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Optical physic

Fotoaktivovatelné sloučeniny

The work presents three projects focused on the syntheses of photoactivatable compounds and studying of their photochemical behaviour. The first project introduces a novel concept - a photoremovable chiral auxiliary. The benzoin photoremovable protecting group has been used as a chiral auxiliary inducing enantioselectivity in the Diels-Alder reaction of cyclopentadiene and protected acrylate. The conditions and the structure of the chromophore have been optimized to display up to 96% enantiomeric excess of the created norbornenate. The subsequent removal of the auxiliary was accomplished by irradiation by UV light - as traceless reagent with a high chemical yield (>85%). The second project summarizes attempts of the synthesis of flavin derivative. The structure of phenanthroline-flavin has been proposed to be able of catalyzing of both oxidative and reductive reactions. Three different multistep synthetic pathways have been investigated and several new uracil and phenanthroline derivatives have been synthetized and fully characterized. However, the last step in all pathways, the condensation of substituted uracil with phenanthroline derivative, was unsuccessful. In the final project, the synthesis of (6-hydroxy-3-oxo-3H-xanthen-9-yl)methyl diethyl phosphate complex with...Práce zahrnuje tři projekty zaměřené na syntézu fotoaktivovatelných molekul a studium jejich fotoreaktivity. První projekt představuje nový koncept - fotoodstupitelnou chirální pomocnou látku. Benzoinová fotoodstupitelná chránicí skupina byla použita jako chirální pomocná látka indukující enantioselektivitu v Dielsově-Alderově reakci cyklopentadienu a chráněného akrylátu. Byly optimalizovány reakční podmínky a struktura chromoforu při dosažení až 96 % enantiomerního nadbytku vzniklého norbornenátu. Následné odstranění pomocné látky bylo provedeno pomocí ozáření UV světlem, bezestopým reagentem, ve vysokém chemickém výtěžku (>85 %). Druhý projekt obsahuje pokusy o syntézu derivátu flavinu. Struktura fenantrolin-flavinu byla navržena tak, aby byla schopna fotokatalyzovat jak oxidace, tak redukce. Byly zkoumány tři různé vícekrokové reakční cesty vedoucí k jeho přípravě a bylo připraveno a plně charakterizováno několik nových uracilových a fenantrolinových derivátů. Poslední krok všech reakčních cest, kondenzace substituovaného uracilu s fenantrolinovým derivátem, byl neúspěšný. V posledním projektu je prezentována syntéza komplexu (6-hydroxy-3-oxo-3H-xanthen-9- yl)methyl diethyl fosfátu s 2,3-dichlor-5,6-dikyano-1,4-benzochinonem a jeho fotoproduktu 6-hydroxy-3-oxo-3H-xanthen-9-karboxylové kyseliny....Department of Organic ChemistryKatedra organické chemieFaculty of SciencePřírodovědecká fakult

Visible-to-NIR-Light Activated Release: From Small Molecules to Nanomaterials

Photoactivatable (alternatively, photoremovable, photoreleasable, or photocleavable) protecting groups (PPGs), also known as caged or photocaged compounds, are used to enable non-invasive spatiotemporal photochemical control over the release of species of interest. Recent years have seen the development of PPGs activatable by biologically and chemically benign visible and near-infrared (NIR) light. These long-wavelength-absorbing moieties expand the applicability of this powerful method and its accessibility to non-specialist users. This review comprehensively covers organic and transition metal-containing photoactivatable compounds (complexes) that absorb in the visible- and NIR-range to release various leaving groups and gasotransmitters (carbon monoxide, nitric oxide, and hydrogen sulfide). The text also covers visible- and NIR-light-induced photosensitized release using molecular sensitizers, quantum dots, and upconversion and second-harmonic nanoparticles, as well as release via photodynamic (photooxygenation by singlet oxygen) and photothermal effects. Release from photo-activatable polymers, micelles, vesicles, and photoswitches, along with the related emerging field of photopharmacology, is discussed at the end of the review

Photochemistry of a 9-Dithianyl-Pyronin Derivative: A Cornucopia of Reaction Intermediates Lead to Common Photoproducts

Leaving groups attached to themeso-methyl position of many common dyes, such as xanthene, BODIPY, or pyronin derivatives, can be liberated upon irradiation with visible light. However, the course of phototransformations of such photoactivatable systems can be quite complex and the identification of reaction intermediates or even products is often neglected. This paper exemplifies the photochemistry of a 9-dithianyl-pyronin derivative, which undergoes an oxidative transformation at themeso-position to give a 3,6-diamino-9H-xanthen-9-one derivative, formic acid, and carbon monoxide as the main photoproducts. The course of this multi-photon multi-step reaction was studied under various conditions by steady-state and time-resolved optical spectroscopy, mass spectrometry and NMR spectroscopy to understand the effects of solvents and molecular oxygen on individual steps. Our analyses have revealed the existence of many intermediates and their interrelationships to provide a complete picture of the transformation, which can bring new inputs to a rational design of new photoactivatable pyronin or xanthene derivatives

Electron-Poor Acridones and Acridiniums as Super Photooxidants in Molecular Photoelectrochemistry by Unusual Mechanisms

