RESUMEN
An aerobic copper-catalyzed oxysulfonylation of vinylarenes with sodium sulfinates is described. This protocol features mild reaction conditions, convenient operation, and broad substrate scope with respect to vinylarenes and sodium sulfinates. Notably, the protocol demonstrates excellent tolerance of functional groups such as chloro, bromo, ester, cyano, and nitro groups. Mechanistic investigations indicated that the reaction should undergo radical cascades involving a sulfonyl radical generated from sodium sulfinate with air as the terminal oxidant, addition across alkene to deliver a benzylic radical, and subsequent cross-coupling with air.
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A nickel-catalyzed direct sulfonylation of alkenes with sulfonyl chlorides has been developed using 1,10-phenanthroline-5,6-dione as the ligand. Unactivated alkenes and styrenes including 1,1-, 1,2-disubstituted alkenes can be subjected to the protocol, and a wide range of vinyl sulfones was obtained in high to excellent yields with good functional group compatibility. Notably, the process did not allow the desulfonylation of sulfonyl chloride or chlorosulfonylation of alkenes. Radical-trapping experiment supported that a sulfonyl free-radical was likely produced and triggered subsequent transformation in the process.
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A metal-free selective ortho-C-H amidation of aryl iodines(III) with the use of N-methoxy amides as aminating reagents under mild conditions is described here. In the protocol, excellent chemoselectivity and high regioselectivity were obtained. Notably, the iodine substituent rendered the amidation product suitable to be used for further elaboration.
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Intricate superstructures possess unusual structural features and promising applications. The preparation of superstructures with single-crystalline nature are conducive to understanding the structure-property relationship, however, remains an intriguing challenge. Herein we put forward a new hierarchical assembly strategy towards rational and precise construction of intricate single-crystal superstructures. Firstly, two unprecedented superclusters in Rubik's cube's form with a size of ≈2×2×2â nm3 are constructed by aggregation of eight {Pr4 Sb12 } oxohalide clusters as secondary building units (SBUs). Then, the Rubik's cubes further act as isolable tertiary building units (TBUs) to assemble diversified single-crystal superstructures. Importantly, intermediate assembly states are captured, which helps illustrate the evolution of TBU-based superstructures and thus provides a profound understanding of the assembly process of superstructures at the atomic level.
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An acyl lactonization of alkenes with aldehydes under visible-light photoredox catalysis is described. With the protocol, a broad scope of alkenoic acids and aldehydes could be compatible and good functional group tolerance is obtained. A series of acyl lactones are obtained with isolated yields ranging from 50-95%. Mechanistic studies revealed that the transformation should proceed via a radical chain process.
Asunto(s)
Aldehídos , Alquenos , Lactonas , Estructura Molecular , CatálisisRESUMEN
A copper-catalyzed intermolecular electrophilic amination of benzamides with O-benzoyl hydroxylamines was achieved with the assistance of an 8-aminoquinolyl group. With this protocol, good compatibility was observed for a variety of aryl amides and heteroaryl amides, and excellent tolerance with various functional groups was achieved. Significantly, the monoaminated product was overwhelmingly delivered under the simple reaction conditions. Preliminary mechanistic investigations suggested that a radical pathway should be excluded and C-H activation be potentially the rate-determining step.
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A visible-light photoredox-catalyzed sulfonyl lactonization of unsaturated carboxylic acids with sulfonyl chlorides is described. This reaction features good functional group tolerance and a broad substrate scope, providing a simple and efficient protocol to access a wide range of sulfonyl lactones in high to excellent yields. Preliminary mechanistic investigations suggested that a free-radical pathway should be involved in the process.
