The effect of temperature on the photoacidity of merocyanine photoacids in water

Merocyanine photoacids are molecular photoswitches that can be used to regulate acid-base reactions reversibly. Despite their growing impact across multiple research areas including materials science and nanotechnology, the effect of temperature on their functioning in aqueous environments has not yet been explored. Here we employ variable-temperature pH and UV-Vis analyses to rationalize their temperature-dependent (photo)chemical behaviors in water, showing that their photoacidity is inversely proportional to the temperature (by ca. ?0.01 pK/°C).     

Photo-, solvent-, and ion-controlled multichromism of imidazolium-substituted diarylethenes

Cationic diarylethenes with an imidazolium ring are synthesized for the first time. The imidazolium cationic moiety is connected directly to the ethene unit as one of the aryl units that take part in the photoinduced pericyclization reaction. The imidazolium-substituted diarylethenes undergo reversible photochromic reactions in a variety of organic media, including ionic liquids, even though they have a delocalized cationic charge in one of the five-membered aromatic rings. The closed-ring isomer shows solvatochromism depending on the solvent donor numbers. Addition of some tetraalkylammonium salts, such as tetrabutyl ammonium nitrate, into the colored organic solution of diarylethene also causes a color change, indicating its ionochromic property. These solvato- and ionochromic properties are considered in connection with the shift of chemical equilibrium between the closed-ring isomers, one with an extended pi-conjugation system and one with limited pi-conjugation due to the strong interaction with solvent molecules and anions with high donor number.     

Acid–Base Controllable Recognition Properties of a Highly Versatile Calix[6]crypturea

Versatile concave receptors with binding properties that can be controlled by external stimuli are rare. Herein, we report on a calix[6]crypturea ( 1 ) that features two different binding sites in close proximity, that is, a tris(2‐aminoethyl)amine (tren)‐based tris‐ureido cap that provides convergent hydrogen‐bond‐donor sites and a hydrophobic cavity suitable for the inclusion of organic guests. The binding properties of this heteroditopic receptor have been evaluated by NMR spectroscopic studies. Compound 1 behaves as a remarkably versatile host that strongly binds neutral molecules, anions, or contact ion pairs. Within each family of guests, compound 1 is able to discriminate between different guests with a high degree of selectivity. Indeed, neutral molecules that possess hydrogen‐bond donor and acceptor groups, chloride anions, and linear ammonium ions associated to F^? or Cl^? are particularly well recognized. In comparison with all the related receptors, compound 1 displays several unique features: 1) charged or neutral species are also recognized in polar or protic solvents, 2) thanks to the flexibility of the calixarene structure, induced‐fit processes allow the binding of large, biologically relevant ammonium salts such as neurotransmitters, and 3) the protonation of the basic cap leads to a positively charged receptor, 1? H⁺, which is reluctant to host anions and in which host properties are now governed by strong charge–dipole interactions with the guests. In other words, compound 1 presents an acid–base controllable tris‐ureido recognition site protected by a hydrophobic corridor that can select guests through induced‐fit processes. Thus, its versatile host properties can be allosterically controlled by protonation and selective guest‐switching processes are possible. To illustrate all these remarkable features, a sophisticated three‐pole supramolecular switch, based on the interconversion of host–guest systems displaying either charged or neutral guests, is described.     

稳定性切换在一阶时滞微分方程中的应用

介绍了时滞动力系统中的对零解稳定性讨论的稳定性切换法,并应用此方法对时滞动力系统中的三个一阶时滞微分方程基本定理给予证明.同时表明了在局部稳定性分析中,该方法有着更大的优势.     

A Visible‐Light‐Driven Molecular Motor Based on Pyrene

The aromatic core of an overcrowded alkene‐based molecular motor is extended with the goal of inducing isomerization with visible light instead of harmful UV light. In our design, the common naphthalene moiety in the upper half of the motor is changed to pyrene. The photochemical and thermal isomerization processes are studied in detail using DFT calculations as well as NMR and UV/VIS spectroscopy. Our studies confirm that extension of the π‐system of the upper half successfully leads to a shift of the excitation wavelength into the visible region, while retaining proper rotary function.     

Photoswitchable double bonds: Synthetic strategies for tunability and versatility

Isomerizations of azo, imine, and alkene groups using light are highly tunable. As such, photoswitches based on these functional groups have become critical components of many responsive molecules and materials. This mini‐review describes recent work focused on controlling various properties of double bond‐based molecular switches, including speed of switching, thermal stability, and wavelength required to initiate switching. Methods used to control structure and function vary, but commonly involve careful probing of the electronic, photochemical, and steric profiles of the molecular switches. Successes and avenues for further investigation will be discussed.     

聚合物2×2定向耦合型电光开关

设计并制作了一种聚合物2×2定向耦合型电光开关.针对溶胶-凝胶法合成的有机/无机杂化电光材料膜厚较薄的情况,采用一种加载条形波导结构,利用掺有环氧丙脂的聚甲基丙烯酸甲脂-甲基丙烯酸缩水甘油脂作为引导层,在电光薄膜上构成定向耦合器,通过紫外光刻、反应离子刻蚀、电晕极化等工艺,制备了聚合物定向耦合型电光开关,并采用共面波导行波电极以电推挽方式工作.经测试,其器件损耗约为16 dB,开关电压9 V.     

基于接地开关理论的电流型多值CMOS电路设计

以开关信号理论为指导，对电流型CMOS电路中开关变量和信号变量的相互作用进行了分析，并引入了适用于CMOS电路的电源开关理论。基于接地电流开关理论，对几类重要的三值CMOS电路进行了设计。结果表明，应用该理论能获得简单的电路设计。从而进一步完善了开关级逻辑电路设计的研究。