title: A DFT study on structures, frontier molecular orbitals and UV-vis spectra of RuX(PPh3)(NHCPh2)L (X=Tp and Cp; L=Cl and N3).
abstract: Geometry optimization for RuX(PPh3)(NHCPh2)(L) (X=hydridotris(pyrazolyl)borate (Tp) and cyclopentadiene (Cp); L=Cl and N3) are investigated by using density functional theory (DFT) with DZVP2/DZVP all-electron mixed basis sets and compared with available experimental values, and the calculated structures are in very good agreement with experimental data. The frontier molecular orbitals (FMOs) and electronic transitions have been investigated as well. Our calculations show that the π electron-rich ligand (N3) may increase the energies of occupied orbitals and reduce the energy gap of the HOMO-LUMO (ΔEL-H) in these ruthenium based complexes. The simulated UV-vis spectra of these complexes in methanol have been studied with time-dependent density functional theory (TD-DFT), and conductor-like polarizable continuum model (CPCM) was employed to account for the solvent effects. Our results show that a number of absorption peaks are found in the visible region (400-800 nm) with non-zero oscillator strengths. The strongest adsorption feature is associated to a transition from HOMO-2 to LUMO, which is assigned to metal-to-ligand charge transfer (MLCT) or metal/ligand-to-ligand charge transfer (MLCT/LLCT) depending on co-ligands. In addition, the Cp group increases electron-accept ability and results in red shift due to its π electron-rich and π donor characters. According to our results, these ruthenium based complexes are good candidates for dye-sensitized solar cell owing to their absorption intensities and rich absorption bands in the visible region.
authors.affiliation: Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei 10617, Taiwan. Electronic address: tsanghsiu@gmail.com.
authors.forename: Tsang-Hsiu
authors.initials: TH
authors.lastname: Wang
authors.affiliation: Office of Research and Development, National United University, Miaoli 36003, Taiwan.
authors.forename: I-Teng
authors.initials: IT
authors.lastname: Wang
authors.affiliation: Department of Applied Physics and Chemistry, University of Taipei, Taipei 10048, Taiwan.
authors.forename: Wen-Lin
authors.initials: WL
authors.lastname: Huang
authors.affiliation: Department of Applied Physics and Chemistry, University of Taipei, Taipei 10048, Taiwan.
authors.forename: Li-Yu
authors.initials: LY
authors.lastname: Huang
mesh_terms: D004583:Electrons; D008024:Ligands; D008958:Models, Molecular; D008968:Molecular Conformation; D011789:Quantum Theory; D012428:Ruthenium / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet; D013816:Thermodynamics
chemical_list: D008024:Ligands; D012428:Ruthenium
keywords: Charge transfer; DFT; DSSC; Ruthenium complex; UV