Fluorinated non-fluorinated tetrahedral TriTri porous organic cages for H, CO, and CH adsorption.

We present the synthesis of two porous complementary tetrahedral TriTri imine cages, exhibiting Brunauer-Emmett-Teller (BET) surface areas of 591 m g and 753 m g, suitable for the adsorption of H, CO, and CH. Comparisons in terms of crystallinity, thermal stability, porosity, and selectivity highlight the promising properties of fluorinated and non-fluorinated porous organic cages as functional materials.

Fluorinated Squareimines for Molecular Sieving of Aromatic over Aliphatic Compounds.

The development of more energy-efficient separation technologies is essential. Especially the separation of cyclic aliphatic hydrocarbons from their aromatic counterparts remains a significant challenge due to azeotrope formation and similar physical properties, often requiring energy-intensive processes. Herein, we introduce a novel class of electron-deficient macrocycles with a unique rectangular structure to optimise interactions within the pore, enabling the highly selective molecular sieving of aromatic compounds from mixtures.

Accessing a Diverse Set of Functional Red-Light Photoswitches by Selective Copper-Catalyzed Indigo -Arylation.

The ability to correlate the structure of a molecule with its properties is the key to the rational and accelerated design of new functional compounds and materials. Taking photoswitches as an example, the thermal stability of the metastable state is a crucial property that dictates their application in molecular systems. Indigos have recently emerged as an attractive motif for designing photoswitchable molecules due to their red-light addressability, which can be advantageous in biomedical and material applications.

Multifold Post-Modification of Macrocycles and Cages by Isocyanate-Induced Azadefluorination Cyclisation.

We present the multiple post-modification of organic macrocycles and cages, introducing functional groups into two- and three-dimensional supramolecular scaffolds bearing fluorine substituents, which opens up new possibilities in multi-step supramolecular chemistry employing the vast chemical space of readily available isocyanates. The mechanism and scope of the reaction that proceeds after isocyanate addition to the benzylamine motif via an azadefluorination cyclisation (ADFC) were investigated using DFT calculations, and a series of aromatic isocyanates with different electronic properties were tested. The compounds show excellent chemical stability and were fully characterised.

Photoresponsive Supramolecular Cages and Macrocycles.

The utilisation of light to achieve precise manipulation and control over the structure and function of supramolecular assemblies has emerged as a highly promising approach in the development of complex, configurable, or multifunctional systems and nanoscopic machine-like entities. In this minireview, we highlight recent examples of self-assembled and covalently bound cages and macrocycles with a focus on the external and internal functionalisation of a structure with a photoswitchable unit or the embedment of a photoswitch into the framework of a structure. Functionalising the interior or exterior of a supramolecular cage or macrocycle with a photoresponsive group enables control over different properties, such as guest binding or assembly in the solid-state, while the overall shape of the assembly often undergoes no significant change.

Mechanoresponsive Metal-Organic Cage-Crosslinked Polymer Hydrogels.

We report the formation of metal-organic cage-crosslinked polymer hydrogels. To enable crosslinking of the cages and subsequent network formation, we used homodifunctionalized poly(ethylene glycol) (PEG) chains terminally substituted with bipyridines as ligands for the Pd L corners. The encapsulation of guest molecules into supramolecular self-assembled metal-organic cage-crosslinked hydrogels, as well as ultrasound-induced disassembly of the cages with release of their cargo, is presented in addition to their characterization by nuclear magnetic resonance (NMR) techniques, rheology, and comprehensive small-angle X-ray scattering (SAXS) experiments.

Photoresponsive Dissipative Macrocycles Using Visible-Light-Switchable Azobenzenes.

Visible light can be used to shift dynamic covalent imine assemblies out of equilibrium. We studied a fluorinated azobenzene building block that reliably undergoes geometric isomerism upon irradiation. The building block was used in combination with two different amines, ethylenediamine and R,R-1,2-diaminocyclohexane, to create a library of imine macrocycles.

Synthesis and Characterization of a Crystalline Imine-Based Covalent Organic Framework with Triazine Node and Biphenyl Linker and Its Fluorinated Derivate for CO/CH Separation.

A catalyst-free Schiff base reaction was applied to synthesize two imine-linked covalent organic frameworks (COFs). The condensation reaction of 1,3,5-tris-(4-aminophenyl)triazine (TAPT) with 4,4'-biphenyldicarboxaldehyde led to the structure of HHU-COF-1 (HHU = Heinrich-Heine University). The fluorinated analog HHU-COF-2 was obtained with 2,2',3,3',5,5',6,6'-octafluoro-4,4'-biphenyldicarboxaldehyde.

