A Triphenylamine-Grafted Imidazo[4,5-f][1,10]phenanthroline Ruthenium(II) Complex: Acid−Base and Photoelectric Properties

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• 作者：Su-Hua Fan ; An-Guo Zhang ; Chuan-Chuan Ju ; Li-Hua Gao ; Ke-Zhi Wang
• 刊名：Inorganic Chemistry
• 出版年：2010
• 出版时间：April 19, 2010
• 年：2010
• 卷：49
• 期：8
• 页码：3752-3763
• 全文大小：1146K
• 年卷期：v.49,no.8(April 19, 2010)
• ISSN：1520-510X

文摘

A new heteroleptic ruthenium(II) complex of [Ru(Hipdpa)(Hdcbpy)(NCS)₂]⁻·0.5H⁺·0.5[N(C₄H₉)₄]⁺ Ru(Hipdpa) {where Hdcbpy = monodeprotonated 4,4′-dicarboxy-2,2′-bipyridine and Hipdpa = 4-(1H-imidazo[4,5-f][1,10]phenanthrolin-2-yl)-N,N-diphenylaniline} was synthesized and characterized by elementary analysis, standard spectroscopy techniques, and cyclic voltammetry. The ground- and excited-state acid−base properties of Ru(Hipdpa) were studied by means of UV−vis absorption spectrophotometric and spectrofluorimetric titrations in 4:1(v/v) Britton-Robinson/dimethylformamide buffer solution. The four-step separate protonation/deprotonation processes were found in the ground states, and one of which taking place near the physiological pH range. The two observable excited-state protonation/deprotonation processes were found for the Ru(Hipdpa), constituting pH-induced “off−on−off” emission switches. The performance of the complexes as photosensitizers in nanocrystalline TiO₂-based liquid solar cells containing an electrolyte solution (0.05 M I₂, 0.5 M LiI, and 0.5 M 4-tert-butylpyridine in 50% acetonitrile and 50% propylene carbonate) was investigated and found to achieve a much improved device performance (a short-circuit photocurrent density of 18.7 mA cm⁻², an open-circuit voltage of 630 mV, and an overall conversion efficiency of 6.85%) compared to a triphenylamine-free parent complex [Ru(Hpip)(Hdcbpy)(NCS)₂]⁻·[N(C₄H₉)₄]⁺-based device {Hpip = 2-phenyl-1H-imidazo[4,5-f][1,10]phenanthroline} and a comparable performance to that of cis-bis(isothiocyanato)bis(2,2′-bipyridine-4,4′-dicarboxylic acid)ruthenium(II) (N3) under identical experimental conditions. A density functional theory calculation of the molecular structures and electronic properties of the complexes was also carried out in an effort to understand their effectiveness in TiO₂-based solar cells.