Properties and dynamics of the σ(M′-Re)π∗ excited state of photoreactive dinuclear LnM′-Re(CO)3(α-diimine) (LnM′ = Ph3Sn, (CO)5Mn, (CO)5Re; α-diimine = bpy′, iPr-PyCa, iPr-DAB) complexes studied by time-resolved emission and absorption spectroscopies

Rossenaar, Brenda D.; Lindsay, Elspeth; Stufkens, Derk J.; Vlček, Antonı́n

doi:10.1016/s0020-1693(96)05203-6

Cited by 50 publications

(23 citation statements)

References 49 publications

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“…The resulting multiconfigurational species can be described as a high-spin Ni(II) with antiferromagnetically coupled electrons on the bpy and phenyl ligands (see the Supporting Information Tables S1Q-R and S2M-N for more details). Interestingly, this description of excited state bond homolysis is conceptually similar to that given for the mixed MLCT/σπ* (sigma bond to ligand charge transfer) photoinduced radical formation in Re(I) and Ru(II) complexes. − Overall, this represents a novel homolytic bond dissociation mechanism in nickel catalysis, which we propose derives from the redox noninnocent and multiconfigurational ground and excited state bonding in Ni(II)-bpy complexes.…”

Section: Resultssupporting

confidence: 70%

Multireference Description of Nickel–Aryl Homolytic Bond Dissociation Processes in Photoredox Catalysis

et al. 2020

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Multireference electronic structure calculations consistent with known experimental data have elucidated a novel mechanism for photo-triggered Ni(II)-C homolytic bond dissociation in Ni 2,2'bipyridine (bpy) photoredox catalysts. Previously, a thermally assisted dissociation from the lowest energy triplet ligand field excited state was proposed and supported by density functional theory (DFT) calculations that reveal a barrier of ~30 kcal mol-1. In contrast, multireference ab initio calculations suggest this process is disfavored, with barrier heights of ~70 kcal mol-1 , and highlight important ligand noninnocent contributions to excited state relaxation and bond dissociation processes that are not captured with DFT. In the multireference description, phototriggered Ni(II)-C homolytic bond dissociation occurs via initial population of a singlet Ni(II)-tobpy metal-to-ligand charge transfer (1 MLCT) excited state followed by intersystem crossing and aryl-to-Ni(III) charge transfer, overall a formal two-electron transfer process driven by a single photon. This results in repulsive triplet excited states from which spontaneous homolytic bond dissociation can occur, effectively competing with relaxation to the lowest energy, nondissociative triplet Ni(II) ligand field excited state. These findings guide important electronic structure considerations for the experimental and computational elucidation of the mechanisms of ground and excited state cross-coupling catalysis mediated by Ni heteroaromatic complexes.

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Section: Resultssupporting

confidence: 70%

Multireference Description of Nickel–Aryl Homolytic Bond Dissociation Processes in Photoredox Catalysis

et al. 2020

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“…The discovery and exploration of this so-called σ π* or sigma-bond-to-ligand charge transfer (SBLCT) transition, 10,11 is relatively recent. The properties of this transition and excited state have been studied in detail for several d 6 transition metal complexes, such as [Re(L)(CO) 3 (α-diimine)] (L = alkyl, metal fragment), [12][13][14][15] and [M(L 1 )(L 2 )(CO) 2 (α-diimine)] (M = Ru, Os; L 1 , L 2 = e.g. CH 3 , SnPh 3 , Mn(CO) 5 , RuCp(CO) 2 , etc.).…”

Section: Introductionmentioning

confidence: 99%

Influence of the variation of the co-ligands on the electronic transitions and emission properties of [Pt(I)(CH3)3(iPr-DAB)], [Pt(CH3)4(α-diimine)] and [Pt(SnPh3)2(CH3)2(iPr-DAB)]: an experimental and theoretical study

Slageren

Stufkens

Záli

et al. 2001

J. Chem. Soc., Dalton Trans.

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This paper reports the results of a combined spectroscopic (UV/Vis, resonance Raman, emission) and theoretical study of [Pt(I)The difference in character between the halide-to-ligand charge transfer (XLCT; X = I) transition of [Pt(I)(CH 3 ) 3 (iPr-DAB)] and the sigma-bond-to-ligand charge transfer (SBLCT) transitions of the other complexes, is clearly established by resonance Raman (rR) spectroscopy. DFT MO calculations confirm the assignment of the frontier orbitals and lowest-energy electronic transitions, and support the interpretation of the rR spectra. All complexes emit at low temperatures, with excited state lifetimes strongly depending on the character and reactivity of the lowest excited state.

