Crystal Packing Modes Research Articles

Synthesis, biological activity, X-ray crystallographic, DFT calculations and molecular dynamics simulation studies of 2-phenylthiazole-1,3,5-triazine derivatives as potential cholinesterase inhibitors

Seven 2-phenylthiazole-1,3,5-triazine derivatives were synthesized and estimated for cholinesterase inhibitory activity. All target compounds were characterized by 1H NMR, 13C NMR, FT-IR, and HRMS, and their purity was tested by HPLC to be above 99%. The in vitro enzyme inhibitory activity assays determined that the majority of compounds exhibited moderate to good inhibitory effects on acetylcholinesterase or butyrylcholinesterase and compound 6g displayed the best acetylcholinesterase (IC50 = 0.26 μM) and butyrylcholinesterase inhibitory activity (IC50 = 0.78 μM). The structures of compounds 6a and 6g was further investigated by single-crystal X-ray diffraction, and the Hirshfeld surfaces, crystal voids, and molecular energy framework analysis were further discussed to study the molecular conformations, crystal packing modes, intermolecular interactions, and their energies. What's more, the density functional theory calculations including frontier molecular orbitals, global reactivity descriptors, and molecular electrostatic potential were carried out to reveal the chemical reactivity and stability of 6a and 6g molecules. Molecular docking study indicated that compound 6g could not only interact with acetylcholinesterase but also with butyrylcholinesterase. Molecular dynamics simulations study showed that compound 6g could bind to acetylcholinesterase stably. In addition, ADMET properties prediction implied the drug-like properties and safety of seven compounds. Considering these results, several of the target compounds could work as novel cholinesterase inhibitors, and compound 6g may possess the potential to become a lead compound to develop novel anti-Alzheimer drugs.

Theoretical perspective for structural isomerism effect on photoelectric properties of organic room temperature phosphorescence molecules

Purely organic room temperature phosphorescence (RTP) materials have garnered extensive attentions in anti-counterfeiting and encryption, information display, biological imaging and organic light emitting diodes (OLEDs) due to the features of long lifetimes, low toxicity and good biocompatibility. Nevertheless, both the species and amounts of the efficient RTP molecules are far from meeting the requirements for practical applications, and the quantitative relationship between molecular structures and optoelectronic properties needs full elucidated. Herein, the photophysical properties and properties of three isomers (o-BA, m-BA and p-BA) are explored based on the first-principles calculations coupled with thermal vibration correlation function (TVCF) method and kinetic Monte Carlo simulations. The substituent effects on the molecular structures, intermolecular interactions, transition properties, Huang-Rhys factors and reorganization energies, excited state dynamics as well as transfer integrals and charge carrier mobilities are investigated in detail to clarify the structure-property relationships. Results show that o-BA achieves fast radiative rate on account of impressive transition dipole moment and oscillator strength, but equally large non-radiative decay rate leads to low RTP efficiency. Promisingly, the highest holes mobility is determined for o-BA due to the largest transfer integrals of holes originating from the strong intermolecular interactions. In addition, compared with o-BA and p-BA, m-BA could achieve fast intersystem crossing (ISC) rate with large spin orbit coupling constant and low non-radiative decay rate with small geometric structure changes. Relatively balanced holes and electrons mobilities of m-BA have been demonstrated, which contributes to the recombination of excitons and the improvement of luminescence efficiency. For p-BA, the strong intermolecular hydrogen bonding restricts the free rotation of single bonds and promotes the molecular coplanarity, which contributes to efficient emission. Furthermore, the charge mobility is calculated and the temperature dependence is investigated, the hopping mechanisms for studied isomers are illustrated. This work reveals the relationship among molecular structures, crystal packing modes, photophysical properties and charge transport properties of isomers, and provides an insight for molecular design and property prediction.

Ultralow-loss Optical Waveguides through Balancing Deep-Blue TADF and Orange Room Temperature Phosphorescence in Hybrid Antimony Halide Microstructures.

