Enhancing the Chemical Stability of P12L24 Cage: Transformation of the Chemically Labile Imine Cage into a Robust Carbamate Cage

Herein, we report enhancement in chemical stability of the imine-based porphyrinic cage P12L24 by converting it into a robust carbamate porphyrinic cage, c-P12L24, through a two-step post-synthetic modification process. First, the imine bonds in P12L24 were reduced to form an amine-based cage, r-P12L24, followed by carbamation using N,N'-carbonyldiimidazole (CDI) to yield c-P12L24. The resulting carbamate cage exhibits high stability under acidic and basic conditions (pH 1-13) and in the presence of moisture. 1H NMR, DOSY NMR, and DFT calculations revealed that reducing the imine bonds to amine increases the framework's flexibility, causing partial structural collapse, whereas the carbamate formation restores structural rigidity. The insertion of a 4.0 nm molecular ruler into the cavity of zinc-metallated c-P12L24 via metal-ligand coordination further confirmed restoration of the cavity size and geometry of the original cage. This enhancement of chemical stability through carbamate formation can pave the way to a wide range of potential applications for the gigantic porphyrinic cage.

Pt(II)/Pd(II)-Based Metallosupramolecular Architectures as Light Harvesting Systems and their Applications

The development of artificial light-harvesting systems mimicking the natural photosynthesis method is an ever-growing field of research. Numerous systems such as polymers, metal complexes, POFs, COFs, supramolecular frameworks etc. have been fabricated to accomplish more efficient energy transfer and storage. Among them, the supramolecular coordination complexes (SCCs) formed by non-covalent metal-ligand interaction, have shown the capacity to not only undergo single and multistep energy migration but also to utilize the harvested energy for a wide variety of applications such as photocatalysis, tunable emissive systems, encrypted anti-counterfeiting materials, white light emitters etc. This review sheds light on the light-harvesting behavior of both the 2D metallacycles and 3D metallacages where design ingenuity has been executed to afford energy harvesting by both donor ligands as well as metal acceptors.

A Chiral [2+3] Covalent Organic Cage Based on 1,1'-Bi-2-naphthol (BINOL) Units

A [2+3] chiral covalent organic cage is produced through a dynamic covalent chemistry approach by mixing two readily available building units, viz. an enantiopure 3,3'-diformyl 2,2'-BINOL compound (A) with a triamino spacer (B). The two enantiomeric (R,R,R) and (S,S,S) forms of the cage C are formed nearly quantitatively thanks to the reversibility of the imine linkage. The X-ray diffraction analysis of cage (S,S,S)-C highlights that the six OH functions of the BINOL fragments are positioned inside the cage cavity. Upon reduction of the imine bonds of cage C, the amine cage D is obtained. The ability of the cage D to host the 1-phenylethylammonium cation (EH+) as a guest is evaluated through UV, CD and DOSY NMR studies. A higher binding constant for (R)-EH+ cation (Ka=1.7 106±10 % M-1) related to (S)-EH+ (Ka=0.9 106±10 % M-1) is determined in the presence of the (R,R,R)-D cage. This enantiopreference is in close agreement with molecular dynamics simulation.

Single Crystals of Insoluble Porous Salicylimine Cages

Porous organic cages (POCs) are meanwhile an established class of porous materials. Most of them are soluble to a certain extend and thus processable in or from solution. However, a few of larger salicylimine cages were reported to be insoluble in any organic solvents and thus characterized as amorphous materials. These cages were now synthesized as single-crystalline materials to get insight into packing motifs and preferred intermolecular interactions. Furthermore, the pairs of crystalline and amorphous materials for each cage allowed to compare their gas-sorption properties in both morphological states.

Dynamic covalent self-assembly and self-sorting processes in the formation of imine-based macrocycles and macrobicyclic cages

Investigating the self-assembly and self-sorting behaviour of dynamic covalent organic architectures makes possible the parallel generation of multiple discrete products in a single one pot procedure. We here report the self-assembly of covalent organic macrocycles and macrobicyclic cages from dialdehyde and polyamine components via multiple [2 + 2] and [3 + 2] polyimine condensations. Furthermore, component self-sorting processes have been monitored within the dynamic covalent libraries formed by these macrocycles and macrobicyclic cages. The progressive assembly of the final structures involves intermediates which undergo component selection and self-correction to generate the final thermodynamic constituents. The homo-self-sorting observed seems to involve entropic factors, as the homoleptic species present a higher symmetry than the competing heteroleptic ones. This study not only emphasizes the importance of an adequate design of the components of complex self-sorting systems, but also verifies the conjecture that systems of higher complexity may generate simpler outputs through the operation of competitive self-sorting.

