Synthesis, electrochemistry and photophysics of rigid norbornylogous-bridged complexes of ruthenium and osmium

Gulyas, Peter T.; Smith, Trevor A.; Paddon‐Row, Michael N.

doi:10.1039/a809015g

Cited by 22 publications

(11 citation statements)

References 64 publications

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“…In covalently linked systems aliphatic spacers are known to lead to a slower rate of energy-transfer than conjugated spacers. [16][17][18][19][20][21][22] However, in most of those cases the spacer affects the spatial disposition of the photoactive centers, whereas in our case this factor is eliminated.…”

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confidence: 99%

Vectorial Control of Energy‐Transfer Processes in Metallocyclodextrin Heterometallic Assemblies

et al. 2003

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In recent years, the importance of miniature photomolecular devices in nanoscale technology has led to the design of polymetallic supramolecular assemblies. [1][2][3] The employment of polyelectronic metal centers in a single supramolecular structure provides the basis for the development of molecular energy-conversion systems and wires in macromolecular systems. [4][5][6][7] Multistep reactions are usually required to link metallic building blocks together by means of covalent bonds; such multistep processes result in poor yields and synthetic complexity. Noncovalently assembled systems, in contrast, may allow control of the photoinduced processes by a simple choice of the assembled photoactive components. The noncovalent assembly of units in water presents other opportunities, not only to mimic natural processes, but also to provide easily accessible architectures. Self-assembled systems between ruthenium-bipyridine centers and various electron or energy acceptors have recently attracted much interest. [8][9][10] We are interested in studying photoinduced processes between metal units assembled in water through noncovalent interactions. We have previously introduced photoactive metals onto cyclodextrin rims for the assembly of photoactive units brought together by the cyclodextrin cavity. [11][12][13][14] Herein, we present a ruthenium tris(bipyridyl) cyclodextrin "wheel", [Ru(b-CD-mbpy) 3 ] 2+ (1; b-CD-mbpy = 6-mono[4-methyl(4'-dimethyl-2,2'-bipyridyl] permethylated b-cyclodextrin which was isolated as the PF 6 salt 1-(PF 6 ) 2 and which could be converted into the Cl salt 1-Cl 2 to enhance its solubility) that acts as both energy donor and acceptor leading to a versatile system for communication between the inner metal core and the outer guest unit by energy transfer; metal-complex guests based on osmium(ii) and iridium(iii) terpyridine species with biphenyl or adamantyl tails attached to one of the ligands have been employed to examine the importance of the included tail in the photoinduced process (Figure 1).Compound 1, is an attractive luminescent receptor molecule with three cyclodextrin cups available for recognition. Solutions of 1 in water with 10 % acetonitrile exhibit luminescence at room temperature at 622 nm (F = 0.027, t aerated = 460 ns, t degassed = 640 ns) upon excitation at the metalto-ligand charge transfer (MLCT) band at 436 nm. Comparison of the photophysical properties of this complex with the parent complex [Ru(mbpy) 3 ][PF 6 ] 2 , (mbpy = 4,4'-dimethyl-2,2'-bipyridine) which bears no cyclodextrins, indicates that cyclodextrin substitution does not have a significant effect.Osmium(ii)-based guests, have been employed to play the role of energy acceptors whereas iridium(iii)-based guests were used as energy donors for the Ru II center. The guests have hydrophobic biphenyl and adamantyl tails to ensure high binding constants in the cyclodextrin cavity. The nature of the hydrophobic tail, aliphatic versus aromatic, is selected to examine its effect in the photoinduced processes. Considerin...

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Vectorial Control of Energy‐Transfer Processes in Metallocyclodextrin Heterometallic Assemblies

et al. 2003

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“…p* transitions. Assignments of the absorption bands of the complexes were made on the basis of the well-documented optical transitions of analogous Ru(II) polypyridyl complexes [23][24][25][26]. The absorption spectra of the complexes both show three well-resolved bands.…”

Section: Absorption Spectroscopymentioning

confidence: 99%

Synthesis, photophysical, and electrochemical properties of two polynuclear ruthenium(II) polypyridyl complexes containing diazafluorene

