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Chemistry (Weinheim An Der Bergstrasse,... Mar 2012The photochemistry of iron azido complexes is quite challenging and poorly understood. For example, the photochemical decomposition of [Fe(III)N(3)(cyclam-ac)]PF(6)...
The photochemistry of iron azido complexes is quite challenging and poorly understood. For example, the photochemical decomposition of [Fe(III)N(3)(cyclam-ac)]PF(6) ([1]PF(6)), where cyclam-ac represents the 1,4,8,11-tetraazacyclotetradecane-1-acetate ligand, has been shown to be wavelength-dependent, leading either to the rare high-valent iron(V) nitrido complex [Fe(V)N(cyclam-ac)]PF(6) ([3]PF(6)) after cleavage of the azide N(α)-N(β) bond, or to a photoreduced Fe(II) species after Fe-N(azide) bond homolysis. The mechanistic details of this intriguing reactivity have never been studied in detail. Here, the photochemistry of 1 in acetonitrile solution at room temperature has been investigated using step-scan and rapid-scan time-resolved Fourier transform infrared (FTIR) spectroscopy following a 266 nm, 10 ns pulsed laser excitation. Using carbon monoxide as a quencher for the primary iron-containing photochemical product, it is shown that 266 nm excitation of 1 results exclusively in the cleavage of the Fe-N(azide) bond, as was suspected from earlier steady-state irradiation studies. In argon-purged solutions of [1]PF(6), the solvent-stabilized complex cation [Fe(II)(CH(3)CN)(cyclam-ac)](+) (2red) together with the azide radical (N(3)(.)) is formed with a relative yield of 80%, as evidenced by the appearance of their characteristic vibrational resonances. Strikingly, step-scan experiments with a higher time resolution reveal the formation of azide anions (N(3)(-)) during the first 500 ns after photolysis, with a yield of 20%. These azide ions can subsequently react thermally with 2red to form [Fe(II)N(3)(cyclam-ac)] (1red) as a secondary product of the photochemical decomposition of 1. Molecular oxygen was further used to quench 1red and 2red to form what seems to be the elusive complex [Fe(O(2))(cyclam-ac)](+) (6).
Topics: Crystallography, X-Ray; Ferric Compounds; Heterocyclic Compounds; Models, Molecular; Molecular Conformation; Molecular Structure; Photochemistry; Spectroscopy, Fourier Transform Infrared
PubMed: 22298314
DOI: 10.1002/chem.201103294 -
[Hokenfu Zasshi] the Japanese Journal... Nov 1971
Topics: Photochemistry; Smog
PubMed: 5211668
DOI: No ID Found -
Chemical Society Reviews Feb 2014Fluorescence provides a mechanism for achieving contrast in biological imaging that enables investigations of molecular structure, dynamics, and function at high spatial... (Review)
Review
Fluorescence provides a mechanism for achieving contrast in biological imaging that enables investigations of molecular structure, dynamics, and function at high spatial and temporal resolution. Small-molecule organic fluorophores have proven essential for such efforts and are widely used in advanced applications such as single-molecule and super-resolution microscopy. Yet, organic fluorophores, like all fluorescent species, exhibit instabilities in their emission characteristics, including blinking and photobleaching that limit their utility and performance. Here, we review the photophysics and photochemistry of organic fluorophores as they pertain to mitigating such instabilities, with a specific focus on the development of stabilized fluorophores through derivatization. Self-healing organic fluorophores, wherein the triplet state is intramolecularly quenched by a covalently attached protective agent, exhibit markedly improved photostabilities. We discuss the potential for further enhancements towards the goal of developing "ultra-stable" fluorophores spanning the visible spectrum and how such fluorophores are likely to impact the future of single-molecule research.
Topics: Fluorescent Dyes; Microscopy, Fluorescence; Models, Molecular; Optical Imaging; Photochemistry
PubMed: 24177677
DOI: 10.1039/c3cs60237k -
Journal of the American Chemical Society Nov 2004A combination of hydrophobic forces and guest templation drive the assembly of cavitands into molecular capsules. Encapsulated guests such as dibenzyl ketones reside in...
A combination of hydrophobic forces and guest templation drive the assembly of cavitands into molecular capsules. Encapsulated guests such as dibenzyl ketones reside in an essentially dry environment, and upon irradiation, undergo rearrangement processes that are templated by the shape of the 1 nm x 2 nm cavity.
