The photocatalytic decomposition of phenol in oxygenated aqueous suspensions of lightly-reduced anatase TiO2, being the most satisfactory among the semiconductors investigated from the standpoint of the photocatalytic activity and stability, has been investigated at the optimum pH 3.5. The products at the initial stage of the reaction were hydroquinone, pyrocatechol, 1,2,4-benzenetriol, pyrogallol, and 2-hydroxy-1,4-benzoquinone. These intermediates underwent further photocatalytic oxidation via acids and/or aldehydes finally into CO2 and H2O. A reaction scheme involving hydroxyl radicals as real reactive species has been proposed. Although H2O2 was formed via O2\ewdot produced by electron trapping of adsorbed oxygen, its concentration remained constant at a low value during the reaction. About 0.7 mole of O2 was consumed for the consumption of one mole of phenol at the initial stage of the reaction. These results indicated that hydroxyl radicals were formed not only via holes but also via H2O2 from O2\ew...

Heterogeneous Photocatalytic Decomposition of Phenol over TiO2 Powder

Lanthanides(III) and actinides(III) belong to hard elements, preferably bound in complexation reactions to the hard oxygen donor atoms. Correspondingly, studies of complexation of these elements in solutions were until the 1980s performed with complexants bonding the complexed metal ion either exclusively to oxygen atoms or to both oxygen and nitrogen atoms. Such complexes may be very stable in solution, but high stability is not the only property desired. Complexation is a very useful tool for separation of metal ions, if utilized in systems involving two immiscible phases. In such cases, the selectivity of the complexation is a characteristic as valuable or still more valuable.

Complexation and separation of lanthanides(III) and actinides(III) by heterocyclic N-donors in solutions.

Remarkably versatile chemistry of Bodipy dyes allows the design and straightforward synthesis of multivalent-multitopic derivatives, which, with judicious selection of metal ion-ligand pairs based on known affinities, affords control and manipulation of photoinduced electron transfer and internal charge transfer processes as desired. We have demonstrated that metal ions acting as modulators (or inputs, in digital design parlance) can generate absorbance changes in accordance with the operation of a half-adder. In addition, an AND logic gate in the emission mode was delivered using a different binucleating arrangement of ligands. A molecular equivalent of a three-input AND logic gate was also obtained exploiting differential binding affinities of metal ions for different ligands. The results suggest that different metal ions can be used as nonannihilating inputs, selectively targeting various ligands incorporated within a single fluorophore, and with careful design, diverse photophysical processes can be selectively modulated, resulting in a range of signals, useful in molecular logic design, and offering an enticing potential for multianalyte chemosensors.

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Selective Manipulation of ICT and PET Processes in Styryl-Bodipy Derivatives: Applications in Molecular Logic and Fluorescence Sensing of Metal Ions

Selective alkane transformations via radicals and radical cations: insights into the activation step from experiment and theory.

Excitation energy transfer, when coupled to an ion-modulated ICT chromophore, creates novel opportunities in sensing. The direction of energy transfer and the point of ICT modulation can be varied as desired. In our previous work, we have shown that energy transfer efficiency between two energetically coupled fluorophores will be altered by the metal ion binding to the ICT chromophore carrying a ligand. There are two beneficial results: increased pseudo-Stokes shift and expanded dynamic range. Here, we explored the consequences of the modulation of energy transfer efficiency at the energy donor site, in a molecular design which has an ICT type metal ion-sensitive chromophore placed as the energy donor in the dyad. Clear advantages emerge compared to the acceptor site modulation: unaltered emission wavelength in the red end of the visible spectrum, while keeping a large Stokes shift and the ratiometric character.

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Design strategies for ratiometric chemosensors: modulation of excitation energy transfer at the energy donor site.

A method has been described for the spectrophotometric determination of 20 to 100μg. of a rare earth element using xylenol orange. The complexes of cerium(III), lanthanum-(III), neodymium(III) and yttrium(III) with xylenol orange have an absorption maximum at 575 to 578μ vs. the reagent blank. Each of them is a 1 : 1 complex and has a formation constant of approximately 105 under the conditions studied. Anions such as NTA and EDTA inhibit the color development of the complexes.

