The need for a new generation of substructure searching software

Advances in synthetic chemistry mean that the molecules now synthesized include increasingly complex entities with mechanical bonds or extensive frameworks. For these complex molecular and supramolecular species, single-crystal X-ray crystallography has proved to be the optimal technique for determining full three-dimensional structures in the solid state. These structures are curated and placed in structural databases, the most comprehensive of which (for organic and metallo–organic structures) is the Cambridge Structural Database. A question of increasing importance is how users can search such databases effectively for these structures. Here some of the classes of complex molecules and supramolecules and the challenges associated with searching for them are highlighted. The idea of substructure searches that involve topological searches as well as searches for molecular fragments is developed, and significant enhancements are proposed to substructure search programs that are both achievable and highly beneficial for both the database user community and the broader chemistry community.

Mechanochemical synthesis of mechanical bonds in M12L8 poly-[n]-catenanes.

Using mechanochemistry by grinding TPB and ZnBr2 an amorphous poly-[n]-catenane of interlocked M12L8 nanocages is obtained in good yields (⁓ 80 %) and within 15 minutes. The mechanical bond among...

Coordination assembly and host–guest chemistry of a triply interlocked [2]catenane

Triply catenated systems composed of two or more discrete coordination-metal cages through mechanical bonds exhibit excellent host–guest behaviors, which can be potentially applied in drug delivery systems.

STUDY OF THE DEFORMED STATE CONNECTION OF THE PISTON WITH THE ROD OF THE UNREGULATED PISTON PUMP

The technological processes of cold rolling of precision workpieces and ring parts, rolling of pipes, rolling of piston-connecting rod axial-rotor piston pump, which are a kind of processing of metals by pressure and contain changes in the shape of workpieces according to performing relative to the axis of the workpiece radial rotational motion. The workpiece can remain stationary or rotate. It is shown that by means of technological process of rolling of pipes, unrolling of preparations various hollow axisymmetric metal products receive, the specified processes are combined by the mechanism of deformation, namely: at them two deformations of compression and one - tension are realized. This mechanical deformation scheme creates favorable conditions for plastic deformation, because intercrystalline displacements are difficult, leading to the violation of mechanical bonds, and plastic deformation occurs mainly due to intracrystalline displacements. It is shown that in the process of connecting the piston-connecting rod in compliance with the process parameters (output supply pressure, feed rate, leaving time) the value of the specified gap either exceeds the maximum value or decreases to the value at which the next operation of the piston-connecting rod spell. The deformed state in the technological operation of rolling the piston-connecting rod pair at different stages of shape change is studied, the process control mechanism is revealed, which prevents the defect in the form of deviation from the regulated gap after rolling between the piston and the connecting rod. The used resource of plasticity at different stages of rolling is calculated, the deformability of the piston workpiece in the rolling process is estimated.

Mechanical bonds and dynamic covalent bonds

Jishan Wu and Fraser Stoddart introduce the Materials Chemistry Frontiers themed collection on mechanical bonds and dynamic covalent bonds.

Nanohoop Rotaxanes via Active Template Syntheses and Their Potential in Sensing Applications

<p>The synthesis of nanohoop rotaxanes via two different active template strategies is reported. By preparing triazole-embedded rotaxanes, the observation of metal binding events in both organic and aqueous conditions are readily observed via dramatic changes in nanohoop emission. Inspired by this result, we then describe the design and synthesis of a new type of "self-destructing" nanohoop rotaxane that, in the presence of an analyte, releases a quenched nanohoop macrocycle resulting in a bright fluorescence response. More broadly, this work highlights the conceptual advantages of combining compact π-rich macrocyclic frameworks with mechanical bonds formed via active-template syntheses. </p><p></p>

Nanohoop Rotaxanes via Active Template Syntheses and Their Potential in Sensing Applications

<p>The synthesis of nanohoop rotaxanes via two different active template strategies is reported. By preparing triazole-embedded rotaxanes, the observation of metal binding events in both organic and aqueous conditions are readily observed via dramatic changes in nanohoop emission. Inspired by this result, we then describe the design and synthesis of a new type of "self-destructing" nanohoop rotaxane that, in the presence of an analyte, releases a quenched nanohoop macrocycle resulting in a bright fluorescence response. More broadly, this work highlights the conceptual advantages of combining compact π-rich macrocyclic frameworks with mechanical bonds formed via active-template syntheses. </p><p></p>

A comprehensive study of the molecular vibrations in solid-state benzylic amide [2]catenane

In this work we record and assign the infrared spectrum of benzylic amide [2]catenane, a molecular solid owning mechanical bonds. By means of first-principles calculations we analyze over 1000 normal modes in terms of the usual internal coordinates.

Displacement assay methodology for pseudorotaxane formation in the millisecond time-scale

Rotaxanes, formed by an axis through the cavity of a macrocycle, are promising systems for the construction of molecular machines. A very limited number of experimental techniques are available for mechanistic studies since only mechanical bonds are formed, being NMR one of the most widely used. The major inconvenience derived from NMR use is the time-scale for threading/dethreading processes lasting a few minutes in the case of faster processes. In the present manuscript, we report the application of a new kinetic methodology based on a displacement assay for cyclodextrin-based pseudorotaxane formation. By coupling a very fast (microseconds time-scale) binding/dissociation of nitrophenol to α-CD with a dicationic axle threading/dethreading process, we have been able to study kinetic processes taking place in the millisecond time-scale.