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Photochemical Properties (photochemical + property)
Selected AbstractsPhotophysical and Photochemical Properties of Fluorinated and Nonfluorinated n -Propanol-Substituted Zinc PhthalocyaninesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 8 2010lke Gürol Abstract The synthesis of symmetrical fluorinated and nonfluorinated zinc(II) phthalocyanine derivatives obtained from 4,5-dichlorophthalonitrile, 4-nitrophthalonitrile and 3-nitrophthalonitrile substituted with 2,2,3,3-tetrafluoro-1-propanol and n -propanol are described. The comparison of the photophysicochemical properties of fluorinated and nonfluorinated substituted zinc(II) phthalocyanines is reported for the first time. The new compounds have been characterized by elemental analysis, IR, 1H NMR and 19F NMR spectroscopy, electronic spectroscopy and mass spectra. The photophysical and photochemical properties of the compounds were studied in dimethyl sulfoxide (DMSO). The complexes were quenched with benzoquinone (BQ), and their fluorescence-quenching properties were investigated in the same solvent. The effects of the number of the substitution and the position on the photophysical and photochemical parameters of the zinc(II) phthalocyanines 1a,7a are also reported. Photophysical and photochemical properties of phthalocyanine complexes are very useful for photodynamic therapy (PDT) of cancer applications. In particular, high singlet-oxygen quantum yields are very important for Type II mechanisms. These complexes have good singlet-oxygen quantum yields and show potential as Type-II photosensitizers. [source] ChemInform Abstract: Design, Synthesis, Photochemical Properties and Cytotoxic Activities of Water-Soluble Caged L-Leucyl-L-leucine Methyl Esters that Control Apoptosis of Immune Cells.CHEMINFORM, Issue 20 2002Hironori Mizuta Abstract ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a "Full Text" option. The original article is trackable via the "References" option. [source] Photophysical and Photochemical Properties of Fluorinated and Nonfluorinated n -Propanol-Substituted Zinc PhthalocyaninesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 8 2010lke Gürol Abstract The synthesis of symmetrical fluorinated and nonfluorinated zinc(II) phthalocyanine derivatives obtained from 4,5-dichlorophthalonitrile, 4-nitrophthalonitrile and 3-nitrophthalonitrile substituted with 2,2,3,3-tetrafluoro-1-propanol and n -propanol are described. The comparison of the photophysicochemical properties of fluorinated and nonfluorinated substituted zinc(II) phthalocyanines is reported for the first time. The new compounds have been characterized by elemental analysis, IR, 1H NMR and 19F NMR spectroscopy, electronic spectroscopy and mass spectra. The photophysical and photochemical properties of the compounds were studied in dimethyl sulfoxide (DMSO). The complexes were quenched with benzoquinone (BQ), and their fluorescence-quenching properties were investigated in the same solvent. The effects of the number of the substitution and the position on the photophysical and photochemical parameters of the zinc(II) phthalocyanines 1a,7a are also reported. Photophysical and photochemical properties of phthalocyanine complexes are very useful for photodynamic therapy (PDT) of cancer applications. In particular, high singlet-oxygen quantum yields are very important for Type II mechanisms. These complexes have good singlet-oxygen quantum yields and show potential as Type-II photosensitizers. [source] On the Photochemical Stability of the 9-Mesityl-10-methylacridinium CationEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 2 2009Andrew C. Benniston Abstract The 9-mesityl-10-methylacridinium cation in aerated deuterated/normal acetonitrile decomposes to give several side products when continuously exposed to white light. The main breakdown product isolated by column chromatography is identified as 3,5-dimethyl-4-(10-methylacridinium)benzaldehyde. This assignment was confirmed by single-crystal X-ray crystallography. In light of these findings it appears that decomposition pathways also need to be considered when discussing the photochemical properties of the 9-mesityl-10-methylacridinium cation, especially in the presence of dioxygen.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Noble Metal Nanocrystal-Incorporated Fullerene-Like Polyoxometalate Based MicrospheresADVANCED FUNCTIONAL MATERIALS, Issue 6 2009Amjad Nisar Abstract Monodisperse fullerene-like polyoxometalate-based microspheres are synthesized using a single-phase approach which is quick, easier to control surfactant to polyoxometalate (POM) molar ratios and result in better control over the size-distribution range. Noble-metal nanocrystals are successfully incorporated in the surfactant encapsulated complex multilayered spherical assemblies without any change in their layered morphology. Combining the merits of fullerene-like POMs and monodisperse noble metal nanocrystals, these monodisperse hybrid spheres show interesting composition- and size-dependent photochemical properties. [source] Synthesis of new photoresponsive polyesters containing norbornadiene residues by the polyaddition of donor,acceptor