Publications (5)32.53 Total impact
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Article: Tunable Mesogens Based on Shape-Persistent Aromatic Oligoamides: From Lamellar, Columnar, to Nematic Liquid Crystalline Phase.
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ABSTRACT: Crescent aromatic oligoamides are shown to form thermotropic lamellar columnar, rectangular columnar, and discotic nematic mesophases according to structural variation, demonstrating their capability to serve as a new class of diverse mesogens of liquid crystals.Organic Letters 06/2012; · 5.86 Impact Factor -
Article: Synthesis of crescent aromatic oligoamides with preorganized chelating groups and their extraction towards transition metal ions.
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ABSTRACT: Three crescent aromatic oligoamides 1-3 with their backbones rigidified by intramolecular hydrogen bonds were designed and synthesized. The liquid-liquid extraction by these compounds has been investigated using UV-vis spectrometry towards Pb(2+) picrate and some transition metal picrates including Ag(+), Hg(2+), Cd(2+), Zn(2+), Cu(2+), Co(2+), Ni(2+) salts. The results revealed higher selectivity and efficiency towards Hg(2+) over other metal cations; pentameric ligand 1 with six oxygen donor atoms provided the highest extractability of 83.3%, while dimeric ligand 3 extracted almost exclusively Hg(2+). The stoichiometry of the extracted complex between ligand 1 and Hg(2+), and the extraction constant (logK(ex)) were determined in solvent extraction.Journal of hazardous materials 03/2012; 217-218:171-6. · 4.14 Impact Factor -
Article: Strong aggregation and directional assembly of aromatic oligoamide macrocycles.
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ABSTRACT: Aromatic oligoamide macrocycles exhibit strong preference for highly directional association. Aggregation happens in both nonpolar and polar solvents but is weakened as solvent polarity increases. The strong, directional assembly is rationalized by the cooperative action of dipole-dipole and π-π stacking interactions, leading to long nanotubular assemblies that are confirmed by SEM, TEM, AFM, and XRD. The persistent nanotubular assemblies contain non-collapsible hydrophilic internal pores that mediate highly efficient ion transport observed with these macrocycles and serve as cylindrical sites for accommodating guests such as metal ions.Journal of the American Chemical Society 11/2011; 133(46):18590-3. · 9.91 Impact Factor -
Article: Efficient kinetic macrocyclization.
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ABSTRACT: In this article, the highly efficient formation of a series of recently discovered aromatic oligoamide macrocycles consisting of six meta-linked residues is first discussed. The macrocycles, with their backbones rigidified by three-center hydrogen bonds, were found to form in high yields that deviate dramatically from the theoretically allowed value obtained from kinetic simulation of a typical kinetically controlled macrocyclization reaction. The folding of the uncyclized six-residue oligomeric precursors, which belong to a class of backbone-rigidified oligoamides that have been demonstrated by us to adopt well-defined crescent conformations, plays a critical role in the observed high efficiency. Out of two possible mechanisms, one is consistent with experimental results obtained from the coupling of crescent oligoamides of different lengths, which suggests a remote steric effect that discourages the formation of oligomers having lengths longer than the backbone of the six-residue precursors. The suggested mechanism is supported by the efficient formation of very large aromatic oligoamide macrocycles consisting of alternating meta- and para-linked residues. These large macrocycles, having H-bond-rigidified backbones and large internal lumens, are formed in high (>80%) yields on the basis of one-step, multicomponent macrocyclization reactions. The condensation of monomeric meta-diamines and a para-diacid chloride leads to the efficient formation of macrocycles with 14, 16, and 18 residues, corresponding to 70-, 80-, and 90-membered rings that contain internal cavities of 2.2, 2.5, and 2.9 nm across. In addition, the condensation between trimeric or pentameric diamines and a monomeric diacid chloride had resulted in the selective formation of single macrocyclic products with 16 or 18 residues. The efficient formation of the macrocycles, along with the absence of other noncyclic oligomeric and polymeric byproducts, is in sharp contrast to the poor yields associated with most kinetically controlled macrocyclization reactions. This system represents a rare example of highly efficient kinetic macrocyclization reactions involving large numbers of reacting units, which provides very large, shape-persistent macrocycles.Journal of the American Chemical Society 02/2009; 131(7):2629-37. · 9.91 Impact Factor -
Article: Improving the Efficiency of Forming ‘Unfavorable’ Products: Eight-Residue Macrocycles from Folded Aromatic Oligoamide Precursors
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ABSTRACT: Oligoamide macrocycles consisting of eight meta-linked benzene residues were synthesized based on the cyclization of aromatic oligoamide precursors having folded backbones rigidified by three-center hydrogen bonds. An alternative route based on the condensation of pentadimeric diamine and trimeric diacid provided the cyclic octamer in 75% yield using EDCI/HOBt as the coupling reagent.Synlett 01/2009; · 2.71 Impact Factor