Harnessing the potential of thermally activated delayed fluorescence (TADF) and room temperature phosphorescence (RTP) is crucial for developing light-emitting diodes (LEDs), lasers, sensors, and many others. However, effective strategies in this domain are still relatively scarce. This study presents a new approach to achieving highly efficient deep-blue TADF (with a PLQY of 25 %) and low-energy orange RTP (with a PLQY of 90 %) through the fabrication of lead-free hybrid halides. This new class of monomeric and dimeric 0D antimony halides can be facilely synthesized using a bottom-up solution process, requiring only a few seconds to minutes, which offer exceptional stability and nontoxicity. By leveraging the highly adaptable molecular arrangement and crystal packing modes, the hybrid antimony halides demonstrate the ability to self-assemble into regular 1D microrod and 2D microplate morphologies. This self-assembly is facilitated by multiple non-covalent interactions between the inorganic cores and organic shells. Notably, these microstructures exhibit outstanding polarized luminescence and function as low-dimensional optical waveguides with remarkably low optical-loss coefficients. Therefore, this work not only presents a pioneering demonstration of deep-blue TADF in hybrid antimony halides, but also introduces 1D and 2D micro/nanostructures that hold promising potential for applications in white LEDs and low-dimensional photonic systems.

Ultralow‐loss Optical Waveguides through Balancing Deep‐Blue TADF and Orange Room Temperature Phosphorescence in Hybrid Antimony Halide Microstructures

AbstractHarnessing the potential of thermally activated delayed fluorescence (TADF) and room temperature phosphorescence (RTP) is crucial for developing light‐emitting diodes (LEDs), lasers, sensors, and many others. However, effective strategies in this domain are still relatively scarce. This study presents a new approach to achieving highly efficient deep‐blue TADF (with a PLQY of 25 %) and low‐energy orange RTP (with a PLQY of 90 %) through the fabrication of lead‐free hybrid halides. This new class of monomeric and dimeric 0D antimony halides can be facilely synthesized using a bottom‐up solution process, requiring only a few seconds to minutes, which offer exceptional stability and nontoxicity. By leveraging the highly adaptable molecular arrangement and crystal packing modes, the hybrid antimony halides demonstrate the ability to self‐assemble into regular 1D microrod and 2D microplate morphologies. This self‐assembly is facilitated by multiple non‐covalent interactions between the inorganic cores and organic shells. Notably, these microstructures exhibit outstanding polarized luminescence and function as low‐dimensional optical waveguides with remarkably low optical‐loss coefficients. Therefore, this work not only presents a pioneering demonstration of deep‐blue TADF in hybrid antimony halides, but also introduces 1D and 2D micro/nanostructures that hold promising potential for applications in white LEDs and low‐dimensional photonic systems.

Dibenzo [a, g] corannulene-phenoxazine dyads: Facile synthesis and optoelectronic properties

Corannulene has a peculiar topology, while phenoxazine (PXZ) features extraordinary optoelectronic properties. In this study, two dibenzo [a, g] corannulene-phenoxazine dyads, BBC-C-PXZ and BBC-N-PXZ, connected via C–C and C–N bonds, respectively, were successfully prepared using PXZ as an electron donor and dibenzo [a, g] corannulene (BBC) as an electron acceptor. Photoelectrical properties of the compounds were studied using UV–vis absorption, luminescence spectroscopy, electrochemical tests and theoretical calculations. Both dyads showed Curve-Twist intramolecular charge transfer (C-TICT) in solution and aggregated state, which could be explained by the BBC-C-PXZ concave-convex crystal packing mode. They further exhibited moderate to good singlet oxygen quantum yields, the BBC-N-PXZ was 42.3% in toluene and BBC-C-PXZ was only 14.3% in n-hexane. The BBC-N-PXZ (connected by the C–N bond) exhibited contrasting reversible and anti-fatigue “turn-on” mechanochromic behavior, which displayed a blue shift under external stimulation, while the BBC-C-PXZ (linked by the C–C bond) did not exhibit this phenomenon. Analyses of the D-A (donor-acceptor) dyad systems revealed that the introduction of curved polycyclic aromatic hydrocarbons and diversified linkage positions result in unique optical and electrical properties of materials, and it provides new advances and breakthroughs in the design of organic electronic materials.

Tri(N-carbazolyl)phosphine Gold(I) Complexes: Structural and Catalytic Activity Studies.

Twelve tri(N-carbazolyl)phosphine gold(I) complexes, bearing both protonated and deuterated aryl phosphorous triamide-type ligands, have been synthesized and characterized. An elusive Au-H(D) interaction between the H(D) atoms of the tri(N-carbazolyl)phosphine ligand at the H-1(D-1) position of the carbazolyl ring and the central gold atom was observed. Complexes 5(H)/5(D) bearing the dibrominated tri(N-carbazolyl)phosphine ligand exhibit isotopic polymorphism, in which two dramatically different crystal-packing modes between the protonated and deuterated forms occur. The catalytic potential of these complexes has been showcased in the gold(I)-catalyzed glycosylation with glycosyl o-alkynylbenzoates as donors, with TON being up to 27 000.

