Organic Crystalline Materials Research Articles

Study of the solvent-dependent crystal shape of theophylline using constant chemical potential molecular dynamics simulations.

The crystal habit of an organic crystalline material impacts its properties, processing, and performance, especially in pharmaceuticals. In solution crystallization, solvents play a crucial role in modulating the crystal habits by interacting with the different growing facets - either enhancing or inhibiting the growth of specific facets. Thus, an in-depth understanding of the role of the solvent in crystal shape selection is of paramount importance for the design and growth of crystals. In this work, we used constant chemical potential molecular dynamics (CμMD) to simulate the growth of theophylline crystals in solvents with decreasing polarity, i.e. water, isopropyl alcohol, and dimethylformamide. Our results indicate that as the polarity of the solvent increases, theophylline crystallizes into rod-shaped crystals; the aspect ratio is modulated by the relative growth of the (001) and (010) facets. Furthermore, solvent profile analyses revealed that the desolvation of the crystal facets plays a major role in the growth process.

Nearly three-dimensional Dirac fermions in an organic crystalline material unveiled by electron spin resonance

Original analysis methods of the electron spin resonance revealed that nearly three-dimensional Dirac fermions coexistent with standard fermions in an organic charge-transfer complex with each temperature-dependence and rotation symmetry.

Water-chain mediated proton conductivity in mechanically flexible redox-active organic single crystals

Investigating the electrochemical features of proton-conducting flexible organic crystalline materials is crucial for the development of efficient energy storage and conversion devices.

Covalent Organic Frameworks: Opportunities for Rational Materials Design in Cancer Therapy

AbstractNanomedicines are extensively used in cancer therapy. Covalent organic frameworks (COFs) are crystalline organic porous materials with several benefits for cancer therapy, including porosity, design flexibility, functionalizability, and biocompatibility. This review examines the use of COFs in cancer therapy from the perspective of reticular chemistry and function‐oriented materials design. First, the modification sites and functionalization methods of COFs are discussed, followed by their potential as multifunctional nanoplatforms for tumor targeting, imaging, and therapy by integrating functional components. Finally, some challenges in the clinical translation of COFs are presented with the hope of promoting the development of COF‐based anticancer nanomedicines and bringing COFs closer to clinical trials.

Covalent Organic Frameworks: Opportunities for Rational Materials Design in Cancer Therapy.

Nanomedicines are extensively used in cancer therapy. Covalent organic frameworks (COFs) are crystalline organic porous materials with several benefits for cancer therapy, including porosity, design flexibility, functionalizability, and biocompatibility. This review examines the use of COFs in cancer therapy from the perspective of reticular chemistry and function-oriented materials design. First, the modification sites and functionalization methods of COFs are discussed, followed by their potential as multifunctional nanoplatforms for tumor targeting, imaging, and therapy by integrating functional components. Finally, some challenges in the clinical translation of COFs are presented with the hope of promoting the development of COF-based anticancer nanomedicines and bringing COFs closer to clinical trials.

Atomistic-Level Effects of Noncovalent Interactions and Crystalline Packing for Organic Material Structural Integrity upon Exposure to Gamma Radiation.

Developing an atomistic understanding of ionizing radiation induced changes to organic materials is necessary for intentional design of greener and more sustainable materials for radiation shielding and detection. Cocrystals are promising for these purposes, but a detailed understanding of how the specific intermolecular interactions within the lattice upon exposure to radiation affect the structural stability of the organic crystalline material is unknown. This study evaluates atomistic-level effects of γ radiation on both single- and multicomponent organic crystalline materials and how specific noncovalent interactions and packing within the crystalline lattice enhance structural stability. Dose studies were performed on all crystalline systems and evaluated via experimental and computational methods. Changes in crystallinity were evaluated by p-XRD and free radical formation was analyzed via EPR spectroscopy. Type of intermolecular interactions and packing within the crystal lattice was delineated and related to the specific free radical species formed and the structural integrity of each material. Periodic DFT and HOMO-LUMO surface mapping calculations provided atomistic-level identifications of the most probable sites for the radicals formed upon exposure to γ radiation and relate intermolecular interactions and molecular packing within the crystalline lattice to experimental results.

