Porphyrin-based switchable molecular turnstiles

The design, synthesis and structural characterisation, in solution, of two new molecular turnstiles based on Sn-porphyrin derivatives are described. The system is composed of a stator (5-(4-pyridyl)-10,15,20-triphenylporphyrin), a hinge (Sn(IV)) and a rotor (handle equipped with 2,6-pyridinedicarboxamide as a tridentate coordinating site or its Pd(II) complex). The presence of interaction sites, both on the stator and the rotor, offers the possibility of switching between an open state (free rotation of the handle around the porphyrin) and a closed state (blockage of the rotation) by either establishment of hydrogen bonds between the stator and the rotor or by the simultaneous binding of Pd by both coordinating groups.     

分子陀螺的设计、合成与组装

近来,科学家设计和合成了系列分子水平的陀螺。类似于儿童的玩具陀螺仪,这种分子陀螺由一个转子、一个定子框架和连接定子和转子的轴组成。定子框架通过自身的刚性结构为中心转子的转动提供足够的内在自由度,得以对内部的转子实施保护。并使得分子陀螺成为一个理想的分子转子。当转子上有偶极距时,则可能在外来电、磁、光的刺激下进行定向转动,成为分子马达。化学家们通过X射线晶体衍射技术、动态核磁技术、理论计算化学、热力学分析等方法表征了分子陀螺的各种特征,并积极探索其潜在的应用价值。本文着重介绍分子陀螺,以及超分子陀螺仪的发展历史以及研究进展。     

分子旋转对分子器件电子输运性质的影响

利用基于非平衡格林函数和密度泛函理论相结合的第一性原理计算方法,研究了一种可旋转分子跨接在金电极上的电子输运性质。计算结果表明:分子中的转子与定子间的旋转角度可以有效调控分子器件的电子输运性质。当夹角从30°变化到150°,分子器件的导电性呈现出增强、减弱的震荡变化。此外,当夹角变化到90°,分子器件的电流电压曲线打破其他角度呈现的线性变化特性,其电流值在2.4 V以后随着电压的增大而减小,表现出强烈的负微分电阻效应。     

An oscillating molecular turnstile

An oscillating molecular turnstile based on a stator composed of a porphyrin core bearing two trans coordinating pyridyl units at the meso positions and a rotor equipped with a pyridyl group was designed. Whereas, in solution, the rotor freely rotates around the stator, in the presence of a silver cation behaving as an effector, the system oscillates between two stations. The oscillatory movement may be frozen upon cooling at -70 °C generating thus the closed state of the turnstile. The switching of the system between the open and closed states may be achieved using an external stimulus such as addition of Et(4)NBr.     

Open and closed states of a porphyrin based molecular turnstile

The molecular turnstile 1 composed of a stator based on an Sn(IV)-porphyrin bearing two sets of monodentate coordinating sites (pyridyl and benzonitrile) and a handle bearing a 2,6-pyridinediamide moiety as a tridentate unit was synthesised. In the absence of metal behaving as a blocking agent, the handle freely rotates around the stator (open state). In the presence of Pd(II), the closed state of the turnstile 1-Pd resulting from the simultaneous binding of the metal centre by both the dianionic tridentate site and one of the two pyridyl units is generated. The reaction of 1-Pd with the organometallic 2,6-diphenylpyridine Pt(II) complex 11 leads to the heterotrinuclear (Pt, Sn, Pd) species 13, resulting from the binding of the platinum complex by 1-Pd.     

The modeling and simulation of the thermal analysis on the hydrogenerator stator winding insulation

This paper presents the modeling and simulation of the thermal analysis on the hydrogenerator stator winding. The insulation aging is predetermined first by the insulation temperatures that, in turn, are influenced by the environmental conditions and second by the speed increase of the high temperature chemical reaction in materials. By increasing the temperature in the electro-insulated material, many molecules enter in chemical reaction accelerating the insulation aging. The heat transfer is a natural process, caused by inner energy, between bodies with high temperature and bodies with lower temperature. This process can also take place between parts of the same body that have different temperatures. The heat is transmitted by conduction, convection, and radiation. The heat transfer and especially the thermal conduction are a domain in which the finite element method is successfully applied. The thermal conduction problems will be solved by the finite elements method. The analysis of the thermal transfer process was made using the modeling and simulation program with finite elements ANSYS, and the results of the simulations were compared with measurement values. The analyzed stator winding is supplied with high voltage of 11 kV that is used for a high power hydrogenerator. To realize the thermal analysis of the winding stator, the coil will be supplied with 11 kV. The results of the analysis on a prototype model present the thermal transfer in coil–insulation–air system when the coil is hot.     