norbornadiene dicarboxylic acid diglycidyl ester with dicarboxylic acids and their photochemical propertiesJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 16 2001Yousuke Konno Abstract A donor,acceptor norbornadiene derivative, 5-(4-methoxyphenyl)-1,4,6,7,7-pentamethyl-2,5-norbornadiene-2,3-dicarboxylic acid diglycidyl ester (D,A NDGE), was synthesized by the reaction of the cesium salt of 5-(4-methoxyphenyl)-1,4,6,7,7-pentamethyl-2,5-norbornadiene-2,3-dicarboxylic acid with epibromohydrin in N -methyl- pyrrolidone (NMP). The polyaddition reactions of D,A NDGE with certain dicarboxylic acids were carried out with tetrabutylammonium bromide as a catalyst in NMP, producing corresponding polyesters containing D,A norbornadiene (NBD) residues in the main chain in fair to good yields. The photoisomerization of the D,A NBD residues in the polyesters proceeded very smoothly, forming the corresponding quadricyclane groups. The photoreactivities of the D,A NBD residues in the polymer were 50 times higher than those of the NBD residues in the film state and 60 times higher than those in a tetrahydrofuran solution. The stored energy in the quadricyclane groups of the polymers was about 45,55 kJ/mol according to differential scanning calorimetry analysis of the irradiated polymer films. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2683,2690, 2001 [source] Surface Elastic Properties of Human Retinal Pigment Epithelium Melanosomes,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 3 2008Senli Guo Atomic force microscope (AFM) imaging and nanoindentation measurements in water were used to probe the mechanical properties of retinal pigment epithelium melanosomes isolated from 14-year-old and 76-year-old donors. Topographic imaging reveals surface roughness similar to previous measurements on dry melanosomes. Force-indentation measurements show different types of responses that were catalogued into four different categories. In these measurements no permanent surface damage of melanosomes was observed as revealed by imaging before and after indentation measurements. The indentation measurements that exhibited nearly elastic responses were used to determine the Young's modulus of melanosomes. The average Young's modulus values are similar for 14-year-old and 76-year-old melanosomes with a somewhat narrower distribution for the 14-year-old sample. These elastic modulus values are considerably higher than the modulus of organelles with cytoplasm (<1 MPa) and approaching values of the modulus of protein crystals (,100 MPa) indicating rather high packing density of biologic material in melanosomes. The width of the Young's modulus distributions is considerable spanning from few megapascals to few tens of megapascals indicating large heterogeneity in the structure. A fraction of the force curves cannot be described by the homogeneous elastic sample model; these force curves are consistent with ,10 nm structural heterogeneity in melanosomes. The approach-withdraw hysteresis indicates a significant viscoelasticity, particularly in the samples from the 14-year-old sample. Adhesion of the AFM probe was detected on ,3% and ,20% of the surface of 14-year-old and 76-year-old samples, respectively. In light of previous studies on these same melanosomes using photoelectron emission microscopy, this adhesion is attributed to the presence of lipofuscin on the surface of the melanosomes. This suggestion indicates that part of the difference in photochemical properties between the old and young melanosomes originates from surface lipofuscin. [source] Development of Bacteriorhodopsin Analogues and Studies of Charge Separated Excited States in the Photoprocesses of Linear Polyenes,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 1 2007Anil K. Singh Development of bacteriorhodopsin (bR) analogues employing chromophore substitution technique for the purpose of characterizing the binding site of bR and generating bR analogues with novel opto-electronic properties for applications as photoactive element in nanotechnical devices are described. Additionally, the photophysical and photochemical properties of variously substituted diarylpolyenes as models of photobiologically relevant linear polyenes are discussed. The role of charge separated dipolar excited states in the photoprocesses of linear polyenes is highlighted. [source] The Distinct Signaling Mechanisms of Microbial Sensory Rhodopsins in Archaea, Eubacteria and Eukarya,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 1 2007Kwang-Hwan Jung Most of the known archaeal-type microbial rhodopsins are retinal-binding ion transporters, such as bacteriorhodopsin (BR) and proteorhodopsin (PR). Their identification is the result of extensive studies of their photochemical and biophysical properties. The cells containing these pigments, however, use other microbial rhodopsins as photosensors to monitor environmental light signals. From the early studies of sensory rhodopsin I (HsSRI) in Halobacterium salinarum and sensory rhodopsin II (NpSRII) in Natronomonas pharaonis, we now know that several microbial sensory rhodopsins in the other major domain of life relay information on light intensity and quality to the cell. Three of the most studied