Chemistry and crystal engineering

Recent studies published in the Chemistry and crystal engineering section of IUCrJ emphasize developments both in methodology and techniques as well as the diverse range of classes of compounds being studied and of problems being tackled.

Chromic and dynamic: soft crystals of platinum(II) complexes pave the way for multi-responsive materials

The development of smart, stimuli-responsive materials has received increased attention in the past decade for their applications as sensing technologies. This commentary discusses a timely topical review by Kato [(2024). IUCrJ, 11, 442–452] on the fabrication of multi-stimuli responsive crystals comprised of luminescent platinum(II) complexes, which exhibit intriguing chromic phenomena in response to stimuli.

Exploring crystal structure–physical property relationships with pressure

From its conception, X-ray crystallography has provided a unique understanding of the structure, bonding and electronic state of materials, which, in turn, unlocks a means of examining the properties and function of crystalline systems. Using state-of-the-art single-crystal X-ray diffraction, along with UV–Vis spectroscopy and DFT calculations, Zwolenik et al. [(2024). IUCrJ, 11, 519–527] have provided a comprehensive study of the structure–optical property relationship of 1,3-di­acetyl­pyrene with methodologies that are increasingly accessible to non-specialist laboratories.

Relating solvatochromism and solvatomorphism in organic dyes using high pressure

By using complementary experimental methods including in situ high-pressure single-crystal X-ray diffraction and UV–Vis spectroscopy, the intricate connection between solvatochromism and solvatomorphism has been elucidated in a recent publication [Sobczak & Katrusiak (2024). IUCrJ, 11, 528–537]. The connection was demonstrated for an important pigment – Reichardt's dye – with potential applications in nonlinear optoelectronics and molecular pressure sensor development.

Chromic soft crystals based on luminescent platinum(II) complexes

Platinum(II) complexes exhibit intense luminescence based on their molecular arrangement and chromic luminescence, which is a color change in response to gentle stimuli such as vapor exposure or weak mechanical forces. Both the molecular and the crystal designs for soft crystals are critical to effectively control the chromic phenomenon of platinum(II) complexes.

The importance of definitions in crystallography

This paper proposes a rigorous definition of a periodic structure as an equivalence class of periodic sets under rigid motion, which is a composition of translations and rotations.

The evolution of raw data archiving and the growth of its importance in crystallography

The IUCr 75th Congress in Melbourne hosted a workshop on raw data reuse, continuing efforts to promote discussions and plans within crystallography, diffraction and scattering communities. These initiatives build on earlier IUCr funded workshops, aiming to establish ground truth obtained from research results through raw data archiving potential.

Bridging the microscopic divide: a comprehensive overview of micro-crystallization and in vivo crystallography

The 26th IUCr congress held in Melbourne brought discussions on micro-crystallization and in vivo crystallography within structural biology to the forefront, highlighting innovative approaches and collaborative efforts to advance macromolecular research.

Photoinduced bidirectional mesophase transition in vesicles containing azo­benzene amphiphiles

In this work, a reversible non-invasive light-induced mesophase transition from lamellar to cubic Pn3m is observed in mixed azo­benzene-lipid and phospho­lipid vesicles using small-angle X-ray scattering.

Comprehensive encoding of conformational and compositional protein structural ensembles through the mmCIF data structure

Traditional structural models of biomolecules typically represent only a single conformational state, even though biomolecules naturally exist in multiple states crucial for their function. Here, we propose enhancements to the macromolecular crystallographic information file (mmCIF) to better capture the complex conformational and compositional heterogeneity of biomolecules that is human- and machine-interpretable.

A step towards 6D WAXD tensor tomography

A novel approach is reported for 6D wide-angle X-ray diffraction tensor tomography characterization based on the concept of virtual reciprocal-space scanning.

Analysis of COF-300 synthesis: probing degradation processes and 3D electron diffraction structure

Detailed analysis of the influence of time and temperature on the synthesis of COF-300 showed partial linker degradation but still allowed 3D electron diffraction structure solution using optimized conditions.

