Supramolecular interactions in the solid state

Polymorphism of a porous hydrogen bond-assisted ionic organic framework

The polymorphs of a cationic iHOF constructed by anion⋯pi interactions and the role of molecular inflexibility in framework construction are presented.

Polymorphism of a widely used building block for halogen-bonded assemblies: 1,3,5-trifluoro-2,4,6-triiodobenzene

After reporting the structure of a new polymorph of 1,3,5-trifluoro-2,4,6-triiodobenzene (denoted BzF3I3), C₆F₃I₃, (I), which crystallized in the space group P2₁/c, we perform a comparative analysis with the already reported P2₁/n polymorph, (II) [Reddy et al. (2006). Chem. Eur. J. 12, 2222-2234]. In polymorph (II), type-II I...I halogen bonds and I...π interactions connect molecules in such a way that a three-dimensional structure is formed; however, the way in which molecules are connected in polymorph (I), through type-II I...I halogen bonds and π-π interactions, gives rise to an exfoldable lamellar structure, which looks less tightly bound than that of (II). In agreement with this structural observation, both the melting point and the melting enthalpy of (I) are lower than those of (II).

Kinetic assembly of coordination networks

Kinetic assembly is an important method for obtaining desired materials in chemical synthesis and materials science. We highlight the kinetic assembly of porous coordination networks, which promote the production of interactive pore sites. The interactive pore sites can activate or stabilize guest molecules. The properties of interactive pores are typified by iodine chemisorption and small sulfur encapsulation. Using interactive pores, we trapped small sulfur allotropes, such as S₂, cyclo-S₃, bent-S₃, and S₆, demonstrating the importance of interactive pore sites. Here, we address the important aspects of interactive pore sites created by kinetic assembly of porous coordination networks.

Isomorphous crystal structures of chlorodi-acetyl-ene and iododi-acetyl-ene derivatives: simultaneous hydrogen and halogen bonds on carbon-yl

The crystal structures of tert-butyl (5-chloro-penta-2,4-diyn-1-yl)carbamate, C10H12ClNO2 (II), and tert-butyl (5-iodo-penta-2,4-diyn-1-yl)carbamate, C10H12INO2 (IV), are isomorphous to previously reported structures and accordingly their mol-ecular and supra-molecular structures are similar. In the crystals of (II) and (IV), mol-ecules are linked into very similar two-dimensional wall organizations with anti-parallel carbamate groups involved in a combination of hydrogen and halogen bonds (bifurcated N-H⋯O=C and C≡C-X⋯O=C inter-actions on the same carbonyl group). There is no long-range parallel stacking of diynes, so the topochemical polymerization of di-acetyl-ene is prevented. A Cambridge Structural Database search revealed that C≡C-X⋯O=C contacts shorter than the sum of the van der Waals radii are scarce (only one structure for the C≡C-Cl⋯O=C inter-action and 13 structures for the similar C≡C-I⋯O=C inter-action).

Supramolecular networks in molecular complexes of pyridine boronic acids and polycarboxylic acids: synthesis, structural characterization and fluorescence properties

3- and 4-pyridineboronic acids have been combined with trimesic and pyromellitic acids to give three molecular complexes.

A quantitative measure of halogen bond activation in cocrystallization

Calculated energy profiles for XB show the activating effect of ring substituents. The results match the outcome of experimental studies by Aakeröy et al. Cryst.Growth Des., 2015, 15, 3853.

Generation of crystal structures using known crystal structures as analogues

This analysis attempts to answer the question of whether similar molecules crystallize in a similar manner. An analysis of structures in the Cambridge Structural Database shows that the answer is yes - sometimes they do, particularly for single-component structures. However, one does need to define what we mean by similar in both cases. Building on this observation we then demonstrate how this correlation between shape similarity and packing similarity can be used to generate potential lattices for molecules with no known crystal structure. Simple intermolecular interaction potentials can be used to minimize these potential lattices. Finally we discuss the many limitations of this approach.

High pressure Raman spectra of monoglycine nitrate single crystal

Single crystal of monoglycine nitrate has been studied by Raman spectroscopy under high pressures up to 5.5 GPa. The results show changes in lattice modes in the pressure ranges of 1.1-1.6 GPa and 4.0-4.6 GPa. The first change occurs with appearance of bands related to the lattice modes as well as discontinuity in the slope of dΩ/dP of these modes. Moreover, bands associated with the skeleton of glycine suggest that the molecule undergoes conformational modifications. The appearance of a strong band at 55 cm(-1) point to a second phase transition associated with the lattice modes, while the internal modes remain unchanged. These anomalies are probably due to rearrangement of hydrogen bonds. Additionally, decompression to ambient pressure shows that the phase transitions are reversible. Finally, the results show that the nitrate anions play an important role on the stability of the monoglycine nitrate crystal.

Quaternary cocrystals: combinatorial synthetic strategies based on long-range synthon Aufbau modules (LSAM)

A synthetic strategy is outlined whereby a binary cocrystal may be developed in turn into a ternary and finally into a quaternary cocrystal. The strategy hinges on the concept of the long-range synthon Aufbau module (LSAM) which is a large supramolecular synthon containing more than one type of intermolecular interaction. Modulation of these interactions may be possible with the use of additional molecular components so that higher level cocrystals are produced. We report six quaternary cocrystals here. All are obtained as nearly exclusive crystallization products when four appropriate solid compounds are taken together in solution for crystallization.

Giant strain geared to transformable H-bonded network in compressed β-d-mannose

The clearly visible shape change of β-d-mannose crystals is associated with pressure-induced isostructural phase transition.

A halogen bond does not dictate the conformational preferences of cis-1,3-disubstituted cyclohexanes

A halogen bond is unlikely to control the conformation of cis-1,3-disubstituted cyclohexanes. In addition, polarization rather than the σ-hole effect describes this weak interaction more appropriately.

Positive and negative linear compressibility and electronic properties of energetic and porous hybrid crystals with nitrate anions

Within the framework of DFT-D calculations, the compressibility anisotropy of UN and DATN energetic nitrates and the Ag(en)N hybrid crystal is established.