Infrared spectroscopy of hydrated N-(2-phenylethyl)acetamide clusters: The electron-redistribution within the solute weakens local hydrogen bond

Highlights: ► The IR-dip spectroscopy has been applied to investigate the H-bond interaction of the hydrated NPEA cluster cation. ► The spatially separated water molecules influence their intermolecular interactions. ► The electrons are redistributed to enhance the total intermolecular interactions in the D0 state of hydrated NPEA cluster. - Abstract: The hydrated N-(2-phenylethyl)acetamide (NPEA) clusters have been investigated in the gas phase. In the S0 state of NPEA-(H2O)2, each of two water molecules is hydrogen-bonded to the NH and CO groups, respectively, whereas these two groups are bridged with three water molecules in the S0 state of NPEA-(H2O)3. Upon photoionization of these clusters, mono- and dihydrated NPEA cluster cations are produced, where a water molecule is hydrogen-bonded to the NH group. In [NPEA-(H2O)2]+, the other water molecule is located near the CO group of NPEA+ due to a charge–dipole interaction. The electrons of NPEA+ are redistributed to enhance the total intermolecular interactions, leading to weakening the hydrogen bond in [NPEA-(H2O)2]+