卟啉类试剂合成的进展

综述了近十几年来卟啉试剂合成的进展,收集的卟啉试剂共１５２种,分成４类,即对称、非对称型、双卟啉型和高分子型卟啉等。     

Self-assembly of novel tris(p-carboxyphenyl) porphyrin monomer and its copolymers with acrylamide in aqueous media

The novel porphyrin monomer 5-(4-acryloyloxylphenyl)-10,15,20-tris(4-carboxyphenyl)porphyrinate zinc(II) (ZnAOTCPP) and its corresponding sodium salt (ZnAOTCPP-Na) were synthesized. The latter compound exhibited a new band in excitation spectra due to formation of porphyrin aggregates in water, which were derived from its surface-activity when the concentration was higher than its critical association concentration (CAC). The porphyrins were copolymerized with acrylamide (AM) to prepare water-soluble copolymers with random and micro-blocky structures, which all displayed very new absorption and fluorescence emission bands in the long wavelength region compared with the porphyrin monomer. Furthermore, the micro-blocky copolymer exhibited an additional new absorption band at even longer wavelength region compared with the random copolymer. The experimental results and analysis showed that the porphyrin units in the random copolymer chains self-assembled to form porphyrin association complexes by hydrophobic association and π-π stacking interactions, and covalent restrictions of polymer chains in the micro-blocky copolymer.     

Meso位直结型稳定双卟啉的合成及性质

利用氧化法成功地合成了同核ｍｅｓｏ位直结型稳定卟啉二聚体锌络合物，收率接近理论值；无论是碱式还是金属络合物都显示出卟啉环间成平面正交的电子吸收光谱；在循环伏安图谱中都显示出卟啉环间再氧化还原过程中较强烈的库仑作用；每个卟啉环的一电子氧化或还原均可逆过程。     

Towards Copper(I) Clusters for Photo-Induced Oxidation of Biological Thiols in Living Cells**

The cell redox balance can be disrupted by the oxidation of biological peptides, eventually leading to cell death, which provides opportunities to develop cytotoxic drugs. With the aim of developing compounds capable of specifically inducing fatal redox reactions upon light irradiation, we have developed a library of copper compounds. This metal is abundant and considered essential for human health, making it particularly attractive for the development of new anticancer drugs. Copper(I) clusters with thiol ligands (including 5 novel ones) have been synthesized and characterized. Structures were elucidated by X-ray diffraction and showed that the compounds are oligomeric clusters. The clusters display high photooxidation capacity towards cysteine – an essential amino acid – upon light irradiation in the visible range (450 nm), while remaining completely inactive in the dark. This photoredox activity against a biological thiol is very encouraging for the development of anticancer photoredox drugs.The in vitro assay on murine colorectal cancer cells (CT26) did not show any toxicity – whether in the dark or when exposed to 450 nm light, likely because of the poor solubility of the complexes in biological medium.     

Photochemistry and Cytotoxicity Evaluation of Heptamethinecyanine Near Infrared (NIR) Dyes

The present study investigates the photochemical properties of potential photosensitizers for photodynamic therapy, namely four commercial heptamethinecyanine dyes (IR125, IR780, IR813, IR820). Spectroscopic studies were made by means of laser induced fluorescence and laser flash photolysis in order to obtain fluorescence quantum yields and transient absorption spectra. Fluorescence lifetimes were also determined. The differences encountered were essentially related with the interaction of the sulfonate groups with the solvent, and also regarding the rigidification of the central bridge connecting the two nitrogen-containing heterocyclic groups. Transient absorption studies were performed both in aerated and oxygen free samples, to conclude about the formation of photoisomers and triplet state. For the four dyes under study, a cytotoxic evaluation in the dark and after irradiation was performed using HeLa cells as the model cell line, which revealed significant changes after irradiation mainly in IR125 and IR813 dyes. Confocal microscopy analysis showed that these dyes tend to enter to the intracellular space.     

