Photoinduced Electron Transfer Dynamics of Cyclometalated Ruthenium (II)鈥揘aphthalenediimide Dyad at NiO Photocathode

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• 作者：Zhiqiang Ji ; Yiying Wu
• 刊名：Journal of Physical Chemistry C
• 出版年：2013
• 出版时间：September 12, 2013
• 年：2013
• 卷：117
• 期：36
• 页码：18315-18324
• 全文大小：472K
• 年卷期：v.117,no.36(September 12, 2013)
• ISSN：1932-7455

文摘

Both forward and backward electron transfer kinetics at the sensitizer/NiO interface is critical for p-type dye-sensitized photocathodic device. In this article, we report the photoinduced electron transfer kinetics of a Ru(II) chromophore鈥揳cceptor dyad sensitized NiO photocathode. The dyad (O26) is based on a cyclometalated Ru(NCN)(NNN) (Ru[II]) chromophore and a naphthalenediimide (NDI) acceptor, where NCN represents 2,2鈥?(4,6-dimethyl-phenylene)-bispyridine and NNN represents 2,2鈥?6鈥?6鈥?terpyridine ligand. When the dyad is dissolved in a CH₃CN solution, electron transfer to form the Ru(III)鈥揘DI^{鈥?/sup> occurs with a rate constant k_f = 1.1 脳 1010 s鈥? (蟿_f = 91 ps), and electron鈥揾ole pair recombines to regenerate ground state with a rate constant k_b = 4.1 脳 109 s鈥? (蟿_b = 241 ps). When the dyad is adsorbed on a NiO film by covalent attachment through the carboxylic acid group, hole injection takes place first within our instrument response time (180 fs) followed by the subsequent electron shift onto the NDI to produce the interfacial charge-separated state [NiO(h+)鈥揜u(II)鈥揘DI鈥?/sup>] with a rate constant k_f = 9.1 脳 1011 s鈥? (蟿_f = 1.1 ps). The recovery of the ground state occurs with a multiexponential rate constant k_b = 2.3 脳 109 s鈥? (蟿_b = 426 ps). The charge recombination rate constant is slightly slower than a reference cyclometalated ruthenium compound (O25) with no NDI group (蟿_b = 371 ps). The fast formation of interfacial charge separated state is a result of ultrafast hole injection resulting in the reduced form of sensitizer, which provides a larger driving force for NDI reduction. The kinetic study suggests that Ru(II) chromophore鈥揳cceptor dyads are promising sensitizers for the NiO photocathode devices.}