Packing Arrangement Research Articles

Sergeant-and-Soldier Effect in an Organic Room-Temperature Phosphorescent Host-Guest System.

Host-guest systems have emerged as an efficient strategy for promoting organic room temperature phosphorescence (RTP). Despite the advantages of doping guest molecules into a host matrix, the complexity of these systems and the lack of techniques to visualize host-guest interactions at the molecular scale pose significant challenges in understanding the underlying mechanisms. Here, a novel host-guest RTP system is developed by incorporating low concentrations (1-10 mol%) of TPP-4C-BI (guest) into crystalline TPP-4C-Cz (host). Utilizing structural isomerism, the guest molecules are regularly incorporated into the host crystal lattice, resulting in phosphorescence quantum yields almost ten times higher than the pure compounds. The system enabled resolution of the molecular packing of the single crystal through X-ray diffraction, providing unprecedented visualization of host-guest interactions. A "sergeant-and-soldier" effect, where the minority dopant molecules (sergeants) significantly influence the packing arrangement of the host molecules (soldiers), enhances RTP is identified. Further analyses revealed that due to the host molecule's inefficient phosphorescence pathway, its long-lived dark triplets are channeled to the guest via triplet-triplet energy transfer (TTET), allowing the excited energy to radiatively decay more efficiently. These insights advance the understanding of RTP mechanisms and offer practical implications for designing high-efficiency phosphorescent materials.

Controllable 1,4-Palladium Aryl to Aryl Migration in Fused Systems─Application to the Synthesis of Azaborole Multihelicenes.

Herein, we report the first 1,4-Pd aryl to aryl migration/Miyaura borylation tandem reaction in fused systems. The Pd shift occurred in the bay region of the dibenzo[g,p]chrysene building blocks, giving rise to a thermodynamically controlled mixture of 1,8- and 1,9-borylated compounds that allowed the preparation of regioisomeric azaborole multihelicenes from the same starting material. The outcome of this synthesis can be controlled by the choice of reaction conditions, allowing the migration process to be turned off in the absence of an acetate additive and the target multiheterohelicenes to be prepared in a regioselective manner. The target compounds show bright green fluorescence in dichloromethane with emission quantum yields (Φ) of up to 0.29, |glum| values up to 2.7 × 10-3, and green or green-yellow emission in the solid state, reaching Φ of 0.22. Single crystal X-ray diffraction analyses gave insight into their molecular structures and the packing arrangement. Evaluation of aromaticity in these multihelicenes revealed a nonaromatic character of the 2H-1,2-azaborole constituent rings.

NNN type pincer Pd (II) complexes of pyridine-2,6-dicarboxamides: Catalytic activity and supramolecular formation

Pyridine-2,6-dicarboxamide, NNN pincer type pro-ligands, and their palladium complexes were synthesized. The prepared pro-ligands and complexes were characterized with several characterization techniques (FT-IR, 1H NMR, 13C NMR, and UV-vis analyses). The molecular structure of the acetonitrile-N2,N6-bis(2-bromophenyl)pyridine-2,6-dicarboxamidopalladium(II) complex has been determined by single crystal XRD measurement. This complex contains intramolecular and intermolecular H-bonds, C–H⋅⋅⋅π and face-to-face π⋅⋅⋅π interactions. In addition, two synthons were found in the crystal lattice that have been generated through hydrogen-bond interactions. Homo-synthons (R22(12)), which forms through C–H⋅⋅⋅O intermolecular interactions (2.816 Å for C15–H15⋅⋅⋅O1 and 2.603 Å for C13–H13⋅⋅⋅O2) and hetero-synthons (R21(8)), that generated via C–H⋅⋅⋅N intermolecular interactions (C21–H21C⋅⋅⋅N4, 3.439 Å). Furhermore, homo-synthons (R33(11) and R22(9)) through intermolecular contacts were determined between the palladium complex and the acetonitrile molecules. Furthermore, a quantitative analysis of the noncovalent interactions within the structure was performed using Hirshfeld surface and two-dimensional fingerprint plot analyses. The three-dimensional arrangement of the crystal packing was assessed during the energy-framework calculations, revealing that the electrostatic energy framework had a considerable influence on the dispersion energy framework. The [PdL5] complex provided a conversion of more than 98% and a yield of more than 98% in the shortest time among other catalysts, in which the Suzuki-Miyaura C-C cross-coupling reaction (SMR) was carried out with the 4-bromotoluene substrate. The activity of [PdL5] complex was then examined in the reactions of two other substrates, 1-bromo-4-isobutylbenzene and 2-bromo-6-methoxynaphthalene. Although a yield of over 97% and a conversion of over 97% were observed in the reaction of 1-bromo-4-isobutylbenzene after two hours, the reaction of 2-bromo-6-methoxynaphthalene achieved complete conversion and a yield of over 99% within just one hour.