Towards Understanding Excited-State Properties of Organic Molecules Using Time-Resolved Soft X-ray Absorption Spectroscopy

The extension of the pump-probe approach known from UV/VIS spectroscopy to very short wavelengths together with advanced simulation techniques allows a detailed analysis of excited-state dynamics in organic molecules or biomolecular structures on a nanosecond to femtosecond time level. Optical pump soft X-ray probe spectroscopy is a relatively new approach to detect and characterize optically dark states in organic molecules, exciton dynamics or transient ligand-to-metal charge transfer states. In this paper, we describe two experimental setups for transient soft X-ray absorption spectroscopy based on an LPP emitting picosecond and sub-nanosecond soft X-ray pulses in the photon energy range between 50 and 1500 eV. We apply these setups for near-edge X-ray absorption fine structure (NEXAFS) investigations of thin films of a metal-free porphyrin, an aggregate forming carbocyanine and a nickel oxide molecule. NEXAFS investigations have been carried out at the carbon, nitrogen and oxygen K-edge as well as on the Ni L-edge. From time-resolved NEXAFS carbon, K-edge measurements of the metal-free porphyrin first insights into a long-lived trap state are gained. Our findings are discussed and compared with density functional theory calculations.     

Studies on the photo-oxidation mechanism of polymers. VI. The role of commercial thermostabilizers in the photostability of poly(vinyl chloride)

This paper presents a study on the photolysis of PVC in the presence of different types of tin stabilizers. Using physicochemical methods such as ESR spectroscopy, conductivity titration, gel permeation chromatography, and absorption spectroscopy, the mechanism of PVC photolysis has been investigated. ESR spectroscopy shows that during UV irradiation of tin stabilizers, different types of free radicals depending on the chemical structure of the examined compounds are formed. It has been found that the presence of tin stabilizers does not significantly influence the photo-oxidation and degradation of PVC but influences the crosslinking processes. The authors propose an interpretation of the free-radical formation during UV photolysis of tin stabilizers and of the crosslinking acceleration mechanism.     

A comparison of diamonds irradiated by high fluence neutrons or electrons, before and after annealing

Neutron- and electron-irradiated type Ia “black” diamonds were analyzed: three near colorless type Ia diamonds were treated in a nuclear reactor with a dose of 1.8 × 10¹⁷ neutrons/cm² and three equivalent samples were irradiated in an electron accelerator with a dose of approximately 0.5 GGy 10 MeV electrons. The diamonds were then annealed and analyzed after the different steps of the treatment. The samples turned from near colorless to very dark green to opaque black upon irradiation and deep greenish yellow to deep orangy brown upon annealing (Fig. 1). The amount of brown color developed during the treatment was found to relate to the type of irradiation used and likely to the total dose of irradiation. The absorption and photoluminescence features as well as the color changes that were observed were found to be unusual and characteristic for diamonds treated with such high irradiation doses. Certain spectral features such as the 644/649 nm, the 724/734/738 nm, the 920 nm and the 967 nm absorptions were only detected in the neutron-irradiated diamonds while others such as the 6165 cm^− 1 and the 805 nm absorptions were only found in the spectra of the electron-irradiated stones.In addition to these treatment experiments some neutron-irradiated very dark green (appearing black) diamonds were heated from 300 to 1100 °C in increments of 50 °C to get a precise idea of the temperature at which color changes occur and the various absorption peaks form. All diamonds turned yellowish to orangy brown after annealing above 700 °C and most of them exhibited unusually strong H1b and/or H1c absorptions after annealing at > 900 °C.     

