Strong Binding Affinity of a Zinc-Porphyrin-Based Receptor for Halides through the Cooperative Effects of Quadruple CH Hydrogen Bonds and Axial Ligation
A new type of host compound (1), tetraphenyl zinc-porphyrin (ZnTPP) that contains four triazole groups at the ortho-position of each phenyl group, has been synthesized and characterized by using 1H, 13CNMR, and MALDI-TOF-MS analyses. The host-guest complex formation between 1 and halides was investi...
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Veröffentlicht in: | Chemistry : a European journal 2011-12, Vol.17 (49), p.13898 |
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Sprache: | eng |
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Zusammenfassung: | A new type of host compound (1), tetraphenyl zinc-porphyrin (ZnTPP) that contains four triazole groups at the ortho-position of each phenyl group, has been synthesized and characterized by using 1H, 13CNMR, and MALDI-TOF-MS analyses. The host-guest complex formation between 1 and halides was investigated by using 1HNMR spectroscopy in [D6]DMSO. The triazole, benzyl, and phenylene proton signals were shifted upfield by the addition of halides in the form of tetrabutylammonium salts, which implies that the triazole protons in 1 are allocated very closely to the porphyrin ring and are directed toward the binding pocket over the porphyrin ring during the formation of hydrogen bonds. The UV/Vis absorption spectra showed that both the Soret and Qband absorptions of 1 underwent a strong redshift due to the addition of halides. Compound 1 exhibited surprisingly strong binding affinities for the halides, where the association constants for Cl-, Br-, and I- binding were estimated to be larger than 108, 1.79×107, and 1.84×105M-1, respectively. The UV/Vis absorption changes and the result of competitive titration using 4-tert-butylpyridine indicated that the cooperative effects of axial coordination and CHX hydrogen bond interactions resulted in the strong binding affinity of 1 to halides. |
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ISSN: | 0947-6539 1521-3765 |
DOI: | 10.1002/chem.201101884 |