Modeling Reactive Scattering of F(2P) at a Liquid Squalane Interface: A Hybrid QM/MM Molecular Dynamics Study

Atomic and Molecular Collisions at Liquid Surfaces

The gas-liquid interface remains one of the least explored, but nevertheless most practically important, environments in which molecular collisions take place. These molecular-level processes underlie many bulk phenomena of fundamental and applied interest, spanning evaporation, respiration, multiphase catalysis, and atmospheric chemistry. We review here the research that has, during the past decade or so, been unraveling the molecular-level mechanisms of inelastic and reactive collisions at the gas-liquid interface. Armed with the knowledge that such collisions with the outer layers of the interfacial region can be unambiguously distinguished, we show that the scattering of gas-phase projectiles is a promising new tool for the interrogation of liquid surfaces with extreme surface sensitivity. Especially for reactive scattering, this method also offers absolute chemical selectivity for the groups that react to produce a specific observed product.

QM/MM investigations of organic chemistry oriented questions

About 35 years after its first suggestion, QM/MM became the standard theoretical approach to investigate enzymatic structures and processes. The success is due to the ability of QM/MM to provide an accurate atomistic picture of enzymes and related processes. This picture can even be turned into a movie if nuclei-dynamics is taken into account to describe enzymatic processes. In the field of organic chemistry, QM/MM methods are used to a much lesser extent although almost all relevant processes happen in condensed matter or are influenced by complicated interactions between substrate and catalyst. There is less importance for theoretical organic chemistry since the influence of nonpolar solvents is rather weak and the effect of polar solvents can often be accurately described by continuum approaches. Catalytic processes (homogeneous and heterogeneous) can often be reduced to truncated model systems, which are so small that pure quantum-mechanical approaches can be employed. However, since QM/MM becomes more and more efficient due to the success in software and hardware developments, it is more and more used in theoretical organic chemistry to study effects which result from the molecular nature of the environment. It is shown by many examples discussed in this review that the influence can be tremendous, even for nonpolar reactions. The importance of environmental effects in theoretical spectroscopy was already known. Due to its benefits, QM/MM can be expected to experience ongoing growth for the next decade.In the present chapter we give an overview of QM/MM developments and their importance in theoretical organic chemistry, and review applications which give impressions of the possibilities and the importance of the relevant effects. Since there is already a bunch of excellent reviews dealing with QM/MM, we will discuss fundamental ingredients and developments of QM/MM very briefly with a focus on very recent progress. For the applications we follow a similar strategy.