硅胶固载光敏剂的合成及其在反式维生素D3光敏异构化为顺式维生素D3中的应用

采用丙二酸作为连接体,将9-蒽甲醇连接到硅胶上生成硅胶固载的光敏剂.利用此固相光敏剂分别在乙醇和甲苯溶液中敏化反式维生素D₃.实验结果表明,此固相光敏剂能够有效地敏化反式维生素D₃为顺式维生素D₃的反应,并且非常容易从反应体系中分离出来.     

Synthesis of a Polymer-bound Sensitizer and its Application in the Photoisomerization of trans-Vitamin D_3 to cis-Vitamin D_3

The photochemistry of the vitamin D family and their precursors has been the subject of extensive studies for many years1-4. Most of the studies focus on the photoisomer- ization of 7-dehydrocholesterol and that of tachysterol to previtamin D3, which is of commercial importance in the synthesis of vitamin D34, 5. Recently the cis/trans isomerization of vitamin D analogs (Scheme 1) draws attention because of its importance in the synthesis of hydroxylated vitamin D metabolites6. However, o…     

Effect of surfactant structure on catalysis of microemulsion for photoisomerization of trans-stilbene

In this study,the photoisomerization of trans-sfilbene was carried out in water in oil (W/O) microemulsions by using sodium dodecyl sulfate (SDS),dodecyl trimethyl ammonium bromide (DTAB) and cetyl trimethyl ammonium bromide (CTAB) as surfactant,respectively.The catalytic effect of microemulsion on this reaction is closely related to the structure of surfactant.When there is no photosensitizer 9,10-dicyanoanthracene (DCA),the surfactant with shorter hydrophobic chain is preferred,while in the presence of DCA,the surfactant with anionic polar group is preferred.     

The influence of sodium dodecyl sulfate/benzyl alcohol/H2O system on the photoisomerization of trans-stilbene

Photoisomerization of trans-stilbene (TS) was investigated in sodium dodecyl sulfate (SDS)/benzyl alcohol (BA)/H(2)O systems in order to establish the relationship between the reaction yields and the compositions and structures of molecular organized assemblies. The results show that, in SDS/BA/H(2)O systems with the structures of oil in water microemulsions, bicontinuous microemulsions, and hexagonal liquid crystals, the reaction yields are much larger than those in benzyl alcohol, both with and without the photosensitizer 9,10-anthracenedicarbonitrile. However, SDS/BA/H(2)O water in oil microemulsion and lamellar liquid crystal can obviously catalyze the photoisomerization of TS only when the photosensitizer is not present. The yield is increased with the increase in H(2)O content or with the decrease in BA content.     

First photosensitized enantiodifferentiating isomerization by optically active sensitizer immobilized in zeolite supercages

Enantiodifferentiating photoisomerization of (Z)-cyclooctene sensitized by (R)- or (S)-1-methylheptyl benzoate immobilized in zeolite supercages afforded the respective enantiomer pair, (-)- and (+)-(E)-isomer (1E) in 5% enantiomeric excess, whilst racemic 1E was obtained upon homogeneous-phase photosensitization with the same antipodal sensitizer pair, thus demonstrating for the first time that chirally modified zeolites not only serve as supramolecular photosensitizing media but also enhance the original enantiodifferentiating ability of chiral photosensitizer.     

Synthesis of self‐photosensitizing polyesters containing donor–acceptor norbornadiene moieties and benzophenone groups and their photochemical reactions

The ring‐opening copolymerization of a glycidyl ester derivative having a benzophenone group and the donor–acceptor norbornadiene (D‐A NBD) dicarboxylic acid, 5‐(4‐methoxyphenyl)‐1,4,6,7,7‐pentamethyl‐2,5‐norbornadiene‐2,3‐dicarboxylic acid, monoglycidyl ester derivatives with D‐A NBD dicarboxylic anhydride using tetraphenylphosphonium bromide as a catalyst proceeded smoothly to give novel self‐photosensitizing NBD polymers in good yields. The molecular weight of these polyesters was about 4,000, and lower than that of analogous NBD polymers having no benzophenone group. All the synthesized NBD polymers isomerized smoothly to the corresponding quadricyclane (QC) polymers upon UV irradiation in tetrahydrofuran (THF) solution and in the film state. The rate of the photoisomerization of the D‐A NBD moieties in these polymers was higher than that of the D‐A NBD moieties in the polymer having no photosensitizing group. Furthermore, the rate of the photoisomerization of the D‐A NBD moieties in these polymers was also higher than that of the NBD polymer with low molecular weight photosensitizer in dilute solution. The photo‐irradiated polymers having QC moieties released thermal energies of 146–180 J/g. The D‐A NBD moieties contained in these NBD polymers possessed fair to good fatigue resistance. The degradation of the NBD moieties in these polymers was 15–30% after 50 repeated cycles of interconversion. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 2978–2988, 2007     

