Rigid Units Research Articles

Combating Fungal Infections and Resistance with a Dual-Mechanism Luminogen to Disrupt Membrane Integrity and Induce DNA Damage.

Antifungal drug resistance is a critical concern, demanding innovative therapeutic solutions. The dual-targeting mechanism of action (MoA), as an effective strategy to reduce drug resistance, has been validated in the design of antibacterial agents. However, the structural similarities between mammalian and fungal cells complicate the development of such a strategy for antifungal agents as the selectivity can be compromised. Herein, we introduce a dual-targeting strategy addressing fungal infections by selectively introducing DNA binding molecules into fungal nuclei. We incorporate rigid hydrophobic units into a DNA-binding domain to fabricate antifungal luminogens of TPY and TPZ, which exhibit enhanced membrane penetration and DNA-binding capabilities. These compounds exhibit dual-targeting MoA by depolarizing fungal membranes and inducing DNA damage, amplifying their potency against fungal pathogens with undetectable drug resistance. TPY and TPZ demonstrated robust antifungal activity in vitro and exhibited ideal therapeutic efficacy in a murine model of C. albicans-induced vaginitis. This multifaceted approach holds promise for overcoming drug resistance and advancing antifungal therapy.

Understanding secondary order parameters in perovskites with tilted octahedra

In the family of perovskite materials, the tilts of BX 6 octahedra are the most common type of structural distortion. Conventionally, the formation of low-symmetry perovskite phases with tilted octahedra is analyzed by considering only primary order parameters. However, octahedral tilting also gives rise to secondary order parameters which contribute to additional atomic displacements, ordering and lattice distortions. Our study highlights the significant impact of secondary order parameters on the structural formation and emergent physical properties of perovskites. Through group-theoretical and crystallographic analyses, we have identified all secondary order parameters within Glazer-type tilt systems and clarified their physical manifestations. We explore the fundamental symmetry relationships among various structural degrees of freedom in perovskites, including tilt-induced ferroelasticity, correlations between displacements and ordering of atoms occupying different positions, and the potential for rigid unit rotations and unconventional octahedral tilts. Particular emphasis is placed on the emergence of secondary order parameters and their coupling with primary order parameters, as well as their symmetry-based hierarchy, illustrated through a modified Bärnighausen tree. We applied our theoretical insights to elucidate phase transitions in well known perovskites such as CaTiO3 and RMnO3 (where R = La and lanthanide ions), thereby demonstrating the significant influence of secondary order parameters on crystal structure formation. Our results serve as a symmetry-based guide for the design, identification and structural characterization of perovskites with tilted octahedra, and for understanding tilt-induced physical properties.

Linker length-dependent lithium storage of pyrene-4,5,9,10-tetraone-based conjugated organic polymer cathodes

Conjugated organic polymers (COPs) have been emerged as a class of cathode materials for lithium-ion batteries (LIBs) because of the rigid structural units and tunable properties. Nonetheless, their applications are still limited due to the poor conductivity and low cycling life. Herein, we design a series of pyrene-4,5,9,10-tetraone-based COPs (P(PTODB)-1, P(PTODB)-2, P(PTODB)-3), containing different number of benzene rings as linking units. Consequently, prolonging the linker lengths could effectively improve structural stability and extend π-conjugation, leading to the enhanced charge-storage capability. When tested as cathode materials for LIBs, the P(PTODB)-2 electrode delivers a better electrochemical performance with high capacity of 203 mA h g-1 after 100 cycles at 0.1 A g-1 (coulombic efficiency almost 100%) and excellent rate performance (150 mA h g-1 at 5 A g-1). In addition, the Li+ storage mechanism was carried out by ex situ Fourier transform infrared (FT-IR) and X-ray photoelectron spectroscopy (XPS) analysis. Eventually, our study brings forward the appropriately extended linker lengths to fabricate COP cathodes with high electrochemical properties.

