Patrick J. Beldon

Real-time and in situ monitoring of mechanochemical milling reactions

Chemical and structural transformations have long been carried out by milling. Such mechanochemical steps are now ubiquitous in a number of industries (such as the pharmaceutical, chemical and metallurgical industries), and are emerging as excellent environmentally friendly alternatives to solution-based syntheses. However, mechanochemical transformations are typically difficult to monitor in real time, which leaves a large gap in the mechanistic understanding required for their development. We now report the real-time study of mechanochemical transformations in a ball mill by means of in situ diffraction of high-energy synchrotron X-rays. Focusing on the mechanosynthesis of metal-organic frameworks, we have directly monitored reaction profiles, the formation of intermediates, and interconversions of framework topologies. Our results reveal that mechanochemistry is highly dynamic, with reaction rates comparable to or greater than those in solution. The technique also enabled us to probe directly how catalytic additives recently introduced in the mechanosynthesis of metal-organic frameworks, such as organic liquids or ionic species, change the reactivity pathways and kinetics.

Rapid Room‐Temperature Synthesis of Zeolitic Imidazolate Frameworks by Using Mechanochemistry

Freshly ground: Improved mechanochemical methodologies, such as liquid-assisted grinding and ion- and liquid-assisted grinding enable the rapid and topologically selective synthesis of porous and nonporous zeolitic imidazolate frameworks with diverse topologies, at room temperature and directly from zinc oxide.

Facile mechanosynthesis of amorphous zeolitic imidazolate frameworks.

A fast and efficient mechanosynthesis (ball-milling) method of preparing amorphous zeolitic imidazolate frameworks (ZIFs) from different starting materials is discussed. Using X-ray total scattering, N(2) sorption analysis, and gas pycnometry, these frameworks are indistinguishable from one another and from temperature-amorphized ZIFs. Gas sorption analysis also confirms that they are nonporous once formed, in contrast to activated ZIF-4, which displays interesting gate-opening behavior. Nanoparticles of a prototypical nanoporous substituted ZIF, ZIF-8, were also prepared and shown to undergo amorphization.

Real-time in situ powder X-ray diffraction monitoring of mechanochemical synthesis of pharmaceutical cocrystals.

Looking in: The penetrating power of high-energy X-rays provides a means to monitor in situ and in real time the course of ball-milling reactions of organic pharmaceutical solids by detecting crystalline phases and assessing the evolution of their particle sizes. Upon switching from neat grinding to liquid-assisted grinding, cocrystal formation is enabled or tremendously accelerated, while the reaction mechanism alters its course.

In situ and real-time monitoring of mechanochemical milling reactions using synchrotron X-ray diffraction

We describe the only currently available protocol for in situ, real-time monitoring of mechanochemical reactions and intermediates by X-ray powder diffraction. Although mechanochemical reactions (inducing transformations by mechanical forces such as grinding and milling) are normally performed in commercially available milling assemblies, such equipment does not permit direct reaction monitoring. We now describe the design and in-house modification of milling equipment that allows the reaction jars of the operating mill to be placed in the path of a high-energy (∼90 keV) synchrotron X-ray beam while the reaction is taking place. Resulting data are analyzed using conventional software, such as TOPAS. Reaction intermediates and products are identified using the Cambridge Structural Database or Inorganic Crystal Structure Database. Reactions are analyzed by fitting the time-resolved diffractograms using structureless Pawley refinement for crystalline phases that are not fully structurally characterized (such as porous frameworks with disordered guests), or the Rietveld method for solids with fully determined crystal structures (metal oxides, coordination polymers).

Fabrication of Magnetic Barcoded Microcarriers for Biomolecular Labeling: SU‐8 Encapsulated Magnetic Tags

Rows of rectangular magnetic elements with different aspect ratio are encapsulated in polymer microcarriers to form a novel magnetic label, or tag, for multiplexed biological and chemical assays. We demonstrate that each tag can be encoded using an external magnetic field applied to the whole tag, which will allow for in‐flow writing, thanks to shape‐anisotropy controlled coercivity of the individual bits. This paper focuses on the fabrication of our 2nd generation tags, which facilitate optical trapping, do not require a sacrificial release layer, and the alignment procedure has been simplified to a single step. A new procedure is described for recovering a functional surface from fully cross‐linked SU‐8 via a cerium (IV) ammonium nitrate based chemical etch, and a novel method for releasing patterned photoresist from a bare Si wafer is discussed. In addition, a series of homobifunctional amine spacer compounds are compared as a method of increasing the binding efficiency of surface probe molecules.

Transition metal coordination complexes of chrysazin

Eleven novel coordination compounds, composed of chrysazin (1,8-dihydroxyanthraquinone) and different first-row transition metals (Fe, Co, Ni, Cu), were synthesised and the structures determined by single-crystal X-ray diffraction. The synthetic trends were investigated using high-throughput synthesis under systematic variation of concentration and reagent stoichiometry: for complexes containing Co, Ni or Cu crystallisation was improved by low ligand : metal ratios, while the effect of concentration depended on the metal used. The compounds crystallise as discrete clusters, apart from two, which contain long Cu–O bonds which may allow the two compounds to be considered one-dimensional coordination polymers. One of these compounds shows a distance between aryl rings of less than 3.26 A, which is shorter than that in graphite, suggesting applications as an organic–inorganic semiconductor. The compound was found to be insulating by single-crystal and powder AC-impedance measurements, and this result is discussed with reference to the electronic structure calculated using density-functional theory.