How the electronic properties and chemical reactivity of empty fullerenes can be changed upon endohedral metal-doping? How the dynamic behavior and position of encapsulated metal atoms can be controlled? How its functionality can be extended by chemical treatments? We have addressed all aspects of endohedral metallofullerenes, including the synthesis, isolation, structure, chemical properties, and theoretical considerations and their applications in the related fields to answer these questions.
From an organic chemistry perspective, for endohedral metallofullerenes, fascinating nanocarbon molecules, the electronic properties and chemical reactivities of fullerenes can be changed by endohedral metal-doping. Moreover, their functionality can be extended by chemical treatments.
This article gives a comprehensive review of the anharmonic downward distortion following (ADDF) method. The ADDF method has been developed as an automated reaction path search method. This method follows the anharmonic downward distortion (ADD) toward transition states and dissociation channels starting from a local minimum on the potential energy surface (PES). Systematic applications of the ADDF method to all local minima provide a global network of reaction pathways on the PES of given chemical formulas. Various extensions have been proposed and applied to many interesting chemical problems such as elucidation of photodissociation mechanisms, structure prediction of H-bonded clusters, mechanistic studies of organometallic catalysis, design of generation–conversion routes of amino acid molecules, and so on. It has also been employed in efficient construction of anharmonic PESs for highly accurate vibrational analysis. These developments and applications are illustrated with some representative results.
By following the anharmonic downward distortion (ADD), pathways of chemical reactions can be explored automatically and systematically on the quantum chemical potential energy surface. The ADD-following has been successfully employed for systematic analysis and prediction of chemical structures and reactions.
Fullerene assembly films consisting of C60 and 1,2-diaminoethane (ethylenediamine) were easily fabricated on an amino-group-modified substrate by an alternate immersion process. The C60-assembly film was characterized after confirming the film formation using transmission absorption spectroscopy, transmission electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. An inverted-type organic solar cell was fabricated by using the C60-assembly film as the acceptor layer in the photoactive layer of the solar cell. The resultant photoelectric conversion performances of the solar cells were evaluated using the photocurrent and photovoltage via the photoexcitation of polythiophene. The results suggested that the fabricated C60-assembly film works as an n-type semiconductor for polythiophene.
Fullerene assembly films consisting of C60 and 1,2-diaminoethane were fabricated on an amino-group-modified substrate. An organic solar cell was fabricated by using the C60-assembly film. The photovoltaic performances suggested that the C60-assembly film works as an n-type semiconductor for polythiophene.
Acrylonitrile–butadiene rubbers (NBR) have been widely used in many industrial applications due to their very low cost and high performance. In this study, we focus on the fabrication of NBR/carbon nanotube (CNT) composites using surfactant dispersed super-growth SWNTs (SG-SWNTs) as the nanocarbon, and multi-walled carbon nanotubes for comparison. We found that the prepared NBR (15 wt %)/SG-SWNT composite showed a 10 S cm−1 conductance, which was much higher than that of the NBR (15 wt %)/MWNT composite. Such a high value would be due to the good dispersion of the/SG-SWNTs in the rubber matrix.
Practical and diversity-oriented synthesis of multisubstituted benzofurans has been accomplished from simple phenols through a Pummerer annulation/cross-coupling sequence. Operationally simple and rapid reactions of phenols with ketene dithioacetal monoxides (KDMs) with the aid of trifluoroacetic anhydride provide the corresponding 2-methylsulfanylbenzo[b]furans. The scope of the reaction encompasses phenols and KDMs having a broad range of substituents. The remaining methylsulfanyl group in the annulation products is converted to various aryl groups through cross-coupling reactions that we improved specially to this end. This two-step approach to multisubstituted benzofurans is powerful enough to synthesize highly fluorescent benzofuran derivatives as well as the naturally occurring Eupomatenoid family.
