One‐Handed Single Helicates of Dinickel(II) Benzenehexapyrrole‐α,ω‐diimine with an Amine Chiral Source

Benzenehexapyrrole‐α,ω‐dialdehyde, composed of a pair of formyltripyrrole units with a 1,3‐phenylene linker, was metallated to give dinuclear single‐stranded helicates. X‐ray studies of the bis‐nickel(II) complex showed a helical C₂ form with a pair of helical–metal coordination planes of a 3N+O donor set. The terminal aldehyde was readily converted into the imine by optically active amines, whereby helix‐sense bias was induced. Bis‐nickel(II) and bis‐palladium(II) complexes of the benzenehexapyrrole‐α,ω‐diimines were studied to show that an enantiomer pair of the helical C₂ form are interchanged by slow flipping of each coordination plane and fast rotation around the C(benzene)?C(pyrrole) bond. The helical screw in the bis‐nickel(II) complexes was biased to one side in more than 95 % diastereoselectivity, which was achieved by using a variety of optically active amines, such as (R)‐1‐cyclohexylethylamine, (S)‐1‐ phenylethylamine, L ‐Phe(OEt) (Phe=phenylalanine), and (R)‐valinol. The nickel complexes showed much better diastereoselectivity than the corresponding palladium complexes.     

Self-promoted electron transfer from cobalt(II) porphyrin to p-fluoranil to produce a dimer radical anion-cobalt(III) porphyrin complex

Self-promoted electron transfer from a cobalt(II) porphyrin [Co(II)OEP] to p-fluoranil (F4Q) occurs, exhibiting a second-order dependence of the electron-transfer rate with respect to the F4Q concentration due to the formation of a strong complex between the dimer radical anion [(F4Q)2*-] and the resulting Co(III)OEP+.     

Lamellar‐Twisting‐Induced Circular Dichroism of Chromophore Moieties in Banded Spherulites with Evolution of Homochirality

Banded spherulites are formed by crystallization of a chiral polymer that is end‐capped with chromophore. Induced circular dichroism (ICD) of the chromophore can be found in the crystallized chiral polymers, giving exclusive optical response of the ICD. The ICD signals are presumed to be driven by the lamellar twisting in the crystalline spherulites, and the exclusive optical activity is attributed to the chirality transfer from molecular level to macroscopic level. To verify the suggested mechanism, the sense of the lamellar twisting in the crystalline spherulite is determined using PLM for the comparison with the ICD signals of the chromophore in the electron circular dichroism spectrum. The conformational chirality of the chiral polymer is determined by the vibrational circular dichroism spectrum. On the basis of the chiroptical results, evolution of homochirality from helical polymer chains (conformational chirality) to lamellar twisting in the banded spherulite (hierachical chirality) is suggested.     

Self-assembly of hybrid dendrons with complex primary structure into functional helical pores

The synthesis of three libraries of self-assembling hybrid dendrons containing a primary structure based on the sequence (4-3,4-3,5)12G2-CO(2)CH(3) generated from benzyl ether, biphenyl-4-methyl ether, and AB(2) repeat units constructed from (AB)(y)--AB(2) combinations of benzyl ethers, is reported. The structural and retrostructural analysis of their supramolecular dendrimers facilitated the discovery of new architectural principles that lead to the assembly of functional helical pores. The self-assembly of an example of hybrid dendron containing -H, -CO(2)CH(3), -CH(2)OH, -COOH, -COOK, -CONH(2), -CONHCH(3), -CO(2)(CH(2))(2)OCH(3), -(R) and -(S)-CONHCH(CH(3))C(2)H(5) as X-groups at the apex demonstrated that these self-assembling dendrons provide the simplest strategy for the design and synthesis of porous columns containing a diversity of hydrophilic and hydrophobic functional groups in the inner part of the pore. The results reported here expand the scope and limitations of dendrons available for the self-assembly of functional pores that previously were generated mostly from dendritic dipeptides, to simpler architectures based on hybrid dendrons.     

Spontaneous resolution through helical assembly of a conformationally chiral molecule with an unusual zwitterionic structure

A conformationally chiral zwitterionic molecule forms mutually orthogonal helical superstructures in the crystal. This is achieved through a network of hydrogen bond pathways, and electrostatic interactions in crystals formed with and without water of crystallization. A systematic protocol for the computation of charge distribution on the 'molecule-in-the-crystal' is presented; the computed charges provide an insight into the origin of the intermolecular electrostatic interactions. The coexisting orthogonal helical formations lead to the homochiral assembly, and spontaneous resolution observed in the crystals. This material facilitates an appraisal of the molecular level interactions, which form the basis for the persistent spontaneous resolution of a conformationally chiral molecule in the solid state.