Metal-to-ligand charge-transfer (MLCT) photochemistry:  experimental evidence for the participation of a higher lying MLCT state in polypyridyl complexes of ruthenium(II) and osmium(II)

Lumpkin, Richard S.; Kober, Edward M.; Worl, Laura A.; Murtaza, Zakir; Meyer, Thomas J.

doi:10.1021/j100364a039

Cited by 203 publications

(232 citation statements)

References 0 publications

Supporting

Mentioning

218

Contrasting

Order By: Relevance

“…18 Similarly, the excited-state lifetime of Ru(bpy) 3 2+ within a cellulose acetate matrix is 914 ns, an increase in 300 ns from aqueous measurements. 15,19 Zeolite EMT provides a less restrictive environment for Ru(bpy) 3 2+ as shown by the 2 H NMR studies. The shorter lifetime of ambient Ru-EMT is ascribed to the availability of the 3 dd state and the temperature-dependent lifetime studies account for this by using two temperaturedependent terms.…”

Section: Discussionmentioning

confidence: 93%

Effect of Rotational Mobility on Photoelectron Transfer: Comparison of Two Zeolite Topologies

2003

View full text Add to dashboard Cite

Nuclear magnetic resonance (NMR) spectroscopy and time-resolved diffuse reflectance (TRDR) have been combined to study the effects of constrained rotational motion on the rates of photoinduced electron-transfer reactions within zeolites. By synthesizing tris(2,2′-bipyridine) ruthenium (II) [Ru(bpy) 3 2+ ] within the large cages of zeolites Y and EMT, it was possible to directly investigate the effect of zeolite cage size on molecular motion of Ru(bpy) 3 2+ and the influence of the cage size on the rate of intrazeolitic electron transfer. Deuterium solid-state NMR shows that zeolite Y imposes restraint on molecular rotation of Ru(bpy) 3 2+ , while zeolite EMT allows for motion. Temperature-dependent studies show the ability to freeze or induce motion of Ru-(bpy) 3 2+ within zeolite EMT while motion within zeolite Y remains unaffected, even at elevated temperatures. For zeolite EMT, an increase in the rate of the photoinduced forward and back electron transfer from Ru-(bpy) 3 2+ to methyl viologen was noted and correlated with access, rotational motion, and favorable orbital overlap. The overall photochemical charge separation efficiencies for the intrazeolitic Ru(bpy) 3 2+ -bipyridinium reactions were similar for both zeolites. IntroductionOne of the major obstacles in the development of artificial photosynthetic systems is that the thermal back-electron transfer reaction negates the utilization of photochemically created reactive redox species. 1 Thus, considerable effort is being made to understand the features that control electron-transfer dynamics. Toward that end, many donor-acceptor systems have been examined, and assembly of molecular units on microheterogeneous supports is being pursued to influence electron-transfer dynamics. 2 By virtue of the nature of microheterogeneous supports, the motion of molecules is modified and it is of interest to examine how electron transfer is influenced by such immobilization. Zeolites, because of the molecular size of their cavities, are an excellent host system to investigate immobilization phenomena.Zeolite Y consists of a regular network of sodalite cages in a tetrahedral arrangement resulting in 13 Å supercages with 7 Å windows (Figure 1a). 3 This is large enough to accommodate the luminescent molecule trisbipyridine ruthenium (II) [Ru-(bpy) 3 2+ ] which has a molecular diameter of 12 Å and can be assembled within the supercages by using a "ship-in-a-bottle" synthetic procedure. 4 These intrazeolitic ruthenium complexes can then be surrounded by bipyridinium ions such as methyl viologen (MV 2+ ) using the inherent ion-exchange properties of the zeolite. It has been shown that zeolite Y can promote longlived, Ru(bpy) 3 3+ -bipyridinium radical cation charge-separated states. 5,6 Molecular modeling of Ru(bpy) 3 2+ entrapped within zeolite Y indicated a significant number of contacts between the metal complex and the walls of the zeolite that were within the van der Waals radii of the atoms. 6 It was proposed that these contacts inhibit the rotational motion of the i...

show abstract

Section: Discussionmentioning

confidence: 93%

Effect of Rotational Mobility on Photoelectron Transfer: Comparison of Two Zeolite Topologies

