Although mesoporous materials have well-defined pore structures, these fine materials can surprisingly be produced by employing a set of conventional and simple procedures such as mixing, heating, filtration, and washing, using low-cost materials. They can be regarded as easy-to-make bulk nanostructured materials. Mesoporous materials have great potential for use in both macroscopic applications and nanotechnology. In this account, we introduce examples of recent developments in mesoporous materials involving innovations in their components and structural designs and concentrating on our own recent progress. These examples include syntheses of mesoporous silica, metal oxides, semiconductive materials, metals, alloys, organic composites, biomaterial composites, carbon, carbon nitride, and boron nitride, as innovative components. As structural innovations for mesoporous materials, various film preparations, pore alignments, and hierarchic structures are described together with their related functions including sensing and controlled release of target molecules.
We introduce recent developments of mesoporous materials, including syntheses of mesoporous silica, metal oxides, semiconductors, metals, alloys, organic composites, biocomposites, carbon, carbon nitride, and boron nitride as well as film fabrication, pore alignment, and hierarchic structuring for novel functions.
In this paper, we review recent advances in the use of polymers in ionic liquids (ILs) from the view point of the “dawn of neoteric solvents and innovative materials.” The first part of this paper presents a brief review of the solubility parameters of ILs, which are expected to serve as a qualitative guide for predicting polymer solubility in ILs; however, this concept cannot be used to rationalize a number of cases in which strong Coulombic interactions dominate the solubility parameters of the ILs. Thus, solubility of 24 different common synthetic polymers is experimentally demonstrated under dilute conditions (3 wt %) in four different common ILs. It is found that the Lewis basicities of the counter anions in the ILs play an important role in determining the solubility of the polymers. ILs can also be used as good solvents for low-solubility biopolymers and as good dispersion media of carbon nanotubes, which contributes to the fields of biorefinery processes and advanced materials. Certain combinations of polymers in ILs undergo phase separations as the temperature of the solutions is varied. The solubility of a nonionic polymer in water generally decreases with increasing temperature, and certain combinations exhibit lower critical solution temperature (LCST) phase separation, whereas the solubility of a polymer in an organic solvent generally increases with increasing temperature and in some cases upper critical solution temperature (UCST) phase separation is observed. Interestingly, both LCST and UCST phase separations are observed for certain polymers in ILs. After presenting possible explanations of the solubility of polymers in ILs, recent developments in the field of thermosensitive polymers in ILs are discussed from the perspective of materials science, where such phase separations are exploited to trigger abrupt changes in polymer properties. The final part of this review describes the thermosensitive self-assembly of block copolymers in ILs. Similar to conventional molecular solvents, block copolymers in ILs exhibit variable self-assemblies in solution and in the bulk.
We review recent advances in the use of polymers in ionic liquids from the view point of the “dawn of neoteric solvents and innovative materials” and demonstrate material function and processing of such binary systems.
Intramolecular interactions of face-to-face tetrathiafulvalenes (TTFs) in 1,8-bis(tetrathiafulvalenyl)naphthalene frameworks were investigated in neutral and cationic states. From X-ray analysis and NMR spectroscopy on neutral 1,8-bis(tetrathiafulvalenyl)naphthalenes, which exist as a mixture of syn- and anti-isomers in solution, there is steric repulsion between TTF moieties. However, analysis of the cyclic voltammogram (CV) revealed that a strong attractive interaction was present in the cation radical state. Electronic spectra of the cation radical state showed the presence of a mixed-valence (MV) state with a strong charge resonance feature. ESR spectra of the 1,8-bis(tetrathiafulvalenyl)naphthalene cation radical showed a typical signal of an MV state. Furthermore, a π-dimer, which exhibits pronounced Davydov splitting in the electronic spectra, was formed in the dication state. The observed absorption bands in the electronic spectra were characterized by using quantum chemical calculations of the cation radical and dication species. NMR spectra of both the π-dimer and tetracation species show either a deshielding effect due to cationic charge or a shielding effect due to diamagnetic ring currents. To our knowledge, this is the first reported example of a 1H NMR spectrum of TTF π-dimer.
Pyridinethiol–ruthenium complexes [Ru(bpy)2(py)(4-pySH)](PF6)2, [Ru(bpy)(tpy)(2-pySH)](PF6)2, and [Ru(bpy)(tpy)(4-pySH)](PF6)2 (4-pySH: 4-pyridinethiol, tpy: 2,2′:6′,6′′-terpyridine, and 2-pySH: 2-pyridinethiol) were synthesized and characterized by 1H NMR, elemental analysis, X-ray photoelectron spectroscopy (XPS), and electrospray ionization-mass spectrometry. Spectral changes after the addition of acid or base by titration demonstrated that the complexes were reversibly protonated/deprotonated. Crystal-structure analysis of [Ru(bpy)(tpy)(2-pySH)](PF6)2 and XPS analysis of the complexes discussed in this study suggest that all pyridinethiol ligands coordinate in a monodentate fashion to Ru only via the sulfur atom. Regardless of the protonated or deprotonated form, the 4-pyridinethiol complexes exhibited one reversible redox couple that is attributed to RuIII/II–(4-pyridinethiol-κS or 4-pyridinethiolate-κS). The protonated form of the 2-pyridinethiol complex showed one reversible redox couple that is attributed to RuIII/II–(2-pyridinethiol-κS), whereas the deprotonated form showed irreversible redox behavior, implying linkage isomerization between RuII–(2-pyridinethiolate-κS) and RuIII–(2-pyridinethiolate-κN) through the redox reaction of RuIII/II. The reversible/irreversible redox behaviors were also confirmed by spectroelectrochemistry. Effects of ancillary ligands on this linkage isomerization are also discussed in this report.
