Beyond a single structure: complementary IR and NMR signatures of multi-minima noncovalent binding

Abstract

Hydridic hydrogen atoms, where hydrogen carries increased electron density, form a distinct class of noncovalent interactions, yet their structural and energetic characteristics remain poorly understood. Shallow multi-minima potential-energy surfaces and competing low-energy docking motifs make conventional NMR insufficient to resolve individual interactions. Using a triethylsilane⋯1,4-diiodoperfluorobutane complex, we demonstrate that hydridic Si–H⋯I interactions coexist with competing C–H⋯I, C–H⋯F and repulsion-wall motifs as well as numerous dispersion energy contributions producing diverse Si–H vibrational signatures in cryogenic ATR-IR spectra. Combined with quantum-chemical calculations, these data reveal that hydridic hydrogen bonds stabilize specific docking geometries, modulate local electrostatics, and contribute to association energies, even when conventional NMR signals appear averaged. Our results establish hydridic hydrogen bonding as a tunable, structurally and energetically distinct noncovalent interaction, providing a framework for rational design of organosilicon catalysts, supramolecular assemblies, and molecular recognition systems in chemistry and biology.