八烷氧基萘酞菁锌的激发三重态性质及光动力抗癌活性

采用激光闪光光解技术测定了系列八烷氧基萘酞菁锌配合物ZnNc(OR)8(R=C4H9,C8H17,C12H25)激发三重态的寿命,研究了该系列化合物光敏化产生单重态氧的能力和对HL60癌细胞的光动力活性,并探讨了它们作为光敏剂在肿瘤光动力治疗中的光敏反应机制。     

八烷氧基萘酞菁锌的激发三重态性质及光动力抗癌活性

采用激光闪光光解技术测定了系列八烷氧基萘酞菁锌配合物ZnNc(OR)8(R=C4H9,C8H17,C12H25)激发三重态的寿命,研究了该系列化合物光敏化产生单重态氧的能力和对HL60癌细胞的光动力活性,并探讨了它们作为光敏剂在肿瘤光动力治疗中的光敏反应机制。     

几种光敏剂光敏氧化效率的比较

<正> 光敏氧化效率是由敏化剂分子吸收光量子数及其产生单重态氧的量子产率决定的,这要求敏化剂的吸收光谱同光源的发射光谱很好地匹配。本文报道竹红菌甲素匹配高压钠灯有效地产生单重态氧,高效光敏氧化一系列具有不同反应活性的底物,成为单重态氧化学中一个新的光敏氧化体系。     

极性敏感的BDP分子溶剂化效应的光谱性质

合成了具有分子内电荷转移(ICT)性质的三重态光敏剂分子BDP, 研究了其稳态吸收光谱、 荧光光谱、 荧光寿命、 飞秒/纳秒瞬态吸收光谱及诱导产生单线态氧的能力等性质, 发现强极性溶剂对BDP分子的溶剂化效应降低了其ICT态和第一激发三重态(T₁态)的能量, 从而降低了BDP分子单线态氧的产量.     

几种萘酞菁硅配合物的光动力效应的研究

研究了7种轴向配位的萘酞菁硅配合物的激发态性质、产生单重态氧的能力及对几种氨基酸的光敏氧化能力.研究表明,对于相同浓度的不同配合物来说,随着轴向配位基团推电子能力的逐渐增强,激发三重态寿命降低,产生单重态氧的能力逐渐下降,而产生单重态氧的能力是光敏氧化氨基酸反应速率的决定因素,因此,其光敏氧化氨基酸的一级反应速率常数逐渐减小.     

新型绿色农药——光活化农药

光活化农药包括光活化杀虫剂和光活化除草剂, 与传统农药相比具有廉价、高效、无污染等优越性。光活化农药的关键是光敏剂, 在有光和氧存在条件下光敏剂催化产生单重态氧, 杀灭害虫。光敏剂效果取决于其单重态氧的量子产率, 其分子本身只起催化作用并不介入毒性反应, 并且易被降解, 因此对环境无污染。由于单重态氧在细胞上的生物化学作用点多, 使害虫不易对其产生抗药性。这类绿色农药正在逐步走向实用化, 它的发展将会大大改善因长期使用传统农药而造成的危害, 对农业发展将会产生巨大的促进作用。     

激子的分裂与高效太阳能电池

能将单重态激子分裂为两个三重态激子的化合物,可作为一种新型的敏化剂,较大程度地提高太阳能电池的光-电转换能力.本文扼要地介绍了激子分裂的基本要点和发展状况,并对研究这一现象的实验方法和分裂机制等进行了讨论.在实验方法部分,叙述了通过稳态与瞬态延迟光谱的测定,可对体系中单重态的分裂和三重态重合,进而对激子的分裂进行研究,此外,还对激子的偶合、能级间的能量关系,以及环境效应等作了介绍.文章还对激子分裂过程的可能机制和如何选择这类敏化剂分子的一些基本准则,给予了讨论和说明.     

高分子三重态敏化剂的研究III: 高分子苯乙酮敏化过程中能量迁移的研究

本工作合成了一组不同组成的聚(苯乙烯-乙烯基苯乙酮)高分子敏化剂, 对分子中两组分的含量进行了标定. 通过荧光和磷光光谱的研究表明: 高分子敏化剂分子中存在着单重态和三重态的能量迁移和T-T湮灭作用.从降冰片二烯光敏异构化为四环烷的反应中发现, 苯乙酮摩尔含量为38%的高分子苯乙酮敏化剂具有最大的敏化能力, 并对上述诸现象产生的原因进行了分析和讨论.     

