Picosecond to millisecond tracking of a photocatalytic decarboxylation reaction provides direct mechanistic insights

Abstract

The photochemical decarboxylation of carboxylic acids is a versatile route to free radical intermediates for chemical synthesis. However, the sequential nature of this multi-step reaction renders the mechanism challenging to probe. Here, we employ a 100 kHz mid-infrared probe in a transient absorption spectroscopy experiment to track the decarboxylation of cyclohexanecarboxylic acid in acetonitrile-d3 over picosecond to millisecond timescales using a photooxidant pair (phenanthrene and 1,4-dicyanobenzene). Selective excitation of phenanthrene at 256 nm enables a diffusion-limited photoinduced electron transfer to 1,4-dicyanobenzene. A measured time offset in the rise of the CO2 byproduct reports on the lifetime (520 ± 120 ns) of a reactive carboxyl radical in solution, and spectroscopic observation of the carboxyl radical confirm its formation as a reaction intermediate. Precise clocking of the lifetimes of radicals generated in situ by an activated C-C bond fission will pave the way for improving the photocatalytic selectivity and turnover.

Transcriptional signatures in prefrontal cortex confer vulnerability versus resilience to food and cocaine addiction-like behavior

“…In the present study, we focused on the dataset of cocaine self-administration mice during the maintenance phase to study the impact of long-term exposure to cocaine on transcriptional changes at cell type specific levels. First, we determined the different cell subtypes stated in Bhattacherjee et al 14 using tSNE approach and replicated this (Fig. 3 a).…”

“…Finally, we investigated the cell type selective expression of the shared genes using the publicly available single-cell RNA-seq data of the PFC (including anterior cingular, prelimbic, and infralimbic cortex) in adult male C57BL/6 mice 14 . In the present study, we focused on the dataset of cocaine self-administration mice during the maintenance phase to study the impact of long-term exposure to cocaine on transcriptional changes at cell type specific levels.…”

“…( a ) t-SNE plot representing different cell type clusters in PFC. t-SNE plot representing the clusters of the different cell subtypes in PFC based on the transcriptome of cocaine self-administration mice during the habituation phase from Bhattacherjee et al 14 . ( b ) t-SNE plot representing some of the common upregulated genes found in cocaine and food addiction studies.…”

“…Protein–protein association analysis identified a hub network of several shared genes at the protein level. Using single-cell RNA-seq data from a publicly available study 14 , we could allocate the shared molecular players in a cell-type-specific manner.…”

Mapping the multi-step mechanism of a photoredox catalyzed atom-transfer radical polymerization reaction by direct observation of the reactive intermediates

“…In this way, reaction pathways may be observed on timescales from hundreds of femtoseconds up to tens of milliseconds. [29][30][31] The resulting advantage is dynamic real-time tracking of short-and longer-lived intermediates, typically spanning picosecond to microsecond lifetimes, allowing iden-tication and kinetic analyses for species impossible to observe with steady state techniques.…”