2003

View full text Add to dashboard Cite

show abstract

“…These absorption and emission bands at wavelengths closer to the red in comparison to those of common iridium(III) complexes, and therefore in a more biologically transparent region of the spectrum, will also enable greater depth of penetration for excitation and imaging. Complexes of osmium(II) are also typically highly inert to ligand photosubstitution making them highly robust [34] (although the unprecedentedly facile ligand photoejection in the complex [Os(btz)3] 2+ was recently reported [35]). The intensity of phosphorescence is, however, sensitive to the presence of oxygen resulting in quenching through conversion of ground state 3 O2 to reactive 1 O2, thus enabling exploitation in photodynamic therapy (PDT) [36].…”

Section: Resultsmentioning

confidence: 99%

Towards Water Soluble Mitochondria-Targeting Theranostic Osmium(II) Triazole-Based Complexes

et al. 2016

View full text Add to dashboard Cite

Abstract:The complex [Os(btzpy) 2 ][PF 6 ] 2 (1, btzpy = 2,6-bis(1-phenyl-1,2,3-triazol-4-yl)pyridine) has been prepared and characterised. Complex 1 exhibits phosphorescence (λ em = 595 nm, τ = 937 ns, φ em = 9.3% in degassed acetonitrile) in contrast to its known ruthenium(II) analogue, which is non-emissive at room temperature. The complex undergoes significant oxygen-dependent quenching of emission with a 43-fold reduction in luminescence intensity between degassed and aerated acetonitrile solutions, indicating its potential to act as a singlet oxygen sensitiser. Complex 1 underwent counterion metathesis to yield [Os(btzpy) 2 ]Cl 2 (1 Cl ), which shows near identical optical absorption and emission spectra to those of 1. Direct measurement of the yield of singlet oxygen sensitised by 1 Cl was carried out (φ ( 1 O 2 ) = 57%) for air equilibrated acetonitrile solutions. On the basis of these photophysical properties, preliminary cellular uptake and luminescence microscopy imaging studies were conducted. Complex 1 Cl readily entered the cancer cell lines HeLa and U2OS with mitochondrial staining seen and intense emission allowing for imaging at concentrations as low as 1 µM. Long-term toxicity results indicate low toxicity in HeLa cells with LD50 >100 µM. Osmium(II) complexes based on 1 therefore present an excellent platform for the development of novel theranostic agents for anticancer activity.

show abstract

“…photocatalysts (Lumpkin, Kober, Worl, Murtaza & Meyer, 1990), features which make them desirable for incorporation into solar-energy conversion schemes. The title compound is isostructural with [Ru(bpy)3](PF6)2, the structure of which has been reported previously (Rillema & Jones, 1979).…”

Section: Methodsmentioning

confidence: 99%

Crystal and molecular structure of tris(2,2'-bipyridyl)osmium(II) bis(hexafluorophosphate)

Richter¹,

Scott²,

Brewer³

et al. 1991

Acta Crystallogr C

View full text Add to dashboard Cite

Experimental. [Os(bpy)3](PF6)2 (bpy = 2,2'-bipyridine) was prepared by a modification of the procedure of Burstall, Dwyer & Gyarfus (1950), and its properties have been reported elsewhere (Richter & Brewer, 1991). Recrystallization was accomplished using the technique of vapor diffusion (Stout & Jensen, 1968), with the compound dissolved in acetonitrile and using ether as the precipitating solvent. The crystals were large, thick, purple hexagons and had to be cut for the X-ray experiment.An irregularly shaped crystal with dimensions of 0.41 × 0.25 × 0.17 mm was selected for data collection on a Syntex P2~ diffractometer, with graphite monochromator, upgraded to Nicolet R3 specifications (Campana, Shepard & Litchman, 1981). The structure solution was obtained via the direct methods routine SOL V in the SHELJ(TL crystallo-

show abstract

Metal-to-ligand charge-transfer (MLCT) photochemistry: experimental evidence for the participation of a higher lying MLCT state in polypyridyl complexes of ruthenium(II) and osmium(II)

Cited by 203 publications

References 0 publications

Effect of Rotational Mobility on Photoelectron Transfer: Comparison of Two Zeolite Topologies

Effect of Rotational Mobility on Photoelectron Transfer: Comparison of Two Zeolite Topologies

Towards Water Soluble Mitochondria-Targeting Theranostic Osmium(II) Triazole-Based Complexes

Crystal and molecular structure of tris(2,2'-bipyridyl)osmium(II) bis(hexafluorophosphate)

Contact Info

Product

Resources

About