Ventilation modes and greenhouse structures affect 222Rn concentration in greenhouses in China

The influences of ventilation modes and greenhouse structures on radon concentrations in single- and multi-span plastic film greenhouses were studied to find effective engineering measures for controlling indoor radon by numerical simulation. The plants and mulch on ground, and sealing conditions had been considered to ensure the accuracy of simulation. Ventilation mode obviously influenced the indoor radon concentration and distribution, while the ventilation wind speed and structural form exerted no clear influence. Mechanical ventilation could reduce radon concentration to a greater extent than natural ventilation, and side-face ventilation was superior to end-face ventilation.

     

中学化学实验室气体环境的实测研究

对中学化学学生实验活动中产生的气体污染物进行测试,得到不同通风条件下化学实验室内部空气污染物的数据。结果表明,中学化学学生分组实验产生的主要气体污染物有苯、甲苯、甲醛、氨气等,实验过程中如不采取任何通风措施,实验室气体污染物的浓度短时间内会急剧升高,所以采取有效措施对实验室内部空气污染物进行消除是非常必要的。目前中学化学实验室配备的通风设备以桌面排风设备为主,相比于自然通风的环境,学生实验时开启桌面排风设备,能够有效降低实验产生的气体污染物浓度。     

Influence of ventilation on the reduction of the radon concentration in an underground research facility

The concentration of radon in an underground research facility (URF) was measured by setting up 12 sampling points in the URF and with 3 different measurement methods. All the methods were calibrated in the radon laboratory of the No. 6 Institute of Nuclear Industry. The accumulation of radon in the URF was observed before a ventilation system was applied. The reduction of radon concentration in the URF by 1-hour ventilation was also observed. Experimental result indicates that the concentration of radon in the URF increased from 15 to 50 Bq·m⁻³ in 5 days without ventilation, and decreased to less than 10 Bq·m⁻³ with 1-hour ventilation. Applying the average working time of 4 hours per day of the workers in the URF, the additional effective dose is 0.75 msv·y⁻¹ when 1 hour ventilation is applied before entering the URF and 13 mSv·y⁻¹ without ventilation. These figures strongly suggest that for the health of the workers, ventilation in such underground research facilities is needed.     

Molecular Turnstiles Featuring Bicyclic Rotators: Solution and Solid-State Investigation of Steric and Electronic Concerns

A molecular rotor is created when a 2,1,3-benzothiadiazole rotator is incorporated into a rigid arylene ethynylene framework supported by pyridine coordination to a metal (Ag⁺ or PdCl₂) guest. Comparisons to a similarly sized naphthyl rotator via ¹H NMR spectroscopy provide insights into the movement of these bicyclic rotators relative to the rigid stator framework. Chemical shift increases of 0.3 ppm, or more, upon metal complexation are consistent with through-space interaction of the central arene with a bound PdCl₂ guest. Further study via X-ray crystallography illustrates that rotation of the 2,1,3-benzothiadiazole unit in the solid state is likely hampered by relatively strong chalcogen bonding (N⋅⋅⋅S distance of 2.93 Å), forming 2S-2N squares between benzothiadiazoles of neighboring complexes. Strong π–π interactions (3.29–3.36 Å) between neighboring complexes likewise restrict solid-state rotation of the potential benzothiadiazole rotator. Modest changes to UV–vis spectra upon metal coordination suggest that electronic properties are mostly independent of stator configuration.     

Mise en évidence expérimentale de la sensibilité de l'écoulement de type rotor-stator aux effets de bord

Experimental investigation of the external peripheral geometry effects in a rotor-stator system has brought to light the strong influence on the flow structure of a small difference between the disc radii: two distinct regimes can be observed. At given values of the Reynolds number and aspect ratio the flow field is in agreement with the infinite dises solution as soon as the ratio of the stator and the rotor radii becomes sufficiently large.     

