Halogenation effects on the bridgehead position of the adamantane molecule

Abstract

Halogen substitution effects on the bridgehead positioned carbon of adamantane molecule portraits many significant characteristics for the adamantane halides. As a result of the induction and electrostatic interaction caused by the substitution, large electron densities are formed around the halogens and a small positive electrostatic potential (σ-hole) is developed along the z-direction parallel to C-X bond axis. Computational study performed through EOM-CCSD method, B3LYP and WB97XD functionals of the density functional theory effectively supports this investigation in terms of molecular structure, vibrational properties, bonding behavior and electrostatic potential surfaces. Accordingly, substitution give rise to the change in the dipole moment and symmetry of the molecules. In addition, polarizabilities of the molecules along the C-X bond axis increases with respect to electron densities. HOMO-LUMO energy gap and positive σ-holes are found to decrease with the increase in the negative electron affinity. An anisotropic charge distribution developed upon substitution allows the adamantane halides to exhibit two different binding motifs like halogen and hydrogen bonding along the parallel and perpendicular directions of C-X bond. These characteristics feature of the halo adamantane finds applications in self-assembled monolayers, crystal engineering and biomedical applications.