Review of Applications of Density Functional Theory (DFT) Quantum Mechanical Calculations to Study the High-Pressure Polymorphs of Organic Crystalline Materials.

Since its inception, chemistry has been predominated by the use of temperature to generate or change materials, but applications of pressure of more than a few tens of atmospheres for such purposes have been rarely observed. However, pressure is a very effective thermodynamic variable that is increasingly used to generate new materials or alter the properties of existing ones. As computational approaches designed to simulate the solid state are normally tuned using structural data at ambient pressure, applying them to high-pressure issues is a highly challenging test of their validity from a computational standpoint. However, the use of quantum chemical calculations, typically at the level of density functional theory (DFT), has repeatedly been shown to be a great tool that can be used to both predict properties that can be later confirmed by experimenters and to explain, at the molecular level, the observations of high-pressure experiments. This article's main goal is to compile, analyze, and synthesize the findings of works addressing the use of DFT in the context of molecular crystals subjected to high-pressure conditions in order to give a general overview of the possibilities offered by these state-of-the-art calculations.

Exquisite control of electronic and spintronic properties on highly porous Covalent Organic Frameworks (COFs): transition metal intercalation in bilayers

Two-dimensional covalent organic frameworks (2D COFs) are crystalline organic porous materials stacked in a layered fashion. In general, these materials have excellent structural tunability, which can be achieved through the various tools of organic synthesis. Their layered and porous nature makes them attractive candidates for electronics, optoelectronics, and catalysis. However, their application is still limited due to relatively poor π-delocalization and practical applications require controlling and tuning their electronic structure. In this paper, using hybrid density functional theory, we computationally explore a novel 2D COF architecture, consisting of only two crystalline atomic layers made of benzene, boroxine, and triazine rings. We study the intercalation of first-row transition metals in the bilayer to enhance and fine-tune their electronic and magnetic behavior. This resulted in the development of one pristine bilayer, 63 intercalated bilayers, and one trilayer 2D COF. We found that the concentration and position of transition metals in the structure can drastically change the 2D COFs’ electronic, magnetic, and spintronic features. Based on their spin-polarized electronic properties, these transition metal-intercalated 2D COFs have potential applications as water splitting catalysts, direct semiconductors in the visible range, half metals, half semiconductors, and bipolar magnetic semiconductors.

Recent Progress in Design Principles of Covalent Organic Frameworks for Rechargeable Metal-Ion Batteries.

Covalent organic frameworks (COFs) are acknowledged as a new generation of crystalline organic materials and have garnered tremendous attention owing to their unique advantages of structural tunability, frameworks diversity, functional versatility, and diverse applications in drug delivery, adsorption/separation, catalysis, optoelectronics, and sensing, etc. Recently, COFs is proven to be promising candidates for electrochemical energy storage materials. Their chemical compositions and structures can be precisely tuned and functionalized at the molecular level, allowing a comprehensive understanding of COFs that helps to make full use of their features and addresses the inherent drawback based on the components and functions of the devices. In this review, the working mechanisms and the distinguishing advantages of COFs as electrodes for rechargeable Li-ion batteries are discussed in detail. Especially, principles and strategies for the rational design of COFs as advanced electrode materials in Li-ion batteries are systematically summarized. Finally, this review is structured to cover recent explorations and applications of COF electrode materials in other rechargeable metal-ion batteries.

Formation of polyrotaxane crystals driven by dative boron-nitrogen bonds.

The integration of mechanically interlocked molecules (MIMs) into purely organic crystalline materials is expected to produce materials with properties that are not accessible using more classic approaches. To date, this integration has proved elusive. We present a dative boron-nitrogen bond-driven self-assembly strategy that allows for the preparation of polyrotaxane crystals. The polyrotaxane nature of the crystalline material was confirmed by both single-crystal x-ray diffraction analysis and cryogenic high-resolution low-dose transmission electron microscopy. Enhanced softness and greater elasticity are seen for the polyrotaxane crystals than for nonrotaxane polymer controls. This finding is rationalized in terms of the synergetic microscopic motion of the rotaxane subunits. The present work thus highlights the benefits of integrating MIMs into crystalline materials.

