A new heteroleptic ruthenium(II) complex of [Ru(Hipdpa)(Hdcbpy)(NCS)(2)](-).0.5H(+).0.5[N(C(4)H(9))(4)](+) Ru(Hipdpa) {where Hdcbpy = monodeprotonated 4,4'-dicarboxy-2,2'-bipyridine and Hipdpa = 4-(1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)-N,N-diphenylaniline} was synthesized and characterized by elementary analysis, standard spectroscopy techniques, and cyclic voltammetry. The ground- and excited-state acid-base properties of Ru(Hipdpa) were studied by means of UV-vis absorption spectrophotometric and spectrofluorimetric titrations in 4:1(v/v) Britton-Robinson/dimethylformamide buffer solution. The four-step separate protonation/deprotonation processes were found in the ground states, and one of which taking place near the physiological pH range. The two observable excited-state protonation/deprotonation processes were found for the Ru(Hipdpa), constituting pH-induced "off-on-off" emission switches. The performance of the complexes as photosensitizers in nanocrystalline TiO(2)-based liquid solar cells containing an electrolyte solution (0.05 M I(2), 0.5 M LiI, and 0.5 M 4-tert-butylpyridine in 50% acetonitrile and 50% propylene carbonate) was investigated and found to achieve a much improved device performance (a short-circuit photocurrent density of 18.7 mA cm(-2), an open-circuit voltage of 630 mV, and an overall conversion efficiency of 6.85%) compared to a triphenylamine-free parent complex [Ru(Hpip)(Hdcbpy)(NCS)(2)](-).[N(C(4)H(9))(4)](+)-based device {Hpip = 2-phenyl-1H-imidazo[4,5-f][1,10]phenanthroline} and a comparable performance to that of cis-bis(isothiocyanato)bis(2,2'-bipyridine-4,4'-dicarboxylic acid)ruthenium(II) (N3) under identical experimental conditions. A density functional theory calculation of the molecular structures and electronic properties of the complexes was also carried out in an effort to understand their effectiveness in TiO(2)-based solar cells.
The neutral dimer complex Re 2 (CO) 6 (BIZ) 2 was directly obtained from a simple reaction between Re(CO) 5 Cl and N∩OH-type ligand 2-(1-phenyl-1H-benzoimidazol-2-yl)phenol (HBIZ). The further reaction of Re 2 (CO) 6 (BIZ) 2 with pyridine (Py) led to the monomeric Re(CO) 3 (BIZ)(Py), which was characterized by means of single-crystal X-ray diffraction analysis, 1 H NMR, elemental analysis, and UV-visible absorption, photoluminescence, and infrared spectroscopy as well as cyclic voltammetry. The photoelectrochemical properties of Re(CO) 3 (BIZ)(Py) spin-coated film modified indium-tin oxide electrode were investigated, and a large cathodic photocurrent up to 0.55 μA/cm 2 at -0.3 V bias potential was observed. The LUMO and HOMO energy levels of Re(CO) 3 (BIZ)(Py) were studied by density functional theory calculations. The possible mechanism of the photocurrent generation was discussed.
New hybrid multilayer films containing Prussian blue (PB) and a binuclear Ru(II) complex were successfully fabricated using the electrostatic layer-by-layer self-assembly technique. The process was carefully monitored by ultraviolet-visible (UV-vis) spectroscopy. A linear increase in the UV-vis absorbance with the number of deposited layers indicated that the film deposition was uniform and reproducible. The electrochemical and photoelectrochemical properties of these hybrid multilayer films were investigated in an aqueous Na2SO4 solution. PB and the binuclear Ru(II) complex assembled in the film were redox active with surface confined characteristics. The surface concentration and molecular area of RuL in the film were calculated according to a UV-vis absorption spectrum and cyclic voltammetry, respectively. The photocurrent generated by switching on the light irradiation of the film increased linearly as the deposited bilayers increased. The photocurrent action spectrum was in agreement with metal-to-ligand charge-transfer (MLCT) band of RuL in the absorption spectrum, which indicated that the photocurrent was generated based on MLCT excitation of the RuL in the (PB/RuL) film.
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