Tuning Electronic Structure, Redox, and Photophysical Properties in Asymmetric NIR-Absorbing Organometallic BODIPYs

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• 作者：Yuriy V. Zatsikha ; Eranda Maligaspe ; Anatolii A. Purchel ; Natalia O. Didukh ; Yefeng Wang ; Yuriy P. Kovtun ; David A. Blank ; Victor N. Nemykin
• 刊名：Inorganic Chemistry
• 出版年：2015
• 出版时间：August 17, 2015
• 年：2015
• 卷：54
• 期：16
• 页码：7915-7928
• 全文大小：896K
• ISSN：1520-510X

文摘

Stepwise modification of the methyl groups at the 伪 positions of BODIPY 1 was used for preparation of a series of mono- (2, 4, and 6) and diferrocene (3) substituted donor鈥揳cceptor dyads in which the organometallic substituents are fully conjugated with the BODIPY 蟺 system. All donor鈥揳cceptor complexes have strong absorption in the NIR region and quenched steady-state fluorescence, which can be partially restored upon oxidation of organometallic group(s). X-ray crystallography of complexes 2鈥?b>4 and 6 confirms the nearly coplanar arrangement of the ferrocene groups and the BODIPY 蟺 system. Redox properties of the target systems were studied using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). It was found that the first oxidation process in all dyads is ferrocene centered, while the separation between the first and the second ferrocene-centered oxidation potentials in diferrocenyl-containing dyad 3 is 鈭?50 mV. The density functional theory-polarized continuum model (DFT-PCM) and time-dependent (TD) DFT-PCM methods were used to investigate the electronic structure as well as explain the UV鈥搗is and redox properties of organometallic compounds 2鈥?b>4 and 6. TDDFT calculations allow for assignment of the charge-transfer and 蟺 鈫?蟺* transitions in the target compounds. The excited state dynamics of the parent BODIPY 1 and dyads 2鈥?b>4 and 6 were investigated using time-resolved transient spectroscopy. In all organometallic dyads 2鈥?b>4 and 6 the initially excited state is rapidly quenched by electron transfer from the ferrocene ligand. The lifetime of the charge-separated state was found to be between 136 and 260 ps and demonstrates a systematic dependence on the electronic structure and geometry of BODIPYs 2鈥?b>4 and 6.