Topics: Hydrophobic and Hydrophilic Interactions; Ketones; Magnetic Resonance Spectroscopy; Nanotechnology; Photochemistry; Propane; Pyrenes; Spectrometry, Fluorescence
PubMed: 15521751
DOI: 10.1021/ja0450197 -
Nature Reviews. Molecular Cell Biology Nov 2005The fluorescence characteristics of photoactivatable proteins can be controlled by irradiating them with light of a specific wavelength, intensity and duration. This... (Review)
Review
The fluorescence characteristics of photoactivatable proteins can be controlled by irradiating them with light of a specific wavelength, intensity and duration. This provides unique possibilities for the optical labelling and tracking of living cells, organelles and intracellular molecules in a spatio-temporal manner. Here, we discuss the properties of the available photoactivatable fluorescent proteins and their potential applications.
Topics: Animals; Fluorescence; Luminescent Proteins; Photochemistry
PubMed: 16167053
DOI: 10.1038/nrm1741 -
Organic Letters Jan 2024Photooxygenation of flavonoids leads to the release of carbon monoxide (CO). Our structure-photoreactivity study, employing several structurally different flavonoids,...
Photooxygenation of flavonoids leads to the release of carbon monoxide (CO). Our structure-photoreactivity study, employing several structurally different flavonoids, including their C-labeled analogs, revealed that CO can be produced via two completely orthogonal pathways, depending on their hydroxy group substitution pattern and the reaction conditions. While photooxygenation of the enol 3-OH group has previously been established as the CO liberation channel, we show that the catechol-type hydroxy groups of ring B can predominantly participate in photodecarbonylation.
Topics: Carbon Monoxide; Flavonoids; Photochemistry
PubMed: 38227978
DOI: 10.1021/acs.orglett.3c04141 -
Environment International Jul 2006The photochemistry of a major commercial polybrominated diphenyl ether (PBDE) flame retardant congener, 2,2',4,4',5,5'-hexabromodiphenyl ether (BDE153), was investigated...
The photochemistry of a major commercial polybrominated diphenyl ether (PBDE) flame retardant congener, 2,2',4,4',5,5'-hexabromodiphenyl ether (BDE153), was investigated in acetonitrile, distilled water, and seawater. After a short irradiation period in acetonitrile at 302 nm, the major photoproducts of BDE153 included 2,2',4,4',5-(BDE99), 2,2',4,5,5'-(BDE101), and 2,4,4',5,5'-(BDE118) substituted penta-BDEs as primary photohydrodebromination products, 2,2',4,4'-(BDE47), 3,3',4,4'-(BDE77), 2,3',4,4'-(BDE66), and 2,2',4,5'-(BDE49) substituted tetra-BDEs as secondary photohydrodebromination products, a suite of non-2,3,7,8-substituted mono- through penta-brominated dibenzofurans, and three tetrabrominated 2-hydroxybiphenyl congeners. By comparison, irradiation in distilled water and seawater gave increased relative photohydrodebromination contributions and no evidence for the formation of brominated dibenzofurans or 2-hydroxybiphenyls. In all solvent systems, subsequent degradation of primary and secondary photoproducts under continuing irradiation led to a steadily decreasing reaction mass balance. The results suggest a short photochemical half-life for BDE153 in aquatic systems, with rapid photohydrodebromination to some of the most prevalent penta- and tetra-brominated diphenyl ether congeners typically observed in environmental matrices.
Topics: Flame Retardants; Halogenated Diphenyl Ethers; Phenyl Ethers; Photochemistry; Polybrominated Biphenyls; Water Pollutants, Chemical
PubMed: 16581124
DOI: 10.1016/j.envint.2006.01.009 -
Nature Feb 1989The development of photolabile caged neurotransmitters has made possible the study of the split-second kinetics of receptor-ligand interactions. An instrument has now...
The development of photolabile caged neurotransmitters has made possible the study of the split-second kinetics of receptor-ligand interactions. An instrument has now been developed for activating the neurotransmitter and measuring the neuron's response.
Topics: Animals; Carbachol; Kinetics; Neurons; Neurotransmitter Agents; Photochemistry; Photolysis; Receptors, Cholinergic
PubMed: 2563570
DOI: 10.1038/337583a0 -
ChemSusChem Feb 2011
Topics: Carbon Dioxide; Catalysis; Electrochemistry; Energy-Generating Resources; Metals; Oxides; Photochemistry; Solar Energy; Water
PubMed: 21328547
DOI: 10.1002/cssc.201100040 -
Angewandte Chemie (International Ed. in... Jul 2015
Topics: Biochemistry; Chemistry; Chemistry Techniques, Synthetic; Germany; History, 20th Century; History, 21st Century; Humans; Photochemistry; Steroids
PubMed: 26119794
DOI: 10.1002/anie.201504950