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“…In this state, one electron has been transferred from the σ(Ru-Os2) bonding orbital (vide supra) to the lowest π* orbital of the iPr-AcPy ligand. Such absorptions are characteristic for complexes in metal-to-α-diimine excited states [49][50][51][52] and for α-diimine radical anions contain-ing at least one aromatic group. [49,53,54] The remaining transient absorption in 2-ClBu is very similar to that observed in the ns TA spectra of 3 (vide infra) and is assigned to the biradical [ · Os(CO) 4 -Os(CO) 4 -+ Ru(CO) 2 (α-diimine ·-)], in accordance with the results for [Os 3 (CO) 10 (iPr-AcPy)].…”

Section: Time-resolved Absorption Spectroscopy Of Cluster 3 In Noncoomentioning

confidence: 99%

“…As stated above, the transient absorption is characteristic for α-diimine radical anions [49][50][51][52] and for α-diimine complexes in their metal-to-α-diimine excited state, provided the α-diimine ligand bears at least one heteroaromatic group. [49,53,54] As the ns TA spectra closely resemble those of [Os 3 (CO) 10 (iPr-AcPy)] in acetone, [15] the transient absorption is again assigned to the open-structure biradical [ · Os(CO) 4 -Os(CO) 4 -+ Ru(Sv)(CO) 2 (iPr-AcPy ·-)] (Sv = acetone).…”

Section: Time-resolved Absorption Spectroscopy Of Cluster 3 In Noncoomentioning

confidence: 99%

Heterosite Effects in Novel Heteronuclear Clusters [Os₂Ru(CO)₁₁(PPh₃)] and [Os₂Ru(CO)₁₀(2‐acetylpyridine‐N‐isopropylimine)]

et al. 2005

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A new synthetic route towards the mixed-metal cluster [Os 2 -Ru(CO) 12 ] is described together with the syntheses of its PPh 3 and iPr-AcPy (iPr-AcPy = 2-acetylpyridine-N-isopropylimine) derivatives. The molecular structures of the novel clusters [Os 2 Ru(CO) 11 (PPh 3 )] and [Os 2 Ru(CO) 10 (iPr-AcPy)] were determined on the basis of crystalline solid solutions of the Os 2 Ru and corresponding Os 3 species. The structures reveal that coordination of the Lewis bases occurs exclusively at the ruthenium site of [Os 2 Ru(CO) 12 ], which is in agreement with density functional theory (DFT) calculations on several structural isomers of these compounds. According to the time-dependent DFT results, the lowest optically accessible excited state of [Os 2 Ru(CO) 10 (iPr-AcPy)] has a prevailing σ(Ru-Os2)-π*(iPr-AcPy) character, with a partial σσ*(Ru-Os2) contribution. In weakly coordinating 2-chlorobutane, the excited state has a lifetime τ = 10.4 ± 1.2 ps and produces biradicals considerably faster than observed for [Os 3 (CO) 10 (iPr-AcPy) (τ = 25.3 ± 0.7 ps). In coordinating acetonitrile, the excited state of [Os 2 Ru(CO) 10 (iPr-AcPy)] decays mono-exponentially with a lifetime τ = 2.1 ± 0.2 ps. In contrast to [Os 3 (CO) 10 (iPr-AcPy)]

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Properties and dynamics of the σ(M′-Re)π∗ excited state of photoreactive dinuclear LnM′-Re(CO)3(α-diimine) (LnM′ = Ph3Sn, (CO)5Mn, (CO)5Re; α-diimine = bpy′, iPr-PyCa, iPr-DAB) complexes studied by time-resolved emission and absorption spectroscopies

Cited by 50 publications

References 49 publications

Multireference Description of Nickel–Aryl Homolytic Bond Dissociation Processes in Photoredox Catalysis

Multireference Description of Nickel–Aryl Homolytic Bond Dissociation Processes in Photoredox Catalysis

Influence of the variation of the co-ligands on the electronic transitions and emission properties of [Pt(I)(CH3)3(iPr-DAB)], [Pt(CH3)4(α-diimine)] and [Pt(SnPh3)2(CH3)2(iPr-DAB)]: an experimental and theoretical study

Heterosite Effects in Novel Heteronuclear Clusters [Os₂Ru(CO)₁₁(PPh₃)] and [Os₂Ru(CO)₁₀(2‐acetylpyridine‐N‐isopropylimine)]

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Properties and dynamics of the σ(M′-Re)π∗ excited state of photoreactive dinuclear LnM′-Re(CO)3(α-diimine) (LnM′ = Ph3Sn, (CO)5Mn, (CO)5Re; α-diimine = bpy′, iPr-PyCa, iPr-DAB) complexes studied by time-resolved emission and absorption spectroscopies

Cited by 50 publications

References 49 publications

Multireference Description of Nickel–Aryl Homolytic Bond Dissociation Processes in Photoredox Catalysis

Multireference Description of Nickel–Aryl Homolytic Bond Dissociation Processes in Photoredox Catalysis

Influence of the variation of the co-ligands on the electronic transitions and emission properties of [Pt(I)(CH3)3(iPr-DAB)], [Pt(CH3)4(α-diimine)] and [Pt(SnPh3)2(CH3)2(iPr-DAB)]: an experimental and theoretical study

Heterosite Effects in Novel Heteronuclear Clusters [Os2Ru(CO)11(PPh3)] and [Os2Ru(CO)10(2‐acetylpyridine‐N‐isopropylimine)]

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Heterosite Effects in Novel Heteronuclear Clusters [Os₂Ru(CO)₁₁(PPh₃)] and [Os₂Ru(CO)₁₀(2‐acetylpyridine‐N‐isopropylimine)]