Light-stimulated oxidation reactions of tris(1,10-phenanthroline), tris (2,2′-dipyridine) and bis(2,2′,2″-tripyridine)iron(II) complexes

The oxidation reactions of Fe(phen)²⁺₃, Fe(dipy)²⁺₂ were investigated electrochemically under the irradiation of visible light and in the dark. Two arrests in current were observed at 0.5 and 0.9 V (vs sce) in the anodic polarization curves of these complexes. The initial and the second arrests were ascribed to the oxidations of the aquo-ferrous ion and FeL²⁺_n, respectively. The oxidation of these complexes was stimulated by irradiation with light. It was concluded that d electrons were excited to antibonding ligand orbitals, on absorbing visible light and then the electrochemical oxidation of these complexes proceeded more favourably under the irradiation of light than in the dark.     

Substituent effects of iron porphyrins: Structural, kinetic, and theoretical studies

Substituent effects of iron porphyrin complexes on the structures and kinetic processes have been examined for the first time. Basing on the premise that iron porphyrin is functional analogous to heme, a series of iron porphyrin derivatives bearing different substituents at the meso positions of the corrole ring are investigated as to their electrochemistry, the relationships among the electron transfer (ET) processes, their structures, and orbital energies. The good coherence between the experiment and theory indicates that the ET rate can be accelerated when electron-donating substituents are introduced to the iron porphyrin ring. Finally, the implications of the results are discussed in the influence of stability of iron porphyrin complexes on the ability to carry molecular oxygen, which may suggest it possible to dominate the biological activity of heme by selecting the appropriate substituents to iron porphyrin ring.     

Reversible discoloration effects in the photoaging of poly(vinyl chloride)

It is often observed that the photochemical degradation of titanium dioxide pigmented PVC leads to a latent discoloration that is revealed only during a further period of storage of the aged material in the dark. This effect is reversible, and photobleaching can be provoked by a new irradiation of the polymer. This behavior can be attributed to the formation of polyenic sequences with a short conjugation length, which present an absorption below 400 nm. The screen effect of the pigment protects these polyenes against photooxidation, which permits these polyenes to accumulate in the degraded polymer. In the absence of light, these polyenes can be thermally isomerized, so leading to isomer forms absorbing at longer wavelength above 400 nm. This absorption is responsible for a yellowing of the polymer. The isomerization is perfectly reversible and a further irradiation provokes the conversion to the isomer form absorbing below 400 nm, leading then to a photobleaching of the sample. These experiments can be repeated many times before any distortion occurs.     

1,3-二乙酸咪唑磷钨酸盐的制备及其对甲基红的光催化降解性能

采用元素分析和红外光谱对所制磷钨酸1,3-二乙酸咪唑盐催化剂进行表征,考察了光照时间、催化剂用量对光催化降解有机染料甲基红效率的影响. 结果表明,无光催化剂时甲基红可直接光解,完全光解所需时间为220 min;催化剂用量为0.02?0.10 g时,对甲基红光降解效率随催化剂用量增加显著提高;加入0.08 g催化剂后,紫外光照射60 min可使甲基红溶液降解完全,降解效率为未加入催化剂时的3倍.     

四对硝基苯基卟啉和四对氨基苯基卟啉的合成

分别采用苯基卟啉硝化法(两步法)和对硝基苯甲醛直接合成法合成了四对硝基苯基卟啉(TNPP)。苯基卟啉硝化法首先采用Alder方法合成四苯基卟啉,然后以发烟硝酸为硝化试剂,将苯环对位硝化,反应产物是一硝化、二硝化、三硝化和四硝化产物的混合物,难分离,而且此路线腐蚀性强,操作困难,不宜大规模制备。对硝基苯甲醛直接合成法,以丙酸做反应溶剂,使反应活性降低,从而避免了更多的副反应,反应结束后,直接过滤即可得到四对硝基苯基卟啉,收率为22%。再将TNPP用二水合氯化亚锡在盐酸中还原得到四对氨基苯基卟啉(TAPP),还原收率为60%。IR、1H NMR、元素分析等证实产物结构。紫外可见吸收光谱和荧光光谱显示相对于四苯基卟啉,吸电子的硝基和给电子的氨基均使其Q带和B带的吸收位置红移,并使其发光位置也明显红移。     