A new strategy to design isostructural salts: The case of the antitumor drug dimethylaminomicheliolide

Isostructural multicomponent crystals provide a promising way for fine-tuning physicochemical properties, whereas their design remains quite challenging. The purpose of this work was to provide a new strategy for obtaining isostructural multicomponent crystals by introducing coformers with functional group positional isomerism. Five isostructural salts of an antitumor drug dimethylaminomicheliolide (DMAMCL) were reported and designed with a series of dihydroxybenzoic acid regioisomers for the first time, which were identified by power and single-crystal X-ray diffractions. Similar lattice parameters suggested these obtained salts may have the same crystal packing mode. The quantitative similarity parameters via XPac, CrystalCMP and Mercury program further proved these crystal structures are 3D isostructural. Hirshfeld surface maps and 2D fingerprint plots show that the isostructural salts have similar intermolecular interactions. Compared with DMAMCL, obvious improvement was observed in the thermal stability, hygroscopicity, and solubility of these isostructural salts. Meanwhile, isostructural crystals may have different physicochemical properties, even though the shape and molecular size are similar and the packing of crystal structures is equally matched.

High performance ambipolar semiconductor of pyridine-capped diketopyrrolopyrrole-porphyrin oligomers: Roles of thiophen substitution and oligomer length

Series of seven donor-acceptor pyridine-capped diketopyrrolopyrrole − 5,15-diacetylenyl-10,20-diaryl-porphyrinato zinc oligomers nPyDPP-PAr [n = 1–3, Ar = methyl-benzothiophene (BT) or methyl thiophene (T) or methylbenzene (B)] were designed. Density functional theory calculations were performed to theoretically study the molecular geometry, electronic structure, and charge transport properties of the seven donor-acceptor compounds. The effects of oligomer length and different Ar groups on the crystal packing mode and charge transport properties were systematically studied. Thiophen substitution reduces the electron injection barrier, diminishes the reorganization energy, enlarges the charge transfer integral, and therefore shows three-to-one role for ambipolar semiconductor with large charge transfer mobility. Extending the π-conjugated backbone not only improves the semiconductor performance, but also makes the ambipolar performance more balanced. 3PyDPP-PT and 3PyDPP-PBT show high hole/electron transfer mobility as high as 8.28/7.90 cm2 V−1 s−1 and 9.00/9.79 cm2 V−1 s−1, respectively.

Machine Learning-Assisted High-Throughput Virtual Screening for On-Demand Customization of Advanced Energetic Materials

Finding energetic materials with tailored properties is always a significant challenge due to low research efficiency in trial and error. Herein, a methodology combining domain knowledge, a machine learning algorithm, and experiments is presented for accelerating the discovery of novel energetic materials. A high-throughput virtual screening (HTVS) system integrating on-demand molecular generation and machine learning models covering the prediction of molecular properties and crystal packing mode scoring is established. With the proposed HTVS system, candidate molecules with promising properties and a desirable crystal packing mode are rapidly targeted from the generated molecular space containing 25 112 molecules. Furthermore, a study of the crystal structure and properties shows that the good comprehensive performances of the target molecule are in agreement with the predicted results, thus verifying the effectiveness of the proposed methodology. This work demonstrates a new research paradigm for discovering novel energetic materials and can be extended to other organic materials without manifest obstacles.

Accurate Analysis of Anisotropic Carrier Mobility and Structure-property Relationships in Organic BOXD Crystalline Materials.

Charge mobility is an essential factor of organic crystalline materials. Although many investigators have made important progress, the exact relationship between the crystal structure and carrier mobility remains to be clarified. Fortunately, a series of bis-1,3,4-oxadiazole derivatives have been successfully prepared and reported. They have similar main molecular fragments but different crystal packing modes, which provide an ideal research objective for studying the effect of molecular packing on charge mobility in organic photoelectric conversion systems. In this work, the charge mobilities of these molecules are systematically evaluated from the perspective of first-principles calculation, and the effect of a molecular overlap on orbital overlap integral and final charge carrier mobility is fully discussed. It can be seen that the small intermolecular distance (less than 6 Å) is the decisive factor to achieve high electron mobility in π stacking, and better mobility can be obtained by increasing the hole migration distance appropriately. A larger dihedral angle of anisotropy is an important point limiting the charge mobility in the herringbone arrangement. It is hoped that the correlation results between the crystal structure and mobility can assist the experimental study and provide an effective way to improve the photoelectric conversion efficiency of the organic semiconductor devices and multiple basis for multiscale material system characterization and material information.