An integrated approach combining experimental, informatics and energetic methods for solid form derisking of PF-06282999

The landscapes of observed and predicted three-dimensional crystal packing arrangements of small-molecule drug candidates can be complex. The possible appearance of a more thermodynamically stable solid form during drug development has led to the digital workflow of informatics-based risk assessments, named a Solid Form Health Check. Herein, we describe the use of a combined approach consisting of experiments, informatics together with energetic calculations in analysis of four competing polymorphs of PF-06282999, a myeloperoxidase (MPO) inhibitor with conformational flexibility and multiple plausible hydrogen bond networks. This combined approach offered a comprehensive understanding of the solid form structure, properties, and performance, ensuring robust solid form derisking and selection.

Linkage Regulation of Back‐To‐Back Connected Dimers as Guest Acceptors Enables Organic Solar Cells with Excellent Efficiency, Stability and Flexibility

AbstractHigh efficiency, stability, and flexibility are key prerequisites for the commercial applications of organic solar cells (OSCs). Herein, three back‐to‐back connected dimers (2Qx‐TT, 2Qx‐C3, 2Qx‐C6) are developed as the guest acceptors for OSCs with improved comprehensive performance. By regulating the linkage from rigid bithiophene to flexible alkyl chain, the back‐to‐back connected dimers display quite different molecular geometry and intermolecular interactions, consequently influencing their packing arrangement, film‐forming process, carrier mobilities, and the device efficiency, stability, and flexibility. By introducing these dimer acceptors as the guest into active layer, these dimers form alloy phases with the host acceptor, promoting film‐forming process and charge dynamics. All ternary devices exhibit improved PCEs of over 18% than the control binary device. Among them, 2Qx‐C3‐based ternary device obtains the best efficiency of as high as 19.03%. Moreover, thanks to the stronger entanglement favored by the dimers with flexible linkage, the PM6:BTP‐eC9:2Qx‐C3‐based device shows outstanding stability and flexibility. The flexible device displays an improved PCE of 16.09% with a crack‐onset strain of 15.0%, showing excellent mechanical robustness close to the all‐polymer devices. This work demonstrates the potential of the back‐to‐back connected dimer acceptors as the guest for highly efficient, stable and flexible OSCs.

Investigation of the crystal structure, spectral properties, and interactions of N-(R-nitrophenylsulfonamido)benzoic acids with human serum albumin

