Characterization of Silanol Groups in Protonated Magadiite by 1H and 2H Solid-State Nuclear Magnetic Resonance
Silanol groups in protonated magadiite (H-magadiite) were characterized by 1H and 2H solid-state nuclear magnetic resonance (NMR). H-magadiite and deuterated (D) magadiite were synthesized by the treatment of Na-rich magadiite with 0.2 N HC1 and 0.2 N DC1, respectively. In the ’H NMR spectrum measured at room temperature, silanol groups of H-magadiite showed two signals at 3.75 and 5.70 ppm, indicating that two types of silanol groups were present. The ratio of silanol groups associated with strong hydrogen bonding (5.70 ppm) to those with weaker hydrogen bonding (3.75 ppm) was 2 to 1. The 2H NMR spectra of deuterated magadiite were measured in the temperature range from 150 to 440 K. In the spectra measured at temperatures below 294 K, silanol groups showed Pake doublet patterns. These patterns were composed of two components corresponding to the two types of silanol groups shown in the ‘H NMR analysis. Both silanol groups produced wobbling motions with increasing temperature. Above 294 K, the profile of the Pake doublet pattern was transformed gradually to a near triangular pattern, indicating that the silanol groups underwent other motions also, such as a two-site jump.
Synthesis and visible-light photochromism of a new composite based on polymolybdate enclosed in magadiite.
A new composite based on polymolybdate incorporated in layered magadiite has been synthesized via a exfoliation/self-assembly process. Various techniques, including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy coupled with energy-dispersive X-ray analysis (SEM-EDX), Raman spectroscopy, thermogravimetric (TG) analysis, UV-vis spectroscopy, and transmission electron microscopy (TEM), have been employed to characterize the composite. Results indicated that the polymolybdate particles were incorporated into the layered magadiite. Upon the irradiation of visible light (420-630 nm), the composite changed color from yellow to dark blue; moreover, the color can be bleached upon exposure to a 15% H2O2 solution. The visible-light illumination and H2O2 treatment can be repeated in excess of 10 times. The mechanism of photochromism has been investigated, and the reversibility is attributed to the hydration property of host magadiite and oxidative ability of H2O2 solution.
Phloroglucinol derivatives from Hypericum japonicum.
The isolation and identification of a new phloroglucinol derivative (2), a diterpenol (4), together with the known compounds flavesone (1) and sarothralen B (3), from the aerial parts of Hypericum japonicum are reported. Their structures were established by extensive spectral analysis and the structure of (3) has also been confirmed by a single crystal X-ray determination.