Versatile Coordination of Azocarboxamides: Redox‐Triggered Change of the Chelating Binding Pocket in Ruthenium Complexes. Issue 68 (8th November 2018)

• Record Type: Journal Article
• Authors: Klein, Johannes; Beerhues, Julia; Schweinfurth, David; van der Meer, Margarethe; Gazvoda, Martin; Lahiri, Goutam Kumar; Košmrlj, Janez; Sarkar, Biprajit
• Is Part Of: Chemistry. Volume 24:Issue 68(2018)
• Page Start: 18020
• Page End: 18031
• Publication Date: 2018-11-08
• Subjects: bridging ligands -- chelates -- coordination modes -- electrochemistry -- ruthenium; Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201803606
• Languages: English
• ISSNs: 0947-6539

Abstract

Abstract: Azocarboxamides occupy a special place among azo ligands owing to their versatility for metal coordination. Herein ruthenium complexes with two different azocarboxamide ligands that differ in the presence (or not) of a coordinating pyridyl heterocycle are presented. By making full use of the O, N(amide), N(azo), and N(pyridyl) coordinating sites, the first diruthenium complex that is bridged by an azo ligand containing two different binding pockets was obtained. Moreover, it was conclusively proven that, in the mononuclear complexes, oxidation at the ruthenium center leads to a complete change of coordination at the chelating binding pocket. The complexes were characterized by NMR spectroscopy, mass spectrometry, and single‐crystal X‐ray diffraction. Additionally, the mechanism of the aforementioned redox‐triggered change in the chelating binding pocket and the electronic structures of all the complexes were investigated by a combination of electrochemistry, UV/Vis/NIR/EPR spectroelectrochemistry, and DFT calculations. This is first instance in which a redox‐driven change in the complete chelating binding pocket has been observed in a ruthenium complex as well as with azo‐based ligands. These results thus show the potential of these versatile azocarboxamide ligands to act as redox‐driven switches with possible relevance to electrocatalysis. Abstract : Join at the tip : Ruthenium complexes of azocarboxamide ligands with and without a coordinating pyridyl heterocycle were synthesized. By making full use of the O, N(amide), N(azo), and N(pyridyl) coordinating sites, the first diruthenium complex bridged by an azo ligand containing two different binding pockets was obtained. Moreover, in the mononuclear complexes, oxidation at the Ru center leads to a change in the coordination mode at the chelating binding pocket (see scheme).