Fluorescent PET (photoinduced electron transfer) sensors are considered to be those molecular systems where the binding of ions and other species leads to the perturbation of the competition between the de-excitation pathways of fluorescence and electron transfer. The early developments in this field are traced and the design logic of these sensors is detailed. A variety of examples drawn from different areas of chemistry are classified according to the ‘fluorophore-spacer-receptor’ format and their photophysical behaviour is rationalized in terms of fluorescent PET sensor principles. Cases are pointed out where such experimental data are unavailable but desirable. During these discussions, the relevance of twisted fluorophore-receptor systems and the contrast with integrated fluorophore-receptor systems is noted. The utility of the fluorescence ‘on-off’ phenomenon in these PET sensors for the area of molecular photoionic devices is pointed out.

Fluorescent PET (photoinduced electron transfer) sensors

A power system having a power converter with an adaptive controller. The power system is coupled to a load and includes a power system controller that receives a signal indicating a system operational state of the load and selects a power converter operational state as a function thereof. The power system also includes a power converter with a power switch that conducts for a duty cycle to provide a regulated output characteristic at an output thereof. The power converter also includes a controller that receives a command from the power system controller to enter the power converter operational state and provides a signal to control the duty cycle of the power switch as a function of the output characteristic and in accordance with the command, thereby regulating an internal operating characteristic of the power converter to improve an operating efficiency thereof as a function of the system operational state.

Power system with power converters having an adaptive controller

A controller for a power converter and method of operating the same employable with a bridge rectifier having first and second synchronous rectifier switches. In one embodiment, the controller includes an amplifier configured to enable a turn-on delay for the first synchronous rectifier switch. The controller also includes a discharge switch having first and second switched terminals coupled to gate and source terminals, respectively, of the first synchronous rectifier switch and configured to discharge a gate-to-source capacitance of the first synchronous rectifier switch to enable a turn off thereof.

Controller for a synchronous rectifier switch

A series of donor-substituted 1,3,5-triaryl-2-pyrazoline fluorophores were structurally characterized by X-ray analysis, and their photophysical properties studied by steady-state absorption and emission spectroscopy. The photoinduced electron-transfer thermodynamics of the derivatives was estimated on the basis of the spectroscopic data and redox potentials of the fluorophores. The aryl substituents in the 1- and 3-position of the pyrazoline ring influence the photophysical properties of the fluorophores in distinctly different ways. The excited-state equilibrium energy ΔE00 is primarily influenced by changes of the substituent in the 1-position, whereas the reduction potential of the fluorophore is essentially determined by the 3-aryl group. Density functional calculations were used to probe the electronic structure and energy ordering of the emissive and the electron-transfer state. The results from the computational analysis agree qualitatively well with the experimental data. In addition, we have eva...

Tuning the photoinduced electron-transfer thermodynamics in 1,3,5-triaryl-2-pyrazoline fluorophores: X-ray structures, photophysical characterization, computational analysis, and in vivo evaluation.

A power converter employing a tapped inductor and method of operating the same. In one embodiment, the power converter includes first and second tapped inductors including a tapped winding having a first section and a second section with a tap therebetween. The power converter also includes first and second active phase legs including a main switch series-coupled with an input node of the power converter and the first section of the tapped windings of the first and second tapped inductors, respectively. The first and second active phase legs also include an auxiliary switch interposed between the second section of the tapped windings of the first and second tapped inductors, respectively, and an output node of the power converter.

Power converter employing a tapped inductor and integrated magnetics and method of operating the same

A method for protecting synthetic and natural fibres against phototendering. The method comprises treating the fibres with a substituted benzotriazolesulfonate of formula (A) wherein (I) R1 is hydrogen or halogen, R2 is hydrogen or alkyl, R3 is hydrogen or hydroxy, R4 is -SO3X where X is hydrogen or an alkali metal, and R5 is hydrogen, with the proviso that R2 is not methyl when R1 and R3 are hydrogen; or (II) R1, R3 and R4 are hydrogen, R2 is -SO3X where X is hydrogen or an alkali metal, and R5 is -OR6 where R6 is hydrogen or alkyl; or (III) R1 is hydrogen or halogen, R2 is -SO3X where X is hydrogen or an alkali metal, R3 and R5 are hydrogen, and R4 is hydrogen, alkyl or benzyl; or (IV) R1 is -SO3X where X is hydrogen or an alkali metal, R2 is alkyl, R3 and R5 are hydrogen, and R4 is hydrogen or alkyl; under acidic conditions. The method is particularly suitable for treating wool, silk and nylon fibres, including blends thereof.

