Bridging Mode Research Articles

Effect of near-fault vertical ground motions on failure mode of long-span sea-crossing cable-stayed bridges

Existing investigations have proved that the near-fault vertical ground motion (VGM) would have a significant effect on the seismic performance of bridge structures. This study mainly investigates the combined effect of VGM and horizontal ground motion (HGM) on failure mode and component damage sequence of long-span sea-crossing cable-stayed bridges. For this purpose, a long-span sea-crossing cable-stayed bridge considering the pile-soil effect and hydrodynamic effects is selected in this paper. The seismic demand models and limit state models are developed under the combination of VGM and HGM to perform the component fragility analysis, which aims to evaluate the damage state and sequence of key components. The results indicate that VGM has little effect on the damage probability of the bearings, but an adverse effect on the damage probability of the pylons and piers. The vulnerable component would be changed from the bearing to the pier and pylon with strong VGM. Meanwhile, the three-dimensional fragility surface of each component based on the horizontal peak ground velocity (Vx) and the ratio of vertical to horizontal component (αV/H) is obtained by convolution. Thus, the effects of Vx and αV/H on the damage mechanism of the cable-stayed bridge in different damage states are quantified.

Unprecedented Thermo‐Enhanced Retainable Circularly Polarized Luminescence

AbstractCircularly polarized luminescence (CPL) enabled by chiral self‐assembly is very promising in diversified applications. However, temperature‐triggered disassembly or self‐assembly transition often results in reduction or even silence of CPL. Here, a strategy of coordinating self‐assembly is reported that offers temperature enhanced and retainable CPL that is resistant to further temperature variation. Upon co‐assembling commercial dyes with the coordinating hydrogel of cholate‐calcium, the chirality transfer from cholate to the dyes allows generation of CPL. With increasing temperature, the CPL intensity can be enhanced 4 times and the emission dissymmetry factorgemcan be promoted from 0.04 to 0.1, then they remain stable either upon further elevating or lowering temperature. Mechanism study reveals that increasing temperature has triggered the coordination transition between the carbonate groups and Ca2+from the metastable bidentate chelating to the thermal stable bridging mode, which drives the transition from flexible nanohelices to stiff helical bunches. This promotes the alignment of the dyes and in the meantime decreases its mobility, thus leads to increased CPL intensity andgem. It is envisioned that the strategy of coordinating self‐assembly would be very promising in creating thermally stable CPL for diversified applications.

Pillararene-Inspired Macrocycles: From Extended Pillar[n]arenes to Geminiarenes.

chemistry since their establishment due to their innate functional features of molecular recognition and complexation. The rapid development of modern supramolecular chemistry has also significantly benefited from creating new macrocycles with distinctive geometries and properties. For instance, pillar[n]arenes (pillarenes), a relatively young generation of star macrocyclic hosts among the well-established ones (e.g., crown ethers, cyclodextrins, cucurbiturils, and calixarenes), promoted a phenomenal research hotspot all over the world in the past decade. Although the synthesis, host-guest properties, and various supramolecular functions of pillarenes have been intensively studied, many objective limitations and challenges still cannot be ignored. For example, high-level pillar[n]arenes (n > 7) usually do not possess applicable large-sized cavities due to structural folding and cannot be synthesized on a large scale because of the uncompetitive cyclization process. Furthermore, two functional groups must be covalently para-connected to each repeating phenylene unit, which severely limits their structural diversity and flexibility. In this context, we have developed a series of pillarene-inspired macrocycles (PIMs) using a versatile and modular synthetic strategy during the past few years, aiming to break through the synthetic limitations in traditional pillarenes and find new opportunities and challenges in supramolecular chemistry and beyond. Specifically, by grafting biphenyl units into the pillarene backbones, extended pillar[n]arenes with rigid and nanometer-sized cavities could be obtained with reasonable synthetic yields by selectively removing hydroxy/alkoxy substitutes on pillarene backbones, leaning pillar[6]arenes and leggero pillar[n]arenes with enhanced structural flexibility and cavity adaptability were obtained. By combining the two types of bridging modes in pillarenes and calixarenes, a smart macrocyclic receptor with two different but interconvertible conformational features, namely geminiarene, was discovered. Benefiting from the synthetic accessibility, facile functionalization, and superior host-guest properties in solution or the solid state, this new family of macrocycles has exhibited a broad range of applications, including but not limited to supramolecular assembly/gelation/polymers, pollutant detection and separation, porous organic polymers, crystalline/amorphous molecular materials, hybrid materials, and controlled drug delivery. Thus, in this Account, we summarize our research efforts on these PIMs. We first present an overview of their design and modular synthesis and a summary of their derivatization strategies. Thereafter, particular attention is paid to their structural features, supramolecular functions, and application exploration. Finally, the remaining challenges and perspectives are outlined for their future development. We hope that this Account and our works can stimulate further advances in synthetic macrocyclic chemistry and supramolecular functional systems, leading to practical applications in various research areas.