Photo-induced structural changes of azobenzene Langmuir-Blodgett films

Structural changes of the Langmuir-Blodgett (LB) films of azobenzene accompanied by photoisomerization are described. First, photoisomerization is explained in terms of 'free volume'. In the polyion complex monolayers of amphiphiles having two azobenzene units at the air-water interface, the area per molecule depends on the polycation species. The fraction of cis-azobenzene in the LB films at the photostationary state under the illumination with UV light increased with increasing area per molecule, which is consistent with the concept of free volume. Second, a counter example of the concept of free volume is presented. Three-dimensional cone-shaped structures developed with trans-to-cis photoisomerization in the polyion complex LB film of a water-soluble amphiphilic azobenzene. These structures appeared and disappeared reversibly by alternate illumination with UV and visible light. The results indicate that the two-dimensional LB film structure exerts significant modification by photoisomerization. This is against the concept of free volume because this concept does not consider the possibility that the two-dimensional LB film structures may change into three-dimensional ones. Finally, photo-induced J-aggregate formation of non-photochromic and photochromic dyes is described. Two cyanine dyes were each mixed with an amphiphilic azobenzene in the LB films. These cyanine dyes are known to form J-aggregates in single-component LB films. In the mixed LB films, the J-aggregate formation was suppressed to some extent. The alternate illumination of the films with UV and visible light caused the photoisomerization of azobenzene in the mixed LB films, which triggered the J-aggregate formation of the cyanine dyes. The J-aggregate formation was accompanied by the development of three-dimensional cone-shaped structures from the film surface. When an amphiphilic merocyanine was mixed with the azobenzene in the LB films, J-aggregate formation was also induced by the alternate illumination with UV and visible light. This J-aggregate formation was also accompanied by a large morphological change: circular domains changed into fractal-like ones. The J-aggregate formation of the dyes and the concomitant morphological change were irreversible. In these cases, the photoisomerization of azobenzene served as a trigger to induce self-organization of the dye molecules.     

Comparison of photosensitizer (AIPcS2) quantification techniques: in situ fluorescence microsampling versus tissue chemical extraction

A noninvasive in situ fluorescence-based method for the quantification of the photosensitizer chloroaluminum disulfonated phthalocyanine was compared to the highly accurate but nonreal time ex vivo spectrofluorometry method. Our in vivo fluorescence technique is designed to allow real-time assessment of photosensitizer in tumor and normal tissues and therefore temporally optimal light delivery. Laser-induced fluorescence was used to measure photosensitizer concentration from multiple microscopic regions of tissue. Ex vivo chemical extraction was used to quantify photosensitizer concentration in the same volume of tissue. The amount of photosensitizer in the vascular and/or parenchymal compartments of skeletal muscle and liver was determined by quantifying fluorescent signal in vivo, ex vivo and after blood removal. Confocal microscopy was used to spatially document photosensitizer localization 30 min and 24 h after delivery. While a linear correlation can exist between the fluorescence intensity measured by our fiber-optic bundle system and actual tissue concentration, temporal changes to this calibration line exist as the photosensitizer changes its partitioning fraction between the blood (vasculature) and the tissue parenchyma. In situ photosensitizer fluorescence microsampling (dosimetry) systems can be performed in real time and linearly correlated to actual tissue concentration with minimal intertissue variance. Tissue-specific differences may require temporal alterations in the calibration.     

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.     

联有含氮艹/氐的2-吡唑啉化合物的光物理行为

合成了一种在(5)位上联有含氮的2-吡唑啉化合物，研究了该化合物分子所呈现的光敏顺-反异构化现象，并对其机理进行了考察，研究结果表明：具电子转移性质的该化合物顺-反异构化反应速率强烈的依赖于溶剂的极性。同时，光敏异构化还导致了该吡唑啉化合物荧光发射强度随光照时间而增大的有趣结果。     

Photochemical properties of amino and nitro derivatives of 2-and 4-styrylquinolines and their hydrochlorides

The trans-cis and cis-trans photoisomerization reactions of a double bond in nitro and amino derivatives of 2-and 4-styrylquinolines in the neutral and protonated (hydrochloride) forms were studied. Protonation in nitrostyrylquinolines was shown to have no effect on the photoisomerization quantum yields. In aminostyrylquinolines, the photoisomerization reaction is “switched off” for the monocationic form as a result of the competitive process of intramolecular charge transfer and is “switched on” again for the dication. In the latter case, the quantum yield of trans-cis photoisomerization decreases by a factor of 2–2.5 and the quantum yield of cis-trans photoisomerization remains practically unchanged as compared to that of the neutral compound. Upon long-term irradiation of 4-(4′-nitrostyryl)quinoline, the photocyclization reaction of the cis-isomer was observed.     