Water/Vapor Assisted Fabrication of Large-Area Superprotonic Conductive Covalent Organic Framework Membranes.

Fabrication of large-area ionic covalent organic framework membranes (iCOMs) remains a grand challenge. Herein, the authors report the liquid water and water vapor-assisted fabrication of large-area superprotonic conductive iCOMs. A mixed monomer solution containing 1,3,5-triformylphloroglucinol (TFP) in 1,4-dioxane and p-diaminobenzenesulfonic acid (DABA) in water is first polymerized to obtain a pristine membrane which subsequently underwent crystallization process in mixed vapors containing water vapor. During the polymerization stage, water played a role of a diluting agent, weakening the Coulombic repulsion between sulfonic acid groups. During the crystallization stage, water vapor played a role of a structure-directing agent to facilitate the formation of highly crystalline, large-area iCOMs. The resulting membranes achieved a proton conductivity value of 0.76 S cm-1 at 90 °C under 100% relative humidity, which is among the highest ever reported. Using liquid water and water vapor as versatile additives open a novel avenue to the fabrication of large-area membranes from covalent organic frameworks and other kinds of crystalline organic framework materials.

Tunable electrical conductivity in covalent organic frameworks by intercalation of electron acceptor molecules

Covalent organic frameworks (COFs) are crystalline organic materials with high porosity. The COFs are typically electrical insulators because of their wide bandgaps and closed-shell structures despite their π–π layer stacking motif suitable for carrier conduction. Here, we report a strategy for realizing tunable electrical conductivity in COFs by intercalating redox-active guest molecules. The approach is demonstrated using COF-5 with a boronate-ester-linked two-dimensional structure and one-dimensional nanopore channels infiltrated by 7,7,8,8-tetracyanoquinododimethane (TCNQ). Successful incorporation of guest TCNQ molecules into the cavities of the COF-5 host is confirmed by vibrational and optical spectroscopies and results in the appearance of guest–host charge-transfer transitions for TCNQ-intercalated COF-5. Overall electrical conductivities are enhanced by the carrier generation induced by the charge transfer between TCNQ and COF-5 with the retained layer-stacked structures in COF-5 also contributing to the conduction pathways. The tunable electronic properties of COFs realized by the host–guest strategies established here will further promote refinement of design principles of conductive COFs and deeper understanding of the conduction mechanism while simultaneously providing opportunities for using COFs in diverse applications.

Beyond Solvothermal: Alternative Synthetic Methods for Covalent Organic Frameworks

AbstractCovalent organic frameworks (COFs) are crystalline porous organic materials that hold a wealth of potential applications across various fields. The development of COFs, however, is significantly impeded by the dearth of efficient synthetic methods. The traditional solvothermal approach, while prevalent, is fraught with challenges such as complicated processes, excessive energy consumption, long reaction times, and limited scalability, rendering it unsuitable for practical applications. The quest for simpler, quicker, more energy‐efficient, and environmentally benign synthetic strategies is thus paramount for bridging the gap between academic COF chemistry and industrial application. This Review provides an overview of the recent advances in alternative COF synthetic methods, with a particular emphasis on energy input. We discuss representative examples of COF synthesis facilitated by microwave, ultrasound, mechanic force, light, plasma, electric field, and electron beam. Perspectives on the advantages and limitations of these methods against the traditional solvothermal approach are highlighted.

Beyond Solvothermal: Alternative Synthetic Methods for Covalent Organic Frameworks.

Covalent organic frameworks (COFs) are crystalline porous organic materials that hold a wealth of potential applications across various fields. The development of COFs, however, is significantly impeded by the dearth of efficient synthetic methods. The traditional solvothermal approach, while prevalent, is fraught with challenges such as complicated processes, excessive energy consumption, long reaction times, and limited scalability, rendering it unsuitable for practical applications. The quest for simpler, quicker, more energy-efficient, and environmentally benign synthetic strategies is thus paramount for bridging the gap between academic COF chemistry and industrial application. This Review provides an overview of the recent advances in alternative COF synthetic methods, with a particular emphasis on energy input. We discuss representative examples of COF synthesis facilitated by microwave, ultrasound, mechanic force, light, plasma, electric field, and electron beam. Perspectives on the advantages and limitations of these methods against the traditional solvothermal approach are highlighted.