Completely non-contact modal testing of full-scale bridge in challenging conditions using vision sensing systems

Vision-based modal testing method can provide a contactless approach to understanding dynamic properties of bridges. However, the applicability of this method to in-service bridge measurement has been limited by its drawbacks, such as low-accuracy measurement data of entire bridges, low robustness to varying lighting, artificial target installation or distinct natural features requirement, etc. In addition, the existing vision-based methods rarely captured torsional modes of the real-life bridges, leading to an insufficient understanding of the fundamental dynamic properties of the structures. This paper proposes a new vision-based modal testing framework to overcome these drawbacks. A multiple-setup strategy with three time-synchronised cameras is used to record videos of dynamic structural motion. A robust object tracking technique is used to extract reliable displacement of the field structure from the videos with significant noises. This framework provides a completely non-contact approach to capture bending and torsional modal properties of full-scale bridges in uncontrolled field conditions. A large-scale laboratory bridge and in-service suspension footbridge were selected to verify the feasibility of the proposed approach to extract correlated modal properties. The modal analysis results showed a satisfactory agreement with the accelerometer measurement, demonstrating the proposed framework's efficacy in operational modal analysis.

A three-dimensional wire-feeding model for heat and metal transfer, fluid flow, and bead shape in wire plasma arc additive manufacturing

A three-dimensional wire-feeding model has been developed to study the transient coupling behaviour of heat and metal transfer, fluid flow, and solidified bead shape in wire plasma arc additive manufacturing (WPAAM). A novel surface heat source model considering the arc energy shading effect is proposed and adopted. An improved momentum source of the arc force considering the arc pressure shading effect is also developed and used. This model has been used to study the metal transfer dynamics, flow patterns, and bead shape of the WPAAM process with a wire-feeding speed (WFS) of 1–5 m/min. The simulated results agreed reasonably with the experimental data. As the WFS increased from 1 to 5 m/min, three different metal transfer modes were observed, which changed from globular droplet mode to droplet-liquid bridge mode and solid-liquid bridge mode. Detailed metal transfer information was analysed, including metal transfer position, shape, average temperature, and main driving force. The effects of the arc shading and metal transfer on the melt pool dynamics and bead shape were simulated and discussed. A periodic flow pattern of the melt pool produced by the metal transfer impact causes ripples or even humping defects. As the WFS increased, the melt pool depression gradually disappeared due to the arc pressure shading effect. When the WFS increased to 5 m/min, a temperature drop of about 140 K in the central melt pool, caused by the arc energy shading effect and cold metal transfer, weakened the lateral flow significantly, which explained the decrease of bead width at a large WFS. The results demonstrate that the developed wire-feeding model and findings could be used as a theoretical tool and basis to better understand the underlying physical mechanisms and achieve bead shape control in the WAAM process.

The Formation, Structural Characteristics, Absorption Pathways and Bioavailability of Calcium-Peptide Chelates.

Calcium is one of the most important mineral elements in the human body and is closely related to the maintenance of human health. To prevent calcium deficiency, various calcium supplements have been developed, but their application tends to be limited by low calcium content and highly irritating effects on the stomach, among other side effects. Recently, calcium–peptide chelates, which have excellent stability and are easily absorbed, have received attention as an alternative emerging calcium supplement. Calcium-binding peptides (CaBP) are usually obtained via the hydrolysis of animal or plant proteins, and calcium-binding capacity (CaBC) can be further improved through chromatographic purification techniques. In calcium ions, the phosphate group, carboxylic group and nitrogen atom in the peptide are the main binding sites, and the four modes of combination are the unidentate mode, bidentate mode, bridging mode and α mode. The stability and safety of calcium–peptide chelates are discussed in this paper, the intestinal absorption pathways of calcium elements and peptides are described, and the bioavailability of calcium–peptide chelates, both in vitro and in vivo, is also introduced. This review of the research status of calcium–peptide chelates aims to provide a reasonable theoretical basis for their application as calcium supplementation products.

