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Synthesis and Crystal Structures of 1,1′-Methylene-bis(imidazolidine-2,4-dione) and Alkali Metal Salts

Author(s):Robert Salchner -- Volker Kahlenberg -- Roman Lackner -- Klaus Wurst -- Doris Braun -- Gerhard Laus -- Herwig Schottenberger
Journal: Crystals
Publisher:
Abstract
| Pages: 1-10
Single-crystal structures of 1,1′-methylenebis(imidazolidine-2,4-dione) and its sodium and dipotassium salts were determined. Powder X-ray diffraction was also employed to characterize the bulk materials and those phases which did not yield single-crystals. These compounds are of interest for intumescent coatings.

Acknowledgement to Reviewers of Crystals in 2013

Author(s):Crystals Editorial Office
Journal: Crystals
Publisher:
Abstract
| Pages: 11-11
The editors of Crystals would like to express their sincere gratitude to the following reviewers for assessing manuscripts in 2013. [...]  

σ-Hole Interactions of Covalently-Bonded Nitrogen, Phosphorus and Arsenic: A Survey of Crystal Structures

Author(s):Peter Politzer -- Jane S. Murray -- Goran V. Janjić -- Snežana D. Zarić
Journal: Crystals
Publisher:
Abstract
| Pages: 12-31
Covalently-bonded atoms of Groups IV–VII tend to have anisotropic charge distributions, the electronic densities being less on the extensions of the bonds (σ-holes) than in the intervening regions. These σ-holes often give rise to positive electrostatic potentials through which the atom can interact attractively and highly directionally with negative sites (e.g., lone pairs, π electrons and anions), forming noncovalent complexes. For Group VII this is called “halogen bonding” and has been widely studied both computationally and experimentally. For Groups IV–VI, it is only since 2007 that positive σ-holes have been recognized as explaining many noncovalent interactions that have in some instances long been known experimentally. There is considerable experimental evidence for such interactions involving groups IV and VI, particularly in the form of surveys of crystal structures. However we have found less extensive evidence for Group V. Accordingly we have now conducted a survey of the Cambridge Structural Database for crystalline close contacts of trivalent nitrogen, phosphorus and arsenic with six different types of electronegative atoms in neighboring molecules. We have found numerous close contacts that fit the criteria for σ-hole interactions. Some of these are discussed in detail; in two instances, computed molecular electrostatic potentials are presented.

Dimensionality Variation in Dinuclear Cu(II) Complexes of a Heterotritopic Pyrazolate Ligand

Author(s):Chris S. Hawes -- Paul E. Kruger
Journal: Crystals
Publisher:
Abstract
| Pages: 32-41
Two new Cu(II) complexes of the ligand 3-carboxy-5-(2-pyridyl)-1H-pyrazole, H2L1, have been prepared and structurally characterized and found to be comprised of a similar [M2L2] dimer motif. Subtle variation in the synthetic conditions allowed isolation of two metal complexes: [Cu2L12(MeOH)2], 1, a discrete dimer linked by hydrogen bonding interactions in the solid state, and poly-[Cu2L12], 2, a polymeric material where the dimer motif is linked by carboxylate bridges to give an extended two-dimensional sheet. The selective isolation of each phase by careful synthetic control highlights the subtlety and importance of the underlying synthetic conditions.

Structural Variation in Polyoxomolybdate Hybrid Crystals Comprising Ionic-Liquid Surfactants

Author(s):Takeru Ito -- Keisuke Mikurube -- Kimiko Hasegawa -- Takashi Matsumoto -- Kurato Kosaka -- Haruo Naruke -- Shinichi Koguchi
Journal: Crystals
Publisher:
Abstract
| Pages: 42-52
Polyoxomolybdate inorganic-organic hybrid crystals were synthesized with 1-decyl-3-methylimidazolium and 1-dodecyl-3-methylimidazolium as ionic-liquid surfactants. Both hybrid crystals possessed alternate stacking of surfactant layers and octamolybdate (Mo8) monolayers, while the molecular structures of Mo8 were different depending on the surfactants and solvents employed for crystallization. Each Mo8 anion was connected by two sodium cations to form infinite one-dimensional chain. The surfactant chains in these crystals were arranged in a complicatedly bent manner, which will be induced by the weak C–H···O hydrogen bonds between the Mo8 anions and ionic-liquid surfactants.

Hydrogen-Bonding Motifs in Piperazinediium Salts

Author(s):Chris S. Hawes -- Cherry Chen -- Andrew Tran -- David R. Turner
Journal: Crystals
Publisher:
Abstract
| Pages: 53-63
Four novel organic salts of piperazine and 2-methylpiperazine with p-toluenesulfonic acid and chloroacetic acid have been synthesized and structurally characterized. The hydrogen-bonding ring synthons that exist between the cation/anion pairs are compared and contrasted alongside database results.

Polyoxotungstates in Molecular Boxes of Purine Bases

Author(s):Vladislav Kulikov -- Gerd Meyer
Journal: Crystals
Publisher:
Abstract
| Pages: 64-73
Three new compounds, (GuaH)4[W10O32](H2O)4 (1), (ThbH)3(H3O)[(W10O32](H2O)7.5 (2) and (ThbH)2[W6O19](H2O)2 (3) (GuaH = guaninium, thbH = theobrominium) were synthesized in acidified acetonitrile solutions. The polyoxotungstates in all of these compounds are surrounded by an organic matrix consisting of protonated purine bases and water molecules. The distinctive structural arrangement of the aromatic organic cations around the polyoxoanions parallel to their faces is reminiscent of nanosized boxes. The results of IR spectroscopy are consistent with previously reported results for polyoxotungstates and neat organic compounds. The polyoxoanions are reduced to tungsten(IV) oxide upon heating over 400 °C in an intramolecular redox reaction.

Compressed Air Energy Storage System Control and Performance Assessment Using Energy Harvested Index

Author(s):Hanif SedighNejad -- Tariq Iqbal -- John Quaicoe
Journal: Electronics
Publisher:
Abstract
| Pages: 1-21
In this paper a new concept for control and performance assessment of compressed air energy storage (CAES) systems in a hybrid energy system is introduced. The proposed criterion, based on the concept of energy harvest index (HEI), measures the capability of a storage system to capture renewable energy. The overall efficiency of the CAES system and optimum control and design from the technical and economic point of view is presented. A possible application of this idea is an isolated community with significant wind energy resource. A case study reveals the usefulness of the proposed criterion in design, control and implementation of a small CAES system in a hybrid power system (HPM) for an isolated community. Energy harvested index and its effectiveness in increasing the wind penetration rate in the total energy production is discussed.

Carbon Nanoelectronics

Author(s):Cory D. Cress
Journal: Electronics
Publisher:
Abstract
| Pages: 22-25
Initiated by the first single-walled carbon nanotube (SWCNT) transistors [1,2], and reinvigorated with the isolation of graphene [3], the field of carbon-based nanoscale electronic devices and components (Carbon Nanoelectronics for short) has developed at a blistering pace [4]. Comprising a vast number of scientists and engineers that span materials science, physics, chemistry, and electronics, this field seeks to provide an evolutionary transition path to address the fundamental scaling limitations of silicon CMOS [5]. Concurrently, researchers are actively investigating the use of carbon nanomaterials in applications including back-end interconnects, high-speed optoelectronic applications [6], spin-transport [7], spin tunnel barrier [8], flexible electronics, and many more. [...]
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