From a range of structurally-diverse carbohydrate and glycoside azides, three distinct families of new carbohydrate-functionalised triazolium salts were prepared, as precursors to triazolylidene N-heterocyclic carbene ligands. Ruthenium-triazolylidene complexes were synthesised and characterised by numerous techniques (spectroscopic, electrochemical, elemental analysis). Catalytic activity was probed for a number of oxidative and reductive transformations. Acetyl-protected carbohydrate-NHC hybrid complexes were deprotected in situ and efficiently performed transfer hydrogenation on a range of ketone substrates. A manuscript describing these results is being prepared for publication.
Control experiments for oxidative catalytic coupling of amines, revealed the unprecedent ability of certain triazolium salts to catalyse this reaction selectively. This catalytic system was probed and a publication on the activity of triazolium salts will be forthcoming.
Iridium-NHC complexes were prepared from functionalization of various carbohydrates with the triazolylidene motif. Catalytic activity of these complexes for direct hydrogenation of ketones and aldehydes under mild aqueous conditions and low hydrogen pressure was determined. Activity was pH-dependent, and unprotected carbohydrate systems out-performed acetyl-protected analogues. These iridium complexes were compatible with physiological media, such as aqueous buffer solutions. Through collaboration with Prof F. Paradisi (Nottingham, UK), the ability of carbohydrate-functionalised Iridium-complexes to interact with glycoside hydrolase was probed. A manuscript on the synthesis, properties and catalytic activity of these iridium complexes is being prepared for publication.
These, and related, iridium-complexes were also employed as catalysts for oxidative dehydrogenation of carbohydrates through a collaboration with Prof J. Mata (Castellón, ES). A publication describing these results is being prepared for publication.
This work has been disseminated chiefly through attendance at conferences, participation in CaRLa Catalysis Winter School (Germany), presenting posters (6) at conferences in Switzerland, Ireland, Netherlands, oral presentation at a major conference (International Conference on Coordination Chemistry in Japan) and at the Catalysis Winter School. Social media (Twitter, LinkedIn, blog) has been used in conjunction with attendance at conferences to share contents of presentations with a wider audience, in addition to explaining the project to visiting researchers, school students and members of the public who visit the Department of Chemistry as part of open days or outreach activities. 4-5 articles are expected to be published in the near future based on results from this project.
