Formation of Eigen or Zundel Features at Protonated Water Cluster–Aromatic Interfaces

Abstract

Interfacial interactions of protonated water clusters adsorbed at aromatic surfaces play an important role in biology, and in atmospheric, chemical and materials sciences. Here, we investigate the interaction of protonated water clusters ((H+H2O)n (where n=1–3)) with benzene (Bz), coronene (Cor) and dodecabenzocoronene (Dbc)). To study the structure, stability and spectral features of these complexes, computations are done using DFT‐PBE0(+D3) and SAPT0 methods. These interactions are probed by AIM electron density topography and non‐covalent interactions index (NCI) analyses. We suggest that the excess proton plays a crucial role in the stability of these model interfaces through strong inductive effects and the formation of Eigen or Zundel features. Also, computations reveal that the extension of the π‐aromatic system and the increase of the number of water molecules in the H‐bounded water network led to a strengthening of the interactions between the corresponding aromatic compound and protonated water molecules, except when a Zundel ion is formed. The present findings may serve to understand in‐depth the role of proton localized at aqueous medium interacting with large aromatic surfaces such as graphene interacting with acidic liquid water. Besides, we give the IR and UV‐Vis spectra of these complexes, which may help for their identification in laboratory.

Microhydration of small protonated polyaromatic hydrocarbons: a first principles study

“…Besides, this spectroscopy can be used to identify the excess proton localized in either the carbon surface or water clusters after comparison of the present spectra to those predicted recently for Bz–H + W n , Cor–H + W n and Dbc–H + W n ( n = 1–3) clusters. 66 Indeed, the presently computed UV-vis band wavelengths are significantly lower than those when the excess proton is localized at the water clusters.…”

“…For all species, we carry out computations at the PBE0/6-311++G** and PBE0-D3/6-311++G** levels, where D3 corresponds to the Grimme's dispersion correction to account for dispersion. 68 As established in the literature, 66,69 the PBE0-D3/6-311++G** level of theory is accurate enough to describe such protonated aromatic–water clusters since benchmarks revealed that PBE0-D3/6-311++G** competes with MP2/CBS and CCSD(T)/CBS, whereas a strong reduction in computational costs is noticed. In particular, we carried out additional MP2/6-311++G** calculations for BzH + –W n ( n = 1–3) clusters.…”

“…In contrast, the proton transfer process enhances the H-bonding strength as well as shortens the water–water interactions in protonated water PAH clusters. 66…”

“…In particular, they can help to disentangle the IR spectra of protonated aromatics interacting with water clusters and those of aromatics interacting with protonated water clusters in a mixture using the presently computed IR spectra and those of Bz–H + W n , Cor–H + W n and Dbc–H + W n ( n = 1–3) as given in ref. 66. Indeed, different spectral shapes are computed for each set of complexes.…”

“…Although computations and experiments on the latter are challenging, recent investigations showed, indeed, that studying the series of small PAHs with increasing size gives several insights on the larger ones. 64–66 Besides, we target shedding light on the microsolvation induced effect of these H + PAHs targeting their physical chemical properties in aqueous solutions.…”