This study introduced the synthesis of two novel compounds in the N-(R-nitrophenylsulfonamido)benzoic acids (NO2-SBA), designated as HL6 and HL8. Detailed structural information for HL6 and HL8 was acquired through the employment of various characterization techniques such as single-crystal and powder X-ray diffraction, FT-IR spectroscopy, 1H and 13C NMR spectroscopy, and elemental analysis. X-ray diffraction and Hirshfield surface analysis provides a comparative analysis of hydrogen bonding in HL6·H2O and HL8, revealing significant differences in their interaction patterns and resulting crystal structures. Although both molecules possess the same number of hydrogen bond donors and acceptors, the nature of these interactions and their orientations lead to distinct packing arrangements. In HL6·H₂O, the presence of water molecules introduces additional hydrogen bonding possibilities, which are absent in HL8, significantly affecting the overall structure. Additionally, interactions of all nine compounds in the NO2-SBA series [categorized as o-ABA: HL1–HL3, m-ABA: HL4–HL6, and p-ABA: HL7–HL9] with human serum albumin (HSA) were investigated to understand how structural characteristics influence binding mechanisms and affinity. Fluorescence spectroscopy was employed to further examine these interactions, providing a better understanding of their pharmacological properties. The compounds exhibited moderate affinity to HSA, with the o-ABA series displaying a binding constant (Kb) ten times stronger than the other series, underscoring the significant role of the N,R groups in binding interactions.

The role of adsorbent microstructure and its packing arrangement in optimising the performance of an adsorption column

Physical adsorption takes place inside narrow pores where the attractive interaction between the surface of the adsorbent and the contaminant molecules is strong enough to retain the molecules. Adsorption columns involve a range of mass-transport mechanisms: advection through the free spaces between the adsorbent pellets, diffusion through the macro/mesopores of the adsorbent, and adsorption at the surface, where the micropores exist. The adsorbent specifications along with its assembly within the sorption column are key factors when optimizing the filtration of pollutants. In this work we present a mathematical model based on advection–diffusion equations coupled with Langmuir kinetics that accounts for a geometrical approach to the porosity structure inside the adsorbent, formed by a radial lattice of cylinders, and the channels through which the fluid flows surrounding the cylindrical pellets. The model is tested using typical lab-scale values based on VOC adsorption, and we use it to identify optimal macro/mesopore size and column porosity for energetic considerations.

Investigation on particle size and packing tortuosity by coupling image analysis and permeability tests

This experimental study aims to enhance the understanding of the correlation among equivalent particle diameters measured using two analytical techniques: optical analysis (assisted by computer aided image analysis) and permeability tests. The presence or absence of a specific analytical method or instrument can lead to the use of an incorrect equivalent diameter. Therefore, it can be beneficial to establish conversion rules between different equivalent particle diameters obtained through various methods and instruments. The optical analysis returns an equivalent diameter value inherently independent of particle arrangement since it deals with isolated particles. In contrast, the permeability test offers an equivalent mean diameter dependent not only on the size of the particles but also on their packed arrangement. A suitable correlation between the two diameters has been proposed, shown to be a decreasing function of porosity following a power law.An unexpected outcome of the comparison between the optical method and permeametry is the possibility to isolate and characterize the effect that the packing arrangement has on pressure losses and to characterize it in terms of the tortuosity of the path that the fluid must travel through the packed bed. Our findings confirm a strong alignment between our tortuosity model, which contains the ratio between the two equivalent diameters considered here, and an empirical correlation from literature often utilized for predicting packed bed tortuosity.

Adsorptive removal of a nitrate ion from the aqueous solution of sodium nitrate by application of double fixed-bed column

This study focuses on the removal of nitrate ions from aqueous solutions using rice husk activated carbon (RHAC). The RHAC was subjected to characterization via Fourier transform infrared (FTIR), scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS), and X-ray florescence (XRF) to ascertain its functional groups, surface morphology, and oxide/elemental composition, respectively. Batch experiments were conducted to assess the impact of nitrate concentration, bed height, and number of packing layers on removal efficiency. FTIR spectra revealed favorable sorption-related functional groups within RHAC, while SEM analysis indicated the presence of effective sorption sites on its surface. EDS analysis of the rice husk adsorbent before adsorption (RHBS) demonstrated a significant composition of Si (42.20%), O (35.30%), and Ca (12.33%). The batch study unveiled a concentration-dependent decrease in nitrate removal efficiency, alongside the enhanced performance with increased bed height and number of packing layers. Kinetic data fitting favored the Yoon–Nelson and Adams–Bohart models. Overall, RHAC exhibited efficient nitrate ion removal, with column performance notably improved by utilizing multiple packing layers. These results will enhance our understanding of the mechanisms involved in removing nitrate ions and highlight the potential effectiveness of RHAC, especially when utilized with multiple packing arrangements in column setups.

