Spectral Properties of tetrathiabenzoquinones and their self-assembly in the solid state

Abstract

Bis(1,4-dithiacyclohexano)[2,3-b:2′,3′-e]-1,4-benzoquinone 3a and analogous cyclic dithiaquinone derivatives were synthesized. The difference (Δλ) in λmax of these dyes between the solution phase and vapor deposited thin film indicates the degree of strength of the intermolecular π-π interactions in the solid state. The Δλ values were largely affected by the interlayer distances and the steric requirements of the molecules. The three dimensional molecular stacking of dye 3a was evaluated by X-ray crystal analysis and the substituent effects on the properties of analogous dyes were evaluated by the MOPAC and AMPAC calculation methods. The vapor deposited thin film of dye 3a gave large 3rd order nonlinear optical susceptibility. The intermolecular π-π interactions of the dye molecules play an important role for these special functionalities.