Innovative in Situ Ball Mill for X-ray Diffraction

Abstract

The renewed interest of mechanochemistry as an ecofriendly synthetic route has inspired original methodologies to probe reactions, with the aim to rationalize unknown mechanisms. Recently, Friščić et al. ( Nat. Chem. 2013 , 5 , 66 - 73 , DOI: 10.1038/nchem.1505 ) monitored the progress of milling reactions by synchrotron X-ray powder diffraction (XRPD). For the first time, it was possible to acquire directly information during a mechanochemical process. This new methodology is still in its early stages, and its development will definitively transform the fundamental understanding of mechanochemistry. A new type of in situ ball mill setup has been developed at the Materials Science beamline (Swiss Light Source, Paul Scherrer Institute, Switzerland). Its particular geometry, described here in detail, results in XRPD data displaying significantly lower background and much sharper Bragg peaks, which in turn allow more sophisticated analysis of mechanochemical processes, extending the limits of the technique.

Insight into the Mechanochemical Synthesis and Structural Evolution of Hybrid Organic–Inorganic Guanidinium Lead(II) Iodides

“…For the in situ reaction, a custom‐made jar and mill were used. They are described in detail elsewhere . The syntheses were conducted in the same way as the lab syntheses.…”

“…The setup used for the in situ measurements was described in detail elsewhere . It allows the time‐resolved investigation of mechanochemical reactions, thereby delivering highly resolved PXRD data with low backgrounds and a good signal‐to‐noise ratio.…”

The effect of ball mass on the mechanochemical transformation of a single-component organic system: anhydrous caffeine

“…These issues prompted the rapid development of techniques to probe mechanochemical reactions in situ and in real time. To date, this has been performed using X-ray powder diffraction at synchrotron sources, laboratory-based Raman spectroscopy, or a simultaneous combination of the two [3,[15][16][17][18][19]. In situ, real-time monitoring has proven a great advantage to identifying processes and control parameters in mechanochemistry.…”

The emergence of medicinal mechanochemistry

“…screening for API solid forms, organic synthesis by milling, and mechanochemical screening for molecular recognition, enables the emergence of a new research discipline in which different aspects of pharmaceutical and medicinal chemistry are addressed through solid-state reactivity, rather than the conventional solution-based routes.This nascent area of medicinal mechanochemistry [2] is likely to have a strong impact on future pharmaceutical and medicinal chemistry, by offering not only access to materials and reactivity that are sometimes difficult or even impossible to access from solution, but also by providing a general answer to the demands of pharmaceutical industry for cleaner, safer and efficient synthetic solutions. [3,4] [ The in situ characterization of materials is a widespread technique as it gives an accurate description of the sample in a particular state without disturbing the system and adding supplemental parameters/errors in the measurement. It allows to describe and understand phenomena during a process but it also plays a key role to the development of new materials.…”

“…Nevertheless, such setup has limitations: it is only adapted for high-energy synchrotron X-rays providing diffraction patterns in a squeezed Q-range with strongly overlapping Bragg peaks and does not yield high quality data. With the aim of improving such situation, we developed a completely different setup yielding higher resolution powder diffraction data and providing continuously a representative part of the bulk for probing [3,4]. The particular geometry of the ball mill designed at Materials Science beamline (SLS, Switzerland) shows a significant improvement of diffraction data quality ( Fig.1): new intermediates were precisely identified during ball milling syntheses and crystal structures might be solved from it.…”