Efficient Air-Stable Organometallic Low-Molecular-Mass Gelators for Ionic Liquids: Synthesis, Aggregation and Application of Pyridine-Bridged Bis(benzimidazolylidene)-Palladium Complexes

Author(s)

Tao Tu, Xiaoling Bao, Wilfried Assenmacher, Herwig Peterlik, Joerg Daniels, Karl Heinz Dötz

Abstract

Novel pincer-type, pyridine-bridged bis(benzimidazolylidene)-palladium complexes 5-7 were synthesised from cheap commercial precursors under microwave assistance. Although simple in structure, carbene complexes 5a,b are efficient low-molecular-mass metallogelators. They gelate not only a broad variety of protic and aprotic organic solvents, but also different types of customary ionic liquids (such as imidazolium, pyridinium, pyrazolidinium, piperidinium and ammonium salts) at concentrations as low as 0.5 mg mL(-1). The morphologies of the resulting 3D gel networks composed from long and thin fibres were studied by TEM and light microscopy for a selection of organic and ionic liquids. The achiral gelators are able to induce the formation of helical fibres. The thermal stability of the gel samples increases with the gelator concentration as demonstrated by thermo reversible DSC studies. Temperature-dependent NMR and X-ray diffraction studies, as well as comparisons with pincer complex analogues bearing shorter alkyl chains, suggest that the 3D networks responsible for gelation are based on non-covalent interactions, such as pi-stacking, van der Waals interactions, and hydrogen and metal-metal bonding. Ionic liquids and gels obtained from them and 5a,b display comparable high conductivities, which characterises pyridine-bridged bis(benzimidazolylidene)-palladium pincer complexes as air-stable metallo gelators that efficiently immobilise ionic liquids in low gelator concentration indicating-beyond catalysis-their potential applications in electrochemical devices

Organisation(s)

Dynamics of Condensed Systems

External organisation(s)

Rheinische Friedrich-Wilhelms-Universität Bonn

Journal

Chemistry: A European Journal

Volume

15

Pages

1853-1861

No. of pages

9

ISSN

0947-6539

DOI

https://doi.org/10.1002/chem.200802116

Publication date

2009

Peer reviewed

Yes

Austrian Fields of Science 2012

1030 Physics, Astronomy, 103009 Solid state physics, 103008 Experimental physics, 210006 Nanotechnology

Portal url

https://ucrisportal.univie.ac.at/en/publications/efficient-airstable-organometallic-lowmolecularmass-gelators-for-ionic-liquids-synthesis-aggregation-and-application-of-pyridinebridged-bisbenzimidazolylidenepalladium-complexes(696f0b33-3468-4146-9160-c7b12646954c).html