金属卟啉配合物在催化空气氧化环己烷反应中的应用

以四苯基卟啉和乙酸盐为原料,合成了4种简单过渡金属配合物,并应用紫外-可见光谱仪（UV-vis）和傅里叶变换红外光谱仪（FTIR）对所得产物进行表征,获得了同周期过渡金属卟啉配合物吸收光谱的重要信息。研究表明,通过紫外-可见及红外光谱对过渡金属卟啉配合物中心离子的价态及其在周期表中的位置进行初步判断是可行的。以空气氧化环己烷制备环己醇和环己酮为探针反应,在不加入任何溶剂或助催化剂的条件下考察了金属卟啉用量、反应温度、压力、时间等对其催化活性的影响。结果发现,锰卟啉催化活性最好,在最佳反应条件下,环己烷转化率最高可达15.37%,环己醇和环己酮的总选择性约为93.94%。     

Effect of Fenton and photo-Fenton reactions on the degradation and biodegradability of 2 and 4-nitrophenols in water treatment

Photo-Fenton, Fenton and biodegradation reactions have been investigated in detail during the degradation of 2 and 4-nitrophenols. Fenton-type reactions accelerated nitrophenols degradation in comparison with direct photolysis using pyrex flasks (λ > 290 nm). The influence of Fe³⁺, H₂O₂, light, temperature, reactant concentration and gas atmosphere was systematically studied. Experimental techniques used involved total organic carbon determination (TOC), high pressure liquid chromatography (HPLC), nuclear magnetic resonance (NMR) and spectroscopy (OD). A solution containing 3.6·10⁻¹ M of 2-nitrophenol was degraded in ca. 3 h (30°C) in the dark and in ca. 1 h (30°C) under light where continuous photoproduction of the Fenton reagent is achieved. This study shows that the hydrolxylation of the phenol ring is fast as compared to the slower concomitant decrease in DOC in dark or light processes. Using NMR an explanation is proposed in terms of pathways involving direct oxidation of the nitrophenols under study by hydroxy type radicals. Chemical insight is provided why the photo-Fenton degradation observed for 2-nitrophenol proceeds at about half the rate than his homologue 4-nitrophenol. Biodegradability of 2-nitrophenol was monitored before and after photo-Fenton treatment by biochemical oxygen demand (BOD) and dissolved organic carbon (DOC) and indicated the formation of substances which are non-biodegradable during photo-Fenton pretreatment.     

Synthesis and spectral evaluation of some unsymmetrical mesoporphyrinic complexes

Synthesis and spectral evaluation of new zinc and copper unsymmetrical mesoporphyrinic complexes are reported. Zn(II)-5-(4-acetoxy-3-methoxyphenyl)-10,15,20- tris-(4-carboxymethylphenyl)porphyrin, Zn(II)-5-[(3,4-methylenedioxy)phenyl]-10,15,20- tris-(4-carboxymethylphenyl)porphyrin, Cu(II)-5-(4-acetoxy-3-methoxyphenyl)-10,15,20- tris-(4-carboxymethylphenyl)porphyrin and Cu(II)-5-[(3,4-methylenedioxy)phenyl]-10,15,20- tris-(4-carboxymethylphenyl)porphyrin were synthesized using microwave-assisted synthesis. The complexes were characterized by elemental analysis, FT-IR, UV-Vis, EPR and NMR spectroscopy, which fully confirmed their structure. The spectral absorption properties of the porphyrinic complexes were studied in solvents with different polarities. Fluorescence emission and singlet oxygen formation quantum yields were evaluated for the compounds under study, revealing high yields for the zinc derivatives. The copper complexes are not emissive and only display residual capacity for singlet oxygen formation.     

