Investigating Novel Two-Dimensional Halogen-Bonded Networks

The formation of two-dimensional supramolecular networks on inert surfaces has been studied by several groups over the last two decades, with attention focussed upon achieving control over network porosity and the possibility of functionalisation. Common to the majority of work undertaken to date is the role of hydrogen bonds in stabilising these networks and controlling their porosity. Very recently, however, collaborative work from the (Stephen) Jenkins and (Stuart) Clarke groups at Cambridge has highlighted the exciting prospect of creating such networks through the use of halogen bonds.

Halogen bonds are somewhat analogous to hydrogen bonds, but with some important differences. In hydrogen bonding, a hydrogen atom bound to a strongly electropositive atom become somewhat positively charged,
and hence capable of strong (mainly, but not wholly, electrostatic) attractive interaction with nearby electronegative species. In halogen bonds, the role of hydrogen is played by a readily polarisable halogen
atom - although such an atom is itself electronegative, polarisation can lead to a positively charged region of space known as the sigma hole, which can again attract nearby electronegative species.

In this PhD project, the student will investigate the nature of two-dimensional networks formed by halogen-bonding species on metal and graphitic surfaces. The work will involve a variety of techniques, including synchrotron-based methods, infrared spectroscopy and scanning tunnelling microscopy. The initial emphasis will be upon finding species (or combinations of species) that give rise to porous networks; later, attention will turn to functionalising the pores, so that they can act to direct surface chemical reactions occurring within them.