Dual Nickel(II)/Mechanoredox Catalysis: Mechanical-Force-Driven Aryl-Amination Reactions Using Ball Milling and Piezoelectric Materials

The combination of a nickel(II) catalyst and a mechanoredox catalyst under ball-milling conditions promotes mechanical-force-driven C−N cross-coupling reactions. In this nickel(II)/mechanoredox cocatalyst system, the modulation of the oxidation state of the nickel center, induced by piezoelectricity, is used to facilitate a highly efficient aryl-amination reaction, which is characterized by a broad substrate scope, an inexpensive combination of catalysts (NiBr₂ and BaTiO₃), short reaction times, and an almost negligible quantity of solvents. Moreover, this reaction can be readily up-scaled to the multi-gram scale, and all synthetic operations can be carried out under atmospheric conditions without the need for complicated reaction setups. Furthermore, this force-induced system is suitable for excitation-energy-accepting molecules and poorly soluble polyaromatic substrates that are incompatible with solution-based nickel(II)/photoredox cocatalysts.     

Giant Crystalline Molecular Rotors that Operate in the Solid State

Molecular motion in the solid state is typically precluded by the highly dense environment, and only molecules with a limited range of sizes show such dynamics. Here, we demonstrate the solid-state rotational motion of two giant molecules, i.e., triptycene and pentiptycene, by encapsulating a bulky N-heterocyclic carbene (NHC) Au(I) complex in the crystalline media. To date, triptycene is the largest molecule (surface area: 245 Ų; volume: 219 ų) for which rotation has been reported in the solid state, with the largest rotational diameter among reported solid-state molecular rotors (9.5 Å). However, the pentiptycene rotator that is the subject of this study (surface area: 392 Ų; volume: 361 ų; rotational diameter: 13.0 Å) surpasses this record. Single-crystal X-ray diffraction analyses of both the developed rotors revealed that these possess sufficient free volume around the rotator. The molecular motion in the solid state was confirmed using variable-temperature solid-state ²H spin-echo NMR studies. The triptycene rotor exhibited three-fold rotation, while temperature-dependent changes of the rotational angle were observed for the pentiptycene rotor.     

Phase transition and conductive acceleration of phosphonium-cation-based room-temperature ionic liquid

An unusual ionic conduction phenomenon related to the phase transition of a novel phosphonium-cation-based room-temperature ionic liquid (RTIL) is reported; we found that in the phase change upon cooling, a clear increase in ionic conductivity was seen as the temperature was lowered, which differs from widely known conventional RTILs; clearly, our finding of abnormality of the correlation between temperature change and ionic conduction is the first observation in the electrolyte field.     

Nitrogen-15 NMR spectroscopy of N-metallated nucleic acids: insights into 15N NMR parameters and N-metal bonds

It was recently demonstrated spectroscopically that RNA/DNA nucleobases can bind to metal cations in aqueous solution through coordination bonds and covalent bonds. Nitrogen-15 ((15)N) NMR spectroscopy was employed and shown to be a powerful tool for determining the mode of metal ion binding to nitrogen atoms in RNA/DNA molecules. This review describes (15)N NMR spectroscopic characteristics in accordance with the mode of metal ion binding to nitrogen atoms. The general rules for (15)N chemical shift changes, which are applicable to the determination of the metal ion binding mode of N-metallated compounds, are also described.     

Amide I infrared spectral features characteristic of some untypical conformations appearing in the structures suggested for amyloids

Amide I infrared (IR) spectral features are studied, by using the density functional theoretical method, for two untypical (but possibly rather prevalent) structures inspired from those recently suggested for amyloids: a structure consisting of loop regions in the (alpha L, alpha R) conformation stacked to form an alpha-sheet, and a structure involving some main-chain peptide groups (of any residues) and some side-chain amide groups of glutamine and asparagine residues closely located with each other. The amide I vibrational (off-diagonal) coupling constants are examined by extracting them from the calculated Cartesian-based force constants with the average partial vector method and by comparing them with those estimated on the basis of the transition dipole coupling mechanism. It is suggested that the amide I IR band characteristic of the alpha-sheet conformation in dry environment (without hydrogen bonding to solvent water molecules) is located in a high-frequency region (approximately >1670 cm(-1), somewhat higher than that of alpha-helix), because of the dependence of the diagonal (uncoupled) frequency and the off-diagonal coupling constant on the Phi and Psi dihedral angles. It is also shown that the amide I vibrations of the closely located peptide and amide groups are strongly coupled through-space with each other, and in the presence of this type of strong vibrational coupling, a noticeable change in the IR intensity upon (13)C=O substitution may occur even for a mode that arises mainly from an unsubstituted group and is not much shifted in frequency. The meaning of these results in the interpretation of observed amide I spectral profiles, especially the possible usefulness of IR spectroscopic measurements for detecting those untypical structures in the process of amyloid formation, is also discussed.     

