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 Title: Unravelling The Microsolvation Framework Around Prototype Polycyclic Aromatic Hydrocarbon, Naphthalene, By High-resolution Infrared Spectroscopy Author(s): Chatterjee, Kuntal Contributor(s): Havenith, Martina; Khatri, Jai; Roy, Tarun Kumar Subject(s): Clusters/Complexes Abstract: Solvation of aromatic molecules is a fundamental chemical process. Stability and function of almost all biomolecules are governed by the surface water molecules, typically known as biological water. Despite a plethora of reports available for the prototype aromatic molecule, benzene,$^{1}$ studies related to the solvation of larger aromatic moieties are rather scarce. Herein, we probe the microsolvated structures of the simplest polycyclic aromatic hydrocarbon, naphthalene (Np), by high-resolution infrared (IR) spectroscopy inside helium nanodroplets and quantum chemical calculations. Our results show that in the monohydrated Np-water dimer, solvent water preferentially binds to the $\pi$ electron cloud of the two fused phenyl rings via OH-$\pi$ hydrogen bonds (H-bond) and acts as a double H-bond donor. This binding motif is strikingly different from the corresponding cationic Np-water complex, in which water lies in the Np-ring plane and acts as a double H-bond acceptor by the simultaneous formation of two CH-O H-bonds.$^{2,3}$ Therefore, we see the presence or absence of charge causes a substantial modification of solvent binding motif. Further stepwise water-addition to neutral Np-water complex leads to evolution of H-bond network as reflected from the IR spectra. In larger Np-(water)$_{2,3}$ clusters, hydration motifs mimic the bare water network and thus leads to the formation of linear H-bonded water dimer and cyclic water trimer, which simultaneously interact with Np $\pi$ electrons. Changing the solvent from water to methanol does not change the qualitative $\pi$ bonding motif. However, in this case, the solvent only interacts with a single phenyl ring via a OH-$\pi$ H-bond due to the presence of a single proton donor. The addition of the second solvent molecule leads to the formation of H-bonded methanol dimer that interacts with Np. \textbf{References:} 1. R. N. Pribble and T. S. Zwier, Science, 1994, 265, 75 2. K. Chatterjee and O. Dopfer, Chem. Sci., 2018, 9, 2301. 3. K. Chatterjee and O. Dopfer, Phys. Chem. Chem. Phys., 2017, 19, 32262 Issue Date: 2021-06-25 Publisher: International Symposium on Molecular Spectroscopy Genre: Conference Paper / Presentation Type: Text Language: English URI: http://hdl.handle.net/2142/111355 Date Available in IDEALS: 2021-09-24
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