Nanoporous Molecular Sandwiches: Pillared Two-Dimensional Hydrogen-Bonded Networks with Adjustable Porosity

Benchmarking Guanidinium Organosulfonate Hydrogen-Bonded Frameworks for Structure Determination of Encapsulated Guests

Single crystal X-ray diffraction (SCXRD) is arguably the most definitive method for molecular structure determination, but it is often challenged by compounds that are liquids or oils at room temperature or do not form crystals adequate for analysis. Our laboratory previously reported a simple, cost-effective, single-step crystallization method based on guanidinium organosulfonate (GS) hydrogen bonded frameworks for structure determination of a wide range of encapsulated guest molecules, including assignment of the absolute configuration of chiral centers. Herein, we expand on those results and report a head-to-head comparison of the GS method with adamantoid "molecular chaperones", which have been reported to be useful hosts for structure determination. Inclusion compounds limited to only two GS hosts are characterized by low R1 values and Flack parameters, infrequent disorder of the host and guest, and manageable disorder when it does exist. The structures of some target molecules that were not included or resolved using the adamantoid chaperones were successfully included and resolved by the GS hosts, and vice versa. Of the 32 guests attempted by the GS method, 31 inclusion compounds afforded successful guest structure solutions, a 97% success rate. The GS hosts and adamantoid chaperones are complementary with respect to guest inclusion, arguing that both should be employed in the arsenal of methods for structure determination. Furthermore, the low cost of organosulfonate host components promises an accessible route to molecular structure determination for a wide range of users.

Charge-Assisted Ionic Hydrogen-Bonded Organic Frameworks: Designable and Stabilized Multifunctional Materials

Hydrogen-bonded organic frameworks (HOFs) are a class of crystalline framework materials assembled by hydrogen bonds. HOFs have the advantages of high crystallinity, mild reaction conditions, good solution processability, and reproducibility. Coupled with the reversibility and flexibility of hydrogen bonds, HOFs can be assembled into a wide diversity of crystalline structures. Since the bonding energy of hydrogen bonds is lower than that of ligand and covalent bonds, the framework of HOFs is prone to collapse after desolventisation and the stability is not high, which limits the development and application of HOFs. In recent years, numerous stable and functional HOFs have been developed by π-π stacking, highly interpenetrated networks, charge-assisted, ligand-bond-assisted, molecular weaving, and covalent cross-linking. Charge-assisted ionic HOFs introduce electrostatic attraction into HOFs to improve stability while enriching structural diversity and functionality. In this paper, we review the development, the principles of rational design and assembly of charge-assisted ionic HOFs, and introduces the different building block construction modes of charge-assisted ionic HOFs. Highlight the applications of charge-assisted ionic HOFs in gas adsorption and separation, proton conduction, biological applications, etc., and prospects for the diverse design of charge-assisted ionic HOFs structures and multifunctional applications.

Synthesis, growth, optical, mechanical, thermal, dielectric, and SHG properties of Triethylaminium picrate (TEAP) single crystal for nonlinear optical applications

Triethylaminium picrate (TEAP) crystals were grown using the slow evaporation solution growth method at ambient (35 °C) temperature. Salt was synthesized from Picric acid, and Triethylamine and methanol was used as solvents. The solution was mixed at a 1:1 ratio and evaporated slowly, produced yellow colour single crystal of TEAP with an average dimension of 19 × 8 × 5 mm3. The structure of the compound was determined by single-crystal X-ray diffraction (SCXRD) study, which confirms that the crystal is belongs to Orthorhombic crystal system, and its crystallinity was confirmed by the Bragg peak in the powder X-ray diffraction pattern. The superamolecular characteristic of the TEAP was confirmed by the Hirshfield analysis. CHN elemental analysis confirmed the stoichiometry and chemical composition of the synthesized complex salts. FT-IR and Polarized Raman spectral analyses confirmed the presence of different functional groups in the complex. UV-vis-NIR study identified the optical transmission window and the lower (TEAP) cut-off wavelength. Vickers' microhardness analysis determined the mechanical stability of the grown crystal. Studies of dielectric and AC conductivity were analyzed as a function of frequency. The thermogravimetry (TG) and differential thermal analysis (DTA) techniques were used to investigate the thermal behaviour of the material. The Kurtz-Perry powder technique was used to analyze the crystal's nonlinear optical properties (NLO) and found that its SHG efficiency was 1.5 times higher than that of potassium dihydrogen phosphate (KDP). The results from the obtained characterizations conclude that the TEAP crystal could be useful for NLO applications.

