- Adiabatic Photodehydroxylation of 9-Phenylxanthen-9-ol. Observation of Carbocation Fluorescence in Neutral Aqueous Solution
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The photobehavior of the title compound (1) has been studied in aqueous solution and organic solvents.Evidence is presented that shows that 1 undergoes adiabatic photodehydroxylation in aqueous solution - it being the first example of a new class of adiab
- Wan, Peter,Yates, Keith,Boyd, Mary K.
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- Simple and modular design platform of bimodal turn-on chemodosimeters for oxophilic metal cations
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The selective chemodosimetric behaviour towards oxophilic metal cations of three compounds in one modular platform is explored. Each exhibits turn-on visible colour and emission, while two offer ratiometric emission profiles. The highest performer exhibits 3000-fold enhancement in visible-light emission per equivalent of metal cation.
- Hogan, David T.,Sutherland, Todd C.
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supporting information
p. 16469 - 16473
(2018/10/23)
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- Kinetic, thermodynamic and mechanistic studies on the reduction of carbenium ions by NAD(P)H analogues
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Hydride transfer mechanisms of the reductions of xanthylium ion by NAD(P)H analogues (i.e. BNAH, HEH and AcrH2) were investigated. Both the kinetic observations and an analysis of thermodynamic driving forces for each mechanistic step in all the possible mechanisms indicate that the reductions are initiated by a rate-determining electron transfer, followed by a fast hydrogen atom abstraction. The mechanism of the reductions of 9-phenylxanthylium and triphenylmethylium ions by BNAH were also investigated and are similarly discussed.
- Cheng, Jin-Pei,Lu, Yun
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p. 577 - 584
(2007/10/03)
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- Characterization of the triplet excited state of the phenylxanthenium carbocation
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The triplet excited state of the 9-phenylxanthenium cation has been observed directly by both luminescence and transient absorption techniques.The triplet-triplet absorption shows λmax /= 300 nm and decays over a period of several microseconds in the absence of easily oxidized donors.The triplet cation reacts with 9-phenylxanthydrol and biphenyl via electron transfer to give the corresponding radical and radical cation and also reacts rapidly with both oxygen and 1,3-cyclohexadiene. Key words: carbocations, triplets, electron transfer, laser flash photolysis.
- Johnston, L. J.,Wong, D. F.
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p. 280 - 282
(2007/10/02)
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- Heterolysis and homolysis energies for some carbon-oxygen bonds
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Methods described previously for obtaining heterolysis (ΔHhet) and homolysis (ΔHhomo) enthalpies for bonds that can be cleaved to produce resonance-stabilized carbenium ions, anions, and radicals are extended to the study of carbon-oxygen bonds through the reactions of resonance-stabilized carbenium ions with substituted phenoxide ions. Titration calorimetry was used to obtain the heat of heterolysis, and the second-harmonic ac voltammetry (SHACV) method was used to obtain reversible oxidation potentials for the anions. In several cases, the electrode reactions were so fast that reversible potentials were obtained only with the greatest difficulty. Nonetheless, there is remarkably good agreement between these oxidation potentials for phenoxide ions obtained by electrochemical methods in sulfolane solution and those reported by others using entirely different techniques in different media. Such agreement provides unprecedented evidence for the soundness of the various methods used to study redox potentials of organic ions and radicals. As before, a wide variety of correlations was tested between ΔHhet and ΔHhomo. These two properties showed little correlation with each other, but ΔHhet gave good correlations between many properties for which neutral species are converted into ions or vice versa, such as redox potentials of both types of ions, the pKas of the anions, or the free energies of electron transfer. In contrast to the earlier study of cleavage to carbanions and carbenium ions, the present ΔHhet values are predicted well by a general equation that employs the pKR+ of the carbenium ion (without modification) and the pKa of the phenol. The improvement is consistent with the fact that the cleavage of carbon-oxygen bonds of the triarylcarbinols used to establish the pKR+ stability scale is a more appropriate model for the heterolysis of carbon-oxygen bonds in sulfolane at 25°C than it is for the cleavage of carbon-carbon bonds under the same conditions.
- Arnett, Edward M.,Amarnath, Kalyani,Harvey, Noel G.,Venimadhavan, Sampath
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p. 7346 - 7353
(2007/10/02)
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- Electrophilic Reactions of Xanthylium Carbocations Produced by Flash Photolysis of 9-Xanthenols
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The xanthylium ion and eight 9-aryl derivatives (p-MeO, p-Me, m-Me, H, p-F, m-MeO, p-Cl, and p-CF3 phenyl) were produced in 1:4 acetonitrile/water by flash photolysis of the corresponding 9-xanthenols.The identifications of the transients as xanthylium ca
- McClelland, Robert A.,Banait, Narinder,Steenken, Steen
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p. 2929 - 2935
(2007/10/02)
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- A Laser Flash Photolysis Study of Photodehydroxylation Phenomena of 9-Phenylxanthen-9-ol and Photobehavior of Related Intermediates. Enhanced Electrophilicity of 9-Phenylxanthenium Cation Singlet
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In the course of 248-nm laser photolysis, solutions of 9-phenylxanthen-9-ol (1) undergo homolytic and heterolytic photodehydroxylation, the relative efficiency of which depends strongly on the solvent nature.Polar/hydroxylic solvents, particularly aqueous
- Minto, Robert E.,Das, Paritosh K.
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p. 8858 - 8866
(2007/10/02)
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- Bio-organic Applications of Mass Spectrometry. Part 6. Selective Deprotection of Nucleotides by Fast Atom Bombardment Mass Spectrometry
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The fully protected nucleoside S-methyl O-2,4-dichlorophenyl phosphorothioates (2) and (3) undergo selective removal of the protecting groups when exposed, in liquid matrices, to 9.5 KeV Xe bombardment.Dimethoxytrityl and 9-phenylxanthen-9-yl cations are formed when the reactivity of the protonated species is examined, while solvolytic removal of the 2,4-dichlorophenyl protecting group afforded the nucleosides phosphodiester anions (6) and (8) as a result of matrix-substrate interaction in the energized condensed phase.The same substrates are competitively demethylated at the sulphur atom when thioglycerol is present in the solvation sphere of the reactants.Anions (6) and (8), desorbed into the gas phase by fast atom bombardment of their triethylammonium salts, displayed the same metastable ion kinetic energy spectra as those produced from nucleotides (2) and (3) by applying the same methodology.
- Liguori, Angelo,Sindona, Giovanni,Uccella, Nicola
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p. 1661 - 1666
(2007/10/02)
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