Revealing the Electronic Structure of Water Imprinted in the Chiral Molecular Environment

Water plays a crucial role in determining the functions of biomolecules and nanomaterials. However, the electronic structure of water molecules at the nanoscale remains elusive. In this study, we investigate the electronic structure of water molecules imprinted in chiral Ag(I) thiolate complexes (-SRs) by using cysteine as a probe ligand. By employing a chirality transfer strategy and analyzing absorption and circular dichroism (CD) spectra, we identify three types of structural water molecules (SWs) within the Ag(I)-SRs. These SWs exhibit unique electronic interactions between the outermost p-orbitals of oxygen atoms due to spatial confinement, forming electronic states with a molecule-like structure. Notably, the distinctive electronic structure of SWs generates a pair of absorption signals with opposite Cotton effects, which can be captured by CD spectroscopy in a chiral molecular environment. Our theoretical calculations using the one-dimensional free electron gas model align well with experimental results, and the Cotton effect exhibited by these SWs is explained by a simple octant rule. This study provides novel insights into the electronic structure of water in confined nanospaces and highlights its potential role in various biological and material systems.