Bidirectional non-innocence of the β-diketonato ligand 9-oxidophenalenone (L^-) in [Ru([9]aneS3)(L)(dmso)]ⁿ, [9]aneS3 = 1,4,7-trithiacyclononane

The new compound [Ru^II([9]aneS3)(L)(dmso)]ClO₄ ([1]ClO₄) ([9]aneS3 = 1,4,7-trithiacyclononane, HL = 9-hydroxyphenalenone, dmso = dimethylsulfoxide) has been structurally characterised to reveal almost equal C-O bond distances of coordinated L ^-, suggesting a delocalised bonding situation of the β-diketonato ligand. The dmso ligand is coordinated via the sulfur atom in the native (1⁺) and reduced states (1 and 1^-) as has been revealed by X-ray crystallography and by DFT calculations. Cyclic voltammetry of 1⁺ exhibits two close-lying one-electron oxidation waves at 0.77 V and 0.94 V, and two similarly close one-electron reduction processes at -1.43 V and -1.56 V versus SCE in CH₂Cl₂. The electronic structures of 1ⁿ in the accessible redox states have been analysed via experiments (EPR and UV-vis-NIR spectroelectrochemistry) and by DFT/TD-DFT calculations, revealing the potential for bidirectional non-innocent behaviour of coordinated L^/-/2-. Specifically, the studies establish significant involvement of L based frontier orbitals in both the oxidation and reduction processes: [([9]aneS3)(dmso)Ru^III-L]³⁺ (1 ³⁺) [([9]aneS3)(dmso)Ru^III-L^-] ²⁺/[([9]aneS3)(dmso)Ru^II-L]²⁺ (1²⁺) [([9]aneS3)(dmso)Ru^II-L^-]⁺ (1⁺) [([9]aneS3)(dmso)Ru^II-L^2-] (1) [([9]aneS3)(dmso)Ru ^II-L^3-]^-/[([9]aneS3)(dmso)Ru^I-L ^2-]^- (1^-).