Properties of Water Confined in Periodic Mesoporous Organosilicas: Nanoimprinting the Local Structure

The properties of materials confined in porous media are important in scientific and technological aspects. Topology, size, and surface polarity of the pores play a critical role in the confinement effects, however, knowledge regarding the guest–pore interface structure is still lacking. Herein, we show that the molecular mobility of water confined in periodic mesoporous organosilicas (PMOs) is influenced by the polarity of the organic moiety. Multidimensional solid‐state NMR spectroscopy directly probes the spatial arrangement of water inside the pores, showing that water interacts either with only the silicate layer or with both silicate and organic layers depending on the alternating surface polarity. A modulated and a uniform pore filling mode are proposed for different types of PMOs.     

Solution Mediated Synthesis and Structure of the First Anionic Bis‐( hexaborato)‐Zincate Prepared in the Presence of an Organic Amine

A room temperature reaction of zinc acetate, tributyl borate and N, N, N′N′‐tetramethylethylenediamine (tmen) in a mixture of water and 1‐butanol has given rise to a new bis‐(hexaborato)‐zincate, [(Me)₂NH(CH₂)₂NH(Me)₂][{Zn(B₆O₇(OH)₆}₂]·2H₂O ( I ). The structure, determined by single crystal X‐ray diffraction, (P1, a = 8.3014(2), b = 9.2489(2), c = 10.442(2)Å, α = 107.71(3), β = 94.22(3), γ = 100.02(3)°, V = 749.6(3)Å^{3 =} Z = 1, R₁ = 0.0387, wR₂ = 0.105), consists of anionic molecular Zn hexaborate units forming a herringbone arrangement, through strong hydrogen bond interactions, with the amine molecule situated between the chains. Compound I is the first bis‐(hexaborato)‐zincate, to our knowledge, that has been synthesized in the presence of an organic amine.     

The Rules in the Geometric Structure of Tetrahedral (Td) Nanocarbons

The main purpose of this article is to find the rules for the geometric structure of the tetrahedral (T_d) nanocarbons. Also, we would like to demonstrate the ways that we derive the formulas for these rules by simple figures and illustrations. We hope that with these derived formulas of the rules, we will be able to derive all types of the Tetrahedral Nanocarbon Clusters (without consideration for the case of distortion).     

The Structure of Mn(acac)3—Experimental Evidence of a Static Jahn–Teller Effect in the Gas Phase

The structure of free manganese(III) tris(acetylacetonate) [Mn(acac)₃] was determined by mass‐spectrometrically controlled gas‐phase electron diffraction. The vapor of Mn(acac)₃ at 125(5) °C is composed of a single conformer of Mn(acac)₃ in C₂ symmetry with the central structural motif of a tetragonal elongated MnO₆ octahedron and 47(2) mol % of acetylacetone (Hacac) formed by partial thermal decomposition of Mn(acac)₃. Three types of Mn−O separations have been refined (r_h1=2.157(16), 1.946(5), and 1.932(5) Å. We have found no indication for a significant deviation of the ‐C−C−C−O−Mn−O‐ six‐membered rings from planarity, which is observed in the solid state.     

Methanolysis of Pyrazinecarbonitrile in the Coordination Sphere of Copper(II). The Crystal Structure of Dichlorobis(O-Methylpyrazinecarboximidate)-Copper(II) Dihydrate

Abstract

Reaction of pyrazinecarbonitrile (pz-CN) with copper(II) in methanol solution led to formation of solid complexes containing O-methylpyrazinecarboximidate (pz-C(NH)OMe) as a ligand. The analogous reaction of pyrazinecarbonitrile in ethanol led to isolation of solid complexes containing unchanged pz-CN. Six novel copper(II) compounds have been obtained under various reaction conditions. Their stereochemistry and the mode of ligand coordination has been determined by spectroscopic and conductometric measurements. Moreover, the crystal structure of the complex [CuCl₂(O-methylpyrazinecarboximidate)₂]. 2H₂O has been determined by X-ray diffraction techniques.     

The crystal and molecular structure of sodium 4‐(2,4,6‐triisopropylbenzoyl)benzoate in terms of the photochemical behaviour of the anion

Contrary to the known 4‐(2,4,6‐triisopropylbenzoyl)benzoate salts, di‐μ‐aqua‐bis[tetraaquasodium(I)] bis[4‐(2,4,6‐triisopropylbenzoyl)benzoate] dihydrate, [Na₂(H₂O)₁₀](C₂₃H₂₇O₃)₂·2H₂O, (1), does not undergo a photochemical Norrish–Yang reaction in the crystalline state. In order to explain this photochemical inactivity, the intermolecular interactions were analyzed by means of the Hirshfeld surface and intramolecular geometrical parameters describing the possibility of a Norrish–Yang reaction were calculated. The reasons for the behaviour of the title salt are similar crystalline environments for both the o‐isopropyl groups in the anion, resulting in similar geometrical parameters and orientations, and that these interaction distances differ significantly from those found in salts where the photochemical reaction occurs.