Photoisomerization locking of azobenzene by formation of a self-assembled macrocycle

Reaction of an azobenzene-linked biscatecholate ligand with boron and titanium sources gave ring- and cage-shaped complexes in a self-assembly fashion, respectively. These complexes were inert to photoisomerization though the ligand itself was isomerized upon photoirradiation. The self-assembled macrocyclization caused inhibition of the photoisomerization.     

联有含氮茋的2-吡唑啉化合物的光物理行为

合成了一种在（5）位上联有含氮的2-吡唑啉化合物，研究了该化合物分子所呈现的光敏顺-反异构化现象，并对其机理进行了考察，研究结果表明：具电子转移性质的该化合物顺-反异构化反应速率强烈的依赖于溶剂的极性。同时，光敏异构化还导致了该吡唑啉化合物荧光发射强度随光照时间而增大的有趣结果。     

菌紫质中视黄醛超快异构化反应的动态光谱分析

利用飞秒时间分辨吸收光谱方法研究了菌紫质(BR)光循环中视黄醛超快异构化反应过程. 发展了结合全局拟合的奇异值分解(SVD)分析方法, 建立了超快异构化反应动力学模型, 解析了几个重要的中间态I460, J625和K590的物种相关差异光谱(SADS)和布居动力学, 确定了光致异构化反应过程. 同时明确了700 nm附近存在的受激荧光来自于弗兰克-康登跃迁态(H中间态)的贡献, 其衰减寿命为0.04 ps. 这些结果对深入认识H态在超快异构化反应过程中的作用具有参考价值.     

The phase-dependent photochemical reaction dynamics of halooxides and nitrosyl halides

Recent progress in understanding the phase-dependent reactivity of halooxides and nitrosyl halides is outlined. Halooxide reactivity is represented by the photochemistry of chlorine dioxide (OClO) and dichlorine monoxide (ClOCl). The gas phase photochemical dynamics of OClO are contrasted with the dynamics in condensed environments. The role of excited-state symmetry in defining the reaction dynamics and the observation of photoisomerization resulting in the production of ClOO are discussed. The current understanding of the excited-state reaction dynamics of ClOCl and evidence for photoisomerization of this species resulting in the production of ClClO are outlined. Finally, the photochemical reaction dynamics of the nitrosyl halide ClNO are presented. The main difference between the gas and condensed phase reaction dynamics of this species is that whereas photodissociation to form Cl and NO dominates the gas phase reaction dynamics, photoisomerization resulting in ClON production occurs to an appreciable extent in condensed environments. The observation of photoisomerization for OClO, ClOCl and ClNO suggests that this process is a general feature of the condensed phase reaction dynamics for smaller halooxides and nitrosyl halides. Finally, future areas for study in both halooxide and nitrosyl halide photoreactivity are outlined.     

Ligand‐Tuning of the Excitation Wavelength of a Solid state E/Z Isomerization: [Zn(TA)2(2,2′‐Bipyridyl)] in a Supramolecular Framework

The single‐crystal‐to‐single‐crystal (SCSC) E?Z photoisomerization of TA in the supramolecular solid CECR‐[Zn(TA)₂(bpy)]·H₂O (CECR = C‐ethylcalixresorcinarene, HTA = tiglic acid, and bpy = 2,2′‐bipyridine, is induced by 458 nm light, indicating a red‐shift of the photo‐active wavelength on introduction of the aromatic bpy ligand compared with the previously studied reaction of CECR‐[Zn(TA)₂(H₂O)₂] 4H₂O. Theoretical calculations show that the initial excitation involves the bipyridyl ligand, which acts as an intramolecular photosensitizer for the isomerization process. The reaction is topotactic and illustrated by photodifference maps.     

