The Missing Chalcogen Bonding Donor: Strongly Polarized Oxygen of Water.

A biscyclen molecular cabin, synthesized by connecting two cyclen macrocycles with four linkages, entraps a Li + ···H 2 O···Li + trimer with a water molecule clamped by two Li + ions. This configuration results in strongly polarized water, characterized by a water proton resonance shift of up to 10.00 ppm. The arrangement facilitates unprecedented O-centered chalcogen bonds between the lone pairs of pyridinyl nitrogen atoms and polarized water oxygen, as confirmed by X-ray crystallography, NMR spectroscopy, and theoretical calculations. Further observation of O-centered chalcogen bonding in a H 2 O·(LiCl) 2 cluster suggests its widespread presence in hydrated salt systems.