The Spectroscopic Characterization of Halogenated Pollutants through the Interplay between Theory and Experiment: Application to R1122

Andrea Pietropolli Charmet,Nicola Tasinato,Paolo Stoppa,Giorgia Ceselin

doi:10.3390/molecules27030748

Andrea Pietropolli Charmet, Nicola Tasinato + Show 2 more

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https://doi.org/10.3390/molecules27030748

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Abstract

In the last decade, halogenated ethenes have seen an increasing interest for different applications; in particular, in refrigeration, air-conditioning and heat pumping. At the same time, their adverse effects as atmospheric pollutants require environmental monitoring, especially by remote sensing spectroscopic techniques. For this purpose, an accurate characterization of the spectroscopic fingerprint—in particular, those of relevance for rotational–vibrational spectroscopy—of the target molecules is strongly needed. This work provides an integrated computational–theoretical investigation on R1122 (2-Chloro-1,1-difluoro-ethylene, ClHC=CF), a compound widely employed as a key intermediate in different chemical processes. State-of-the-art quantum chemical calculations relying on CCSD(T)-based composite schemes and hybrid CCSD(T)/DFT approaches are used to obtain an accurate prediction of the structural, rotational and vibrational spectroscopic properties. In addition, the equilibrium geometry is obtained by exploiting the semi-experimental method. The theoretical predictions are used to guide the analysis of the experimentally recorded gas-phase infrared spectrum, which is assigned in the 400–6500 cm region. Furthermore, absorption cross sections are accurately determined over the same spectral range. Finally, by using the obtained spectroscopic data, a first estimate of the global warming potential of R1122 vibrational spectra is obtained.

Highlights

Halogenated ethenes are the shortest members among the family of halogenated olefins, a class of organic compounds that has received growing attention from the scientific community, especially in the last decade
The equilibrium geometry has been derived by the semi-experimental approach, in which the ground-state rotational constants of a set of isotopologues have been corrected through vibrational contributions evaluated at the rev-DSDPBEP86/jun-ccpV(T+d)Z level and used to refine the structural parameters in a non-linear least-squares procedure
The equilibrium geometry has been theoretically derived by adopting different methods; in particular, CCSD(T)-based composite schemes, as well as density functional theory (DFT) computations relying on the rev-DSDPBEP86 or PW6B95 functionals corrected by the recently proposed Nano-LEGO platform

Summary

Introduction

Halogenated ethenes are the shortest members among the family of halogenated olefins, a class of organic compounds that has received growing attention from the scientific community, especially in the last decade. The recent advances in high-resolution infrared techniques make them very efficient in monitoring and detecting gaseous pollutants in real-time and with a very high sensitivity [11,12,13], provided that accurate spectroscopic data are available [14]. These data are obtained by the ro-vibrational and line-shape analysis of high-resolution spectra, which are often affected by several resonances [15]; ab initio calculations are nowadays able to yield accurate predictions for both anharmonic and Coriolis couplings, greatly assisting the whole process

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