Electrochemical and Photoelectrochemical Investigation of New Self-Assembled Films Based on Prussian Blue and a Terpyridyl RuII Complex

A new hybrid multilayer film containing Prussian blue (PB) and a bis-terpyridyl RuII complex of RuII(L)2(ClO4)2 (in which L = 4′-(4-(imidazol-1-yl)phenyl)-2,2′:6′,2″-terpyridine), was fabricated though covalently and electrostatic layer-by-layer self-assembly techniques, and characterised by UV-vis absorption spectroscopy, cyclic voltammetry, and photoelectrochemical techniques. The results demonstrated that the two film-forming components were successfully transferred into the hybrid film, which exhibited three quasi-reversible redox couples centred at 0.06, 0.76, and 1.0 V. The photoelectrochemical studies showed that an 11-layer film exhibited a large cathodic photocurrent density of 7.72 μA cm–2 while irradiated with 100 mW cm–2 polychromatic light (325 < λ < 730 nm) at an applied potential of –0.2 V versus a saturated calomel electrode.

pH luminescence switching, dihydrogen phosphate sensing, and cellular uptake of a heterobimetallic ruthenium(II)-rhenium(I) complex

A new heterobimetallic ruthenium(II)-rhenium(I) complex of [Ru(bpy)2(HL)Re(CO)3Cl](ClO4)2·6H2O (RuHLRe) {bpy = 2,2'-bipyridine and HL = 2-(4-(2,6-di(pyridin-2-yl)pyridin-4-yl)phenyl)-1H-imidazo[4,5-f][1,10]phenanthroline} was synthesised and characterised by elemental analysis, proton nuclear magnetic resonance spectroscopy, and mass spectrometry. The ground- and excited-state acid-base properties of RuHLRe were studied using UV-Vis absorption spectrophotometric and spectrofluorimetric titrations in a 100 : 1 (v/v) Britton-Robinson buffer-CH3CN solution combined with luminescence lifetime measurements. The complex exhibited two-step separate protonation-deprotonation processes in both the ground and excited states. The complex acted as pH-induced "off-on-off" luminescence switches (I(on)/I(off) = 31.0 and 14.6), with one of the switching actions being driven by pH variations over the physiological pH range (5.3-8.0). Importantly, cellular imaging and cytotoxicity experiments demonstrated that RuHLRe rapidly and selectively illuminated the membrane of HeLa cells over fixed cells and exhibited reduced cytotoxicity at the imaging concentration compared to the Re(I)-free parent Ru(II) complex. In addition, RuHLRe acted as an efficient "turn on" emission sensor for H2PO4(-) and "turn off" emission sensor for F(-) and OAc(-).

The effects of linear assembly of two carbazole groups on acid-base and DNA-binding properties of a ruthenium(II) complex

A novel Ru(II) complex of [Ru(bpy)2(Hbcpip)](ClO4)2 {where bpy=2,2-bipyridine, Hbcpip=2-(4-(9H-3,9'-bicarbazol-9-yl)phenyl)-1H-imidazo[4,5-f][1,10]phenanthroline} is synthesized and characterized. Calf-thymus DNA-binding properties of the complex were studied by UV-vis absorption and luminescence titrations, steady-state emission quenching by [Fe(CN)6](4-), DNA competitive binding with ethidium bromide, thermal denaturation and DNA viscosity measurements. The results indicate that the complex partially intercalated into the DNA with a binding constant of (5.5±1.4)×10(5) M(-1) in buffered 50 mM NaCl. The acid-base properties of the complex were also studied by UV-visible and luminescence spectrophotometric pH titrations, and ground- and excited-state acidity ionization constant values were derived.