Trinuclear Ru Research Articles

Intramolecular energy transfer in ruthenium(II)-chromium(III) chromophore-luminophore complexes. Ru(bpy)2[Cr(cyclam)(CN)2]24+

A new trinuclear Ru(II)-Cr(III) chromophore-luminophore complex, Ru(bpy){sub 2}(Cr(cyclam)(CN){sub 2}){sub 2}{sup 4+}, has been synthesized and characterized. Visible light absorption by the Ru(bpy){sub 2}{sup 2+} chromophore leads to emission from the Cr(cyclam)(CN){sub 2}{sup +} luminophore, as a consequence of very efficient ({ge} 99%) and fast (subnanosecond time scale) chromophore-luminophore exchange energy-transfer process. The emission is intense ({Phi} = 5.3 {times} 10{sup {minus}3} in H{sub 2}O) and long-lived ({tau} = 260 {mu}s in H{sub 2}O). The photophysical properties of the luminophore are slightly perturbed by interaction with the chromophore, resulting in a sharper emission band shape and shorter radiative and radiationless lifetimes. The presence of a Ru(II) {yields} Cr(III) intervalence transfer state, hardly detectable in the ground-state spectrum, is clearly revealed by the excited-state absorption spectrum of the chromophore-luminophore complex.

Synthesis and desulfurization of 2,5-dihydrothiophene transition-metal complexes: models for the hydrodesulfurization (HDS) of thiophene

Several S-coordinated 2,5-dihydrothiophene (2,5-DHT) transition-metal complexes were synthesized in order to determine whether or not this type of coordination promotes butadiene elimination from the 2,5-DHT ligand, a step proposed in a mechanism for the hydrodesulfurization (HDS) of thiophene. Thermal decomposition of W(CO)[sub 5](2,5-DHT) and Re[sub 2](CO)[sub 9](2,5-DHT) at 110C liberates butadiene and free 2,5-DHT (relative ratio 1:4). Uncoordinated 2,5-DHT itself does not decompose at 120C after 3 days. Thus, S-coordination of 2,5-DHT to these metal centers does promote the liberation of butadiene. Upon being heated at 180C, MCl[sub 2](2,5-DHT)[sub 2] (M = Pd, Pt) gives off mainly thiophene and free 2,5-DHT (1:1) with only a small amount of butadiene. Thus, depending on the complex either butadiene or thiophene may be evolved. The reaction of Ru[sub 3](CO)[sub 12] with 2,5-DHT forms the trinuclear ([mu][sub 2]-H)Ru[sub 3](CO)[sub 9]([mu][sub 3]-1-4-[eta][sup 4]-DHT), whose X-ray structure determination shows that the sulfur and olefin of the 2,5-DHT coordinate to two different ruthenium atoms but also C-H cleavage occurs at C(2) forming a C-Ru bond. The structure of an S-coordinated DHT complex [Cp(PMe[sub 3])[sub 2]Ru(2,5-DHT)](PF[sub 6]) is also reported.

Complexes of tricoordinate hypervalent pnictogens with pentamethylcyclopentadienylruthenium

AbstractThe complexes of a pentamethylcyclopentadienylruthenium moiety with hypervalent tricoordinate pnictogens are reported. A unique mode of complexation is observed for each of the different pnictogens (P, As, Sb). The phosphorus derived complex exhibits an 8‐electron tetrahedral bonding environment at phosphorus. The antimony derived complex maintains a 10‐electron bonding system at antimony with a pseudo‐trigonalbipyramidal geometry at antimony. The arsenic‐containing complex is formed with destruction of the original arsenic heterocycle and formation of a trinuclear Ru–Ru–As ring. Remarkably, the formation of the arsenic ruthenium complex can be reversed to reconstruct the original arsenic heterocycle.

Conversion of Light into Electricity with Trinuclear Ruthenium Complexes Adsorbed on Textured TiO2 Films

AbstractA series of CN‐bridged trinuclear Ru complexes of the general structure [RuL2(μ‐(CN)Ru(CN)L2′)2] where L is 2,2′‐bipyridine‐4,4′‐dicarboxylic acid and L′ is 2,2′‐bipyridine (1)2,2′‐bipyridine‐4,4′‐dicarboxylic acid (2), 4,4′‐dimethyl‐2,2′‐bipyridine (3), 4,4′‐diphenyl‐2,2′‐bipyridine (4), 1,10‐phenanthroline (5), and bathophenanthrolinedisulfonic acid (6) have been synthesized, and their spectral and electrochemical properties investigated. The two carboxylic functions on the 2,2′‐bipyridine ligand L serve as interlocking groups through which the dye is attached at the surface of TiO2 films having a specific surface texture. The role of these interlocking groups is to provide strong electronic coupling between the π* orbital of the 2,2′‐bipyridine and the 3d‐wave‐function manifold of the conduction band of the TiO2, allowing the charge injection to proceed at quantum yields close to 100 %. The charge injection and recombination dynamics have been studied with colloidal TiO2, using laser photolysis technique in conjunction with time‐resolved optical spectroscopy. Photocurrent action spectra obtained from photo‐electrochemical experiments with these trinuclear complexes cover a very broad range in the visible, making them attractive candidates for solar light harvesting. Monochromatic incident photon‐to‐current conversion efficiencies are strikingly high exceeding 80% in some cases. Performance characteristics of regenerative cells operating with these trinuclear complexes and ethanolic triiodide/iodide redox electrolyte have been investigated. Optimal results were obtained with complex 1 which gave a fill factor of 75 % and a power conversion efficiency of 11.3% at 520 nm.

ChemInform Abstract: Synthesis and Redox Properties of a Bipyridyl Analogue of Ruthenium Red.

AbstractThe trinuclear Ru(III), Ru(IV), Ru(III) complex (I) is prepared from dichlorobis(bipyridine)‐Ru(II) by Chloride abstraction, H2O2 oxidation, and by NaClO4 addition.