Supramolecular Chirality in Self-Assembled Systems

1.1. General Reactivity of Alkyne-Gold(I) Complexes
For centuries, gold had been considered a precious, purely decorative inert metal. It was not until 1986 that Ito and Hayashi described the first application of gold(I) in homogeneous catalysis.1 More than one decade later, the first examples of gold(I) activation of alkynes were reported by Teles2 and Tanaka,3 revealing the potential of gold(I) in organic synthesis. Now, gold(I) complexes are the most effective catalysts for the electrophilic activation of alkynes under homogeneous conditions, and a broad range of versatile synthetic tools have been developed for the construction of carbon–carbon or carbon–heteroatom bonds.

Gold(I) complexes selectively activate π-bonds of alkynes in complex molecular settings,4−10 which has been attributed to relativistic effects.11−13 In general, no other electrophilic late transition metal shows the breadth of synthetic applications of homogeneous gold(I) catalysts, although in occasions less Lewis acidic Pt(II) or Ag(I) complexes can be used as an alternative,9,10,14,15 particularly in the context of the activation of alkenes.16,17 Highly electrophilic Ga(III)18−22 and In(III)23,24 salts can also be used as catalysts, although often higher catalyst loadings are required.

In general, the nucleophilic Markovnikov attack to η2-[AuL]+-activated alkynes 1 forms trans-alkenyl-gold complexes 2 as intermediates (Scheme 1).4,5a,9,10,12,25−29 This activation mode also occurs in gold-catalyzed cycloisomerizations of 1,n-enynes and in hydroarylation reactions, in which the alkene or the arene act as the nucleophile.



Scheme 1

Anti-Nucleophilic Attack to η2-[AuL]+-Activated Alkynes

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Gold(I)-Catalyzed Activation of Alkynes for the Construction of Molecular Complexity

Chirality-Sensing Supramolecular Systems

Bull. Chem. Soc. Jpn. への投稿のすすめ

This article aims to show the identity of “circularly polarized luminescent active simple organic molecules” as a new concept in organic chemistry due to the potential interest of these molecules, as availed by the exponentially growing number of research articles related to them. In particular, it describes and highlights the interest and difficulty in developing chiral simple (small and non-aggregated) organic molecules able to emit left- or right-circularly polarized light efficiently, the efforts realized up to now to reach this challenging objective, and the most significant milestones achieved to date. General guidelines for the preparation of these interesting molecules are also presented.

/pdf/circularly-polarized-luminescence-from-simple-organic-5gfpxas9he.pdf

Circularly Polarized Luminescence from Simple Organic Molecules

A solid-state dedicated circular dichroism (CD) spectrophotometer (J-800KCM) was designed and constructed. As a CD spectrophotometer is a polarization–modulation instrument, CD spectra are necessarily accompanied by artifacts due to macroscopic anisotropies such as linear birefringence (LB) and linear dichroism (LD) which are unique to the solid state. A photomultiplier with the least polarization characteristics and a photoelastic modulator (PEM) with the least residual static birefringence were selected for the new instrument, which was based on the electrical and optical systems of a commercially available spectrophotometer. A phased-locked loop circuit was introduced to a PEM driver, and a sample rotation holder, a stage controller, and an analyzer were installed. We have designed and built a special solid-state sample holder to enable the cancellation of artifact CD, and a lens unit for smaller samples. A set of procedures for obtaining true CD has been devised based on the Mueller matrix method, and...

A solid-state dedicated circular dichroism spectrophotometer: Development and application

Facile Synthetic Route to Highly Luminescent Sila[7]helicene

Aggregationprocessesleadingtochiralitytransferorinduc-tionoramplificationphenomenaarecurrentlyoneofthe“hottopics”ofmodernchemicalscience.Theinvestigationofsuchprocesses has influenced research in many areas includingstudies on the origin of the homochirality of life, variousbiomimeticsystems,materialsandpolymerscience,nonlinearoptics, molecular devices, molecular recognition, and thedetermination of absolute configuration.

Solid-state supramolecular chirogenesis: high optical activity and gradual development of zinc octaethylporphyrin aggregates.

The synthesis and characterization of the bis(bidentate) Schiff-base ligand [(R)-2] formed by the condensation reaction of (R)-1,1‘-binaphthyl-2,2‘-diamine [(R)-BINAM] with pyridine-2-carboxaldehyde is presented. The coordination chemistry of (R)-2 with Ni(ClO4)2·6H2O, Co(ClO4)2·6H2O, CuCl2, and CuSO4 has been investigated. Reaction of (R)-2 with the first two metal salts leads to complexes of the type [M((R)-4)2](ClO4)2 (M = NiII, CoII), where (R)-4 is a tridentate ligand resulting from the hydrolytic cleavage of one of the pyridyl groups from (R)-2. Both complexes were characterized by X-ray crystallography, which showed that the Λ absolute configuration of the metal center is favored in both cases. 1H NMR spectroscopy suggests that the high diastereoselectivity of Λ-[Co((R)-4)2](ClO4)2 is maintained in solution. The reaction of (R)-2 with CuCl2 leads to the dinuclear complex [Cu2((R)-2)Cl4], which has a [Cu2(μ2-Cl2)] core. The reaction of CuSO4 with (R)-2 gives a dimeric complex, {Cu((R)-4)SO4}2, which...

Mono- and dinuclear complexes of chiral tri- and tetradentate Schiff-base ligands derived from 1,1'-binaphthyl-2,2'-diamine.

Phase-modulated ellipsometry of the J-aggregates of the title porphyrin shows that the material gives a true CD signal. This confirms that there is a real chiral transfer by mechanical forces, mediated by shear gradient flows, from the macroscopic to the electronic transition level. Dislocations in the structure of the aggregate could justify the formation of chirality at the level of the electronic transitions once the mesophases can be sculptured by hydrodynamic gradient flows.

/pdf/on-the-mechano-chiral-effect-of-vortical-flows-on-the-140xkmjjx9.pdf

Takunori Harada

Papers

A solid-state dedicated circular dichroism spectrophotometer: Development and application

Facile Synthetic Route to Highly Luminescent Sila[7]helicene

Solid-state supramolecular chirogenesis: high optical activity and gradual development of zinc octaethylporphyrin aggregates.

Mono- and dinuclear complexes of chiral tri- and tetradentate Schiff-base ligands derived from 1,1'-binaphthyl-2,2'-diamine.

On the mechano-chiral effect of vortical flows on the dichroic spectra of 5-phenyl-10,15,20-tris(4-sulfonatophenyl)porphyrin J-aggregates.