Diosmium compounds containing bis(imidazole)-<i>p</i>-quinone bridging ligands

Dhara, Suman; Ansari, Mohd. Asif; Schwederski, Brigitte; Filippou, Vasileios; Kaim, Wolfgang; Lahiri, Goutam Kumar

doi:10.1039/d2dt00184e

Cited by 11 publications

(13 citation statements)

References 34 publications

(25 reference statements)

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“…On the contrary, no such variation in the binding mode of L2 2– was evident as a function of osmium metal precursors Os(bpy) 2 ( 8 ) and Os(pap) 2 ( 9 ), and the bidentate N – ,O – donating mode of L2 2– was systematically stabilized as in 5 (Figure ). The average Os II -N(L2 2– ): 2.075(4) Å, Os II -O(L2 2– ): 2.084(5) Å and Os II -N(bpy/pap): 2.042(4)/2.016(8) Å distances were in good agreement with those of the reported analogous systems . The dπ–pπ interaction (back-bonding) between Ru II /Os II and the low-lying π*(azo) orbitals of pap in [ 7 ](ClO 4 ) 2 and 9 , respectively, was also reflected in the relevant MN(azo, pap)/NN (pap) distances as in the case of 2 or 4 (Table S2, Supporting Information) …”

Section: Resultssupporting

confidence: 82%

“…The multiple stepwise reductions of M II -L 2– (MRu/Os, L = L1 2– or L2 2– or L2′ 2– ) complexes were essentially associated with the pap (azo) or bpy (diamine)-based orbitals (Scheme S1, Supporting Information). The radical-based EPR of the first reduced state (R1, Figure ) of 4 – , 7 + , and 9 – ( S = 1/2, Figure ) also corroborated the same. , The two-electron reduced triplet state of 2 2– (R2, Figure , S = 1) expectedly displayed a radical EPR at g = 1.996 but without any forbidden half-field signal at g ≈ 4, possibly due to the fast relaxation process at 110 K …”

Section: Resultssupporting

confidence: 65%

“…As in 2 , longer Os II -N (pyridine, pap, 2.022(5) Å)/NN (pap, 1.309(7) Å) distances in 4 than in the corresponding Os II -N (azo, pap, 1.982(5) Å)/NN of free pap (1.258(5) Å) justified Os II → π* (azo) back-bonding. Further, shorter Ru II -N/Os II -N (pyridine, pap, average: 2.039(5) Å/2.022(5) Å) bond distances compared to the distances of Ru II -N/Os II -N (pyridine, bpy, average: 2.097(3) Å/2.043(5) Å) reaffirmed a stronger π-accepting feature of pap . The Ru II -O distances in [ 1 ]ClO 4 / 2 (2.106(3)/2.079(4) Å) and the Os II -O distances in 3 / 4 (2.114(17)/2.079(4) Å) matched well with those reported in analogous complexes. , …”

Section: Resultsmentioning

confidence: 84%

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Unique Metal–Ligand Interplay in Directing Discrete and Polymeric Derivatives of Isomeric Azole-Carboxylate. Varying Electronic Form, C–C Coupling, and Receptor Feature

et al. 2023

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This article dealt with the ruthenium and osmium derivatives of isomeric 1H-indazole-3-carboxylic acid/2H-indazole-3carboxylic acid (H 2 L1) and 1H-benzimidazole-2-carboxylic acid (H 2 L2) along with the π-acidic bpy (bpy = 2,2′-bipyridine) and pap (pap = 2phenylazopyridine) co-ligands. It thus extended structurally authenticated monomeric ([(bpy) 2 Ru II (HL1 − )]ClO 4 [1]ClO 4 , (pap) 2 Ru II (L1 2− ) 2, (bpy) 2 Os II (L1 2− ) 3, (pap) 2 Os II (L1 2− ) 4, (bpy) 2 Ru II (L2 2− ) 5, (bpy) 2 Os II (L2 2− ) 8, and (pap) 2 Os II (L2 2− ) 9) and dimeric ([(bpy, where L2′ 2− was developed selectively with the {Ru(pap) 2 } metal fragment via in situ intermolecular C−C coupling of the two units of decarboxylated benzimidazolate. Moreover, chemical oxidation (Os II to Os III ) of (bpy) 2 Os II (L1 2− ) 3 (E 0 = 0.11 V versus SCE) and (bpy) 2 Os II (L2 2− ) 8 (E 0 = 0.12 V versus SCE) by AgClO 4 yielded unprecedented Os III -Ag I derived polymeric {[(bpy) 2 Os III -L1 2− -Ag I (CH 3 CN)](ClO 4 ) 2 } n {[10](ClO 4 ) 2 } n and dimeric [(bpy) 2 Os III -L2 2− -Ag I (CH 3 CN)](ClO 4 ) 2 [11](ClO 4 ) 2 complexes as a function of trans and cis orientations of the active N2 donor with special reference to the carboxylate O2 of L 2− , respectively. Microscopic (FE-SEM, TEM−EDX, and AFM) and DLS experiments suggested a homogeneously dispersed hollow spherical shaped morphology of {[10](ClO 4 ) 2 } n with an average particle size of 200−400 nm as well as its non-dissociative feature in the aprotic medium. Experimental (structure, spectroscopy, and electrochemistry) and theoretical (DFT/TD-DFT) explorations revealed a redox non-innocent feature of L 2− in the present coordination situations and the selective anion sensing (X = F − , CN − , and OAc − ) event of [1]ClO 4 involving a free NH group at the backface of HL1 − , which proceeded via the NH•••X hydrogen bonding interaction.

