Emission band shape probes of the mixed-valence excited state properties of polypyridyl-bridged bis-ruthenium(II) complexes

Near-IR Charge-Transfer Emission at 77 K and Density Functional Theory Modeling of Ruthenium(II)-Dipyrrinato Chromophores: High Phosphorescence Efficiency of the Emitting State Related to Spin–Orbit Coupling Mediation of Intensity from Numerous Low-Energy Singlet Excited States

“…The experimentally determined photophysical parameters of the reference Ru-bpy complexes in this work were previously reported and are summarized in Table S2B (page S27). ,, Each low-energy intense absorption curve of the reference complexes, ranging from 18,000 to 25,000 cm –1 , is the sum of numerous MLCT­(Ru-dπ/bpy-π*) excited states. ,− ,, For the [Ru­(bpy) 2 (R-dipy)] + complexes, the low-energy intense band ranging from 15,000 to 20,000 cm –1 in the spectra of these complexes is considered to be MLCT transition, including Ru-dπ/bpy-π* and Ru-dπ/dipy-π* excited-state components, and the very intense absorption maxima at the 21,700–21,800 cm –1 region (≈458–460 nm) can be attributed to π–π* transitions of the dipyrrinato moiety. , Relatively narrow 77 K emission bands with structural emission vibronic sideband features have been reported previously for the reference Ru-bpy chromophores. ,− The broad 77 K emission bands in the spectra of the [Ru­(bpy) 2 (R-dipy)] + complexes in Figure do not have resolved vibronic sidebands, unlike those of the Ru-bpy chromophores.…”

“…65,66,68 Each low-energy intense absorption curve of the reference complexes, ranging from 18,000 to 25,000 cm −1 , is the sum of numerous MLCT(Ru-dπ/bpy-π*) excited states. 20,[65][66][67]69,103 For the [Ru(bpy) 2 (R-dipy)] + complexes, the low-energy intense band ranging from 15,000 to 20,000 cm −1 in the spectra of these complexes is considered to be MLCT transition, including Ru-dπ/bpy-π* and Ru-dπ/dipy-π* excited-state components, and the very intense absorption maxima at the 21,700−21,800 cm −1 region (≈458−460 nm) can be attributed to π−π* transitions of the dipyrrinato moiety. 84,101 Relatively narrow 77 K emission bands with structural emission vibronic sideband features have been reported previously for the reference Ru-bpy chromophores.…”

Influence of the “Innocent” Ligands on the MLCT Excited-State Behavior of Mono(bipyridine)ruthenium(II) Complexes: A Comparison of X-ray Structures and 77 K Luminescence Properties

“…For ruthenium polypyridyl complexes, E 00 ‘ (or E 0 ‘ 0 ) is a dominant component of the absorption (or emission spectrum), and the contributions from the reorganizational energies, λ r , contribute to the component bandwidth and to the shape of the spectral band in the [Ru(L) 4 bpy] 2+ (where bpy = 2,2-bipyridine) complexes. ,,,− However, extracting the information about either E 00 ‘ or λ r from the absorption (or E 0 ‘ 0 from the emission) spectra of species in ambient solutions is complicated by intrinsically large bandwidths, and the band-shape analysis of the absorption spectra is often further complicated by the overlapping contributions of different electronic transitions. On the other hand, transition-metal complex emission spectra generally correspond to a single electronic transition of the lowest-energy electronic excited state, ,− and approaches have recently evolved for evaluating the variations of electron-transfer parameters within a series of closely related complexes by means of the careful comparison of the shapes of the relatively broad band 77 K emission spectra of [Ru(Am) 6 - 2 n (bpy) n ] 2+ complexes in frozen solutions. ,, The analysis of the band shapes of these complexes is facilitated by removing from the experimental spectrum the dominant contribution of the fundamental component, which corresponds to the {e, 0‘} → {g, 0} transition, I max( f ) , and comparing either (a) the difference spectra, I ν m (diff) , which correspond to the sums of the spectral intensities of the components of all of the vibronic progressions, or (b) a reorganizational energy profile constructed by multiplying the normalized difference spectrum, I ν m (diff) ÷ I max( f ) , by the spectral frequency difference from the fundamental (with a generally small correction for the non-Gaussian shapes of the vibrational reorganizational energy contributions) to obtain a profile whose amplitude varies as the sum of the overlapping reorganizational energy contributions of the displacement modes. ,,− The latter approach is the most sensitive to variations in the reorganizational energies in a series of complexes because I ν m (diff) does not directly reflect variations in the electron-transfer reorganizational energies. Thus, the intensity contributions to the emission or difference spectrum of each of the first-order components in the vibronic progressions are given by , A more direct measure of the reorganizational energy information can be based on rearranging eq 1, or…”

Chemical Scavenging Yields for Short-Lived Products from the Visible Light Photoionization of the Tris(bipyridine)ruthenium(II) Triplet Metal-to-Ligand Charge-Transfer Excited State

“…The [tris­(1,10-phenanthroline)­ruthenium­(II)] hexafluorophosphate (95% purity) was purchased from Strem Chemical Inc. The bis-{bis­(bipyridine)­ruthenium­(II)}­(2,3-dipyridylpyrazine)­ruthenium­(II) hexafluorophosphate complex, [{Ru­(bpy)} 2 (dpp)] 4+ , was synthesized as reported previously …”