Synthesis and spectroscopic studies of triazole-based macroheterocycles containing eudesmane-type sesquiterpenoid moieties

Chiral recognition is one of the most important and fascinating areas in supramolecular chemistry. Chiral macrocycles, especially chiral macrocyclic hosts, having stable structures, adjustable internal cavities to encapsulate and complexation have been developed during the last decade. Attention has been paid on the synthesis of covalently linked of rigid units on the side chain of macrocycles with active binding motifs. In this study, new synthetic protocols has been developed for preparation of optically active triazole-based macrocyclic compounds in which eudesmane-type sesquiterpene lactones act as pendent moieties by the implementation of the copper(I)-catalyzed azid-alkyne cycloaddition strategies. The described protocols provided mild reaction conditions, high yields and high atom- and step-economy. New macrocycles with hanging dihydroisoalantolactone units, different combinations of heteroatoms, and ring sizes in the range of 16–36 atoms were characterized by NMR and UV–vis spectroscopy and mass spectrometry analysis. The molecular structures and intermolecular interactions of two new macrocyclic compounds were elucidated using single-crystal X-ray crystallography. Upon addition of Mg(II) or Zn(II) cations to these novel ligands, using titration experiments we observed the formation of 1:1 (16:Mg2+) complexes and 1:1 to 2:1 (16:Zn2+) complexes, respectively, according to stoichiometry. The result suggests that dihydriisoalantolactone and triazole units within the molecules formed complexes with Mg (II) and Zn (II) ions in solution.

Pressure-induced phase changes in natural fluorapophyllite-(K) studied by Raman spectroscopy

The high-pressure Raman spectra in the low-wavenumber region (50–1200 cm−1) and the hydroxyl stretching vibration region (2600–3800 cm−1) of fluorapophyllite-(K) were collected in the interval of 0.0–50.7 GPa. Experimental results show that fluorapophyllite-(K) undergoes a crystalline-crystalline phase transition from a tetragonal structure (P4/mnc) to an orthorhombic structure (Pnnm) and then amorphization under high pressure conditions. Discontinuous changes in Raman peaks in the hydroxyl vibration region (2600–3800 cm−1) and the low-wavenumber region (50–1200 cm−1) occur at different onset pressures, suggesting that the destabilization of sub-lattices in fluorapophyllite-(K) under high pressure is not synchronous; the weak interlayer H2O structural units are more prone to destabilization at lower pressures than the rigid SiO4 tetrahedral layer units. Therefore, H2O groups in fluorapophyllite-(K) serve as sensitive local probes during the pressure-induced phase transition and amorphization.

Intrinsically stretchable fully π-conjugated polymer film via fluid conjugated molecular external-plasticizing for flexible light-emitting diodes

Fully π-conjugated polymers with rigid aromatic units are promising for flexible optoelectronic devices, but their inherent brittleness poses a challenge for achieving high-performance, intrinsically stretchable fully π-conjugated polymer. Here, we are establishing an external-plasticizing strategy using semiconductor fluid plasticizers (Z1 and Z2) to enhance the optoelectronic, morphological, and stretchable properties of fully π-conjugated polymer films for flexible light-emitting diodes. The synergistic effect of hierarchical structure and optoelectronic properties of Z1 in poly(9,9-di-n-octylfluorene-alt-benzothiadiazole) (F8BT) films enable excellent stretchable deformability (~25%) and good conductivity. PLEDs based on F8BT/Z1 films show stable electroluminescence and efficiency under 15% stretch and 100 cycles at 10% strain, revealing outstanding stress tolerance. This strategy is also improving the stretchable properties of polymers like poly(9,9-di-n-octylfluorenyl-2,7-diyl) (PFO) and poly(2-methoxy-5(2′-ethyl)hexoxy-phenylenevinylene) (Super Yellow), demonstrating its general applicability. Therefore, this strategy can provide effective guidance for designing high-performance stretchable fully π-conjugated polymers films for flexible electronic devices.

