Synthetic and Structural Studies of 1,8-Chalcogen Naphthalene Derivatives



Four novel 1,8-disubstituted naphthalene derivatives 47 that contain chalcogen atoms occupying the peri positions have been prepared and fully characterised by using X-ray crystallography, multinuclear NMR spectroscopy, IR spectroscopy and MS. Molecular distortion due to noncovalent 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 47 was compared to the series of known 1,8-bis(phenylchalcogeno)naphthalenes 13, which were themselves prepared from novel synthetic routes. A general increase in the E⋅⋅⋅E′ distance was observed for molecules containing bulkier atoms at the peri positions. The decreased S⋅⋅⋅S distance from phenyl-1 and ethyl-4 analogues is ascribed to a weaker chalcogen lone pair–lone pair repulsion acting in the ethyl analogue due to the presence of two equatorial S(naphthyl) ring conformations. Two novel peri-substituted naphthalene sulfoxides of 1, Nap(O[DOUBLE BOND]SPh)(SPh) 8 and Nap(O[DOUBLE BOND]SPh)29, which contain different valence states of sulfur, were prepared and fully characterised by using X-ray crystallography and multinuclear NMR spectroscopy, IR spectroscopy and MS. Molecular structures were analysed by using naphthalene ring torsions, peri-atom displacement, splay angle magnitude, S⋅⋅⋅S interactions, aromatic ring orientations and quasi-linear O[DOUBLE BOND]S⋅⋅⋅S arrangements. The axial S(naphthyl) rings in 8 and 9 are unfavourable for S⋅⋅⋅S contacts due to stronger chalcogen lone pair–lone pair repulsion. Although quasi-linear O[DOUBLE BOND]S⋅⋅⋅S alignments suggest attractive interaction is conceivable, analysis of the B3LYP wavefunctions affords no evidence for direct bonding interactions between the S atoms.