Where are the lone pairs? QC and QCT

The article by Guzmán-Hernández & Jancik [(2024). Acta Cryst. C80, 766–774] is an excellent example of how QC–QCT (quantum crystallography–quantum chemical topology) methodology can extract structural information from a crystal.

Crystal structure of submicron-sized sulfur particles using 3D ED obtained in atmospheric conditions

The structure solution and refinement from three-dimensional electron diffraction (3D ED) data of elemental sulfur, known to sublimate in the vacuum of transmission electron microscopes, is enabled through the use of an environmental cell with a micro-electromechanical system. This work represents the first step in characterizing sulfur's transformation into lithium polysulfides using in-situ 3D ED.

Conformational versatility among crystalline solids of L-phenyl­alanine derivatives

We present the synthesis and characterization of four new crystalline forms of an N-derivative of L-phenyl­alanine with 2-naphthaldehyde, where the com­pound adopts different unfolded and folded conformations depending on its charge state and the supra­molecular environment. To characterize and classify such conformational differences, we propose the use of a dimensionless Shape Factor qu­antity defined as the Structural Aspect Ratio (SA_R), which proves to be a simple but useful tool for this purpose, and its application could be extended to other conformational studies.

Monoprotonated species of 2-amino­malonyl difluoride, [C₃H₄F₂NO₂][H₂F₃]

The monoprotonated species of 2-amino­malonyl difluoride, [C₃H₄F₂NO₂][H₂F₃], is particularly inter­esting for the protonation in superacidic media, as well as in Lewis acidic media, due to its two acyl fluoride moieties. The crystal structure is the first single-crystal X-ray diffraction measurement of this com­pound or its salts.

Synthesis and diverse crystal packing in o-, m- and p-bis­(carbonyl­thio­ureido)benzenes containing bis­ferrocenes

Three bis­(acyl­thio­urea) positional isomers containing two ferrocenyl groups were synthesized and characterized by X-ray diffraction. Their various noncovalent inter­actions and crystal assemblies have been investigated.

Structural investigations of benzoyl fluoride and the benzo­acyl cation of low-melting com­pounds and reactive inter­mediates

Acyl cations exist as short-living species in organic reactions starting from the corresponding acyl chloride or acyl fluoride. Benzoyl fluoride and the benzo­acyl­ium cation are highly reactive and sensitive com­pounds. The first structure determination of the low-melting fluoride and its corresponding acyl­ium cation uncovers their crystal structures, built up by various C⋯F contacts, as well as different kind of π-inter­actions.

On the de­pro­ton­ation of chloro­thia­zide

The structures of the Na and K salt forms of chloro­thia­zide have been re-investigated and are found to have different hydration states and de­pro­ton­ation sites from those described previously. The structure of the Cs salt form is found to contain the same anion as in the new models for the Na and K salt forms.

Polymorphism in a secondary phosphine

Bis(2,3,5,6-tetra­methyl­phen­yl)phosphine is the first secondary phosphine known to exhibit polymorphism and is observed to form two different crystal structures depending on the solvent of crystallization. As structures of these reactive com­pounds are somewhat rare in the literature, this study expands the sum of structural knowledge of secondary phosphines, as well as revealing aspects of their supra­molecular chemistry.