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{trans-1,4-Bis[(4-pyridyl)ethenyl]benzene}(2,2‘-bipyridine)ruthenium(II) Complexes and Their Supramolecular Assemblies with β-Cyclodextrin

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journal contribution
posted on 31.05.2004, 00:00 by Sergio H. Toma, Miriam Uemi, Sofia Nikolaou, Daniela M. Tomazela, Marcos N. Eberlin, Henrique E. Toma
Two novel ruthenium polypyridine complexes, [Ru(bpy)2Cl(BPEB)](PF6) and {[Ru(bpy)2Cl]2(BPEB)}(PF6)2 (BPEB = trans-1,4-bis[2-(4-pyridyl)ethenyl]benzene), were synthesized and their characterization carried out by means of elemental analysis, UV−visible spectroscopy, positive ion electrospray (ESI-MS), and tandem mass (ESI-MS/MS) spectrometry, as well as by NMR spectroscopy and cyclic voltammetry. Cyclic and differential pulse voltammetry for the mononuclear complex showed three set of waves around 1.2 V (Ru2+/3+), −1.0 V (BPEB0/-), and −1.15 (BPEB-/2-). This complex exhibited aggregation phenomena in aqueous solution, involving π−π stacking of the planar, hydrophobic BPEB ligands. According to NMR measurements and variable-temperature experiments, the addition of β-cyclodextrin (βCD) to [Ru(bpy)2Cl(BPEB)]+ leads to an inclusion complex, breaking down the aggregated array.