Core Shell Investigation of 2-nitroimidazole.

Paola Bolognesi,Luca Sementa,Bratislav P Marinkovic,Susanna Monti,Jacopo Chiarinelli,Lorenzo Avaldi,Robert Richter,Vincenzo Carravetta,Antonella Cartoni,Mattea C Castrovilli,Sanja Tosic,Preeti Manjari Mishra,Giovanni Barcaro

doi:10.3389/fchem.2019.00151

Abstract

Tunability and selectivity of synchrotron radiation have been used to study the excitation and ionization of 2-nitroimidazole at the C, N, and O K-edges. The combination of a set of different measurements (X-ray photoelectron spectroscopy, near-edge photoabsorption spectroscopy, Resonant Auger electron spectroscopy, and mass spectrometry) and computational modeling have successfully disclosed local effects due to the chemical environment on both excitation/ionization and fragmentation of the molecule.

Highlights

Inner shell electrons are localized on specific molecular sites, due to their “atomic-like” nature, and, because they are affected by the chemical environment, can provide details on specific molecular bonds
The goal of the present study is to explore the electronic structure of 2-nitroimidazole (2NIM) in the core excitation and ionization regions at the C, N, and O K edges by experiments and quantum mechanics calculations and to investigate the possible correlations between these core excited electronic states and the following molecular fragmentation
For the X-ray photoelectron spectra (XPS) and near-edge X-ray absorption fine spectra (NEXAFS) experiments, a qualitative approach, based on the spectroscopy of imidazole and nitrogen dioxide molecules, guided a first assignment of the different features of the spectra. This was fully validated by the HF, DFT, multiconfigurational self-consistent field (MCSCF), and TDDFT calculations: the discussion of the observed chemical shifts unravels the role played by the nitro group in the stabilization of the imidazole ring atoms

Summary

Introduction

Inner shell electrons are localized on specific molecular sites, due to their “atomic-like” nature, and, because they are affected by the chemical environment, can provide details on specific molecular bonds. The question that arises is whether the molecular fragmentation induced by inner shell processes is site-selective, i.e., affected by the “localization” of the core hole, as well as, in the case of photoabsorption, by the localization and character of the excited orbital. In some cases, (Ueda et al, 1999; Liu et al, 2005), an ultrafast molecular fragmentation takes place on a time scale comparable to the electronic decay time of the core hole. In such cases, the process being driven by the elongation of specific bonds adjacent to the core excited atom will be dominated by the formation of specific fragments “cut” around the atomic site

Objectives

Results

Conclusion