Publications by authors named "Shinji Inagaki"

Article Synopsis
  • Researchers synthesized new phosphine-based mesoporous organosilicas with electron-donating alkyl groups on phosphorus using bifunctional compounds.
  • The synthesized materials were used to immobilize palladium (Pd) species, resulting in effective catalysts for Suzuki-Miyaura cross-coupling reactions between aryl chlorides and phenylboronic acid.
  • The catalyst with tert-butyl groups (3 a) showed greater catalytic activity and compatibility with various functional groups, and its recyclability was tested, demonstrating moderate effectiveness for reuse.
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1,10-Phenanthroline (Phen) is a typical ligand for metal complexation and various metal/Phen complexes have been applied as a catalyst in several organic transformations. This study reports the synthesis of a Phen-based periodic mesoporous organosilica (Phen-PMO) with the Phen moieties being directly incorporated into the organosilica framework. The Phen-PMO precursor, 3,8-bis[(triisopropoxysilyl)methyl]-1,10-phenanthroline (1a), was prepared the Kumada-Tamao-Corriu cross-coupling of 3,8-dibromo-1,10-phenanthroline and [(triisopropoxysilyl)methyl]magnesium chloride.

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SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) caused a pandemic in 2019 and reaffirmed the importance of environmental sanitation. To prevent the spread of viral infections, we propose the application of a mesoporous silica (MS)-based virus-inactivating material. MS is typically synthesized using a micellar surfactant template; hence, the intermediate before removal of the surfactant template is expected to have a virus-inactivating activity.

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The rapid detection of biomolecules greatly contributes to health management, clinical diagnosis, and prevention of diseases. Mass spectrometry (MS) is effective for detecting and analyzing various molecules at high throughput. However, there are problems with the MS analysis of biological samples, including complicated separation operations and essential pretreatments.

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Invited for this month's cover is the group of Shinji Inagaki from Toyota Central R&D Laboratories Inc. and Ken-ichi Fujita from Kyoto University. The image shows iridium complexes immobilized on the channel walls of periodic mesoporous organosilica, which catalyze the dehydrogenation of a methanol-water mixture to produce hydrogen and carbon dioxide.

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CO-free hydrogen production from methanol and water by using transition metal complex catalysts has attracted increasing attention. However, liquid-phase batch reactions using homogeneous catalysts are impractical for large-scale operations, owing to the consumption of bases and the use of organic solvents or additives. This study concerns a novel method for continuous hydrogen production from a simple methanol-water solution under vapor-phase flow.

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Nanoimprinting methods have been used widely to prepare various patterned or nanostructured thin films from inorganic or organic components. However, the accumulation of large functional aromatic groups in covalently crosslinked nanoimprints is challenging, due to the difficulty in controlling the fluidity and reactivity of the precursor films. In this work, nanoimprinting of naphthalimide-silica sol-gel films results in vertically oriented nanoporous structures consisting of covalently crosslinked UV-absorbing frameworks.

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Article Synopsis
  • A periodic mesoporous organosilica (BPy-PMO) has a unique structure with densely packed 2,2'-bipyridine groups, which act as chelating ligands for metal complexes, creating defined catalytic sites.
  • The study involves creating a heterogeneous photocatalyst for water oxidation by attaching various tris(2,2'-bipyridine)ruthenium complexes onto BPy-PMO, using iridium oxide as a catalyst.
  • By modifying the electronic properties of these Ru complexes with different functionalities, the researchers achieved an improved reaction turnover number of 20 for photocatalytic water oxidation, surpassing previous results.
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Low-lying singlet excited states of pyrene derivatives originated from the L and L states of pyrene have decisive influences on their absorption and fluorescence emission behaviors. Calculation of these excited states with quantitative accuracy is required for the theoretical design of pyrene derivatives tailored to target applications; this has been a long-standing challenge for quantum chemical calculations. In this study, we explore an adequate computational scheme through calculations of pyrene and its phenyl-substituted derivatives using multi-reference perturbation theory (MRPT) methods.

