The University of Tokyo · Chemistry
Professor Shûichi Hiraoka's research lab specializes in supramolecular and coordination chemistry, focusing on the self-assembly of metal-ligand architectures such as cages, capsules, and macrocycles. The lab explores dynamic and reversible systems that form complex 3D structures through precise control of metal ions and multidentate ligands, enabling guest encapsulation and functionalization. Key interests include structural adaptability, metal-ligand exchange processes, and the development of stimuli-responsive host systems with applications in molecular recognition and catalysis.
Figures are computed from collected data and may differ slightly.
ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTGuest-Selected Formation of Pd(II)-Linked Cages from a Prototypical Dynamic LibraryShuichi Hiraoka and Makoto FujitaView Author Information Coordination Chemistry Laboratories Institute for Molecular Science, CREST Japan Science and Technology Cooperation (JST) Myodaiji, Okazaki, 444-8585, Japan Cite this: J. Am. Chem. Soc. 1999, 121, 43, 10239–10240Publication Date (Web):October 15, 1999Publication History Received8 March 1999Published online15
Ten of a kind: A series of {M6L8} octahedral metallocapsules that are structurally identical except for the metal at the apexes was quantitatively prepared from tris-monodentate ligands L and ten divalent d5–d10 transition-metal ions (see picture). Six CF3SO3− anions coordinated inside the capsules can be site-selectively replaced with other anionic ligands to functionalize the cavity. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/
Heteronuclear, supramolecular ring and cage complexes have been constructed from a pyridyl catechol ligand, TiO(acac)2, and PdCl2(CH3CN)2. These two complexes are quantitatively interconvertible, in which Ti4+-centered coordination changes take place between a well-known Ti(catecholato)3 and a newly established TiH(catecholato)2(acetylacetonato) structures. The Ti4+-centered structural changes arise from the changes in the component fraction and basicity condition.
A disk-shaped tridentate ligand 1 arranges silver(I) ions in a two-dimensional triangular and a three-dimensional tetrahedral fashion in the metal-ligand ratios, 3:2 and 1:1, respectively. The resulting sandwich-type (Ag312) and tetrahedral (Ag414) architectures are in a dynamic equilibrium in solution.
An accommodating host: Capsule- and cage-shaped complexes are formed from AgI and disk-shaped trismonodentate ligands in 1:1 and 1.5:1 concentration ratios, respectively; their interconversion is reversible. The capsule complex can entrap a small neutral molecule such as adamantane in the inner space, but the guest is released when the cage structure is adopted. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2005/z462394_s.pdf or fr
The sandwich-shaped heterotopic trinuclear Ag+ complex Ag(3)1.2 was exclusively formed from two different tris(thiazolyl) and hexa(thiazolyl) disk-shaped ligands, 1 and 2, with the aid of three Ag+ ions. The variable-temperature 1H NMR study on its complexation behavior revealed that metal-ligand exchanges between the two neighboring thiazolyl nitrogen donors of 2 take place at the three Ag+ centers in concert. DeltaH++ and DeltaS++ for the exchange process were calculated to be 50.5 kJ mol(-1)
Activity of the Escherichia coli cardiolipin synthase, encoded by cls, increased about 10-fold in the stationary growth phase, while other committed-step enzymes in phospholipid biosynthesis rather decreased. A null cls mutant lost viability to 10(-4) of the wild-type cells during the prolonged incubation for 5 days. Cardiolipin was most stable among membrane phospholipids during the incubation. Accordingly, cardiolipin should play a role in survival of the cell and E. coli employs a sophisticat
The equilibration of cage-like receptors, M3(L1)2 + M3(L2)2 ⇌ 2 M3(L1)(L2), was efficiently controlled by appropriate guest addition: large (spherical) or small (flat) guests stabilized the homoleptic cages (M3(L1)2 or M3(L2)2) while medium-sized guests preferred the heteroleptic cage (M3(L1)(L2)).
A marvelous machine: A 2.5 nm sized molecular machine that behaves like a double ball bearing with three rotors was constructed from two kinds of disk-shaped ligands, AgI ions, and dinuclear PtII bridging complexes (see structure: C red, N blue, O purple, S green, Ag yellow, Pt brown). Motion of the three rotors was found to depend greatly on the degree of interlocking between the two ligands in rotor 2 through helix inversion. Detailed facts of importance to specialist readers are published as
A 4 nm-sized covalent organic capsule having 24 pyridyl groups was synthesized in extremely high yield (43% in three steps) using an octahedron-shaped metallocapsule as a template molecule. The entity was fully characterized by NMR and MALDI-TOF MS measurements. N-Methylation of the 24 pyridyl groups of the organic capsule produced a 5 nm-sized polycationic capsule, which is larger than the neutral precursory capsule because of the electrostatic repulsion between the positive charges on the pyri
A discrete 2-nm-sized self-assembled organic capsule was formed from the union of six hexagram-shaped amphiphile molecules in aqueous methanol due to the hydrophobic effect, van der Waals forces, and CH-pi interactions between the chemical components. A couple of hexa-substituted benzene molecules were encapsulated inside the capsule in both solution and the solid state, as was evidenced by 1H NMR spectroscopy and single-crystal X-ray analysis.
Molecular flippers: The Ag3L2 complexes, which are quantitatively formed from two disk-shaped tridentate ligands (thiazolyl- or pyridyl-based) and three Ag+ ions, are helical and twist between the P and M forms (see scheme). The flip motion includes a relative 120° rotation between the two disk-shaped ligands connected by the Ag+ ions. Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2003/z51068_s.pdf or from the author. Please note:
For a long-range transmission of motion between two movable parts apart from each other, transmitters that can precisely correlate these two motions should be properly incorporated into the system. However, such a motional relay is yet to be realized in artificial systems because of the lack of reliable methodologies for arranging a discrete number of motional parts. Herein, we report a correlated motion of two rotor molecules, which are coaxially arranged at a distance of 1.5 nm, through either
Fitting in: Hexagram-shaped amphiphiles self-assemble in the presence of a spherical, hydrophobic guest molecule to form a tetrahedron-shaped tetrameric organic capsule in an aqueous methanol solution (see picture). In the presence of adamantane, an aqueous solution of a box-shaped hexameric capsule composed of hexagram-shaped amphiphiles was converted into a novel 1.7 nm sized tetrameric capsule that has an encapsulated adamantane template molecule.
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