Themed collection Introducing the CrystEngComm Advisory Board and their research

This overview, summarizing recent progresses in the fabrication of multi-functional oxide nanomaterials for sustainable and environmental end-uses, sheds light on the interplay between their chemico-physical features and functional properties.

The importance of Se⋯N chalcogen-bonding in supramolecular assembly is demonstrated.

Fused azolate ligands are hydrolytically-stable linkers for metal–organic frameworks. Their unique geometries and capacity for functionalisation have opened new pathways at the convergence of simple N-heterocycles and biologically relevant purines.

Nanoscale compositionally graded crystals have huge potential to allow the exploration of new functionalities through crystal lattice modulation.

Nanocrystal engineering has evolved into a dynamic research area over the past few decades but is not properly defined. Here, we present select examples to highlight the diverse aspects of crystal engineering applied on inorganic nanomaterials.

A newly developed methodology allows for the determination of the mechanisms of deformation in flexible crystals with atomic precision. With broader applications, mapping experiments have wide reaching potential within the field of materials science.

Crystal adaptronics has undergone tremendous developments that have been utilized to rationalize dynamics in crystals. This highlight discusses about the role of intermolecular interactions in rationalizing mechanical responses in crystals.

This highlight focuses on the recent development of oxazoline-based discrete coordination complexes and coordination polymers.

Dyads formed by tetrathiafulvalene (TTF) linked to perchlorotriphenylmethyl (PTM) radicals exhibit interesting physical properties such as bistability in solution or conductivity in solid state.

The mechanochemical experiments on leflunomide result in the formation of solvate with DMSO and salt with piperazine via conversion to the Z-form of teriflunomide. These solid-state forms were characterized by diffraction and thermal techniques.

The CVD–VLS process for 4H-SiC films with a Pt–Si alloy flux achieved their low carrier densities of ∼10¹⁵ cm⁻³, demonstrating a remarkable etch back effect and a possible conversion of TEDs and TSDs in the substrate to BPDs in the films.

The torsional flexibility of imines affects solid-state packing and properties. Behaviors including colossal thermal expansion, pedal motion, and phase transitions in imine-containing solids are described.

The second and third crystalline forms of lactic acid are described, yet along with the known structure, they together fail to reproduce any of the supramolecular aggregates that have long been observed in isotropic media.

Reversible and facile single-crystal-to-single-crystal transformation between two polymorphs of diphenhydramine citrate leads to molecular level understanding of crystal phase change.

Hydrogen bonds (i.e., N⁺–H⋯N) in combination with cation⋯π interactions enable a cascade-like [2 + 2] photodimerization of 4-stilbazole in a salt cocrystal.

There are many active pharmaceutical ingredients that lack N–H, O–H and S–H hydrogen-bond donor functional groups.

An automated application, CoForm, was used for predicting the outcomes of attempted co-crystallizations between two active pharmaceutical ingredients, loratadine and desloratadine, and 41 potential co-formers from the general interest (OGI) list.

A supramolecular ladder sustained by halogen bonds with rungs based upon a photoproduct, namely rctt-tetrakis(5′-pyrimidyl)cylcobutane, generated in the solid state is reported.

A novel 3D luminescent MOF has been developed by the incorporation of an organic chromophore, demonstrating the photoluminescence of MOFs can be greatly enhanced by increasing their structural dimensionality.

Supramolecular repurposing of the anti-HIV drug emtricitabine enables the recognition of rod-shaped bipyridines as a hydrogen-bonded supramolecular cleft.

Intrinsically porous molecular building blocks are used for the rational design and construction of molecular-level controlled porous materials.

A new parameter is proposed to quantify the linearity of halogen bonds.

An analysis of compiled literature nanoindentation contact hardness (H_c) and elastic modulus (E) values of molecular crystals revealed a wide range of mechanical properties (0.001–1.80 GPa for H_c and 0.27–46.8 GPa for E).

