Kinetics and Photochemistry of Ruthenium Bisbipyridine Diacetonitrile Complexes: An Interdisciplinary Inorganic and Physical Chemistry Laboratory Exercise (original) (raw)
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Photosubstitution of ancillary ligands in octahedral mono-terpyridine ruthenium (II) complexes
Comptes Rendus de l'Académie des Sciences - Series IIC - Chemistry, 2000
A series of ruthenium (II)-terpyridine complexes incorporating mono-, bi-, and terdentate ligands were prepared and characterized by UV-visible and NMR spectroscopy and cyclic voltammetry. In acetonitrile solution, the complexes Ru(ttpy)(pypz)(CH 3 CN)(PF 6) 2 (1) and Ru(ttpy)(dmbp)(CH 3 CN)(PF 6) 2 (4) (ttpy= 4%-tolyl-2,2%:6%,2%%-terpyridine, pypz = 1-(2pyridyl)-3,5-dimethylpyrazole and dmbp =6,6%-dimethyl-2,2%-bipyridine) undergo photosubstitution of coordinated acetonitrile. In the case of 1, the photoproduct is the less constrained isomer. In the case of 4, a reversible photochemical interchange of the monodentate ligand (CH 3 CN and pyridine) occurs efficiently and quantitatively. This last complex could be used as a photoactive component in the construction of molecular switches based on photoactive rotaxanes. © 2000 Académie des sciences / Éditions scientifiques et médicales Elsevier SAS. ruthenium / photosubstitution / sterically hindered ligands / terpyridine Résumé-Réaction de photosubstitution de ligands ancillaires dans des complexes mono-terpyridinique octaédrique de ruthénium (II). Plusieurs complexes mono-terpyridine de ruthénium (II) incorporant des ligands mono-, bi-, et terdentate ont été préparés et caractérisés par spectroscopie UV-visible, RMN du proton et voltamétrie cyclique. Leur comportement photochimique a été étudié par spectroscopie UV-visible et RMN du proton. Dans l'acétonitrile, les complexes Ru(ttpy)(pypz)(CH 3 CN)(PF 6) 2 (1) et Ru(ttpy)(dmbp)(CH 3 CN)(PF 6) 2 (4) (ttpy = 4%-tolyl-2,2%:6%,2%%-terpyridine, pypz = 1-(2pyridyl)-3,5-diméthylpyrazole et dmbp =6,6%-diméthyl-2,2%-bipyridine) subissent une réaction de photosubstitution de l'acétonitrile coordonné. Dans le cas du complexe 1, la photosubstitution conduit à l'isomère le moins encombré. Dans le cas de 4, une réaction photochimique réversible d'échange du ligand monodentate (CH 3 CN et pyridine) a lieu d'une manière efficace et quantitative. Ce dernier complexe pourrait servir de centre photo-actif dans la construction d'interrupteurs moléculaires photo-induits fondés sur des rotaxanes.
Chemistry - A European Journal, 2005
To mimic the electron-donor side of photosystem II (PSII), three trinuclear ruthenium complexes (2, 2a, 2b) were synthesized. In these complexes, a mixed-valent dinuclear Ru2(II,III) moiety with one phenoxy and two acetato bridges is covalently linked to a Ru(II) tris-bipyridine photosensitizer. The properties and photoinduced electron/energy transfer of these complexes were studied. The results show that the Ru2(II,III) moieties in the complexes readily undergo reversible one-electron reduction and one-electron oxidation to give the Ru2(II,III) and Ru2(III,III) states, respectively. This could allow for photooxidation of the sensitizer part with an external acceptor and subsequent electron transfer from the dinuclear ruthenium moiety to regenerate the sensitizer. However, all trinuclear ruthenium complexes have a very short excited-state lifetime, in the range of a few nanoseconds to less than 100 ps. Studies by femtosecond time-resolved techniques suggest that a mixture of intramolecular energy and electron transfer between the dinuclear ruthenium moiety and the excited [Ru(bpy)3]2+ photosensitizer is responsible for the short lifetimes. This problem is overcome by anchoring the complexes with ester- or carboxyl-substituted bipyridine ligands (2a, 2b) to nanocrystalline TiO2, and the desired electron transfer from the excited state of the [Ru(bpy)3]2+ moiety to the conduction band of TiO2 followed by intramolecular electron transfer from the dinuclear Ru2(II,III) moiety to photogenerated Ru(III) was observed. The resulting long-lived Ru2(III,III) state decays on the millisecond timescale.
