Crystal Engineering: Strategies and Architectures

This review takes a look at some of the strategies that have been devised for research in crystal engineering, in particular, those based around hydrogen-bonded architectures. In addition, some of the history and possibilites of the field itself are alluded to.

Structural Model of the Orthorhombic Non-Fibonacci Approximant in the Al₁₂Fe₂Cr Alloy

A structural model of the orthorhombic approximant (Imm2, a = 12.34, b = 12.41, c = 30.71Å) of the Al₁₂Fe₂Cr decagonal quasicrystal has been derived from its high-resolution electron microscopic images.

Phase Transition in K₃Na(MoO₄)₂ and Determination of the Twinned Structures of K₃Na(MoO₄)₂ and K_2.5Na_1.5(MoO₄)₂ at Room Temperature

K₃Na(MoO₄)₂ and K_2.5Na_1.5(MoO₄)₂ are monoclinic distorted glaserite structures. The excessive Na in K_2.5Na_1.5(MoO₄)₂ occupies the position of a more firmly bound potassium in the structure.

Structure of Two Disordered Molybdates, Li₂Mo^IVO₃ and Li₄Mo₃^IVO₈, from Total Neutron Scattering

Analysis of total neutron scattering data has enabled us to determine the correct local structures in Li₂MoO₃ and Li₄Mo₃O₈ – two compounds containing Mo–Mo-bonded triangular clusters. The shortcomings of analysing only Bragg scattering in the structure determination of disordered materials are demonstrated.

Penta­chloro­toluene: Rotational and Compositional Disorder

Crystals of pentachlorotoluene are, like crystals of most other hexasubstituted chloromethylbenzenes, rotationally disordered. Compositional disorder may also be a problem.

Cleavage and Twinning in CuInSe₂ Crystals

In Bridgman-grown monocrystals of CuInSe₂, it has been found that the main cleavage planes are (101) and (112) and that twinning occurs along {112} planes about a [221] axis.

Li⁺/Na⁺ β-Alumina: A Combined Single-Crystal Neutron and X-ray Diffraction Study

The crystal structure of the ionic conductor Li⁺/Na⁺ β-alumina has been studied at 30 and 298K with single-crystal X-ray diffraction and at 295K with neutron diffraction. The results reveal a complex ionic distribution of Li⁺ and Na⁺ ions.

X-ray Study of M^II(ClO₄)₂.6H₂O (M^II = Zn, Ni): Twinning, Disorder and Phase Transitions

High-temperature phases of Zn(ClO₄)₂.6H₂O and Ni(ClO₄)₂.- 6H₂O, two pseudohexagonal crystals with three orthorhombic twin components, have been studied by X-ray diffraction. Correlated disorder after temperature cycling has disappeared.

Low-Temperature Neutron Diffraction Study of the Silver Perchlorate–Benzene π Complex

The crystal structure of the AgClO₄.C₆H₆ complex, determined earlier by X-ray diffraction at room temperature, has been redetermined at 18, 78 and 158 K by neutron diffraction. Distortions of the benzene molecule from D_6h symmetry ascribed to Ag⁺⋯C₆H₆ interactions are small, yet still significant.

Structures and Magnetic Properties of Dimeric Copper(II) Benzoylformates

Dimeric copper(II) benzoylformates show unusually strong antiferromagnetic interactions (-2J = ca 650 cm⁻¹; H= -2JS₁.S₂), which may be due to the electronic effect of the α-keto group in the bridging carboxylate moiety. In the binuclear cage structure the coordination geometry around Cu^II atoms is typical square pyramidal.

Molecular Motion and Conformational Interconversion of Azo­benzenes in Crystals as Studied by X-ray Diffraction

Variable-temperature X-ray structure analysis of azobenzenes reveals that the torsional vibration of the N—Ph bonds is large enough to give rise to conformational interconversion in crystals.

Disorder in Cyclodextrin Clathrates: X-ray Diffuse Scattering Analysis of α-Cyclodextrin Cyclo­pentanone Hydrate

The diffuse scattering analysis of the α-cyclodextrin cyclopentanone hydrate has revealed a variety of disorder phenomena; the interpretation of the results (structure in domains, intercell, vacancies and twin lattices) helps to explain the rotational disorder of the guest and some observed strains of the average structure. The correlated disorder phenomena are limited to small domains (with dimensions 10² or 10³Å); the description of these domains suggests how crystals grow.

Resonance-Induced Hydrogen Bonding at Sulfur Acceptors in R₁R₂C=S and R₁CS₂⁻ Systems

The frequency of formation and geometries of R₁R₂C=S⋯H-N,O systems show that these hydrogen bonds are resonance induced; the effective electronegativity of S is increased by conjugative interactions between C=S and substituent atoms (particularly N) or unsaturated groups at R₁R₂. Distance comparisons and acceptor `competition' studies involving >C=O⋯ H-N,O analogues show that C=S forms weaker hydrogen bonds than C=O.

Hydrogen-Bond Acceptor and Donor Properties of Divalent Sulfur (Y-S-Z and R-S-H)

The frequency of formation and the geometries of >S⋯H-N,O hydrogen bonds show that these bonds are both rare and very weak. Hydrogen bonds involving -S-H donors are, however, quite common, although weaker than analogous bonds involving O-H donors.

Chiral Molecular Alloys: Patterson-Search Structure Determination of L-Carvone and DL-Carvone from X-ray Powder Diffraction Data at 218 K

The crystal structures of pure L-carvone (C₁₀H₁₄O) and a DL-carvone equimolar mixture have been determined by Patterson-search methods at low resolution from powder diffraction data at 218 K. The mixed crystal formation in the chiral carvone system is confirmed, as proposed in recent thermodynamic studies.

A Study of Diastereomeric Mandelate Salts of Cinchonidine and the Relation to Their Quasidiastereomeric Analogues

The crystal packing of the diastereomeric mandelate salts of cinchonidine does not show the expected quasidiastereomeric relationship with the equivalent cinchoninium mandelate salts. The ineffectiveness of cinchonidine as a resolving agent for mandelic acid may be attributed to the isomorphism of the diastereomeric salts.

Conformation-Related Reaction Efficiency of Glutarimides with Phenyllithium. Structures of 3,3,5,5-Tetra­methylglutarimide and 2-Hy­droxy-2-phenyl-3,3,5,5-tetra­methyl-6-piperidone. X-ray and Theoretical Study

Crystallographic and ab initio studies have clarified the reason for yield variations in the reaction of differently substituted glutarimides with phenyllithium. It has been shown that conformational changes in glutarimide, introduced by substitution, resulted in electron charge distribution changes.

Distribution of Molecular Centres in Crystallographic Unit Cells

A survey of the positions of molecular centres in common space groups shows distinct patterns of preferred locations. There is a tendency for molecules to pack in patterns similar to ideal packing of spheres.

Elements of inorganic structural chemistry. Selected efforts to predict structural features by E. Parthé

Designing the molecular world: chemistry at the frontier edited by P. Ball

Crystallography in modern chemistry by T. C. W. Mak and G.-D. Zhou

Collected works of Dorothy Crowfoot Hodgkin. Vol. I. Insulin. Vol. II. Cholestrol, penicillin and other antibiotics. Vol. III. General crystallography and essays edited by G. G. Dodson, J. P. Glusker, S. Ramaseshan and K. Venkatesan