Porous Organic Cages

Porous organic cages (POCs) are a relatively new class of low-density crystalline materials that have emerged as a versatile platform for investigating molecular recognition, gas storage and separation, and proton conduction, with potential applications in the fields of porous liquids, highly permeable membranes, heterogeneous catalysis, and microreactors. In common with highly extended porous structures, such as metal-organic frameworks (MOFs), covalent organic frameworks (COFs), and porous organic polymers (POPs), POCs possess all of the advantages of highly specific surface areas, porosities, open pore channels, and tunable structures. In addition, they have discrete molecular structures and exhibit good to excellent solubilities in common solvents, enabling their solution dispersibility and processability─properties that are not readily available in the case of the well-established, insoluble, extended porous frameworks. Here, we present a critical review summarizing in detail recent progress and breakthroughs─especially during the past five years─of all the POCs while taking a close look at their strategic design, precise synthesis, including both irreversible bond-forming chemistry and dynamic covalent chemistry, advanced characterization, and diverse applications. We highlight representative POC examples in an attempt to gain some understanding of their structure-function relationships. We also discuss future challenges and opportunities in the design, synthesis, characterization, and application of POCs. We anticipate that this review will be useful to researchers working in this field when it comes to designing and developing new POCs with desired functions.

[2+3] Amide Cages by Oxidation of [2+3] Imine Cages – Revisiting Molecular Hosts for Highly Efficient Nitrate Binding

The pollution of groundwater with nitrate is a serious issue because nitrate can cause several diseases such as methemoglobinemia or cancer. Therefore, selective removal of nitrate by efficient binding to supramolecular hosts is highly desired. Here we describe how to make [2+3] amide cages in very high to quantitative yields by applying an optimized Pinnick oxidation protocol for the conversion of corresponding imine cages. By NMR titration experiments of the eight different [2+3] amide cages with nitrate, chloride and hydrogen sulfate we identified one cage with an unprecedented high selectivity towards nitrate binding vs. chloride (S=705) or hydrogensulfate (S>13500) in CD₂Cl₂/CD₃CN (1 : 3). NMR experiments as well as single‐crystal structure comparison of host‐guest complexes give insight into structure‐property‐relationships.

Purely Covalent Molecular Cages and Containers for Guest Encapsulation

Cage compounds offer unique binding pockets similar to enzyme-binding sites, which can be customized in terms of size, shape, and functional groups to point toward the cavity and many other parameters. Different synthetic strategies have been developed to create a toolkit of methods that allow preparing tailor-made organic cages for a number of distinct applications, such as gas separation, molecular recognition, molecular encapsulation, hosts for catalysis, etc. These examples show the versatility and high selectivity that can be achieved using cages, which is impossible by employing other molecular systems. This review explores the progress made in the field of fully organic molecular cages and containers by focusing on the properties of the cavity and their application to encapsulate guests.

Repurposing of substances with lactone moiety for the treatment of γ-Hydroxybutyric acid and γ-Butyrolactone intoxication through modulating paraoxonase and PPARγ

GHB and GBL are highly accessible recreational drugs of abuse with a high risk of adverse effects and mortality while no specific antidotes exist. These components can also be found in the clinical setting, beverages, and cosmetic products, leading to unwanted exposures and further intoxications. As the structural analogue of GABA, GHB is suggested as the primary mediator of GHB/GBL effects. We further suggest that GBL might be as critical as GHB in this process, acting through PPARγ as its receptor. Moreover, PPARγ and PON (i.e., the GHB-GBL converting enzyme) can be targeted for GHB/GBL addiction and intoxication, leading to modulation of the GHB-GBL balance and blockage of their effects. We suggest that repurposing substances with lactone moiety such as bacterial lactones, sesquiterpene lactones, and statins might lead to potential therapeutic options as they occupy the active sites of PPARγ and PON and interfere with the GHB-GBL balance. In conclusion, this hypothesis improves the GHB/GBL mechanism of action, suggests potential therapeutic options, and highlights the necessity of classifying GBL as a controlled substance.