Inorganic Chemistry, 2007
This paper presents the synthesis, MO calculations, and photochemical and photophysical properties of cis-[Ru-(bpy) 2 (3Amdpy 2 oxaNBE)](PF 6) 2 (2), where bpy is 2,2′-bipyridine and 3Amdpy 2 oxaNBE is the novel 5,6-bis(3amidopyridine)-7-oxanorbornene chelate-ligand (1). Complex 2 is considered in relation to the cis-[Ru(bpy) 2-(3Amnpy) 2 ](PF 6) 2 (3) analogous complex, where 3Amnpy is 3-aminopyridine. Complexes 2 and 3 exhibit absorptions near 350 nm and in the 420−500 nm region attributable to a contribution from MLCT transitions (d π f bpy and d π f L; L) 3Amdpy 2 oxaNBE or 3Amnpy). Whereas complex 3 is photochemically reactive, complex 2 shows luminescence either at 77 K or at room temperature in fluid solution. The emission of 2 assignable as an MLCT (Ru f bpy) emission is characterized by a long lifetime at room temperature (650 ns in CH 3 CN and 509 ns in H 2 O). It is independent of λ irr , but it is temperature dependent; i.e., it increases as the temperature is lowered. Considering the chelate ring of 1 contributes to the stability of the complex 2 under continuous light irradiation, the difference in the primary photoprocesses of 3 (loss of 3Amnpy) and 2 (luminescence) may be caused by a lowering of the lowest excited state from 3 to 2. The surface crossing to the lowest MC state value of 987 cm-1 (similar to that of [Ru(bpy) 3 ] 2+) will be prevented in the case of complex 2, and as a result, efficient 3Amdpy moiety loss cannot occur. The electronic depopulation of the {Ru(bpy) 2 } unit and population of a bpy* orbital upon excitation are evident by comparing the photophysical properties with those of a [Ru(bpy) 3 ] 2+ related complex. Moreover, a reduction of a bpy ligand in the MLCT excited state is indicated by time-resolved spectra that show features typical of bpy •-. The photocatalytic property of 2 is spectroscopically demonstrated by oxidative quenching using either methylviologen 2+ or [RuCl(NH 3) 5 ] +2 electron-acceptor ions.
Journal of Photochemistry and Photobiology A: Chemistry, 2000
The chemistry and photophysics of a new ruthenium(II)-polypyridine complex, [Ru(bipy) 2 (Sbipy)] 2+ where bipy=2,2 -bipyridine and Sbipy=4,4 -dimethylthio-2,2 -bipyridine, have been investigated. In spite of the thioether substituents in the 4,4 positions of the 2,2 -bipyridine ligand, this complex behaves similarly to the [Ru(bipy) 3 ] 2+ complex, exhibiting strong charge-transfer bands at 450 nm, and luminescence emission at 630 nm (t 1/2 =0.91 s), at room temperature. The time resolved excited state spectrum was simulated using the open-shell ZINDO/S method, indicating a rather complex composition of metal-to-ligand, ligand-to-metal and ligand-to-ligand charge-transfer transitions. The thioether groups have been exploited as strong binding sites for pentacyanoferrate ions, allowing the generation of polynuclear species suitable for immobilization purposes, onto nickel electrode surfaces. Such Prussian blue type films displayed photoaction response to visible light in the presence of dissolved oxygen.