Hydrogen-bonded frameworks containing aliphatic 3D linkers show high-capacity water vapour sorption

Hydrogen-bonded frameworks were prepared from a tetra-amidinium component and three-dimensional cubane and bicyclopentane dicarboxylate linkers. Despite the incorporation of aliphatic components, the frameworks demonstrate strong and reversible uptake of water vapour, with one of the frameworks showing water uptake at very low relative humidity.

Hydrogen-bonded organic frameworks: new horizons in biomedical applications

Hydrogen-bonded organic frameworks (HOFs) are an emerging attractive class of highly crystalline porous materials characterized by significant biocompatibility, rich chemical functionalities and well-defined porosity. The unique advantages including metal-free nature and reversible binding manner significantly distinguish HOFs from other porous materials in the biotechnology and biomedical field. However, the relevant HOF studies still remain in their infancy despite the promising and remarkable results that have been presented in recent years. Due to the intricate and dynamic nature of physiological conditions, the major challenge lies in the stability and structural diversity of HOFs in vivo. In this Tutorial Review, we summarize the common building blocks for the construction of HOF-based functional biomaterials and the latest developments in the biological field. Moreover, we highlight current challenges regarding the stability and functionalization of HOFs along with the corresponding potential solutions. This Tutorial Review will have a profound effect in future years on the design and applications of HOF-based biomaterials.

Host-guest system of a phosphorylated macrocycle assisting structure determination of oily molecules in single-crystal form

X-ray crystallography is the most reliable method for structure elucidation and absolute configuration determination of organic molecules based on their single-crystal forms. However, many analytes are hard to crystallize because of their low melting points (an oily state at room temperature) or conformational flexibility. Here, we report the crystallization of a macrocycle, CTX[P(O)Ph] (host), which is a cyclotrixylohydroquinoylene (CTX) derivative, with 26 oily organic molecules (guests), which is applied for the structural determination of the guest with X-ray crystallography. With the aid of the host, CTX[P(O)Ph], the guest molecules were well-ordered with full occupancy in crystal structures. In most cases, at least one guest structure without any disorder could be observed; solvent masking was not necessary for the single crystal X-ray structural analysis, and thus the structures of the guests could be successfully determined, and the absolute configuration could be assigned reliably for chiral guests with this method. The crystallization mechanism was further discussed from theoretical and experimental perspectives, suggesting that the negative electrostatic potential surface of CTX[P(O)Ph] and noncovalent interactions between the host and guest were crucial for the ordered arrangements of the guest.

Pore Modulation of Hydrogen-Bonded Organic Frameworks for Efficient Separation of Propylene

