Nanotechnology Now

Our NanoNews Digest Sponsors





Heifer International

Wikipedia Affiliate Button


DHgate

Home > Press > A Closer Look at Ring Opening

Anfractuous paths: Electron diffraction reveals the involvement of multiple structures in the complex photochemistry of photoswitchable nitro-substituted 1,3,3-trimethylindolinobenzospiropyran. The spiropyran-to-merocyanine isomerization due to ring opening produces primarily the cis–trans–cis structure (see picture; red O, blue N, yellow C), while competing nonradiative pathways lead to other structures, namely the closed forms in their triplet and singlet ground states.
Anfractuous paths: Electron diffraction reveals the involvement of multiple structures in the complex photochemistry of photoswitchable nitro-substituted 1,3,3-trimethylindolinobenzospiropyran. The spiropyran-to-merocyanine isomerization due to ring opening produces primarily the cis–trans–cis structure (see picture; red O, blue N, yellow C), while competing nonradiative pathways lead to other structures, namely the closed forms in their triplet and singlet ground states.

Abstract:
Electron diffraction studies of photoswitchable molecules

A Closer Look at Ring Opening

Weinheim, Germany | Posted on September 9th, 2010

We use a switch to turn lights off and on; however, light can also act as a switch itself, for example when molecules change their structure upon irradiation. Photoswitchable molecules are potentially interesting for use in holographic data storage, as molecular switches for nanomachines, or for switching biological functions in the biosciences. In order to tailor these molecules for different applications, it is necessary to have a comprehensive understanding of the underlying reaction mechanisms. A team led by Nobel Laureate Ahmed Zewail and members of his group at Caltech in Pasadena (California, USA) now reports in the journal Angewandte Chemie about their use of electron diffraction studies to observe a photoswitchable molecule in the process of "switching".

The molecule under examination was a complex ring system that switches between a closed form and an open form upon irradiation with UV light. In the closed spiropyran form it consists of two planar fused ring systems that form two orthogonal planes. When irradiated, a bond is broken to open a single ring. In this open merocyanin form, both units of the molecule are only connected through a bridge made by three bonds. Each of these bonds can theoretically have one of two spatial arrangements, which are designated as cis and trans. Furthermore, this molecule contains a nitro group (-NO2), which allows it to enter into two different electronic states—singlet or triplet—when excited by light.

Which form does it choose? This is what the researches wished to determine in order to study the reaction mechanism. To do this, they used a method known as laser-desorption electron diffraction. In this technique, a sample is heated and vaporized by laser so rapidly that the sample molecules do not have time to decompose. The isolated molecules are then bombarded with electrons. The electrons are diffracted by the atomic nuclei of the molecule, which results in a characteristic diffraction pattern. The scientists recorded diffraction patterns 100 nanoseconds before and after excitation with UV.

By using theoretical model calculations, the researchers were able to interpret these diffraction patterns. The result: "Ring opening leads primarily to the cis-trans-cis structure," according to Zewail, "while competing, non-irradiative paths lead to other structures, such as the closed forms in their triplet and singlet ground states."

"Our results demonstrate the enormous capability of the electron diffraction technique to solve such complex, nanometer-scale structures with minimal symmetry," says Zewail.


Author: Ahmed H. Zewail, California Institute of Technology, Pasadena (USA), www.zewail.caltech.edu/contact/index.html

Title: Direct Determination of Conformations of Photoswitchable Molecules by Laser Desorption-Electron Diffraction

Angewandte Chemie International Edition 2010, 49, No. 37, 6524-6527, Permalink to the article: dx.doi.org/10.1002/anie.201003583

####

For more information, please click here

Copyright © Angewandte Chemie

If you have a comment, please Contact us.

Issuers of news releases, not 7th Wave, Inc. or Nanotechnology Now, are solely responsible for the accuracy of the content.

