Epindolidione (H 2 L), ah eteroatom-modifieda nalogue of tetracene and as tructural isomer of indigo, forms dinuclear complexesw ith [RuX 2 ] 2 + ,X = bpy (2,2'-bipyridine, [1] 2 +)o rpap (2-phenylazopyridine, [2] 2 +), in its doubly deprotonatedb ridging form m-L 2À .The dications in compounds meso-[1](ClO 4) 2 and meso-[2](ClO 4) 2 ,[ X 2 Ru(m-L)RuX 2 ](ClO 4) 2 , contain five-membered chelate rings N-CÀC-O-Ru II with p bridged metalsa ta ni ntramolecular distance of 7.19 .S tepwise reversible oxidation and reduction is mainly ligand centered (oxidation:L 2À ;r eduction:X), as deduced from EPR of one-electron oxidized and reduced intermediates and from UV/Vis/NIR spectroelectrochemistry,s upported by TD-DFT calculation results.T he results for [1](ClO 4) 2 and [2](ClO 4) 2 are qualitatively similart ot he ones observed with the deprotonated indigo-bridged isomers with their six-membered chelate ring structures, confirming the suitability of both p systems for molecular electronicsa pplications, low-energy absorptions, and multiple electron transfers. Scheme1.Structuralisomers of indigo and epindolidione. Scheme2.The two diruthenium complexes [1](ClO 4) 2 and [2](ClO 4) 2 with doublydeprotonated epindolidione presented in this work.
The unexplored substrate-based
reactivity profile of newly designed bis(heterocyclo)methanide (BHM,
L1–L3), a structural mimic of ubiquitous β-diketiminate,
was demonstrated on an electronically rich {Ru(acac)2}
platform (acac = σ-donating acetylacetonate). In this regard,
this work deals with structurally characterized [Ru(L)(acac)2] complexes 1A–3A incorporating electronically
varying heterocycles {1A, L1 = bis(imidazo[1,5-a]pyridin-3-yl)methanide; 2A, L2 = (Z)-4-[(6,7-dihydrothieno[3,2-c]pyridin-4-yl)methylene]-6,7-dihydro-4H-thieno[3,2-c]pyridin-5-ide; 3A, L3 = (Z)-6-chloro-1-[(6-chloro-3,4-dihydroisoquinolin-1-yl)methylene]-3,4-dihydro-1H-isoquinolin-2-ide}. The significant impact of electronic
modification at the BHM backbone (L1–L3) on its redox tunability
at the metal–ligand interface in 1A–3A and
its subsequent oxygenation profile to yield bis(heterocyclo)methanone
(BMO, analogue of α-ketodiimine) in the corresponding [Ru(BMO)(acac)2] (1B–3B) via a radical pathway were rationalized.
In addition, oxidative dehydrogenation of metalated BMO in 1B–3B to BAM [bis(heteroaryl)methanone] in [Ru(BAM))(acac)2] (1C–3C) was illustrated in support of the nonspectator
behavior of α-ketodiimine. A combined experimental and theoretical
investigation extended mechanistic outlines of the aforementioned
transformation processes, which in effect provided a new dimension
relating to the analogous β-diketiminate as well as α-ketodiimine
chemistry.
The article dealt with the sensitive electronic forms in accessible redox states of structurally and spectroscopically authenticated deprotonated 1,2-bis((1H-pyrrol-2-yl)methylene) hydrazine (H2LR, R=H) or 1,2-bis((3,5-dimethyl-1H-pyrrol-2-yl)methylene)hydrazine (H2LR, R=Me), a BODIPY analogue bridged...
Varying chelation assisted as well as solvent dependent reactivity profiles of isostructural β-ketoiminate analogues explicate their non-spectator behaviour and fractional redox non-innocence.
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