Developing hydrogen-bonded organic frameworks (HOFs) that combine functional sites, size control, and storage capability for targeting gas molecule capture is a novel and challenging venture. However, there is a lack of effective strategies to tune the hydrogen-bonded network to achieve high-performance HOFs. Here, a series of HOFs termed as HOF-ZSTU-M (M=1, 2, and 3) with different pore structures are obtained by introducing structure-directing agents (SDAs) into the hydrogen-bonding network of tetrakis (4-carboxyphenyl) porphyrin (TCPP). These HOFs have distinct space configurations with pore channels ranging from discrete to continuous multi-dimensional. Single-crystal X-ray diffraction (SCXRD) analysis reveals a rare diversity of hydrogen-bonding models dominated by SDAs. HOF-ZSTU-2, which forms a strong layered hydrogen-bonding network with ammonium (NH4 + ) through multiple carboxyl groups, has a suitable 1D "pearl-chain" channel for the selective capture of propylene (C3 H6 ). At 298 K and 1 bar, the C3 H6 storage density of HOF-ZSTU-2 reaches 0.6 kg L-1 , representing one of the best C3 H6 storage materials, while offering a propylene/propane (C3 H6 /C3 H8 ) selectivity of 12.2. Theoretical calculations and in situ SCXRD provide a detailed analysis of the binding strength of C3 H6 at different locations in the pearl-chain channel. Dynamic breakthrough tests confirm that HOF-ZSTU-2 can effectively separate C3 H6 from multi-mixtures.

Green synthesis of stable hybrid biocatalyst using a hydrogen-bonded, π-π-stacking supramolecular assembly for electrochemical immunosensor

Rational integration of native enzymes and nanoscaffold is an efficient means to access robust biocatalyst, yet remains on-going challenges due to the trade-off between fragile enzymes and harsh assembling conditions. Here, we report a supramolecular strategy enabling the in situ fusion of fragile enzymes into a robust porous crystal. A c2-symmetric pyrene tecton with four formic acid arms is utilized as the building block to engineer this hybrid biocatalyst. The decorated formic acid arms afford the pyrene tectons high dispersibility in minute amount of organic solvent, and permit the hydrogen-bonded linkage of discrete pyrene tectons to an extended supramolecular network around an enzyme in almost organic solvent-free aqueous solution. This hybrid biocatalyst is covered by long-range ordered pore channels, which can serve as the gating to sieve the catalytic substrate and thus enhance the biocatalytic selectivity. Given the structural integration, a supramolecular biocatalyst-based electrochemical immunosensor is developed, enabling the pg/mL detection of cancer biomarker.

Charge "mis-matched" hydrogen bonded frameworks for cation exchange and dye sorption

Anionic hydrogen bonded frameworks were synthesised from di or tetra-amidinium hydrogen bond donor components and a charge "mis-matched" tecton possessing a 5- charge but only four hydrogen bond accepting groups. The net negative charge on the framework skeletons necessitates the presence of a cation in the framework channel. In one of the frameworks, the initially incorporated organic cation was rapidly displaced by smaller inorganic cations, or the cationic dye methylene blue. This facilitated the effective and selective removal of this dye from water.

Hybrid Hydrogen-Bonded Organic Frameworks: Structures and Functional Applications

As a new class of porous crystalline materials, hydrogen-bonded organic frameworks (HOFs) assembled from building blocks by hydrogen bonds have gained increasing attention. HOFs benefit from advantages including mild synthesis, easy purification, and good recyclability. However, some HOFs transform into unstable frameworks after desolvation, which hinders their further applications. Nowadays, the main challenges of developing HOFs lie in stability improvement, porosity establishment, and functionalization. Recently, more and more stable and permanently porous HOFs have been reported. Of all these design strategies, stronger charge-assisted hydrogen bonds and coordination bonds have been proven to be effective for developing stable, porous, and functional solids called hybrid HOFs, including ionic and metallized HOFs. This Review discusses the rational design synthesis principles of hybrid HOFs and their cutting-edge applications in selective inclusion, proton conduction, gas separation, catalysis and so forth.