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2,2'-Bipyridine is the most widely used chelating ligand for developing metal complexes in coordination and supramolecular chemistry. Here, we present a series of three bipyridine periodic mesoporous organosilicas (BPy-PMOs) grafted with lanthanide β-diketonate complex for the purpose of obtaining thermochromic materials, which can be employed as ratiometric temperature sensors. Such thermometers are based on the ratio of two emission intensity peaks and are not affected by factors such as alignment or optoelectronic drift of the excitation source and detectors.

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A hybrid vapoluminescent system exhibiting fast and repeatable response was constructed using periodic mesoporous organosilica with bipyridine moieties (BPy-PMO) and a Pt(II) complex bearing a potentially luminescent 2-phenylpyridinato (ppy) ligand. An intense red luminescence appeared when the Pt(II)-complex immobilised BPy-PMO was exposed to methanol vapour and disappeared on exposure to pyridine vapour. The ON-OFF vapochromic behaviour occurred repeatedly in a methanol/pyridine/heating cycle.

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The combined use of a metal-complex catalyst and an enzyme is attractive, but typically results in mutual inactivation. A rhodium (Rh) complex immobilized in a bipyridine-based periodic mesoporous organosilica (BPy-PMO) shows high catalytic activity during transfer hydrogenation, even in the presence of bovine serum albumin (BSA), while a homogeneous Rh complex exhibits reduced activity due to direct interaction with BSA. The use of a smaller protein or an amino acid revealed a clear size-sieving effect of the BPy-PMO that protected the Rh catalyst from direct interactions.

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The utility of a bipyridine periodic mesoporous organosilica, BPy-PMO, as a support material of a hydrosilylation catalyst was investigated in the hydrosilylation of phenylacetylene with trimethoxysilane. [PtMe2(BPy-PMO)] (1) exhibited a moderate catalytic activity, whereas the reaction was successfully catalysed by [PtMe2(BPy-PMO-TMS)] (2) bearing end-capped TMS groups on the surface. Spectroscopic analyses of 2 revealed that the porous structure of BPy-PMO-TMS remained almost unchanged through the reaction.

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Periodic mesoporous organosilicas (PMOs), synthesized via surfactant-directed self-assembly of a polysilylated organic precursor (R[Si(OR')]; n≥2, R: organic group), are promising candidates such as catalysts and adsorbents, and for use in optical and electrical devices, owing to their high surface area, well-defined nanoporous structure, and highly functional organosilica framework. Their framework functionality can be widely tuned by selecting appropriate organic groups and controlling their arrangement. This chapter describes the synthesis and structure of PMOs with simple organic groups such as ethane and benzene, and the unique properties and optical applications of functional PMOs.

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Integration of functional molecular parts into nanoporous materials in a state that allows intermolecular charge or energy transfer is one of the key approaches to the development of photofunctional and electroactive materials. Herein, we report charge separation in a functionalized framework of a periodic mesoporous organosilica (PMO) self-assembled by hydrogen bonds. Electroactive π-conjugated organic species with different electron-donating and electron-accepting properties were selectively fixed onto the external surface of a nanoparticulate PMO, within the pore wall, and onto the surface of the internal mesopore.

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This paper describes the physicochemical properties of a rhenium (Re) complex [Re(bpy)(CO) Cl] immobilized on a bipyridine-periodic mesoporous organosilica (BPy-PMO) acting as a solid support. The immobilized Re complex generated a metal-to-ligand charge transfer absorption band at 400 nm. This wavelength is longer than that exhibited by Re(bpy)(CO) Cl in the polar solvent acetonitrile (371 nm) and is almost equal to that in nonpolar toluene (403 nm).

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Heterogeneous metal complex catalysts for the water oxidation reaction have ever been desired for the development of devices simulating photosynthesis. This paper describes the design of highly active and robust heterogeneous iridium complex catalysts for chemical water oxidation. The heterogeneous catalyst (Ir-BPy-NT) was prepared by the post-synthetic metalation of bipyridine-containing mesoporous organosilica nanotubes (BPy-NT) with an [IrCp*Cl(μ-Cl)] (Cp* = η-pentamethylcyclopentadienyl) complex.