Electron-deficient acridones and in situ generated acridinium salts are reported potent, closed-shell photooxidants that undergo surprising mechanisms. When bridging acyclic triarylamine catalysts with a carbonyl group (acridones), this completely diverts their behavior away from open-shell, radical cationic, 'beyond diffusion' photocatalysis to closed-shell, neutral, diffusion-controlled photocatalysis. Brønsted acid activation of acridones dramatically increases excited state oxidation power (by +0.8 V). Upon reduction of protonated acridones, they transform to electron-deficient acridinium salts as even more potent photooxidants (*E1/2 = +2.56-3.05 V vs SCE). These oxidize even electron-deficient arenes where conventional acridinium salt photooxidants have thusfar been limited to electron-rich arenes. Surprisingly, upon photoexcitation these electron-deficient acridinium salts appear to undergo two electron reductive quenching to form spectroscopically-detected acridinide anions. This new behaviour is partly enabled by a substrate assembly with the arene, and contrasts to conventional SET reductive quenching of acridinium salts. Critically, this study illustrates how redox active chromophoric molecules initially considered photocatalysts can transform during the reaction to catalytically active species with completely different redox and spectroscopic properties

Caffeine strongly improves motility parameters of turkey spermatozoa with no effect on cell viability

The purpose of this study was to evaluate the impact of caffeine on turkey spermatozoa during in vitro incubation. Experimental samples were prepared by diluting the raw semen with nine different concentrations of caffeine – from 0.078125 mg/mL to 10 mg/mL. The individual motility parameters were evaluated by the Computer Assisted Semen Analyser (CASA) system, and the viability of spermatozoa was evaluated using eosin-nigrosin staining. Selected parameters were recorded at six time periods: 0, 1, 2, 3, 4 and 5 h at 5 °C and 41 °C. A significantly higher motility and progressive motility of spermatozoa (P < 0.01 and P < 0.001, respectively) was detected in the samples containing caffeine ranging from 0.15625 to 7.5 mg/mL as compared to the control sample at 5 °C. At an incubation temperature of 41 °C the positive effect of caffeine on motility parameters was observed only at the beginning of incubation (at times 0 and 1). The tested caffeine concentrations showed no significant effect on the viability of turkey spermatozoa at any time period of incubation. A higher percentage of dead spermatozoa was observed for incubation at 41 °C (from 5.96% to 11.1%) in comparison to 5 °C (from 1.62% to 5.79%). The results suggest that caffeine can be used as a suitable component of turkey semen extenders and has the potential to improve fertility

Innovative bidirectional isolated high-power density on-board charge for vehicle-to-grid

This paper deals with developing and implementing a bidirectional galvanically isolated on-board charger of a high-power density. The power density of the new charger was 4 kW/kg and 2.46 kW/dm(3), and the maximum efficiency was 96.4% at 3.4 kW. Due to the requirement to achieve a high-power density, a single-stage inverter topology was used. Regarding switching losses, due to the topology of the circuit with so-called hard switching, the switching frequency was set to 150 kHz. A laboratory prototype was built to verify the properties and operating principles of the described charger topology. The on-board charger has been tested in a microgrid test platform. Due to the parasitic properties of the transformer and other electronic components, overvoltage with subsequent oscillations occurred on the primary side of the transformer and damped resonance on its secondary side. These parasitic properties caused interference and especially voltage stress on the semiconductor elements. These undesirable phenomena have been eliminated by adding an active element to the charger topology and a new transistor control strategy. This new switching control strategy of transistors has been patented.Web of Science2221art. no. 847

Photoactivatable Compounds

The work presents three projects focused on the syntheses of photoactivatable compounds and studying of their photochemical behaviour. The first project introduces a novel concept - a photoremovable chiral auxiliary. The benzoin photoremovable protecting group has been used as a chiral auxiliary inducing enantioselectivity in the Diels-Alder reaction of cyclopentadiene and protected acrylate. The conditions and the structure of the chromophore have been optimized to display up to 96% enantiomeric excess of the created norbornenate. The subsequent removal of the auxiliary was accomplished by irradiation by UV light - as traceless reagent with a high chemical yield (>85%). The second project summarizes attempts of the synthesis of flavin derivative. The structure of phenanthroline-flavin has been proposed to be able of catalyzing of both oxidative and reductive reactions. Three different multistep synthetic pathways have been investigated and several new uracil and phenanthroline derivatives have been synthetized and fully characterized. However, the last step in all pathways, the condensation of substituted uracil with phenanthroline derivative, was unsuccessful. In the final project, the synthesis of (6-hydroxy-3-oxo-3H-xanthen-9-yl)methyl diethyl phosphate complex with..

Analýza finanční výkonnosti společnosti Coca-Cola Beverages Česká republika

Práce analyzuje finanční výkonnost společnosti Coca-Cola Beverages Česká republika z pohledu externího analytika. Pro hodnocení jsou použity všechny vhodné metody finanční analýzy, tj. rozbor absolutních ukazatelů, analýza poměrovými ukazately a aplikace ukazatele ekonomické přidané hodnoty (EVA). Dále je finanční situace podniku porovnána s jeho největšími konkurenty na trhu (General Bottlers a Kofola)