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• Stephanie N. Choing,ÌýAaron J. Francis,ÌýGraham Clendenning,ÌýMichael S. Schuurman,ÌýRoger D. Sommer,ÌýIsaac Tamblyn,ÌýWalter W. Weare, andÌýTanja Cuk^*
• J. Phys. Chem. C,Ìý2015,Ìý119Ìý(30), pp 17029–17038.Ìý¶Ù°¿±õ:Ìý10.1021/acs.jpcc.5b00513. Download

The excited state dynamics of a d⁰Ìývanadium(V) oxido ligand-to-metal charge transfer (LMCT) complex, VOL^F, were investigated via a combination of static optical and X-ray absorption (XAS) spectroscopy, transient optical absorption spectroscopy, and time-dependent density functional theory (TD-DFT). Upon excitation of the LMCT in the visible region, transient absorption data reveal that internal conversion traps the excited carrier population into a long-lived charge transfer state of 3d_xyÌýelectron character, S₁(d_xy). The internal conversion is substantiated by an isosbestic point in the transient absorption data, two nearby charge transfer states that couple well by TD-DFT, multiple rates in the ground state recovery, and the decay kinetics of an excited state absorption with the energy of a d-d transition in O K-edge XAS spectra. The long lifetime (∼420 ps) of S₁(d_xy) can be ascribed to its poor optical and vibrational coupling to a distorted ground state (S₀^*) via a negligible electronic dipole transition in TD-DFT. The lack of luminescence or an identifiable triplet state also suggests attributing the lifetime to electronic contributions. In conjunction with its strong visible absorption and reduction potential, the long-lived LMCT suggests that molecules such as VOL^FÌýcould have potential utility for energy conversion applications. Moreover, the results show that internal conversion between two nearby charge transfer states, differentiated by their 3d character, can form a long-lived charge transfer excitation, broadly informing the discovery of 3d metal-centered optical absorbers with long-lived charge transfer lifetimes.