Chiral assembly of organic luminogens with aggregation-induced emission

Chirality is important to chemistry, biology and optoelectronic materials. The study on chirality has lasted for more than 170 years since its discovery. Recently, chiral materials with aggregation-induced emission (AIE) have attracted increasing interest because of their fascinating photophysical properties. In this review, we discussed the recent development of chiral materials with AIE properties, including their molecular structures, self-assembly and functions. Generally, the most effective strategy to design a chiral AIE luminogen (AIEgen) is to attach a chiral scaffold to an AIE-active fluorophore through covalent bonds. Moreover, some propeller-like or shell-like AIEgens without chiral units exhibit latent chirality upon mirror image symmetry breaking. The chirality of achiral AIEgens can also be induced by some optically active molecules through non-covalent interactions. The introduction of an AIE unit into chiral materials can enhance the efficiency of their circularly polarized luminescence (CPL) in the solid state and the dissymmetric factors of their helical architectures formed through self-assembly. Thus, highly efficient circularly polarized organic light-emitting diodes (CPOLEDs) with AIE characteristics are developed and show great potential in 3D displays. Chiral AIEgens are also widely utilized as “turn on” sensors for rapid enantioselective determination of chiral reagents. It is anticipated that the present review can entice readers to realize the importance of chirality and attract much more chemists to contribute their efforts to chirality and AIE study.

This review highlights the recent development of chiral materials with aggregation-induced emission properties, including their molecular structures, self-assembly and functions.     

基于模型缩聚的结构损伤统计识别

提出了一种基于有限元模型缩聚技术的结构损伤统计识别方法,该方法仅需要少量传感器的测量数据.首先基于模型缩聚技术建立确定性的损伤识别过程,然后利用摄动法将概率过程融入确定性的损伤识别中,从而得到了一种基于概率统计的结构损伤识别方法.该方法通过计算未知参数(如损伤构件的弹性特征)对于测量噪声的一阶与二阶偏导数,来得到这些未知参数的均值与协方差矩阵.文中不仅阐述了该方法的理论推导过程,而且通过一个门式框架的数值仿真研究,并结合Monte Carlo数值模拟技术验证了该文方法的正确性.     

Tunable Photochromism in the Robust Dithienylethene‐Containing Phospholes: Design,Synthesis, Characterization,Electrochemistry, Photophysics,and Photochromic Studies

A series of dithienylethene‐containing phosphole derivatives has been designed, synthesized and characterized. One of the compounds has been characterized by X‐ray crystallography. Upon photoexcitation, the compounds exhibit drastic color changes, ascribed to the reversible photochromic behavior. Their photochromic, photophysical and electrochemical properties have been studied. They show photochromic reactivities with high photocyclization quantum yields. Their photophysical and photochromic properties are found to be facilely tuned in this system by substitution at the phosphole backbone, as well as variation on the extent of π‐conjugation of the phosphole backbone. Some selected compounds have been demonstrated to exhibit photochromic properties in polymethylmethacrylate (PMMA) films.     

Hyperbolicity, transversality and analytic first integrals

Let A be a (normally) hyperbolic compact invariant manifold of an analytic diffeomorphism f of an analytic manifold M. We assume that the stable and unstable manifold of A intersect transversally (in an admissible way), the dynamics on A is ergodic and the modulus of the eigenvalues associated to the stable and unstable manifold, respectively, satisfy a non-resonance condition. In the case where A is a point or a torus, we prove that the discrete dynamical system associated to f does not admit an analytic first integral. The proof is based on a triviality lemma, which is of combinatorial nature, and a geometrical lemma. The same techniques, allow us to prove analytic non-integrability of Hamiltonian systems having Arnold diffusion. In particular, using results of Xia, we prove analytic non-integrability of the elliptic restricted three-body problem, as well as the planar three-body problem.     

Symbolic dynamics and Arnold diffusion

We consider hyperbolic tori of three degrees of freedom initially hyperbolic Hamiltonian systems. We prove that if the stable and unstable manifold of a hyperbolic torus intersect transversaly, then there exists a hyperbolic invariant set near a homoclinic orbit on which the dynamics is conjugated to a Bernoulli shift. The proof is based on a new geometrico-dynamical feature of partially hyperbolic systems, the transversality-torsion phenomenon, which produces complete hyperbolicity from partial hyperbolicity. We deduce the existence of infinitely many hyperbolic periodic orbits near the given torus. The relevance of these results for the instability of near-integrable Hamiltonian systems is then discussed. For a given transition chain, we construct chain of hyperbolic periodic orbits. Then we easily prove the existence of periodic orbits of arbitrarily high period close to such chain using standard results on hyperbolic sets.     

