Mononuclear and Dinuclear Complexes of Dibenzoeilatin: Synthesis, Structure, and Electrochemical and Photophysical Properties

Sheba D. Bergman, Israel Goldberg, Andrea Barbieri, Francesco Barigelletti*, Moshe Kol

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


This work describes a study of Ru(II) and Os(II) polypyridyl complexes of the symmetrical, fused-aromatic bridging ligand dibenzoeilatin (1). The synthesis, purification, and structural characterization by NMR of the mononuclear complexes [Ru(bpy)2(dbneil)]2+ (2), [Ru(tmbpy)2(dbneil)]2+ (3), and [Os(bpy) 2(dbneil)]2+ (4), the homodinuclear complexes [{Ru(bpy)2}2{μ-dbneil}]4+ (5), [{Ru(tmbpy)2}2{μ-dbneil}]4+ (6), and [{Os(bpy)2}2{μ-dbneil}]4+ (7), and the heterodinuclear complex [{Ru(bpy)2}{μ-dbneil}{Os(bpy) 2}]4+ (8) are described, along with the crystal structures of 4, 6, and 7. Absorption spectra of the mononuclear complexes feature a low-lying MLCT band around 600 nm. The coordination of a second metal fragment results in a dramatic red shift of the MLCT band to beyond 700 nm. Cyclic and square wave voltammograms of the mononuclear complexes exhibit one reversible metal-based oxidation, as well as several ligand-based reduction waves. The first two reductions, attributed to reduction of the dibenzoeilatin ligand, are substantially anodically shifted compared to [M(bpy) 3]2+ (M = Ru, Os), consistent with the low-lying π* orbital of dibenzoeilatin. The dinuclear complexes exhibit two reversible, well-resolved, metal-centered oxidation waves, despite the chemical equivalence of the two metal centers, indicating a significant metal-metal interaction mediated by the conjugated dibenzoeilatin ligand, Luminescence spectra, quantum yield, and lifetime measurements at room temperature in argon-purged acetonitrile have shown that the complexes exhibit 3MLCT emission, which occurs in the IR-region between 950 and 1300 nm. The heterodinuclear complex 8 exhibits luminescence only from the Ru-based fragment, the intensity of which is less than 1% of that observed in the corresponding homodinuclear complex 5; no emission from the Os-based unit is observed, and an intramolecular quenching constant of kq ≥ 3 × 109 S-1 is evaluated. The nature of the quenching process is briefly discussed.

Original languageEnglish
Pages (from-to)2355-2367
Number of pages13
JournalInorganic Chemistry
Issue number7
StatePublished - 5 Apr 2004


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