Use of substituted 2-(2'-hydroxyaryl)-2h-benzotriazolesulfonates as photostabilising agents for natural and synthetic fibres

A large number of mono-para-substituted 1,3,5-triphenyl-2-pyrazolines and some related compounds has been synthesized, and their absorption and fluorescence properties in cyclohexane and in methanol measured The effect of substituent on these properties and on the fluorescent whitening ability of the 1,3,5-triphenyl-2-pyrazolines in general is discussed The presence of electron-withdrawing substituents, viz, cyano, methylsulfonyl or methoxycarbonyl groups in the para-position of the phenyl rings, has a dramatic effect on the absorption and the fluorescence properties Such substituents located (a) in the l-phenyl ring give pyrazolines exhibiting brilliant blue fluorescence both in methanolic and cyclohexane solution, (b) in the 3-phenyl ring give highly fluorescent yellow compounds which can be considered as dyes and (c) in the 5-phenyl ring cause drastic quenching of the fluorescence

The preparation and spectral properties of some monosubstituted 1,3,5,-Triphenyl-2-pyrazolines

The reactions of some azoles with o-fluoro-acetophenone , -benzaldehyde and -benzophenone in dimethyl sulfoxide solution in the presence of anhydrous potassium carbonate have been investigated. In addition to the expected substitution products, cyclization reactions frequently occurred to give carbinols in the case of the reactions of o-fluoro-acetophenone and -benzophenone, and cyclic ketones in the case of the reactions with o-fluorobenzaldehyde . Fluoren-9-ol and related carbinols containing heteroaromatic nuclie are readily converted in dimethyl sulfoxide solution into the corresponding ketones by treatment with anhydrous potassium carbonate. When treated with ethanolic alkali, 2′-(benzimidazol-1′-yl) acetophenone undergoes a remarkable transformation to give 1-(2&#82442;-aminophenyl)quinolin-4(1H)-one.

Cyclization Reactions in Azole Chemistry: The Reaction of Some Azoles With o-Fluoroacetophenone, o-Fluorobenzaldehyde and o-Fluorobenzophenone

The effect of substituents on the absorption and fluorescence properties of a number of di-and tri-para-substituted 1,3,5-triphenyl-2-pyrazolines, several substituted 1,3,5,5-tetraphenyl- and trans-l,3,4,5-tetraphenyl-2-pyrazolines, and some 1,3-diphenyl-trans-3a,4,5,6,7,7a-hexahydro-4,7- methano-1H-indazoles in cyclohexane and in methanol has been studied. Certain electron-with-drawing substituents, namely, cyano, methylsulfonyl or methoxycarbonyl, have a marked effect. Such substituents located (A) in the 1-phenyl ring give pyrazolines exhibiting blue fluorescence which is quenched if a cyano group is also present in the 5-phenyl ring, (B) in the 3-phenyl ring give fluorescent yellow compounds which can be considered as dyes, and (c) in the 5-phenyl ring cause quenching of the fluorescence (unless an electron-withdrawing group is also present in the 3-phenyl ring).

The preparation and spectroscopic properties of some di- and tri-substituted 1,3,5-triphenyl-2-pyrazolines and related 2-pyrazolines

The reduction of some representative o-nitrophenylazo dyes in ethanolic alkali with glucose gives the corresponding 2-aryl-2H-benzotriazole 1-oxides in excellent yield. These 1-oxides are rapidly reduced to the parent benzotriazoles at room temperature by means of zinc dust/ethanolic alkali. This method provides a convenient preparation for 5-chlorobenzotriazoles, which are otherwise readily dechlorinated by zinc dust under more vigorous conditions.

J Rosevear

Papers

Use of substituted 2-(2'-hydroxyaryl)-2h-benzotriazolesulfonates as photostabilising agents for natural and synthetic fibres

The preparation and spectral properties of some monosubstituted 1,3,5,-Triphenyl-2-pyrazolines

Cyclization Reactions in Azole Chemistry: The Reaction of Some Azoles With o-Fluoroacetophenone, o-Fluorobenzaldehyde and o-Fluorobenzophenone

The preparation and spectroscopic properties of some di- and tri-substituted 1,3,5-triphenyl-2-pyrazolines and related 2-pyrazolines

The reduction of some o-nitrophenylazo dyes with glucose: a general synthesis of 2-Aryl-2H-benzotriazole 1-oxides