Studies on the interaction of achiral cationic pseudoisocyanine with chiral metal complexes |
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Authors: | Wang Jian Zeng Lixi Ding Dongdong Li Xiangjun Zhang Hui Zhao Hong Fan Jun Zhang Weiguang He Yujian |
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Institution: | College of Chemistry and Chemical Engineering, Graduate University of Chinese Academy of Sciences, Beijing, China. wangjian06@mails.gucas.ac.cn |
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Abstract: | The effect of chiral metal complexes (Co(en)(3)]I(3)·H(2)O, cis-CoBr(NH(3))(en)(2)]Br(2), KCo(edta)]·2H(2)O and Ru(phen)(3)](PF(6))(2)) on the polymer-bound J-aggregates in aqueous mixtures of pesudoisocyanine (PIC) iodine and poly(acrylic acid, sodium)(PAAS) have been studied by UV-vis absorption, circular dichroism (CD) and fluorescence spectra. At low concentration, the PIC monomers could self-assemble to form supermolecules by binding to each of the COO(-) groups on the polymer chains through electrostatic interactions. After the addition of chiral metal complexes to the formed PIC-PAAS J-aggregates, we found that only the chiral multiple π-conjugated phenanthroline metal complexes could transfer their metal-centered chiral information to the formed J-aggregates. The chiral J-aggregates showed a characteristic induced circular dichroism (ICD) in the visible region of J-band chromophore, and the ICD signals depend on the absolute configuration, concentration of the chiral multiple π-conjugated metal complexes, as well as temperature. More interestingly, the supramolecular chirality of the polymer supported PIC J-aggregates could be memorized even after the addition of an excess opposite chiral complex enantiomers. This is in sharp contrast to the behavior in the high concentrated NaCl induced PIC-J aggregates, in which the optical rotation of a mixture of two enantiomers varies linearly with their ratio. |
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