Synthetic and structural studies of 1-halo-8-(alkylchalcogeno)naphthalene derivatives

Abstract

A series of eight 1-halo-8-(alkylchalcogeno)naphthalene derivatives ( 1 – 8 ; halogen=Br, I; alkylchalcogen=SEt, SPh, SePh, TePh) containing a halogen and a chalcogen atom occupying the peri positions have been prepared and fully characterised by using X-ray crystallography, multinuclear NMR spectroscopy, IR spectroscopy and MS. Naphthalene distortion due to non-covalent substituent interactions was studied as a function of the bulk of the interacting chalcogen atoms and the size and nature of the alkyl group attached to them. X-ray data for 1 , 2 , 4 and 5 – 8 were compared. Molecular structures were analysed in terms of naphthalene ring torsions, peri-atom displacement, splay angle magnitude, X⋅⋅⋅E interactions, aromatic ring orientations and quasi-linear X⋅⋅⋅EC arrangements. A general increase in the X⋅⋅⋅E distance was observed for molecules that contain bulkier atoms at the peri positions. The I⋅⋅⋅S distance of 4 is comparable with the I⋅⋅⋅Te distance of 8 , and is ascribed to a stronger lone pair–lone pair repulsion due to the presence of an axial S(naphthyl) ring conformation. Density functional theory (B3LYP) calculations performed on 5 – 8 revealed Wiberg bond index values of 0.05–0.08, which indicate minor interactions taking place between the non-bonded atoms in these compounds.