Photochemical Deracemization of Aza-1-isoindolinones: Critical Influence of Catalyst Substitution and the Nature of Its Resting State

The photochemical deracemization of aza-1-isoindolinones has been investigated. A chiral para-methoxy-substituted phenyl ketone was discovered that promotes the conversion of racemic 4-aza-1-isoindoli...

doi.org

Neue Fakten im "Schrödinger-Skandal" vom 13.11.

Seit vier Jahren stehen sexuelle Mißbrauchsvorwürfe gegen Erwin Schrödinger, den österreichischen Physiknobelpreisträger von 1933, im medialen Raum. Sie basieren auf einer Biografie, die fast 40 Jahre...

oe1.orf.at

Is Digital Drying an Effective Method for Infrared Spectroscopy of Gaseous Biofluid?

In recent years, gaseous biofluid analysis has gained popularity as a diagnostic approach due to the noninvasive collection of gaseous bioprobes. Among many biofluids, human exhaled breath stands out ...

pubs.acs.org

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links.springernature.com

Broadband shot-to-shot transient absorption anisotropy

Transient absorption (TA) is the most widespread method to follow ultrafast dynamics in molecules and materials. The related method of TA anisotropy (TAA) repor

pubs.aip.org

Fluorescence-Detected Pump–Probe Spectroscopy for Artifact-Free Detection of Stokes Shift Dynamics

Fluorescence-detected pump–probe (F-PP) spectroscopy is a recently developed method to study excited-state dynamics. F-PP combines the temporal resolution of conventional transient absorption (TA) spe...

pubs.acs.org

Oxetane Cleavage Pathways in the Excited State: Photochemical Kinetic Resolution as an Approach to Enantiopure Oxetanes

Chiral spirocyclic oxetanes [2-oxo-spiro(3H-indole-3,2′-oxetanes)] were subjected to irradiation in the presence of a chiral thioxanthone catalyst (5 mol %) at λ = 398 nm. An efficient kinetic resolution was observed, which led to an enrichment of one oxetane enantiomer as the major enantiomer (15 examples, 37−50% yield, 93−99% ee). The minor enantiomer underwent decomposition, and the decomposition products were carefully analyzed. They arise from a photocycloreversion (retro-Paternò–Büchi reaction) into a carbonyl component and an olefin. The cycloreversion offers two cleavage pathways depending on whether a C−O bond scission or a C−C bond scission occurs at the spirocyclic carbon atom. The course of this reaction was elucidated by a suite of mechanistic, spectroscopic, and quantum chemical methods. In the absence of a catalyst, cleavage occurs exclusively by initial C−O bond scission, leading to formaldehyde and a tetrasubstituted olefin as cleavage products. Time-resolved spectroscopy on the femtosecond/picosecond time scale, synthetic experiments, and calculations suggest the reaction to occur from the first excited singlet state (S1). In the presence of a sensitizer, triplet states are populated, and the first excited triplet state (T1) is responsible for cleavage into an isatin and a 1,1-diarylethene by an initial C−C bond scission. The kinetic resolution is explained by the chiral catalyst recruiting predominantly one enantiomer of the spirocyclic oxindole. A two-point hydrogen-bonding interaction is responsible for the recognition of this enantiomer, as corroborated by NMR titration studies and quantum chemical calculations. Transient absorption studies on the nanosecond/microsecond time scale allowed for observing the quenching of the catalyst triplet by either one of the two oxetane enantiomers with a slight preference for the minor enantiomer. In a competing situation with both enantiomers present, energy transfer to the major enantiomer is suppressed initially by the better-binding minor enantiomer and─as the reaction progresses─by oxindole fragmentation products blocking the binding site of the catalyst.

pubs.acs.org

Photoredox capacity expanded by the Cu site of CuFe-Mabiq

The monometallic Fe-Mabiq and bimetallic CuFe-Mabiq photoredox catalysts feature similar optical spectra and short excited-state lifetimes. Nevertheless, they exhibit markedly different photochemistry...

pubs.rsc.org

2025 MRS Spring Meeting & Exhibit

The 2025 MRS Spring Meeting is the key forum to present research to an interdisciplinary and international audience.

mrs.org

Quantenphysik im Blattgrün

Die Photosynthese – ein grundlegender Prozess für das Leben auf der Erde – birgt noch immer viele Geheimnisse. Ein Forscherteam um Prof. Jürgen Hauer an der TU München hat nun ein faszinierendes Detai...

photonworld.de

Women are credited less in science than men - Nature

The difference between the number of men and women listed as authors on scientific papers and inventors on patents is at least partly attributable to unacknowledged contributions by women scientists.

nature.com

Measurement of Bacterial Headspaces by FT-IR Spectroscopy Reveals Distinct Volatile Organic Compound Signatures

Ensuring prompt and precise identification of bacterial pathogens is essential for initiating appropriate antibiotic therapy and combating severe bacterial infections effectively. Traditional microbiological diagnostics, involving initial culturing and subsequent pathogen detection, are often laborious and time-consuming. Even though modern techniques such as Raman spectroscopy, MALDI-TOF, and 16S rRNA PCR have significantly expedited this process, new methods are required for the accurate and fast detection of bacterial pathogens. In this context, using bacterial metabolites for detection is promising as a future diagnostic approach. Fourier-transform infrared spectroscopy was employed in our study to analyze the biochemical composition of gas phases of bacterial isolates. We can characterize individual bacterial strains and identify specific bacteria within mixtures by utilizing volatile-metabolite-based infrared detection techniques. This approach enables rapid identification by discerning distinctive spectral features and intensities for different bacteria, offering new perspectives for bacterial pathogen diagnostics. This technique holds innovative potential to accelerate progress in the field, providing a faster and potentially more precise alternative to conventional diagnostic methods.

doi.org