Medium effects on the direct cis-trans photoisomerization of 1,4-diphenyl-1,3-butadiene in solution

Quantum yields for the photoisomerization of trans,trans-1,4-diphenyl-1,3-butadiene (tt-DPB), determined in benzene, cyclohexane, methylcyclohexane, hexane, and perfluorohexane, confirm the low values reported earlier for benzene and cyclohexane and reveal even lower values in the last two solvents. In contrast to trans-stilbene (t-St), fluorescence and torsional relaxation leading to photoisomerization do not account exclusively for S(1)tt-DPB decay. Competing radiationless singlet excited-state decay pathways exist in tt-DPB, which do not lead to photoisomerization and may not involve large-amplitude torsional motions. Our results invalidate analyses of tt-DPB fluorescence quantum yields and lifetimes that assign all radiationless decay to the isomerization channel. Gas-phase chromatography analysis of tt-DPB photoisomerization in hexane shows the reaction to be concentration-independent and reveals, for the first time, a significant, two-bond photoisomerization pathway, φ(tt→tc) = 0.092 and φ(tt→cc) = 0.020. The dominant one-bond-twist (OBT) process is accompanied by a bicycle pedal (BP) process that accounts for almost 20% of tt-DPB photoisomerization. The OBT tt-DPB photoisomerization quantum yield is largest in benzene (Bz) and smallest in perfluorohexane (PFH). Contrary to expectations, reduction in medium friction in PFH is accompanied by a decrease in φ(tt→tc). The 1(1)B(u)/2(1)A(g) order and energy gap appear to control the contribution of torsional relaxation to radiationless decay. Lowering the 1(1)B(u) energy as in Bz favors photoisomerization. Reversal of the 1(1)B(u)/2(1)A(g) order in PFH is accompanied by short τ(f) and small φ(f) and φ(tt→tc) values that suggest the presence of competing 2(1)A(g) → 1(1)Ag relaxation paths that are unproductive with respect to photoisomerization. We conclude that the Birks extension to diphenylpolyenes of the Orlandi-Siebrand cis-trans photoisomerization mechanism is not valid. Photoisomerization appears to occur in the 1(I)B(u) state, and we argue that this applies to t-St as well.     

双(苯并噁唑)芪的光物理行为及其异构化反应的研究

研究了双(苯并噁唑)芪的光物理行为和光顺反异构化反应,对这类化合物的发光光谱不依赖于溶剂极性的原因进行了初步讨论。异构化反应中,发现乙二醇引入时会加速该化合物反-顺异构化和抑制顺-反过程的回复,其原因可能是与生成了顺式异构体两个苯基苯并噁唑间的氢键有关。     

Cellular and antitumor activity of a new diethylene glycol benzoporphyrin derivative (lemuteporfin)

A newly synthesized diethylene glycol functionalized chlorin-type photosensitizer, lemuteporfin, was characterized for use in photodynamic therapy (PDT) in a panel of in vitro and in vivo test systems. The photosensitizer was highly potent, killing cells at low nanomolar concentrations upon exposure to activating light. The cellular uptake of lemuteporfin was rapid, with maximum levels reached within 20 min. Mitogen-activated lymphoid cells accumulated more of the lemuteporfin than their quiescent equivalents, supporting selectivity. Photosensitizer fluorescence in the skin increased rapidly within the first few minutes following intravenous administration to mice, then decreased over the next 24 h. Skin photosensitivity reactions indicated rapid clearance of the photosensitizer. Intravenous doses as low as 1.4 micromol/kg combined with exposure to 50 J/cm2 red light suppressed tumor growth in a mouse model. In conclusion, this new benzoporphyrin was found to be an effective photosensitizer, showing rapid uptake and clearance both in vitro and in vivo. This rapid photosensitization of tumors could be useful in therapies requiring a potent, rapidly accumulating photosensitizer, while minimizing the potential for skin photosensitivity reactions to sunlight following treatment.     

Photoisomerization of PtII Complexes Containing Two Different Photochromic Chromophores: Boron Chromophore versus Dithienylethene Chromophore

In order to examine competitive photoisomerization, a series of novel photochromic Pt^II molecules that contain both dithienylethene (DTE) and B(ppy)Mes₂ units (ppy=2-phenylpyridine, Mes=mesityl) were successfully synthesized and fully structurally characterized. Their photochromic properties were examined by UV/Vis, emission and NMR spectroscopy. It was found that the DTE unit in all three compounds is the preferred photoisomerization site, exhibiting reversible photochromism with irradiation. The B(ppy)Mes₂ unit does not undergo photoisomerization in these molecules, but likely enhances the photoisomerization quantum efficiency of the DTE moiety through the antenna effect. Extended irradiation with UV light leads to the rearrangement of the ring-closed isomers of DTE. TD-DFT computational studies indicate that the DTE photocyclization proceeds via a triplet pathway through an efficient energy transfer process.