Three-dimensional interseismic crustal deformation in the northeastern margin of the Tibetan Plateau using GNSS and InSAR

The nature of the crustal deformation of the northeastern margin of the Tibetan Plateau is vital for elucidating the expansion mechanism of the plateau. We installed 21 continuous GNSS stations and obtained a horizontal velocity field with high spatial resolution. We also acquired a line-of-sight(LOS)velocity field with Sentinel-1 images covering the study area from 2014 to 2022. A multi-scale spherical wavelet method was employed to unify the reference frames of GNSS and InSAR data. After unifying the reference frame, the two data types achieve high consistency. Combining GNSS and InSAR velocities yielded the three-dimensional interseismic velocity field in the northeastern margin of the Tibetan Plateau. Furthermore, we analyzed the crustal deformation characteristics based on the three-dimensional deformation field. The crustal deformation exhibits a pronounced northeastward shift relative to the Ordos block, whereas the interior of the Ordos block remains remarkably stationary, behaving as a rigid unit. The Liupanshan fault is primarily characterized by uplift, devoid of any notable horizontal deformation across the fault. The left-lateral strike-slip mainly characterizes the Haiyuan fault.. The maximum east–west deformation velocity on the southern side of the fault is approximately 3.9 mm/yr, decreasing to about 1.0 mm/yr at the eastern end of the fault. The western segment of the West Qinling fault exhibits a minor east–west motion. Our result provides essential data for further study of the crustal deformation patterns.

Natural resin-derived urushiol-based phosphorylation derivative towards flame-retardant and mechanically strong epoxy resin

Biobased flame retardants have attracted great attention owing to their environmental friendliness and easy availability. Urushiol, extracted from natural resin-raw lacquer, has been capped with diphenylphosphoryl chloride to afford a biobased flame retardant, namely urushiol-based phosphonate (U-DC). As an additive this material is effective in reducing flammability while maintaining good mechanical strength for epoxy resins (EP). Impressively, an EP/9 %U-DC blend exhibits a UL-94 V-0 rating, and an LOI of 37.1 % for combustion. Further, compared to that for EP, the peak heat release rate (pHRR) and total heat release (THR) for the EP/9 %U-DC blend was lower by 40.5 % and 26.6 %. Through analysis of volatile products formed and char residue produced during polymer degradation, a mode of flame retardant action for U-DC has been proposed. Further, EP/U-DC blends display better mechanical properties than those of unmodified EP. Tensile strength of EP containing 7 wt% U-DC (81.6 MPa) is greater than that for unmodified EP (64.4 MPa). This may be ascribed to the presence of abundant rigid benzene units in U-DC and chain entanglement between the long side chain of U-DC and the epoxy macromolecular chain. These observations provide a basis for the utilization of new urushiol derivatives in the production of high-performance EP.

Envelope vector solitons in nonlinear flexible mechanical metamaterials

In this paper, we employ a combination of analytical and numerical techniques to investigate the dynamics of lattice envelope vector soliton solutions propagating within a one-dimensional chain of flexible mechanical metamaterial. To model the system, we formulate discrete equations that describe the longitudinal and rotational displacements of each individual rigid unit mass using a lump element approach. By applying the multiple-scales method in the context of a semi-discrete approximation, we derive an effective nonlinear Schrödinger equation that characterizes the evolution of rotational and slowly varying envelope waves from the aforementioned discrete motion equations. We thus show that this flexible mechanical metamaterial chain supports envelope vector solitons where the rotational component has the form of either a bright or a dark soliton. In addition, due to nonlinear coupling, the longitudinal displacement displays kink-like profiles thus forming the 2-components vector soliton. These findings, which include specific vector envelope solutions, enrich our knowledge on the nonlinear wave solutions supported by flexible mechanical metamaterials and open new possibilities for the control of nonlinear waves and vibrations.

Regional Functionalization Molecular Design Strategy: A Key to Enhancing the Efficiency of Multi-Resonance OLEDs.

