• Wun-Fui Mark-Lee School of Chemical Sciences and Food Technology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, Selangor, Malaysia
  • Febdian Rusydi Department of Physics, Faculty of Science and Technology, University of Airlangga, Jl. Mulyorejo, Surabaya, Indonesia
  • Lorna Jeffery Minggu Fuel Cell Institute, Universiti Kebangsaan Malaysia, Selangor, Malaysia
  • Takashi Kubo Department of Chemistry, Graduate School of Science, Osaka University, Toyonaka, Osaka, Japan
  • Mohammad Kassim School of Chemical Sciences and Food Technology, Faculty of Science and Technology, Universiti Kebangsaan Malaysia, Selangor, Malaysia



1-benzoyl-3-(pyridine-2-yl)-1H-pyrazole, DFT, photoluminescence, Ru(II) photosensitiser, photoelectrochemical


Ru(II) complexes, [Ru(bpy)2(m-R-L)](PF6)2 where bpy = 2,2’-bipyridyl and  m-R-L= 1-(meta-R)-benzoyl-3-(pyridine-2-yl)-1H-pyrazole derivatives (R = H, CH3 and Cl) abbreviated as RuL, Ru(m-CH3-L) and Ru(m-Cl-L) complexes, respectively, were synthesized and characterized with spectroscopic techniques namely, infrared, UV-Vis and nuclear magnetic resonance (NMR), photoluminescence and mass spectroscopy. Density functional theory (DFT) and time-dependent (TD) DFT calculations were carried out to study the structural and electronic features of the molecules. These Ru(II) complexes exhibit photo-electronic properties required for a photosensitiser in a TiO2-catalysed photoelectrochemical (PEC) cell. In-depth understanding of the R-L fragment functionality is important to tune the photo-electronic properties of the Ru(II) complex. The highest-occupied molecular orbital (HOMO) is mainly localized at the Ru(II) centre, while the LUMO is dominantly spread across the R-L ligand. The Ru(II) complexes showed favourable metal-to-ligand charge transfer (MLCT) energy levels, which are comparably higher than the conduction band of TiO2 to facilitate electron injection process. Among the Ru(II) complexes, Ru(m-Cl-L) comparatively possesses the highest photoluminescence quantum yield and has the potential to be applied as photosensitiser in PEC systems.


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