Stitching electron localized heptazine units with “carbon patches” to regulate exciton dissociation behavior of carbon nitride for photocatalytic elimination of petroleum hydrocarbons

The electron localized heptazine units make it difficult to separate photoinduced electeron-hole pairs for graphitic carbon nitride (g-C3N4), which limits the application prospect of graphitic-like carbon nitride. Changing inherent N-(C)3 bridging mode of in-plane heptazine units and built more electron channel could be a reasonable strategy. Herein, “carbon patches” were introduced to stitch heptazine units, high speed electron transfer path were thus constructed due to delocalized p orbital electron in “carbon patches” as a result. Simultaneously, interlayers’ high speed electron transfer channel was also constructed by distorted molecular layer because of presence of large electronegative interstitial phosphorus atoms. Such photoinduced electron-holes’ spatial separation in-plane and interlayers were built concurrently and confirmed by XANES and DFT calculation for the first time. The resulted PCCNv series photocatalysts exhibited superior photon absorption capability, excellent charge carriers’ separation kinetics, good O2 molecule adsorption as well as activation capability, the resulted abundant reactive radicals contributed to petroleum hydrocarbons photocatalytic degradation significantly. This work shed light on efficient separation of photoinduced excition for carbon nitride in photocatalysis, simultaneously presented a promising candidate non-metal photocatalytic environmental material for marine oil spill remediation.

Design and synthesis of hydrogen-bonded organic frameworks based on Ni4L4 cubane units

The construction of hydrogen-bonded organic frameworks (HOFs) by strong intermolecular hydrogen bonding interactions has received much attention in recent years. Different from common reported organic molecules based HOFs, we demonstrate here the Ni4L4 cubane (L ​= ​S-1,2-bis(benzimidazole-2-yl)) containing carboxylate ligands is a powerful subunit for the construction of HOFs. In this subunit, four Ni2+ ions are coordinated by four LH ligands to form typical cubane structure, two carboxylic ligands occupy the remaining four coordination sites in bridging mode. Based on this structure, a series of carboxylic ligands containing potential H-bond sites are employed to control the self-assembly of Ni4L4 cubane to generate different HOFs with improved stability and tunable magnetic properties.

Targeting Diverse Bridging Motifs within Actinide Borosulfates and Establishing an Unconventional Structural Hierarchy.

The first actinide borosulfates, (UO2)[B(SO4)2(SO3OH)] (TSUBOS-1) and (UO2)2[B2O(SO4)3(SO3OH)2] (TSUBOB-1), were synthesized solvothermally in oleum using UO3. The classical borosulfate crystal structure of TSUBOS-1 is partially consistent with an established conventional hierarchy. Uranyl pentagonal bipyramids limit the anionic network linkages and isolate sulfate tetrahedra within the anionic network. Therefore, the classical one-dimensional chain established in the hierarchy does not fully describe the structure. The structure of TSUBOB-1 is the first actinide borosulfate that contains an unconventional borate-to-borate bridging mode (denoted B-O-B) and a zero-dimensional oxoanionic unit consisting of one sulfate tetrahedron that shares vertices with two B-O-B bridged borate tetrahedra that each share a vertex with two sulfate tetrahedra. As this structure departs from the existing structural hierarchy, a modified approach for understanding the unconventional borosulfate substructure and dimensionality is proposed, together with a new graphical notation. In the course of our synthesis experiments, a novel uranyl disulfate compound (UO2)2[(S2O7)(SO3OH)2] (TSUDS) was isolated and characterized. The structure of TSUDS is a framework consisting of uranyl pentagonal bipyramids and sulfate tetrahedra. Each uranyl pentagonal bipyramid is surrounded by five sulfate tetrahedra, two of which share a vertex creating a disulfate with a S-O-S bridging mode. The uranyl bipyramids are linked to one another via the singular sulfate or disulfate groups.