Asunto(s)
Cloruros , Lactonas , Ácidos Carboxílicos , Catálisis , LuzRESUMEN
An organo-templated titanium-oxo sulfate of the formulation (H2nep)[TiO(SO4)2] (denoted as TiOS, nep = N-ethylpiperazine) was synthesized under solvent-free conditions. The framework of TiOS is assembled from the [TiO(SO4)2]n2n- infinite chains interconnected by the H2nep cations through H-bond networks. After thermal treatment under vacuum conditions, the organic template H2nep was partially decomposed and converted into N-doped carbon dots (N-CDs), resulting in the N-CDs@TiOS composite material with retained crystallinity of the parent TiOS. The thermolysis of organic templates generates meso-cavities in the framework, rendering N-CDs@TiOS with a mesoporous structure. Photoelectrochemical and photocatalytic experiments show that the presence of N-CDs substantially improved visible-light-driven photocatalytic activity of N-CDs@TiOS compared to that of TiOS. The template thermolysis strategy gives an effective approach to construct the CDs-sensitized Ti-based mesoporous open-framework materials for visible-light photocatalytic applications.
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The metal-to-core charge transfer (MCCT) transition in sensitized titanium-oxo clusters is an important process for photoinduced electron injection in photovoltaic conversion. This process resembles most closely the Type II photoinjection in dye-sensitized solar cells. Herein we report the synthesis and photophysical and photoelectrochemical (PEC) properties of the phosphonate-stabilized titanium-oxo clusters containing the ferrocenecarboxylate ligands. These ferrocene-containing clusters exhibit intense visible absorption extended up to 600 nm along with low optical band gaps of â¼2.2 eV. The low-energy transitions of these clusters were systematically investigated by UV-vis spectroscopy and DFT/TDDFT calculations. The combined experimental and computational studies suggest that the ferrocenecarboxylate-substituted titanium-oxo clusters form a donor-acceptor (D-A) system. The low-energy transition of these clusters primarily involves the MCCT from the iron center to TiO cluster core. The TiO core structure and phosphonate ligands both have great influence on the PEC properties of the clusters. This work provides valuable examples for the sensitized titanium-oxo clusters in which electron injection takes place via MCCT transition.
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A new chalcogenide crystal, (NH4)4Ag12Sn7Se22 (FJSM-STS), has been solvothermally synthesized. The crystal structure, which is composed of arrays of [Sn3Se9]n(6n-) chains interconnecting [SnAg6Se10]n(10n-) and [Ag3Se4]n(5n-) layers, is unprecedented among the reported A/Ag/Sn/Q (A = cation; Q = S, Se, and Te) compounds. Optical absorption together with theoretical calculations of the band structure indicate a direct band gap of 1.21 eV for FJSM-STS, which is close to the ideal band gap to maximize the photoconversion efficiency proposed by Shockley and Queisser. The toxic-metal-free crystal of FJSM-STS exhibits obvious photosensitivity in the near-infrared range. The variates of power and temperature on the photosensitivity have been studied.
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A 3D organic-inorganic hybrid compound, (2-MepyH)3[{Fe(1,10-phen)3}3][{Pr4Sb12O18(OH)Cl(11.5)}(TDC)(4.5)({Pr4Sb12O18(OH)Cl(9.5)} Cl)]·3(2-Mepy)·28H2O (1; 2-Mepy=2-methylpyridine, 1,10-phen=1,10-phenanthroline, H2TDC=thiophene-2,5-dicarboxylic acid), was hydrothermally synthesized and structurally characterized. Unusually, two kinds of high-nuclearity clusters, namely [(Pr4Sb12O18(OH)Cl11)(COO)5](5-) and [(Pr4Sb12O18(OH)Cl9)Cl(COO)5](4-), coexist in the structure of compound 1; two of the latter clusters are doubly bridged by two µ2-Cl(-) moieties to form a new centrosymmetric dimeric cluster. An unprecedented spontaneous and reversible single-crystal-to-single-crystal transformation was observed, which simultaneously involved a notable organic-ligand movement between the metal ions and an alteration of the bridging ion in the dimeric cluster, induced by guest-release/re-adsorption, thereby giving rise to the interconversion between compound 1 and the compound (2-MepyH)3[{Fe(1,10-phen)3}3][{Pr4Sb12O18(OH)Cl(11.5)}(TDC)4({Pr4Sb12O18Cl(10.5)(TDC)(0.5)(H2O)(1.5)}O(0.5))]·25H2O (1'). The mechanism of this transformation has also been discussed in great detail. Photocatalytic H2-evolution activity was observed for compound 1' under UV light with Pt as a co-catalyst and MeOH as a sacrificial electron donor.