Structural Transformable Coulomb Lattice of n-Type Semiconductors for Guest Sorption

In recent years, highly designable organic porous materials have attracted considerable attention in the development of new types of molecular adsorption-desorption materials. The adsorption-desorption process also changes the electronic structure via the existence of guest molecules. Therefore, it is possible to change the physical property during the guest adsorption-desorption cycle using an appropriate chemical design of the host crystal lattice. As the development of n-type organic semiconductors has been limited, we focused on designing an n-type organic semiconductor material to control the host crystal lattice, electronic dimensionality, chemical stability, and high electron mobility using an ionic naphthalenediimide (NDI) derivative. Low symmetrical dianionic bis(benzene-m-sulfonate)-naphthalenediimide (m-BSNDI^2-) forms various types of single-crystal (M⁺)₂(m-BSNDI^2-)·n(guest) with a combination of M⁺ = Na⁺, K⁺, Rb⁺, and guest = H₂O, CH₃OH. Four crystals of (K⁺)₂(m-BSNDI^2-)·n(H₂O), (K⁺)₂(m-BSNDI^2-)·n(CH₃OH), α-(K⁺)₂(m-BSNDI^2-), and β-(K⁺)₂(m-BSNDI^2-) were transformable using the guest adsorption-desorption cycle. Two kinds of single-crystal (K⁺)₂(m-BSNDI^2-)·n(CH₃OH) with n = 0 and 2.0 showed a single-crystal to single-crystal (SCSC) transformation through CH₃OH desorption. On the contrary, five kinds of single crystals with n = 0, 3.0, 3.3, 4.75, and 5.5 were identified in the single-crystal X-ray structural analyses of (K⁺)₂(m-BSNDI^2-)·n(H₂O). Systematic change of the ionic radii in (M⁺)₂(m-BSNDI^2-) modified the crystal lattice flexibility for the guest adsorption-desorption cycles.

Photodynamic Hydrogen-Bonded Biohybrid Framework: A Photobiocatalytic Cascade Nanoreactor for Accelerating Diabetic Wound Therapy

A diabetic wound causes thousands of infections or deaths around the world each year, and its healing remains a critical challenge because of the ease of multidrug-resistant (MDR) bacterial infection, as well as the intrinsic hyperglycemic and hypoxia microenvironment that inhibits the therapeutic efficiency. Herein, we pioneer the design of a photobiocatalytic cascade nanoreactor via spatially organizing the biocatalysts and photocatalysts utilizing a hydrogen-bonded organic framework (HOF) scaffold for diabetic wound therapy. The HOF scaffold enables it to disperse and stabilize the host cargos, and the formed long-range-ordered mesochannels also facilitate the mass transfer that enhances the cascade activity. This integrated HOF nanoreactor allows the continuous conversion of overexpressed glucose and H₂O₂ into toxic reactive oxygen species by the photobiocatalytic cascade. As a result, it readily reverses the microenvironment of the diabetes wound and exhibits an extraordinary capacity for wound healing through synergistic photodynamic therapy. This work describes the first example of constructing an all-in-one HOF bioreactor for antimicrobial diabetes wound treatment and showcases the promise of combined biocatalysis and photocatalysis achieved by using an HOF scaffold in biomedicine applications.

Solvent-Triggered Fast and Visible Switching between Cage- and Channel-Type Hydrogen-Bonded Organic Frameworks

The inherent weak bonding nature of hydrogen-bonded organic frameworks (HOFs) performs like a double-edged sword in that it endows HOFs with superiority in processability and dynamicity but deactivates its on-demand controllability in the crystalline phase. Herein, based on the synergy of dynamic H-bonding interactions and the tailored low solubility in common organic solvents, reversible and fast topological transitions between cage- and channel-type HOFs were achieved upon immersing in the solution state. The aggregation-induced-emission character of the tecton facilitates the visualization of the elusive initial transition process with high sensitivity. In addition, the visible transition from cage- and channel-type HOFs to thermally stable crystalline phases is also achieved under thermal induction.