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Section: Resultssupporting

confidence: 82%

Section: Resultssupporting

confidence: 65%

Section: Resultsmentioning

confidence: 84%

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Unique Metal–Ligand Interplay in Directing Discrete and Polymeric Derivatives of Isomeric Azole-Carboxylate. Varying Electronic Form, C–C Coupling, and Receptor Feature

et al. 2023

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“…The 1:1 conducting and diamagnetic ( S = 0) [ 1 ]ClO 4 –[ 3 ]ClO 4 exhibited satisfactory elemental analysis and mass spectrometric data (Figure S1 in the Supporting Information and Experimental Section). The NN (azo) vibration of L (≈1480 cm –1 ) shifted to ≈1430 cm –1 on metal coordination in [ 1 ]ClO 4 –[ 3 ]ClO 4 , , and ClO 4 – vibration in each of the metal complexes appeared near 1100 cm –1 in their IR spectra (Figure S2 in the Supporting Information and Experimental Section). The 1 H NMR spectra of the complexes displayed aromatic proton resonances in the standard chemical shift region of δ = 7–11 ppm, and the methyl protons of L2-derived [ 2 ]ClO 4 appeared at δ = 2.4–2.6 ppm (Figure S3 in the Supporting Information and Experimental Section).…”

Section: Resultsmentioning

confidence: 99%

Ruthenium Azobis(benzothiazole): Electronic Structure and Impact of Substituents on the Electrocatalytic Single-Site Water Oxidation Process

Singh

Dey

et al. 2023

Inorg. Chem.

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The present article deals with the structurally and spectroelectrochemically characterized newer class of ruthenium-azoheteroarenes [RuII(Ph-trpy)(Cl)(L)]ClO4, [1]ClO4–[3]ClO4 (Ph-trpy: 4′-phenyl-2,2′:6′,2″-terpyridine; L1: 2,2′-azobis(benzothiazole) ([1]ClO4); L2: 2,2′-azobis(6-methylbenzothiazole) ([2]ClO4); L3: 2,2′-azobis(6-chlorobenzothiazole) ([3]ClO4)). A collective consideration of experimental (i.e., structural and spectroelectrochemical) and theoretical (DFT calculations) results of [1]ClO4–[3]ClO4 established selective stabilization of (i) the unperturbed azo (NN)0 function of L, (ii) the exclusive presence of the isomeric form involving the N(azo) donor of L trans to Cl, and (iii) the presence of extended, hydrogen-bonded trimeric units in the asymmetric unit of [2]ClO4 (CH---O) via the involvement of ClO4 – anions. The detailed electrochemical studies revealed metal-based oxidation of [RuII(Ph-trpy)(Cl)(L)]+ (1 +–3 +) to [RuIII(Ph-trpy)(Cl)(L)]2+ (1 2+–3 2+); however, the electronic form of the first reduced state (1–3) could be better represented by its mixed RuII(Ph-trpy)(Cl)(L•–)/RuIII(Ph-trpy)(Cl)(L2–) state. Both native (1 +–3 +) and reduced (1–3) states exhibited weak lower energy transitions within the range of 1000–1200 nm. Further, [1]ClO4–[3]ClO4 delivered an electrochemical OER (oxygen evolution reaction) process in alkaline medium on immobilizing them to a carbon cloth support, which divulged an amplified water oxidation feature for [2]ClO4 due to the presence of electron-donating methyl groups in the L2 backbone. The faster OER kinetics and high catalytic stability of [2]ClO4 could also be rationalized by its lowest Tafel slope (85 mV dec–1) and choronoamperometric experiment (stable up to 12 h), respectively, along with high Faradic efficiency (∼97%). A comparison of [2]ClO4 with the reported analogous ruthenium complexes furnished its excellent intrinsic water oxidation activity.