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A novel thioantimonate(III), namely, [Ni(phen)(3)](2)Sb(18)S(29) (1; phen = 1,10-phenanthroline), has been solvothermally synthesized. Its structure features a three-dimensional framework with the largest channels in thioantimonates. The chiral [Ni(phen)(3)](2+) cations and the Sb:S ratio (1:1.611) in 1 are unique among those in the reported thioantimonates. The thermal stability, optical properties, and electric conductivity as well as the theoretical band structure and density of state of 1 have also been studied.
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With the in situ-generated [Pb(MCP)4]2+ (HMCP+ = 1-methyl-4-(carboxyl)pyridinium) or [M(phen)3]2+ (M = Co, Fe and Ni; phen = 1,10-phenanthroline) complexes as structural directing agents and charge-balancing ions, we solvothermally synthesized and structurally characterized four new organic-inorganic hybrid iodoplumbates. Compound K2[Pb(MCP)4]Pb3I10 (1) represents the first K+ and [Pb(MCP)4]2+ co-templated hybrid haloplumbate, and exhibits a curve-like anionic layer of [Pb3I10]n4n-. Compounds [M(phen)3]Pb2I6·CH3CN (M = Co (2), Fe (3) and Ni (4)) have isostructural phases, and feature a one-dimensional (1D) [Pb2I6]n2n- anionic chain characteristic of pyramid-like [PbI5] units. The optical property studies show that compounds 1-4 exhibit semiconductor behaviors with the band gaps of 1.98-2.68 eV. In addition, the title compounds exhibited interesting photoelectrical responsive properties, with the photocurrent density in the order of 1 > 3 > 2 > 4. The thermal stabilities of the title compounds 1-4, as well as the theoretical band structure and density of states (DOS) of compounds 1 and 2 have also been studied.
RESUMEN
Two macrocyclic titanium-oxo clusters, namely, [Ti32(µ3-O)8(µ2-O)8(OCH2CH2O)32(OCH2CH2OH)16(BTA)16]·44H2O (BTA = butyrate) and [Ti32(µ3-O)8(µ2-O)8(OCH2CH2O)32(OCH2CH2OH)16(DMBTA)16(HDMBTA)2]·24H2O (DMBTA = 2,2-dimethylbutyrate) were synthesized and structurally characterized. The framework of the Ti32-oxo macrocycle was cyclically fixed by the double-deprotonated ethylene glycolate ligands, which exhibit an inner cavity of about 1.2 × 1.2 nm. The catalytic properties of the Ti32-oxo macrocycles towards the oxidative desulfurization (ODS) reaction were investigated. The structure-dependent catalytic properties towards oxidative desulfurization were observed for the Ti32-oxo macrocycles functionalized with the different carboxylate ligands.
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A copper-catalyzed direct aminosulfonylation of unactivated alkenes with sodium sulfinates for the efficient synthesis of sulfonylated pyrrolidones is described. This reaction features good functional group tolerance and wide substrate scope, providing an efficient and straightforward protocol to access this kind of pyrrolidones. Moreover, preliminary mechanistic investigations disclosed that a free-radical pathway might be invovled in the process.
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Herein, we report two nanocluster-based compounds built on an unprecedented cluster [Ba13Sb36Cl34O54]8-, which represents the first example of a discrete alkaline earth (AE)-containing oxochloride cluster and the largest Sb-based oxohalide cluster to date; the proton-conducting property of the compounds was investigated.
RESUMEN
A selective O-cyclization of N-methoxy aryl amides with CH2Br2 or 1,2-DCE (1,2-dichloroethane) via palladium-catalyzed C-H activation has been described. New C(sp3)-O and C(sp2)-C(sp3) bonds are forged simultaneously with the assistance of an N-methoxy amide group, and good functional group tolerance in substrates is observed. Preliminary mechanistic investigations show that the process may involve a five-membered palladacycle intermediate.