Multiple yet switchable hydrogen-bonded organic frameworks with white-light emission

The development of new strategies to construct on-demand porous lattice frameworks from simple motifs is desirable. However, mitigating complexity while combing multiplicity and reversibility in the porous architectures is a challenging task. Herein, based on the synergy of dynamic intermolecular interactions and flexible molecular conformation of a simple cyano-modified tetraphenylethylene tecton, eleven kinetic-stable hydrogen-bonded organic frameworks (HOFs) with various shapes and two thermo-stable non-porous structures with rare perpendicular conformation are obtained. Multimode reversible structural transformations along with visible fluorescence output between porous and non-porous or between different porous forms is realized under different external stimuli. Furthermore, the collaborative of flexible framework and soft long-chain guests facilitate the relaxation from intrinsic blue emission to yellow emission in the excited state, which represents a strategy for generating white-light emission. The dynamic intermolecular interactions, facilitated by flexible molecular conformation and soft guests, diversifies the strategies of construction of versatile smart molecular frameworks.

Switchable hydrogen-bonded frameworks have potential applications in the development of smart materials. Herein, the authors report eleven hydrogen-bonded organic frameworks and two non-porous structures that can undergo reversible structural and fluorescence switching; white-light emission is enabled.

Hydrogen-Bonded Metal-Nucleobase Frameworks for Efficient Separation of Xenon and Krypton

Xe/Kr separation is an industrially important but challenging process owing to their inert properties and low concentrations in the air. Energy-effective adsorption-based separation is a promising technology. Herein, two isostructural hydrogen-bonded metal-nucleobase frameworks (HOF-ZJU-201 and HOF-ZJU-202) are capable of separating Xe/Kr under ambient conditions and strike an excellent balance between capacity and selectivity. The Xe capacity of HOF-ZJU-201a reaches 3.01 mmol g-1 at 298 K and 1.0 bar, while IAST selectivity and Henry's selectivity are 21.0 and 21.6, respectively. Direct breakthrough experiments confirmed the excellent separation performance, affording a Xe capacity of 25.8 mmol kg-1 from a Xe/Kr mixed-gas at dilute concentrations. Density functional theory calculations revealed that the selective binding arises from the enhanced polarization in the confined electric field produced by the electron-rich anions and the electron-deficient purine heterocyclic rings.

Towards hydrogen and halogen bonded frameworks based on 3,5-bis(triazolyl)pyridinium motifs

Construction of supramolecular assemblies using hydrogen and halogen bonding between anions and the 3,5-bis(triazolyl)pyridinium motif was investigated.

Use of modulators and light to control crystallisation of a hydrogen bonded framework

The effect of concentration, organic co-solvent, and salt modulators on the crystallisation of a hydrogen bonded framework was studied. The framework contains ∼1.4 nm wide channels and contains a diazobenzene based dicarboxylate anion. Light-induced cis/trans switching of this anion was also used to control crystallisation.

Amidinium⋯carboxylate frameworks: predictable, robust, water-stable hydrogen bonded materials

In the last few years, the amidinium⋯carboxylate interaction has emerged as a powerful tool for the relatively predictable construction of families of three dimensional hydrogen bonded organic frameworks. These frameworks can be prepared in water and are surprisingly stable, including to heating in polar organic solvents and water. This feature article describes the design and synthesis of these materials, discusses their structures and stability, and highlights their recent applications for enzyme encapsulation and as precursors for the synthesis of molecularly thin hydrogen bonded 2D nanosheets.

Various Stacking Patterns of Two-Dimensional Molecular Assemblies in Hydrogen-Bonded Cocrystals: Insight on Competitive Intermolecular Interactions and Control of Stacking Patterns

We first demonstrate the rational control over the stacking patterns in two-dimensional (2D) molecular assemblies using chemical modification. A target system is a hydrogen-bonded cocrystal composed of 2-pyrrolidone (Py) and chloranilic acid (CA) with 2:1 composition ( PyCA ). X-ray crystallography revealed that various weak intersheet interactions give rise to a variety of metastable overlapping patterns comprised of the 2D assemblies mainly formed via hydrogen bonds, affording reversible and irreversible structural phase transitions. We successfully prepared cocrystals of Py and anilic acids bearing different halogens, in which 2D assemblies isostructural with those observed in PyCA exhibit various overlapping patterns. The order of stability for each overlapping pattern estimated using theoretical calculations of the intermolecular interactions did not completely coincide with those indicated by our experimental results, which can be explained by considering the entropic effect, i.e., the molecular motion of Py as detected using nuclear quadrupole resonance spectroscopy.

