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

Experimentally Calibrated Analysis of the Electronic Structure of CuO+: Implications for Reactivity

Contains fulltext : 200095.pdf (postprint version ) (Open Access

Transforming hemithioindigo from a two-way to a one-way molecular photoswitch by isolation in the gas phase

Hemithioindigo compounds are attractive two-way molecular photoswitches combining stilbene and thioindigo parts connected by a C–C double bond. In solution, these photoswitches have been well studied. This study presents the investigation of a hemithioindigo derivative in the gas phase. Visible absorption spectra, measured by standard (visPD) and helium-tagging visible photodissociation (He-visPD) techniques were used to unravel absorption characteristics at the level of isolated molecules at 3 Kelvin. Comparison between the Z and E isomers shows a quite distinctive behavior upon visible light absorption. The Z isomer readily undergoes Z → E conversion in the gas phase, as evidenced by the changes in the helium-tagging infrared photodissociation (He-IRPD) spectra. Surprisingly, visible light excitation of the E isomer does not lead to efficient E → Z isomerization unlike in solution. Instead, the ions relax back to their ground state. Influencing the microenvironment of the E isomer by complexation with the highly polar betaine zwitterion resulted in absorption changes, albeit without activating the photoswitching process. Hence, isolation in the gas phase transforms hemithioindigo into a one-way molecular photoswitch. Furthermore, the combination of He-visPD and IRPD spectroscopies proved to be an excellent method for studying photochemical processes such as the double-bond isomerization in the gas phase

Reactive cyclic intermediates in the ProTide prodrugs activation: trapping the elusive pentavalent phosphorane

Contains fulltext : 200158.pdf (publisher's version ) (Closed access

M-O Bonding Beyond the Oxo Wall: Spectroscopy and Reactivity of Cobalt(III)-Oxyl and Cobalt(III)-Oxo Complexes

Contains fulltext : 206092.pdf (publisher's version ) (Open Access

Trapping Iron(III)-Oxo Species at the Boundary of the "Oxo Wall": Insights into the Nature of the Fe(III)-O Bond

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N-Ammonium Ylide Mediators for Selective Electrochemical C–H Oxidation

The site-specific oxidation of strong C(sp3)-H bonds is of uncontested utility in organicsynthesis. From simplifying access to metabolites and late-stage diversification of lead compoundsto truncating retrosynthetic plans, there is a growing need for new reagents and methods forachieving such a transformation in both academic and industrial circles. One main drawback ofcurrent chemical reagents is the lack of diversity with regards to structure and reactivity thatprevent a combinatorial approach for rapid screening to be employed. In that regard, directedevolution still holds the greatest promise for achieving complex C–H oxidations in a variety ofcomplex settings. Herein we present a rationally designed platform that provides a step towardsthis challenge using N-ammonium ylides as electrochemically driven oxidants for site-specific,chemoselective C(sp3)–H oxidation. By taking a first-principles approach guided by computation,these new mediators were identified and rapidly expanded into a library using ubiquitous buildingblocks and trivial synthesis techniques. The ylide-based approach to C–H oxidation exhibitstunable selectivity that is often exclusive to this class of oxidants and can be applied to real worldproblems in the agricultural and pharmaceutical sectors.</p

Additional file 3: of Topological analysis of metabolic networks integrating co-segregating transcriptomes and metabolomes in type 2 diabetic rat congenic series

Supplementary Tables 4-6. (XLSX 28452 kb