (DMO), methyl formate (MF), H2O, and CO). From these observations, it is concluded that several catalytic processes operate simultaneously, and are coupled via common catalytic intermediates. Starting from a P2Pd0 compound formed in situ, oxidation to a palladium imido compound P2PdII?NPh, can be achieved by de‐oxygenation of nitrobenzene 1) with two molecules of CO, 2) with two molecules of CO and the acidic protons of two methanol molecules, or 3) with all four hydrogen atoms of one methanol molecule. Reduction of P2PdII?NPh to P2Pd0 makes the overall process catalytic, while at the same time forming Azo(xy), MPC, DPU and aniline. It is proposed that the Pd–imido species is the central key intermediate that can link together all reduction products of nitrobenzene and all oxidation products of methanol in one unified mechanistic scheme. The relative occurrence of the various catalytic processes is shown to be dependent on the characteristics of the catalysts, as imposed by the ligand structure.  相似文献   

9.
Methylene blue (MB+) and pyrrole were copolymerised to electrodeposit a novel electroactive polymer on a Au electrode which was assessed for O2 sensing. The electroactive polymer exhibits diffusion‐limited behaviour and an electrochemical, followed by catalytic (EC′) mechanism in the presence of dissolved O2. Notably, it is pH‐insensitive in both N2‐purged and air‐equilibrated phosphate buffered saline (PBS) from pH 4 to 8. It is stable over 18 days, possesses a good sensitivity of 256.335 µA mM?1 cm?2, wide linear range of 15 µM to 285 µM and detection limit of 1.47 µM (S/N=3) for dissolved O2. It is highly promising for use in biological investigations where pH fluctuations are expected.  相似文献   

10.
Metal complexes have been widely investigated as promising electrocatalysts for CO2 reduction. Most of the current research efforts focus mainly on ligands based on pyrrole subunits, and the reported activities are still far from satisfactory. A novel planar and conjugated N4‐macrocyclic cobalt complex (Co(II)CPY) derived from phenanthroline subunits is prepared herein, and it delivers high activity for heterogeneous CO2 electrocatalysis to CO in aqueous media, and outperforms most of the metal complexes reported so far. At a molar loading of 5.93×10?8 mol cm?2, it exhibits a Faradaic efficiency of 96 % and a turnover frequency of 9.59 s?1 towards CO at ?0.70 V vs. RHE. The unraveling of electronic structural features suggests that a synergistic effect between the ligand and cobalt in Co(II)CPY plays a critical role in boosting its activity. As a result, the free energy difference for the formation of *COOH is lower than that with cobalt porphyrin, thus leading to enhanced CO production.  相似文献   

11.
A density functional theory calculation has been carried out to investigate the mechanism of W(CO)6 and W2(CO)10 catalyzed water-gas-shift reaction (WGSR). The calculations indicate that the bimetallic catalyst (W2(CO)10) would be likely to be more highly active than the mononuclear metal-based catalyst (W(CO)6) due to the possibility of metal–metal cooperativity in reducing the barriers for the WGSR. The energetic span model is a tool to compute catalytic turnover frequencies (TOFs) which is the traditional measure of the efficiency of a catalyst. The one with the highest efficiency usually gives the highest TOF. The bimetallic catalyst (W2(CO)10) exhibits high catalytic activity towards WGSR due to the highest value of the calculated TOF (3.62 × 10?12 s?1, gas phase; 8.74 × 10?15 s?1, solvent phase), which is higher than the value of TOF (8.96 × 10?20 s?1, gas phase; 3.96 × 10?19 s?1, solvent phase) proposed by Kuriakose et al. (Inorg Chem 51:377–385, 2012). Our results will be important for designing a better catalyst for the industrially important reaction.  相似文献   

