Featured Research

from universities, journals, and other organizations

Direct observation of carbon monoxide binding to metal-porphyrines

Date:
January 10, 2011
Source:
Technische Universitaet Muenchen
Summary:
What makes carbon monoxide so toxic is that it blocks the binding site for oxygen in hemoglobin. This very mechanism, if better understood, could be used to implement sensors to warn against carbon monoxide. Physicists have taken an important step by deciphering the mechanisms for binding of gas molecules to iron and cobalt porphyrins.

A scanning tunneling microscopy image (left) shows four porphyrins. The models (right) illustrate the two systems shown in the picture. The protrusions correspond to the central atom (yellow sphere) and the two elevated portions to the saddle (orange). The characteristic cross shape results from the attached carbon monoxide molecules (red and blue).
Credit: Knud Seifert (TUM)

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. Her analysis helped the researchers understand the novel binding mode in detail. She also showed that the shape of the molecular saddle remains practically unchanged, even after the two gas molecules bind to the porphyrin.

The porphyrins reacted very differently when the researchers replaced the carbon monoxide with stronger-binding nitrogen monoxide. As expected, this binds directly to the central atom, though only a single molecule fits in each porphyrin ring. This has a significant effect on the electronic structure of the carrier molecule, and the characteristic saddle becomes flattened. Thus, the porphyrin reacts very differently to different kinds of gas -- a result that is relevant for potential applications, such as sensors.

Dr. Willi Auwaerter, one of the authors, is thrilled: "What's new is that we actually saw, for the first time, the mechanism on a molecular level. We even can selectively move individual gas molecules from one porphyrin to another." The team aims to explain the physical and chemical processes on surfaces and in nanostructures. Once these fundamental questions are answered, they will take on new challenges: How big is the influence of the central atom? How does the binding change in planar conformations? How can such systems be utilized to implement catalyzers and sensors through controlled charge transfers?

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.


Story Source:

The above story is based on materials provided by Technische Universitaet Muenchen. Note: Materials may be edited for content and length.


Journal References:

  1. Knud Seufert, Marie-Laure Bocquet, Willi Auwδrter, Alexander Weber-Bargioni, Joachim Reichert, Nicolαs Lorente, Johannes V. Barth. Cis-dicarbonyl binding at cobalt and iron porphyrins with saddle-shape conformation. Nature Chemistry, 2011; DOI: 10.1038/NCHEM.956
  2. Knud Seufert, Willi Auwärter, Johannes V. Barth. Discriminative Response of Surface-Confined Metalloporphyrin Molecules to Carbon and Nitrogen Monoxide. Journal of the American Chemical Society, 2010; 132 (51): 18141 DOI: 10.1021/ja1054884

Cite This Page:

Technische Universitaet Muenchen. "Direct observation of carbon monoxide binding to metal-porphyrines." ScienceDaily. ScienceDaily, 10 January 2011. <www.sciencedaily.com/releases/2011/01/110110121629.htm>.
Technische Universitaet Muenchen. (2011, January 10). Direct observation of carbon monoxide binding to metal-porphyrines. ScienceDaily. Retrieved August 20, 2014 from www.sciencedaily.com/releases/2011/01/110110121629.htm
Technische Universitaet Muenchen. "Direct observation of carbon monoxide binding to metal-porphyrines." ScienceDaily. www.sciencedaily.com/releases/2011/01/110110121629.htm (accessed August 20, 2014).

Share This




More Matter & Energy News

Wednesday, August 20, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Awesome New Camouflage Sheet Was Inspired By Octopus Skin

Awesome New Camouflage Sheet Was Inspired By Octopus Skin

Newsy (Aug. 19, 2014) — Scientists have developed a new device that mimics the way octopuses blend in with their surroundings to hide from dangerous predators. Video provided by Newsy
Powered by NewsLook.com
Researcher Testing on-Field Concussion Scanners

Researcher Testing on-Field Concussion Scanners

AP (Aug. 19, 2014) — Four Texas high school football programs are trying out an experimental system designed to diagnose concussions on the field. The technology is in response to growing concern over head trauma in America's most watched sport. (Aug. 19) Video provided by AP
Powered by NewsLook.com
Green Power Blooms as Japan Unveils 'hydrangea Solar Cell'

Green Power Blooms as Japan Unveils 'hydrangea Solar Cell'

AFP (Aug. 19, 2014) — A solar cell that resembles a flower is offering a new take on green energy in Japan, where one scientist is searching for renewables that look good. Duration: 01:29 Video provided by AFP
Powered by NewsLook.com
Tiny Satellites, Like The One Tossed From ISS, On The Rise

Tiny Satellites, Like The One Tossed From ISS, On The Rise

Newsy (Aug. 18, 2014) — The Chasqui I, hand-delivered into orbit by a Russian cosmonaut, is one of hundreds of small satellites set to go up in the next few years. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
 
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:  

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:  

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile iPhone Android Web
Follow Facebook Twitter Google+
Subscribe RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins