Helically chiral functionalized [6]helicene: Synthesis,optical resolution,and photophysical properties

A short and efficient synthetic pathway leading to a new chiral π-conjugated system is reported. The X-ray structure of the target compound was determined and showed a helical conformation. Its resolution was successfully accomplished, leading to two enantiomers in high optical purity, and their chiroptical properties were examined experimentally. The photophysical properties of the organic material were also evaluated, showing an emission in the visible region, and HOMO and LUMO levels have been estimated experimentally, demonstrating an electrochemical band gap of 2.37 eV.     

氯氰菊酯光敏降解中单线态氧机理研究

光敏剂亚甲兰,核黄素及玫瑰红Ｂ可加速氯氰菊酯（ＣＰＭ）的光解作用。这些物质的敏化作用主要通过激发基态氧为单线态氧来实现。光敏剂和氧均是敏化光降解不可缺陷少的条件。１／Ｋｅｘｐｔｌ与「Ａ」的关系证实了单线态氧氧化机理。在亚甲兰、核黄素存在下氯氰菊酯ＫＡ分别为６．４９＊１０＾６ｌ．ｍｏｌ＾－１．ｓ＾－１和２．２７＊１０＾６Ｌ．＾－１。氯氰菊酯的光解速率在一定范围内,随光敏剂浓度的增加而增加,过量的光敏剂将减少体系的透光率而导致氯氰菊酯光解速率降低,单线态氧探针性物质即竞争反应的引入将明显降低氯氰菊酯的光解速率,同时,不同极性溶剂因其对单线态氧猝灭能力的不同也会明显改变氯氰菊酯的光解速率。     

亚硝酸甲酯光解反应的从头算和Cl研究

用从头算和MP2方法求得亚硝酸甲酯的基态、第一和第二激发态解离为CH₃O和NO自由基的解离能分別为238.14、68.99和-183.97kJ/mol,而CH₃O和NO易于生成甲醛和硝酰。由CI方法求出的亚硝酸甲酯直接生成甲醛和硝酰的基态和激发态反应曲线表明,该反应难以按这种机理进行。因此,以上计算支持了实验提出的亚硝酸甲酯光反应生成甲醛和硝酰的两种机理中的光解离机制。     

UV光谱研究[Cp-Fe-Cp]BF4和[Cp-Fe-Naph]BF4的光解动力学及机理

本文测定了两种新型阳离子光聚合引发剂二茂铁四氟硼酸盐（[Cp-Fe-Cp]BF4)和环戊二烯基－铁－萘四氟硼酸盐（[Cp-Fe-Naph]BF4)在二氯甲烷和环氧氯丙烷中的紫外－可见吸收光谱，研究了紫外光照射对吸收光谱的影响，通过实时紫外－可见吸收光谱分析，研究了两种光引发剂在环氧氯丙烷中的光解动力学。发现二者的吸收光谱随光照时间的变化规律一致，而且光解反应均为一级反应，速率常数分别为0.72和0.65min^-1，从而提出了二茂铁四氟硼酸盐的光引发机理。     

间-吡啶基紫外光化学中的氢原子解离通道

利用高里德堡态氢原子飞行时间探测技术, 在224～248 nm激发波长研究了间-吡啶基紫外光化学中的氢原子解离通道的动力学过程．氢原子光解碎片产率谱显示在234 nm附近有较宽的吸收．产物的平动能释放较小;在224～248 nm激发波长区间平均< f_T>是0.12～0.19．产物的平动能分布显示产物是H+HC≡C-CH=CH-C≡N,H 3,4-吡啶和H 2,3-吡啶,以H HC≡C-CH=CH-C≡N为主要的氢原子生成通道．氢原子碎片具有各向同性的角度分布．研究结果表明,在紫外电子态激发以后,间-吡啶基经过内转换到电子基态,再经由单分子解离到H HC≡C-CH=CH-C≡N,H 3,4-吡啶和H 2,3-吡啶产物．间-吡啶基的紫外光解机理和以前报道过的邻-吡啶基的紫外光解机理相似．     

Ultraviolet Photolysis and Ortho-Phthalaldehyde-Mercaptoethanol Derivatization of Pharmaceuticals for Enhanced Fluorescence Detection in HPLC

Abstract

Several classes of nitrogenous pharmaceutical were examined for fluorescence after ultraviolet (UV) radiation induced photolysis followed by reaction with o-phthalaldehyde-2-mercaptoethanol (OPA-MERC), and after UV photolysis alone. Photolyses were examined in water, mixtures of methanol/water (1:1), and acetonitrile/water (1:1). Acetone was assessed as a photosensitizer to enhance photolysis and fluorescence response. Flow injection analysis and high-performance liquid chromatographic techniques were used for several pharmaceuticals. The analytes were subjected to UV photolysis and reaction with OPA-MERC reagent for generation of fluorophores that responded to fluorescence detection. During photolysis, solvent type as well as the presence of photosensitizers seem to play a significant role in the formation of primary amines and fluorophores. Photochemical transformation products of some of the pharmaceutical chemicals are proposed. Analytical figures of merit were determined for some analytes. This fluorescence detection approach is applicable for a number of pharmaceuticals at nanogram level.     

Synthesis and characterization of phenanthrene derivatives for optoelectronic applications

New phenanthrene derivatives, bearing cyano group at selected positions, have been prepared in good yields through Knoevenagel condensation and classical oxidative photocyclization. The optical properties of the cyanophenanthrenes have been investigated by UV–vis absorption. A cyclic voltammetry analysis showed a relatively high electronic affinity, indicating that they may be good candidates for electron-injection hole blocking layers in organic light-emitting diodes.     

Synthesis and photolytic evaluation of a nitroindoline-caged glycine with a side chain of high negative charge for use in neuroscience

A photolabile precursor of the neuroinhibitory amino acid glycine has been synthesised with two phosphate groups attached to the indoline nucleus at a 4-alkoxy substituent. In common with the photochemical properties of other 1-acyl-7-nitroindolines, this releases glycine on a sub-μs time scale upon irradiation with near-UV light. The synthetic route previously developed for the preparation of the GABA analogue required some modifications because of the greater hydrolytic sensitivity of the glycine compound. The phosphorylation method used here could be beneficial to the synthesis of other nitroindoline-caged amino acids, especially the related caged GABA derivative. Glycine released by laser photolysis on spinal cord neurons generated fast-rising responses and the pharmacological properties of the reagent are such that it is useful for physiological experiments.     

Two-photon uncaging of bioactive compounds: Starter guide to an efficient IR light switch

Triggering physiological responses with a light switch has become a reality with the development of smart molecular probes such as photolabile protecting groups (PPGs), able to “uncage” biological ligands on demand. To make the light switch virtually harmless and confine the excitation to the single-cell level, the caged ligands can be released using two-photon (2P) absorption and 2P microscopy using red/infrared light. This exceptional level of precision however comes at the cost of a reduced photosensitivity and a poor compatibility of early PPGs with 2P excitation. This review aims to provide a tutorial guidebook to the design of 2P-sensitive PPGs suitable for optobiology by discussing challenges, strategies and progress in uncaging of bioactive compounds. To do so, we first recall the photo-physical principles governing 2P absorption, and the resulting ground rules in the design of efficient 2P absorbing organic dyes. We then detail how following these guidelines has led to tremendous progress in the development of a new generation of caged compounds, and the implications in the fields of biophotonics, from neurology to targeted therapy.