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A periodic mesoporous organosilica (PMO) containing 2,2'-bipyridine (bpy) ligands within the framework (BPy-PMO) has great potential for designing novel catalysts by modifying metal complexes. A photosensitizing site (Ru(PS)) was introduced by treating cis-[Ru(bpy) (dimethylsulfoxide)Cl]Cl with BPy-PMO. Then a catalytic site (Ru(Cat)) was brought in Ru(PS) -BPy-PMO by reaction with a ruthenium polymer [Ru(CO) Cl ] .

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Artificial photosynthesis-reduction of CO into chemicals and fuels with water oxidation in the presence of sunlight as the energy source-mimics natural photosynthesis in green plants, and is considered to have a significant part to play in future energy supply and protection of our environment. The high quantum efficiency and easy manipulation of heterogeneous molecular photosystems based on metal complexes enables them to act as promising platforms to achieve efficient conversion of solar energy. This Review describes recent developments in the heterogenization of such photocatalysts.

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Heterogenization of metal-complex catalysts for water oxidation without loss of their catalytic activity is important for the development of devices simulating photosynthesis. In this study, efficient heterogeneous iridium complexes for water oxidation were prepared using bipyridine-bridged periodic mesoporous organosilica (BPy-PMO) as a solid chelating ligand. The BPy-PMO-based iridium catalysts (Ir-BPy-PMO) were prepared by postsynthetic metalation of BPy-PMO and characterized through physicochemical analyses.

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Periodic mesoporous organosilica (PMO) is a unique material that has a crystal-like wall structure with coordination sites for metal complexes. A Ru complex, [RuCl2 (CO)3 ]2 , is successfully immobilized onto 2,2'-bipyridine (BPy) units of PMO to form a single-site catalyst, which has been confirmed by various physicochemical analyses. Using NaClO as an oxidant, the Ru-immobilized PMO oxidizes the tertiary C-H bonds of adamantane to the corresponding alcohols at 57 times faster than the secondary C-H bonds, thereby exhibiting remarkably high regioselectivity.

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Nanoporous materials with functional frameworks have attracted attention because of their potential for various applications. Silica-based mesoporous materials generally consist of amorphous frameworks, whereas a molecular-scale lamellar ordering within the pore wall has been found for periodic mesoporous organosilicas (PMOs) prepared from bridged organosilane precursors. Formation of a "crystal-like" framework has been expected to significantly change the physical and chemical properties of PMOs.

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Heterogeneous catalysis for direct C-H borylation of arenes and heteroarenes in the combination of iridium (Ir) complex fixed on periodic mesoporous organosilica containing bipyridine ligands within the framework (Ir-BPy-PMO) and pinacolborane (HBpin) is reported. Ir-BPy-PMO showed higher catalytic activity toward the borylation of benzene with inexpensive HBpin compared to expensive bis(pinacolato)diboron (B2pin2). The precatalyst could be handled without the use of a glove box.

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A photocatalytic system for CO2 reduction exhibiting visible-light harvesting was developed by preparing a hybrid consisting of a supramolecular metal complex as photocatalyst and periodic mesoporous organosilica (PMO) as light harvester. A Ru(II) Re(I) binuclear complex (RuRe) with methylphosphonic acid anchor groups was adsorbed on acridone or methylacridone embedded in the walls of PMO mesochannels to yield the hybrid structure. The embedded organic groups absorbed visible light, and the excitation energy was funneled to the Ru units.

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An organic-based photocatalysis system for water oxidation, with visible-light harvesting antennae, was constructed using periodic mesoporous organosilica (PMO). PMO containing acridone groups in the framework (Acd-PMO), a visible-light harvesting antenna, was supported with [Ru(II)(bpy)3(2+)] complex (bpy = 2,2'-bipyridyl) coupled with iridium oxide (IrO(x)) particles in the mesochannels as photosensitizer and catalyst, respectively. Acd-PMO absorbed visible light and funneled the light energy into the Ru complex in the mesochannels through excitation energy transfer.

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