Rational Design of Emissive NIR-Absorbing Chromophores: RhIII Porphyrin-Aza-BODIPY Conjugates with Orthogonal Metal-Carbon Bonds

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• 作者：Jinfeng Zhou ; Lizhi Gai ; Dr. Zhikuan Zhou ; Wu Yang ; Dr. John Mack ; Kejing Xu ; Prof. Jianzhang Zhao ; Dr. Yue Zhao ; Dr. Hailin Qiu ; Prof. Kin Shing Chan and Prof. Zhen Shen
• 刊名：Chemistry - A European Journal
• 出版年：2016
• 出版时间：September 5, 2016
• 年：2016
• 卷：22
• 期：37
• 页码：13201-13209
• 全文大小：2218K
• ISSN：1521-3765

文摘

The facile synthesis of Group 9 Rh^III porphyrin-aza-BODIPY conjugates that are linked through an orthogonal Rh−C(aryl) bond is reported. The conjugates combine the advantages of the near-IR (NIR) absorption and intense fluorescence of aza-BODIPY dyes with the long-lived triplet states of transition metal rhodium porphyrins. Only one emission peak centered at about 720 nm is observed, irrespective of the excitation wavelength, demonstrating that the conjugates act as unique molecules rather than as dyads. The generation of a locally excited (LE) state with intramolecular charge-transfer (ICT) character has been demonstrated by solvatochromic effects in the photophysical properties, singlet oxygen quantum yields in polar solvents, and by the results of density functional theory (DFT) calculations. In nonpolar solvents, the Rh^III conjugates exhibit strong aza-BODIPY-centered fluorescence at around 720 nm (Φ_F=17–34 %), and negligible singlet oxygen generation. In polar solvents, enhancements of the singlet-oxygen quantum yield (Φ_Δ=19–27 %, λ_ex=690 nm) have been observed. Nanosecond pulsed time-resolved absorption spectroscopy confirms that relatively long-lived triplet excited states are formed. The synthetic methodology outlined herein provides a useful strategy for the assembly of functional materials that are highly desirable for a wide range of applications in material science and biomedical fields.