629 research outputs found
Complexes of tetracyclines with divalent metal cations investigated by stationary and femtosecond-pulsed techniques
No full textPhysical Chemistry Chemical Physics
Volume 14, Issue 2, 14 January 2012, Pages 823-834
Complexes of tetracyclines with divalent metal cations investigated by stationary and femtosecond-pulsed techniques (Article)
Carlotti, B., Cesaretti, A., Elisei, F.
Chemistry Department, Centro di Eccellenza sui Materiali Innovativi Nanostrutturati (CEMIN), University of Perugia, via Elce di Sotto 8, 06123 Perugia, Italy
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Abstract
Spectroscopic techniques both in steady-state (in absorption and emission) and pulsed (absorption of excited states with femtosecond resolution) conditions were used to study the complexation process between six molecules belonging to the tetracycline family and Mg 2+; in the case of TC the study was extended to the metal ions Ca 2+ and Cu 2+. The study was carried out in aqueous solution at various pH values, where one acid-base form of the substrate prevails over the others. The processing of experimental results, performed by means of Singular Value Decomposition and Global Analysis methods, allowed us to evaluate the extent of interaction through the association constants, to identify the number of equilibria present in solution and the stoichiometry (11 or 12) of the tetracyclinemetal ion complex, and to define the spectral and photophysical properties of the latter (in terms of fluorescence quantum yields, lifetimes and rate constants). In fact, the (allowed) radiative decay process is a minor root for the lowest excited state of the complexes which mainly decay to the ground state by internal conversion. Details of the complexation sites are proposed for the various protonated forms of tetracyclines, and for the various cations in the case of TC. In particular, the molecular structure seems to affect significantly the dynamics of interaction when the upper peripheral region of tetracycline is rich in additional hydroxyl groups. Moreover, the state of protonation of the substrate produces changes in the order of the complexation sites, whose affinity for the cation increases significantly when they are negatively charged owing to the loss of protons. Magnesium and calcium (hard cations) give similar interactions, at least in acid solution, while copper(ii) (borderline cation) binds more efficiently on different sites, thus forming complexes with different properties
Fast and ultrafast spectroscopic investigation of tetracycline derivatives in organic and aqueous media
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Lower rim amide (1, 3) functionalised calix [4] arene amido-thiourea derivatives as dimetallic Zn (II) coordination complexes for anion recognition/sensing
No full textA laser flash photolytic study of para-methoxytoluene cation radicals. The effect of -substituents on the proton transfer reactions
No full textHydrogen Production from Water by Photolysis, Sonolysis and Sonophotolysis with Solid Solutions of Rare Earth, Gallium and Indium Oxides as Heterogeneous Catalysts
No full textIn this work, we present the hydrogen production by photolysis, sonolysis and sonophotolysis of water in the presence of newly synthesized solid solutions of rare earth, gallium and indium oxides playing as catalysts. From the experiments of photolysis, we found that the best photocatalyst is the solid solution Y0.8Ga0.2InO3 doped by sulphur atoms. In experiments of sonolysis, we optimized the rate of hydrogen production by changing the amount of water, adding ethanol and tuning the power of our piezoelectric transducer. Finally, we performed sonolysis and sonophotolysis experiments in the presence of S:Y0.8Ga0.2InO3 finding a promising synergistic effect of UV-visible electromagnetic waves and 38 kHz ultrasound waves in producing H2
An acridinium-based sensor as a fluorescent photoinduced electron transfer probe for proton detection modulated by anionic micelles
No full textA water-soluble fluorescent pH sensor of 9-amino-10-methylacridinium chromophore with the
2-(diethylamine)ethyl chain as a receptor shows an “off–on” response going from basic to acidic solution.
Photoinduced electron transfer has been directly demonstrated to be the quenching mechanism by the
observation of the long-lived acridinyl radical. The interaction of the protonated sensor with anionic
micelles causes a significant increase in the detection sensitivity of pH
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