A study on the clearance of metal frames of waste filters from ventilation system in nuclear power plant

Journal of Radioanalytical and Nuclear Chemistry - The ventilation filters from ventilation system in the control area of nuclear power plant will be regularly replaced. In general, the metal frame...     

Configurational and Constitutional Dynamics of Enamine Molecular Switches

Dual configurational and constitutional dynamics in systems based on enamine molecular switches has been systematically studied. pH-responsive moieties, such as 2-pyridyl and 2-quinolinyl units, were required on the „stator“ part, also providing enamine stability through intramolecular hydrogen-bonding (IMHB) effects. Upon protonation or deprotonation, forward and backward switching could be rapidly achieved. Extension of the stator π-system in the 2-quinolinyl derivative provided a higher E-isomeric equilibrium ratio under neutral conditions, pointing to a means to achieve quantitative forward/backward isomerization processes. The „rotor“ part of the enamine switches exhibited constitutional exchange ability with primary amines. Interestingly, considerably higher exchange rates were observed with amines containing ester groups, indicating potential stabilization of the transition state through IMHB. Acids, particularly Bi^III, were found to efficiently catalyze the constitutional dynamic processes. In contrast, the enamine and the formed dynamic enamine system showed excellent stability under basic conditions. This coupled configurational and constitutional dynamics expands the scope of dynamic C−C and C−N bonds and potentiates further studies and applications in the fields of molecular machinery and systems chemistry.     

Multiple hindered rotators in a gyroscope-inspired tribenzylamine hemicryptophane

A gyroscope-inspired tribenzylamine hemicryptophane provides a vehicle for exploring the structure and properties of multiple p-phenylene rotators within one molecule. The hemicryptophane was synthesized in three steps in good overall yield using mild conditions. Three rotator-forming linkers were cyclized to form a rigid cyclotriveratrylene (CTV) stator framework, which was then closed with an amine. The gyroscope-like molecule was characterized by (1)H NMR and (13)C NMR spectroscopy, and the structure was solved by X-ray crystallography. The rigidity of the two-component CTV-trismethylamine stator was investigated by (1)H variable-temperature (VT) NMR experiments and molecular dynamics simulations. These techniques identified gyration of the three p-phenylene rotators on the millisecond time scale at -93 °C, with more dynamic but still hindered motion at room temperature (27 °C). The activation energy for the p-phenylene rotation was determined to be ~10 kcal mol(-1). Due to the propeller arrangement of the p-phenylenes, their rotation is hindered but not strongly correlated. The compact size, simple synthetic route, and molecular motions of this gyroscope-inspired tribenzylamine hemicryptophane make it an attractive starting point for controlling the direction and coupling of rotators within molecular systems.     

热脱附/气相色谱–质谱法检测新装修房内不同状态空气中TVOC比对

采用热脱附/气相色谱–质谱联用方法对两套新装修房(完工2个月和4个月)进行通风、封闭1 h、连续使用家用空调5 h 3种状态下总挥发性有机物TVOC进行检测。结果显示完工2个月的新装修房间封闭1 h TVOC含量比通风状态增加5倍,而连续开启家用空调5 h后室内TVOC含量比通风状态增加7.9倍;完工4个月的新装修房封闭房间1 h TVOC含量比通风状态增加0.5倍,而连续开启家用空调5 h后室内TVOC含量比通风状态增加2.5倍;污染程度不同的房间在使用空调后TVOC含量也有不同的变化。     

Switching around two axles: controlling the configuration and conformation of a hydrazone-based switch

A hydrazone-based rotary switch, having a quinolinyl stator and a pyridine ring as part of the rotor, can be induced using pH to undergo a four-step switching sequence. This process yields three stable isomers and a fourth "metastable" one that can all be addressed separately based on the sequence of acid and base added. The switching process proceeds via conformational and/or configurational changes, allowing the molecule to rotate around two different axles.     