We propose a novel, noncompetitive, label-free, and on-chip immunoassay format based on the excluded volume effect by a target antibody that is itself bound to the corresponding epitope on a biochip. The advantage of the present method is that it only requires a biotin-tethering peptide epitope (capture agent) and fluorophore-labeled-avidin (a signal-generating agent) pair for signal readout. The method is based on the interaction between a nonlabeled target antibody and the corresponding peptide epitope of the antigen decelerating the association rate of the fluorophore-labeled avidin to the biotin moiety at the end of the peptide epitope due to the excluded volume effect of the target antibody. This causes significant changes in signal intensity. Without the target antibody, there is no interference in the binding of the signal-generating agent. The use of other specific interactions would allow fine-tuning of the excluded volume and binding rate to the capture agent to improve sensitivity and versatility.
Water-soluble fluorinated polymer nanoparticles (PNPs) with well-defined structure were successfully prepared as a 19F MRI contrast agent by living radical copolymerization of 2,2,3,3-tetrafluoropropyl methacrylate (TFPMA) and tert-butyl methacrylate (tBMA) initiated from a dendritic macroinitiator. The obtained polymers were hydrolyzed and then converted into a sodium salt, yielding water-soluble fluorinated dendritic-star copolymers (PAMAM-g-PTFPMA-co-PMANa). The copolymer showed a sphere-like structure and the diameter increased in the range of 12–25 nm with the increase of the molecular weight. In 19F NMR properties, the T1 and T2 relaxation times were evaluated to be 400 and 70–80 ms, respectively, and were not significantly affected by the molecular weight of the copolymers. 19F MRI in vitro signals can be visualized at the lowest concentration of 0.5 mM (F atom) and detectable even at concentrations lower than 0.2 µM (particle concentration) under this experimental condition, indicating the high sensitivity due to the accumulated fluorine atoms into nanoparticle. Furthermore, in vivo MRI demonstrated the feasibility of the water-soluble fluorinated PNP as a new type of 19F MRI contrast agent.
The intramolecular hydrogen bond, molecular structure, and vibrational frequencies of 2,4-pentanedione and its seventeen derivatives have been investigated by means of density functional (DFT) method with 6-311++G** basis set. The nature of these interactions, known as resonance-assisted hydrogen bonds, has been discussed. The topological properties of the electron density distributions for O–H···O intramolecular bridges have been analyzed in terms of the Bader theory of atoms in molecules (AIM). The results of calculations show that the Q-parameter describing the degree of π-electron delocalization within the O=C–C=C–O–H keto–enol group correlates with the strength of the H-bond. Correlations between the H-bond strength and topological parameters have been also studied. Natural population analysis data, the electron density and Laplacian properties, as well as, ν(O–H) and γ(O–H) have been used to evaluate the hydrogen-bonding interactions. Furthermore, calculated 1H NMR chemical shifts (δH) correlate well with the hydrogen-bond distance as well as electron density at the bond and ring critical points in the molecular electron density topography.
The chemical properties of chloro(dialkylamino)(diphenylphosphinoyl)methanes have been studied using the simplest compound of this series, chloro(dimethylamino)(diphenylphosphinoyl)methane, as an example. Chloro(dimethylamino)(diphenylphosphinoyl)methane shows ambident reactivity when reacting with electrophiles and nucleophiles depending on coreactant nature, it behaves as either electrophilic substrate or phosphorus nucleophile. This fact can be explained by its dissociation in solutions with both C–Cl bond cleavage to give (dimethylamino)(diphenylphosphinoyl)methyl cation and Cl− anion and C–P bond cleavage to form chloro(dimethylamino)methyl cation and diphenylphosphinite anion. The capability of chloro(dimethylamino)(diphenylphosphinoyl)methane to produce spontaneously Ph2PO–anion allows us to recommend application in organic and organophosphorus synthesis as a synthetic equivalent (synthon) of diphenylphosphinite anion.
