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121.
Bartholomus Pieber Jamal A. Malik Cristian Cavedon Sebastian Gisbertz Aleksandr Savateev Daniel Cruz Tobias Heil Guigang Zhang Peter H. Seeberger 《Angewandte Chemie (International ed. in English)》2019,58(28):9575-9580
Cross‐coupling reactions mediated by dual nickel/photocatalysis are synthetically attractive but rely mainly on expensive, non‐recyclable noble‐metal complexes as photocatalysts. Heterogeneous semiconductors, which are commonly used for artificial photosynthesis and wastewater treatment, are a sustainable alternative. Graphitic carbon nitrides, a class of metal‐free polymers that can be easily prepared from bulk chemicals, are heterogeneous semiconductors with high potential for photocatalytic organic transformations. Here, we demonstrate that graphitic carbon nitrides in combination with nickel catalysis can induce selective C?O cross‐couplings of carboxylic acids with aryl halides, yielding the respective aryl esters in excellent yield and selectivity. The heterogeneous organic photocatalyst exhibits a broad substrate scope, is able to harvest green light, and can be recycled multiple times. In situ FTIR was used to track the reaction progress to study this transformation at different irradiation wavelengths and reaction scales. 相似文献
122.
Jindong Ren Marvin Cnudde Dana Brünink Stefan Buss Constantin G. Daniliuc Lacheng Liu Harald Fuchs Cristian A. Strassert Hong‐Ying Gao Nikos L. Doltsinis 《Angewandte Chemie (International ed. in English)》2019,58(43):15396-15400
A series of Pt(II) complexes with tetradentate luminophores has been designed, synthesized, and deposited on coinage metal surfaces with the aim to produce highly planar self‐assembled monolayers. Low‐temperature scanning tunneling microscopy (STM) and density functional theory (DFT) calculations reveal a significant initial nonplanarity for all complexes. A subsequent metal‐catalyzed separation of the nonplanar moiety at the bridging unit via the scission of a C?N bond is observed, leaving behind a largely planar core complex. The activation barrier of this bond scission process is found to depend strongly on the chemical nature of both bridging group and coordination plane, and to increase from Cu(111) through Ag(111) to Au(111). 相似文献
123.
Arturo Quirantes Francisco J. Olmo Hassan Lyamani Lucas Alados-Arboledas 《Journal of Quantitative Spectroscopy & Radiative Transfer》2008,109(8):1496-1503
Total aerosol scattering and backscattering atmospheric values are typically obtained with an integrating nephelometer. Due to design limitations, measurements do not cover the full (0°–180°) angular range, and correction factors are necessary. The effect of angle cutoff is examined for a number of particle size distributions and refractive indices. Scattering data for sub-micron particles can be corrected by the use of a modified Anderson approximation, while data for larger particle distributions can be approximated by a function of the effective size parameter. Correction factors for the hemispheric backscatter ratio are found to be small if nonsphericity is assumed. Such approximations will help more accurate corrections for angle range, particularly at large size parameter values. 相似文献
124.
Dr. Jose Ángel Pino‐Chamorro Dr. Artem L. Gushchin Prof. M. Jesús Fernández‐Trujillo Dr. Rita Hernández‐Molina Dr. Cristian Vicent Dr. Andrés G. Algarra Prof. Manuel G. Basallote 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(7):2835-2844
A study, involving kinetic measurements on the stopped‐flow and conventional UV/Vis timescales, ESI‐MS, NMR spectroscopy and DFT calculations, has been carried out to understand the mechanism of the reaction of [Mo3S4(acac)3(py)3][PF6] ([ 1 ]PF6; acac=acetylacetonate, py=pyridine) with two RC?CR alkynes (R=CH2OH (btd), COOH (adc)) in CH3CN. Both reactions show polyphasic kinetics, but experimental and computational data indicate that alkyne activation occurs in a single kinetic step through a concerted mechanism similar to that of organic [3+2] cycloaddition reactions, in this case through the interaction with one Mo(μ‐S)2 moiety of [ 1 ]+. The rate of this step is three orders of magnitude faster for adc than that for btd, and the products initially formed evolve in subsequent steps into compounds that result from substitution of py ligands or from reorganization to give species with different structures. Activation strain analysis of the [3+2] cycloaddition step reveals that the deformation of the two reactants has a small contribution to the difference in the computed activation barriers, which is mainly associated with the change in the extent of their interaction at the transition‐state structures. Subsequent frontier molecular orbital analysis shows that the carboxylic acid substituents on adc stabilize its HOMO and LUMO orbitals with respect to those on btd due to better electron‐withdrawing properties. As a result, the frontier molecular orbitals of the cluster and alkyne become closer in energy; this allows a stronger interaction. 相似文献
125.
Cristian Rosso Dr. Giacomo Filippini Prof. Maurizio Prato 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(70):16032-16036
The use of amine-rich N-doped carbon nanodots (NCNDs) for the photochemical radical perfluoroalkylation of organic compounds is reported. This operationally simple approach occurs under mild conditions producing valuable new C−C bonds. The chemistry is driven by the ability of NCNDs to directly reach an electronically excited state upon light absorption, thereby successively triggering the formation of reactive radical species from simple perfluoroalkyl iodides. Preliminary mechanistic studies are also reported. 相似文献
126.
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129.
New Perspectives for Old Clusters: Anderson–Evans Anions as Building Blocks of Large Polyoxometalate Frameworks in a Series of Heterometallic 3 d–4 f Species 下载免费PDF全文
Dr. Beñat Artetxe Dr. Santiago Reinoso Dr. Leire San Felices Prof. Luis Lezama Prof. Juan M. Gutiérrez‐Zorrilla Dr. Cristian Vicent Fadi Haso Prof. Tianbo Liu 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(13):4616-4625
A series of nine [Sb7W36O133Ln3M2(OAc)(H2O)8]17? heterometallic anions ( Ln3M2 ; Ln=La–Gd, M=Co; Ln=Ce, M=Ni and Zn) have been obtained by reacting 3 d metal disubstituted Krebs‐type tungstoantimonates(III) with early lanthanides. Their unique tetrameric structure contains a novel {MW9O33} capping unit formed by a planar {MW6O24} fragment to which three {WO2} groups are condensed to form a tungstate skeleton identical to that of a hypothetical trilacunary derivative of the ?‐Keggin cluster. It is shown, for the first time, that classical Anderson–Evans {MW6O24} anions can act as building blocks to construct purely inorganic large frameworks. Unprecedented reactivity in the outer ring of these disk‐shaped species is also revealed. The Ln3M2 anions possess chirality owing to a {Sb4O4} cluster being encapsulated in left‐ or right‐handed orientations. Their ability to self‐associate in blackberry‐type vesicles in solution has been assessed for the Ce3Co2 derivative. 相似文献
130.
Corrigendum: Labeling and Selective Inactivation of Gram‐Positive Bacteria Employing Bimodal Photoprobes with Dual Readouts 下载免费PDF全文
Dr. Anzhela Galstyan Dr. Desiree Block Dr. Silke Niemann Dr. Malte C. Grüner Prof.Dr. Stefania Abbruzzetti Michele Oneto Dr. Constantin G. Daniliuc Dr. Sven Hermann Prof.Dr. Cristiano Viappiani Prof.Dr. Michael Schäfers Prof.Dr. Bettina Löffler Priv.‐Doz.Dr. Cristian A. Strassert Dr. Andreas Faust 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(27):9051-9051