Dynamic and solid-state behaviour of bromoisotrianglimine.

Solid-state materials formed from discrete imine macrocycles have potential in industrial separations, but dynamic behaviour during both synthesis and crystallisation makes them challenging to exploit. Here, we explore opportunities for structural control by investigating the dynamic nature of a C-5 brominated isotrianglimine in solution and under crystallisation conditions. In solution, the equilibrium between the [3 + 3] and the less reported [2 + 2] macrocycle was investigated, and both macrocycles were fully characterised. Solvent templating during crystallisation was used to form new packing motifs for the [3 + 3] macrocycle and a previously unreported [4 + 4] macrocycle. Finally, chiral self-sorting was used to demonstrate how crystallisation conditions can not only influence packing arrangements but also shift the macrocycle equilibrium to yield new structures. This work thus exemplifies three strategies for exploiting dynamic behaviour to form isotrianglimine materials, and highlights the importance of understanding the dynamic behaviour of a system when designing and crystallising functional materials formed using dynamic covalent chemistry.

AIE active blue light emitting pyridine functionalized quinoxaline and pyridopyrazine derivatives exhibiting reversible acidofluorochromism and thermal sensitivity

This work presents a systematic study of five novel closely related pyridine-substituted quinoxaline and pyridopyrazine derivatives 3a-e. Modifying the quinoxaline framework by introducing electron donating and accepting units led to fine-tuning of optical, thermal, and electrochemical properties. The single crystal X-ray diffraction studies revealed a Y-shaped structure with a herringbone packing arrangement. These compounds showed aggregation-induced emission (AIE) with the formation of J-aggregates. These compounds emitted blue fluorescence with one of the compounds showing CIEy as low as 0.08 in CHCl3 and 0.09 in the solid state. The band gaps were evaluated using UV-visible spectroscopy and density functional theory (DFT). The optical band gaps in the solid state were in the 2.81–3.05 eV range. They exhibited reversible switching of emission properties upon treatment with trifluoroacetic acid (TFA) followed by triethylamine (TEA) in both solution and solid states, which was utilized to fabricate filter paper strips to detect volatile acids. The emission of compounds also displayed linear temperature dependence.

Rational Control of Packing Arrangements in Organic Semiconducting Materials toward High-Performance Optoelectronics

Rational Control of Packing Arrangements in Organic Semiconducting Materials toward High-Performance Optoelectronics

Molecular Orientation-Dependent Photonic Polarization Engineering in Organic Single-Crystal-Filled Microcavities.

Designing the polarization degree of freedom of light is crucial in many fields and has widespread application in, for example, all-optical circuits. In this work, we find that in an organic microcavity filled with anisotropic single crystals the cavity modes can be modulated to be elliptically polarized, i.e., partially circularly polarized and partially linearly polarized. The circular polarization component originates from the Rashba-Dresselhaus spin splitting, while the linear polarization component is due to the dislocation of linearly polarized modes. The dislocation of the linear polarizations is ascribed to the orientation of individual molecules and the molecular packing arrangement; hence, the linear polarizations can be controlled by properly structuring the molecular distributions. Our results pave the way for enriching and engineering the polarization properties of individual optical cavity modes in organic microstructures, which may favor the development of polarized lasers with various polarizations.

Unprecedented Packing Polymorphism of Oxindole: An Exploration Inspired by Crystal Structure Prediction.