Incorporating Guanidinium as Perovskitizer-Cation of Two-Dimensional Metal Halide for Crystal-Array Photodetectors

Two-dimensional (2D) hybrid perovskites are recently emerging as a potential family of semiconductors for versatile optoelectronic applications. Currently, the "perovskitizer" moieties are rigidly limited to small-size cations, while few 2D metal-halides containing guanidinium cations inside perovskite cages have been studied for photodetection. Herein, we present a new 2D hybrid perovskite, (i-BA)₂ (G)Pb₂ I₇ (where G is guanidinium and i-BA is isobutylammonium), which adopts a bilayered framework of {GPb₂ I₇ }. Single-crystal structure analyses disclose that G cations act as the perovskitizer, confined in the flexible perovskite cages formed by the distorted PbI₆ octahedra. Such inorganic sheets are crucial to the superior semiconducting properties and optical bandgap, as verified by the density functional theory calculation. Furthermore, its planar crystal-array photodetector shows fascinating photoelectric performance, including a quite low dark current (∼4.6×10^-11  A), a large current switching ratio (∼1.0×10³ ), and a notable photo-responsivity of ∼0.72 A W^-1 , suggesting great potential of (i-BA)₂ (G)Pb₂ I₇ for photodetection.

Ratchet-like mechanism in a long-life photoproduct of salicylideneaniline enclathrated in a pillared-layer guanidinium disulfonate structure

Salicylideneaniline (SA) was found to exhibit extraordinary long-life photochromism upon being included in a cavity of guanidinium organosulfonate and exhibited a lifetime of ∼30 times that of a pure SA crystal. Crystal structure analysis suggested that the sulfonate molecule in the apo-host provided a flexible cavity space that kinetically trapped SA in its photo-isomerized form, as if it was locked by a ratchet-like mechanism.

A certain molecular environment in a hydrogen-bonded framework may extremely prolong the lifetime of photo-induced, colored species.

Robust Supramolecular Nano-Tunnels Built from Molecular Bricks*

Herein we report a linear ionic molecule that assembles into a supramolecular nano-tunnel structure through synergy of trident-type ionic interactions and π-π stacking interactions. The nano-tunnel crystal exhibits anisotropic guest adsorption behavior. The material shows good thermal stability and undergoes multi-stage single-crystal-to-single-crystal phase transformations to a nonporous structure on heating. The material exhibits a remarkable chemical stability under both acidic and basic conditions, which is rarely observed in supramolecular organic frameworks and is often related to structures with designed hydrogen-bonding interactions. Because of the high polarity of the tunnels, this molecular crystal also shows a large CO₂ -adsorption capacity while excluding other gases at ambient temperature, leading to high CO₂ /CH₄ selectivity. Aggregation-induced emission of the molecules gives the bulk crystals vapochromic properties.

Monolayer nanosheets formed by liquid exfoliation of charge-assisted hydrogen-bonded frameworks

Hydrogen-bonded organic frameworks (HOFs) are a diverse and tunable class of materials, but their potential as free-standing two-dimensional nanomaterials has yet to be explored. Here we report the self-assembly of two layered hydrogen-bonded frameworks based on strong, charge-assisted hydrogen-bonding between carboxylate and amidinium groups. Ultrasound-assisted liquid exfoliation of both materials readily produces monolayer hydrogen-bonded organic nanosheets (HONs) with micron-sized lateral dimensions. The HONs show remarkable stability and maintain their extended crystallinity and monolayer structures even after being suspended in water at 80 °C for three days. These systems also exhibit efficient fluorescence quenching of an organic dye in organic solvents, superior to the quenching ability of the bulk frameworks. We anticipate that this approach will provide a route towards a diverse new family of molecular two-dimensional materials.