Cheng

Chen

Wang

et al. 2011

Transition Met Chem

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Two polypodands, tetrakis[2-(4,5-diazafluoren-9-ylimino)phenoxymethyl]methane (L 1 ) and 1,1,1-tris[2-(4,5-diazafluoren-9-ylimino)phenoxymethyl]propane (L 2 ), and their corresponding Ru(II) polypyridyl complexes have been synthesized and characterized. The photophysical behaviors of the two complexes were investigated by UV-vis absorption and emission spectroscopy. They display metal-to-ligand charge transfer (MLCT) absorptions at around 443 nm in MeCN solution at room temperature and emission at around 573 nm in EtOH:MeOH (4:1) glassy matrix at 77 K. Electrochemical studies of the two complexes show one Ru(II)-centered oxidation at around 1.35 V and three ligand-centered reductions.

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“…Energy transfer was also observed in a dinuclear (Ru-L-Os) complex involving a bridge comprising two dipyridoquinoxaline ligating groups joined by the same linkage. 17 In the present study, variation of the alicyclic linkage has allowed assessment of the effects of orientation and relative displacement of the components in the transfer processes, and also the effect of solvent variation has been probed. It should also be noted that the ligand quencher and ligand bridges do not involve N-heterocycle moieties in the spacer: in earlier studies involving ligands such as dppz {dipyrido[3,2:a-2Ј,3Ј:c]phenazine}, these have been shown to affect the photophysical behaviour because of protonation reactions.…”

Section: Photophysical Studiesmentioning

confidence: 99%

“…The absorption and emission maxima of these systems appear to be solvent independent (see details given in the Experimental section), and the zerozero excitation energy (E 00 ) can be estimated from the emission maxima of related complexes recorded in a low temperature glass to be approximately 2.16 eV. 17 Using the electrochemical data, ∆G in acetonitrile for compound 3 is calculated to be approximately Ϫ0.10 V indicating that photoinduced electron transfer is thermodynamically favoured. The rates of electron transfer calculated (Table 1) will be influenced by the electronic coupling between the donor and acceptor (i.e.…”

Section: Photophysical Studiesmentioning

confidence: 99%

“…[13][14][15][16] However only limited photophysical data currently exist on the luminescent transition metal complexes prepared from such ligands. 11b,15, 17 We now report the use of these systems to probe the effectiveness of alicyclic structures in mediating electron and energy transfer processes in inorganic systems, principally those based on d 6 polypyridyl metal complexes.…”

Section: Introductionmentioning

confidence: 99%

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Electron and energy transfer within dyads involving polypyridyl-ruthenium(II) and -osmium(II) centres separated by rigid alicyclic bridges

Kelso

Smith

Schultz

et al. 2000

J. Chem. Soc., Dalton Trans.

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Rigid alicyclic frameworks (often referred to as molracs, relating to the molecular rack nature of the frame) have been used to vary the separation between organic electron-acceptor (quinone) moieties and chromophoric polypyridylruthenium() centres, and between metal centres in Ru-Ru and Ru-Os dinuclear complexes. Photophysical studies have allowed a preliminary insight into the effectiveness of such alicyclic structures in mediating intramolecular photoinduced energy and electron transfer. In the chromophore-spacer-quinone dyads, solventdependent quenching of the ruthenium() MLCT emission was observed and attributed to electron transfer processes. Distance and stereochemical dependencies of the quenching suggested that through-bond coupling was a factor in these systems. In the heterodinuclear systems, the photo-excited ruthenium() chromophore underwent intramolecular energy transfer to the osmium() component. A through-space Förster dipole-dipole mechanism could adequately account for the rate of the energy transfer process observed.

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Synthesis, electrochemistry and photophysics of rigid norbornylogous-bridged complexes of ruthenium and osmium

Cited by 22 publications

References 64 publications

Vectorial Control of Energy‐Transfer Processes in Metallocyclodextrin Heterometallic Assemblies

Vectorial Control of Energy‐Transfer Processes in Metallocyclodextrin Heterometallic Assemblies

Synthesis, photophysical, and electrochemical properties of two polynuclear ruthenium(II) polypyridyl complexes containing diazafluorene

Electron and energy transfer within dyads involving polypyridyl-ruthenium(II) and -osmium(II) centres separated by rigid alicyclic bridges

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