A5088869993- Metal-Catalyzed Oxygenation Mechanisms
- Oxidative Organic Chemistry Reactions
- Porphyrin and Phthalocyanine Chemistry
- Metal complexes synthesis and properties
- Radical Photochemical Reactions
- Metalloenzymes and iron-sulfur proteins
- Hemoglobin structure and function
- Mass Spectrometry Techniques and Applications
- Catalytic C–H Functionalization Methods
- Photochemistry and Electron Transfer Studies
- Synthesis and Catalytic Reactions
- Heme Oxygenase-1 and Carbon Monoxide
- Organophosphorus compounds synthesis
- Lanthanide and Transition Metal Complexes
- Chemical Reactions and Mechanisms
- Advanced Chemical Physics Studies
- Metal and Thin Film Mechanics
- Catalytic Processes in Materials Science
- Semiconductor materials and devices
- Spectroscopy and Quantum Chemical Studies
- Photosynthetic Processes and Mechanisms
- bioluminescence and chemiluminescence research
- Pharmacological Effects and Assays
- Diamond and Carbon-based Materials Research
- Luminescence and Fluorescent Materials
Charles University
2015-2023
Scripps Research Institute
2021
University of Chemistry and Technology, Prague
2014-2016
The site-specific oxidation of strong C(sp3)-H bonds is uncontested utility in organic synthesis. From simplifying access to metabolites and late-stage diversification lead compounds truncating retrosynthetic plans, there a growing need for new reagents methods achieving such transformation both academic industrial circles. One main drawback current chemical the lack diversity with regard structure reactivity that prevents combinatorial approach rapid screening be employed. In regard,...
In biology, high valent oxo–iron(IV) species have been shown to be pivotal intermediates for functionalization of C–H bonds in the catalytic cycles a range O2-activating iron enzymes. This work details an electronic-structure investigation [FeIV(O)(LNHC)(NCMe)]2+ (LNHC = 3,9,14,20-tetraaza-1,6,12,17-tetraazoniapenta-cyclohexacosane-1(23),4,6(26),10,12(25),15,17(24),21-octaene, complex 1) using helium tagging infrared photodissociation (IRPD), absorption, and magnetic circular dichroism (MCD)...
We demonstrate the application of infrared photodissocation spectroscopy for determination Fe═O stretching frequencies high-valent iron(IV)-oxo complexes [(L)Fe(O)(X)]2+/+ (L = TMC, N4Py, PyTACN, and X CH3CN, CF3SO3, ClO4, CF3COO, NO3, N3). show that values determined by resonance Raman in acetonitrile solutions are on average 9 cm-1 red-shifted with respect to unbiased gas-phase values. Furthermore, we assignment spin state based vibrational modes a coordinated anion compare reactivities...
Abstract Fe V (O)(OH) species have long been proposed to play a key role in wide range of biomimetic and enzymatic oxidations, including as intermediates arene dihydroxylation catalyzed by Rieske oxygenases. However, the inability accumulate these solution has thus far prevented their spectroscopic chemical characterization. Thus, we use gas-phase ion spectroscopy reactivity analysis characterize highly reactive [Fe (O)(OH)( 5tips3 tpa)] 2+ ( 3 ) complex. The results show that hydroxylates...
Terminal non-heme iron(IV)–oxo compounds are among the most powerful and best studied oxidants of strong C–H bonds. In contrast to increasing number such complexes (>80 thus far), corresponding one-electron-reduced derivatives much rarer presumably less stable, only two iron(III)–oxo have been characterized date, both which stabilized by hydrogen-bonding interactions. Herein we employed gas-phase techniques generate identify a series terminal complexes, all without built-in hydrogen bonding....
Abstract The CuO + core is a central motif of reactive intermediates in copper‐catalysed oxidations occurring nature. high reactivity stems from weak bonding between the atoms, which cannot be described by simple classical model. To obtain correct picture, we have investigated acetonitrile‐ligated ion using neon‐tagging photodissociation spectroscopy at 5 K. spectra feature complex vibronic absorption progressions NIR and visible regions. Employing Franck–Condon analyses, derived low‐lying...
Abstract We report for the first time infrared spectra of three non‐heme pseudo‐octahedral iron(V) nitride complexes with assigned Fe−N stretching vibrations. The intensities bands in two are extremely weak. Their detection was enabled by high resolution and sensitivity experiments performed at 3 K isolated gas phase. Multireference CASPT2 calculations revealed that bond ground doublet state is influenced low‐lying excited states. In particular, configuration interaction between second leads...
A combination of NMR and IRPD spectroscopy confirmed the existence predicted cyclic phosphorus intermediates involved in ProTide prodrugs activation.
Helium-tagging predissociation spectroscopy in the visible spectral range (He@VisPD) is shown for Rhodamine 123, 110, and 110's silver salt (silver carboxylate). It that spectra reflect single-photon absorption. The helium-tagged ions are ground vibrational state, He@VisPD feature Franck-Condon envelopes excitation to first excited singlet state agree very well with theoretical simulations. S0 → S1 energies 2.712 ± 0.006 eV 2.700 2.751 of 110. determined can be slightly blue-shifted due...