Chiral diporphyrin receptor 1, which has a macrocyclic cavity for the intercalation of aromatic guest molecules, was designed and synthesized from pyrrole in five steps. The binding constants (Ka) revealed the greater affinity of 1 for more electron-deficient aromatic guests. The complexation between 1 and 1,3,5-trinitrobenzene (G8) (Ka = 1850 M−1) was much stronger than that between porphyrin monomer 3 and G8 (Ka = 50 M−1). This result strongly suggests that G8 was intercalated into the cavity of 1 via cooperative double π–π stacking. Interestingly, 1 enabled the naked-eye detection of an aromatic explosive G8; a dark-red solution of 1 in CHCl3 turned into a colloidal suspension upon addition of G8, and the light was scattered. Fluorescence spectroscopy was also useful for the selective detection of G8; fluorescence of 1 was quenched by complexation with G8, which was visible with the naked eye. Despite modest binding constants for dinitrobenzene derivatives, 1 showed a good ability to discriminate the enantiomers of twelve chiral compounds bearing a dinitrophenyl group by NMR spectroscopy. The MM calculations with the MM3 force field reproduced inclusion complexes between 1 and nitroaromatic compounds. The mechanism of chiral discrimination is proposed.
Several 2-phosphinoazobenzenes, which are in equilibrium with inner phosphonium salts, were synthesized. Effects of substituents, solvents, and acidic additives on their equilibria are described. Thermodynamic parameters of the equilibria in various solvents suggest that the acceptor character of the solvents is mainly responsible for the solvent effects. Addition of phenols changed the equilibria depending on their acidity. Substituents at the 4- and 4′-positions of the azobenzene also affected the equilibrium constants, which shifted the equilibrium toward the phosphonium salt in the order of their electron-withdrawing ability. Photoisomerization of the 2-phosphinoazobenzenes bearing electron-donating substituents at the 4- and 4′-positions, which shifted the equilibrium toward the 2-phosphinoazobenzene, proceeded successfully. While the phosphonium salt in equilibrium with the (E)-isomer of the 2-phosphinoazobenzene was protonated by perchlorophenol, the (Z)-isomer did not react with a proton source because it could not take on the form of an inner phosphonium salt. Thus, the properties and reactivity of the inner phosphonium salts in equilibrium with the phosphines can be successfully controlled by photoirradiation.
By applying 13C and 1H NMR spectroscopy the pyrolysis of site-selectively 13C-enriched (H313CO12C6H5) and normal anisole compounds was studied in the dark at 0.001–1.0 M (M, mol dm−3) and at 400–600 °C (supercritical conditions). Conversion of the 13C-labeled methyl group was confined to the methoxy-originated fragments, 13CO and 13CH4, and the reactive intermediate, H13CHO*. The normal phenyl group, 12C6H5– was converted to benzene, 12C6H6 and phenol, 12C6H5OH without ring disintegration. The pyrolysis consists of two elementary steps: (1) the rate-determining unimolecular ether-bond fission (k1) to generate the fragmented product C6H6 and energized intermediate H13CHO* through the intramolecular proton transfer from the methoxy group to the phenyl, and (2) the fast bimolecular disproportionation (k2) through the intermolecular proton/hydride transfer from H13CHO* to H313COC6H5 to produce 13CO, 13CH4, and C6H5OH. CO is generation by the heterolytic (ionic) mechanism in contrast to the homolytic (radical) one via the phenoxy radical intermediate (C6H5O•) in the literature despite the agreement of the rate constant (k1) and the activation energy.
A concise total synthesis of non-steroidal estrogen receptor antagonists R1128 A–D (1a–1d) has been achieved using iterative ortho-lithiation of 2-(4-methoxyphenyl)-4,4-dimethyloxazoline (3) as the key reaction.
Ladder-type heteroacenes based on indolodibenzothiophene have been synthesized. The route involved a regioselective twofold intramolecular acid-induced cyclization of the central bis(butylsulfinyl)phenyl unit onto the adjacent carbazole units, followed by dealkylation to give diindolobenzobisbenzothiophene (DIBBBT) derivatives. Importantly, this sequence proceeded efficiently in the presence of the chloro substituents which provided reactive sites for further π-extension of the DIBBBT core. The chloro derivative underwent twofold palladium-catalyzed Suzuki–Miyaura reactions with phenylboronic acid or 4-n-octylphenylboronic acid. Compounds have been characterized by 1H NMR spectroscopy, mass spectrometry, elemental analysis, optical spectroscopy, and solution electrochemical studies. Organic field-effect transistors (OFETs) have been constructed based on drop-cast thin films and the performances as p-type semiconductor are presented. The chloro derivative was also copolymerized with 9,9-dioctyl-2,7-fluorenylenediboronic acid bis(1,3-propanediol) ester to give the alternating copolymer which exhibits blue photoluminescence in solution and blue-green electroluminescence in a solution processed organic light-emitting diode (OLED).
By applying a pulsed arc-plasma process, Pt nanoparticles were deposited from a Pt cathode onto CeO2 powders to study their structure and catalytic activity for CO oxidation. Highly dispersed uniform metallic Pt crystallites with the size of 2.6 ± 0.7 nm were obtained. Because of the highly dispersed metallic Pt nanoparticles suitable for CO chemisorption, the catalyst prepared by arc-plasma exhibited higher CO oxidation activity than those prepared by conventional wet impregnation. However, the catalyst was deactivated to a larger extent compared to the impregnated catalyst after thermal aging at 900 °C in a stream of 10% H2O in air.