Syntheses, Electrochemistry, and Photodynamics of Ferrocene鈥揂zadipyrromethane Donor鈥揂cceptor Dyads and Triads
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- 作者：Anu N. Amin ; Mohamed E. El-Khouly ; Navaneetha K. Subbaiyan ; Melvin E. Zandler ; Mustafa Supur ; Shunichi Fukuzumi ; Francis D鈥橲ouza
- 刊名：Journal of Physical Chemistry A
- 出版年：2011
- 出版时间：September 8, 2011
- 年：2011
- 卷：115
- 期：35
- 页码：9810-9819
- 全文大小：1166K
- 年卷期：v.115,no.35(September 8, 2011)
- ISSN：1520-5215
文摘
A near-IR-emitting sensitizer, boron-chelated tetraarylazadipyrromethane, has been utilized as an electron acceptor to synthesize a series of dyads and triads linked with a well-known electron donor, ferrocene. The structural integrity of the newly synthesized dyads and triads was established by spectroscopic, electrochemical, and computational methods. The DFT calculations revealed a 鈥榤olecular clip鈥?type structure for the triads wherein the donor and acceptor entities were separated by about 14 脜. Differential pulse voltammetry combined with spectroelectrochemical studies have revealed the redox states and estimated the energies of the charge-separated states. Free-energy calculations revealed the charge separation from the covalently linked ferrocene to the singlet excited ADP to yield Fc+鈥揂DP鈥⑩€?/sup> to be energetically favorable. Consequently, the steady-state emission studies revealed quantitative quenching of the ADP fluorescence in all of the investigated dyads and triads. Femtosecond laser flash photolysis studies provided concrete evidence for the occurrence of photoinduced electron transfer in these donor鈥揳cceptor systems by providing spectral proof for formation of ADP radical anion (ADP鈥⑩€?/sup>) which exhibits a diagnostic absorption band in the near-IR region. The kinetics of charge separation and charge recombination measured by monitoring the rise and decay of the ADP鈥⑩€?/sup> band revealed ultrafast charge separation in these molecular systems. The charge-separation performance of the triads with two ferrocenes and a fluorophenyl-modified ADP macrocycle was found to be superior. Nanosecond transient absorption studies revealed the charge-recombination process to populate the triplet ADP as well as the ground state.