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“…The diastereomeric 2a and 2b displayed almost identical electrochemical responses, that is, reversible successive two oxidative (O1: 0.05/0.04 V, O2: 0.75/0.74 V) waves and one reductive (R1: −1.36/–1.37 V) wave in CH 3 CN within the experimental potential window of ±2 V versus SCE. The stability of the electronic form of (acac) 2 Ru III (μ-L4 •– )Ru II (acac) 2 ( S = 0) for the isolated 2a or 2b could be rationalized by the large K c2 (between O1 and R1, Figure ) value of ∼10 23 (Table ), which was also suggestive of a valence-averaged class III mixed-valent state, that is, {Ru 2.5 (μ-L4 •– )Ru 2.5 } instead of a valence-localized class II situation of {Ru III (μ-L4 •– )Ru II } . The considerably high K c1 of 10 11 (O2–O1 in Figure , Table ) implied the inherent stability of the intermediate oxidized species 2a + or 2b + ([(acac) 2 Ru III (μ-L4 •– )Ru III (acac) 2 ] + ), which indeed facilitated its development as well as isolation from the initial reaction mixture along with 2a / 2b (Scheme ).…”

Section: Resultsmentioning

confidence: 99%

Inner-Sphere Electron Transfer Induced Reversible Electron Reservoir Feature of Azoheteroarene Bridged Diruthenium Frameworks

et al. 2022

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This article demonstrates the stabilization of ground-and redoxinduced metal-to-ligand charge transfer excited states on coordination of azocoupled bmpd(L4) [bmpd = (E)-1,2-bis(1-methyl-1H-pyrazol-3-yl)diazene; L4 = −N�N−] to the electron-rich {Ru(acac) 2 } (acac = acetylacetonate) unit in mononuclear Ru II (acac) 2 (L4) (1) and diastereomeric dinuclear (acac) 2 Ru 2.5 (μ-L4 •− )Ru 2.5 (acac) 2 [rac, ΔΔ/ΛΛ (2a)/meso, ΔΛ (2b)] complexes, respectively. It also develops further one-step intramolecular electron transfer induced L4On the contrary, under identical reaction conditions electronically and sterically permuted bimpd [L5, (E)-1,2-bis(4-iodo-1-methyl-1H-pyrazol-3-yl)diazene)] delivered mononuclear Ru II (acac) 2 (L5) (3) as an exclusive product. Further, the generation of unprecedented heterotrinuclear complex [(acac) 2 Ru II (μ-L4)Ag I (μ-L4)Ru II (acac) 2 ]ClO 4 ([4]ClO 4 ) involving unreduced L4 via the reaction of 1 and AgClO 4 revealed the absence of any inner-sphere electron transfer (IET) as in precursor 1, which in turn reaffirmed an IET (at the interface of electron-rich Ru(acac) 2 and acceptor L4) mediated stabilization of 2. Structural authentication of the complexes with special reference to the tunable azo distance (N�N, N−N •− , N−N 2− ) of L and their spectro-electrochemical events in accessible redox states including the reversible electron reservoir feature of 2 → 2 + /2 + → 2 were evaluated in conjunction with density functional theory/time-dependent density functional theory calculations. The varying extent of IET as a function of heteroaromatics appended to the azo group of L (L1 = abpy = 2,2′-azobipyridine, L2 = abbt = 2,2′-azobis(benzothiazole), L3 = abim = azobis(1-methylbenzimidazole), L4 and L5, Schemes 1 & 2) in the Ru(acac) 2 -derived respective molecular setup has been addressed.

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Diosmium compounds containing bis(imidazole)-p-quinone bridging ligands

Cited by 11 publications

References 34 publications

Unique Metal–Ligand Interplay in Directing Discrete and Polymeric Derivatives of Isomeric Azole-Carboxylate. Varying Electronic Form, C–C Coupling, and Receptor Feature

Unique Metal–Ligand Interplay in Directing Discrete and Polymeric Derivatives of Isomeric Azole-Carboxylate. Varying Electronic Form, C–C Coupling, and Receptor Feature

Ruthenium Azobis(benzothiazole): Electronic Structure and Impact of Substituents on the Electrocatalytic Single-Site Water Oxidation Process

Inner-Sphere Electron Transfer Induced Reversible Electron Reservoir Feature of Azoheteroarene Bridged Diruthenium Frameworks

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