A note on -bases of a regular affine domain extension

Let be a tower of commutative rings where is a regular affine domain over an algebraically closed field of prime characteristic and is a regular domain. Suppose has a -basis over and . For a subset of whose elements satisfy a certain condition on linear independence, let be a set of maximal ideals of such that is a -basis of over . We shall characterize this set in a geometrical aspect.

     

Effects of dispersion stabilizer and reaction solvent on forming monodisperse polystyrene microspheres by dispersion polymerization

We used poly(aspartic acid) (PAsp) synthesized by ion exchange with sodium polyaspartate (PAspNa) as a dispersion stabilizer. PAsp improved the dispersion stability and the solubility in the medium for dispersion polymerization. The effects of the stabilizer hydrophobicity on particle formation, conversion, particle diameter, and its distribution of polystyrene microspheres were investigated by using both biodegradable polymers as a dispersion stabilizer. According to these results, we concluded that the polymerization rate of the styrene with PAsp was higher than that of styrene with PAspNa. That is why, smaller and more monodisperse microspheres were prepared with PAsp, compared to those with PAspNa.     

Evaluation method for linking methamphetamine seizures using stable carbon and nitrogen isotopic compositions: a complementary study with impurity profiling

Drug profiling, extraction of physical and/or chemical profiles from abused drug samples, is useful for inferring and characterizing links between samples originating from the same and different seizures, and supports drug crime investigations. We describe an evaluation method for linking methamphetamine (MA) seizures using stable carbon and nitrogen isotopic compositions concurrently with gas chromatographic impurity profiling, which is one of the major methods of drug profiling. Several sets of MA seized in Japan, whose investigative information indicated linkages, were analyzed. The impurity profile of each set of seizures was quite similar and hierarchical cluster analysis showed a sample classification that was relatively consistent with the investigative information. The stable carbon and nitrogen isotopic compositions of the MA seizures varied between -29.40 and -24.90 (delta(13)C) and -2.29 and 5.94 (delta(15)N), respectively. In the delta(13)C-delta(15)N graph, MA seizures were classified into seven groups, probably reflecting different origins. The size of the cluster in the isotopic-composition graph was determined by pooled standard deviations (s(p)), the pooled estimates of measurement uncertainty. The sizes of the clusters were less than 6s(p) and the linkages between the MA seizures from the isotopic compositions were consistent with the impurity profiling and investigative information. The results showed that complementary use of stable-isotopic compositions with impurity profiling provides useful information for evaluating the links between seizures.     

A reactive bond orbital investigation of the Diels-Alder reaction between 1,3-butadiene and ethylene: Energy decomposition, state correlation diagram, and electron density analyses

The reactive bond orbital (RBO) method (Hirao, Chem Phys Lett 2007, 443, 141) is extended and applied to the Diels-Alder reaction between 1,3-butadiene and ethylene, with the aim of understanding the nature of their interaction. The roles of distortion, electrostatic, exchange, polarization, and charge transfer (CT) interaction energies at the transition state of the reaction are evaluated by means of RBO energy decomposition analysis. The effects of the hypothetical interactions on electron density redistribution are also identified by analysis based on the RBO method. CT is shown to play essential roles in the new bond formation between the reacting molecules and their internal bond order alterations. However, each of the CT interactions from butadiene to ethylene and from ethylene to butadiene does not necessarily contribute to the bond-order alteration process effectively. A state correlation diagram approach based on the RBO method is also proposed, and its usefulness in understanding the origin of the barrier in the Diels-Alder reaction is demonstrated.     

Development of a two-step chromatography procedure that allows the purification of a high-purity anti-histone H1 monoclonal immunoglobulin M antibody with immunosuppressant activity

In organ transplantation, the development of a novel immunosuppressant free of the need for permanent administration and any serious side effects has eagerly been awaited. We have previously reported that an anti-histone H1 polyclonal antibody has immunosuppressant activity. Here we prepared an anti-histone H1 monoclonal antibody as an analytical tool to elucidate its mechanism of immunosuppression. The isotype of this monoclonal antibody was immunoglobulin M. A monoclonal antibody prepared for administration to organ transplantation model animals should not contain any allogenic proteins and should have high purity. Therefore, we conducted a two-step chromatography procedure, consisting of strong anion-exchange chromatography and gel filtration chromatography, to purify an anti-histone H1 monoclonal immunoglobulin M antibody from the serum-free culture supernatant of hybridomas. Consequently, we successfully purified the monoclonal antibody at 96%, a purification rate at which its administration to organ transplantation model animals is possible.