Two isomers Ba5Mg4C54O48H114 and Pb5Mg4C54O48H114

Abstract There are reported two related structures of Ba5Mg4C54O48H114 (dodeca(aqua-6κ 3O,7κ 3O,8κ 3O,9κ 3O)-tris(μ2-propanoato-1:6κ 2O,1κO′)-tris(μ-propanoato-2:7κ 2O,2κO′-tris(μ-propanoato-3:8κ 2O,3κO′)-tris(μ-propanoato-4:9κ 2O,4κO′)-hexakis(μ3-propanoato-1:5κ 2O,2:5κ 2O′;1:5κ 2O,3:5κ 2O′;1:5κ 2O,4:5κ 2O′;2:5κ 2O,3:5κ 2O′;2:5κ 2O,4:5κ 2O′;3:5κ 2O,4:5κ 2O′)-pentabarium tetramagnesium), (I), and Pb5Mg4C54O48H114 (dodeca(aqua-1κ 3O,2κ 3O,3κ 3O,4κ 3O)-hexakis(μ3-propanoato-1:5κ 2O,2:5κ 2O′;1:5κ 2O,3:5κ 2O′;1:5 κ 2O,4:5κ 2O′;2:5κ 2O,3:5κ 2O′;2:5κ 2O,4:5κ 2O′;3:5κ 2O,4:5κ 2O′)tetramagnesium lead(II) tris(propanoato-κ 2O,O′)plumbate(II)), (II). The title structures are compositional isomers which crystallize in the same space group type. The structure of (I) comprises molecules with symmetry 4 ‾ 3 m $\overline{4}3m$ . The structure (II) comprises the complex cation {Pb(C3H5O2)6[Mg(H2O)3]4}4+ with the symmetry 4 ‾ 3 m $\overline{4}3m$ and four anions [tris(propanoato-κ 2O,O′)plumbate(II)]−, [Pb(C3H5O2)3]− , with 3m symmetry. The central cations Ba12+ and Pb12+ in (I) and in the cation {Pb(C3H5O2)6[Mg(H2O)3]4}4+ of the structure (II), respectively, have similar structural features which are comparable to the environment of the Ba2+ cation in BaCa2(C3H5O2)6 [Stadnicka, K. & Glazer, A. M. (1980). Acta Cryst. B36, 2977–2985]. The molecules in (I) and the ions in (II) are interconnected by Owater‒H⋯Opropanoate hydrogen bonds of a moderate strength. The ethyl chains are disordered which is common in propanoates. However, there are unprecedented features in the title structures: 1) The central atom Pb12+ is the first known example of a Pb2+ cation which is surrounded by six carboxylates in a bidentate bridging mode, i.e. by 12 oxygens. 2) The anion [tris(propanoato-κ 2O,O′)plumbate(II)]− has a constitution with unusually prominent stereochemical activity of the 6s 2 electron pair of the cation Pb2+ completing the coordination to the tetrahedral one. Thus, its formula can be expressed as [Pb[ψ−4t](C3H5O2)3]−. 3) In both title structures, there are propanoate molecules with disordered carboxylate oxygens.

Damage modes and residual deflections of multi-beam hollow slab bridge under car explosions

The purpose of this study is to investigate the damage modes and residual deflection of multi-beam hollow slab bridges under car explosions. To comprehensively estimate the blast response, the failure process of the bridge with different beam numbers are cautiously simulated and compared. With the experimentally validation of the constitutive laws and the fluid–structure interaction parameters, the impact analysis software Autodyn is adopted to capture the damage mechanisms and the vibration histories. After cautious numerical simulations, local punching shear failure and global flexural failure dominate the damage modes of multi-beam hollow slab bridges. Due to the oversized impact energies and the insufficient structural resistance, overall collapse is observed in bridge with 4 or 6 beams in middle and acentric explosions. For bridge with 8 or 10 beams, the formed plastic hinges imply the large residual deflection and possible overall collapse during middle explosions. Owing to the easier energy dissipation and the smaller impact areas, limited flexural damage are discovered in bridge with 8 or 10 beams under acentric explosions. Due to the limited flexural damage and the small residual deflection of the distant beams, these beams can maintain great bearing capacity and can be repaired after explosions.

BSA Interaction, Molecular Docking, and Antibacterial Activity of Zinc(II) Complexes Containing the Sterically Demanding Biomimetic N3S2 Ligand: The Effect of Structure Flexibility.

Two zinc(II) complexes, DBZ and DBZH4, that have (ZnN3S2) cores and differ in the bridging mode of the ligating backbone, effectively bind to BSA. The binding affinity varies as DBZ > DBZH4 and depends on the ligand structure. At low concentrations, both complexes exhibit dynamic quenching, whereas at higher concentrations they exhibit mixed (static and dynamic) quenching. The energy transfer mechanism from the BSA singlet excited state to DBZ and DBZH4, is highly likely according to steady-state fluorescence and time-correlated singlet photon counting. Molecular docking was used to support the mode of interaction of the complexes with BSA and showed that DBZ had more energy for binding. Furthermore, antibacterial testing revealed that both complexes were active but to a lesser extent than chloramphenicol. In comparison to DBZH4, DBZ has higher antibacterial activity, which is consistent with the binding constants, molecular docking, and particle size of adducts. These findings may have an impact on biomedicine.