Supramolecular networks by imine halogen bonding.

Halogen bonding of neutral donors using imine groups of porous organic cage compounds as acceptors leads to the formation of halogen-bonded frameworks. We report the use of two different imine cages, in combination with three electron-poor halogen bond donors. Four resulting solid-state structures elucidated by single-crystal X-ray analysis are presented and analysed for the first time by plane-wave DFT calculations and QTAIM-analyses of the entire unit cells, demonstrating the formation of halogen bonds within the networks.

Fast, solvent-free synthesis of ferrocene-containing organic cages dynamic covalent chemistry in the solid state.

A simple, solvent-free synthetic protocol towards the synthesis of organic self-assembled macromolecules has been established. By employing mechanochemistry using glassware readily available to every organic chemist, we were able to synthesise three novel organic cage compounds exemplarily and to speed up the synthesis of a ferrocene-containing macrocycle by a factor of 288 compared to the solution-based synthesis. The structural investigation of the newly synthesised cages revealed different modes of connectivity from using ferrocene-containing aldehydes caused by the free rotation of the cyclopentadienyl units against each other.

Release of Molecular Cargo from Polymer Systems by Mechanochemistry.

The design and manipulation of (multi)functional materials at the nanoscale holds the promise of fuelling tomorrow's major technological advances. In the realm of macromolecular nanosystems, the incorporation of force-responsive groups, so called mechanophores, has resulted in unprecedented access to responsive behaviours and enabled sophisticated functions of the resulting structures and advanced materials. Among the diverse force-activated motifs, the on-demand release or activation of compounds, such as catalysts, drugs, or monomers for self-healing, are sought-after since they enable triggering pristine small molecule function from macromolecular frameworks.

Supramolecular Alloys from Fluorinated Hybrid Tri Di Imine Cages.

To create innovative materials, efficient control and engineering of pore sizes and their characteristics, crystallinity and stability is required. Eight hybrid Tri Di imine cages with a tunable degree of fluorination and one fully fluorinated Tri Di imine cage are investigated. Although the fluorinated and the non-fluorinated building blocks used herein differ vastly in reactivity, it was possible to gain control over the outcome of the self-assembly process, by carefully controlling the feed ratio.

Mechanochemical Release of Non-Covalently Bound Guests from a Polymer-Decorated Supramolecular Cage.

Supramolecular coordination cages show a wide range of useful properties including, but not limited to, complex molecular machine-like operations, confined space catalysis, and rich host-guest chemistries. Here we report the uptake and release of non-covalently encapsulated, pharmaceutically-active cargo from an octahedral Pd cage bearing polymer chains on each vertex. Six poly(ethylene glycol)-decorated bipyridine ligands are used to assemble an octahedral Pd (TPT) cage.

A porous fluorinated organic [4+4] imine cage showing CO and H adsorption.

We present the synthesis of a porous, organic [4+4] imine cage containing perfluorinated aromatic panels. Gas adsorption experiments show an uptake of 19.0 wt% CO2 (4.

Fluorinated azobenzenes as supramolecular halogen-bonding building blocks.

-Fluoroazobenzenes are a remarkable example of bistable photoswitches, addressable by visible light. Symmetrical, highly fluorinated azobenzenes bearing an iodine substituent in -position were shown to be suitable supramolecular building blocks both in solution and in the solid state in combination with neutral halogen bonding acceptors, such as lutidines. Therefore, we investigate the photochemistry of a series of azobenzene photoswitches.

[2+2] Halogen-bonded boxes employing azobenzenes.

Herein, we report the synthesis and crystal structures of three [2+2] supramolecular boxes assembled by halogen bonding. The discrete, two-dimensional boxes with a length of 25-30 Å are based on rigid u-shaped halogen acceptors paired with highly fluorinated, azobenzenes bearing halogen bond donors.

Optically switchable organic light-emitting transistors.

Organic light-emitting transistors are pivotal components for emerging opto- and nanoelectronics applications, such as logic circuitries and smart displays. Within this technology sector, the integration of multiple functionalities in a single electronic device remains the key challenge. Here we show optically switchable organic light-emitting transistors fabricated through a judicious combination of light-emitting semiconductors and photochromic molecules.