photosensory transduction mechanisms of these microbial rhodopsins are dealt with in this review. We discuss recent progress in the understanding of genomic organization, photochemical properties and photosignaling mechanisms with respect to biological function. [source] Photoreactivity of the Nonsteroidal Anti-inflammatory 2-Arylpropionic Acids with Photosensitizing Side Effects,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 5 2001Francisco Boscá ABSTRACT The photoreactivity of the nonsteroidal anti-inflammatory 2-arylpropionic acids benoxaprofen, carprofen, naproxen, ketoprofen, tiaprofenic acid, and suprofen is reviewed with special emphasis on fundamental photophysical and photochemical properties. The absorption and emission properties of the excited states of these drugs as well as their main photodegradation routes are summarized. The photochemical mechanisms are discussed on the basis of product studies and detection of short-lived intermediates by means of laser flash photolysis. After dealing with the unimolecular processes, attention is focused on the photosensitized reactions of key biomolecules, such as lipids, proteins or nucleic acids. Finally, a short section on the photobiological effects on simple biological models is also included. Although some earlier citations are included, the literature coverage is in general limited to the last decade. [source] The Effect of Preparation Procedures on the Morphology of Melanin from the Ink Sac of Sepia officinalisPIGMENT CELL & MELANOMA RESEARCH, Issue 1 2003Yan Liu The structure of melanin extracted from the ink sac of the cuttlefish Sepia officinalis was examined for different methods of isolation and purification of the pigment. Scanning electron microscopy (SEM) images of Sepia eumelanin prepared by different procedures establish that multi-,m-sized aggregates reported by previous workers are generated by their sample preparation, and that the dominant constituents of Sepia melanin are ,150 nm spherical granules. Brunauer-Emmett-Teller (BET) measurements reveal that Sepia eumelanin from Sigma (prepared by spray drying the pigment) has a surface area of 14.3 m2/g. Pigment extracted directly from the fresh ink sac and then freeze-dried has a surface area of 21.5 m2/g, while CO2 -supercritically dried has a surface area of 37.5 m2/g. This is consistent with SEM images showing that the process of freeze-drying produces aggregates, but to a lesser extent than spray drying. Supercritical drying of the sample produces suspensions of the individual ,150 nm granule, which is more reflective of the natural pigment. Brunauer-Emmett-Teller surface area analysis and Barrett-Joyner-Halenda (BJH) pore volume analysis indicate that the surface of the granules is not smooth and the interior of the granules is not porous, but rather the aggregates of granules are porous. Ultra-high resolution SEM and atomic force microscopy (AFM) images show the granules are easily deformed and are comprised of smaller constituents. De-aggregation of the granules by sonication and ultra-filtration reveal a range of structures depending on the pore size of the membrane used. The implications of these results on quantifying photochemical properties and kinetic reaction rate constants of melanin are discussed. [source] Synthesis and functional properties of green fluorescent poly(methylmethacrylate) for use in liquid crystal systemsPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 9 2003Ivo Grabchev Abstract The copolymerization of six 4-aminosubstituted-1,8-naphthalimide dyes comprising an allylic polymerizable group with methylmethacrylate has been investigated. The utility of the copolymers prepared as fluorescent component in polymer/liquid crystal systems has been examined. The photophysical and photochemical properties of the systems monomeric dye/liquid crystal and copolymer/liquid crystal have been also discussed. It has been shown that in a liquid crystal mixture 1,8-naphthalimide dyes and respective copolymer/liquid crystals have yellow,green fluorescent color with good photostability. Copyright © 2003 John Wiley & Sons, Ltd. [source] Oxidative Electrochemical Switching in Dithienylcyclopentenes, Part 1: Effect of Electronic Perturbation on the Efficiency and Direction of Molecular Switching,CHEMISTRY - A EUROPEAN JOURNAL, Issue 21 2005Wesley R. Browne Dr. Abstract The electro- and spectroelectrochemical properties of dithienylhexahydro- and dithienyhexafluorocyclopentenes are reported. The large effect of variation in the central cyclopentene moieties on the redox properties of the dithienylcyclopentenes is in striking contrast to the minor effect on their photochemical properties. The electronic properties of the oxidised compounds in the +1 and +2 oxidation state are reported, and the possibility of electrochemical cyclisation and cycloreversion were explored by UV/Vis spectroelectrochemistry. The efficiency of electrochemical switching is found to be dependent both on the central cyclopentene unit and on the nature of the substituents at C5 of the thienyl rings. For the hexahydrocyclopentene-based compounds oxidative ring closure of the ring-open form is observed, while for the hexafluorocyclopentene-based compounds