Search

A convenient method for the synthesis of pentaarylcyclobutenylrhodium(I) complexes from [Rh(cod)OH]2, arylboronic acids, and diphenylacetylene derivatives is presented. The present rhodium(I) complexes provided insights into the mechanism for the formation of highly reactive living polymerization catalysts from [Rh(nbd)Cl]2by an analogous method, which was previously developed by us. In addition, the complex showed high reactivity as a catalyst for the polymerization of sodium propiolate.

A rational design to create vapoluminescence materials is to install fluorescent tags into molecules. Changing the distance and arrangement of the fluorescent tags can be performed to trigger the vapoluminescence behavior. Herein, we unexpectedly observed a vapoluminescence behavior triggered by a crystal-state host–guest complexation between pillar[6]arene host crystals and organic guest vapors that both exhibit no fluorescence in the visible-light region. After the uptake of the guest vapors, the host–guest complex crystals exhibit blue fluorescence in the visible-light region. Charge-transfer interactions between the host and guest molecules in the crystal state mainly contribute to the observation of fluorescence in the visible-light region.

While host–guest binding is generally a very fast reaction, guest uptake/release sometimes becomes slow particularly when the host cavity is separated from the outside by relatively narrow openings. If the apertures are opened/closed, the host molecule can be used as a nano-sized container just like a capped container in our daily life. This review focuses on the recent development of the kinetic control of guest uptake/release based on the open/close functions, etc., in addition to fundamental kinetic studies of host–guest binding.While host–guest binding is generally a very fast reaction, guest uptake/release sometimes becomes slow particularly when the host cavity is separated from the outside by relatively narrow openings. If the apertures are opened/closed, the host molecule can be used as a nano-sized container just like a capped container in our daily life. This review focuses on the recent development of the kinetic control of guest uptake/release based on the open/close functions, etc., in addition to fundamental kinetic studies of host–guest binding.

Diuranyl bis(salophen) complex 1features a relatively slow conformational motion, induced by an intramolecular O═U═O···UO2binding motif, which interconverts the two nonsymmetric halves of the ligand. This flipping motion, which constitutes one of the fundamental molecular motions, can be completely halted by addition of fluoride anion, which is bound to 1, reaching one of the highest affinities reported to date. This system represents a model to study flipping dynamics in light of the possibility of developing novel types of molecular machines based on it.

Host–guest binding sometimes triggers the subsequent chemical reactions of the host framework as well as changes in the physical properties. Since the host–guest binding generally occurs very quickly, it is sometimes difficult to differentiate the mechanism from the alternative one in which the guest binding occurs after the reaction. However, it is important to differentiate the two mechanisms when we develop new molecules based on time-dependent functions. Thus, we propose two distinct mechanisms, recognition firstand reaction first, in a slowly reacting host system. We designed and synthesized a new cobalt(III) metallohost, [LCo2(pip)4](OTf)2(pip = piperidine), which can take up a guest cation into its 18-crown-6-like cavity causing concomitant exchange of the axial piperidine ligands under solvolytic conditions. We investigated the mechanism to elucidate whether the guest recognition or ligand exchange occurs first. When Na+(5–10 equiv) was present, the guest recognition occurred by the recognition firstmechanism; i.e., Na+was initially taken up into the cavity, then the axial piperidine ligands were replaced with methoxo ligands. On the other hand, when 1 equiv of M+(= K+, Rb+) was present, the guest recognition occurred by the reaction firstmechanism; i.e., M+was taken up after one of the piperidine ligands was replaced with a methoxo ligand. Therefore, the recognition pathway can be switched by changing the guest cations.

A triptycene-based shape-persistent belt-shaped macrocycle, metallonanobelt, was synthesized by the self-assembly of 2,3,6,7-tetraaminotriptycene L and square planar Pd2+. The pentamer was selectively formed by the complexation of L with Pd2+in the presence of the pillar[6]arene derivative P6having triethylene glycol pendant as a template, whereas a mixture of a trimer, tetramer, and pentamer was obtained in the absence of the template. The pentamer was successfully isolated based on the solubility difference between the metallonanobelt and the template. It was also revealed that the isolated pentamer was remarkably stable in solutions such as acetonitrile or methanol thanks to the relatively inert planar chelate metal complex, [Pd(o-phenylenediamine)2] unit. Thus, we can handle the metallonanobelt almost as a static organic nanobelt that is synthesized covalently.

To analyze the structure and function of phytochrome chromophores, we have been synthesizing natural and unnatural bilin chromophores of phytochromes. In this manuscript, we report the synthesis of sterically fixed 15E-fixed18Et-biliverdin (BV) and 15E-anti-fixed18Et-BV derivatives. The key reaction is the introduction of an sp3carbon alkyl chain bearing a leaving group at the meso-position of the CD-ring component by using the corresponding Grignard reagents in the presence of LiCl.

