J. Appl. Cryst.の発刊に際して

The halogen bond occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a halogen atom in a molecular entity and a nucleophilic region in another, or the same, molecular entity. In this fairly extensive review, after a brief history of the interaction, we will provide the reader with a snapshot of where the research on the halogen bond is now, and, perhaps, where it is going. The specific advantages brought up by a design based on the use of the halogen bond will be demonstrated in quite different fields spanning from material sciences to biomolecular recognition and drug design.

The Halogen Bond

Publisher Summary This review is concerned with the neglected class of inorganic compounds, which contain ions of the same element in two different formal states of oxidation. Although the number of references cited in our review show that many individual examples of this class have been studied, yet they have very rarely been treated as a class, and there has never before, to our knowledge, been a systematic attempt to classify their properties in terms of their electronic and molecular structures. In the past, systems containing an element in two different states of oxidation have gone by various names, the terms “mixed valence,” nonintegral valence,” “mixed oxidation,” “oscillating valency,” and “controlled valency” being used interchangeably. Actually, none of these is completely accurate or all-embracing, but in our hope to avoid the introduction of yet another definition, we have somewhat arbitrarily adopted the phrase “mixed valence” for the description of these systems. The concept of resonance among various valence bond structures is one of the cornerstones of modern organic chemistry.

Mixed Valence Chemistry-A Survey and Classification

Crystal polymorphism is encountered in all areas of research involving solid substances. Its occurrence introduces complications during manufacturing processes and adds another dimension to the complexity of designing materials with specific properties. Research on polymorphism is fraught with unique difficulties due to the subtlety of polymorphic transformations and the inadvertent formation of pseudopolymorphs. In this report, a summary of thermodynamic, kinetic and structural considerations of polymorphism is presented. A wide variety of techniques appropriate to the study of organic crystalline polymorphism and pseu-dopolymorphism is then surveyed, ranging from simple crystal density measurement to observation of polymorphic transformations using variable-temperature synchrotron X-ray diffraction methods. Application of newer methodology described in this report is yielding fresh insights into the nature of the crystallization process, holding promise for a deeper understanding of the phenomenon of polymorphism and its practical control.

Crystalline Polymorphism of Organic Compounds

Dendrimers in Supramolecular Chemistry: From Molecular Recognition to Self-Assembly.

As part of an investigation of the solid-state intermolecular contacts in which the nitrile group participates, the crystal structures of p-cyano-N-(p-cyanobenzylideneaniline), C15H9N3 (CN/CN) and 4,4′-(azinodimethylidyne)bis-benzonitrile, C16H10N4 (CN//CN) have been determined at −100 °C. Cell parameters for CN/CN: a = 4.7270(9) A, b = 10.443(2) A, c = 11.943(2) A; α = 90°, β = 98.70(3)°, γ = 90°; monoclinic, space group P21/c. Cell parameters for CN//CN: a = 3.8008(8) A, b = 7.9627(16) A, c = 11.181(2) A; α = 70.23(3)°, β = 84.66(3)°, γ = 81.93(3)°; triclinic, space group $$ P\overline{1} $$
 . Both molecules occupy crystallographic inversion centers, which requires that (CN/CN) be disordered. Both molecules assume nearly planar conformations in the solid state. Neither (CN/CN) nor (CN//CN) is isostructural with its halogen-nitrile substituted analogues, although (CN/CN) is found to be isostructural with the corresponding stilbene. Both (CN/CN) and (CN//CN) engage in centrosymmetric H-bonding interactions that define an R
 2
 2
 (10) motif. This motif is also observed in many related structures, although noteworthy exceptions can be found. In the crystal structures of p-cyano-N-(p-cyanobenzylideneaniline), C15H9N3 (CN/CN) (a disordered structure) and 4,4′-(azinodimethylidyne)bis-benzonitrile, C16H10N4 (CN//CN), nitrile groups are found to engage in centrosymmetric H-bonding interactions with aromatic ring hydrogen atoms, defining an R
 2
 2
 (10) motif in each case.

