Transition and Excited States of 1,1'-azo-bis-1,2,3-triazole

A novel photochromic molecule has been recently synthesized\footnote{Yu-Chuan Li et al. \emph{J. Am. Chem. Soc.}, 2010, 132, 12172}. The photo-isomerization of this nitrogen-rich small molecule is efficiently controlled by a xenon flash lamp suggesting a potential in photonic and molecular mechanics applications. We perform a synergistic quantum molecular dynamics (QMD), real-time time dependent density functional theory (TDDFT) and TDDFT- perturbation theory study to capture and elucidate the transition state, excitation energies and optical properties of the molecule. We also use it to test performance of recently developed real-time TDDFT method\footnote{V. Goncharov, K. Varga, \emph{Phys. Rev. B} 2010, submitted.} to calculate hyperpolarizabilities and compare results with the Sternheimer method.