硅甲基氮烯异构化反应的理论研究

应用量子化学从头算方法研究了硅甲基氮烯单重态和三重态的异构化反应,优化了单重态异构化反应的过渡态。提出三重态先通过系间交叉(intersystem crossing)转变为单重态,再发生异构化的反应机理。计算了单重态和三重态的分裂能以及反应的活化势垒和反应能量,给出了反应物、过渡态和产生的有关结构数据。     

β-二酮类化合物的光互变异构化反应

对三种β-二酮类化合物的光异构化反应进行了研究,并对它们在光照后产生单重态氧的能力进行了测定。该类化合物产生单重态氧的能力与其光异构化为酮式结构的能力成正比,因此凡易于进行光酮化反应的体系,可作为光敏化剂,而不易于进行该反应者,可作为光稳定剂。     

新型三重态光敏剂——3-芳甲酰基香豆素光物理和光化学性质的研究

本工作合成了一系列新型的三重态光敏剂——3-芳甲酰基香豆素。测定了它们的吸收光谱和磷光光谱,研究了它们的光物理和光化学行为,包括如磷光量子产率的测定以及比较了它们对反式茋敏化异构化的能力。结果表明,这是一类很有效的三重态光敏剂。     

Organic triplet sensitizer library derived from a single chromophore (BODIPY) with long-lived triplet excited state for triplet-triplet annihilation based upconversion

Triplet-triplet annihilation (TTA) based upconversions are attractive as a result of their readily tunable excitation/emission wavelength, low excitation power density, and high upconversion quantum yield. For TTA upconversion, triplet sensitizers and acceptors are combined to harvest the irradiation energy and to acquire emission at higher energy through triplet-triplet energy transfer (TTET) and TTA processes. Currently the triplet sensitizers are limited to the phosphorescent transition metal complexes, for which the tuning of UV-vis absorption and T(1) excited state energy level is difficult. Herein for the first time we proposed a library of organic triplet sensitizers based on a single chromophore of boron-dipyrromethene (BODIPY). The organic sensitizers show intense UV-vis absorptions at 510-629 nm (ε up to 180,000 M(-1) cm(-1)). Long-lived triplet excited state (τ(T) up to 66.3 μs) is populated upon excitation of the sensitizers, proved by nanosecond time-resolved transient difference absorption spectra and DFT calculations. With perylene or 1-chloro-9,10-bis(phenylethynyl)anthracene (1CBPEA) as the triplet acceptors, significant upconversion (Φ(UC) up to 6.1%) was observed for solution samples and polymer films, and the anti-Stokes shift was up to 0.56 eV. Our results pave the way for the design of organic triplet sensitizers and their applications in photovoltaics and upconversions, etc.     

A MODEL FOR BIOLOGICAL QUANTUM CONVERSION INVOLVING THE PHOTOOXIDATIVE DEPHOSPHORYLATION OF MENADIOL DIPHOSPHATE

Abstract— The mechanism of the photooxidative dephosphorylation of menadiol diphosphate appears to be invariant with respect to three sensitizers used; namely, riboflavin, biacetyl, and menadiol diphosphate itself. The mechanism involves triplet energy transfer from the sensitizers to oxygen to yield singlet oxygen which oxidizes menadiol diphosphate. The photolysis of menadiol diphosphate in acetic acid has resulted in formation of acetyl phosphate, as determined by paper chromatography. Therefore, we have demonstrated the feasibility of our model for converting light energy into chemical potential ('high-energy' phosphate bond energy or group transfer potential) in the form of acetyl phosphate.     

XANTHENE DYES AS SENSITIZERS FOR THE PHOTOREDUCTION OF WATER

Abstract— Some photochemical and photophysical properties of a group of xanthene dyes have been studied in relation to their roles as sensitizers for the photoreduction of water. New spectroscopic and kinetic measurements have been carried out with these dyes. The triplet states of the dyes undergo energy-transfer and electron-transfer, but with rate constants differing by two orders of magnitude in favour of the former pathway. The very efficient transfer of triplet energy from a group of dyes to an acceptor molecule led to the design of a greatly improved system for the photochemical production of hydrogen.     

Effects of conjugation length and resonance enhancement on two-photon absorption in phenylene-vinylene oligomers

Two-photon excitation spectra have been recorded over the large spectral range of 540-1000 nm for five phenylene-vinylene oligomers that differ in the length of the conjugated pi system. The significant changes observed in the two-photon excitation spectra and absorption cross sections as a function of this systematic change in the chromophore are discussed in light of (1) the corresponding one-photon absorption spectra and (2) high-level density functional response theory calculations performed on analogues of these systems. The results obtained illustrate one way to exploit parameters that influence nonlinear optical properties in large organic molecules. Specifically, data are provided to indicate that when the frequency of the laser used in the two-photon experiment is nearly-resonant with an allowed one-photon transition, significant increases in the two-photon absorption cross section can be realized. This phenomenon of the so-called resonance enhancement allows for greater control in obtaining an optimal response when using existing two-photon chromophores, and provides a much-needed guide for the systematic development and efficient use of two-photon singlet oxygen sensitizers.     

