Theoretical investigation of structures, electronic spectra and nonlinear optical properties of gold-pentacene (Au2C22H14) complexes

Eight systems formed by adding two gold atoms to a pentacene (Au2C22H14) were investigated by density functional theory. The structures, electronic spectra and second-order nonlinear optical properties of these eight systems were calculated and were compared with AuC22H14. The covalent bonds were observed in these eight systems (Au2C22H14) studied, and the Au–C bond can be strengthened by increasing the number of Au atoms. Moreover, introduction of the second Au atoms further increases the possible transitions and obvious red shift, except for system 4. This indicates that the properties of electronic transition can be tuned through changing the number of Au atoms. Systems 1, 1′, 2 and 2′ possess moderate molecular second-order polarizabilities, and βvec of System 1 is about six times larger than that of (AuC22H14). Thus, the position of Au atoms has also great influence on the second-order NLO response.