Excited State Redox Potentials of Ruthenium Diimine Complexes; Correlations with Ground State Redox Potentials and Ligand Parameters

Vlček, Antonı́n; Dodsworth, Elaine S.; Pietro, William J.; Lever, Annabelle

doi:10.1021/ic00111a043

Cited by 126 publications

(126 citation statements)

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“…While it is true that the ∆E 1/2 values do not quantitatively correspond to the relative emission energies of these complexes, it is important to remember that these electrochemical values neglect differences in charge repulsion and solvation energies, factors that are included in the D parameter. We have used the energy gap values obtained from spectral fitting (E 0 ) as a thermodynamic quantity similar to the E 00 parameter used by Lever 59 to give an estimation of the difference in MLCT energy gap predicted electrochemically and that observed spectroscopically. It can be expected that solvent reorganization energies will be larger in complexes with more solvent interaction, increasing the apparent E 00 value and decreasing the value of D. These and other subtle differences may be contributing to the incongruous D′ value seen for [Ru(dea) 3 ] 2+ .…”

Section: Resultsmentioning

confidence: 99%

Static and Time-Resolved Spectroscopic Studies of Low-Symmetry Ru(II) Polypyridyl Complexes

Curtright

McCusker

1999

J. Phys. Chem. A

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The spectroscopic and electrochemical properties of a series of four Ru II polypyridyl complexes are reported. Compounds of the form [Ru(dmb) x (dea) 3-x ] 2+ (x ) 0-3), where dmb is 4,4′-dimethyl-2,2′-bipyridine and dea is 4,4′-bis(diethylamino)-2,2′-bipyridine, have been prepared and studied using static and time-resolved electronic and vibrational spectroscopies as a prelude to femtosecond spectroscopic studies of excited-state dynamics. Static electronic spectra in CH 3 CN solution reveal a systematic shift of the MLCT absorption envelope from a maximum of 458 nm in the case of [Ru(dmb) 3 ] 2+ to 518 nm for [Ru(dea) 3 ] 2+ with successive substitutions of dea for dmb, suggesting a dea-based chromophore as the lowest-energy species. However, analysis of static and time-resolved emission data indicates an energy gap ordering of [Ru(dmb) , at variance with the electronic structures inferred from the absorption spectra. Nanosecond time-resolved electronic absorption and time-resolved step-scan infrared data are used to resolve this apparent conflict and confirm localization of the long-lived 3 MLCT state on dmb in all three complexes where this ligand is present, thus making the dea-based excited state unique to [Ru-(dea) 3 ] 2+ . Electrochemical studies further reveal the origin of this result, where a strong influence of the dea ligand on the oxidative Ru II/III couple, due to π donation from the diethylamino substituent, is observed. The electronic absorption spectra are then reexamined in light of the now well-determined excited-state electronic structure. The results serve to underscore the importance of complete characterization of the electronic structures of transition metal complexes before embarking on ultrafast studies of their excited-state properties.

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Section: Resultsmentioning

confidence: 99%

Static and Time-Resolved Spectroscopic Studies of Low-Symmetry Ru(II) Polypyridyl Complexes

Curtright

McCusker

1999

J. Phys. Chem. A

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“…These are MLCT in nature as evaluated from the longest-wavelength portions of absorption spectra ( 1 MLCT) and from the characteristics of the emission spectra ( 3 MLCT). [15] For instance, for [Ru(tpy) 2 ] 2 , the metal centred oxidation, E 1/2 ox (3+/2+), and the ligand centred reduction, E 1/2 red (2+/+), are +1.30 and -1.24 V, respectively, with respect to the SCE in MeCN. [16] The emission level, E em , is ca.…”

Section: Introductionmentioning

confidence: 99%

Luminescent Iridium(III)‐Terpyridine Complexes – Interplay of Ligand Centred and Charge Transfer States

et al. 2005

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Electrochemical properties, ground state absorption spectra, luminescence spectra and lifetimes (at room temperature and 77 K) as well as transient absorption spectra are reported herein for newly synthesized iridium(III) complexes in which benzamide units are appended to the coordinated terpyridine fragments. The nature of the luminescent excited states (Φ < 2 × 10–3 and τ in the microsecond range, in air‐equilibrated acetonitrile at 298 K) is discussed with regards to the ligand‐centred (3LC) or charge transfer (3CT) nature. At room temperature, the excited state, a predominantly ligand‐centred triplet (3LC) for the iridium(III) terpyridine compounds, is switched for the benzamide‐containing complexes to a charge transfer state (3CT). Intense absorption in the visible range, high energy content, long excited states lifetimes at 298 and 77 K and good luminescence yields make these complexes very promising as photosensitisers (P). The CT nature of the excited states of the benzamide‐containing complexes makes them ideal components for the construction of rigid, linear arrays of the Donor‐P‐Acceptor type for charge separation. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)

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“…The idea behind the studies has been based on the assumption, that the oxidation/reduction potential of a molecule corresponds to a "solution ionisation potential", and that there should be a direct relationship between oxidation/reduction potentials and HOMO/LUMO energies. Thermodynamic correlations between optical transition energies in complex molecules and the reduction/oxidation potentials, or differences thereof, were advocated over the past forty years in diverse reports (for some elegant studies, see refs [71][72][73][74][75][76][77][78][79][80][81][82][83][84][85][86][87]. The most extensive correlations of differences in redox potentials and energies of optical transitions have been derived for a number of Rh, Ru, Os, and Fe complexes.…”

Section: Combined Spectroscopic and Electrochemical Approach To Probimentioning

confidence: 99%

A Review on Molecular Electrochemistry of Metallocene Dichloride and Dimethyl Complexes of Group 4 Metals: Redox Properties and Relation with Optical Ligand-to-Metal Charge Transfer Transitions

Loukova

Strelets

2001

Collect. Czech. Chem. Commun.

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Emphasis is given to redox, photophysical, and photochemical properties of homologous bent metallocenes of group 4 transition metals. Comparative analysis of a variety of electron-transfer induced transformations and ligand-to-metal charge-transfer excited states is performed for bent metallocene complexes upon systematic variation of the identity of the metal ion (Ti, Zr or Hf), ancillary π- and monodentate σ- (Cl, Me) ligands. For such organometallic π-complexes, linear correlations exist between energies of optical and redox HOMO-to-LUMO electron transitions. It is suggested that combination of spectroscopic and electrochemical techniques provides important diagnostics to determine "ionisation potential" and "electron affinity" in solution (relative energies of frontier molecular orbitals obtained as redox potentials) and the energy gap in metallocene complexes. Some of earlier instructive cases of direct relationship between optical transition energies and differences in redox potentials revealed for inorganic and coordination compounds are discussed.

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Excited State Redox Potentials of Ruthenium Diimine Complexes; Correlations with Ground State Redox Potentials and Ligand Parameters

Cited by 126 publications

References 0 publications

Static and Time-Resolved Spectroscopic Studies of Low-Symmetry Ru(II) Polypyridyl Complexes

Static and Time-Resolved Spectroscopic Studies of Low-Symmetry Ru(II) Polypyridyl Complexes

Luminescent Iridium(III)‐Terpyridine Complexes – Interplay of Ligand Centred and Charge Transfer States

A Review on Molecular Electrochemistry of Metallocene Dichloride and Dimethyl Complexes of Group 4 Metals: Redox Properties and Relation with Optical Ligand-to-Metal Charge Transfer Transitions

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