Solid-State Intermolecular Contacts Involving the Nitrile Group in p -Cyano- N -( p -cyanobenzylidene)aniline and 4,4′-(azinodimethylidyne) bis -benzonitrile

Benzfuroxans. The Crystal and Molecular Structure of 5-Chlorobenzfurazan 1-Oxide and 5-Bromobenzfurazan 1-Oxide1

Four complexes of CuCN with imidazoles have been prepared by adding the ligand to a solution of CuCN in aqueous sodium thiosulfate. The imidazole ligands used were 2-methylimidazole (mim), 1,2-dimethylimidazole (dmim), 5-chloro-1-methylimidazole (clmim), and 2-phenylimidazole (phim). Complex 1, (CuCN)(mim) is monoclinic, C2/c, a = 9.565(3), b = 7.764(5), c = 8.983(8) A, β = 96.76(3)°, Z, = 4, Complex 2, (CuCN)(dmim) is monoclinic, P21/c, a = 8.120(2), b = 11.796(4), c = 16.375(9) A, β, = 100.87(4)°, Z = 8. Complex 3, (CuCN) (clmim) is monoclinic, C2/c, a = 24.907(4), b = 6.894(5), c = 18.259(4) A, β = 102.79(2)°, Z = 16. Complex 4, (CuCN)(phim) is orthorhombic, Pca21, a = 9.204(4), b = 8.125(2), c = 26.304(6) A, Z, = 8. Complexes 1, 2, and 4 have one-dimensional chains –Cu–CN–Cu– with an imidazole bonded to each Cu. Complex 3 has a two-dimensional sheet of CuCN, again with an imidazole bonded to each Cu. In 1 the imidazole group is disordered by a two-fold rotation approximately around the N···N direction in the imidazole group. In 3 one of the imidazole groups has a disorder involving exchange of the Cl and CH3.

Crystal structures of four complexes produced by reaction of copper(I) cyanide with imidazoles

The reaction of both histamine (hista) and cysteine (cys) with aqueous CuCN/S2O32- produced Cu(II) ion. In the histamine case thiocyanate ion was also created leading to the production of Cu(SCN)2(hista)2. With cysteine, the 2-amino-2-thiazoline-4-carboxylic acid (atca) ligand was created leading to the production of Cu(atca)2(H2O). The crystal structures of the two complexes are discussed, and pathways for the production of thiocyanate and the atca ligand are proposed.

Copper(II) Complexes of Histamine and Cysteine Produced by Thiosulfate-Assisted Synthesis Using Copper(I) Cyanide. The in Situ Formation of the Thiocyanate Anion and the 2-Amino-2-thiazoline-4-carboxylic Acid Ligand

Tetra­fluoro­di­iodo­benzene and di­methyl sulfoxide (DMSO) crystallize in a 1/1 complex, C6F4I2·C2H6OS, in space group Pbca. Infinite ⋯C6I⋯O⋯IC6I⋯ chains are held together by strong I⋯O contacts. The DMSO mol­ecules, which lie on mirror planes, are disordered, giving rise to two I⋯O contacts of 2.898 (9) and 2.803 (10) A, both with approximately linear C—I⋯O arrangements. The C6F4I2 mol­ecules lie on inversion centers.

Doyle Britton

Papers

Solid-State Intermolecular Contacts Involving the Nitrile Group in p -Cyano- N -( p -cyanobenzylidene)aniline and 4,4′-(azinodimethylidyne) bis -benzonitrile

Benzfuroxans. The Crystal and Molecular Structure of 5-Chlorobenzfurazan 1-Oxide and 5-Bromobenzfurazan 1-Oxide1

Crystal structures of four complexes produced by reaction of copper(I) cyanide with imidazoles

Copper(II) Complexes of Histamine and Cysteine Produced by Thiosulfate-Assisted Synthesis Using Copper(I) Cyanide. The in Situ Formation of the Thiocyanate Anion and the 2-Amino-2-thiazoline-4-carboxylic Acid Ligand

2,3,5,6-Tetrafluoro-1,4-diiodobenzene–dimethyl sulfoxide (1/1)

Doyle Britton

Papers

Solid-State Intermolecular Contacts Involving the Nitrile Group in p -Cyano- N -( p -cyanobenzylidene)aniline and 4,4′-(azinodimethylidyne) bis -benzonitrile

Benzfuroxans. The Crystal and Molecular Structure of 5-Chlorobenzfurazan 1-Oxide and 5-Bromobenzfurazan 1-Oxide1

Crystal structures of four complexes produced by reaction of copper(I) cyanide with imidazoles

Copper(II) Complexes of Histamine and Cysteine Produced by Thiosulfate-Assisted Synthesis Using Copper(I) Cyanide. The in Situ Formation of the Thiocyanate Anion and the 2-Amino-2-thiazoline-4-carboxylic Acid Ligand

2,3,5,6-Tetra­fluoro-1,4-di­iodo­benzene–di­methyl sulfoxide (1/1)

2,3,5,6-Tetrafluoro-1,4-diiodobenzene–dimethyl sulfoxide (1/1)