Synthesis, Structural Characterization, and Photophysical, Spectroelectrochemical, and Anion-Sensing Studies of Heteroleptic Ruthenium(II) Complexes Derived from 4鈥?Polyaromatic-Substituted Terpyridin

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• 作者：Dinesh Maity ; Shyamal Das ; Sourav Mardanya ; Sujoy Baitalik
• 刊名：Inorganic Chemistry
• 出版年：2013
• 出版时间：June 17, 2013
• 年：2013
• 卷：52
• 期：12
• 页码：6820-6838
• 全文大小：978K
• 年卷期：v.52,no.12(June 17, 2013)
• ISSN：1520-510X

文摘

Heteroleptic bis-tridentate ruthenium(II) complexes of composition [(H₂pbbzim)Ru(tpy-Ar)](ClO₄)₂, where H₂pbbzim = 2,6-bis(benzimidazol-2-yl)pyridine and tpy-Ar = 4鈥?substituted terpyridine ligands with Ar = phenyl (2), 2-naphthyl (3), 9-anthryl (4), and 1-pyrenyl (5) groups, have been synthesized and characterized by using standard analytical and spectroscopic techniques. The X-ray crystal structures of the complexes [(H₂pbbzim)Ru(tpy-Naph)](ClO₄)₂ (3), [(pbbzim)Ru(tpy-Naph)]路(CH₃)₂CO路H₂O (3a), and [(H₂pbbzim)Ru(tpy-Py)](ClO₄)₂ (5) have been determined. The absorption, steady-state, and time-resolved luminescence spectral properties of the complexes were thoroughly investigated in dichloromethane. The compounds display strong luminescence at room temperature with lifetimes (蟿₂) in the range of 5.5鈥?2 ns, depending upon the nature of the polycyclic aromatic moiety as well as the solvents. The complexes are found to undergo one reversible oxidation in the positive potential window (0 to +1.5 V) and four successive quasi-reversible reductions in the negative potential window (0 to 鈭?.4 V). The anion-sensing properties of the receptors were thoroughly investigated in acetonitrile/dichloromethane (1/9 v/v) solutions (2 脳 10^鈥? M) using absorption, steady-state, and time-resolved emission spectroscopic studies. ¹H NMR titration experiments, on the other hand, were carried out in either CD₃CN or DMSO-d₆. The anion-sensing studies revealed that the receptors act as sensors for F^{鈥?/sup>, CN鈥?/sup>, AcO鈥?/sup>, and SO₄2- and to some extent for HSO₄鈥?/sup> and H₂PO₄鈥?/sup>. It is evident that, in the presence of excess anions, deprotonation of the imidazole N鈥揌 fragments of the receptors occurs, which is signaled by the change of color from yellow-orange to violet visible with the naked eye. From the absorption and emission titration studies the binding/equilibrium constants of the receptors with the anions have also been determined. Anion-induced lifetime quenching and/or enhancement make the receptors suitable lifetime-based sensors for selective anions. Cyclic voltammetric (CV) measurements of the compounds carried out in acetonitrile have provided evidence in favor of anion-dependent electrochemical responses with F鈥?/sup> and AcO鈥?/sup> ions. Spectroelectrochemical studies have also been carried out for both the protonated and deprotonated forms of the complexes in the range of 300鈥?200 nm. With successive oxidation of the Ru(II) center, replacement of MLCT bands by LMCT bands occurs gradually with observation of sharp isosbestic points in all cases.}