Evolution of structure and spectroscopic properties of a new 1,3-di­acetylpyrene polymorph with temperature and pressure

A new polymorph of 1,3-diacetylpyrene that is luminescent in the solid state and a prominent negative thermal expansion material has been obtained from its melt. A thorough structural characterization of this new crystal form was performed in a wide temperature and pressure range using single-crystal X-ray diffraction. Structural studies have been combined with steady-state UV–Vis spectroscopy and periodic density functional theory calculations. A previously published methodology of crystal placement in a diamond anvil cell has been successfully applied in predicting optimal 2°AP-β sample orientation, ensuring >80% data coverage and enabling unrestrained Hirshfeld atom refinements for high-pressure structures as well as analysis of anharmonic oscillations.

Structural insight into piezo-solvatochromism of Reichardt's dye

This work employs the preference of compounds to crystallize at high-pressure in the form of solvates to explore the solvation process and piezo-solvatochromic effects of Reichardt's dye, ET(1). The solute–solvent interactions of this dye affect the optical properties of the dye in various solvents as shown by X-ray diffraction and UV–Vis spectroscopy, revealing applications in nonlinear optoelectronics and molecular pressure sensor development.

Crystal structure via fluctuation scattering

Fluctuation X-ray scattering measures the correlation of scattered X-rays in diffraction experiments. Here, the Bragg peak intensity from fluctuation X-ray scattering correlations is recovered using an iterative algorithm.

From X-ray crystallographic structure to intrinsic thermodynamics of protein–ligand binding using carbonic anhydrase isozymes as a model system

Rational drug discovery and design require a deep understanding of the structure and thermodynamics of protein–ligand interactions. Here, the human carbonic anhydrase family of enzymes and their specific sulfonamide ligands are used to describe binding assays and crystal structures for understanding of protein–compound recognition principles.

Scanning WAXS microscopy of regenerated cellulose fibers at mesoscopic resolution

Scanning WAXS microscopy of a regenerated cellulose textile fiber reveals a radial gradient in the degree of orientation of the crystallite.

Statistical optimization of guest uptake in crystalline sponges: grading structural outcomes

A statistical design of experiments approach applied to crystalline sponge analysis enables greater understanding of experimental influences and the development of a novel molecular structure quality grading system.

A modified phase-retrieval algorithm to facilitate automatic de novo macromolecular structure determination in single-wavelength anomalous diffraction

A modified phase-retrieval algorithm has been built on the framework of the relaxed alternating averaged reflection (RAAR) algorithm, incorporating the π-half phase perturbation for weak reflections and the direct-methods based tangent formula for strong reflections in reciprocal space. The modified phase-retrieval algorithm exhibits significantly improved effectiveness and accuracy of various forms of SAD substructure determination to facilitate automatic de novo macromolecular structure determination.

A predicted model-aided reconstruction algorithm for X-ray free-electron laser single-particle imaging

A predicted model-aided reconstruction algorithm is proposed for orientation determination and phase retrieval in X-ray free-electron laser single-particle imaging. The predicted model-aided algorithm exhibits significant improvements in the success rate, accuracy and efficiency of the reconstruction process.

High-accuracy measurement, advanced theory and analysis of the evolution of satellite transitions in manganese Kα using XR-HERFD

Here, the n = 2 satellite present for manganese-containing materials and across materials science has been successfully observed by applying the new technique of extended-range high-energy-resolution fluorescence detection (XR-HERFD), developed from high-resolution resonant inelastic X-ray scattering and HERFD, and the spectra have been predicted with new advanced theory.

Crystallographic phase identifier of a convolutional self-attention neural network (CPICANN) on powder diffraction patterns

The development of CPICANN, a novel convolutional self-attention neural network, represents a groundbreaking approach in materials informatics. By leveraging the convolutional self-attention mechanism, CPICANN automates and significantly enhances the efficiency of crystal phase identification from whole X-ray powder diffraction patterns, marking a substantial advancement over traditional time-consuming methods.

In some cases more complicated approaches to refinement of macromolecular structures are not necessary

The manuscript `Modeling a unit cell: crystallographic refinement procedure using the biomolecular MD simulation platform Amber' presents a novel protein structure refinement method claimed to offer improvements over traditional techniques like Refmac5 and Phenix. Our re-evaluation suggests that while the new method provides improvements, traditional methods achieve comparable results with less computational effort.