J. Appl. Cryst.の発刊に際して

Interpretation of europium(III) spectra

: The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

The organoselenium and organotellurium compounds have been described as promising pharmacological agents in view of their unique biological properties. Glutathione peroxidase mimic, antioxidant activity and thioredoxin reductase inhibition are some of the properties reviewed here. On the other hand, little is known about the molecular toxicological effects of organoselenium and organotellurium compounds. Most of our knowledge arose from research on inorganic selenium and tellurium. However, the ability to oxidize sulfhydryl groups from biological molecules can be involved both in their pharmacological properties and in their toxicological effects. In fact, exposition to high doses of organoselenium or to low doses of organotellurium causes the depletion of endogenous reduced glutathione in a variety of tissues. Thus, the design of compounds that cause low depletion of glutathione and react with specific targeted proteins, controlling specific metabolic pathways, will represent an important progress in understanding the field of organochalcogen compounds. Furthermore, the development of new organochalcogens with higher thiol-peroxidase activity that can use other non-toxic thiol reducing agents, such as N-acetylcysteine instead of glutathione, will permit the investigation of the co-administration of organochalcogens and thiols as a formulation for antioxidant therapy.

Organoselenium and Organotellurium Compounds: Toxicology and Pharmacology

New Self-Assembled Structural Motifs in Coordination Chemistry.

Luminescence and structure of europium compounds

Crystal engineers aim to control the way molecules aggregate in the crystalline phase and are therefore concerned with crystal structure prediction, polymorphism, and discovering the relative importance of different types of intermolecular forces and their influence on molecular structure. In order to design crystal structures, knowledge of the types, strengths, and nature of possible intermolecular interactions is essential. Non-covalent interactions involving p-systems is a theme that is under extensive investigation as these interactions can be inductors for the assembly of a vast array of supramolecular architectures.

The Importance of Pi-Interactions in Crystal Engineering: Frontiers in Crystal Engineering

Emerging supramolecular synthons: C–H⋯π(chelate) interactions in metal bis(1,1-dithiolates)

Abstract What might very well be classified as a revolution in chemical crystallography is the emergence of crystal engineering as a discipline and the pivotal role X-ray crystallography plays in this [1]. Although dating back to the 1950's, the field has exploded in the last decade or so, and now is at the forefront of contemporary chemical and cognisant research. One of the areas in crystal engineering of greatest potential impact relates to the pharmaceutical industry – drug formulation and intellectual property – where issues relating to crystallisation, polymorphism, etc. are paramount [2]. A focus of these crystal engineering studies relates to the preparation of multi-component crystals, often referred to as co-crystals, where, for example utilizing hydrogen bonding synthons, active pharmaceutical ingredients are co-crystallised with other molecules [2]. The motivation for such studies is to improve stability (e.g. shelf-life), bioavailability (e.g. solubility), etc. [3].

What is a co-crystal?

A search of the Cambridge Structural Database (CSD) was performed to identify Te⋯π-aryl interactions not reported before in the literature. The examination of the distance between tellurium atoms and aryl group centroids and the analysis of crystal packing, using deposited crystal structure data, produced a list of organotellurium compounds which showed a variety of Te⋯π bonding interactions. These include inter-ionic Te⋯π interactions in anion–cation ion pairs, intramolecular Te⋯π-aryl interactions in mono- and di-nuclear covalent molecular compounds, as well as in dimeric and tetrameric supermolecules or in supramolecular polymeric arrays formed through secondary bonds. Most interesting was the finding that intermolecular Te⋯π aryl interactions can connect molecular tectons, leading to supramolecular self-assembly with formation of dimeric and polymeric superstructures. Finally, Te⋯π aryl interactions may
interconnect polymeric chains formed through Te⋯X secondary bonds into 2D and perhaps 3D networks. Thus, the Te⋯aryl interactions appear as a new bonding motif for supramolecular self-assembly, which could be exploited for crystal engineering in organotellurium chemistry, i.e. for the design of new materials with attractive useful properties.

Julio Zukerman-Schpector

Papers

Luminescence and structure of europium compounds

The Importance of Pi-Interactions in Crystal Engineering: Frontiers in Crystal Engineering

Emerging supramolecular synthons: C–H⋯π(chelate) interactions in metal bis(1,1-dithiolates)

What is a co-crystal?

Tellurium⋯π-aryl interactions: a new bonding motif for supramolecular self-assembly and crystal engineering