Recent Progress of Covalent Organic Frameworks Applied in Electrochemical Sensors.

As an emerging porous crystalline organic material, the covalent organic frameworks (COFs) are given more and more attention in many fields, such as gas storage and separation, catalysis, energy storage and conversion, luminescent devices, drug delivery, pollutant adsorption and removal, analysis and detection due to their special advantages of high crystallinity, flexible designability, controllable porosities and topologies, intrinsic chemical and thermal stability. In recent years, the COFs are applied in analytical chemistry, for instance, chromatography, solid-phase microextraction, luminescent and colorimetric sensing, surface-enhanced Raman scattering and electroanalytical chemistry. The COFs decorated electrodes show high performance for detecting trace substances with remarkable selectivity and sensitivity, such as heavy metal ions, glucose, hydrogen peroxide, drugs, antibiotics, explosives, phenolic compounds, pesticides, disease metabolites and so on. This review mainly summarized the application of COF based electrochemical sensor according to different target analytes.

Accurate structure models and absolute configuration determination using dynamical effects in continuous-rotation 3D electron diffraction data

Continuous-rotation 3D electron diffraction methods are increasingly popular for the structure analysis of very small organic molecular crystals and crystalline inorganic materials. Dynamical diffraction effects cause non-linear deviations from kinematical intensities that present issues in structure analysis. Here, a method for structure analysis of continuous-rotation 3D electron diffraction data is presented that takes multiple scattering effects into account. Dynamical and kinematical refinements of 12 compounds—ranging from small organic compounds to metal–organic frameworks to inorganic materials—are compared, for which the new approach yields significantly improved models in terms of accuracy and reliability with up to fourfold reduction of the noise level in difference Fourier maps. The intrinsic sensitivity of dynamical diffraction to the absolute structure is also used to assign the handedness of 58 crystals of 9 different chiral compounds, showing that 3D electron diffraction is a reliable tool for the routine determination of absolute structures.

Oriented Covalent Organic Framework Film Synthesis from Azomethine Compounds

AbstractStrategies enabling solution processing of covalent organic framework (COF) thin films will become increasingly important as these versatile materials are integrated into a wide range of electronic and optical devices. This work highlights an approach to yield thin film synthesis of TAPA‐PDA (TAPA: tris(4‐aminophenyl)amine, PDA: terephthalaldehyde) and TAPB‐PDA (TAPB: 1,3,5‐tris(4‐aminophenyl)benzene) imine COFs using azomethine compounds which can be drop cast onto a variety of substrates. High crystalline COF films are shown to form on various electronically‐relevant substrates. Grazing incidence wide angle X‐ray scattering characterization reveals COF films with a preferred horizontal orientation in the case of TAPA‐PDA COF and a more mixed/vertical orientation in the TAPB‐PDA COF film regardless of the substrate. As this exciting class of crystalline organic materials becomes more relevant for various device applications, solution processing techniques will be vital to take advantage of the properties of thin film COFs.

Crystal packing and photoelectric property of bis(2-picolyl)amine-functionalized triarylborane and its complexes