Analytical investigation of the main cable bending stiffness effect on free flexural vibration of suspension bridges with a 3D cable system

This paper proposed a dimensionless continuum model of suspension bridges to comprehensively study the bending stiffness effect of the 3D cable system on the structural free flexural vibration, which has seldom been investigated in previous studies. In this model, coupled differential equations including the cable bending resistance term are derived via the Galerkin method. The equations are then nondimensionalized from a set of key design parameters, including the lateral inclination of hangers. The precision of the model is validated with the finite element (FE) method through an example. Then, parametric comparative studies of the effect under dimensionless parameters are conducted between 3D and 2D cable system suspension bridges. The results show that, the bending stiffness effects of the 3D cable system are more evident on the high order modes and antisymmetric modes of suspension bridges, which is similar with those effects of the 2D cable system. The hanger lateral inclination restrains the effect on the structural frequencies following a relationship of linear negative correlation; when the inclination angle varies from 30 to 60 degrees, the effect ratio of 3D to 2D cable system correspondingly varies from 0.33 to 0.67. Under a given hanger lateral inclination (48.6 degrees) with other identical conditions, the variation trend of the effects on the high order frequencies are similar between 3D and 2D cable systems; the effect value of the 3D cable system is on average 0.625 times that value of the 2D cable system.

Three-dimensional nonlinear aerostatic stability analysis of long-span suspension bridges under skew wind

Based on the aerostatic force model under skew wind, considering the nonlinear and three-dimensional effects of aerostatic forces and also structural geometric nonlinearity, a method of three-dimensional nonlinear aerostatic stability analysis under skew wind is presented, and the corresponding computational procedure (SNAA-SW) is developed. By taking a suspension bridge- the Runyang suspension bridge over the Yangtze River as example, 3D nonlinear aerostatic stability analysis of the bridge under skew wind is conducted, and the skew wind effect on the aerostatic stability of long-span suspension bridges is ascertained. The results show that the skew wind effect does not change the aerostatic instability mode of suspension bridges, which shows a spatial bending-torsion coupled instability mode as the same as normal wind case. The skew wind has positive and negative effects on the aerostatic stability of suspension bridge under different wind attack angles, and the evolutions of critical wind speed of aerostatic instability with wind yaw angle are completely different from the cosine rule as proposed by the skew wind decomposition method, for most cases, the lowest critical wind speed of aerostatic instability occurs under skew wind. With the increase of wind yaw angle, the skew wind effect on the critical wind speed of aerostatic instability becomes more prominent, and the influence is between −10.7% and 8.1%. Therefore, the skew wind effect needs to be accurately considered in the aerostatic stability analysis of long-span suspension bridges in particular at large wind yaw angles.

The tuning of oxalato-bridge on magnetic interaction and field-induced phase transition in Ba2Co2Cl2(C2O4)3·4H2O

The crystal structure of the oxalato-bridged compound Ba2Co2Cl2(C2O4)3·4H2O has C2/c symmetry and contains two types of oxalate-bridged modes. We have investigated the magnetization behavior of the Ba2Co2Cl2(C2O4)3·4H2O sample with both the static and pulsed magnetic fields. The Bleaney-Bowers fitting for the temperature dependence of magnetization shows that there are two different spin-dimers with the different intra- and inter-dimer interactions. Using the high field sweep rate of the pulsed magnetic field, magnetization measurements show four continuous phase transitions (with four different critical magnetic fields) in a smaller magnetic field range from 5.5 to 7 T, which also confirms there are two different dimers. Based on the structure analysis, the four phase transitions might result from four different magnetic exchange interactions (J1, J'1, J2 and J'2) in the two different dimers. Thus, in the design of the molecular-based magnetic materials, the oxalato-bridged and its various bridging modes can be used to mediate the magnetic interaction of the intra- and inter-dimers, the electronic effect between the metal ions and induce new phases.