12.
The reactions of mono‐ and bidentate aromatic nitrogen‐containing ligands with [Ru(CO)3Cl2]2 in alcohols have been studied. In alcoholic media the nitrogen ligands act as bases promoting acidic behaviour of alcohols and the formation of alkoxy carbonyls [Ru(N–N)(CO)2Cl(COOR)] and [Ru(N)2(CO)2Cl(COOR)]. Other products are monomers of type [Ru(N)(CO)3Cl2], bridged complexes such as [Ru(CO)3Cl2]2(N), and ion pairs of the type [Ru(CO)3Cl3]? [Ru(N–N)(CO)3Cl]+ (N–N = chelating aromatic nitrogen ligand, N = non‐chelating or bridging ligand). The reaction and the product distribution can be controlled by adjusting the reaction stoichiometry. The reactivity of the new ruthenium complexes was tested in 1‐hexene hydroformylation. The activity can be associated with the degree of stability of the complexes and the ruthenium–ligand interaction. Chelating or bridging nitrogen ligands suppresses the activity strongly compared with the bare ruthenium carbonyl chloride, while the decrease in activity is less pronounced with monodentate ligands. A plausible catalytic cycle is proposed and discussed in terms of ligand–ruthenium interactions. The reactivity of the ligands as well as the catalytic cycle was studied in detail using the computational DFT methods. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

13.
Complex fac‐[Fe(CO)3(TePh)3]? was employed as a “metallo chelating” ligand to synthesize the neutral (CO)3Mn(μ‐TePh)3Fe(CO)3 obtained in a one‐step synthesis by treating fac‐[Fe(CO)3(TePh)3]? with fac‐[Mn‐(CO)3(CH3CN)3]+. It seems reasonable to conclude that the d6 Fe(II) [(CO)3Fe(TePh)3]? fragment is isolobal with the d6 Mn(I) [(CO)3Mn(TePh)3]2? fragment in complex (CO)3Mn(μ‐TePh)3Fe(CO)3. Addition of fac‐[Fe(CO)3(TePh)3]? to the CpNi(I)(PPh3) in THF resulted in formation of the neutral CpNi(TePh)(PPh3) also obtained from reaction of CpNi(I)(PPh3) and [Na][TePh] in MeOH. This investigation shows that fac‐[Fe(CO)3(TePh)3]? serves as a tridentate metallo ligand and tellurolate ligand‐transfer reagent. The study also indicated that the fac‐[Fe(CO)3(SePh)3]? may serve as a better tridentate metallo ligand and chalcogenolate ligand‐transfer reagent than fac‐[Fe(CO)3(TePh)3]? in the syntheses of heterometallic chalcogenolate complexes.  相似文献   

14.
吴思忠  陆世维 《中国化学》2003,21(4):372-376
The catalytic performance of Ni(η^5-Ind)2 complex in the dimerization of propylene was studied in combimation with an organoaluminum co-catalyst,eventually in the presence of a phosphine ligand.The effects of the type of aluminum co-catalyst and its relative amount,the nature of phosphine ligand and P/Ni ratio as well as the reaction temperature were examined.The results indicated that the nickel precatalyst exhibited high productivity for the propylene dimerization together with organoaluminum.It was likely to strongly modify the reactivity in the catalytic sytem when using phosphine ligand as additives,especially at the reaction temperature below 0℃.The catalytic system based on Ni(η^5-Ind)2 complex displaed an extremely high productivity(TOF up to 16900h^-1)and a good regioselectivity to 2,3-dimethylbutenes (2,3-DMB) in dimers(66.4%)under proper reaction parameters.  相似文献   

