Binuclear 1,2,4,5-Tetraimino-3,6-diketocyclohexane Bis[bis(Bipyridine)ruthenium(II)] Redox Series

Abstract

The reaction of the [Ru(bpy)2(MeOH)2]2+ cation (bpy = 2,2'-bipyridine) with 1,2,4,5-tetraaminobenzene in the presence of trace water and oxygen yields the cation [(bpy)2Ru(1,2,4,5-tetraimino-3,5-diketocyclohexane)Ru(bpy)2]4+. This binuclear species undergoes ligand-based reductions, giving the 3+ and 2+ charged species. The X-ray structure, electrochemistry, ZINDO calculations, and NMR, ESR, UV/vis, and IR spectra were analyzed where possible, giving an electronic model of the binuclear species and some of its redox products. The X-ray structure reveals the [(bpy)2Ru] fragments symmetrically disposed across the 1,2,4,5-tetraimino-3,5-diketocyclohexane bridge in a molecule with Cs symmetry.

Probing the Transition between the Localised (Class II) and Localised‐to‐Delocalised (Class II–III) Regimes by Using Intervalence Charge‐Transfer Solvatochromism in a Series of Mixed‐Valence Dinuclear Ruthenium Complexes

“…[44][45][46][47][48][49][50] The present report represents one of only a handful of structures that have been obtained through selective diastereoisomer isolation prior to crystal growth. [13,19,[51][52][53] Electrochemical and UV/Vis/NIR spectral characterisation: …”

Metal‐Induced Tautomerization of p‐ to o‐Quinone Compounds: Experimental Evidence from CuI and ReI Complexes of Azophenine and DFT Studies

“…We attribute these absorptions to metal-to-ligand charge transfer (MLCT) transitions from d orbitals of the electronrich metal centers with d 6 (Re I ) or d 10 (Cu I ) configuration to the p* orbital of the o-quinonediimine p system which is largely concentrated at the coordinating a-diimine part. Such longwavelength MLCT transitions have been observed for numerous a-diimine complexes of ] however, the very high intensities with e = 12 500 m À1 cm À1 for the Cu I complex and even 20 100 m À1 cm À1 for the Re I compound of L o is characteristic for complexes of p-and of o-quinonediimines as has been reported before mainly for ruthenium(ii) compounds.…”

“…Using the all-nitrogen compound azophenine L p , a long established p-quinonoid compound [8] with a hardly explored ligand potential in coordination chemistry, [9,10] we have previously shown that coordination of phosphine-stabilized copper(i) can cause tautomerization to the chelating o-quinonoid tautomer L o (Scheme 2), supported by interionic ringforming hydrogen bonding between the newly o-positioned NHPh substituents with one fluorine atom of the BF 4 À counterion. [11] Metal-induced tautomerization is a phenomenon that has been discussed especially in connection with Pt II ±nucleobase interaction where stabilization of the ™wrong∫ tautomer could lead to mispairing in nucleic acids.…”

Straightforward Synthesis of Substituted p‐Quinones: Isolation of a Key Intermediate and Use as a Bridging Ligand in a Diruthenium Complex

“…[4][5][6] The remarkable properties that such ligands impart to their metal complexes make such compounds useful in a variety of fields, such as homogenous catalysis, [7] supramolecular chemistry, [5,8] coordination polymers, [9,10] and as bridging ligands in combination with redox active metal centers such as ruthenium. [11][12][13][14] The last field has gained tremendous attention in recent years because of ambiguities arising in oxidation-state formulations also with "organometallic-type" non-innocent ligands. [15] In addition, the creation of quinone-based molecular magnets is a lively field of research that has produced many interesting results.…”