Computational Insight to Improve the Thermal Isomerisation Performance of Overcrowded Alkene‐Based Molecular Motors through Structural Redesign

Synthetic overcrowded alkene‐based molecular motors achieve 360° unidirectional rotary motion of one motor half (rotator) relative to the other (stator) through sequential photochemical and thermal isomerisation steps. In order to facilitate and expand the use of these motors for various applications, it is important to investigate ways to increase the rates and efficiencies of the reactions governing the rotary motion. Here, we use computational methods to explore whether the thermal isomerisation performance of some of the fastest available motors of this type can be further improved by reducing the sizes of the motor halves. Presenting three new redesigned motors that combine an indanylidene rotator with a cyclohexadiene, pyran or thiopyran stator, we first use multiconfigurational quantum chemical methods to verify that the photoisomerisations of these motors sustain unidirectional rotary motion. Then, by performing density functional calculations, we identify both stepwise and concerted mechanisms for the thermal isomerisations of the motors and show that the rate‐determining free‐energy barriers of these processes are up to 25 kJ mol^?1 smaller than those of the original motors. Furthermore, the thermal isomerisations of the redesigned motors proceed in fewer steps. Altogether, the results suggest that the redesigned motors are useful templates for improving the thermal isomerisation performance of existing overcrowded alkene‐based motors.     

测试因素对一次性医用口罩通气阻力的影响

针对一次性医用口罩(DMMs)通气阻力测试结果不稳定情况,从测试设备稳定性、气体流量、样品不同位置、气流方向、预处理、测试时间方面展开了研究。结果表明,气体流量、样品不同位置和预处理对口罩的通气阻力有较大影响,测试时间和气流方向对口罩通气阻力无明显影响。研究结果对各生产厂商开发优异DMMs及生产过程质量控制有重要意义。     

An analysis of regional ventilation in pulmonary sarcoidosis by inspired 133Xe washout test

Xenon-133 ventilation study were used to measure regional ventilation in seven patients with pulmonary sarcoidosis and in four normal subjects. For the purpose of analyzing the washout curves on the whole lungs, two ventilation indexes were calculated, which were TA/H and T1/2. TA/H is that the area under the curve divided by the difference in mean count rate during equilibrium and at 120 s after washout started. T1/2 value represents the time required to 50% of the mean count rate during equilibrium. The average time of TA/H on the whole lung was 13.5 +/- 1.1 s in normal subjects (n = 4), 13.0 +/- 4.3 s in stage I (bilateral hilar lymphadenopathy without lung involvement on chest X-ray) sarcoidosis (n = 3), 21.3 +/- 1.8 s in stages I, II (lung involvement) sarcoidosis (n = 4). The average time of T1/2 on the whole lung was 43.7 +/- 4.7 s in normal subjects, 42.3 +/- 16.0 s in stagel sarcoidosis, 72.5 +/- 28.6 s stages II, III sarcoidosis. The ventilation indexes on the regional lungs showed almost a similar tendency to that on the whole lung. The ventilation indexes in patients with stage II, III sarcoidosis were significantly longer than in normal subjects and in patients with stage I sarcoidosis. It was suggested that 133Xe washout test might detect regional ventilation abnormalities which were not recognized on chest X-ray in pulmonary sarcoidosis.     

Effect of structural parameters on the flow field and power consumption of in-line high shear mixer

The effects of three structural parameters on flow field and power consumption of in-line high shear mixer (HSM) were investigated by large eddy simulation (LES). In addition, an artificial neural network (ANN) is used to predict the relationship between the structural parameters and the power consumption, and the effect of dimensionless structural parameters on the power number constant Poz and k1 is studied. The results show that the stator tooth thickness and the tooth tip-base distance have a slight effect on the flow field, and the shear gap width is a key parameter affecting the flow field. As the stator teeth thickness, the tooth tip-base distance and the shearing gap width increases, the power number Po decreases. There is a linear relationship between the constant k₁ and the dimensionless structural parameters. With the increase of the dimensionless parameter Ts/Ds-o of the stator tooth thickness, the dimensionless parameter St/H of the tooth tip-base distance, and the dimensionless parameter Sg/DR-o of the shear gap width, the constant k₁ decreases. With the increase of the parameter St/H, Sg/DR-o and Ts/Ds-o, the constant Po_z first increases and then decreases. There is a linear relationship between the constant Po_z and the parameter Ts/h. With the increase of the parameter Ts/h, the constant Po_z increases.