15.
Nitrogenase cofactors can be extracted into an organic solvent to catalyze the reduction of cyanide (CN?), carbon monoxide (CO), and carbon dioxide (CO2) without using adenosine triphosphate (ATP), when samarium(II) iodide (SmI2) and 2,6‐lutidinium triflate (Lut‐H) are employed as a reductant and a proton source, respectively. Driven by SmI2, the cofactors catalytically reduce CN? or CO to C1–C4 hydrocarbons, and CO2 to CO and C1–C3 hydrocarbons. The C? C coupling from CO2 indicates a unique Fischer–Tropsch‐like reaction with an atypical carbonaceous substrate, whereas the catalytic turnover of CN?, CO, and CO2 by isolated cofactors suggests the possibility to develop nitrogenase‐based electrocatalysts for the production of hydrocarbons from these carbon‐containing compounds.  相似文献   

16.
Density functional calculations at the BP86/TZ2P level were carried out to understand the ligand properties of the 16‐valence‐electron(VE) Group 14 complexes [(PMe3)2Cl2M(E)] ( 1ME ) and the 18‐VE Group 14 complexes [(PMe3)2(CO)2M(E)] ( 2ME ; M=Fe, Ru, Os; E=C, Si, Ge, Sn) in complexation with W(CO)5. Calculations were also carried out for the complexes (CO)5W–EO. The complexes [(PMe3)2Cl2M(E)] and [(PMe3)2(CO)2M(E)] bind strongly to W(CO)5 yielding the adducts 1ME–W(CO)5 and 2ME–W(CO)5 , which have C2v equilibrium geometries. The bond strengths of the heavier Group 14 ligands 1ME (E=Si–Sn) are uniformly larger, by about 6–7 kcal mol?1, than those of the respective EO ligand in (CO)5W‐EO, while the carbon complexes 1MC–W(CO)5 have comparable bond dissociation energies (BDE) to CO. The heavier 18‐VE ligands 2ME (E=Si–Sn) are about 23–25 kcal mol?1 more strongly bonded than the associated EO ligand, while the BDE of 2MC is about 17–21 kcal mol?1 larger than that of CO. Analysis of the bonding with an energy‐decomposition scheme reveals that 1ME is isolobal with EO and that the nature of the bonding in 1ME–W(CO)5 is very similar to that in (CO)5W–EO. The ligands 1ME are slightly weaker π acceptors than EO while the π‐acceptor strength of 2ME is even lower.  相似文献   

17.
Four iron(II) carbonyl complexes, fac‐[Fe (CO)3X2(py)] (X = I?, 1 and Br?, 3 ), fac‐[{Fe (CO)3X2}2(bipy)] (X = I?, 2 and Br?, 4 ), were facilely synthesized by reacting cis‐[Fe (CO)4X2] (X = I?, Br?) with pyridine (py) and 4,4′‐dipyridine (bipy) ligands, respectively, in good yields (70%~85%). These complexes were fully characterized, and the structures of Complexes 2 and 3 were crystallographically analyzed. In dimethyl sulfoxide, they decomposed rapidly to release carbon monoxide (CO), and in methanol, they showed better stability which allowed kinetically analyzing their decomposing behaviors. The self‐decomposing in methanol fitted first‐order kinetics with a half‐time ranging from several minutes to 1 h. Our results suggested that the ligand with great conjugation (bipy) and strong electron‐donating capability (iodide) could stabilize the iron(II) carbonyl complexes. The decomposition of the iodo complexes ( 1 and 2 ) involved the production of iodine radicals. MTT (3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyl tetrazolium bromide) assessments revealed that the efficacy against human bladder carcinoma cell line (RT112) is in the following trend: 1 > 2 > 3 > 4 . The relatively strong efficacy of Complexes 1 and 2 is mainly contributed to the in situ generated iodine radicals. The combination of the cytotoxicity of the in situ generated radicals with the anticancer activity of CO as reported in literatures may lead to developing novel anticancer drugs with enhanced efficacy.  相似文献   

