Hirokazu Nakayama

Structural study of phosphate groups in layered metal phosphates byhigh-resolution solid-state31P NMR spectroscopy

In studies of a series of crystals of layered metal phosphate compounds by magic angle spinning (MAS) NMR spectroscopy, it has been found that there is a distinct correlation between the 31 P isotropic chemical shift value and the type of phosphate group. The isotropic 31 P chemical shifts of (H 2 PO 4 ) - , (HPO 4 ) 2- and (PO 4 ) 3- groups appear around δ -10, -20 and -30, respectively. These assignments were made unambiguously by measuring the 31 P MAS NMR spectra with and without 1 H high-power decoupling together with the cross-polarization transfer technique between 1 H and 31 P nuclei (CP MAS spectra).

Adsorption of formaldehyde by polyamine-intercalated α-zirconium phosphate

Gaseous formaldehyde adsorption mechanism of diethylenetriamine- and pentaethylenehexamine-intercalated α-zirconium phosphate was demonstrated to be self oxidation-reduction of formaldehyde, that is, Cannizzaro reaction, in the interlayer space as evidenced by XRD and solid-state NMR. This fact suggests that these intercalation compounds can be used as a reaction field of self oxidation-reduction of formaldehyde, and also as adsorbents of formaldehyde, which causes sick-house syndrome.

Keggin-type polyacid clusters on apatite: characteristic catalytic activities in solvent-free oxidation

We found that Keggin-type phosphometalates are effective catalysts for solvent-free oxidation with urea–H2O2 by dispersing on fluorapatite solid phase. In the solid phase system the phosphomolybdate (NH4)3PMo12O40 was more effective than the phosphotungstate (NH4)3PW12O40, whereas the latter was much superior to the former in the liquid-phase reaction with aqueous H2O2. In situ formation of novel peroxo-type species from (NH4)3PMo12O40/FAp and urea–H2O2, which may lead to the high catalytic activity in the solid phase system, was observed by 31P solid-state NMR.

Molecular Motions and Phase Transitions in Solid CH3NH3PbX3 (X = C1, Br, I) as Studied by NMR and NQR

Abstract The temperature dependence of 35C1, 81Br, and 127I NQR frequencies and 1Hspin-lattice relaxation times (T1) for CH3NH3PbX3 (X = Cl, Br, I) was measured through the successive phase transitions in these solids. The isotropic reorientation of the CH3NH3 ions takes place in the higher-temperature phases (tetragonal [I4/mcm] and cubic) of the three salts (Ea= 11 kJ mol -1). T1s in the lowest-temperature phases (orthorhombic) indicate that the cations undergo correlated C3-reorientation in the chloride (Ea = 5.45 kJ mol -1)and in the iodide (Ea = 5.80 kJ mol -1, whereas correlated (Ea = 2.40 kJ mol-1) and uncorrected (Ea = 7.50 kJ mol-1) C3- reorientations are excited in the bromide. It is also revealed that the rotational tunneling of the cations governs T1 at lowtemperature region in the orthorhombic phases of these salts

Positron annihilation and 129Xe NMR studies of free volume in polymers

Abstract The existence and the average size of free volume in bisphenol-A polycarbonate (PC), low-density polyethylene (LDPE), poly (2,6-dimethyl-phenyleneoxide)(PPO), and polytetrafluoroethylene (PTFE) were studied by positron annihilation and 129 Xe NMR measurements. The 129 Xe NMR chemical shifts for xenon adsorbed in the polymers indicated that the average pore size of the free volume increased in the following order: PC, LDPE, PPO, and PTFE. This order of the pore size of the free volume agrees well with that estimated from the longest lifetime ( τ 3 ) of ortho -positronium formed in the polymers. The unique correlation that δ −1 ∝ r is established between the 129 Xe NMR chemical shift ( δ ) and the pore size ( r ), which is deduced from the positron annihilation measurements.

Unusual adsorption mechanism for carboxylic acid gases by polyamine-intercalated α-zirconium phosphate

The adsorption mechanism of gaseous carboxylic acid by diethylenetriamine- or pentaethylenehexamine-intercalated α-zirconium phosphate was examined in detail using XRD and solid-state 13C and 31P NMR. The adsorption of acetic acid, propanoic acid, and butyric acid resulted in the co-intercalation of the carboxylic acid molecules into polyamine-intercalated α-zirconium phosphate to expand their interlayer distance by 0.64–0.97 nm. In the case of formic acid, its adsorption induced the rearrangement of the polyamine molecules within the interlayer space.