Crystal structures reveal a novel dimer of the RWD domain of human general control nonderepressible 2

General control nonderepressible 2 (GCN2) is a serine/threonine protein kinase, detecting a variety of stresses including amino acid starvation, reactive oxygen species, etc. in eukaryotic cells. Activation of GCN2 requires the interaction of the N-terminal RWD domain with the upstream GCN1 protein and the dimerization by the kinase domain. In this study, we determined two crystal structures of the RWD domain of human GCN2 in two different crystal packing modes. These two different crystal structures reveal a same dimer of the RWD domain, which has not been reported in previous studies. We further confirmed this novel dimer interaction in solution using gel filtration experiments, and in human embryonic kidney (HEK) 293 cells using bimolecular fluorescence complementation (BiFC) and co-immunoprecipitation (co-IP) assays. Together, this study discovers a potential protein-protein interface on the RWD domain of human GCN2, and suggests a possible regulation between the interaction of GCN1 and the formation of GCN2 dimer.

Tuning morphology of sulfadiazine through phase transformation of two novel solvates

Two new solvates of the widely used antibiotic sulfadiazine were found and fully characterized. The crystal structures of these two solvates were determined. Differences between various sulfadiazine forms were elucidated by analyzing intermolecular interactions, crystal packing modes and molecule conformations. In addition, the phase transformations between solvates and solvent-free form were investigated. The sulfadiazine solvates quickly transformed into solvent-free form in water. The obtained particles were aggregates but with well-defined shape. They maintained the morphology and size of the solvate crystals. The results indicated that solvates can be used as intermediates to regulate the morphology of solvent-free form product through rapid solvent-mediated phase transformation.

Crystal-packing modes determine the solid-state ESIPT fluorescence in highly dipolar 2′-hydroxychalcones

Fifteen easily assembled ESIPT-active 2′-hydroxychalcones were prepared to identify deep-red crystal-state fluorophores with increased quantum yields. Systematic single-crystal XRD analysis furnished trends in the structure–property relationship.

Synthesis and structure of regioisomeric amino enones containing 2-pyridyl and CF3 substituents

Regioisomeric amino enones (Z)-4-amino-1,1,1-trifluoro-4-(2-pyridyl)but-3-en-2-one and (Z)-3-amino-4,4,4-trifluoro-1-(2-pyridyl)but-2-en-1-one were synthesized by the reaction of lithium (Z)-1,1,1-trifluoro-4-oxo-4-(2-pyridyl)but-2-en-2-olate with ammonium acetate in glacial AcOH. A comparative study of physicochemical properties and the crystal structures showed that the molecules of these new compounds are planar (except for two fluorine atoms) with an U-shaped configuration of the keto enamine moiety. A change in the position of the amino group with respect to the CF3 substituent leads to significant changes in the electron density distribution and the C-C bond lengths in the keto enamine moiety and also in the character of intermolecular hydrogen bonds responsible for the crystal packing mode of regioisomeric amino enones.

Synthesis, characterization, and crystal structure analysis of group IIB coordination compounds containing N,N′-bidentate chelating Schiff-base ligand

The solid-state chemistry of coordination complexes has become an actively developing research area of modern inorganic chemistry. Herein, Zn and Hg coordination compounds containing a N,N′-bidentate chelating Schiff-base ligand were synthesized and then characterized using spectroscopic techniques and single-crystal X-ray crystallography. The molecular structures and crystal packing modes of these complexes, as well as the crystal structures of related compounds, were investigated thoroughly using geometrical and Hirshfeld surface analyses, as well as theoretical calculations. It has been revealed that the supramolecular architecture of these series of coordination complexes is governed mainly by a combination of chelate···π and π···π stacking, and non-classical hydrogen bonding interactions. This study provides further insight into the understanding of the coordination chemistry of group IIB complexes containing Schiff-base ligand and the role of weak non-covalent interactions in the solid-state structure of coordination compounds.