The conventional schemes for classifying isomers are clarified to suffer from serious confusion, because they are misleadingly based on the pairing of stereoisomers and “constitutional isomers” and the pairing of enantiomers and “diastereomers.” The misleading features are demonstrated in detail by critically examining isomers of dihalobenzenes, cycloalkanes, 2,3,4-trihydroxyglutaric acids, and pentanols as representative examples. The serious confusion is concluded to stem from disregard for the concepts of equivalence relationships and equivalence classes. The conventional definitions of an isomeric relationship, a stereoisomeric relationship, and an enantiomeric relationship are revised respectively to connote a self-isomeric relationship, a self-stereoisomeric relationship, and a self-enantiomeric relationship. Thereby, these relationships are capable of working up to equivalence relationships, which generate equivalence classes of isomers, stereoisomers, and enantiomers. An isoskeletomeric relationship is proposed as an additional equivalence relationship, which generates an equivalence class of isoskeletomers. A new flowchart of classifying isomers is devised on the basis of these equivalence relationships. On the other hand, the term “constitutionally-isomeric” is replaced by the term constitutionally-anisomeric to emphasize the nature of an inequivalence relationship, i.e., the difference nature at which the relationship aims. The term “constitutionally-isomeric” and the plural form “constitutional isomers” are permitted only for the purpose of characterizing 2D structural formulas. The terms skeletally-anisomeric and diastereomeric are also used as inequivalence relationships. The plural form “diastereomers” is permitted if a reference molecular entity is given to be fixed, but its easy usage should be avoided because they do not mean equivalence classes.
A novel heterogeneous acid catalyst was prepared by the incorporation of Keggin (H3[PW12O40]) and Preyssler (H14[NaP5W30O110]) type heteropolyacids into the interlayer of a layered silicate Hiroshima University Silicate (HUS)-2 that was grafted with (3-aminopropyl)triethoxysilane. Calcination of the Keggin-type heteropolyacid-incorporated HUS-2 at 400 °C for 6 h removed interlayer aminopropyl groups and considerably increased the BET surface area and the micropore volume to 206 m2 g−1 and 0.08 cm3 g−1, respectively. The Preyssler-type heteropolyacid-incorporated HUS-2 had a BET surface area of 216 m2 g−1 and a micropore volume of 0.09 cm3 g−1. The Keggin-type heteropolyacid-incorporated HUS-2 was found to be active for catalysis of the selective dehydration of ethanol to ethene.
Strong luminescent nanoparticles composed of lanthanoid coordination polymers using micelle reaction techniques, lanthanoid coordination nanoparticles, are reported. Size of the nanoparticles estimated using dynamic light-scattering measurements were found to be approximately 66 nm. Lanthanoid coordination nanoparticles were characterized using ESI-MS spectrometry, XRD measurements, and thermogravimetric analyses (TGA). Emission properties of lanthanoid coordination nanoparticles were estimated using emission spectra and emission lifetimes. These results indicate that nanoparticles composed of lanthanoid coordination polymers show effective luminescent properties and thermal stability such as bulk powders of lanthanoid coordination polymers.
The relationships between the geometric and electronic structures, and photoelectron spectra (PES) of LiAln− (n = 3–13) clusters were investigated. The ground and low-lying states geometries were optimized using B3LYP calculation. The assignment for large PES peaks was performed on the basis of calculated adiabatic detachment energies (ADE) and vertical detachment energies (VDE) values. PES peaks in Figure 2 of the clusters smaller than n = 6 are arose mostly from 3p of Al and those larger than n = 9 are 3s–3p (s–p) of Al. This peak pattern change occurs due to the s–p hybridization with the change in the geometric features. It was suggested that the high coordinated Al atom(s) in the Al framework and Li atom play an important role in forming the s–p hybridization at n ≥ 9.
A speciation method for chromate, selenite, and selenate was developed by high-performance liquid chromatography (HPLC)–fluorometric detection (FL) using a single derivatizing reagent. Chromium(VI) was determined based on the fluorescence intensity of 1H-naphtho[2,3-d][1,2,3]triazole (NAT) derived from 2,3-diaminonaphthalene (DAN) and nitrous ion; the NO2− was generated through a redox process between Cr(VI) and hydroxylamine hydrochloride (HACl). 4,5-Benzopiazselenol (Se-DAN) was also derived from Se(IV) and DAN, and it was resolved from NAT and detected by reversed-phase HPLC–FL operated under a single setting of an excitation and a fluorescence wavelength. Linear ranges of the calibration curve and detection limits were 0–20 µmol L−1 (correction coefficient: 0.995) and 0.1 µmol L−1 for Cr(VI), and 0–20 µmol L−1 (0.995) and 0.2 µmol L−1 for Se(IV), respectively. Concentration of Se(VI) was estimated from the difference in its concentration between total Se and Se(IV). The analytical procedure for the determination of total Se included a reduction of Se(VI) to Se(IV) with hydrochloric acid and potassium bromide. The linear range of the calibration curve and detection limit for Se(VI) was 0–20 µmol L−1 (correction coefficient: 0.990) and 0.3 µmol L−1, respectively. The proposed method was applied to the determinations of Cr(VI), Se(IV), and Se(VI) in a river water sample. Recoveries of Cr and Se species ranged between 98 and 104%, and the relative standard deviations were about 5% at 10 µmol L−1 levels of the species.