Organic crystalline materials are attracting increasing interest due to their promising applications in the fields of nonlinear optics (NLO), organic lasers, optical waveguides, and light-emitting transistors. In this paper, a photoelectric molecule QB was constructed through combining an electron-withdrawing unit, a triarylborane, and a metal-ligand unit of bis(2-picolyl)amine. The crystallization behavior and crystalline photoelectric properties of QB and its complexes were thoroughly studied. This compound exhibited polymorphism, and a green emitting block-like crystal and blue-emission lamellar crystal were obtained, respectively. Their different photoluminescence mechanisms were clarified through X-ray crystallographic analysis and theoretical calculations. Furthermore, the single-crystal structures of the complexes of QB coordinating with KCN and Zn(ClO4)2 were also determined. Crystal QB-KCN emitted strong blue fluorescence at 445 nm, owing to the formation of rigid 2-to-2 adduct, which could effectively suppress non-radiative transitions. Crystal QB-Zn(ClO4)2 showed very weak cyan emission due to its loose molecular packing. The electrochemical results illuminated that the metal coordination can effectively affect the electron-withdrawing ability of conjugated triarylborane, and further affect the monomolecular luminescent properties due to the intramolecular charge transfer. We believe that polymorphism and metal coordination are available means to obtain excellent crystalline photoelectric materials.

Effects of Gamma Radiation on Single- and Multicomponent Organic Crystalline Materials.

Exploration of highly ionizing radiation damage to organic materials has mainly been limited to polymers and single-component organic crystals due to their use in coatings and scintillation detection. Additional efforts are needed to create new tunable organic systems with stability in highly ionizing radiation to rationally design novel materials with controllable chemical and physical properties. Cocrystals are a promising class of compounds in this area because of the ability to rationally design bonding and molecular interactions that could lead to novel material properties. However, currently it is unclear if cocrystals exposed to radiation will maintain crystallinity, stability, and physical properties. Herein, we report the effects of γ radiation on both single-component- and multicrystalline organic materials. After irradiation with 11 kGy dose both single- (trans-stilbene, trans-1,2-bis(4-pyridyl)ethylene (4,4'-bpe), 1,n-diiodotetrafluorobenzene (1,n-C6I2F4 ), 1,n-dibromotetrafluorobenzene (1,n-C6Br2F4 ), 1,n-dihydroxybenzene (1,n-C6H6O2 ) (where n = 1, 2, or 3)), and multicomponent materials (4,4'-bpe)·(1,n-C6I2F4 ), (4,4'-bpe)·(1,n-C6Br2F4 ), and (4,4'-bpe)·(1,n-C6H6O2 ) were analyzed and compared to their preirradiated forms. Radiation damage was evaluated via single-crystal- and powder-X-ray diffraction, Raman spectroscopy, differential scanning calorimetry, and solid-state fluorimetry. Single-crystal X-ray diffraction analysis indicated minimal changes in the lattice postirradiation, but additional crystallinity changes for bulk materials were observed via powder X-ray diffraction. Overall, cocrystalline forms with 4,4'-bpe were more stable than the related single-component systems and were related to the relative stability of the individual conformers to γ radiation. Fluorescence signals were maintained for trans-stilbene and 4,4'-bpe, but quenching of the signal was observed for the cocrystalline forms to varying degrees. Three of the single components, 1,2-diiodotetrafluorobenzene (1,2-C6I2F4 ), 1,4-diiodotetrafluorobenzene (1,4-C6I2F4 ), and 1,4-dibromotetrafluorobenzene (1,4-C6Br2F4 ), also underwent sublimation within an hour of exposure to air postirradiation. Further analysis using differential scanning calorimetry (DSC) and Raman spectroscopy attributed this phenomenon to removal of impurities adsorbed to the crystal surface during irradiation.

Covalent Organic Frameworks for Capacitive Energy Storage: Recent Progress and Technological Challenges

AbstractCovalent‐organic frameworks (COFs) are emerging organic crystalline materials with a porous framework that extends into two or three dimensions. Originating from their versatile and rigorous synthesis conditions, COFs have abundant and tunable pores, large and easily accessible surfaces, and plenty of redox‐active sites, making them promising material candidates for various energy storage applications. One important area is to serve as capacitive electrode materials in supercapacitors. This review provides a timely and comprehensive summary of the recent progress in the design and synthesis of COF‐based or COF‐derived materials for capacitive energy storage applications. The review starts with a brief introduction to COFs’ structural features and synthesis methods. Next, recently reported literature is categorized and introduced following their different energy storage mechanisms and material assembly or treatment approaches. Finally, the existing challenges and future directions for realizing practical COF‐based supercapacitors are discussed.