This account reviews recent development of in situ crystallographic study of reactive intermediates using the cryo-trapping method. Starting from the basic concept of a reaction cavity in a crystal, we succeeded in not only observing photoinduced reactive species such as radical, carbene, and nitrene but also establishing a unique approach, crystalline molecular flask, to observe labile species in chemical reactions in a crystal. On the basis of such a crystalline reaction field design, we successfully observed irreversible reactive intermediates in a crystal.
This account reviews recent development of in situ crystallographic study of reactive intermediates on the basis of crystal design.
We report the UV-light-induced formation of water aerosol/droplets in air based on laser-light scattering measurements, differential mobility analyses and cavity ring-down laser spectroscopy (CRDS), and propose a mechanism. It was shown that UV-light (185 nm) irradiation of air within a soap bubble rapidly produced water droplets under supersaturated conditions. Multiple UV irradiation cycles were demonstrated to increase particle sizes in a controlled reaction chamber. We propose that the reaction mechanism is initiated by oxygen (O2) photodissociation and ozone (O3) formation and further photodissociation of O3 leads to sequential dark reactions, generating hydrogen peroxide (H2O2) as a hygroscopic stable product. Exciting excess O3 in wet air with mid-UV radiations (254 nm) was also demonstrated to produce water particles, indicating that this series of reactions can be started at an intermediate stage using a longer wavelength of UV light. For the first time, it was demonstrated that H2O2 in air is a precursor of the initial nucleation of water with two different aerosol formation schemes at 263 K: a) from a mixture of H2O2 and water vapor in dark and b) from a mixture of O3 and water vapor by mid-UV (266 nm) light irradiation. These results indicate that H2O2 can capture water molecules and form water particles.
UV-light-induced water aerosol/droplet formation in wet air was described under different environmental conditions and irradiation modes. For the first time, it was experimentally shown that hydrogen peroxide is a precursor of the nucleation of water in dark and under UV irradiation.
The dynamic properties of water confined in Sephadex G15 gel were investigated over the temperature range of 275–320 K at a hydration level h (= mass of water/mass of dry G15 gel) of 0.38, where both bound water melting at 258–268 K and unfrozen water are present, by using quasi-elastic neutron scattering (QENS) and neutron spin echo (NSE) techniques. The QENS data showed that, at 290 K, the water molecules perform local motions characterized by a diffusion coefficient Dlocal of (0.65 ± 0.05) × 10−5 cm2 s−1 and that the diffusion is limited to some volume estimated as a sphere with a radius of 4.4 Å. The Arrhenius plots of the relaxation time of water gave the activation energy of 44.2 ± 1.5 kJ mol−1, which is somewhat larger than the value (15–36 kJ mol−1) of water confined in MCM-41 C10 (pore diameter 21 Å). This finding suggests that water molecules in G15 gel are strongly bound to the hydroxy groups of the crosslinked substrates.
Kurahamide, a new dolastatin 13 analog, was isolated from a marine cyanobacterial assemblage, consisting mostly of Lyngbya sp. Its gross structure was elucidated by spectroscopic analysis, and the stereochemistries were assigned based on a chiral HPLC analysis of hydrolysis products. Kurahamide strongly inhibited elastase and chymotrypsin in vitro. In addition, kurahamide moderately inhibited the growth of human cancer cells, including HeLa and HL60 cells.
By the use of auxiliary functions with the noninteger indices introduced by one of the authors, the formulas for the S(α*)-self-frictional overlap integrals (S(α*)-SFOIs) of χ-Slater type orbitals with noninteger principal quantum number (χ-NISTOs) are presented, where α* is the self-frictional quantum number. The suggested approach guarantees a highly accurate calculation of the S(α*)-SFOIs for the arbitrary values of parameters and locations of orbitals.
By means of surface desorption atmospheric pressure chemical ionization mass spectrometry (DAPCI-MS), mass-spectra fingerprints of various oil samples were rapidly recorded in the mass range of m/z 50–1000 without any sample pretreatment in negative ion mode. A new spectrogram analysis method (Chaos Entropy Index) for identifying complex mixtures was established and applied to the authentication of expired oil. Multivariate statistics analysis showed that expired edible oils can be successfully separated from fresh edible oils with 100% accuracy on the basis of Global CEIs and the most significant mass ranges presenting major feature peaks of expired oil were determined based on Local CEIs. These experimental findings demonstrate that as a rapid, simple, and accurate analytical method, CEI approach in conjunction with DAPCI-MS has an extensive prospect for differential analysis of complex viscous mixtures.
The adhesion force of electroless nickel–phosphorus (Ni–P) platings prepared on silicon nitride (SiN), aluminum (Al), and polyimide (PI) substrates using complexing agents of glycine, succinic acid, succinic acid with glycine, and succinic acid with malic acid was demonstrated for the application to wafer-level packaging in large-scale integrated circuits. The adhesion strength of Ni–P platings was investigated by the tape-peeling test and the universal mechanical strength tester. As results, no peeling of Ni–P films formed using glycine, succinic acid, and succinic acid with glycine were observed, although Ni–P films formed using succinic acid with malic acid showed peeling. Thus, Ni–P plating formed using succinic acid with malic acid gave the smallest adhesion force. In contrast, the adhesion force of Ni–P platings formed using succinic acid with glycine on SiN, Al, and PI was the largest, approximately 850 kg cm−2, among Ni–P platings formed using those complexing agents. The growth rate of Ni–P films formed using succinic acid, succinic acid with glycine, and succinic acid with malic acid was uneven on SiN, Al, and PI. In comparison, Ni–P plating formed using glycine provided uniform growth rate on SiN, Al, and PI.
Two series of new modified poly(ether–imide–urea)s, POa–POc and PSa–PSc, with benzoxazole or benzothiazole pendent groups were successfully synthesized by diphenyl azidophosphate (DPAP)-activated one-pot polyaddition reaction of two bis(imide–dicarboxylic acid)s, 2-[3,5-bis(4-trimellitimidophenoxy)phenyl]benzoxazole (1O) or 2-[3,5-bis(4-trimellitimidophenoxy)phenyl]benzothiazole (1S) with various kinds of aromatic diamines a–c. In this direct method, the polymers were prepared by polyaddition reactions of the in situ-formed diisocyanate with the aromatic diamines. For comparative purposes, reference poly(ether–imide–urea)s, PRa–PRc, were also prepared by reacting a bis(imide–dicarboxylic acid) lacking pendent groups, namely, 3,5-bis(4-trimellitimidophenoxy)benzene (2) with the same diamines under similar conditions. Characterization of polymers was accomplished by inherent viscosity measurements, FTIR, 1H NMR spectroscopy and thermogravimetry. The polymers were obtained in quantitative yields with inherent viscosities between 0.19 and 0.37 dL g−1. The solubilities of modified poly(ether–imide–urea)s in common organic solvents as well as their thermal stability were enhanced compared to these of the corresponding unmodified poly(ether–imide–urea)s. The glass-transition temperature, 10% weight loss temperature, and char yields at 800 °C were, respectively, 7–28, 14–38 °C, and 3–7% higher than those of the reference polymers in nitrogen atmosphere.
Proton conductivity of graphene oxide (GO) has been reduced in graphene oxide–metal ion hybrids (GO–M; M = K+, Al3+, Zn2+, Fe3+, Cr3+, Co2+, Pr3+, Ce3+, and Tb3+). As the hybrids contain doped metal ions, we propose their possibility as catalyst and electrodes in sensing devices.