Analysis of intermolecular interactions in homologous molecular crystals of energetic materials

Crystal packing modes determine the energy and safety performance of energetic materials (EMs) to some extent. To deepen the understanding of the intermolecular interactions in the crystal packings, the homologous molecular crystals of energetic materials were first defined according to the packing similarities in this study, and four groups of energetic homologous crystals with the same packing structures were found from the large experimentally available data. Several computational approaches were employed to comparatively probe the intermolecular interactions at molecular and crystal levels. The results of the analysis show that the common organic skeleton of two molecular conformations in each homologous packing structure remains the same or becomes mirror-symmetrical with a minor variation of functional groups, resulting in the local change of molecular electrostatic potentials, while the overall distribution of electrostatic potentials can be largely maintained. Compared with the other groups of homologous crystals, interestingly, the differences in intermolecular interactions in Group 4 are relatively large according to two-dimensional fingerprint plots and energy frameworks, indicating that the crystal packing of energetic materials is predominately caused by some types of intermolecular interactions. The results reported here are expected to inspire the constructions of energetic crystals with specific packing modes to improve performances, such as a minor modification to the molecular structure while keeping original crystal packing style. The homologous molecular crystals in energetic materials were first proposed based on the packing similarities to comparatively explore the intermolecular interactions in the same packing structures, with the goal of improving the understanding of crystal construction of energetic materials with specific packing modes.

Bulky Phenylalkyl Substitutions to Bisthienoisatins and Thienoisoindigos

In order to investigate the effects of bulky substituents on the crystal structures and packing modes, N-benzyl (Bn) and N-2-phenylethyl (EtPh) substituents are introduced in bisthienoisatin (BTI),...

Two‐Coordinate Copper(I)/NHC Complexes: Dual Emission Properties and Ultralong Room‐Temperature Phosphorescence

AbstractAs a kind of photoluminescent material, CuI complexes have many advantages such as adjustable emission, variable structures, and low cost, attracting attention in many fields. In this work, two novel two‐coordinate CuI‐N‐heterocyclic carbene complexes were synthesized, and they exhibit unique dual emission properties, fluorescence and phosphorescence. The crystal structure, packing mode, and photophysical properties under different conditions were systematically studied, proving the emissive mechanism to be the locally excited state of the carbazole group. Based on this mechanism, ultralong room‐temperature phosphorescence (RTP) with a lifetime of 140 ms is achieved by selective deuteration of the carbazole group. These results deepen the understanding of the luminescence mechanism and design strategy for two‐coordinate CuI complexes, and prove their potential in applications as ultralong RTP materials.

Two-Coordinate Copper(I)/NHC Complexes: Dual Emission Properties and Ultralong Room-Temperature Phosphorescence.

As a kind of photoluminescent material, CuI complexes have many advantages such as adjustable emission, variable structures, and low cost, attracting attention in many fields. In this work, two novel two-coordinate CuI -N-heterocyclic carbene complexes were synthesized, and they exhibit unique dual emission properties, fluorescence and phosphorescence. The crystal structure, packing mode, and photophysical properties under different conditions were systematically studied, proving the emissive mechanism to be the locally excited state of the carbazole group. Based on this mechanism, ultralong room-temperature phosphorescence (RTP) with a lifetime of 140 ms is achieved by selective deuteration of the carbazole group. These results deepen the understanding of the luminescence mechanism and design strategy for two-coordinate CuI complexes, and prove their potential in applications as ultralong RTP materials.

Effect of Carbazolyl Groups on Photophysical Properties of Cyanuric Chloride.

Long-lived room temperature organic phosphorescence is highly useful in biological imaging, electroluminescent devices, information security, and security protection on account of its unique photophysical process and long-lived luminescence. In recent years, pure organic phosphorescent materials that do not contain rare precious metals have received increasing attention. Carbazole and its derivatives have been used to develop room temperature organic phosphorescent materials. However, the effect of carbazolyl groups on the photophysical properties of pure organic phosphors has rarely been reported. In this work, three cyanuric chloride phosphors (CzDCIT, BiCzDT, and TCzT) modified with different numbers of carbazolyl groups were synthesized. Several characterization techniques were employed to reveal distinct crystal forms of CzDCIT, BiCzDT, and TCzT. The single crystal diffraction of CzDCIT and BiCzDT showed not only different crystal packing modes, but also the formation of internal H-aggregation. These three phosphor powders exhibited dual emissions of blue fluorescence and yellow phosphorescence at room temperature, with luminescence lifetimes of 0.16-0.34 s. Theoretical calculations indicated that different numbers of effective intersystem crossing channels between CzDCIT, BiCzDT, or TCzT were responsible for the luminescence lifetimes. After doping the phosphors into the polymer matrix, they exhibited good persistent phosphorescence and high recoverability in multiple compression-grinding cycles.