Propriedades eletrônicas e espectroscópicas de compostos bioativos amazonenses em meio atmosférico

Abstract

Hydrogen-bonded interactions of organic molecules are known to play crucial role in many chemical and biochemical processes that are essential to the maintenance of life. But they are important as well in various atmospheric processes like formation of secondary aerosol particles that may have adverse effects on public health and global climate. Atmospheric aerosol particle formation often begins with pre-nucleation processes, where hydrogen bonding between a few atmospheric precursor molecules plays a key role in stabilizing small molecular clusters. These interactions facilitate the transition to nucleation, eventually leading to the growth of larger aerosol particles. Recently, the role of organic acids in the process of new particle via nucleation is being investigated widely, both by experimental and theoretical procedures. The Amazon basin is an important source of aerosols and gases, which are transported to high levels in the atmosphere and may have potential impact on global climate conditions. Recent experimental measurements have found a considerable number of organic compounds in the natural constituents of Amazonian aerosol samples. In the present work, we employ quantum computational methods based on density functional theory (DFT) to explore the interaction of Malic acid and Vanillic acid with five different atmospheric bases - ammonia, methylamine, dimethylamine, trimethylamine and monoethanolamine - all recognized as important atmospheric nucleation precursors. Both Malic acid and Valine have been detected in natural organics aerosol emissions in Amazon basin and the acid-base interactions are believed to be lay a crucial role in stabilizing atmospheric molecular clusters. The presence of strong inter-molecular hydrogen bonds and large binding electronic energies indicate that these acids interact strongly with base molecules which is relevant in the context of pre-nucleation cluster formation. The Rayleigh scattering intensities of the clusters increase many-fold upon clustering with respect to the isolated acid molecules. Analyses of the binding free energy changes of clusters at different temperatures suggest that clustering becomes more favorable at temperatures below ambient air (298 K). A detailed and systematic examination of the structural, energetic, electrical, and spectroscopic properties of the binary complexes formed between malic acid and vanillic acid with atmospheric bases reveals that these complexes could play a role in atmospheric pre-nucleation and nucleation processes, provided they are present in sufficient concentrations.