18.
Self‐assembled, hexarhenium(I), triangular metalloprism compound [{(CO)3Re(μ‐ 2 )Re(CO)3}33‐ 1 )2] ( 3 ) featuring three bis‐chelating pillarlike indigo dianions (μ‐ 2 ), each of which connects two fac‐Re(CO)3 cores, which are interconnected by a tritopic N donor, that is, a 2,4,6‐tris(4‐pyridyl)‐1,3,5‐triazine (μ3‐ 1 , tPyTz) ligand, has been synthesized in high yield and characterized. Metalloprism 3 exhibits a strong absorption in the near‐infrared (NIR) region. The reversible, multielectron redox properties of the electrogenerated 3 n species, where n=3+, 0, 3?, 4?, 5?, 8?, in the visible and especially in the NIR region were investigated in THF solution by cyclic voltammetry (CV), chronocoulometry, EPR spectroscopy, and thin‐layer UV/Vis/NIR spectroelectrochemistry (SEC). Stepwise, site‐specific electrochemical reductions lead to the formation of a series of highly stable ion (radical) species in which electrons associated with μ‐ 2 or μ3‐ 1 components of the molecule can be clearly distinguished. An EPR investigation revealed interaction of unpaired electrons with the metal nuclei (185,187Re, I=5/2) in the reduced intermediates. The framework has C2 symmetry, and accidental degeneracies suffice. Detailed theoretical calculations by structure‐based DFT confirm that the triply degenerate HOMO has ≥70 % indigo character with a sizable dπ‐Re character, while the LUMO is dominated by the triply degenerate indigo ligands, and the LUMO+1 by doubly degenerate tPyTz ligands. A comparison of 3 and previously reported 2,2′‐bis‐benzimidazolate‐ (BiBzlm) or alkoxy‐pillared ReI metalloprisms indicates a very low switching potential with a potential window of less than 1 V and reversibly accessible optical properties with higher stability of the intermediates. The properties exhibited by 3 appear to be due to the slight tuning of the bridging ligand from N,N? to N,O?.  相似文献   

19.
The co‐adsorption of O2 and CO on anionic sites of gold species is considered as a crucial step in the catalytic CO oxidation on gold catalysts. In this regard, the [Au2O2(CO)n]? (n=2–6) complexes were prepared by using a laser vaporization supersonic ion source and were studied by using infrared photodissociation spectroscopy in the gas phase. All the [Au2O2(CO)n]? (n=2–6) complexes were characterized to have a core structure involving one CO and one O2 molecule co‐adsorbed on Au2? with the other CO molecules physically tagged around. The CO stretching frequency of the [Au2O2(CO)]? core ion is observed around =2032–2042 cm?1, which is about 200 cm?1 higher than that in [Au2(CO)2]?. This frequency difference and the analyses based on density functional calculations provide direct evidence for the synergy effect of the chemically adsorbed O2 and CO. The low lying structures with carbonate group were not observed experimentally because of high formation barriers. The structures and the stability (i.e., the inertness in a sense) of the co‐adsorbed O2 and CO on Au2? may have relevance to the elementary reaction steps on real gold catalysts.  相似文献   

20.
We demonstrate a unique synthetic route for oxygen‐deficient mesoporous TiOx by a redox–transmetalation process by using Zn metal as the reducing agent. The as‐obtained materials have significantly enhanced electronic conductivity; 20 times higher than that of as‐synthesized TiO2 material. Moreover, electrochemical impedance spectroscopy (EIS) and galvanostatic intermittent titration technique (GITT) measurements are performed to validate the low charge carrier resistance of the oxygen‐deficient TiOx. The resulting oxygen‐deficient TiOx battery anode exhibits a high reversible capacity (~180 mA h g?1 at a discharge/charge rate of 1 C/1 C after 400 cycles) and an excellent rate capability (~90 mA h g?1 even at a rate of 10 C). Also, the full cell, which is coupled with a LiCoO2 cathode material, exhibits an outstanding rate capability (>75 mA h g?1 at a rate of 3.0 C) and maintains a reversible capacity of over 100 mA h g?1 at a discharge/charge of 1 C/1 C for 300 cycles.  相似文献   

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