Crystal polymorphism, characterized by different packing arrangements of the same compound, strongly ties to the physical properties of a molecule. Determining the polymorphic landscape is complex and time-consuming, with the number of experimentally observed polymorphs varying widely from molecule to molecule. Furthermore, disappearing polymorphs, the phenomenon whereby experimentally observed forms cannot be reproduced, pose a significant challenge for the pharmaceutical industry. Herein, we focused on oxindole (OX), a small rigid molecule with four known polymorphs, including a reported disappearing form. Using crystal structure prediction (CSP), we assessed OX solid-state landscape and thermodynamic stability by comparing predicted structures with experimentally known forms. We then performed melt and solution crystallization in bulk and nanoconfinement to validate our predictions. These experiments successfully reproduced the known forms and led to the discovery of four novel polymorphs. Our approach provided insights into reconstructing disappearing polymorphs and building more comprehensive polymorph landscapes. These results also establish a new record of packing polymorphism for rigid molecules.

Unprecedented Packing Polymorphism of Oxindole: An Exploration Inspired by Crystal Structure Prediction

AbstractCrystal polymorphism, characterized by different packing arrangements of the same compound, strongly ties to the physical properties of a molecule. Determining the polymorphic landscape is complex and time‐consuming, with the number of experimentally observed polymorphs varying widely from molecule to molecule. Furthermore, disappearing polymorphs, the phenomenon whereby experimentally observed forms cannot be reproduced, pose a significant challenge for the pharmaceutical industry. Herein, we focused on oxindole (OX), a small rigid molecule with four known polymorphs, including a reported disappearing form. Using crystal structure prediction (CSP), we assessed OX solid‐state landscape and thermodynamic stability by comparing predicted structures with experimentally known forms. We then performed melt and solution crystallization in bulk and nanoconfinement to validate our predictions. These experiments successfully reproduced the known forms and led to the discovery of four novel polymorphs. Our approach provided insights into reconstructing disappearing polymorphs and building more comprehensive polymorph landscapes. These results also establish a new record of packing polymorphism for rigid molecules.

In vivo imaging of human retinal ganglion cells using optical coherence tomography without adaptive optics.

Retinal ganglion cells play an important role in human vision, and their degeneration results in glaucoma and other neurodegenerative diseases. Imaging these cells in the living human retina can greatly improve the diagnosis and treatment of glaucoma. However, owing to their translucent soma and tight packing arrangement within the ganglion cell layer (GCL), successful imaging has only been achieved with sophisticated research-grade adaptive optics (AO) systems. For the first time we demonstrate that GCL somas can be resolved and cell morphology can be quantified using non-AO optical coherence tomography (OCT) devices with optimal parameter configuration and post-processing.

Theoretical optimization of bed packing arrangement in cascade Dual-Catalyst system with side reactions

The performance of cascade dual-catalyst systems is highly related to the catalysts spatial arrangement within the bed layers. However, optimization tools for the cascade dual-catalyst layer arrangements are still in need of development. In this study, an optimization framework based on genetic algorithms (GA) and artificial neural networks (ANN) is developed for optimization while explore effects of side reaction on optimized arrangement. Further, a new descriptor as known as delta switch (DS) is introduced. Isolated analysis of the effects of the two types of side reactions shows that the solely side reaction on S0 results in a repeated S0-S1-S0 structure, while the introduce of side reactions on S1 disrupts this structural regularity and reduces the optimal length of the bed layer. Based on DS patterns, a simplified cascade dual-catalysts spatial optimization framework (≤3 layers) is employed, achieving ≥ 95 % performance of original GA.

Guest-Induced Conformational Transformations in Tiara[5]arene Crystals: A Pathway for Molecular Sieving.

