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The high-pressure solid solution and compression behavior of hydroxides in the ternary MgSiO 4 H 2 -AlOOH-FeOOH system were studied at pressures of 16-60 GPa and temperatures of 300-1513 K. We applied in situ X-ray measurements in conjunction with a multianvil apparatus using sintered diamond anvils to achieve homogeneous temperature distributions within large sample volumes. Our results show that CaCl 2 -type hydroxides form solid solutions over a wide composition range. We also observed the volume reductions in the solid solutions accompanied by a spin transition of iron at~50 GPa, and the wide compositional ranges are maintained through this process. Consequently, water may be transported into the deep lower mantle by the hydrous CaCl 2 -type solid solution with changing its composition depending on the chemical and thermal environments.Plain Language Summary A significant amount of water has been transported into the Earth's interior via subduction of hydrous phases in cold plates since plate tectonics started to operate billions of years ago. Recent theoretical and experimental studies revealed that hydrous phases with compositions of MgSiO 4 H 2 , AlOOH, and FeOOH are stable at the high pressures occurring in the lower mantle, suggesting that a certain amount of water may be delivered to the core-mantle boundary (~2,900-km depth). However, hydroxides in multicomponent systems relevant to the actual mantle and subducting slabs are not well studied. Here we compressed multicomponent hydroxides in the ternary MgSiO 4 H 2 -AlOOH-FeOOH system using multianvil technology and found that hydroxide subducted into the lower mantle can retain Earth's major elements, such as Mg, Si, Al, Fe, and O. Key Points:• The solid solution and compression behavior of hydroxides were studied by in situ X-ray measurements and a multianvil press • CaCl 2 -type hydroxides form solid solutions over a wide composition range in the MgSiO 4 H 2 -AlOOH-FeOOH system • The volume of CaCl 2 -type hydroxides decreases due to a spin transition of iron at~50 GPa Supporting Information:• Supporting Information S1Correspondence to: M. Nishi,

The synthesis and optical, electrochemical, and magnetic properties of nickel(II) complexes of 5,10,20-triaryl-5,15-diazaporphyrin (TriADAP) are reported. Metal-templated cyclization of unsymmetrically substituted nickel(II)–bis(1-amino-9-chloro-5-mesityldipyrrin; mesityl = 2,4,6-trimethylphenyl) complexes afforded the corresponding TriADAPs or 5-aryl-15-benzyl-10,20-dimesityl-5,15-diazaporphyrin, depending on the combination of base and solvent. The latter macrocycle was converted to TriADAP by deprotection of the [Formula: see text]-benzyl group through Pd/C-promoted hydrogenation. TriADAPs were isolated in both 18[Formula: see text] (cation) and 19[Formula: see text] (neutral) forms. The interconversion between these two oxidation states resulted in a distinct change in the optical properties of the DAP [Formula: see text]-system. NMR spectroscopy of the 18[Formula: see text] TriADAP cations showed that they had aromatic character, whereas EPR spectroscopy of the 19[Formula: see text] TriADAP showed a highly delocalized electron spin of the [Formula: see text]-radical. The para substituents of the [Formula: see text]-aryl groups of TriADAPs had a small but distinct impact on their HOMO and LUMO energies. The change in the net charge of one electron was directly reflected in the redox properties of the DAP ring; TriADAP was more easily reduced and less easily oxidized than DAP. The difference in the net charge was also reflected by the shielding of the pyrrolic [Formula: see text]-protons observed in the [Formula: see text]H NMR spectra. The present results confirm that TriADAP is a highly promising framework for constructing a new class of azaporphyrin-based materials with 18[Formula: see text]–19[Formula: see text] redox-switchable optical and magnetic properties.

The catalyst-free hydrosilylation of CO 2 under mild conditions remains limited. Herein, we report the synthesis, characterization, and reactivity of 5,10,15,20-tetraphenylporphyrinato(dihydrido)silicon(IV)(1)a sas ix-coordinate silicon dihydride. The Si-H moiety of 1 reacts with polar double bonds and CO 2 in the absence of ac atalyst to afford hydrosilylated products. Combining the hydrosilylation with subsequentt ransformation furnishes formic acidf rom CO 2 .C omputational studies indicate that the hydride-donorp roperties of 1 are exceptionally high for an eutrals ilicon hydride, and that the directh ydride transfer from silicon to carbon is ap ivotal step in the hydrosilylation of CO 2 with 1.

Water transportation to the deep lower mantle via plate subduction may induce a reaction between water and iron at the core-mantle boundary. Recent experimental studies suggest that such a reaction may generate FeO 2 H x-rich domains, which can explain the seismic structures of the ultralow velocity zone in this region. In this study, the chemical reaction between metallic iron and a limited water supply at~120 GPa was investigated using time-resolved in situ synchrotron X-ray diffraction measurements in combination with the laser-heated diamond anvil cell technique. Contrary to the results of earlier studies, the formation of FeO instead of FeO 2 H x without intermediate phases was observed. Considering the unlimited availability of iron in the core and the limited water supply resulting from mantle downflow, the FeO-rich layers consisted of Fe-bearing ferropericlase and postperovskite, which must have locally cumulated at the bottom of the mantle simultaneously with hydrogen incorporation into the core. Plain Language Summary Water strongly influences the structure, dynamics, and evolution of the deep Earth. Recent experimental studies suggest that hydrous phases play an important role as carriers of surface water to the deep mantle via the subduction of oceanic plates. Such deep-water subduction processes may allow the surface water to reach the bottom of the mantle, where the mantle minerals are in direct contact with the iron at the core. Thus, the purpose of this study was to provide understanding regarding the behavior of water when it meets iron at the core-mantle boundary. To investigate the reaction between water and iron at high pressures and temperatures, experiments were performed using in situ X-ray diffraction measurements in combination with the diamond-anvil cell technique. The results obtained confirmed the formation of FeO during the reaction. Thus, the deep water cycle may produce FeO-rich layers at the core-mantle boundary, which may explain the seismic characteristics of the bottom of the mantle and at the top of the outer core.