Dynamic structural reconstruction of (guanidinium+)2(benzene-1,4-disulfonate2−) host crystal by guest adsorption

Guanidinium (G⁺) and benzene-1,4-disulfonate (BDS²⁻) form a rigid electrostatic cation–anion crystal lattice, which undergoes an interesting dynamic structural reconstruction through guest adsorption–desorption processes.

Advanced pillared designs for two-dimensional materials in electrochemical energy storage

Two-dimensional (2D) materials have attracted increased attention as advanced electrodes in electrochemical energy storage owing to their thin nature and large specific surface area. However, limited interlayer spacing confines the mass and ion transport within the layers, resulting in poor rate performance. Considerable efforts have been made to deal with this intrinsic problem of pristine 2D materials. Among them, interlayer engineering through pillared designs offers abundant electrochemical active sites and promotes ion diffusion. Synergetic effects between incorporated species and 2D hosts offer much better conductivity and surface modification. As a result, 2D materials with advanced pillared designs demonstrate great enhancement of specific capacity/capacitance and rate performance. Herein, we summarize the recent progress of pillared 2D materials in relation to the intercalated species. Moreover, we highlight their typical applications in lithium-ion storage and beyond to provide some insights on future trends towards this research area.

Complementarity in Cyclotricatechylene Assemblies: Symmetric Cages Linked within 3D Cubic Hydrogen Bonded Networks

A serendipitous discovery has led to the generation of a family of four compounds in which six components combine to form symmetric metal-cyclotricatechylene (H6ctc) cages. The four compounds, which have the compositions, [Cs((CH3)2CO)6][K4(H6ctc)4(H2O)8][Cs4(H2O)6](PO4)3, [Rb((CH3)2CO)6][Rb2K2(H6ctc)4(H2O)6][Rb4(H2O)6](PO4)3, [Cs((CH3)2CO)6][K4(H6ctc)4(H2O)8]-[Cs(H2O)9](SO4)3 and [Rb((CH3)2CO)6][Rb2K2(H6ctc)4(H2O)6][Rb(H2O)9](SO4)3 possess cubic symmetry that arises from the complementary interactions that govern the assembly of the components. The cage cavities contain water molecules and either one or four large alkali metal ions (either Rb+ or Cs+) which interact with the internal aromatic surfaces of the cage. Each cage is linked to six tetrahedral anions (PO43− or SO42−) through 24 equivalent hydrogen bonds and each anion bridges a pair of cages through eight such hydrogen bonds. An unusual octahedral complex M((CH3)2CO)6+ (M = Rb or Cs), in which the M-C=O link is linear, appears to be a key structural component. A feature of this family of crystalline compounds is the presence of a range of complementary interactions which combine to generate materials that exhibit high crystallographic symmetry.

Encapsulation of the [Ru(bpy)3]2+ luminophore in a unique hydrogen-bonded host framework

One-dimensional networks of the well-known photosensitizer [Ru(bpy)₃]²⁺ are encapsulated in an unusual hydrogen-bonded crystalline host framework.

Hydrogen-bonded frameworks for molecular structure determination

Single crystal X-ray diffraction is arguably the most definitive method for molecular structure determination, but the inability to grow suitable single crystals can frustrate conventional X-ray diffraction analysis. We report herein an approach to molecular structure determination that relies on a versatile toolkit of guanidinium organosulfonate hydrogen-bonded host frameworks that form crystalline inclusion compounds with target molecules in a single-step crystallization, complementing the crystalline sponge method that relies on diffusion of the target into the cages of a metal-organic framework. The peculiar properties of the host frameworks enable rapid stoichiometric inclusion of a wide range of target molecules with full occupancy, typically without disorder and accompanying solvent, affording well-refined structures. Moreover, anomalous scattering by the framework sulfur atoms enables reliable assignment of absolute configuration of stereogenic centers. An ever-expanding library of organosulfonates provides a toolkit of frameworks for capturing specific target molecules for their structure determination.

