Selective, robust and cost-effective chemical sensors for detecting small volatile-organic compounds (VOCs) have widespread applications in industry, healthcare and environmental monitoring. Here we design a Pt(II) pincer-type material with selective absorptive and emissive responses to methanol and water. The yellow anhydrous form converts reversibly on a subsecond timescale to a red hydrate in the presence of parts-per-thousand levels of atmospheric water vapour. Exposure to methanol induces a similarly-rapid and reversible colour change to a blue methanol solvate. Stable smart coatings on glass demonstrate robust switching over 10⁴ cycles, and flexible microporous polymer membranes incorporating microcrystals of the complex show identical vapochromic behaviour. The rapid vapochromic response can be rationalised from the crystal structure, and in combination with quantum-chemical modelling, we provide a complete microscopic picture of the switching mechanism. We discuss how this multiscale design approach can be used to obtain new compounds with tailored VOC selectivity and spectral responses.

With the aim to develop simple, programmatically generated, topology-based descriptors of crystal structures for application to mechanical properties prediction methods, we have developed a new geometric analysis protocol using the CSD Python API.

[Ni(medpt)(NO₂)(η²-ONO)] displays an equilibrium between the η¹-NO₂and the η¹-ONO linkage isomers between 150–298 K; upon photoactivation at 100 K the percentage of the η¹-ONO isomer increases.

A high pressure single crystal X-ray diffraction and Raman spectroscopy study has revealed a similar mechanism for both thermal and pressure-induced spin crossover in [FeL1₂](ClO₄)₂ (L1 = 2,6-bis{3-methylpyrazol-1-yl}-pyrazine) and the concomitant anion order-disorder transition.

Molecular conformations can influence the structure and properties of crystalline solids. Important solid-state phenomena such as conformational polymorphism arise from the ability of compounds to crystallise in different conformers. A method to readily identify whether or not a crystal conformation is highly adjusted or may correspond to a rare conformer is, thus, very desirable. We present a new way of identifying unusual conformations in molecular crystals from distributions of torsions in the Cambridge Structural Database (CSD). Our method allows for identification of torsion unusualness with regards to conformational adjustment and conformational change. As part of this method, two new parameters derived from CSD distributions are calculated: P_adjust and P_change. These parameters were tested against DFT calculations for the derivation of meaningful CSD probability thresholds which allow for the identification of unusual torsions. The developed method was then used to investigate unusual torsions in molecular crystals. We found that between 10–13% of torsions in the CSD are unusual and that unusual conformational adjustment is significantly more common than unusual conformational change.