Unusual light-driven amplification through unexpected regioselective photogeneration of five-membered azaheterocyclic AIEgen

Developing versatile synthetic methodologies with merits of simplicity, efficiency, and environment friendliness for five-membered heterocycles is of incredible importance to pharmaceutical and material science, as well as a huge challenge to synthetic chemistry. Herein, an unexpected regioselective photoreaction to construct a fused five-membered azaheterocycle with an aggregation-induced emission (AIE) characteristic is developed under mild conditions. The formation of the five-membered ring is both thermodynamically and kinetically favored, as justified by theoretical calculation and experimental evidence. Markedly, a light-driven amplification strategy is proposed and applied in selective mitochondria-targeted cancer cell recognition and fluorescent photopattern fabrication with improved resolution. The work not only delivers the first report on efficiently generating a fused five-membered azaheterocyclic AIE luminogen under mild conditions via photoreaction, but also offers deep insight into the essence of the photosynthesis of fused five-membered azaheterocyclic compounds.

A multifunctional, AIE-based, fused five-membered azaheterocycle is photogenerated with light-driven amplification to combat the photobleaching issue and fabricate display materials.     

Polymorph selectivity of an AIE luminogen under nano-confinement to visualize polymer microstructures

Despite the huge progress of luminescent molecular assemblies over the past decade, it is still challenging to understand their confined behavior in semi-crystalline polymers for constrained space recognition. Here, we report a polymorphic luminogen with aggregation-induced emission (AIE), capable of selective growth in polymer amorphous and crystalline phases with distinct color. The polymorphic behaviors of the AIE luminogen embedded within the polymer network are dependent on the size of nano-confinement: a thermodynamically stable polymorph of the AIE luminogen with green emission is stabilized in the amorphous phase, while a metastable polymorph with yellow emission is confined in the crystalline phase. The information on polymer crystalline and amorphous phases is transformed into distinct fluorescence colors, allowing a single AIE luminogen as a fluorescent marker for visualization of polymer microstructures in terms of amorphous and crystalline phase distribution, quantitative polymer crystallinity measurement, and spatial morphological arrangement. Our findings demonstrate that confinement of the AIE luminogen in the polymer network can achieve free space recognition and also provide a correlation between microscopic morphologies and macroscopic optical signals. We envision that our strategy will inspire the development of other materials with spatial confinement to incorporate AIE luminogens for various applications.

A polymorphic AIEgen is capable of selective growth in amorphous and crystalline polymer phases with distinct color for microstructure visualization.     

Crosslinking photosensitized by a ruthenium chelate as a tool for labeling and topographical studies of G-protein-coupled receptors

The purpose was to apply oxidative crosslinking reactions to the study of recognition and signaling mechanisms associated to G-protein-coupled receptors. Using a ruthenium chelate, Ru(bipy)(3)(2+), as photosensitizer and visible light irradiation, in the presence of ammonium persulfate, we performed fast and efficient covalent labeling of the B(2) bradykinin receptor by agonist or antagonist ligands possessing a radio-iodinated phenol moiety. The chemical and topographical specificities of these crosslinking experiments were investigated. The strategy could also be applied to the covalent labeling of the B(1) bradykinin receptor, the AT(1) angiotensin II receptor, the V(1a) vasopressin receptor and the oxytocin receptor. Interestingly, we demonstrated the possibility to covalently label the AT(1) and B(2) receptors with functionalized ligands. The potential applications of metal-chelate chemistry to receptor structural and signaling studies through intramolecular or intermolecular crosslinking are presented.     

Theoretical analysis of the influence of the adosorption process on the voltammetric curves in the case of a second order adsorption step followed by a first order charge transfer reaction: Part II. Comparison between linear potential sweep voltammetry and steady state cyclic voltammetry

The voltammetric curves for a 2-step sequential reaction involving a 2nd order adsorption process (such as the catalytic mechanism met in the anodic oxidation of hydrogen) are investigated theoretically by computer calculations. Steady state cyclic voltammetry (s.s.c.v.) is particularly treated by repeating forward and backward sweeps as many times as necessary to reach the steady state. For both l.p.s.v. and s.s.c.v., the usual characteristic features are considered, i.e. E_M, θ_M, i_M as a function of sweep rate υ, especially in the range of υ, where the computed data fit the results derived from analytical solution (quasi-reversible charge transfer, and irreversible charge transfer). In s.s.c.v., indications are given to obtain the kinetic parameters (k₁, k₂, α) from experimental plots.