Chiral Metal Complexes

A special issue of Inorganics (ISSN 2304-6740). This special issue belongs to the section "Inorganic Solid-State Chemistry".

Deadline for manuscript submissions: closed (28 February 2019) | Viewed by 15136

Special Issue Editor


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Guest Editor
Department of Chemistry, Osaka City Univerisity, Osaka, Japan
Interests: lanthanide coordination chemistry; circular dichroism; supramolecular chirality; molecular sensors; dynamic equilibrium

Special Issue Information

Dear Colleagues,

Metal complexes with chelate ligands can produce optical isomerism around the metal center. In the case of labile metal ions (alkali, alkaline earth, rare earth, and some of the first transition metal ions), the optical isomers are in dynamic equilibrium in solution. Such equilibrium could be controlled by various internal and external factors. The strong circular dichroism that appears in the visible absorption and emission, specific to chiral metal complexes, can be applied to optical sensors that sensitively reflect the changes of metal complex chirality. Aggregates of such labile metal complexes can express supramolecular chirality, which can also be controlled by external factors more sensitively. In this Special Issue, attention is focused on supramolecular recognition chemistry based on the dynamic conformational changes of metal complexes and their applications. 

Prof. Dr. Satoshi Shinoda
Guest Editor

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Keywords

  • labile metal complex
  • circular dichroism
  • lanthanide complex
  • supramolecular assembly
  • dynamic equilibrium
  • molecular sensors

Published Papers (4 papers)

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Research

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26 pages, 6443 KiB  
Article
The Importance of Solvent Effects on the Mechanism of the Pfeiffer Effect
by Jamie L. Lunkley, Ngoc M. Nguyen, Kristina M. Tuminaro, Dana Margittai and Gilles Muller
Inorganics 2018, 6(3), 87; https://doi.org/10.3390/inorganics6030087 - 29 Aug 2018
Cited by 9 | Viewed by 3714
Abstract
The Pfeiffer effect is observed when an optically active compound such as an amino acid is introduced to a solution containing a labile racemic metal complex, and an equilibrium shift is obtained. The “perturbation” results in an excess of one enantiomer over the [...] Read more.
The Pfeiffer effect is observed when an optically active compound such as an amino acid is introduced to a solution containing a labile racemic metal complex, and an equilibrium shift is obtained. The “perturbation” results in an excess of one enantiomer over the other. The shift is a result of a preferential outer sphere interaction between the introduced chiral species and one enantiomeric form (Λ or ∆) of a labile metal complex. Speculations regarding the mechanism of the Pfeiffer effect have attributed observations to a singular factor such as pH, solvent polarity, or numerous other intermolecular interactions. Through the use of the lanthanide(III) complexes [Tb(DPA)3]3− and [Eu(DPA)3]3− (where DPA = 2,6-pyridinedicarboxylate) and the amino acids l-serine and l-proline; it is becoming clear that the mechanism is not so simply described as per the preliminary findings that are discussed in this study. It appears that the true mechanism is far more complicated than the attribute just a singular factor. This work attempts to shine light on the fact that understanding the behavior of the solvent environment may hypothetically be the key to offering a more detailed description of the mechanism. Full article
(This article belongs to the Special Issue Chiral Metal Complexes)
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10 pages, 2427 KiB  
Article
Chiral Tectonics: VCD and ECD Application for Epimerization of a Star-Burst Tetranuclear Complex with a Labile Central Core
by Hisako Sato, Fumi Sato and Akihiko Yamagishi
Inorganics 2018, 6(3), 70; https://doi.org/10.3390/inorganics6030070 - 12 Jul 2018
Cited by 4 | Viewed by 2984
Abstract
The present article reports the application of vibrational circular dichroism (VCD) and temperature-dependent electronic circular dichroism (ECD) methods to reveal the dynamical aspects of a star-burst tetranuclear metal complex with a labile central core in a solution. One-handed chiral inert tecton, ∆- or [...] Read more.
The present article reports the application of vibrational circular dichroism (VCD) and temperature-dependent electronic circular dichroism (ECD) methods to reveal the dynamical aspects of a star-burst tetranuclear metal complex with a labile central core in a solution. One-handed chiral inert tecton, ∆- or Λ-[Ru(III)(acac)2(taetH)] (acacH = acetylacetone, taetH2 = tetraacetylethane), was prepared by reacting [Ru(acac)3] with taetH2 in solid at 120 °C. The ∆Λ-pair of pure enantiomers was obtained chromatographically. On adding Al(ClO4)3 to its enantiopure solution, three units of one-handed tecton were assembled spontaneously around an aluminum(III) ion to form a star-burst tetranuclear complex, [{∆- or Λ-Ru(acac)2(taet)}3Al(III)]. The VCD spectrum recorded on the CDCl3 solution of the complex showed that the central chirality around an Al(III) ion took dominantly the absolute configuration antipodal to those of peripheral Ru(III) units at the temperature lower than −10 °C. The complex underwent interconversion between the ∆- and Λ-configurations around a central Al(III) core (or epimerization) in solution. The activation energy barrier was determined from the time courses of ECD spectra in CHCl3 and CH3OH. Full article
(This article belongs to the Special Issue Chiral Metal Complexes)
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Review

