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A Dicobalt Complex with an Unsymmetrical Quinonoid Bridge Isolated in Three Units of Charge: A Combined Structural, (Spectro)electrochemical,Magnetic and Spectroscopic Study 下载免费PDF全文
Margarethe van der Meer Yvonne Rechkemmer Uta Frank Frauke D. Breitgoff Dr. Stephan Hohloch Prof. Dr. Cheng‐Yong Su Dr. Petr Neugebauer Raphael Marx María Dörfel Prof. Dr. Joris van Slageren Prof. Dr. Biprajit Sarkar 《Chemistry (Weinheim an der Bergstrasse, Germany)》2016,22(39):13884-13893
Quinonoid ligands are excellent bridges for generating redox‐rich dinuclear assemblies. A large majority of these bridges are symmetrically substituted, with examples of unsymmetrically substituted quinonoid bridges being extremely rare. We present here a dicobalt complex in its various redox states with an unsymmetrically substituted quinonoid bridging ligand. Two homovalent forms and one mixed‐valent form have been isolated and characterized by single crystal X‐ray diffraction. The complex displays a large comproportionation constant for the mixed‐valent state which is three orders of magnitude higher than that observed for the analogous complex with a symmetrically substituted bridge. Results from electrochemistry, UV/Vis/NIR spectroelectrochemistry, SQUID magnetometry, multi‐frequency EPR spectroscopy and FIR spectroscopy are used to probe the electronic structures of these complexes. FIR provides direct evidence of exchange coupling. The results presented here display the advantages of using an unsymmetrically substituted bridge: site specific redox chemistry, high thermodynamic stabilization of the mixed‐valent form, isolation and crystallization of various redox forms of the complex. This work represents an important step on the way to generating heterodinuclear complexes for use in cooperative catalysis. 相似文献
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Tailoring RuII Pyridine/Triazole Oxygenation Catalysts and Using Photoreactivity to Probe their Electronic Properties 下载免费PDF全文
Fritz Weisser Hendrik Stevens Johannes Klein Margarethe van der Meer Dr. Stephan Hohloch Prof. Dr. Biprajit Sarkar 《Chemistry (Weinheim an der Bergstrasse, Germany)》2015,21(24):8926-8938
Tuning of ligand properties is at the heart of influencing chemical reactivity and generating tailor‐made catalysts. Herein, three series of complexes [Ru(L)(Cl)(X)]PF6 (X=DMSO, PPh3, or CD3CN) with tripodal ligands (L1–L5) containing pyridine and triazole arms are presented. Triazole‐for‐pyridine substitution and the substituent at the triazole systematically influence the redox behavior and photoreactivity of the complexes. The mechanism of the light‐driven ligand exchange of the DMSO complexes in CD3CN could be elucidated, and two seven‐coordinate intermediates were identified. Finally, tuning of the ligand framework was applied to the catalytic oxygenation of alkanes, for which the DMSO complexes were the best catalysts and the yield improved with increasing number of triazole arms. These results thus show how click‐derived ligands can be tuned on demand for catalytic processes. 相似文献
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Electrocatalytic Dihydrogen Production with a Robust Mesoionic Pyridylcarbene Cobalt Catalyst 下载免费PDF全文
Margarethe van der Meer Estelle Glais Dr. Inke Siewert Prof. Dr. Biprajit Sarkar 《Angewandte Chemie (International ed. in English)》2015,54(46):13792-13795
A CoIII complex with a mesoionic pyridylcarbene ligand is presented. This complex is an efficient electrocatalyst for H2 production at very low overpotential and high turnovers when using a (glassy carbon) GC electrode. The corresponding triazole complexes display no catalytic activity whatsoever under identical conditions. The remarkable robustness of the Co? C(carbene) bond towards acids is likely responsible for the high efficiency of this catalyst. The present results thus open new avenues for carbene‐based ligands for generating functional models for hydrogenases. 相似文献
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Ohne ZusammenfassungZum Schlusse erlauben wir uns, Herrn Dr. K. Hlawatsch für die Ausführung der im vorstehenden mitgetheilten krystallographischen Untersuchungen unseren besten Dank zu sagen. 相似文献
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Einar Biilmann I. Krarup F. Auerbach E. Smolczyk S. Bodforss H. Lund G. E. Cullen N. Bjerrum S. P. L. Sørensen Margarethe Sørensen K. Linderstrøm-Lang J. H. Blom E. Langseth Jensen E. Schreiner L. Ebert St. Veibel H. Baggesgaard-Rasmussen S. A. Schou S. Tovberg-Jensen Vera Lester O. M. Henriques R. Schaefer F. Schmidt E. Mislowitzer C. W. G Hetterschy J. Hudig R. Shoji W. Sturm P. F. Sharp F. H. Mac Dougall 《Analytical and bioanalytical chemistry》1931,83(1-2):45-59