COMPLEXES OF CRIEGEE INTERMEDIATE CH2OO WITH CO, CO2, H2O, SO2, NO2, CH3OH, HCOOH AND CH3CH3CO MOLECULES – A DFT STUDY ON BONDING, ENERGETICS AND SPECTRA

Abstract

Using high-level quantum chemical methods like CBS-QB3, CCSD(T), PBEPBE, the bonding and energy of the criegee intermediate (CI) CH2OO complexes, with atmospherically abundant gas molecules like H2O, CO, CO2, SO2, NO2, HCOOH, CH3OH and CH3CH3CO are studied. The interaction of CIs with these molecules results in hydrogen-bonded reaction complexes due to the zwitterionic character of CIs. Our findings indicate that CIs interact strongly with HCOOH, CH3OH, H2O and are weakly bonded to CO and CO2. The bonded complex of CIs with SO2 results in heteroozonide adduct. Energy decomposition analysis (EDA) reveals that the weakest interaction of CI with CO differs by 14 kcal/mol from that of the strongest criegee-HCOOH complex. EDA results augment well with the nature of bonding and charge transfer mechanism. Notably, exchange–correlation (XC) energy contributes maximum towards the interaction. Our IR analysis results suggest that CH2 and Osingle bondO stretching frequencies of CIs are red-shifted with large charge transfers where distinct CH2 symmetric modes increase the rate in hydrogen-bonded criegee reaction complexes. The electronic transitions in UV absorption spectra show that the excitation wavelengths of CIs complexes with the atmospheric molecules is red-shifted.