TY - JOUR
T1 - Mononuclear and Dinuclear Complexes of Dibenzoeilatin
T2 - Synthesis, Structure, and Electrochemical and Photophysical Properties
AU - Bergman, Sheba D.
AU - Goldberg, Israel
AU - Barbieri, Andrea
AU - Barigelletti, Francesco
AU - Kol, Moshe
PY - 2004/4/5
Y1 - 2004/4/5
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=1842536855&partnerID=8YFLogxK
U2 - 10.1021/ic0354062
DO - 10.1021/ic0354062
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AN - SCOPUS:1842536855
SN - 0020-1669
VL - 43
SP - 2355
EP - 2367
JO - Inorganic Chemistry
JF - Inorganic Chemistry
IS - 7
ER -