Limit state analysis of stepped sliding of jointed rock slope based on tensile-shear composite failure mode of rock bridges

Limit state analysis of stepped sliding of jointed rock slope based on tensile-shear composite failure mode of rock bridges

The biocatalytic activity of the “lantern-like” binuclear copper complex with trisulfide bridges mimicking SOD metallo-proteins

Through a redox process, an in situ transformation of propylthiouracil led to the formation of a trisulfur ligand that coordinates Cu(II) ion forming a lantern-like binuclear copper(II) complex [Cu2(ptu-S-ptu)2]. The complex was characterized by elemental analysis, spectroscopic techniques (FTIR, UV–Vis, EPR, and Hirshfeld surfaces analyses.), single-crystal X-Ray analysis, and its optimized molecular structure was obtained by DFT calculations. It crystallizes as a twin in the space group P-1, with two different, though closely related, centrosymmetric binuclear complexes per unit cell. The (ptu-S-ptu)2− thiouracil rings are nearly perpendicular to each other and their N and O atoms equatorially cis-coordinate the two copper ions in a two-fold Cu-OCN-Cu bridging mode. The four-fold bridging configuration is completed by another (ptu-S-ptu)2− ligand, inversion-related through the middle of the Cu…Cu contact. The elongated octahedral coordination around each copper is completed by the linking S-atom of the ligand at the axial position. The crystallographic results point to a copper d(x2-y2) d-orbital for the electron (or hole) ground state and optimal overlap of this orbital with molecular electronic path bridging the two metal atoms, hence indicating a relatively large antiferromagnetic coupling between them. The designed complex behaves as a promiscuous promising catalyst. It possesses intrinsic peroxidase-like activity catalyzing phenol red bromination in the presence of H2O2 at room temperature, and the oxidation of pyrogallol, and behaves as a superoxide dismutase (SOD) mimic compound acting on superoxide anion. Additionally, insights into their reactivity are analyzed by comparison with a family of other sulfur-containing copper(II) metal complexes in an attempt to explain the differences in catalytic properties and to determine the structural properties that affect the reactivity with substrates. Albumin interactions studies are also incorporated.

Temperature Load Mode of Bridge in Permafrost Region of Qinghai–Tibet Railway

The Qinghai–Tibet railway is the plateau permafrost railway with the highest altitude and the longest line in the world. The natural conditions along the line are harsh, with many unfavorable factors such as low temperature, strong ultraviolet radiation, and large changes in daily temperature, resulting in frequent bridge damage. In order to study the bridge temperature field and its effect in the permafrost region of the Qinghai–Tibet railway, a long-term field test was carried out, and a calculation model of sunshine temperature field of concrete two-piece T-beam was established based on the principle of meteorology and heat transfer. On this basis, the beam temperature difference load mode, beam section temperature distribution law, and temperature effect were obtained. As revealed, the daily temperature difference of the Qinghai–Tibet railway bridge is large in winter, which is related to the ground’s effective radiation and surface reflectivity, and the maximum value has exceeded the current codes. The beam section temperature field shows “internal heat and external cold” in the morning and “internal cold and external heat” from noon to evening. Under the action of strong radiation and large temperature difference, bridge displacement occurs frequently, by which it is easy to cause damage to rail fasteners and bridge bearings. Based on the field test and finite element analysis, the bridge temperature difference load mode was proposed, which makes up for the deficiency that the relevant codes do not consider the plateau’s special climatic conditions and can provide a reference for the construction of plateau railways such as the Sichuan–Tibet railway.

Structural Isomerization in Cu(I) Clusters: Tracing the Cu Thermal Migration Paths and Unveiling the Structure-Dependent Photoluminescence

Structural Isomerization in Cu(I) Clusters: Tracing the Cu Thermal Migration Paths and Unveiling the Structure-Dependent Photoluminescence

Photo‐Enhanced‐Coordination Triggered Unprecedented Bistable AIE for Long‐Term Optical Memories

AbstractPhoto‐triggered chromism has emerged as critically important in materials for advanced soft photonic devices. The conventional photochromic units with reversible color change between two isomers are unstable either thermally or photochemically, which is an important challenge for long‐standing optical devices. Here, a novel photo‐enhanced coordination mechanism leading to stable chromism is reported. Upon tethering the aggregation‐induced emission (AIE) moiety diphenyldibenzofulvene (PBF) to a dicarboxylic pyridine group, photo‐irradiation triggers the coordination transition between the carbonate groups and Mg2+ from bidentate to the more stable bridging mode, which further influences the conformation of the remote PBF group, leading to transition of the emission color from cyan to yellow. Under ambient conditions, both coordinating isomers display excellent thermal and photochemical stability. As a result, the photo writings on the films based on the coordinating AIE materials exhibit the long‐term stability, which barely fades even upon heating, vapor fuming, or day‐light exposure. This photo‐enhanced‐coordination enabled bistable chromism is expected to open a new vista in the study of chromism and high durable optical memories.