Zeeman splittings of the two lowest excited states of [Ru(bpy)3](PF6)2

doi:10.1016/0009-2614(90)80061-H

Chemical Physics Letters

Volume 171, Issues 1–2, 27 July 1990, Pages 122-126

https://doi.org/10.1016/0009-2614(90)80061-H Get rights and content

Abstract

For [Ru(bpy)₃](PF₆)₂, the splittings of the two lowest excited electronic states could be measured under magnetic fields (Zeeman effect). The splittings of both states increase with the magnetic-field strength to 3 ± 0.5 cm⁻¹ at B = 6 T. It is concluded that at B equal zero, the parent terms of these two states cannot be classified as originating from a situation in which one electron is localized on one ligand.

References (21)

E.M. Kober et al.
Inorg. Chem.
(1984)
M.L. Myrick et al.
J. Am. Chem. Soc.
(1988)
H. Yersin et al.
J. Am. Chem. Soc.
(1984)
H. Yersin et al.
J. Phys.
(1985)
E. Gallhuber et al.
XI IUPAC Symposium on Photochemistry, Lisbon
(1986)
T. Schönherr et al.
Chem. Phys. Letters
(1989)
R.W. Harrigan et al.
J. Chem. Phys.
(1973)
D.C. Baker et al.
Chem. Phys.
(1974)
E. Krausz
Chem. Phys. Letters
(1987)
E. Kraustz et al.
Progr. Inorg. Chem.
(1989)
P.G. Bradley et al.
J. Am. Chem. Soc.
(1981)

There are more references available in the full text version of this article.

Cited by (14)