Bookmark:
Delicious Digg Newsvine Google Yahoo Reddit Magnoliacom Furl Facebook

Related News Press

News and information

Small but heading for the big time: Nanobiotix half year results for the six months ended 30 June 2015, in line with expectations: Major clinical achievements and corporate developments August 28th, 2015

A new technique to make drugs more soluble August 28th, 2015

Nanocatalysts improve processes for the petrochemical industry August 28th, 2015

Nanolab Technologies LEAPS Forward with High-Performance Analysis Services to the World: Nanolab Orders Advanced Local Electrode Atom Probe (LEAP®) Microscope from CAMECA Unit of AMETEK Materials Analysis Division August 27th, 2015

Possible Futures

Sediment dwelling creatures at risk from nanoparticles in common household products August 13th, 2015

Harris & Harris Group Reports Financial Statements as of June 30, 2015, and Announces a Stock Repurchase Program August 10th, 2015

Molecular trick alters rules of attraction for non-magnetic metals August 5th, 2015

Global Carbon Nanotubes Industry 2015: Acute Market Reports August 4th, 2015

Academic/Education

Announcing Oxford Instruments and School of Physics signing a Memorandum of Understanding August 26th, 2015

Kwansei Gakuin University in Hyogo, Japan, uses Raman microscopy to study crystallographic defects in silicon carbide wafers August 25th, 2015

JPK reports on the use of a NanoWizard® AFM-SECM system at the Université Paris Diderot looking at nanoscale biostructures August 18th, 2015

Rice, Penn State open center for 2-D coatings: National Science Foundation selects universities to develop atom-thin materials with industry partners August 13th, 2015

Molecular Machines

Injectable electronics: New system holds promise for basic neuroscience, treatment of neuro-degenerative diseases June 8th, 2015

One step closer to a single-molecule device: Columbia Engineering researchers first to create a single-molecule diode -- the ultimate in miniaturization for electronic devices -- with potential for real-world applications May 25th, 2015

UCLA nanoscientists are first to model atomic structures of three bacterial nanomachines: Cryo electron microscope enables scientists to explore the frontiers of targeted antibiotics April 21st, 2015

Advances in molecular electronics: Lights on -- molecule on: Researchers from Dresden and Konstanz succeed in light-controlled molecule switching April 20th, 2015

Memory Technology

'Magic' sphere for information transfer: Professor at the Lomonosov Moscow State University made the «magic» sphere for information transfer August 24th, 2015

Superlattice design realizes elusive multiferroic properties: New design sandwiches a polar metallic oxide between an insulating material August 23rd, 2015

High-precision control of nanoparticles for digital applications August 19th, 2015

Scientists achieve major breakthrough in thin-film magnetism August 17th, 2015

Nanomedicine

Small but heading for the big time: Nanobiotix half year results for the six months ended 30 June 2015, in line with expectations: Major clinical achievements and corporate developments August 28th, 2015

A new technique to make drugs more soluble August 28th, 2015

These microscopic fish are 3-D-printed to do more than swim: Researchers demonstrate a novel method to build microscopic robots with complex shapes and functionalities August 26th, 2015

Glitter from silver lights up Alzheimer's dark secrets August 25th, 2015

Announcements

Small but heading for the big time: Nanobiotix half year results for the six months ended 30 June 2015, in line with expectations: Major clinical achievements and corporate developments August 28th, 2015

A new technique to make drugs more soluble August 28th, 2015

Nanocatalysts improve processes for the petrochemical industry August 28th, 2015

Nanolab Technologies LEAPS Forward with High-Performance Analysis Services to the World: Nanolab Orders Advanced Local Electrode Atom Probe (LEAP®) Microscope from CAMECA Unit of AMETEK Materials Analysis Division August 27th, 2015

Nanobiotechnology

Small but heading for the big time: Nanobiotix half year results for the six months ended 30 June 2015, in line with expectations: Major clinical achievements and corporate developments August 28th, 2015

Nanotechnology that will impact the Security & Defense sectors to be discussed at NanoSD2015 conference August 25th, 2015

Louisiana Tech University researchers discover synthesis of a new nanomaterial: Interdisciplinary team creates biocomposite for first time using physiological conditions August 24th, 2015

How UEA research could help build computers from DNA August 19th, 2015

NanoNews-Digest
The latest news from around the world, FREE



  Premium Products
NanoNews-Custom
Only the news you want to read!
 Learn More
NanoTech-Transfer
University Technology Transfer & Patents
 Learn More
NanoStrategies
Full-service, expert consulting
 Learn More











ASP
Nanotechnology Now Featured Books




NNN

The Hunger Project







Car Brands
Buy website traffic