Molecular Recognition by Porphyrin Nanorings - in Water, in the Gas Phase and on Surfaces

The chemist's dream has long been to look at molecules, not just to see their shape, but to better understand behaviour derived from charge and other electronic properties. Optical microscopy is restricted to the visible light wavelength in the 400 - 700 nm range, and typical bond lengths of 0.1 nm. But the invention of scanning probe microscopy in the 1980s, made the dream a reality, providing subatomic resolution images. This technology maps out interactions between a sharp probe and a molecule, allowing atomic resolution images of individual molecules.
To achieve this objective of looking at molecules on a surface, a small number of molecules need to be placed in an even way on a surface such that individual molecules can be seen. Selecting an individual molecule of interest from a mixture and reliably deposing it on a surface was also a dream of chemists. This has now been realised through electrospray ion beam deposition (ES-IBD), which gives control of which molecule will be deposed on a surface by filtering based on mass. This has facilitated the study of large organic molecules, such as peptides, on surfaces using scanning probe microscopy.
The projects initial focus is the synthesis of porphyrin nanorings, which are molecules of interest due to their electronic properties. As porphyrin nanorings are large organic molecules, deposing them on a surface from the gas phase presents a great challenge, which this project aims to overcome using electrospray ion beam deposition. Scanning probe microscopy facilitates not just structural imaging, but also provides insight into charge distribution. This is because a range of approaches can be taken that map different interactions between the tip of the probe and the sample. Overall, this project will provide
an insight into how charge moves in these molecules.

The purpose of this research is to provide insight into fundamental principles that are important for the design of organic semiconductors, organic photovoltaics, and organic diodes. These are potentially useful in technology, such as computers, which in the future will require smaller components. Organic materials are advantageous as they are light weight, flexible, more processible, and do not rely on scarce elements.

This project falls within the EPSRC physical sciences research area.