Designing Hydrogen-Bonded Organic Frameworks (HOFs) with Permanent Porosity

Designing organic components that can be used to construct porous materials enables the preparation of tailored functionalized materials. Research into porous materials has seen a resurgence in the past decade as a result of finding of self-standing porous molecular crystals (PMCs). Particularly, a number of crystalline systems with permanent porosity that are formed by self-assembly through hydrogen bonding (H-bonding) have been developed. Such systems are called hydrogen-bonded organic frameworks (HOFs). Herein we systematically describe H-bonding patterns (supramolecular synthons) and molecular structures (tectons) that have been used to achieve thermal and chemical durability, a large surface area, and functions, such as selective gas sorption and separation, which can provide design principles for constructing HOFs with permanent porosity.

Recent advances in self-assembled amidinium and guanidinium frameworks

Recent advances in amidinium and guanidinium-containing hydrogen-bonded framework materials are highlighted.

Comparing the host behaviour ofN,N′-bis(9-phenyl-9-thioxanthenyl)ethylenediamine andN,N′-bis(9-phenyl-9-xanthenyl)ethylenediamine in the presence of various alkylated aromatic and aniline guests: crystal engineering considerations

N,N′-Bis(9-phenyl-9-thioxanthenyl)ethylenediamine andN,N′-bis(9-phenyl-9-xanthenyl)ethylenediamine were assessed for their host behaviour in the presence of various alkylated aromatics and anilines.

Adsorption of anthracene substitutes into suprachannels: bulk vs. included guests

Investigation of FRET of included anthracene substitutes within unusual hydrophobic suprachannels was carried out.

From dynamic self-assembly to networked chemical systems

Although dynamic self-assembly, DySA, is a relatively new area of research, the past decade has brought numerous demonstrations of how various types of components - on scales from (macro)molecular to macroscopic - can be arranged into ordered structures thriving in non-equilibrium, steady states. At the same time, none of these dynamic assemblies has so far proven practically relevant, prompting questions about the field's prospects and ultimate objectives. The main thesis of this Review is that formation of dynamic assemblies cannot be an end in itself - instead, we should think more ambitiously of using such assemblies as control elements (reconfigurable catalysts, nanomachines, etc.) of larger, networked systems directing sequences of chemical reactions or assembly tasks. Such networked systems would be inspired by biology but intended to operate in environments and conditions incompatible with living matter (e.g., in organic solvents, elevated temperatures, etc.). To realize this vision, we need to start considering not only the interactions mediating dynamic self-assembly of individual components, but also how components of different types could coexist and communicate within larger, multicomponent ensembles. Along these lines, the review starts with the discussion of the conceptual foundations of self-assembly in equilibrium and non-equilibrium regimes. It discusses key examples of interactions and phenomena that can provide the basis for various DySA modalities (e.g., those driven by light, magnetic fields, flows, etc.). It then focuses on the recent examples where organization of components in steady states is coupled to other processes taking place in the system (catalysis, formation of dynamic supramolecular materials, control of chirality, etc.). With these examples of functional DySA, we then look forward and consider conditions that must be fulfilled to allow components of multiple types to coexist, function, and communicate with one another within the networked DySA systems of the future. As the closing examples show, such systems are already appearing heralding new opportunities - and, to be sure, new challenges - for DySA research.

Pyrene-box capsules for adaptive encapsulation and structure determination of unstable or non-crystalline guest molecules

“Pyrene-box” cages easily crystallize from aqueous solutions and readily encapsulate compounds of biological interest.