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14 pages, 7201 KiB  
Review
Chirality Induction in Bioorganometallic Conjugates
by Toshiyuki Moriuchi, Satoshi D. Ohmura and Takayo Moriuchi-Kawakami
Inorganics 2018, 6(4), 111; https://doi.org/10.3390/inorganics6040111 - 13 Oct 2018
Cited by 5 | Viewed by 3842
Abstract
Considerable attention has been given to the research field of bioorganometallic chemistry, which is a hybrid chemistry field between biology and organometallic chemistry. The introduction of biomolecules, which have hydrogen bonding sites and chiral centers, into organometallic compounds is a promising strategy to [...] Read more.
Considerable attention has been given to the research field of bioorganometallic chemistry, which is a hybrid chemistry field between biology and organometallic chemistry. The introduction of biomolecules, which have hydrogen bonding sites and chiral centers, into organometallic compounds is a promising strategy to construct chirality-organized bioorganometallic conjugates. This feature paper sketches an outline of induction of helical chirality into bioorganometallic conjugates by the control of a torsional twist of the organometallic moiety. Topics covered included control of the helical chirality of 1,n′-disubstituted ferrocene moieties in ferrocene-dipeptide conjugates, and the chirality induction of the Au(I)–Au(I) axis in the dinuclear organogold(I)-uracil conjugates. Full article
(This article belongs to the Special Issue Chiral Metal Complexes)
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19 pages, 9634 KiB  
Review
Dynamic Helicity Control of Oligo(salamo)-Based Metal Helicates
by Shigehisa Akine
Inorganics 2018, 6(3), 80; https://doi.org/10.3390/inorganics6030080 - 17 Aug 2018
Cited by 11 | Viewed by 4231
Abstract
Much attention has recently focused on helical structures that can change their helicity in response to external stimuli. The requirements for the invertible helical structures are a dynamic feature and well-defined structures. In this context, helical metal complexes with a labile coordination sphere [...] Read more.
Much attention has recently focused on helical structures that can change their helicity in response to external stimuli. The requirements for the invertible helical structures are a dynamic feature and well-defined structures. In this context, helical metal complexes with a labile coordination sphere have a great advantage. There are several types of dynamic helicity controls, including the responsive helicity inversion. In this review article, dynamic helical structures based on oligo(salamo) metal complexes are described as one of the possible designs. The introduction of chiral carboxylate ions into Zn3La tetranuclear structures as an additive is effective to control the P/M ratio of the helix. The dynamic helicity inversion can be achieved by chemical modification, such as protonation/deprotonation or desilylation with fluoride ion. When (S)-2-hydroxypropyl groups are introduced into the oligo(salamo) ligand, the helicity of the resultant complexes is sensitively influenced by the metal ions. The replacement of the metal ions based on the affinity trend resulted in a sequential multistep helicity inversion. Chiral salen derivatives are also effective to bias the helicity; by incorporating the gauche/anti transformation of a 1,2-disubstituted ethylene unit, a fully predictable helicity inversion system was achieved, in which the helicity can be controlled by the molecular lengths of the diammonium guests. Full article
(This article belongs to the Special Issue Chiral Metal Complexes)
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