A one-step phosphorylation of d-aldohexoses and d-aldopentoses with inorganic cyclo-triphosphate

The phosphorylation reaction by inorganic cyclo-triphosphate (P3m) having a six-membered ring was examined for D-aldohexoses and D-aldopentoses in aqueous solution. Similar to the process for D-glucose, D-galactose, D-xylose or D-allose were phosphorylated with P3m to give stereoselectively beta-D-galactopyranosyl 1-triphosphate, beta-D-xylopyranosyl 1-triphosphate or beta-D-allopyranosyl 1-triphosphate with maximum yields of 31.3, 32.5 or 32.1%, respectively. On the other hand, in the reaction of D-ribose, D-lyxose, D-mannose or D-arabinose with P3m, the yields of beta-D-ribopyranosyl 1-triphosphate, alpha-D-lyxopyranosyl 1-triphosphate, alpha-D-mannopyranosyl 1-triphosphate or alpha-D-arabinopyranosyl 1-triphosphate were 8.0, 16.5, 9.6 or 14.1%, respectively. The phosphorylation mechanism of D-aldopyranoses with P3m was also discussed.

Stereoselective phosphorylation of branched cyclodextrins with inorganic cyclo-triphosphate

The phosphorylation by inorganic sodium cyclo-triphosphate (P(3m)) having a six-membered ring was examined for cyclomaltohexaose (alpha-cyclodextrin) and branched cyclodextrins (mono-6-O-alpha-D-glucopyranosylcyclomaltohexaose, mono-6-O-alpha-D-maltosylcyclomaltohexaose, mono-6-O-alpha-D-glucopyranosylcyclomaltoheptaose, and mono-6-O-alpha-D-maltosylcyclomaltoheptaose) in aqueous solution. For all cyclomaltooligosaccharides (cyclodextrins) studied, the 2-OH group was stereoselectively phosphorylated. In the reaction of branched cyclodextrins and P(3m), only the 2-OH on the alpha-D-glucopyranosyl group of the cyclodextrin rings was phosphorylated with maximum yields of more than 27%. The phosphorylation mechanism of branched cyclodextrins with P(3m) is also discussed.

Adsorption of Carboxylic Acids by Diethylenetriamine Intercalation Compound of α-Zr(HPO4)2 · H2O

Abstract Two kinds of diethylenetriamine (2E3A) intercalation compounds of α-zirconium phosphate with different interlayer distances could be obtained by regulating the reaction time and temperature. Phase I (d = 10.2 Å) slowly transforms to Phase II(d = 15. 8 Å) with transformation enthalpy of 30 kJ-mol−1 in 2E3A aqueous solution. The conformation of 2E3A in Phase I and Phase II were confirmed to be bent and all trans (straight) forms by31P MAS NMR and XRD measurements. Two phases have different adsorption behavior for gaseous carboxylic acids. Phase II can adsorb considerable amount of carboxylic acids whereas Phase I adsorb a little.

Proton magnetic resonance of CnH2n+2(n= 1–4) adsorbed in mordenite. Dynamic behaviour and host–guest interaction

Proton spin–lattice relaxation times, T1, for methane, ethane, propane and butane adsorbed in mordenite have been measured in situ over wide ranges of temperature and loading. The spin–lattice relaxation was found to be governed by the reorientation of the guest molecules in the low-temperature region. No phase transition was observed between 4.2 K and room temperature. The results also revealed that methane molecules are distributed between the main channel and the side-pocket of the host mordenite, whereas ethane, propane and butane are accommodated only in the main channel. For the molecules accommodated in the main channel the activation energy for reorientation (methane: 1.0 kJ mol–1, ethane: 1.0 kJ mol–1, propane: 3.5 kJ mol–1, butane: 5.0–5.5 kJ mol–1) and the temperature at which the T1 minimum appears increase systematically with the size of the guest molecule, suggesting that the potential barrier for reorientation originates from the steric host–guest interaction.