Spectrophotometric Determination of Cerium(III) and Some Rare Earths with Xylenol Orange

Cyclic and acyclic dithiamonoaza, tetrathiamonoaza, and tetrathiadiaza analogs of polyethers bearing a hydrazone moiety on nitrogen atom(s) were synthesized. Their acidity constants in 1,4-dioxane–water solution and stability constants of hydrazones derived from dithiamonoaza and tetrathiamonoaza analogs of polyethers for some heavy metal ions in same acidic media were measured spectrophotometrically. Hydrazones of cyclic and acyclic tetrathiamonoaza series had highly Ag+-selective complexability.

Hydrazones Derived from Dithiamonoaza and Tetrathiamonoaza Analogs of Polyethers as Silver Ion Selective Ionophores: Syntheses, Proton-Dissociation Behaviors, and Metal Ion Complexing Properties in 1,4-Dioxane–Water Acidic Solution

Dithiazacrown, tetrathiazacrown, and two tetrathiadiazacrown ether derivatives, bearing a phenyl group on each nitrogen atom at the periphery, were synthesized, and the solvent extractions of some transition metal ions with these compounds were carried out using an H2O–1,2-dichloroethane system. All of the thiazacrown compounds employed exhibited Ag+ selectivity, and formed 1 : 1 : 1 complexes of Ag+ : ligand : laurate ion as a counter anion to be extracted into a 1,2-dichloroethane solution. The extractabilities (extraction constants, Kex) for Ag+ decreased in the order: 7,16-diphenyltetrathia-7,16-diaza-18-crown-6 (3) (log Kex = 1.18 ± 0.13) > 13-phenyltetrathia-13-aza-15-crown-5 (2) (0.75 ± 0.09) > 7-phenyldithia-7-aza-9-crown-3 (1) (−0.47 ± 0.06) > 13,16-diphenyltetrathia-13,16-diaza-18-crown-6 (4) (−0.62 ± 0.16).

Silver Ion Selective Extraction with Dithiaza-, Tetrathiaza-, and Tetrathiadiazacrown Ether Derivatives.

Aluminum reacts with xylenol orange in a slightly acidic solution to form two red complexes which are in equilibrium with each other. At pH 3.4±0.1, Beer’s law is obeyed up to an aluminum concentration of 1.0 p.p.m. in 1 cm. absorption cells. The absorbance was measured at the isosbestic point of 536 mμ. The molar extinction coefficient was found to be 21100. This method seems to be the most favorable one for aluminum determination if the aluminum is first separated from any interfering ions. The composition of the complexes has also been discussed.

The Spectrophotometric Determination of Aluminum with Xylenol Orange

Liquid membranes containing cyclic and acyclic tetrathiazaalkanes bearing a hydrazone moiety as a proton-dissociable group exhibited effective uphill silver ion transport behavior in the proton-driven cation transport. Excellent silver ion selectivities relative to other class ab and class b metal ions were observed for these membranes when citric acid was used for adjusting pH and for preventing hydrolysis of several metal ions in the source phase. Complete recovery of silver ion from a silver solder sample was selectively achieved using the liquid membrane containing acyclic tetrathiazaalkane hydrazone.

Makoto Otomo

Papers

Spectrophotometric Determination of Cerium(III) and Some Rare Earths with Xylenol Orange

Hydrazones Derived from Dithiamonoaza and Tetrathiamonoaza Analogs of Polyethers as Silver Ion Selective Ionophores: Syntheses, Proton-Dissociation Behaviors, and Metal Ion Complexing Properties in 1,4-Dioxane–Water Acidic Solution

Silver Ion Selective Extraction with Dithiaza-, Tetrathiaza-, and Tetrathiadiazacrown Ether Derivatives.

The Spectrophotometric Determination of Aluminum with Xylenol Orange

Highly Silver Ion-selective Transport Through Liquid Membranes Containing Cyclic and Acyclic Polythiamonoazaalkanes Bearing an Easily Ionizable Moiety