Spirobis-dithiepines as promising scaffolds for advanced materials

The goal of this thesis was to develop a new scaffold based on spirobis-dithiepines and study its properties for applications in advanced materials.; A new structure was introduced in the form of a spirobis-dithiepine core which was proposed as a potential core for banana-shaped mesogenic compounds. Synthetic routes were developed to obtain various bis-substituted spirobis-dithiepines and a versatile synthon in the form of a bis-aldehyde. The bis-aldehyde was shown to be a crucial intermediate which could be modified to obtain a variety of potential banana-shaped mesogenic compounds. A novel rearrangement yielding, an alpha-beta unsaturated ketone dithiepine, was introduced and a mechanism was proposed for the rearrangement.; A study of the photochemically properties of the bis-aldehyde showed that the compound undergoes a photo induced hydrogen migration. The photo induced hydrogen migration was shown to disrupt the conjugation between the conjugated donor-acceptor system present in the bis-aldehyde. The photo induced hydrogen migration was proposed a method of modulating hyperpolarizabilities in the molecule and making a one way molecular switch.; Examination of the spirobis-dithiepine reveals a chiral axis in the spiro connection which affords the molecule with axial chirality. Evidence was obtained via a chiral column separation of the existence of the enantiomers of the bis-aldehyde.; A theoretical and experimental conformational analysis of the spirobis-dithiepine core revealed the existence of stable conformers which are dynamically interconverting at room temperature. Computational methods using Gaussian 03 were used to identify the stable conformers and transitions states for the spirobis-dithiepine core. The core was shown to interconvert from a cis to trans conformation converting through various stable conformers and transition states. The relative conformational energies for two substituted spirobis-dithiepines (bis-aldehyde and bis-acenaphthaquinone dithiepine) were computed and the results showed that their relative energy differences are similar to that of the core. A variable temperature NMR of the bis-aldehyde showed the existence of conformers.; The computed dipole moments for both substituted spirobis-dithiepines showed a considerable change when comparing the cis conformation to the trans conformation. The bis-acenaphthaquinone dithiepine showed a greater effect. The conformational analysis demonstrated the existence of a bi-state system which could be subtly interconverted through a conformational change.