Microcrystal Electron Diffraction (MicroED) for Small-Molecule Structure Determination.

The development of new methods to analyze and determine molecular structures parallels the ability to accelerate synthetic research. For many decades, single-crystal analysis by X-ray diffraction (SXRD) has been the definitive tool for structural analysis at the atomic level; the drawback, however, is that a suitable single crystal of the analyte needs to be grown. The recent innovation of the crystalline sponge (CS) method allows the microanalysis of compounds simply soaked in a readily prepared CS crystal, thus circumventing the need to screen crystallization conditions while also using only a trace amount of the sample.

Efficient Light-Induced pK Modulation Coupled to Base-Catalyzed Photochromism.

Photoswitchable acid-base pairs, whose pK values can be reversibly altered, are attractive molecular tools to control chemical and biological processes with light. A significant, light-induced pK change of three units in aqueous medium has been realized for two thermally stable states, which can be interconverted using UV and green light. The light-induced pK modulation is based on incorporating a 3-H-thiazol-2-one moiety into the framework of a diarylethene photoswitch, which loses the heteroaromatic stabilization of the negatively charged conjugate base upon photochemical ring closure, and hence becomes significantly less acidic.

Click Chemistry Derived Pyridazines: Electron-Deficient Building Blocks with Defined Conformation and Packing Structure.

A series of 3,6-bis(4-triazolyl)pyridazines equipped with terminal phenyl substituents with varying degree of fluorination were synthesized by using the facile copper-catalyzed azide-alkyne cycloaddition and their structures were thoroughly investigated in the gas phase, in solution, and in the solid state by employing DFT calculations, NMR spectroscopy, and single-crystal X-ray diffraction, respectively. On the molecular level, their structure is governed by the strong preference of the triazole-pyridazine linkages for the anti-conformation. The supramolecular organization of the molecules in the crystalline solid is controlled by π-stacking, C-H⋅⋅⋅π as well as C-F⋅⋅⋅H interactions.

N,N'-Disubstituted Indigos as Readily Available Red-Light Photoswitches with Tunable Thermal Half-Lives.

Some rare indigo derivatives have been known for a long time to be photochromic upon irradiation with red light, which should be advantageous for many applications. However, the absence of strategies to tune their thermal half-lives by modular molecular design as well as the lack of proper synthetic methods to prepare a variety of such molecules from the parent indigo dye have so far precluded their use. In this work, several synthetic protocols for N-functionalization have been developed, and a variety of N-alkyl and N-aryl indigo derivatives have been prepared.

Compressed Corannulene in a Molecular Cage.

Self-assembled coordination cages can be employed as a molecular press, where the bowl-shaped guest corannulene (C20H10) is significantly flattened upon inclusion within the hydrophobic cavity. This is demonstrated by the pairwise inclusion of corannulene with naphthalene diimide as well as by the dimer inclusion of bromocorannulene inside the box-like host. The compressed corannulene structures are unambiguously revealed by single-crystal X-ray analysis.

Improving the fatigue resistance of diarylethene switches.

When applying photochromic switches as functional units in light-responsive materials or devices, an often disregarded yet crucial property is their resistance to fatigue during photoisomerization. In the large family of diarylethene photoswitches, formation of an annulated isomer as a byproduct of the photochromic reaction turns out to prevent the desired high reversibility for many different derivatives. To overcome this general problem, we have synthesized and thoroughly investigated the fatigue behavior of a series of diarylethenes, varying the nature of the hetaryl moieties, the bridging units, and the substituents.

Fluorinated and trifluoromethylated corannulenes.

The syntheses and properties of corannulenes carrying electron-withdrawing groups (F, CF3 , C6 F5 ) are reported. Direct fluorination of corannulene (C20 H10 ) was carried out with xenon difluoride, and the crystal structure of the product was confirmed by the X-ray analysis. Novel trifluoromethylated corannulenes, including the versatile 4,9-dibromo-1,2-bis(trifluoromethyl)corannulene, were obtained by various established ring-closing reactions.

Sumanenylferrocenes and their solid state self-assembly.

The first ferrocene-fused organometallic compounds derived from the buckybowl sumanene (C21H12) are presented. Both compounds, sumanenylferrocene and 1,1'-disumanenylferrocene, have been synthesized by Negishi-type cross-coupling of iodosumanene and were studied crystallographically. Sumanenylferrocenes form unique packing motifs, which are both different from those of their corannulene congeners and sumanene itself.