Energetics and structural insights of molecular conductors using density functional theory methods: 1,3-dithiole-2-thione, 1,3-dithiole-2-one, 1,3-dioxole-2-one, and 1,3-dioxole-2-thione

Abstract

Computations were carried out employing the restricted HartreeFock (RHF) and density functional theory (DFT) methods to investigate the geometries and energies for the 1,3-dithiole-2-thione (DTT), 1,3-dithiole-2-one (DTO), 1,3-dioxole-2-thione (DOT), and 1,3-dioxole-2-one (DOO) molecules and their radical cations. The geometrical parameters of all the four molecules suggest a finite extent of extended conjugation across the molecules. The radical cations of the DTT and DOT molecules exhibit increased extent of conjugation compared to their neutral analogues. However, on going from the neutral DOO and DTO molecules to their radical cations, the extent of conjugation across the ions decreases and two unsaturated sites become isolated from each other. Requirement of the relaxation energy for the formation of radical cation is much lower for the DTT and DOT molecules compared to that for the DOO and DTO molecules. Smaller relaxation energy requirement favors minimal resistance to charge transport along the molecular stacking. Therefore, it is speculated that the DTT and DOT molecules are better molecular conductors as compared to the DOO and DTO molecules. © 2009 World Scientific Publishing Company.