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The effect of the ortho alkylation of perylene bisimides on the alignment and self-assembly properties has been studied. It was found that the dichroic properties of perylene bisimides in a liquid crystal host can be reversed with a single synthetic step by ortho alkylation. Furthermore, a solvent-induced growth of ultralong organic n-type semiconducting fibrils from non- ortho-alkylated perylene bisimide was observed. Ortho substitution of the perylene bisimide core alters the mode of fibrillar growth, leading to isotropic crystallization. [ABSTRACT FROM AUTHOR]

The synthesis of quinoline-derived helically folded aromatic oligoamides functionalized by various chiral functions at their N-terminus is reported. When a (1S)-(-)-camphanyl moiety was introduced, it was found that helix handedness was completely shifted to right-handed helicity (de > 99%), in both protic and nonprotic solvents. The absolute helical sense and the de values were unambiguously characterized by using 1H NMR, circular dichroism (CD), and X-ray crystallography. The crystal structure of these compounds allowed us to propose a rationale for the efficiency of helix handedness induction based on a combination of steric factors and intramolecular hydrogen bonding. [ABSTRACT FROM AUTHOR]

Abstract: This Letter reports the utility of a heavily constrained cis-fused bicyclo[3.3.0]octane (octahydropentalene) aliphatic template for effecting molecular self-assembly. An attractive feature of this system is its heavily constrained alicyclic backbone that would allow for the exploration of self-assembling systems with conformationally ordered features. [Copyright &y& Elsevier]

The article presents a study on the encapsulation of tartaric acid in a helical aromatic oligoamide. It says that the study conducted a titration in CDCI3 with the use of 1% DMSO-d6 so that the guest will be dissolved in the stock solution. The diastereoselectivity was determined through circular dichroism (CD) titration. The changes were monitored through nuclear magnetic resonance which revealed a consistent change with the occurrence of a host-guest complex.

Helically folded molecular capsules based on oligoamide sequences of aromatic amino acids which are capable of binding tartaric acid in organic solvents with high affinity and diastereoselectivity have been synthesized, and their structures and binding properties investigated by ¹H NMR, X-ray crystallography, circular dichroism, and molecular modeling. We found that elongating the helices at their extremities by adding monomers remote from the tartaric binding site results in a strong increase of the overall helix stability, but it does not influence the host-guest complex stability. The effect of this elongation on the binding and release rates of the guest molecules follows an unexpected non-monotonous trend. Three independent observations (direct monitoring of exchange over time, 2D-EXSY NMR, and molecular modeling) concur and show that guest exchange rates tend to first increase upon increasing helix length and then decrease when helix length is increased further. This investigation thus reveals the complex effects of adding monomers in a helically folded sequence on a binding event that occurs at a remote site and sheds light on possible binding and release mechanisms. [ABSTRACT FROM AUTHOR]