3D Stereolithography by Using Two-Photon Photopolymerization

Summary: This article describes the development and evolution of two-photon lithography of 3-dimensional (3D) polymeric structures through two-photon photopolymerization (TPP) and the materials used to facilitate the same. The first part elaborates on the advantages of TPP over conventional lithographic techniques used in the fabrication of 3D microelectromechanical systems (MEMS). The second part introduces the preparation of highly efficient organic two-photon absorbing materials based on the centro-symmetric π-conjugated system and their performance as sensitizers in two-photon polymerization.     

Two-photon photosensitized production of singlet oxygen: sensitizers with phenylene-ethynylene-based chromophores

[reaction: see text] Singlet molecular oxygen (a(1)Delta(g)) has been produced and optically monitored in time-resolved experiments upon nonlinear two-photon excitation of photosensitizers that contain triple bonds as an integral part of the chromophore. Both experiments and ab initio computations indicate that the photophysical properties of alkyne-containing sensitizers are similar to those in the alkene-containing analogues. Most importantly, however, in comparison to the analogue that contains double bonds, the sensitizer containing alkyne moieties is more stable against singlet-oxygen-mediated photooxygenation reactions. This increased stability can be advantageous, particularly with respect to two-photon singlet oxygen imaging experiments in which data are collected over comparatively long time periods.     

Studies on the radiolytically produced transients of neutral red: triplet and reduced radicals

The spectral and kinetic properties of reduced radicals and the triplet state of neutral red (NR), a phenazine-based dye, have been investigated using pulse radiolysis technique. A mixed water-isopropanol-acetone solvent has been used to study the reduced radicals of NR for a wide pH range of about 1-13, due to limitation of solubility of the dye in aqueous solutions particularly above pH 8. From pH-dependent absorption studies it has been established that the reduced radicals of NR can exist in four different prototropic forms in solution. Three pKa values for the corresponding prototropic equilibria have been estimated. The formation and decay rate constants of reduced radicals have also been measured. The triplet state characteristics of the dye have been investigated in neat benzene solutions, both in the presence and in the absence of triplet sensitizers. The T1-->Tn absorption spectrum and decay kinetics of the triplet state have been measured. The triplet state energy (ET) of NR in benzene have been estimated to be within 36-42 kcal mol-1, using an energy transfer method.     

A PULSED LASER AND PULSE RADIOLYSIS STUDY OF AMPHIPHILIC CHLOROPHYLL DERIVATIVES WITH PDT ACTIVITY TOWARD MALIGNANT MELANOMA

Two amphiphilic derivatives of chlorophyll, which have high potential as photodynamic therapy sensitizers for malignant melanoma have been investigated by a combination of laser flash photolysis and pulse radiolysis. It is shown that direct excitation of monomeric forms of these molecules in both hydrophilic and hydrophobic environments produces significant yields of the corresponding triplet states, which have been characterized in terms of spectral and kinetic parameters. In both environments, scavenging of the triplets by oxygen produces singlet oxygen, O₂(^lΔ₈), with essentially unit efficiency as evidenced by time-resolved IR luminescence measurements.     

Synthesis,Characterization, Photophysics and Photochemistry of Pyrylogen Electron Transfer Sensitizers

A series of new dicationic sensitizers that are hybrids of pyrylium salts and viologens has been synthesized. The electrochemical and photophysical properties of these “pyrylogen” sensitizers are reported in sufficient detail to allow rationale design of new photoinduced electron transfer reactions. The range of their reduction potentials (+0.37–+0.05 V vs SCE) coupled with their range of singlet (48–63 kcal mol^?1) and triplet (48–57 kcal mol^?1) energies demonstrate that they are potent oxidizing agents in both their singlet and triplet excited states, thermodynamically capable of oxidizing substrates with oxidation potentials as high as 3.1 eV. The pyrylogens are synthesized in three steps from readily available starting materials in modest overall 11.4–22.3% yields. These sensitizers have the added advantages that: (1) their radical cations do not react on the CV timescale with oxygen bypassing the need to run reactions under nitrogen or argon and (2) have long wavelength absorptions between 413 and 523 nm well out of the range where competitive absorbance by most substrates would cause a problem. These new sensitizers do react with water requiring special precautions to operate in a dry reaction environment.