The way molecules arrange on a surface can be changed by the addition of guest molecules, say UK chemists. The finding will impact on many areas of science including quantum computing, they claim. 

Many molecules can adopt different crystalline arrangements, known as polymorphs. When studying molecules arranged on a surface, it is often possible to observe multiple polymorphs within a single sample. 

Neil Champness at the University of Nottingham and colleagues formed a hydrogen-bonded network of tetracarboxylic acid molecules by allowing them to self-assemble from a solution onto a surface. When they repeated the process, adding a guest molecule called coronene to the solution, they found that the molecules assembled into a different polymorph, known as a Kagomé network. Champness believes the work can be applied to other network types and guest species, allowing scientists to control the organisation of molecules on the nanoscale. 

Champness says the work also develops the concept of positioning molecules in well-defined arrays. 'For a whole variety of applications, specific molecular arrangements are vital,' he explained. 'One example is quantum computing, where the active components involved in the computing operation need to be very specifically spaced. Our study demonstrates the possibility of doing this, even though we are not near to actually trying to build a quantum computer.' 

The next step for Champness is to control the positioning of chemical functional groups in molecular arrangements, as well as other properties such as magnetic or photochemical functionality. He hopes this will lead to applications such as chemically specific and responsive surfaces. 

Joanne Thomson