The kinetics of phenol decomposition under UV irradiation with and without H2O2 on TiO2, Fe–TiO2 and Fe–C–TiO2 photocatalysts

H₂O₂ used in the photo-Fenton reaction with iron catalyst can accelerate the oxidation of Fe²⁺ to Fe³⁺ under UV irradiation and in the dark (in the so called dark Fenton process). It was proved that conversion of phenol under UV irradiation in the presence of H₂O₂ predominantly produces highly hydrophilic products and catechol, which can accelerate the rate of phenol decomposition. However, while H₂O₂ under UV irradiation could decompose phenol to highly hydrophilic products and dihydroxybenzenes in a very short time, complete mineralization proceeded rather slowly. When H₂O₂ is used for phenol decomposition in the presence of TiO₂ and Fe–TiO₂, decrease of OH radicals formed on the surface of TiO₂ and Fe–TiO₂ has been observed and photodecomposition of phenol is slowed down. In case of phenol decomposition under UV irradiation on Fe–C–TiO₂ photocatalyst in the presence of H₂O₂, marked acceleration of the decomposition rate is observed due to the photo-Fenton reactions: Fe²⁺ is likely oxidized to Fe³⁺, which is then efficiently recycled to Fe²⁺ by the intermediate products formed during phenol decomposition, such as hydroquinone (HQ) and catechol.     

Ab initio determination of dark structures in radiationless transitions for aromatic carbonyl compounds

Mechanistic photodissociation of a polyatomic molecule has long been regarded as an intellectually challenging area of chemical physics, the results of which are relevant to atmospheric chemistry, biological systems, and many application fields. Carbonyl compounds play a unique role in the development of our understanding of the spectroscopy, photochemistry, and photophysics of polyatomic molecules and their photodissociation has been the subject of numerous studies over many decades. Upon irradiation, a molecule can undergo internal conversion (IC) and intersystem crossing (ISC) processes, besides photochemical and other photophysical processes. Transient intermediates formed in the IC and ISC radiationless processes, which are termed "dark", are not amenable to detection by conventional light absorption or emission. However, these dark intermediates play critical roles in IC and ISC processes and thus are essential to understanding mechanistic photochemistry of a polyatomic molecule. We have applied the multiconfiguration complete active space self-consistent field (CASSCF) method to determine the dark transient structures involved in radiationless processes for acetophenone and the related aromatic carbonyl compounds. The electronic and geometric structures predicted for the dark states are in a good agreement with those determined by ultrafast electron diffraction experiments. Intersection structure of different electronic states provides a very efficient "funnel" for the IC or ISC process. However, experimental determination of the intersection structure involved in radiationless transitions of a polyatomic molecule is impossible at present. We have discovered a minimum energy crossing point among the three potential energy surfaces (S1, T1, and T2) that appears to be common to a wide variety of aromatic carbonyl compounds with a constant structure. This new type of crossing point holds the key to understanding much about radiationless processes after photoexcitation of aromatic carbonyl compounds. The importance of ab initio determination of transient structures in the photodissociation dynamics has been demonstrated for the case of the aromatic carbonyl compounds. In addition, the detailed knowledge of mechanistic photochemistry for aromatic carbonyl compounds forms the basis for further investigating photodissociation dynamics of a polyatomic molecule.     

金属卟啉配合物的性能及应用研究进展

金属卟啉配合物是卟啉衍生物中的主体化合物,因其具有优异性能而被广泛地研究与应用.分别从仿生体系、分子识别、催化、材料、有机合成和医疗等方面简要介绍了金属卟啉配合物的优异性能及其应用,旨在让人们了解并熟悉金属卟啉配合物的性能及用途.     

二烷基(4-羟基苯基)硫鎓盐的电荷转移络合物及其敏化光降解

二烷基(4-羟基苯基)硫鎓盐作为一类新型的光引发剂由于其合成方法简便以及具较宽的光谱范围(可延伸至300nm)。因而近年来颇受重视。由于该引发剂在光照激发后生成了共振一稳定的内鎓盐(Ylide)结构和质子酸。如下式: