New insights from the nano world.
The mechanism for binding oxygen to metalloporphyrins is a vital process for oxygen-breathing organisms. Understanding how small gas molecules are chemically bound to the metal complex is also important in catalysis or the implementation of chemical sensors. When investigating these binding mechanisms, scientists use porphyrin rings with a central cobalt or iron atom. They coat a copper or silver support surface with these substances.
An important characteristic of porphyrins is their conformational flexibility. Recent research has shown that each specific geometric configuration of the metalloporphyrins has a distinct influence on their functionality. In line with the current state of research, the scientists expected only a single CO molecule to bind axially to the central metallic atom. However, detailed scanning tunnel microscopy experiments by Knud Seifert revealed that, in fact, two gas molecules dock between the central metallic atom and the two opposite nitrogen atoms. Decisive is the saddle shape of the porphyrin molecules, in which the gas molecules assume the position of the rider.
The significance of the saddle geometry became apparent in model calculations done by Marie-Laure Bocquet from the University of Lyon.
The research was funded by the Deutsche Forschungsgemeinschaft (Cluster of Excellence "Munich Center for Advanced Photonics"), the TUM Institute for Advanced Study, the European Research Council (ERC Advanced Grant MolArt), as well as the Spanish Ministerio de Ciencia E Innovacion. The Leibniz Rechenzentrum of the Bayerische Akademie der Wissenschaften provided computing time. The research group of Professor Barth is member of the Catalysis Research Center (CRC) of the TUM.
Cis-dicarbonyl binding at cobalt and iron porphyrins with saddle-shape conformation, Knud Seufert, Marie-Laure Bocquet, Willi Auwärter, Alexander Weber-Bargioni, Joachim Reichert, Nicolás Lorente und Johannes V. Barth, Nature Chemistry, Online 9. January 2011 – DOI: 10.1038/NCHEM.956 Link: www.nature.com/nchem/journal/vaop/ncurrent/full/
Further publications on this topic:
Discriminative Response of Surface-Confined Metalloporphyrin Molecules to Carbon and Nitrogen Monoxide, Knud Seufert, Willi Auwaerter und Johannes V. Barth, Journal of the American Chemical Society, 2010, 132, 18141� – DOI: 10.1021/ja1054884 Link: pubs.acs.org/doi/abs/10.1021/
Contact: Dr. Andreas Battenberg email@example.com 49-892-891-0510 Technische Universitaet Muenchen