Herein, we propose a regional functionalization molecular design strategy that enables independent control of distinct pivotal parameters through different molecule segments. Three novel multiple resonances thermally activated delayed fluorescence (MR-TADF) emitters A-BN, DA-BN, and A-DBN, have been successfully synthesized by integrating highly rigid and three-dimensional adamantane-containing spirofluorene units into the MR framework. These molecules form two distinctive functional parts: part 1 comprises a boron-nitrogen (BN)-MR framework with adjacent benzene and fluorene units forming a central luminescent core characterized by an exceptionally rigid planar geometry, allowing for narrow FWHM values; part 2 includes peripheral mesitylene, benzene, and adamantyl groups, creating a unique three-dimensional "umbrella-like" conformation to mitigate intermolecular interactions and suppress exciton annihilation. The resulting A-BN, DA-BN, and A-DBN exhibit remarkably narrow FWHM values ranging from 18 to 14 nm and near-unity photoluminescence quantum yields. Particularly, OLEDs based on DA-BN and A-DBN demonstrate outstanding efficiencies of 35.0 % and 34.3 %, with FWHM values as low as 22 nm and 25 nm, respectively, effectively accomplishing the integration of high color purity and high device performance.

The Flower-Shaped Co (II) and Cu (II) Phthalocyanine Polymers as Highly Efficient and Stable Catalysts for Chemical Fixation of CO2 to Cyclic Carbonate

New flower-shaped metallophthalocyanine polymers (THB-4-M, M = Co, Cu) have been synthesized by using 1,3,5-Tri(4-hydroxyphenhyl) benzene (THB) as rigid and contorted units to control the morphology under the solvothermal method. The polymers were characterized using FT-IR, UV-vis, SEM, TGA, and XPS. These polymers were applied as heterogeneous catalysts for the chemical fixation of carbon dioxide (CO2) to cyclic carbonates without solvent. The influence of reaction parameters and different metal centers on the catalytic performance were studied in detail. Under optimal conditions, the catalysts showed high conversion (49.9–99.0%), selectivity (over 85%), and reusability at ambient conditions (at 1 bar CO2).

A Soft Exoskeleton For Hand Finger Rehabilitation Application Using Fully Elastic Pneumatic Actuators

In recent years, there has been a growing demand for wearable actuators, that can be worn on individual body parts. This demand is dynamically increasing due to the numerous potential applications such as rehabilitation and enhancing load-bearing capabilities. Exoskeletons are mechanical structures that supplement or facilitate human movements and increase the body parts natural capabilities. Despite their wide range of applications, rigid exoskeletons have several deficiencies that required further developments. Soft actuators have been developed to address these deficiencies, forming one of the main categories of easily wearable exoskeletons. The two categories - rigid and soft exoskeletons - complement each other in their structures during applications. Soft robotic elements enable precise and delicate movements while providing adequate flexibility during use and rigid units are responsible for the stable frame structure and fixation. Their combined use is applied for rehabilitation, occupational safety, and enhancing work performance purposes. The aim of this article is to physically realize a device that has a legitimate purpose in the field of human hand rehabilitation. The goal was to design, manufacture, and functionally test the elements of a device capable of assisting in the rehabilitation of fingers using completely flexible actuators.

Relaxor unveils geometrical frustration

For over a century, materials science has been focused on comparing magnetism and ferroelectricity, revealing similarities in order types, domains, hysteresis, and responses to external stimuli. The exceptional physical properties of magnets often originate from frustration, which can result from site disorder and lattice geometry. While disordered relaxor ferroelectrics exhibit ultra-high dielectric and piezoelectric properties and fingerprinted behavior similar to spin glasses, ferroelectric-like materials with clear geometrically frustrated states have not been previously identified. Here we introduce a new type of relaxor material, a geometrically frustrated relaxor, exemplified by a Bi2Ti2O7 single crystal with a compositionally ordered pyrochlore structure. Our findings demonstrate canonical relaxor behavior, including dielectric anomalies, dipole freezing, non-ergodicity and a lack of spontaneous phase transitions. Furthermore, we show the emergence of a unique dipole ice state upon cooling, arising from conflicting order parameters related to two mutually exclusive rigid unit modes of Bi4Oʹ tetrahedral rotations. The coexistence of these rotations does not satisfy symmetry constraints, causing geometrical frustration and suppressing the long-range order. The results provide the structural mechanism of geometrical frustration manifestation in Bi-containing pyrochlores, opening up avenues for exploring exotic ground states and advanced functionalities in dielectric materials.