Entangled porous coordination frameworks, wherein two or more distinct frameworks are catenated over an entire crystal, are known to demonstrate unique structural flexibilities in response to the accommodation of molecules in the voids between the frameworks. In this highlight review, we introduce key functions of entangled frameworks based on two principles of their dynamic features: shearing and displacement. We further describe strategies to control the flexibilities; one is a molecular chemistry approach to functionalize frameworks by chemical modification, and the other is a mesoscopic chemistry approach to change the physical form, in particular, the crystal size.

A series of heteroleptic [Ti12X]−complexes have been selectively constructed from a mixture of TiIVions, a pyridyl catechol ligand (H21; H21=4‐(3‐pyridyl)catechol), and various bidentate ligands (HX) in the presence of a weak base, in addition to a previously reported [Ti12(acac)]−(acac=acetylacetonate) complex. Comparative studies of these TiIVcomplexes revealed that [Ti12(trop)]−(trop=tropolonate) is much more stable than the [Ti12(acac)]−complex, which allows the replacement of acac with trop on the [Ti12(acac)]−complex. This TiIV‐centered site‐selective ligand exchange reaction also takes place on a heteronuclear PdIITiIVring complex with the preservation of the PdII‐centered coordination structures. Intra‐ and intermolecular linking between two TiIVcenters with a flexible or a rigid bis‐tropolone bridging ligand provided a tetranuclear and an octanuclear PdIITiIVcomplex, respectively. These higher‐order structures could be efficiently constructed only through a stepwise synthetic route.

Goatfish use a pair of large chin barbels to probe the sea bottom to detect buried prey. The barbels are studded with taste buds but little else is known about the neural organization of this system. We found that the taste buds of the barbel are innervated in a strict orthogonal fashion. The barbel is innervated by a main nerve trunk running in the core of the barbel. A longitudinal nerve bundle originates from the main trunk and, after running a short distance distally, divides into two circumferential nerve bundles (CNB) extending respectively, medially and laterally around the barbel. Approximately 15 CNBs innervate each 1 mm length of barbel. At each transverse level, the CNB innervates two clusters of taste buds, each containing 14 end–organs. The primary taste centre in the brain is similarly extraordinary. The sensory inputs from the barbel terminate in a derived dorsal facial lobe, which has a highly convoluted surface forming a multitude of tubercles. Electrophysiological mapping experiments show that the entire barbel is somatotopically represented in a recurved elongate tubular fashion within the dorsal facial lobe.

A mononuclear peroxocarbonato–iron(III) complex [Fe(6Me-pic)2(O2C(O)O)]−(1-O2C(O)O) with bidentate ligands (6Me-pic), prepared by the reaction of a carbonato–iron(III) complex [Fe(6Me-pic)2(CO3)]−(1-CO3) with H2O2, was fully characterized. 1-O2C(O)O showed reversible O–O bond cleavage and reformation of the peroxo group under CO2at 25 °C. 1-O2C(O)O is capable of not only oxidizing the C=C bond of cyclooctene but also the C–H bond of toluene. As for cyclooctene, epoxidation is favorable under CO2in the presence of H2O, while cis-dihydroxylation precedes under N2, indicating that the oxidation reactivity of 1-O2C(O)O toward cyclooctene can be tuned by changing the concentration of CO2and H2O.

Immunoblotting and pulsed-field gel electrophoresis of Clostridium difficileisolates were employed to differentiate reinfection by a newly acquired strain from relapse by an original strain in a 10-year-old patient with four episodes of C. difficile-associatedcolitis. Immunoblot typing demonstrated subserogroup K-1 of serogroup K for the first and second organisms, subserogroup A-1 of serogroup A for the third organism, and subserogroup G-4 of serogroup G for the fourth organism. PFGE analysis revealed consistent results with immunoblot analysis except that the strains from the fourth episode, whose DNA constantly degraded, were nontypable by this method. Five separate isolates of C. difficilefrom a specimen of each episode showed identical PFGE patterns, indicating that infections of multiple strains probably did not occur in this patient. These typing results suggested that the second episode after a 17-day course of vancomycin therapy represented a relapse by the strain causing the first episode, and that the third and fourth episodes after tapering vancomycin therapy were reinfections by other strains. Both immunoblot and PFGE typing systems are promising tools for analyzing recurrence of C. difficileinfection.

We described for the first time a patient with long-lasting, extremely high serum antibody titcr against Epstein-Barr virus (EBV) viral capsid antigen and early antigen without clinical symptoms suggestive of active EBV infection; the patient finally developed Hodgkin disease (HD) after 7 years of follow-up.

Nanocrystals of three-dimensional pillared-layer type porous coordination polymers, [Zn2(ndc)2(dabco)]n, were fabricated by microwave-assisted coordination modulation, and its morphology was controlled by changing the modulator concentration. Adsorption measurement supported that the crystallinity and intrinsic porosity were maintained even for nanosized crystals, comparable to the corresponding micrometer-sized bulk powder crystals.

Poly(iminoethylene)s containing benzo-15-crown-5 moieties as pendant groups can transport Rb+cation more effectively than the other alkali cations through an organic liquid membrane. The transport selectivities of the polymers diminish drastically with decreasing crown ether content in the polymer chain.