oxidative ring opening of the ring-closed form is observed. However, the introduction of electroactive groups such as methoxyphenyl allows oxidative ring closure to occur in the hexafluoro compounds. The effect of electrolyte, solvent and temperature on the spectroelectrochemical properties were examined, and the switching process was found to be sensitive to the donor properties of the solvent/electrolyte system employed. In addition, thermally activated reversible isomerisation of the dicationic closed form was observed. The driving force for electrochemical ring opening and closure appears to be dependent on the relative stabilisation of the dicationic ring-open and ring-closed states. This study provides insight into the factors which determine the direction of cyclisation. [source] Luminescent Molecular Copper(I) Alkynyl Open Cubes: Synthesis,,Structural,Characterization, Electronic Structure, Photophysics, and PhotochemistryCHEMISTRY - AN ASIAN JOURNAL, Issue 1-2 2006Chui-Ling Chan Dr. Abstract A novel class of tetranuclear copper(I) alkynyl complexes with an "open-cube" structure was synthesized. The crystal structure of [Cu4{P(p -MeC6H4)3}4(,3 -,1,,1,,2 -C,C- p -MeOC6H4)3]PF6 was determined. These complexes were found to display dual emission behavior. Through systematic comparison studies on the electronic absorption and photoluminescence properties of a series of [Cu4(PR3)4(,3 -,1,,1,,2 -C,CR,)3]+ complexes, together with density functional theory (DFT) calculations at the PBE1PBE level on the model complex [Cu4(PH3)4(,3 -,1,,1,,2 -C,C- p -MeOC6H4)3]+, the nature of their emission origins was probed. Their photochemical properties were also investigated by oxidative quenching experiments and transient absorption spectroscopy. [source] Targeting of photosensitizers to head and neck tumours by the use of monoclonal antibodiesCLINICAL OTOLARYNGOLOGY, Issue 4 2001G.A.M.S. Van Dongen Introduction. The objective was to improve the selectivity of photodynamic therapy (PDT) by targeting photosensitizers to tumours by the use of monoclonal antibodies (mAbs). Two sensitizers were selected for this approach. Meta-tetrahydroxyphenylchlorin (mTHPC) was selected because it is one of the most effective photosensitizers in free form. Aluminium (III) phthalocyanine tetrasulphonate [AlPc(SO3H)4] was selected because of its ideal photochemical properties. However, owing to its hydrophilicity, this latter sensitizer is not able to enter the tumour cell and, therefore, in free form is ineffective in PDT. We hypothesized that AlPc(SO3H)4 might become suitable for PDT when coupled to tumour-selective mAbs. Methods. These were developed to couple the sensitizers to mAbs, including mAb 425 directed against the epidermal growth factor receptor. These conjugates were evaluated for efficacy in PDT in vitro and for tumour-targeting capacity in vivo. Results.,In vitro PDT showed that the AlPc(SO3H)4,mAb 425 conjugate was ,7500 times more toxic to A431 cells than the free sensitizer (IC50 values 0.12 nm versus 900 nm), and was also more toxic than the mTHPC,mAb 425 conjugate and free mTHPC (IC50 values 7.3 nm versus 2.0 nm). Biodistribution analysis of the conjugates in tumour-bearing nude mice showed selective accumulation in the tumour. Conclusion. These data show that AlPc(SO3H)4, in particular, has high potential for use in PDT when coupled to tumour-selective mAbs. [source] Applications of silver nanoparticles capped with different functional groups as the matrix and affinity probes in surface-assisted laser desorption/ionization time-of-flight and atmospheric pressure matrix-assisted laser desorption/ionization ion trap mass spectrometry for rapid analysis of sulfur drugs and biothiols in human urineRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 18 2008Kamlesh Shrivas A strategy is presented for the analysis of sulfur drugs and biothiols using silver nanoparticles (AgNPs) capped with different functional groups as the matrix and affinity probes in surface-assisted laser desorption/ionization time-of-flight mass spectrometry (SALDI-TOF MS) and atmospheric pressure-matrix assisted laser desorption/ionization ion trap mass spectrometry (AP-MALDI-ITMS). Biothiols adsorbed on the surface of AgNPs through covalent bonding were subjected to ultraviolet (UV) radiation that enabled desorption and ionization due to the excellent photochemical property of NPs. The proposed method has been successfully applied for the determination of cysteine and homocysteine in human urine samples using an internal standard. The limit of detection (LOD) and limit of quantification (LOQ) for cysteine and homocysteine in urine sample are 7 and 22,nM, respectively, with a relative standard deviation (RSD) of <10%. The advantages of the present method compared with the methods reported in the literature for biothiol analysis are simplicity, rapidity and sensitivity without the need for time-consuming separation and tedious preconcentration processes. Additionally, we also found that the bare AgNPs can be directly used as the matrix in MALDI-TOF MS for the analysis of sulfur drugs without the addition of an extra proton source. Copyright © 2008 John Wiley & Sons, Ltd. [source] | |||||||||||||||||||||||||