Triptycene Derivatives: From Their Synthesis to Their Unique Properties

Since the first preparation of triptycene, great progress has been made with respect to its synthesis and the understanding of its properties. Interest in triptycene-based systems is intense; in recent years, advances in the synthetic methodology and properties of new triptycenes have been reported by researchers from various fields of science. Here, an account of these new developments is given and placed in reference to earlier pivotal works that underpin the field. First, we discuss new approaches to the synthesis of new triptycenes. Progress in the regioselective synthesis of sterically demanding systems is discussed. The application of triptycenes in catalysis is also presented. Next, progress in the understanding of the relations between triptycene structures and their properties is discussed. The unique properties of triptycenes in the liquid and solid states are elaborated. Unique interactions, which involve triptycene molecular scaffolds, are presented. Molecular interactions within a triptycene unit, as well as between triptycenes or triptycenes and other molecules, are also evaluated. In particular, the summary of the synthesis and useful features will be helpful to researchers who are using triptycenes as building blocks in the chemical and materials sciences.

Recent advances on triptycene derivatives in supramolecular and materials chemistry

Triptycene derivatives, a type of specific aromatic compound, have been attracting much attention in many research areas. Over the past several years, triptycene and its derivatives have been described to be useful and efficient building blocks for the design and synthesis of novel supramolecular acceptors, porous materials and luminescent materials with specific structures and properties. In this review, recent researches on triptycene derivatives in supramolecular and materials chemistry are summarized. Especially, the construction of a new type of macrocyclic arenes and organic cages with triptycene and its derivatives as building blocks are focused on, and their applications in molecular recognition, self-assembly and gas selective sorption are highlighted. Moreover, the applications of triptycene and its derivatives in porous organic materials and thermally activated delayed fluorescence (TADF) materials are also discussed.

Isoreticular Crystallization of Highly Porous Cubic Covalent Organic Cage Compounds*

Modular frameworks featuring well-defined pore structures in microscale domains establish tailor-made porous materials. For open molecular solids however, maintaining long-range order after desolvation is inherently challenging, since packing is usually governed by only a few supramolecular interactions. Here we report on two series of nanocubes obtained by co-condensation of two different hexahydroxy tribenzotriquinacenes (TBTQs) and benzene-1,4-diboronic acids (BDBAs) with varying linear alkyl chains in 2,5-position. n-Butyl groups at the apical position of the TBTQ vertices yielded soluble model compounds, which were analyzed by mass spectrometry and NMR spectroscopy. In contrast, methyl-substituted cages spontaneously crystallized as isostructural and highly porous solids with BET surface areas and pore volumes of up to 3426 m2  g-1 and 1.84 cm3  g-1 . Single crystal X-ray diffraction and sorption measurements revealed an intricate cubic arrangement of alternating micro- and mesopores in the range of 0.97-2.2 nm that are fine-tuned by the alkyl substituents at the BDBA linker.

Soluble Congeners of Prior Insoluble Shape-Persistent Imine Cages

One of the most applied reaction types to synthesize shape‐persistent organic cage compounds is the imine condensation reaction and it is assumed that the formed cages are thermodynamically controlled products due to the reversibility of the imine condensation. However, most of the synthesized imine cages reported are formed as precipitate from the reaction mixture and therefore rather may be kinetically controlled products. There are even examples in literature, where resulting cages are not soluble at all in common organic solvents to characterize or study their formation by NMR spectroscopy in solution. Here, a triptycene triamine containing three solubilizing n‐hexyloxy chains has been used to synthesize soluble congeners of prior insoluble cages. This allowed us to study the formation as well as the reversibility of cage formation in solution by investigating exchange of building blocks between the cages and deuterated derivatives thereof.

Endohedral Hydrogen Bonding Templates the Formation of a Highly Strained Covalent Organic Cage Compound*

A highly strained covalent organic cage compound was synthesized from hexahydroxy tribenzotriquinacene (TBTQ) and a meta-terphenyl-based diboronic acid with an additional benzoic acid substituent in 2'-position. Usually, a 120° bite angle in the unsubstituted ditopic linker favors the formation of a [4+6] cage assembly. Here, the introduction of the benzoic acid group is shown to lead to a perfectly preorganized circular hydrogen-bonding array in the cavity of a trigonal-bipyramidal [2+3] cage, which energetically overcompensates the additional strain energy caused by the larger mismatch in bite angles for the smaller assembly. The strained cage compound was analyzed by mass spectrometry and 1 H, 13 C and DOSY NMR spectroscopy. DFT calculations revealed the energetic contribution of the hydrogen-bonding template to the cage stability. Furthermore, molecular dynamics simulations on early intermediates indicate an additional kinetic effect, as hydrogen bonding also preorganizes and rigidifies small oligomers to facilitate the exclusive formation of smaller and more strained macrocycles and cages.

The Ionic Organic Cage: An Effective and Recyclable Testbed for Catalytic CO2 Transformation

Porous organic cages (POC) are a class of relatively new molecular porous materials, whose concept was raised in 2009 by Cooper’s group and has rarely been directly used in the area of organic catalysis. In this contribution, a novel ionic quasi-porous organic cage (denoted as Iq-POC), a quaternary phosphonium salt, was easily synthesized through dynamic covalent chemistry and a subsequent nucleophilic addition reaction. Iq-POC was applied as an effective nucleophilic catalyst for the cycloaddition reaction of CO2 and epoxides. Owing to the combined effect of the relatively large molecular weight (compared with PPh3+I−) and the strong polarity of Iq-POC, the molecular catalyst Iq-POC displayed favorable heterogeneous nature (i.e., insolubility) in this catalytic system. Therefore, the Iq-POC catalyst could be easily separated and recycled by simple centrifugation method, and the catalyst could be reused five times without obvious loss of activity. The molecular weight augmentation route in this study (from PPh3+I− to Iq-POC) provided us a “cage strategy” of designing separable and recyclable molecular catalysts.

A Robust Porous Quinoline Cage: Transformation of a [4+6] Salicylimine Cage by Povarov Cyclization

Porous shape-persistent organic cages have become the object of interest in recent years because they are soluble and thus processable from solution. A variety of cages can be achieved by applying dynamic covalent chemistry (DCC), but they are less chemically stable. Here the transformation of a salicylimine cage into a quinoline cage by a twelve-fold Povarov reaction as the key step is described. Besides the chemical stability of the cage over a broad pH regime, it shows a unique absorption and emission depending on acid concentration. Furthermore, thin films for the vapor detection of acids were investigated, showing color switches from pale-yellow to red, and characteristic emission profiles.

Microporous Triptycene-Based Affinity Materials on Quartz Crystal Microbalances for Tracing of Illicit Compounds

Triptycene-based organic molecules of intrinsic microporosity (OMIMs) with extended functionalized π-surfaces are excellent materials for gas sorption and separation. In this study, the affinities of triptycene-based OMIM affinity materials on 195 MHz high-fundamental-frequency quartz crystal microbalances (HFF-QCMs) for hazardous and illicit compounds such as piperonal and (-)-norephedrine were determined. Both new and existing porous triptycene-based affinity materials were investigated, resulting in very high sensitivities and selectivities that could be applied for sensing purposes. Remarkable results were found for safrole - a starting material for illicit compounds such as ecstasy. A systematic approach highlights the effects of different size of π-surfaces of these affinity materials, allowing a classification of the properties that might be optimal for the design of future OMIM-based affinity materials.

Organic Imine Cages: Molecular Marriage and Applications

Imine condensation has been known to chemists for more than a century and is used extensively to synthesize large organic cages of defined shapes and sizes. Surprisingly, in the context of the synthetic methods for organic imine cages (OICs), a self-sorting/self-selection (molecular marriage) process has been overlooked over the years. Such processes are omnipresent in nature, from the creation of galaxies to the formation of the smallest building blocks of life (the cell). Such processes have the incredible ability to guide a system toward the formation of a specific product or products out of a collection of equally probable multiple possibilities. This Minireview sheds light on new opportunities in cage design offered by the self-sorting/self-selection protocol in OICs. Recent efforts to explore organic cages for various exciting new applications are discussed; for example, for detection of harmful small organic molecules, as templates for nucleation of metal nanoparticles (MNPs), and as proton-conducting materials.

Shape-persistent pyrrole-based covalent organic cages: synthesis, structure and selective gas adsorption properties

Two cryptand-like, shape persistent [2+3] imine cages (1 and 2) derived from oligopyrrolic precursors (diformyl dipyrrylpyridine 3 and diformyl bipyrrole 4) were prepared. These cages contain open cavities as inferred from solid state structural analyses and act as selective CO2 gas adsorbing materials in the solid state.

Eigencages: Learning a Latent Space of Porous Cage Molecules

Porous organic cage molecules harbor nanosized cavities that can selectively adsorb gas molecules, lending them applications in separations and sensing. The geometry of the cavity strongly influences their adsorptive selectivity. For comparing cages and predicting their adsorption properties, we embed/encode a set of 74 porous organic cage molecules into a low-dimensional, latent "cage space" on the basis of their intrinsic porosity. We first computationally scan each cage to generate a three-dimensional (3D) image of its porosity. Leveraging the singular value decomposition, in an unsupervised manner, we then learn across all cages an approximate, lower-dimensional subspace in which the 3D porosity images congregate. The "eigencages" are the set of orthogonal, characteristic 3D porosity images that span this lower-dimensional subspace, ordered in terms of importance. A latent representation/encoding of each cage follows by approximately expressing it as a combination of the eigencages. We show that the learned encoding captures salient features of the cavities of porous cages and is predictive of properties of the cages that arise from cavity shape. Our methods could be applied to learn latent representations of cavities within other classes of porous materials and of shapes of molecules in general.

Computationally-inspired discovery of an unsymmetrical porous organic cage

A completely unsymmetrical porous organic cage was synthesised from a C_2v symmetrical building block that was identified by a computational screen. The cage was formed through a 12-fold imine condensation of a tritopic C_2v symmetric trialdehyde with a ditopic C₂ symmetric diamine in a [4 + 6] reaction. The cage was rigid and microporous, as predicted by the simulations, with an apparent Brunauer-Emmett-Teller surface area of 578 m² g^-1. The reduced symmetry of the tritopic building block relative to its topicity meant there were 36 possible structural isomers of the cage. Experimental characterisation suggests a single isomer with 12 unique imine environments, but techniques such as NMR could not conclusively identify the isomer. Computational structural and electronic analysis of the possible isomers was used to identify the most likely candidates, and hence to construct a 3-dimensional model of the amorphous solid. The rational design of unsymmetrical cages using building blocks with reduced symmetry offers new possibilities in controlling the degree of crystallinity, porosity, and solubility, of self-assembled materials.

Porous Shape-Persistent Organic Cage Compounds of Different Size, Geometry, and Function

The interest in shape-persistent organic cages is nearly as old as the interest in supramolecular chemistry. In the beginning, organic cages have often been synthesized in a stepwise manner, which is not only laborious but very often also accompanied by low overall yields. In 1988, MacDowell published the one pot high-yielding synthesis of [2 + 3] imine cages based on TREN and aromatic dialdehydes, exploiting the reversible condensation of amines and aldehydes to  imines, which was later used by others to make even larger cages on the basis of resorcinarenes. In 2008, the synthesis and characterization of an adamantoid [4 + 6] imine cage by condensation of a C_{3 v}-symmetric triaminotriptycene and commercially available 4- tert-butyl salicyldialdehyde was introduced by the author, which was the ignition of our group activities in this research area. In 2011, we published the first gas-sorption data for this [4 + 6] imine cage: with a measured specific surface area of SA_BET = 1377 m²/g according to the model of Brunauer-Emmett-Teller (BET) this was twice as high as for the reported smaller cages of Cooper. For a second desolvated polymorph of the same cage, an even higher SA_BET = 2071 m²/g was determined; still one of the highest surface areas until date for porous organic molecular materials. Subsequently, the influence of the substituent in 4-position of the salicyldialdehyde for the reaction to [4 + 6] imine cages was investigated as well as the role of the phenolic hydroxyl group. It turned out that the phenolic hydroxyl group is crucial as directing group to increase the formation of the cage as well as stabilize the structure by cyclic six-membered intramolecular hydrogen bonds. The concept was extended to other imine-based cages of different geometry and size. For instance, a [4 + 4] cubic structure from triptycene trissalicylaldehyde and triptycene triamine was accessible as an amorphous insoluble solid, able to adsorb 18.2 wt % CO₂ at ambient conditions. To gain further insight into the structural needs of the molecular precursors, rigidity and preorientation of reacting sites were investigated on prismatic [2 + 3] and truncated tetrahedral [4 + 4] imine cages, showing that rigidity and preorientation is beneficial or even crucial for cage formation. Furthermore, chiral self-sorting was studied on the basic of racemic triamines. Besides imine condensation, we explored the reversible formation of boronic esters from boronic acids and diols. Triptycene tetraol with its 120° angle between the aromatic units has been used in the condensation with benzene triboronic acid to achieve a large cuboctahedral [12 + 8] cage with pore dimensions of 2 nm, which are by IUPAC definition mesoporous. After activation the measured specific surface area was SA_BET = 3758 m²/g, a number rarely achieved even for other porous compounds such as threedimensional framework materials. Smaller tetrahedral [4 + 6] boronic ester cages were synthesized too. These cages show a selective gas sorption with preference of saturated hydrocarbon ethane over ethylene and acetylene. What distinguishes porous materials derived from molecular cages from three-dimensional frameworks or networks the most is their solubility; thus, the cages are soluble porous units (SPUs) in a broader sense. Taking advantage of this, [4 + 6] imine cages were postfunctionalized in solution to change the gas sorption properties in the crystalline state. Furthermore, cage solutions were spray-coated onto quartz crystal microbalances to enhance affinity and selectivity for sensing of airborne analytes. In this Account, the contributions from our lab on porous organic cages are presented.

stk: A python toolkit for supramolecular assembly

A tool for the automated assembly, molecular optimization and property calculation of supramolecular materials is presented. stk is a modular, extensible and open-source Python library that provides a simple Python API and integration with third party computational codes. stk currently supports the construction of linear polymers, small linear oligomers, organic cages in multiple topologies and covalent organic frameworks (COFs) in multiple framework topologies, but is designed to be easy to extend to new, unrelated, supramolecules or new topologies. Extension to metal-organic frameworks (MOFs), metallocycles or supramolecules, such as catenanes, would be straightforward. Through integration with third party codes, stk offers the user the opportunity to explore the potential energy landscape of the assembled supramolecule and then calculate the supramolecule's structural features and properties. stk provides support for high-throughput screening of large batches of supramolecules at a time. The source code of the program can be found at https://github.com/supramolecular-toolkit/stk. © 2018 Wiley Periodicals, Inc.

High-throughput discovery of organic cages and catenanes using computational screening fused with robotic synthesis

Supramolecular synthesis is a powerful strategy for assembling complex molecules, but to do this by targeted design is challenging. This is because multicomponent assembly reactions have the potential to form a wide variety of products. High-throughput screening can explore a broad synthetic space, but this is inefficient and inelegant when applied blindly. Here we fuse computation with robotic synthesis to create a hybrid discovery workflow for discovering new organic cage molecules, and by extension, other supramolecular systems. A total of 78 precursor combinations were investigated by computation and experiment, leading to 33 cages that were formed cleanly in one-pot syntheses. Comparison of calculations with experimental outcomes across this broad library shows that computation has the power to focus experiments, for example by identifying linkers that are less likely to be reliable for cage formation. Screening also led to the unplanned discovery of a new cage topology-doubly bridged, triply interlocked cage catenanes.

Dissecting Porosity in Molecular Crystals: Influence of Geometry, Hydrogen Bonding, and [π···π] Stacking on the Solid-State Packing of Fluorinated Aromatics

Porous molecular crystals are an emerging class of porous materials that is unique in being built from discrete molecules rather than being polymeric in nature. In this study, we examined the effects of molecular structure of the precursors on the formation of porous solid-state structures with a series of 16 rigid aromatics. The majority of these precursors possess pyrazole groups capable of hydrogen bonding, as well as electron-rich aromatics and electron-poor tetrafluorobenzene rings. These precursors were prepared using a combination of Pd- and Cu-catalyzed cross-couplings, careful manipulations of protecting groups on the nitrogen atoms, and solvothermal syntheses. Our study varied the geometry and dimensions of precursors, as well as the presence of groups capable of hydrogen bonding and [π···π] stacking. Thirteen derivatives were crystallographically characterized, and four of them were found to be porous with surface areas between 283 and 1821 m² g^-1. Common to these four porous structures were (a) rigid trigonal geometry, (b) [π···π] stacking of electron-poor tetrafluorobenzenes with electron-rich pyrazoles or tetrazoles, and