Di-piperidinium side chain functionalized poly(anthracene-co-p-terphenyl piperidinium) anion exchange membranes with microphase separation structure

It is an important research topic to construct microphase separation in anion exchange membranes (AEMs). The integration of rigid anthracene units into the main chains to form poly(anthracene-co-p-terphenyl piperidinium) AEMs is a new method by using π-π stacking to regulate microphase separation and construct ion transport channels in membranes. In this study, anthracene units were introduced for the first time to prepare AEMs with different anthracene contents. It is found that the introduction of rigid anthracene units into the backbone leads to an increase in the fractional free volume (FFV) of the membranes and a decrease in the ion conductive resistance. Moreover, the existence of long flexible di-piperidinium side chain helps to adjust the rigidity of the AEMs and enhances the mechanical properties of the membrane. The ionic conductivity of PA10TP-DMP is 153.8 mS cm−1 (80 °C). In the meanwhile, the conductivity retention of 91.7% was observed after the alkaline resistance test (80 °C, 2 M NaOH) for 1200 h. In addition, the PA10TP-DMP based H2-O2 single cell has a peak power density of 840.3 mW cm−2 and a high durability after 100 h test.

Tröger’s base-derived thin film composite membrane for enhanced nanofiltration performance

Nanofiltration (NF) membrane technology serves as an efficient method for separation and purification, playing a vital role in various industrial fields such as water treatment, food processing, and pharmaceutical manufacturing. However, there are still drawbacks, such as limited flux due to densely crosslinked composite layer and poor stability in solvents. In this study, we report the fabrication of the thin-film composite (TFC) NF membrane using Tröger’s base-derived building block, aiming to manipulate intrinsic pore structures of the as-synthesized ultra-thin composite layer by introducing rigid dihedral units. The interfacial polymerization process is employed to enable the polycondensation of Tröger’s base-based diamine monomer and tri-aldehyde monomer via Schiff base reaction. The effects of monomer concentration, immersion time, interfacial polymerization reaction time, heat treatment time and temperature on the performance of NF membrane were studied. The optimized NF membrane presents a rejection of Methyl blue (MB) above 95.3 % and achieves a high water permeance of 43.4 L·m−2·h−1·bar−1. The water permeance is 2–3 times higher than the reported NF membranes with similar rejection ability. In addition, Tröger’s base-derived TFC NF membrane exhibits excellent long-term stability and good organic solvent tolerance. Considering the high water permeance and separation efficiency, the present membrane has significance in dye removal and separation processes.

A Cyanine with 83.2% Photothermal Conversion Efficiency and Absorption Wavelengths over 1200 nm for Photothermal Therapy.

Developing small-molecule photothermal agents (PTAs) with good near-infrared-II (NIR-II) response for deeper tissue penetration and minimizing damage to healthy tissues has attracted much attention in photothermal therapy (PTT). However, concentrating ultra-long excitation wavelengths and high photothermal conversion efficiencies (PCEs) into a single organic small molecule is still challenging due to the lack of suitable molecular structures. Here, six polymethine cyanine molecules based on the structure of indocyanine green are synthesized by increasing the conjugated structure of the two-terminal indole salts and the number of rigid methine units, and incorporating longer alkyl side chains into the indole salts. Ultimately, IC-1224 is obtained with an absorption wavelength of more than 1200nm, which has a high PCE up to 83.2% in the NIR-II window and exhibits excellent PTT tumor ablation performance. This provides a high-performance NIR-II-responsive PTA, and offers further possibilities for the application of PTT in biomedical fields.

Kinematic modeling and formability analysis of revolved bodies formed by origami waterbomb units based on a chain-like layer-building method

ABSTRACT Origami patterns play a critical role in the field of soft and reconfigurable robotics. The revolved body formed by waterbomb units is also widely used in robot design. The kinematic model plays a key role in understanding motion characteristics and is vital for dynamic modeling and control of robots based on origami. However, while the deformation of origami patterns is well-studied on the finite element level, the assembly of rigid origami patterns is rarely explored on the kinematic level. Therefore, we propose a chain-like assembly method for constructing revolved bodies using rigid waterbomb units, ensuring crease status unalternation, collision avoidance, axis existence, and seamless assembly. We explore the formability of waterbomb units and investigate the resulting revolved body with some layer and column numbers of waterbomb units. Results demonstrate that increasing the number of columns does not necessarily provide more space for building layers. Additionally, they reveal boundaries of the layer and column numbers for constructing the revolved body and highlight the impact of the aspect ratio and configuration of the waterbomb units on the formability of the revolved body. This method can provide insights for origami-based robot research and can be extended to model other origami patterns.

