BRIDGING OF QUANTUM CHEMISTRY CALCULATIONS WITH ATOMISTIC/COARSE GRAINED SIMULATIONS

Abstract

Photo-responsive materials can change their optical, magnetic, electrical and structural properties in response to an exposure to light of different wavelengths. One particular example of photo responsive materials is Azobenzene, which undergoes a trans-cis transformation on exposure to UV light. When gold nanoparticles are functionalized with azobenzene di-thiol (ADT) ligands, they self-assemble to closed-pack structures on exposure to UV light, which occurs because of a dipole-dipole attraction between cis-azobenzenes. This self-assembly is reversible as the removal of UV light (or an exposure to visible light) results in trans-azobenzene that does not possess a dipole moment. In this work, quantum-chemistry calculations are performed to investigate the behaviour of ADT ligands, using GAUSSIAN software package. More specifically, we analyse the effect of solvent type and molecule orientation on the dipole moment of ADT and interactions between a pair of ADT. After that, we also studied how ADT molecules response at excited state to an exposure of UV/Visible light in gas phase and in solvent phase. In excited state calculations, we calculate excitation energy of different excited states and compare with its experimental values. At last we calculate frequencies at different mode assignment of ADT molecules, compare it with experimental values, and obtain a frequency spectrum.