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ABSTRACT: A photoresponsive single-handed double helical supramolecule composed of complementary strands bearing azobenzene moieties underwent a reversible trans-cis-isomerization regulated by photoirradiation, resulting in a change in its molecular length.
Chemical Communications 09/2007; · 6.17 Impact Factor
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Angewandte Chemie International Edition 02/2007; 46(14):2435-9. · 13.45 Impact Factor
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ABSTRACT: We describe novel optically active double helices consisting of complementary strands stabilized by amidinium-carboxylate salt bridges. The m-terphenyl groups of each strand are joined by trans-Pt(II) acetylide complexes with pendant PPh(3) ligands as the surrogate linker, which converts to cis counterparts by a ligand exchange reaction with cis-1,2-bis(diphenylphosphino)ethylene, resulting in the formation of double helices with different structures. Subsequent iodine-promoted reductive elimination on the Pt(II) atoms generates the fully organic, enantiomerically pure double helices. [structure: see text]
Organic Letters 07/2006; 8(12):2583-6. · 5.86 Impact Factor
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ABSTRACT: We describe the construction of the first double-stranded metallosupramolecular helical polymers. We designed and synthesized a supramolecular duplex comprised of complementary m-terphenyl-based strands bearing a chiral amidine or achiral carboxylic acid together with two pyridine groups at the four ends. Supramolecular polymerization of the duplex with cis-PtPh2(DMSO)2 in 1,1,2,2-tetrachloroethane produced the double-stranded metallosupramolecular polymer with a controlled helicity of which the two complementary metallostrands are intertwined through the amidinium-carboxylate salt bridges. The structures and hydrodynamic dimensions of the metallosupramolecular polymers were characterized by 1H NMR, diffusion-ordered NMR, dynamic light scattering, absorption, and CD measurements. The polymeric structure was also visualized by atomic force microscopy.
Journal of the American Chemical Society 06/2006; 128(21):6806-7. · 9.91 Impact Factor
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ABSTRACT: Two novel optically active amidines, (R,R)-N,N‘-bis(1-phenylethyl)-2,4,6-triphenylbenzamidine [(R,R)-2] and (R,R)-N,N‘-bis(1-phenylethyl)benzamidine [(R,R)-3] were synthesized, and their helicity induction abilities for poly[(4-carboxyphenyl)acetylene] (poly-1) in dimethyl sulfoxide (DMSO) were investigated by UV−visible and circular dichroic spectroscopies. Poly-1 exhibited a split-type induced circular dichroism (ICD) in the polymer backbone region in the presence of the optically active amidines due to a predominantly one-handed helical conformation. The ICD pattern of poly-1 complexed with the bulky (R,R)-2 ([(R,R)-2]/[poly-1] = 1) dramatically changed in DMSO and the Cotton effect signs reversibly inverted by changing the temperature, whereas the complex of poly-1 with the less bulky (R,R)-3 complex did not show such a temperature-driven change in the ICD. These results indicate that the helix-sense of poly-1 induced by (R,R)-2 through noncovalent acid−base interactions undergoes a transition from one helix to another in response to temperature. Furthermore, the diastereomeric right- and left-handed helices of poly-1 induced by (R,R)-2 at different temperatures could be separately memorized by the replacement of (R,R)-2 with achiral amines, thus generating enantiomeric helices of the mirror images of each other.
12/2005;
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Angewandte Chemie International Edition 07/2005; 44(25):3867-70. · 13.45 Impact Factor