In pursuit of environmental sustainability and energy efficiency, assorted macrocyclic compounds have recently emerged as crystalline adsorbents for the efficient molecular sieving of various chemical commodities. Herein, we delve into the conformational characteristics and solid-state packing modes of tiara[5]arenes (T[5]), a rim-differentiated pillar[5]arene derivative. By meticulously exploring the conformational space, we have successfully identified a multitude of distinct T[5] conformers within a relatively narrow energy range of 22 kJ/mol. This finding underscores the inherent conformational flexibility of this macrocyclic scaffold, enabling T[5] to adapt diverse packing arrangements in the solid state. While solvent-free T[5] crystals do not exhibit permanent porosity, they undergo solvomorphic interconversions when exposed to various guest compounds. Our study demonstrates that T[5]-based crystalline materials exhibit a notable preference for selectively capturing aromatic and olefinic solvents, such as benzene, toluene, chlorobenzene, and cyclohexene, over their aliphatic hydrocarbon counterparts from equivalent volume liquid mixtures, achieving up to 10:1 selectivity between benzene and cyclohexane.

Unveiling the molecular insights of 2-(carboxymethyl) benzoic acid: A density functional theory approach towards structural and biological attributes

Nowadays density functional theory (DFT) is one of the best methods to explore the vibrational modes and structure of the biological system. Quantum mechanical calculations are performed using gas phase and different solvents (DMSO, methanol and water). The derived global reactive parameters, structural and topological study provides the clear insight of the 2-(Carboxymethyl) benzoic acid. Depth studies of DFT proves the existence of hydrogen bonds between donor and acceptor in the compound, which is supportive for the biological applications. In this paper, different experimental and computational simulated FT-IR, FT-Raman, UV–Vis spectral studies are used to explicate vibration assignments of the 2-(Carboxymethyl) benzoic acid. Experimentally observed vibrational frequency is compared with theoretically simulated spectrum. B3LYP method with 6–311++G (d, p) basis set is used in DFT to optimize the 2-(Carboxymethyl)benzoic acid structure. The most stable lower energy conformer is identified using potential energy surface (PES) analysis using Gaussian 16 W software. ESP, HOMO-LUMO, NBO, and QTAIM calculations have evinced an adequate electronic characterization of 2-(Carboxymethyl) benzoic acid. Further, van der Waals and steric interactions among 2-(Carboxymethyl) benzoic acid have been discussed with the help of RDG study. Hirshfeld surface studies establish the existing various interaction among molecules and total packing arrangement of the crystal structure. Due to the high biological activity score, 2-(Carboxymethyl) benzoic acid is a good therapeutic candidate. Lipophilicity analysis of 2-(Carboxymethyl)benzoic acid clearly explicates the bioactivity properties and its effective drug applications. Further, molecular docking investigates that the compound can be used as anticancer medication. The detailed DFT study of the 2-(Carboxymethyl) benzoic acid justified its biological applications of the present communication. The calculated NLO parameters of 2-(Carboxymethyl)benzoic acid evidenced for good efficacy in diverse filed application has been discussed.

Structure of Spider Silk Studied with Solid‐State NMR

AbstractSpider dragline silks exhibit remarkable mechanical properties, combining both high strength and toughness. These unique characteristics arise from the intricate structure of the silk, which requires atomic‐level information to understand its origins. 13C solid‐state NMR provides this detailed structural insight into spider dragline silk. In this review, 13C CP/MAS, 13C DD/MAS and 13C INEPT NMR spectroscopies are employed to reveal the structure of spider dragline silks together with 13C conformation‐dependent chemical shifts, 2D spin‐diffusion NMR, rotational echo double resonance, dipolar‐assisted rotational resonance, and angle‐dependent NMR. The primary structure of major ampullate of spider dragline silk consists of repeated polyalanine and a glycine‐rich regions. By analyzing the 13C conformation‐dependent chemical shifts and utilizing several solid‐state NMR techniques, it has been proposed that the glycine‐rich region primarily adopts a random coil conformation, including partially β‐sheet and β‐turn structures. This contradicts the previously suggested 31 helix conformation. On the other hand, the polyalanine region exhibits an antiparallel β‐sheet structure with staggered packing arrangements. Additionally, solid‐state NMR has also revealed the structure of fragelliform spider silk. These findings contribute to the understanding of the remarkable properties of spider dragline silks and provide insights into its atomic‐level architecture.