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Four phenylphosphonate-stabilized titanium-oxo clusters with varying functional ligands, namely, [Ti8(µ3-O)2(µ2-O)2(µ2-OiPr)4(OiPr)8(O3PC6H5)4(cat)2] (cat = catecholate), [Ti8(µ3-O)2(µ2-O)2(µ2-OiPr)4(OiPr)8(O3PC6H5)4(O2C10H6)2] (O2C10H6 = naphthalene-2,3-diolate), [Ti6(µ3-O)2(µ2-O)2(µ2-OiPr)4(OiPr)6(O3PC6H5)2(4-DMAB)2] (4-DMAB = 4-dimethylaminobenzoate), and [Ti6(µ3-O)2(µ2-O)2(µ2-OiPr)4(OiPr)6(O3PC6H5)2(4-CBA)2] (4-CBA = 4-cyanobenzoate) were synthesized and structurally characterized. The introduction of catecholate ligands effectively extended the visible absorption region up to 670 nm and reduced the band gap to 2.1 eV. DFT calculations revealed that the ligand-based energy levels could effectively modify the band structure of titanium-oxo clusters. The ligand-to-core charge transfer (LCCT) transition from the functional ligands to the cluster core is responsible for the low-energy charge transfer states. Photoelectrochemical and photocatalytic experiments show that functional ligands have significant influence on the physicochemical properties of titanium-oxo clusters.
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Hydrothermal treatment of nickel acetate and phosphoric acid aqueous solution followed with a carbothermal reduction assisted phosphorization process using sucrose as the carbon source for the controlled synthesis of NixPy/C was successfully realized for the first time. The critical synthesis factors, including reduction temperature, phosphorus/nickel ratio, pH, and sucrose amount were systematically investigated. Remarkably, the carbon serves as a reducer and plays a determinative role in the transformation of Ni2P2O7 into Ni2P/C. The synthesis strategy is divided into four distinguishable stages: (1) hydrothermal preparation of Ni3(PO4)2·8H2O precursor for stabilizing P sources; (2) dimerization of Ni3(PO4)2·8H2O into more thermal stable Ni2P2O7 amorphous phase along with the generation of NiO; (3) carbothermal reduction and phosphidation of NiO into NixPy (0 ≤ y/x ≤ 0.5); and (4) further phosphidation of mixed-phase NixPy and carbothermal reduction of Ni2P2O7 into single-phase Ni2P. The resultant Ni2P, the highly active phase in electrocatalysis, was applied as counter electrode in a dye-sensitized solar cell (DSSC). The DSSC based on Ni2P with 10.4 wt.% carbon delivers a power conversion efficiency of 9.57%, superior to that of state-of-the-art Pt-based cell (8.12%). The abundant Niδ+ and Pδ- active sites and the metal-like conductivity account for its outstanding catalytic performance.
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Sensitized titanium-oxo clusters (TOCs) have attracted growing interest. However, reports on TOCs incorporated with a metal complex as photosensitizers are still very rare. In the present work, the organometallic complex ferrocene was used as a sensitizer for a titanium-oxo cluster. A ferrocenecarboxylate-substituted titanium-oxo cluster [Ti6(µ3-O)6(OiPr)6(O2CFc)6] (Fc = ferrocenyl) was synthesized and structurally characterized, in which the ferrocene wheel performs as a sensitizer for photocurrent response. For comparison, naphthalene-sensitized titanium-oxo clusters [Ti6(µ3-O)6(OiPr)6(NA)6] (NA = 1-naphthoate) and [Ti6(µ3-O)6(OiPr)6(NAA)6] (NAA = 1-naphthylacetate) with the same {Ti6} core structure were also synthesized. The structures, optical behaviors, electronic states and photoelectrochemical properties of these sensitized {Ti6} clusters were investigated. It is demonstrated that the introduction of ferrocene groups into the titanium-oxo cluster significantly reduces the band gap and enhances the photocurrent response in comparison with the naphthalene-sensitized clusters. The substantially reduced band gap of the ferrocene-sensitized cluster was attributed to the introduction of Fe(ii) d-d transitions and the possible contribution from the Fc â {Ti6} charge transfer. For the naphthalene-sensitized clusters, the better electronic coupling between the dye and the {Ti6} core in the 1-naphthoate (NA) substituted cluster results in higher photoelectrochemical activity.