Direct Pathway to Molecular Photodissociation on Metal Surfaces Using Visible Light.
We demonstrate molecular photodissociation on single-crystalline metal substrates, driven by visible-light irradiation. The visible-light-induced photodissociation on metal substrates has long been thought to never occur, either because visible-light energy is much smaller than the optical energy gap between the frontier electronic states of the molecule or because the molecular excited states have short lifetimes due to the strong hybridization between the adsorbate molecular orbitals (MOs) and metal substrate. The S-S bond in dimethyl disulfide adsorbed on both Cu(111) and Ag(111) surfaces was dissociated through direct electronic excitation from the HOMO-derived MO (the nonbonding lone-pair type orbitals on the S atoms (nS)) to the LUMO-derived MO (the antibonding orbital localized on the S-S bond (σ*SS)) by irradiation with visible light. A combination of scanning tunneling microscopy and density functional theory calculations revealed that visible-light-induced photodissociation becomes possible due to the interfacial electronic structures constructed by the hybridization between molecular orbitals and the metal substrate states. The molecule-metal hybridization decreases the gap between the HOMO- and LUMO-derived MOs into the visible-light energy region and forms LUMO-derived MOs that have less overlap with the metal substrate, which results in longer excited-state lifetimes.
Surface and Interface Science Laboratory, RIKEN , Wako, Saitama 351-0198, Japan.
Emiko
E
Kazuma
Department of Chemistry, University of Ulsan , 93 Daehak-ro, Nam-gu, Ulsan 680-749, Republic of Korea.
Jaehoon
J
Jung
Graduate School of Science and Engineering, University of Toyama , Toyama 930-8555, Japan.
Hiromu
H
Ueba
Department of Chemistry, University of Illinois at Chicago , 845 West Taylor Street, Chicago, Illinois 60607, United States.
Michael
0000-0003-1419-9252
M
Trenary
Surface and Interface Science Laboratory, RIKEN , Wako, Saitama 351-0198, Japan.
Yousoo
0000-0001-7730-0704
Y
Kim