Ring formation and hydration effects in electron attachment to misonidazole

This research was funded by CZECH SCIENCE FOUNDATION grant number 19-01159S; Czech Ministry of Education Youth and Sports via OP RDE Grant no. CZ.02.2.69/0.0/16_027/0008355; S.D. acknowledges funding from the FWF, Vienna (P30332).We study the reactivity of misonidazole with low-energy electrons in a water environment combining experiment and theoretical modelling. The environment is modelled by sequential hydration of misonidazole clusters in vacuum. The well-defined experimental conditions enable computational modeling of the observed reactions. While the NO- 2 dissociative electron attachment channel is suppressed, as also observed previously for other molecules, the OH- channel remains open. Such behavior is enabled by the high hydration energy of OH- and ring formation in the neutral radical co-fragment. These observations help to understand the mechanism of bio-reductive drug action. Electron-induced formation of covalent bonds is then important not only for biological processes but may find applications also in technology.publishersversionpublishe

Fotochemie v klastrech a nanočásticích: systémy relevantní v atmosférické chemii a v biologii

Influence of solvation on photodissociation of molecules is investigated in clusters produced in a molecular beam experiment. Photochemistry in three different systems is compared: (i) HBrArn and (HBr)n clusters, where the fragment does not react with the solvent and an effect of the fragment caging is observed, (ii) HBr(H2O)n system where chemical reaction occurs and a reaction channel is closed by the electronic interaction with the solvent. The practical relevance of the studied processes ranges from atmospheric chemistry to biology

Nanoparticles in molecular and laser beams

The subject matter about this work is: From engeneering chemistry to nanotechnology

Atmospheric processes on ice nanoparticles in molecular beams

This review summarizes some recent experiments with ice nanoparticles (large water clusters) in molecular beams and outlines their atmospheric relevance: (1) Investigation of mixed water–nitric acid particles by means of the electron ionization and sodium doping combined with photoionization revealed the prominent role of HNO3 molecule as the condensation nuclei. (2) The uptake of atmospheric molecules by water ice nanoparticles has been studied, and the pickup cross sections for some molecules exceed significantly the geometrical sizes of the ice nanoparticles. (3) Photodissociation of hydrogen halides on water ice particles has been shown to proceed via excitation of acidically dissociated ion pair and subsequent biradical generation and H3O dissociation. The photodissociation of CF2Cl2 molecule in clusters is also mentioned. Possible atmospheric consequences of all these results are briefly discussed

Sodium doping and reactivity in pure and mixed ice nanoparticles

Doping of clusters by sodium atoms and subsequent photoionization (NaPI) is used as a fragmentation-free cluster ionization method. Here we investigate different clusters using NaPI and electron ionization (EI) with a reflectron time-of-flight mass spectrometer (RTOF). The mass spectra of the same clusters ionized by NaPI and EI reveal significant differences which point to Na reactivity in the clusters. First, we discuss mixed XM·(H2O)N (X = HNO3, N2O) clusters where reactions between Na and molecules X leads to the “cluster invisibility” for the NaPI method. Second, mixed (NH3)M·(H2O)N clusters are observed by both methods, but they reveal different cluster compositions, and the mass spectra suggest that neither the EI nor the NaPI spectrum corresponds exactly to the neutral cluster distribution. Finally, we discuss the reactions of Na in pure water clusters as a function of the number of Na atoms doped into the clusters. In summary, we present experimental evidence that the NaPI method in the present cases does not reveal the size and composition of the neutral clusters. A detailed understanding of Na reactivity in the clusters is needed for its application as a fragmentation-free cluster ionization method. Besides, we introduce the combination of NaPI and EI as a new tool to investigate the sodium reactivity in clusters and aerosol particles

Effect of cluster environment on the electron attachment to 2-nitrophenol

Effect of cluster environment on the electron attachment to 2-nitrophenol (2NP) is studied in homogeneous 2NP clusters and heterogeneous clusters of 2NP, argon and water. The cluster environment significantly reduces fragmentation of 2NP after electron attachment. Parent cluster anions 2NPn- are primary reaction products in both, homogeneous and heterogeneous clusters. Non-dissociative electron attachment to homogeneous clusters proceeds at low energies <2 eV, presumably via dipole-supported states. In heterogeneous clusters, the interaction with low energy (<2 eV) electrons is shielded by the solvent. Surprisingly, the energetic threshold for the electron attachment rises with the number (n) of 2NP molecules in the cluster (2NP)n-. This rise can be either due to a strong change of the 2NP conformation induced by the cluster environment or due to the the competition with electron autodetachment after proton transfer that has been first observed by Allan in the formic acid dimer [M. Allan, Phys. Rev. Lett. 98, 123201 (2007)]. We observe the same threshold rise for complex Arm·(2NP)n- and H2O·(2NP)n- anions. This indicates that the electron attachment to 2-nitrophenol in cluster environment is more influenced by the solute − solute interaction compared to the solute − solvent interaction

Proton transfer from pinene stabilizes water clusters

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