Shape-Persistent [4+4] Imine Cages with a Truncated Tetrahedral Geometry

The synthesis of shape-persistent organic cage compounds is often based on the usage of multiple dynamic covalent bond formation (such as imines) of readily available precursors. By careful choice of the precursors geometry, the geometry and size of the resulting cage can be accurately designed and indeed a number of different geometries and sizes have been realized to date. Despite of this fact, little is known about the precursors conformational rigidity and steric preorganization of reacting functional groups on the outcome of the reaction. Herein, the influence of conformational rigidity in the precursors on the formation of a [4+4] imine cage with truncated tetrahedral geometry is discussed.

Porous organic cage stabilised palladium nanoparticles: efficient heterogeneous catalysts for carbonylation reaction of aryl halides

Porous organic cage stabilised palladium nanoparticles were prepared using methanol as a mild reductant and displayed high catalytic activity for the carbonylation reaction of aryl halides under mild conditions.

Design and Validation of a 150 MHz HFFQCM Sensor for Bio-Sensing Applications

Acoustic wave resonators have become suitable devices for a broad range of sensing applications due to their sensitivity, low cost, and integration capability, which are all factors that meet the requirements for the resonators to be used as sensing elements for portable point of care (PoC) platforms. In this work, the design, characterization, and validation of a 150 MHz high fundamental frequency quartz crystal microbalance (HFF-QCM) sensor for bio-sensing applications are introduced. Finite element method (FEM) simulations of the proposed design are in good agreement with the electrical characterization of the manufactured resonators. The sensor is also validated for bio-sensing applications. For this purpose, a specific sensor cell was designed and manufactured that addresses the critical requirements associated with this type of sensor and application. Due to the small sensing area and the sensor’s fragility, these requirements include a low-volume flow chamber in the nanoliter range, and a system approach that provides the appropriate pressure control for assuring liquid confinement while maintaining the integrity of the sensor with a good base line stability and easy sensor replacement. The sensor characteristics make it suitable for consideration as the elemental part of a sensor matrix in a multichannel platform for point of care applications.

Porous Molecular Solids and Liquids

Until recently, porous molecular solids were isolated curiosities with properties that were eclipsed by porous frameworks, such as metal-organic frameworks. Now molecules have emerged as a functional materials platform that can have high levels of porosity, good chemical stability, and, uniquely, solution processability. The lack of intermolecular bonding in these materials has also led to new, counterintuitive states of matter, such as porous liquids. Our ability to design these materials has improved significantly due to advances in computational prediction methods.

Synthesis of 9,9'-Spirobifluorenes and 4,5-Diaza-9,9'-spirobifluorenes and Their Application as Affinity Materials for Quartz Crystal Microbalances

Two different classes of aza analogues of 9,9'-spirobifluorenes have been synthesized. These were obtained by either furnishing the spirobifluorene with additional pyridyl moieties or by installing the aza function directly into the spirobifluorene core. These structurally rigid compounds were then evaluated as affinity materials for quartz crystal microbalances and proved to be highly potent for the detection of volatile organic compounds.

A Perspective on the Synthesis, Purification, and Characterization of Porous Organic Cages

Porous organic cages present many opportunities in functional materials chemistry, but the synthetic challenges for these molecular solids are somewhat different from those faced in the areas of metal-organic frameworks, covalent-organic frameworks, or porous polymer networks. Here, we highlight the practical methods that we have developed for the design, synthesis, and characterization of imine porous organic cages using CC1 and CC3 as examples. The key points are transferable to other cages, and this perspective should serve as a practical guide to researchers who are new to this field.

Transforming a chemically labile [2+3] imine cage into a robust carbamate cage

Turning a pH labile porous cage into a highly pH stable porous organic cage by fixation with carbamate units.