DFT investigation of self-assembling, light-responsive azobenzene dithiol ligands

Abstract

Azobenzene dithiol (ADT) ligands that exhibit trans–cis conversion when exposed to UV light are sometimes used in the light-induced self-assembly of nanoparticles. In this work, we perform density functional theory (DFT) calculations to study the ligand–ligand interactions that drive this self-assembly process. The dipole moment of individual ADT molecules and interaction energy between a pair of ADT molecules are computed for cis and trans states in various compositions of methanol-toluene mixture used as the solvent. Cis-ADT is found to possess substantially higher dipole moment than trans-ADT. Dipole moment of the mixture increases with methanol % up to 20% methanol, followed by lesser change on further addition of methanol. Trans-cis isomerization results in a shift of the position of energy minimum on the interaction energy against separation curve. The scaling of effective interaction between nanoparticles against separation for different ADT loading are also estimated from the results of DFT calculations.