Bidirectional non-innocence of the β-diketonato ligand 9-oxidophenalenone (L−) in [Ru(aneS3)(L)(dmso)]n, aneS3 = 1,4,7-trithiacyclononane
The new compound [RuII(aneS3)(L)(dmso)]ClO4 (ClO4) (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: [(aneS3)(dmso)RuIII–L˙]3+ (13+) ⇌ [(aneS3)(dmso)RuIII–L−]2+/[(aneS3)(dmso)RuII–L˙]2+ (12+) ⇌ [(aneS3)(dmso)RuII–L−]+ (1+) ⇌ [(aneS3)(dmso)RuII–L˙2−] (1) ⇌ [(aneS3)(dmso)RuII–L3−]−/[(aneS3)(dmso)RuI–L˙2−]− (1−).