Abstract
ABSTRACT Using a combination of X-ray diffraction and simulation techniques, we are able to identify a crystalline monolayer of 1,3,5-triiodotrifluorobenzene formed on graphite. The monolayer is found to exhibit an incommensurate hexagonal unit cell with a lattice parameter of 9.28(7) Å, exhibiting a trigonal arrangement of iodine atoms not found in the bulk structure. DFT simulations have been performed exhibiting close agreement with the experimental structure. Importantly these simulations can be used to compare the strength of the intermolecular interactions both with and without Van der Waals corrections. Thus it is possible to estimate that halogen bonding consists of approximately half the total interaction energy. This demonstrates that despite the presence of strong directional non-covalent bonding, dispersion interactions account for a very significant proportion of the total energy.
Highlights
Physical adsorption of molecules has been studied in a range of contexts by many authors
Alongside scanning tunnelling microscopy studies [6,7], a number have been performed utilising X-ray and neutron diffraction. This has been done for a range of physisorbed systems in their increasing complexity of intermolecular interactions: purely van der Waals e.g. alkanes [8,9,10] and fluoroalkanes [11,12]; hydrogen-bonded species such as alcohols [13], carboxylic acids [14] and amides [15,16]; and dipolar molecules such as halomethanes [11,17,18,19]
We report the assembly of a TITFB monolayer that does adopt an ordered structure on graphite based on the X3 motif
Summary
Physical adsorption of molecules has been studied in a range of contexts by many authors. Alongside scanning tunnelling microscopy studies [6,7], a number have been performed utilising X-ray and neutron diffraction. This has been done for a range of physisorbed systems in their increasing complexity of intermolecular interactions: purely van der Waals e.g. alkanes [8,9,10] and fluoroalkanes [11,12]; hydrogen-bonded species such as alcohols [13], carboxylic acids [14] and amides [15,16]; and dipolar molecules such as halomethanes [11,17,18,19]. Other halogen-containing species have been investigated [20,21], which has led to the observation of the first 2D halogen bonded monolayers [22], with several further studies addressing assembly by halogen bonding in monolayers [23,24,25]
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