Ultrafast relaxation dynamics of amine-substituted bipyridyl ruthenium(II) complexes
2017, Chemical Physics Letters
Citation Excerpt :
For ruthenium(II) polypyridyl complexes, the highest occupied molecular orbitals (HOMOs) are usually localized on the t2 orbital of ruthenium, while the lowest unoccupied molecular orbitals (LUMOs) have dominant contributions of the π∗ orbital of auxiliary ligands. The excited-state electron appears to be delocalized on all ligands in the initial 1MLCT excited-state followed by the charge localization onto the lowest-energy ligand [18–21]. Heteroleptic ruthenium(II) complexes exhibit complex photophysical properties because of the additional ligand-to-ligand charge-transfer transition (LLCT), and the interligand electron transfer is almost simultaneous with the vibrational cooling [22].
The excited state properties of a series of ruthenium(II) amine-substituted bipyridyl complexes, [Ru(bpy)_n(NNbpy)_3−n]²⁺, were investigated by steady-state and transient absorption spectroscopy, as well as quantum chemical calculations. The steady-state absorption spectra of these complexes in CH₃CN show a distinct red-shift of the ¹MLCT absorption with increasing numbers of amine substituent, whereas the emission spectra indicate an energy gap order of [Ru(bpy)₃]²⁺ > [Ru(bpy)₂(NNbpy)]²⁺ > [Ru(NNbpy)₃]²⁺ > [Ru(bpy)(NNbpy)₂]²⁺. Nanosecond, femtosecond transient absorption and electrochemical measurements suggest that NNbpy ligand has a strong influence on the electronic and emission properties of these complexes, due to electron-rich amine substituent. We illustrate how the numbers of amine substituent modulate the spectroscopic properties of transition metal complexes, which is related to the design of new electro-active systems with novel photoelectrochemical properties.
Energy transfer and harvesting in [Ru<inf>1-x</inf>Os<inf>x</inf>(bpy)<inf>3</inf>](PF<inf>6</inf>)<inf>2</inf> and {λ-[Ru(bpy)<inf>3</inf>]δ-[Os(bpy)<inf>3</inf>]} (PF<inf>6</inf>)<inf>4</inf>
2002, Coordination Chemistry Reviews
Citation Excerpt :
At low temperature, the emissions stem from substates of a 3MLCT term, while at r.t. also a thermally activated 1MLCT emission has been identified for rac-[Ru(bpy)3](PF6)2 [34,35]. The 3MLCT term splits according to the specific site symmetry of [Ru(bpy)3]2+ and according to spin–orbit coupling into several triplet substates (e.g. see [36–45]). In this outline, we do not discuss group-theoretical assignments, since a generally accepted classification has not yet emerged. (
{Λ-[Ru(bpy)₃]Δ-[Os(bpy)₃]}(PF₆)₄ is the first representative of a new class of materials. The crystal structure is built up of homochiral layers of Λ-[Ru(bpy)₃]²⁺ that alternate with homochiral layers of Δ-[Os(bpy)₃]²⁺. In this new material, the excitation energy is transferred efficiently by radiationless processes to one single crystallographic site of Δ-[Os(bpy)₃]²⁺ (site A), where the excitation energy is harvested. We develop an understanding of: (1) the different steps of energy transfer, (2) the dominating mechanisms (Förster and/or Dexter), and (3) the electronic states involved. Therefore, we study, typically at T=1.3 K, properties of the low-lying excited states and of energy transfer processes occurring in rac-[Ru(bpy)₃](PF₆)₂, [Ru_1−xOs_x(bpy)₃](PF₆)₂ (with x=0.01, 0.1, 0.2, and 1.0) and we compare the results to those obtained for {Λ-[Ru(bpy)₃]Δ-[Os(bpy)₃]}(PF₆)₄. It can be concluded for this latter compound that the different inter-layer and intra-layer steps of energy transfer to the lowest site of Δ-[Os(bpy)₃]²⁺ are dominated by efficient Dexter exchange processes. Due to energy accumulation at this lowest site, the new compound exhibits the interesting property of self-site-selectivity. This means, one obtains one-site emission spectra for every excitation wavelength from the UV to 693 nm. And since this lowest site of Δ-[Os(bpy)₃]²⁺ is well shielded from its environment, the spectra are highly resolved and thus reveal directly detailed properties of the low-lying electronic states and their vibronic coupling behavior. In particular, these properties depend strongly on an applied magnetic field. For example, with application of a field up to H=12 T, the intensity of the lowest electronic 0–0 transition can be tuned in and increased by several orders of magnitude. Simultaneously, the vibrational satellite structure is completely altered. We observe changes from a vibronically induced (Herzberg–Teller) structure to a structure dominated by Franck–Condon satellites. This property of Δ-[Os(bpy)₃]²⁺ is due to a magnetically induced coupling between lower lying triplet substates. Similar observations have not yet been reported for other compounds.
Low-lying electronic states of [Rh(bpy)<inf>3</inf>]3+, [Pt(bpy)<inf>2</inf>]2+, and [Ru(bpy)<inf>3</inf>]2+. A comparative study based on highly resolved and time-resolved spectra
1997, Coordination Chemistry Reviews
Optical emission and excitation spectra of [Rh(bpy-h₈)₃]³⁺, [Rh(bpy-h₈)₂(bpy-d₈)]³⁺, [Rh(bpy-d₈)₃]³⁺, [Pt(bpy-h₈)₂]²⁺, [Pt(bpy-h₈)(bpy-d₈)]²⁺, [Pt(bpy-d₈)₂]²⁺, [Ru(bpy-h₈)₃]²⁺, [Ru(bpy-h₈)₂(bpy-d₈)]²⁺, and (Ru(bpy-d₈)₃]²⁺ are discussed. A series of trends—also including [Os(bpy)₃]²⁺—is uncovered. These trends, which are connected with an increase in metal-d or MLCT character in the lowest triplet states, can for instance be seen in transition energies, emission lifetimes, zero-field splittings, rates of spin-lattice relaxation, vibronic satellite structures, and changes of nuclear equilibrium. positions on excitation. Moreover, the compounds investigated are also appropriate for consideration of the concept of “dual emission”, the relation between MLCT character and covalency, as well as the current models of localization/delocalization. In particular, a comparison of the properties of [Rh(bpy)₃]³⁺- and [Ru(bpy)₃]²⁺-doped [Zn(bpy)₃](ClO₄)₂ provides illustrative and very strong evidence for covalent delocalization in the lowest excited states of [Ru(bpy)₃]²⁺, while ligand-centered localization is found in the states of [Rh(bpy)₃]³⁺. Misinterpretations might occur if the aggregation effects of the chromophores are not taken into account.
Stark and Zeeman effects in the lowest excited states of [Zn(bpy)<inf>3</inf>](ClO<inf>4</inf>)<inf>2</inf>:Ru(II). Localized triplet metal-to-ligand charge transfer transitions
1994, Journal of Luminescence
Polarized absorption spectra of the metal-to-ligand charge transfer (MLCT) transitions in the title system are reported. Strong linear dichroisms are observed in accord with the crystal structure which shows that only two of the bpy ligands are crystallographically equivalent. The MLCT transitions to the third ligand are found to lie several hundred wavenumbers higher in energy. A strong angular dependence of the Zeeman effect in luminescence is observed when varying the direction of the magnetic field in the metal-ligand plane. These patterns are quantitatively analyzed in terms of localized transitions. The three lowest-excited electronic states are well described as the components of an orbitally non-degenerate spin triplet state with a very large zero field splitting. All three lowest-energy origins show the same large splitting in an applied electric field, confirming their charge-transfer nature. Luminescence and excitation line narrowing experiments establish that the splitting is a pseudo-Stark effect. Stark-swept transient hole-burning experiments provide a homogeneous line width of ≈ 15 MHz for the origin II in [Zn(bpy)₃](CIO₄)₂:Ru(II) at 1.8 K.
Orientational dependences of the Zeeman effect in the lowest-excited states of [Zn(bpy)<inf>3</inf>](ClO<inf>4</inf>)<inf>2</inf>:Ru(II) and [Ru(bpy)<inf>3</inf>](PF<inf>6</inf>)<inf>2</inf>
1994, Chemical Physics Letters
The positions and intensities of the electronic origins in [Zn(bpy)₃](ClO₄)₂:Ru(II) are strongly dependent on the orientation of an applied magnetic field within the metal—ligand plane. Spectra can be calculated by a model in which the lowest-energy charge-transfer excitations involve an individual metal—ligand subunit. The model can also reproduce all the significant features of the spectra reported for [Ru(bpy)₃](PF₆)₂.
Stark-swept transient hole burning and resonant luminescence line narrowing in [Zn(2,2′-bipyridine)<inf>3</inf>](ClO<inf>4</inf>)<inf>2</inf>:Ru(II)
1993, Chemical Physics Letters
Resonant luminescence line narrowing and Stark-swept transient hole-burning experiments were performed in the electronic origins of the lowest excited states of the title material. The energies of the two lowest excited states are well correlated. No fine structure was observed in the range 300 MHz–30 GHz for the resonantly and non-resonantly narrowed origin II and I, respectively. This is at variance with the interpretation of ODMR experiments. At 4.2 K an upper limit of ≈ 25 MHz is deduced for the homogeneous line width of origin II. A large pseudo-Stark splitting of the origins is observed corresponding to |Δμ| ≈ 5.5 D. This value is used to calibrate Stark-swept transient hole-burning experiments which needed ± 33 V/cm to measure the entire hole shape. A homogeneous line width of 14 ± 2 MHz is found for origin II at 1.5 K. The large Stark effect is the first direct evidence for the charge-transfer character of the lowest excited states in [Ru(bpy)₃]²⁺. The results are consistent with the localized nature of the lowest excited states.

