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The fluorescence intensity of 7- methoxycoumarin (7MC) in aqueous solution is found to significantly decrease upon addition of various cyclodextrins. This observed phenomenon is described as fluorescence suppression, to distinguish it from fluorescence reduction via bimolecular quenching. The decrea...
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The S1 population decay times of azulene and 4,6,8-trimethylazulene have been measured in solvents with a wide range of viscosities using a two-photon, two-color, pump-probe method. The S, lifetimes vary as expected on the basis of the energy gap law. No effect of solvent viscosity is observed, cont...
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Abstract: The title ketene 2 has been generated by laser flash photolysis and observed in solution for the first time, using time-resolved infrared spectroscopy. The kinetics of the reactivity of 2 with H2O, MeOH, and Et2NH with relative reactivities of 1.0, 2.0, and 73 have been measured. These are...
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Abstract: Laser flash photolyses of 2-, 3-, and 4-diazoacetylpyridines 8 give the corresponding pyridylketenes 7 formed by Wolff rearrangements, as observed by time-resolved infrared spectroscopy, with ketenyl absorptions at 2127, 2125, and 2128 cm-1, respectively. Photolysis of 2-, 3-, and 4-8 in C...
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Abstract: This work describes the fluorescence enhancement of the probes 2,6- and 1,8-ANS via complexation with the macrocyclic host cucurbit[7]uril (Q7). The association of these two guests with the Q7 host has been studied using fluorescence, 1H NMR spectroscopy, and molecular modeling. In the cas...
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Laser flash photolysis of 9-hydroxy-9-fluorenecarboxylic acid in hexafluoro-2-propanol (HFIP) generates a transient with lambda(max) at 495 nm that reacts with nucleophiles such as methanol and bromide and is insensitive to oxygen. In the presence of 0.15 M trifluoroacetic acid, a different transien...
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The C=O stretching vibration appears in the infrared spectra of 2-naphthaldehyde (1), 2-acetonaphthone (2), 2-naphthoic acid (3), methyl 2-naphthoate (4) and 1,2-dihydro-3H-benz[e]inden-3-one (5) in the state T-1(pi pi*) between 1600 and 1700 cm(-1). There is a strong line in the Raman spectrum of 1...
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Azinphos-methyl (AZM) is a widely used organophosphate insecticide and acaricide, with demonstrated negative impacts on the environment. Upon absorption of UV-A radiation, this molecule undergoes photolysis to the highly fluorescent compound N-methylanthranilic acid, which undergoes subsequent photo...
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The macrocyclic ligand cyclam occurs as a 70:30 mixture of its trans-I and trans-II configurations, respectively, when included as its CuII complex inside the cavity of the macrocyclic host compound cucurbit[8]uril. This is the first report of an unsubstituted cyclam occurring in either of these two...
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The S-1 population decay times of azulene and 1,4-dimethyl-7-isopropylazulene (guaiazulene) in solution have been determined as a function of their initial vibrational energy content, E(vib)(i), using a pump-probe experiment with subpicosecond time resolution. The S-1 lifetime of azulene does not de...
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This work describes the fluorescence enhancement of the anilinonaphthalene sulfonate probes 1,8-ANS, 2,6-ANS, and 2,6-TNS via complexation with PAMAM dendrimer hosts of Generation 4, 5 and 6. The use of this set of three very closely related probes allows for comparative binding studies, with specif...
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Abstract: Photolysis of N-nitrosamines in acidic acetonitrile produces aminium radical cations via protonation of the initially-formed aminyl radicals. The kinetics of these species can be monitored by transient UV spectroscopy via their absorption band which is found at ca. 300 nm in the case of th...
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We report the first use of fluorescence spectroscopy to probe the environment of the cavities that are present in open framework coordination polymers.
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Abstract: A solid precipitate is formed immediately upon the mixing of aqueous salt solutions of the fluorescence probe 1-anilino-8-naphthalenesulfonate (1,8-ANS) and the cage compound cucurbituril. The resulting solid compound is highly fluorescent, with a maximum emission at ca. 478 nm. Single cry...
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Abstract: The interconversion of cyclobutene-1,2-diones (1) and 1,2-bisketenes (RC=C=O)2 (2) has been surveyed for different combinations of substituents R = H, Me, t-Bu, Ph, Me3Si, CN, Cl, Br, R1O, alkynyl, and PhS. The bisketenes 2 have been generated by flash photolysis, and the kinetics of their...
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The polarity-sensitive fluorescent dye Nile Red forms association complexes with various cyclodextrins in aqueous solution. The formation of such association complexes has a significant effect on the Nile Red fluorescence, with the largest effect being observed in gamma-cyclodextrin solution. When g...