Crystalline and amorphous stable binary compounds of indapamide for high solubility and permeability.

Nano-dimensional crystals of aspirin generated through sonochemistry exhibit Young's modulus values an order of magnitude softer than macro-dimensional crystals.

Co-crystals assembled via halogen or hydrogen bonds yield minimal thermal expansion along 1D chains and greater expansion in 2D sheets.

Nucleation of acetaminophen glass at room temperature originates from ∼50 μm below the surface.

Three baicalein (BAI) cocrystals with nicotinamide (NCT), caffeine (CAF), and isoniazid (ISN) exhibited excellent tabletability despite the markedly different tabletability of the coformers.

Anomalous thermal expansion of a new diyn-diol molecule was studied by means of variable-temperature single-crystal X-ray diffraction. Analysis of the unit cell axes as a function of temperature shows that the material experiences uniaxial negative thermal expansion. Packing analysis of the crystal structures reveals twisting of the cyclopentyl moiety relative to the diyne spine with increasing temperature.

Six different crystal structures are obtained depending on the crystallization solvent.

Isostructural and almost isometric crystals that differ in their colour may be welded in solution and under mild conditions into crystalline materials with imposed sequences.

Co-crystal screening data and machine learning models allows prediction of the most likely co-formers to use for new molecules.

Similarly organized carbamazepine clusters in a soluble cocrystal with glutaric acid templated the nucleation of carbamazepine dihydrate during dissolution.

A 3D-coordination polymer was shown to trap one-dimensional polyhedral water cages consisting of repeat units of (H₂O)₂₄, the geometry of which resembles the exotic organic molecule pagodane.

The attractive nature of type II C–F⋯F–C interaction has been established using experimental and theoretical modelling of electron densities using multipole modelling of high-resolution X-ray diffraction data and theoretical structure factors.

A series of three solvates [Fe(naphPren)₂]I·CH₂Cl₂1, [Fe(naphPren)₂]I·CHCl₃2 and [Fe(naphPren)₂]I·acetone 3 showing thermal and light-induced spin crossover is reported.

In the Cu(II) oxalate salts of (C₅H₇N₂O)₂[Cu(C₂O₄)₂] 1 and C₁₃H₁₆N₂[Cu(C₂O₄)₂] 2, the oxalate adopts different coordination modes: the common bidentate chelating oxalate in 1 and the relatively scarce μ-oxalato-κ³O¹,O²:O¹′ in 2.

Cation-modified and robust zirconium-based metal–organic frameworks demonstrate enhanced performance for carbon dioxide capture.

Cocrystallization improves the solubility and permeability of BCS class IV anticancer drug ribociclib as a cocrystal with resorcinol and as a salt hydrate with vanillic acid.

This manuscript reports a CSD survey of X-ray structures exhibiting halogen bonds involving metals of group 10 as electron donors. The DFT study on several model systems discloses that the interactions are moderately strong.

The hexagonal motifs dictated by the {Cu₃} pyrazolate triangular units are joined together by the additional connectivity of the various alternating zinc (oxo)carboxylate units to form 2D/3D open structures (* relates the same example-structure).

Three Zn(II) supramolecular assemblies are fabricated with a D–π–A ligand and present good fluorescent sensing properties for specific organic molecules.

The impact of macrocycles on calcium oxalate formation. Calcium oxalate is a major component of kidney stones, an ailment that affects many people globally.

Two novel polymorphs of a cocrystal involving phloretin and nicotinamide were identified and found where the polymorphs show distinct crystal structures, photoluminescence, and dissolution rates.

The formation of three types of supramolecular coordination cages is described. Tetrasulfonylcalixarene, combined with metallic salts (Ni, Co and Zn) and the flexible succinate ligand, led to cages. H bonded induced chirality was observed for both isomorphous cages.

The first of a new class of spiroalkane-derived MOF linkers shows aromaticity is not a prerequisite for ligand design in porous materials.

