DFT Study of the Conformation and Optical Properties of Hybrid Aun-Dithienylethene Systems (n = 3, 19, 25).

The journal of physical chemistry. A

PubMedID: 24912128

Fihey A, Kloss B, Perrier A, Maurel F. DFT Study of the Conformation and Optical Properties of Hybrid Aun-Dithienylethene Systems (n = 3, 19, 25). J Phys Chem A. 2014;.
We present a theoretical study of Aun -dithienylethene hybrid systems (n = 3, 19, 25), where the organic molecule is covalently linked to the metallic aggregate. We aim at gaining insights on the optical properties of experimental hybrid photochromic devices, in which the metallic part is a nanometer-scaled gold nanoparticle (NP). We present a DFT-based calculation scheme to model the ground-state (conformation, energetic parameters) and excited state properties (UV-Visible absorption spectra) of this type of hybrid systems. Within this framework, the structural parameters (adsorption site, orientation and internal structure of the photochrome) are found to be slightly dependent on the size/shape of the gold aggregate. The influence of the gold fragment on the optical properties of the resulting hybrid system is then discussed with the help of TD-DFT combined with an analysis of the virtual orbitals involved in the photochromic transitions. We show that, for the open hybrid isomer, the number of gold atoms is the key parameter to recover the photoactive properties that are experimentally observed. On the opposite, for hybrid closed systems, the three-dimensional structure of the metallic aggregate is of high impact. We thus conclude that Au25 corresponds to the most appropriate fragment to model nanometer-sized NP-DTE hybrid device.