Ruthenium-hydride-mediated stabilisation of the azo anion radical of azobis(benzothiazole) and its reversible electron-reservoir feature

Singh, Aditi; Seikh, Liton; Dey, Sanchaita; Lahiri, Goutam Kumar

doi:10.1039/d3nj04221a

Cited by 3 publications

(2 citation statements)

References 61 publications

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“…The expected forbidden (Δ M s = 2) half-field signal at g ∼ 4 for the triplet state of 1 -cis / 1- trans ( S = 1) could not be resolved, presumably due to the impact of a fast relaxation process at the experimental temperature of 77 K . The EPR profile in Figure also reflected partial resolution of nitrogen hyperfine splittings ( I = 1 for 14 N) …”

Section: Resultsmentioning

confidence: 93%

Sequential Oxygenation of Bis(β-diketiminate) on a Selective Diruthenium Platform

Seikh,

Sutradhar,

Dhara

et al. 2024

Inorg. Chem.

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This article demonstrated the redox-noninnocent phenylene-linked bis(β-diketiminate) (L2–)-bridged first example of isomeric diruthenium(III)-acac species (acac = acetylacetonate) and its ability to activate dioxygen. The coordination of deprotonated L2– to the {Ru(acac)2} in bis(bidentate) mode led to isomeric {(acac)2RuIII}2(μ-L2–) (S = 1, 1-trans/1-cis, green). 1 displayed Ru(III)-based anisotropic EPR in CH3CN but without the resolution of the forbidden (ΔM s = 2) g 1/2 signal at 77 K. 1-cis, however, slowly transformed to the energetically favored 1-trans form. 1 underwent two-step oxygenation at the Cβ sites of L2– to form the β-diketiminate/α-ketodiimine (L′ –)-bridged mixed valent (acac)2RuIII(μ-L′ –)RuII(acac)2 (2, S = 1/2, pink) followed by bis(α-ketodiimine) (L″)-bridged isovalent (acac)2RuII(μ-L″)RuII(acac)2 (3, S = 0, red). The role of O2 toward 1 → 2/3 was corroborated by 18O2 labeling experiment. Redox steps of 1–3 varied as a function of isomeric identity, bridge, and metal oxidation state. The calculated MOs and Mulliken spin densities attributed to the noninnocence of L2–, L′ –, and L″ in the respective complexes. Spectrophotometric monitoring of 1 → 2 revealed pseudo-first-order rate constants (105 k s–1) of 1.8 (303 K), 3.5 (313 K), 7.7 (323 K), and 17.0 (333 K) and ΔH ⧧/ΔS ⧧/ΔG ⧧ of 14.3 kcal mol–1/–33.1 cal mol–1 K–1/24.2 kcal mol–1 (298 K), respectively. Moreover, characterization of the short-lived blue intermediate obtained during the conversion of 1 → 2/3 upon exposure to O2 supported its valence tautomeric form ( VT 1, RuIII-L2–-RuIII ↔ RuIII-L•–-RuII, S = 1), which in effect facilitated oxygen activation at the ligand backbone.

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Section: Resultsmentioning

confidence: 93%

Sequential Oxygenation of Bis(β-diketiminate) on a Selective Diruthenium Platform

Seikh,

Sutradhar,

Dhara

et al. 2024

Inorg. Chem.

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“…The reasonably upfield shifted 31 P signal in Ru–Cl-bound 6 (δ, 30 ppm) with regard to the Ru–H-bound [ 7 ]ClO 4 /[ 8 ]ClO 4 (δ, 42–46 ppm) was also reflected in the corresponding Ru–P bond distances (Table ). , The ν(CO)/H and ν(ClO 4 ) bands of the complexes appeared at ≈1940 and ≈1100 cm –1 , respectively (Experimental Section and Figure S14 in the Supporting Information).…”

Section: Resultsmentioning

confidence: 99%

Diverse Coordination Modes and Bidirectional Noninnocence of Pyridyl-β-diketonate on Ruthenium Platforms as a Function of Coligands

Biswas,

Mobin,

Dey

et al. 2024

Inorg. Chem.

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The article demonstrated diverse binding modes of deprotonated 1,3-di(2-pyridinyl)-1,3-propanedione (HL) (κ2-[O,O]−, κ2-[N,O]−, and μ-bis-κ2-[N,O]−) on selective ruthenium platforms: Ru(acac)2 (dimeric [1]ClO4), Ru(bpy)2 (monomeric [2]ClO4), Ru(pap)2 (isomeric monomeric [3]ClO4/[4]ClO4, dimeric [5](ClO4)3), and Ru(PPh3)2(CO) (monomeric 6, isomeric dimeric [7]ClO4/[8]ClO4) (acac = acetylacetonate, bpy = 2,2′-bipyridine, pap = 2-phenylazopyridine). Structural authentication of the complexes revealed (i) diverse binding mode of L– including its unprecedented bridging mode in [8]ClO4, (ii) varying degrees of nonplanarity of L–, and (iii) development of 1D polymeric chains or dimeric/tetrameric forms via intermolecular π–π interactions. The preferential binding feature of L– in the complexes could also be corroborated by their calculated relative energies. The analysis of the multiredox steps of the complexes suggested severe mixing of metal–ligand frontier orbitals, which in effect pinpointed the involvement of L– in both the oxidative and reductive processes along the redox chain, suggesting its bidirectional noninnocence under the present coordination situations. Though α-diketone or β-diketiminate was reported to activate O2 on the selective Ru(acac)2 platform, the inability of analogous β-diketonate-derived [1]ClO4 could be attributed to its calculated greater HOMO–LUMO energy gap, which disfavored electron exchange at the metal(RuIII)–ligand(L – ) interface to introduce the required unpaired spin at the ligand backbone toward the 3O2 activation event.

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Fine Tuning between Radical versus Nonradical States of Azoheteroarenes on Selective Osmium Platforms

Seikh,

Dhara,

Shukla

et al. 2024

Inorg. Chem.

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Ruthenium-hydride-mediated stabilisation of the azo anion radical of azobis(benzothiazole) and its reversible electron-reservoir feature

Abstract: Homolytic cleavage of the RII–H bond of A in contact with L facilitates the formation of H2 and L˙− derived 1–3, which undergo reversible electron exchange between 1–3 and 1+–3+.

Cited by 3 publications

References 61 publications

Sequential Oxygenation of Bis(β-diketiminate) on a Selective Diruthenium Platform

Sequential Oxygenation of Bis(β-diketiminate) on a Selective Diruthenium Platform

Diverse Coordination Modes and Bidirectional Noninnocence of Pyridyl-β-diketonate on Ruthenium Platforms as a Function of Coligands

Fine Tuning between Radical versus Nonradical States of Azoheteroarenes on Selective Osmium Platforms

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