title: Sensitivity of the valence structure in diruthenium complexes as a function of terminal and bridging ligands.
abstract: The compounds [(acac)2Ru(III)(μ-H2L(2-))Ru(III)(acac)2] (rac, 1, and meso, 1') and [(bpy)2Ru(II)(μ-H2L(•-))Ru(II)(bpy)2](ClO4)3 (meso, [2](ClO4)3) have been structurally, magnetically, spectroelectrochemically, and computationally characterized (acac(-) = acetylacetonate, bpy = 2,2'-bipyridine, and H4L = 1,4-diamino-9,10-anthraquinone). The N,O;N',O'-coordinated μ-H2L(n-) forms two β-ketiminato-type chelate rings, and 1 or 1' are connected via NH···O hydrogen bridges in the crystals. 1 exhibits a complex magnetic behavior, while [2](ClO4)3 is a radical species with mixed ligand/metal-based spin. The combination of redox noninnocent bridge (H2L(0) → → → →H2L(4-)) and {(acac)2Ru(II)} → →{(acac)2Ru(IV)} or {(bpy)2Ru(II)} → {(bpy)2Ru(III)} in 1/1' or 2 generates alternatives regarding the oxidation state formulations for the accessible redox states (1(n) and 2(n)), which have been assessed by UV-vis-NIR, EPR, and DFT/TD-DFT calculations. The experimental and theoretical studies suggest variable mixing of the frontier orbitals of the metals and the bridge, leading to the following most appropriate oxidation state combinations: [(acac)2Ru(III)(μ-H2L(•-))Ru(III)(acac)2](+) (1(+)) → [(acac)2Ru(III)(μ-H2L(2-))Ru(III)(acac)2] (1) → [(acac)2Ru(III)(μ-H2L(•3-))Ru(III)(acac)2](-)/[(acac)2Ru(III)(μ-H2L(2-))Ru(II)(acac)2](-) (1(-)) → [(acac)2Ru(III)(μ-H2L(4-))Ru(III)(acac)2](2-)/[(acac)2Ru(II)(μ-H2L(2-))Ru(II)(acac)2](2-) (1(2-)) and [(bpy)2Ru(III)(μ-H2L(•-))Ru(II)(bpy)2](4+) (2(4+)) → [(bpy)2Ru(II)(μ-H2L(•-))Ru(II)(bpy)2](3+)/[(bpy)2Ru(II)(μ-H2L(2-))Ru(III)(bpy)2](3+) (2(3+)) → [(bpy)2Ru(II)(μ-H2L(2-))Ru(II)(bpy)2](2+) (2(2+)). The favoring of Ru(III) by σ-donating acac(-) and of Ru(II) by the π-accepting bpy coligands shifts the conceivable valence alternatives accordingly. Similarly, the introduction of the NH donor function in H2L(n) as compared to O causes a cathodic shift of redox potentials with corresponding consequences for the valence structure.
authors.affiliation: Department of Chemistry, Indian Institute of Technology Bombay , Powai, Mumbai 400076, India.
authors.forename: Abhishek
authors.initials: A
authors.lastname: Mandal
authors.forename: Hemlata
authors.initials: H
authors.lastname: Agarwala
authors.forename: Ritwika
authors.initials: R
authors.lastname: Ray
authors.forename: Sebastian
authors.initials: S
authors.lastname: Plebst
authors.forename: Shaikh M
authors.initials: SM
authors.lastname: Mobin
authors.forename: José Luis
authors.initials: JL
authors.lastname: Priego
authors.forename: Reyes
authors.initials: R
authors.lastname: Jiménez-Aparicio
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Kaim
authors.forename: Goutam Kumar
authors.initials: GK
authors.lastname: Lahiri
mesh_terms: D015082:2,2'-Dipyridyl / Q000737:chemistry*; D000880:Anthraquinones / Q000737:chemistry*; D018360:Crystallography, X-Ray; D004563:Electrochemistry; D004578:Electron Spin Resonance Spectroscopy; D006885:Hydroxybutyrates / Q000737:chemistry*; D008024:Ligands; D008280:Magnetics; D008958:Models, Molecular; D009942:Organometallic Compounds / Q000737:chemistry*; D010422:Pentanones / Q000737:chemistry*; D012428:Ruthenium / Q000737:chemistry*; D013056:Spectrophotometry, Ultraviolet
chemical_list: D000880:Anthraquinones; D006885:Hydroxybutyrates; D008024:Ligands; D009942:Organometallic Compounds; D010422:Pentanones; C042834:9,10-anthraquinone; C049529:acetyl acetonate; D015082:2,2'-Dipyridyl; D012428:Ruthenium