Racemic crystals of Cu/Zn(II)-tetradentate Schiff base ligands with Λ/Δ-chirality induction at-metal center.

Eight cocrystal-salts of the multi-kinase drug pazopanib with hydroxybenzoic acids are sustained by the strong, ionic aminopyridinium⋯carboxylate heterosynthon of N–H⋯O hydrogen bonds between the carboxylic acid donor and amino-pyrimidine acceptor.

The ability to selectively tune the optical and the mechanical properties of organic molecular crystals offers a promising approach towards developing flexible optical devices.

Photomechanical responses of the single crystals of a series of sulfonylhydrazones are explored for the first time.

The impact of the halogen substituent on supramolecular preferences that influence packing is explored in a series of heteroleptic iron(III) complexes.

Eutectic, co-amorphous, cocrystal, and physical mixtures of curcumin with basic amino acids are prepared and characterized by PXRD, DSC, NMR, FT-IR, and SEM; solubility and dissolution improvement achieved in 40% ethanol–water system.

The dielectric constant impacts on oriented attachment as well as solubility and morphology.

Secondary non-covalent interactions prove crucial in determining the topology of supramolecular chains sustained by conventional O–H⋯O hydrogen bonding.

Ionic liquids – ionic crystals – ionic liquid crystals? Structural order in imidazolium-based ILs, a series of asymmetrical 1-dodecyl-2-methyl-3-alkylimidazolium bromides, [C₁₂C₁C_nim][Br] with n = 0–12.

We employ our pulsed laser deposition system with rapid beam deflection to demonstrate the heteroepitaxial growth of 3C–SiC thin films by a vapour–liquid–solid-like mechanism by alternating deposition of SiC and NiSi₂ flux in nanoscale.

Data informatics methods applied to the Cambridge Structural Database reveal shifting trends in solvate formation and inherent biases in the symmetry and packing fraction of solvates and their solvent-free analogues.

Analysis of piracetam polytypes using energy-vector models, thermal expansion and nanoindentation measurements, produces a plausible link between their crystal structures and tableting behaviour.

Crystallisation at pressure overcomes the effect of isotopic polymorphism in the methylpyridine pentachlorophenol co-crystal. Though the hydrogenated Cc polymorph can only be obtained at pressure, it is stable on recovery to ambient conditions.

A survey of delocalised C–I⋯π(chelate ring) interactions is presented.

Cocrystallization is a rational selection crystal engineering approach for the development of novel solid forms with enhanced physicochemical and mechanical properties.

Stabilising C–Cl(lone-pair)⋯π(chelate ring) interactions are described.

Co-sublimation of two neutral components yields crystals of salts and co-crystals. Experiments show that during sublimation of salts, proton transfer occurs after molecules enter the gas phase.

Three zinc-based coordination complexes were selectively generated in the crystalline phase using a new flexible molecular “tweezers” calix[4]arene derivative ligand decorated with two appended carboxylic moieties and benzyl spacers ((3-4H)).

A combined CSD and experimental study shows that the ring stacking and laddering principle, an ionic model, gives insight into the crystal structures of secondary ammonium carboxylate salts.

C–H⋯π(chelate ring) interactions play an important role in assembling first-row transition metal dithiocarbamates in their crystals.

CSD data mining and energy calculations show that coformer self-interactions might significantly contribute to the packing energy stabilization of cocrystals.

A search method based on SMILES string matching was developed to identify hydrate–anhydrate structure pairs in the Cambridge Structure Database.

The value of a hydrogen bond network prediction model was improved using a tool to increase prediction trust. Its accuracy could be improved up to 73% or 89% with the compromise that only 34% and 8% of the test examples could be predicted.

The influence of reducing agents on the mechanochemical synthesis of Au nanoparticles differ significantly from analogous solution syntheses. Environmentally benign mechanochemical syntheses of metal nanoparticles therefore require dedicated studies.