Excited State Isomerization of Small Polyeneiminium Ions - The Influence of Initial Torsion and Methyl Substitution on Md-Calculated Reaction Dynamics

Ultrafast photochemical reactions are assumed to progress via a direct crossing of the potential energy surfaces of the ground and excited state. Simulations on an adiabatically corrected Born-Oppenheimer surface of the first excited state of the 3- cis -penta-3,5-dieniminium cation and its 2-methyl derivative form have been performed with high level CASSCF methodology and a modified MD routine to study the cis-trans isomerization of the central double bond. The calculations show that the dynamics depend not only on the slope of the potential energy surface with its two dominant degrees of freedom, double bond stretching and rotation. For fast isomerization an effective coupling of these modes is also necessary. Methyl substitution and an additional initial twist can significantly accelerate this process. The interrelationship between the stretching and torsional modes is discussed in detail.     

Review of the recent progress in photoresponsive molecularly imprinted polymers containing azobenzene chromophores

Photoresponsive molecularly imprinted polymers (PMIPs) containing azobenzene have received wide research attention in recent years and made notable achievements. This article reviews the recent developments on PMIPs containing azobenzene. Topics include the following: (i) brief introduction of azobenzene, molecularly imprinted polymers, and PMIPs containing azobenzene; (ii) progress in functional monomers, cross-linkers, and polymerization conditions; (iii) preparation methods, properties, applications, as well as advantages and disadvantages of conventional PMIPs; (iv) substrate, preparation method, and applications of photoresponsive surface molecularly imprinted polymers; and (v) some perspectives for further development of PMIPs containing azobenzene.     

IR125和HDITCP在不同烷基链长阳离子离子液体中的光异构化动力学

利用稳态吸收和荧光光谱以及时间相关单光子计数实验,分别测得近红外花菁分子IR125和HDITCP在不同烷基链长阳离子离子液体中的荧光量子产率和荧光寿命,并通过计算获得了它们各自在相应离子液体中的光异构化速率.发现IR125和HDITCP在不同离子液体中的光异构化速率没有随着离子液体粘度的增大而产生明显变化.与IR125和HDITCP在与离子液体具有相同粘度的甘油水溶液中的光异构化速率对比,发现IR125和HDITCP在离子液体中的光异构化能垒比它们在甘油水溶液中的光异构化能垒增大约2 kJ?mol-1,这表明在高粘度的离子液体中IR125或HDITCP与离子液体之间特殊的相互作用会阻碍它们各自的光异构化过程.     

Design and synthesis of azobenzene template based sulfonamide for capture of HCAII: dependence of efficiency on E–Z geometry

We report the synthesis of azobenzene template based sulfonamides 1 and 2 for capture of Human Carbonic Anhydrase II (HCAII). Out of these, 1 showed successful capturing of the protein, only when it is photo-isomerized to the Z form thus demonstrating the importance of spatial proximity of the reactive and selective functionalities.     

通过构象诱导电感耦合机制光可逆调控有机场效应晶体管的性能

将有机场效应晶体管用于传感和开关实际应用的主要阻碍之一是其破坏性传感机制产生的一系列问题. 这里我们报道了一种智能的系统, 用光致变色分子螺吡喃(SP)和聚甲基丙烯酸甲酯(PMMA)结合作为栅介电材料, 得到的器件能以一种无损的方式, 通过光可逆调控器件的导电性能. 当螺吡喃分子发生可逆的光学异构时, 器件的电容和导电性随之发生显著而可逆的变化. 这种构象诱导电感耦合的作用机理提供了一种制备功能器件的新方法, 可以推广为利用其它刺激响应型分子来制备特定功能器件的普适性方法.     

Synthesis and photo activity of phenylazonaphthalene peptide nucleic acid monomers

Phenylazonaphthalene peptide nucleic acid （PNA） monomers were successfully synthesized, and their photoisomerization was examined. The new PNA monomers showed reversible trans-cis isomerization with UVand visible light irradiation, which might be the foundation of photo-regulating the hybridization between PNA containing phenylazonaphthalene unit and DNA. Simultaneously, the fluorescence of the new PNA monomers might make them especially useful as structural probes.     

Effect of opsin on the shape of the potential energy surfaces at the conical intersection of the Rhodopsin chromophore

In order to disentangle the role of the protein in the control of the photoisomerization of the chromophore of the visual pigment Rhodopsin, we compare the structure of the ground and excited potential energy surfaces of gas-phase and opsin-embedded 11-cis retinal chromophore at the corresponding (lowest energy) conical intersections. It is shown that, along the branching plane, the asymmetric opsin environment destabilizes one of the ground state relaxation channels emerging from the conical intersection. This suggests that opsin promotes the formation of the product (bathorhodopsin) via enhanced decay probability along the all-trans exit channel. In contrast, in the gas-phase no significant structural difference has been found for the channels that lead towards the 11-cis or all-trans forms of the chromophore.     

Trans-cis photoisomerization of azobenzene by n→π* excitation:A semiclassical dynamics study

A realistic dynamics simulation study is reported for the trans-cis photoisomerization of azobenzene triggered by the n→π*excitation and the results show that the formation of cis isomer follows the rotational motion around the N=N bond.The simulation find that the CNN bond angle bending vibrations also play a significant role in the vibronic coupling between the HOMO and LUMO,which essentially leads a nonadiabatic transition of the molecule to the electronic ground state.     

噁唑体系激发态质子转移和失活的理论研究

利用高精度的CASSCF和MS-CASPT2电子结构计算方法系统地研究了2-(2'-羟基苯基)-4-甲基噁唑的光物理和光化学机理. 在CASSCF级别,首先优化得到势能面极小结构和圆锥交叉结构,及激发态质子转移、异构化、和失活的极小能量路径. 然后用MS-CASPT2方法对所有得到的结构和能量路径进行单点能量校正,我们发现在含有OH…N氢键的构象异构体中,激发态质子转移基本上是一个无垒的过程;在含OH…O 氢键的构象异构体中,激发态质子转移被抑制了. 此外,找到两个能量较低的酮式S₁/S₀圆锥交叉结构,使得激发态质子转移生成的S₁酮式结构可以很快失活到达基态. 但是,醇式S₁/S₀圆锥交叉结构能量较高,抑制了S₁醇式结构的激发态失活.