Rational Design of Emissive NIR-Absorbing Chromophores: Rh-III Porphyrin-Aza-BODIPY Conjugates with Orthogonal Metal-Carbon Bonds
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AbstractThe 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 (FF=17-34 %), and negligible singlet oxygen generation. In polar solvents, enhancements of the singlet-oxygen quantum yield (FD=19-27 %, lambda(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.
All Author(s) ListZhou JF, Gai LZ, Zhou ZK, Yang W, Mack J, Xu KJ, Zhao JZ, Zhao Y, Qiu HL, Chan KS, Shen Z
Journal nameChemistry - A European Journal
Volume Number22
Issue Number37
Pages13201 - 13209
LanguagesEnglish-United Kingdom
Keywordsnear-IR absorption and fluorescence; orthogonal rhodium-carbon bond; porphyrinoids; rhodium; solvatochromism
Web of Science Subject CategoriesChemistry; Chemistry, Multidisciplinary

Last updated on 2021-16-09 at 01:47