Abstract Terminal oxo complexes of late transition metals are frequently proposed reactive intermediates. However, they scarcely known beyond Group 8. Using mass spectrometry, we prepared and characterized two such complexes: [(N4Py)Co III (O)] + ( 1 ) IV 2+ 2 ). Infrared photodissociation spectroscopy revealed that the Co−O bond in is rather strong, accordance with its lack chemical reactivity. On contrary, has a very weak by stretching frequency ≤659 cm −1 . Accordingly, can abstract...
The nominal temperature range of cryogenic radio-frequency ion traps has recently been extended down to T=2.3 K. Whereas in situ He tagging mass-selected ions embedded dense helium buffer gas is becoming common for recording IR spectra through photofragmentation small and large ions, much less activity devoted the field cold chemistry, which this contribution means two orders magnitude extending from 300 below 3 importance understanding dynamics bi- termolecular reactions illustrated with...
Abstract The generation of iron(V) nitride complexes, which are targets biomimetic chemistry, is reported. Temperature‐dependent ion spectroscopy shows that this reaction governed by the spin‐state population their iron(III) azide precursors and can be tuned temperature. complex [(MePy 2 TACN)Fe(N 3 )] 2+ (MePy TACN= N ‐methyl‐ , ‐bis(2‐picolyl)‐1,4,7‐triazacyclononane) exists as a mixture sextet doublet spin states at 300 K, whereas only state populated K. Photofragmentation leads to...
Multimetallic Pd/Ni and dual-ligand Pd catalysis enable C(sp 2 )–P cross-coupling reactions in aqueous micelles under mild conditions using inexpensive commercial materials catalysts while avoiding environmentally unsustainable organic solvents.
3-Halo-3-phenyl-3H-diazirines (halogen = Br or Cl) undergo a dissociative single-electron transfer from alkyllithiums (RLi) in THF-based solvent mixtures. The resulting 3-phenyldiazirinyl radical, observed by EPR spectroscopy, is eventually transformed to benzonitrile. In Et2O, 2 equiv of RLi add both nitrogens halodiazirine N═N bond, affording N,N'-dialkylbenzamidines. nitrenoid reactivity some N-alkyl-1H-diazirine intermediates manifested their insertion into the α-C-H bond THF Et2O.
Fluorescein, eosin Y, and rose bengal are dyes used in clinical medicine considered (photo-)chemically stable. Upon extensive irradiation with visible light aqueous solutions, we found that these compounds release carbon monoxide (CO) - a bioactive gasotransmitter 40-100% yields along the production of low-mass secondary photoproducts, such as phthalic formic acids, multistep degradation process. Such photochemistry should be applications dyes, they could also utilized visible-light...
Abstract The CuO + core is a central motif of reactive intermediates in copper‐catalysed oxidations occurring nature. high reactivity stems from weak bonding between the atoms, which cannot be described by simple classical model. To obtain correct picture, we have investigated acetonitrile‐ligated ion using neon‐tagging photodissociation spectroscopy at 5 K. spectra feature complex vibronic absorption progressions NIR and visible regions. Employing Franck–Condon analyses, derived low‐lying...
Diazirinylidene (c-CN2) is formally the simplest of N-heterocyclic carbenes. The intermediacy this elusive species in fragmentation butyl 3-bromodiazirine-3-carboxylate (1a) with pent-4-en-1-ols and their sodium alkoxides DMF supported by formation 2-oxabicyclo[4.1.0]heptanes dipentenoxymethanes. These products result from an intramolecular [2 + 1] cycloaddition O-H insertion, respectively, pentenoxymethylenes suggested to originate reaction electrophilic c-CN2 alkoxide ion. 1a primary or...
Photoswitching of a permanently charged hemithioindigo switch was probed by two photon experiments in the gas phase at 3 K.
Abstract The generation of iron(V) nitride complexes, which are targets biomimetic chemistry, is reported. Temperature‐dependent ion spectroscopy shows that this reaction governed by the spin‐state population their iron(III) azide precursors and can be tuned temperature. complex [(MePy 2 TACN)Fe(N 3 )] 2+ (MePy TACN= N ‐methyl‐ , ‐bis(2‐picolyl)‐1,4,7‐triazacyclononane) exists as a mixture sextet doublet spin states at 300 K, whereas only state populated K. Photofragmentation leads to...
Abstract Leaving groups attached to the meso ‐methyl position of many common dyes, such as xanthene, BODIPY, or pyronin derivatives, can be liberated upon irradiation with visible light. However, course phototransformations photoactivatable systems quite complex and identification reaction intermediates even products is often neglected. This paper exemplifies photochemistry a 9‐dithianyl‐pyronin derivative, which undergoes an oxidative transformation at ‐position give 3,6‐diamino‐9 H...
Xanthene derivatives are organic dyes, some of which routinely used in different chemical and biological applications, including human medicine. In this work, we investigated the photochemistry most common ones, fluorescein, eosin Y, rose bengal, major products their photodegradation using optical spectroscopy, NMR, chromatography mass spectroscopy techniques. These substances, usually considered (photo)chemically stable, were found to liberate carbon monoxide (CO) 40–80% yields upon...