View all citing articles on Scopus

¹: Present address: BASF AG, D-6700 Ludwigshafen, Federal Republic of Germany.

View full text

Article preview

Chemical Physics Letters

Abstract

References (21)

Inorg. Chem.

J. Am. Chem. Soc.

J. Am. Chem. Soc.

J. Phys.

XI IUPAC Symposium on Photochemistry, Lisbon

Chem. Phys. Letters

J. Chem. Phys.

Chem. Phys.

Chem. Phys. Letters

Progr. Inorg. Chem.

J. Am. Chem. Soc.

Cited by (14)

Ultrafast relaxation dynamics of amine-substituted bipyridyl ruthenium(II) complexes

Energy transfer and harvesting in [Ru<inf>1-x</inf>Os<inf>x</inf>(bpy)<inf>3</inf>](PF<inf>6</inf>)<inf>2</inf> and {λ-[Ru(bpy)<inf>3</inf>]δ-[Os(bpy)<inf>3</inf>]} (PF<inf>6</inf>)<inf>4</inf>

Low-lying electronic states of [Rh(bpy)<inf>3</inf>]<sup>3+</sup>, [Pt(bpy)<inf>2</inf>]<sup>2+</sup>, and [Ru(bpy)<inf>3</inf>]<sup>2+</sup>. A comparative study based on highly resolved and time-resolved spectra

Stark and Zeeman effects in the lowest excited states of [Zn(bpy)<inf>3</inf>](ClO<inf>4</inf>)<inf>2</inf>:Ru(II). Localized triplet metal-to-ligand charge transfer transitions

Orientational dependences of the Zeeman effect in the lowest-excited states of [Zn(bpy)<inf>3</inf>](ClO<inf>4</inf>)<inf>2</inf>:Ru(II) and [Ru(bpy)<inf>3</inf>](PF<inf>6</inf>)<inf>2</inf>

Stark-swept transient hole burning and resonant luminescence line narrowing in [Zn(2,2′-bipyridine)<inf>3</inf>](ClO<inf>4</inf>)<inf>2</inf>:Ru(II)