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Updated: Aug 28, 2025

Preparation of Contiguous Bisaziridines for Regioselective Ring-Opening Reactions
Published on: July 28, 2022
Inner-Sphere Electron Transfer Induced Reversible Electron Reservoir Feature of Azoheteroarene Bridged Diruthenium
Liton Seikh1, Sanchaita Dey1, Suman Dhara1
1Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India.
Abstract:
This article demonstrates the stabilization of ground- and redox-induced metal-to-ligand charge transfer excited states on coordination of azo-coupled 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 RuII(acac)2(L4) (1) and diastereomeric dinuclear (acac)2Ru2.5(μ-L4•-)Ru2.5(acac)2 [rac, ΔΔ/ΛΛ (2a)/meso, ΔΛ (2b)] complexes, respectively. It also develops further one-step intramolecular electron transfer induced L4•- bridged isovalent higher analogue [(acac)2RuIII(μ-L4•-)RuIII(acac)2]ClO4 in diastereomeric forms, rac-[2a]ClO4/meso-[2b]ClO4. On 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 RuII(acac)2(L5) (3) as an exclusive product. Further, the generation of unprecedented heterotrinuclear complex [(acac)2RuII(μ-L4)AgI(μ-L4)RuII(acac)2]ClO4 ([4]ClO4) involving unreduced L4 via the reaction of 1 and AgClO4 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-N2-) 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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