The structures of 1-bromoheptane and 1-bromononane monolayers adsorbed on the surface of graphite

Abstract

X-ray diffraction and differential scanning calorimetry (DSC) have been used to confirm the formation of the solid monolayers of 1-bromoheptane (C7Br) and 1-bromononane (C9Br) on the surface of graphite. The X-ray diffraction patterns of these two species can be fitted by two possible monolayer structures with symmetries Pgb and P2. For one of these (C7Br) this ambiguity can be lifted using neutron diffraction and the Pgb plane group can be identified as the correct structural solution. Both of the unit cells contain two molecules forming an approximately 90 o zig-zag chain of bromine atoms with an inter-bromine distance of approximately 3.70 Å , which is similar to twice the Van der Waals radii of the bromine, suggesting rather little non-covalent interaction. The dipole moments in two adjacent chains are opposed leading to no net dipole for the layer as a whole.

Halogen-Bond-Based Molecular Self-Assembly on Graphene Surface: A First-Principles Study

“…It has been well documented that haloperfluorocarbons (X–PFCs) act as good XB donors and are capable of establishing strong XBs with electron-rich molecules, especially pyridine derivatives. ,− Therefore, the specific N···X–PFC synthons have been commonly utilized in 3D crystal engineering and supramolecular architecture. The formation of 2D XB-based monolayers of X-PFCs and pyridyl species was first reported by Clarke et al, and in their pioneering works, the self-assembled cocrystal physisorbed monolayers involving 4,4′-bipyridine and 1,4-diiodotetrafluorobenzene ( 4F2I ), 1,4-dibromotetrafluorobenzene ( 4F2I ), 1,4-diiodobenzene ( 4H2I ) on graphite were identified via synchrotron X-ray diffraction and DFT calculations. − Moreover, they also studied the adsorbed monolayers of several halogenated alkanes and pyridine derivatives on the graphite substrate using differential scanning calorimetry and X-ray and neutral diffraction. − Subsequently, Wan and co-workers has demonstrated the formation of an open porous network on HOPG using ethynylpyridine and aryl-halide-based building blocks, and they obtained four main supramolecular assemblies driven by the N···I interactions between terminal pyridyl moieties and iodoperfluorobenzenes . However, to the best of our knowledge, few theoretical studies concerning intermolecular X···N bonds in the binary network of X-PFCs and pyridyl derivatives on graphite surface have been reported to date.…”

2D constraint modifies packing behaviour: a halobenzene monolayer with X3 halogen-bonding motif

“…alkanes [ 8 – 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 – 19 ]. More recently, 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 – 25 ].…”