- Electrochemical CO2 Reduction-The Effect of Chalcogenide Exchange in Ni-Isocyclam Complexes
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Among the numerous homogeneous electrochemical CO2 reduction catalysts, [Ni(cyclam)]2+ is known as one of the most potent catalysts. Likewise, [Ni(isocyclam)]2+ was reported to enable electrochemical CO2 conversion but has received significantly less attention. However, for both catalysts, a purposeful substitution of a single nitrogen donor group by chalcogen atoms was never reported. In this work, we report a series of isocyclam-based Ni complexes with {ON3}, {SN3}, {SeN3}, and {N4} moieties and investigated the influence of nitrogen/chalcogen substitution on electrochemical CO2 reduction. While [Ni(isocyclam)]2+ showed the highest selectivity toward CO2 reduction within this series with a Faradaic efficiency of 86% for the generation of CO at an overpotential of-1.20 V and acts as a homogeneous catalyst, the O-and S-containing Ni complexes revealed comparable catalytic activities at ca. 0.3 V milder overpotential but tend to form deposits on the electrode, acting as precursors for a heterogeneous catalysis. Moreover, the heterogeneous species generated from the O-and S-containing complexes enable a catalytic hydride transfer to acetonitrile, resulting in the generation of acetaldehyde. The incorporation of selenium, however, resulted in loss of CO2 reduction activity, mainly leading to hydrogen generation that is also catalyzed by a heterogeneous electrodeposit.
- Apfel, Ulf-Peter,Battistella, Beatrice,Gerschel, Philipp,Ray, Kallol,Siegmund, Daniel
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- NEW 6-OXA-3,9, 15-TRIAZA-BICYCLO[9.3.1 ]PENTADEC A- 1 ( 14), 1 1 ( 15), 12-TRIENE DERIVATIVES BASED COMPOUNDS AND THEIR APPLICATION AS LIGANDS OF ESSENTIAL METAL ION BASED MRI AND 52MN BASED PET CONTRAST AGENTS
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The one subject of the invention is the compounds of general formula (I), their isomers, their physiologically acceptable salts and/or Mn(ll), Fe(ll), Fe(lll), Co(ll) and Ni(ll) complexes and their application: where R1| = - OH or -NR 3/s
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Page/Page column 4; 5
(2017/07/11)
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- "Bidentate" and "tridentate" sulfonamide ligands for titanium complexes: Crystal structures and solution dynamics elucidating an η2 or η3-coordination mode
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Highly air- and moisture-sensitive complexes having sulfonamide ligands, (TsNR)2Ti(NMe2)2 (Ts = p-MeC6H4SO2), were prepared by treatment of two equivalents of TsNHR with Ti(NMe2)4 at room temperature. One of the compounds, where R = i-Pr (1), was studied in detail; the crystal structure of 1 revealed that both of the TsNi-Pr ligands were bound to the metal in an η2-coordination mode. Solution dynamics of 1 showed that an η1/η2 interconversion occurred above 60°C with an activation energy of 15.8 kcal mol-1. Treatment of Ti(NMe2)4 with the sulfonamide TsHN(CH2)2O(CH2)2NHTs (3), led to the formation of [TsN(CH2)2O(CH2)2NTs]Ti(NMe 2)2 (2) in high yield, in which the sulfonamide moiety was coordinated to the titanium center in an η3 (NON) mode. No sign of η1/η2 interconversion of the sulfonamide ligands was seen in solution. Treatment of 2 with Me3SiCl resulted in the formation of [{TsN(CH2)2O(CH2)2NTs}Ti(NMe 2)Cl]2 (4) and [{TsN(CH2)2O(CH2)2NTs}TiCl 2]2 (5). An X-ray structure determination of 4 revealed that sulfonyl oxygen bridging resulted in the formation of an eight membered ring.
- Hamura, Satoshi,Oda, Takashi,Shimizu, Yasuaki,Matsubara, Kouki,Nagashima, Hideo
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p. 1521 - 1527
(2007/10/03)
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- Design and synthesis of macrocyclic ligands for specific interaction with crystalline ettringite and demonstration of a viable mechanism for the setting of cement
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Cementitious materials are among those most widely used by mankind while being among the least well understood. The detailed physicochemical processes involved in the hydration and setting of cement slurries are very complex, and a clearly defined quantitative account is still lacking: indeed, even the composition of the cement powder itself is not known exactly. Still less has there been any understanding of the mechanism by which numerous known retarders of the cement setting process act. In this article, we detail the synthesis of novel macrocyclic organophosphonate retarders 1a and 2a which were developed by rational methods. Attempts to synthesise these compounds as phosphonate ester derivatives were universally unsuccessful, however direct modification of the parent hexaaza-(3) and trioxatriaza-18-crown-6 (5) derivatives was successful, to provide the phosphonic acids 1b and 2b respectively. Subsequent testing of these compounds showed their ability to inhibit the growth of crystalline ettringite and delay the setting of cement. These results support the hypothesis that the formation of crystalline ettringite is the rate determining step in the setting of cement.
- Griffin, Jonathan L. W.,Coveney, Peter V.,Whiting, Andrew,Davey, Roger
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p. 1973 - 1981
(2007/10/03)
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- MACROHETEROCYCES. XXXVI. A CONVENIENT METHOD FOR SYNTHESIS OF DI- AND POLYAZACROWN ETHERS
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A method is proposed for the production of di- and polyazacrown ethers by the condensation of bissulfonamides with dibromides or ditosyloxy derivatives in a two-phase aqueous alkali-toluene (benzene) system.The optimum concentration range for the substrate and the alkylating agent is 0.017-0.1 M.The catalytic activity of the quaternary ammonium salts decreases in the order (Bu)4NI > (Bu4)NBr > (Bu4)NCl > (Bu4)NHSO4 > (C2H5)3C6H5CH2NCl >> (Et)4NI > (Et)4NBr.The highest yields of te 12-membered azacrown ethers are obtained in the presence of lithium hyroxide, and the largest yields of the crown ethers with larger ring sizes are obtained in the presence of sodium or potassium hydroxide, and this is probably due to the matrix effects of the cation.
- Luk'yanenko, N.G.,Basok, S.S.,Filonova, L.K.
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p. 1562 - 1571
(2007/10/02)
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