Bis(Bipyridyl)-Ru(II)-1-benzoyl-3-(pyridine-2-yl)-1H-pyrazole as potential photosensitiser: Experimental and density functional theory study

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. © 2017 penerbit utm press. all rights reserved.