Unprecedented Richness of Temperature- and Pressure-Induced Polymorphism in 1D Lead Iodide Perovskite.

Inherent features of metal halide perovskites are their softness, complex lattice dynamics, and phase transitions spectacularly tuning their structures and properties. While the structural transformations are well described and classified in 3D perovskites, their 1D analogs are much less understood. Herein, both temperature- and pressure-dependent structural evolutions of a 1D AcaPbI3 perovskitoid incorporating acetamidinium (Aca) cation are examined. The study reveals the existence of nine phases of δ-AcaPbI3, which present the most diverse polymorphic collection among known perovskite materials. Interestingly, temperature- and pressure-triggered phase transitions in the 1D perovskotoid exhibit fundamentally different natures: the thermal transformations are mainly associated with the collective translations of rigid polyanionic units and ordering/disordering dynamics of Aca cations, while the compression primarily affects inorganic polymer chains. Moreover, in the 1-D chains featuring the face-sharing connection mode of the PbI6 octahedra the Pb···Pb distances are significantly shortened compared to the corner-sharing 3D perovskite frameworks, hence operating in the van der Waals territory. Strikingly, a good correlation is found between the Pb···Pb distances and the pressure evolution of the bandgap values in the δ-AcaPbI3, indicating that in 1D perovskitoid structures, the contacts between Pb2+ ions are one of the critical parameters determining their properties.

Regulating the photoisomerization pathway to achieve efficient E → Z isomerization of azobenzene-embedded molecular cages

Achieving efficient E → Z photoconversion of Azobenzene is now still a challenge. Based on our previously reported cage C1, which exhibits an E → Z photoisomerization efficiency of up to 94%, two additional cages C2 and C3 were synthesized with more rigid and longer units replacing the flexible diphenyl ether motifs in C1. It was found that, when the diphenyl ether rims were changed to biphenyl groups (C2), or to diphenylacetylene motifs (C3), the dihedral angles of the two benzene rings of the azobenzene rim in these cages decreased correspondingly from 48.86° to 42.96°, and finally to 30.13°. The E → Z photoisomerization quantum yields measurements indicate that, with the decreasing of the dihedral angles, the role of the inversion pathway in the E → Z processes of these cages gradually decreases, while the role of the rotation pathway becomes increasingly greater, accompanied by the decreasing in the E → Z photoconversions from 94% to 87%, and to 72%. These results validate our new strategy of promoting inversion pathway/inhibiting rotation pathway to achieve efficient E → Z photoconversion of azobenzene.

A reconfigurable metamaterial using trapeziums and triangles with alternative connectivity

A category of metamaterial that can manifest a wide range of Poisson's ratio from positive to negative is presented herein. This metamaterial consists of rigid units in the shapes of right trapeziums and right triangles that are connected at their corners in the form of necks, which supply elastic restraint during relative rotation of the rigid units. The on-axes Poisson's ratio of the metamaterial was formulated by geometrical analysis. By assigning a rotational spring constant to the connecting necks, the total spring potential energy for a specific enclosure was obtained. This energy was then matched against the strain energy of deformation for the homogenized continuum of the metamaterial for the same enclosure to give the on-axes Young's moduli. Results reveal a configuration that enables the metamaterial to display sign-programmable Poisson's ratio. In addition to being able to adjust the on-axes Young's moduli relative to each other, two specific configurations have been identified that permit both on-axes Young's moduli to be equal. The ease of reconfiguration, the wide range of effective mechanical properties and the capability of the Poisson's ratio sign to be programmed, therefore, avail the metamaterial as a viable material for applications that require frequent in situ adjustment of effective properties.