Confinement-Driven Transient Coordination Complexes: H2 Dissociation and Quantum Channel Modification in Single-Atom Contacts
Year: 2026
Type: preprint
Abstract: Understanding chemical reactivity at cryogenic temperatures is essential for advancing both fundamental quantum science and next-generation catalytic technologies. At the single-atom limit, geometric confinement can promote ground-state electronic effects that drive novel chemical events without thermal activation. Using the H2 interaction with transition-metal nanocontacts as a benchmark, we report the barrierless formation of a transient tip complex characterized by a diborane-like 4-electron, 3-center bond (Pt–H ~0.17 and 0.18 nm). This 2 ground-state dissociation acts as a selective quantum channel modifier: while the intact, physisorbed molecule yields a conductance of ~0.2 G0, the dissociated transient complex results in a quantized conductance of 1 G0. This mechanism is correctly captured by mean-field orbital models when proper non-local exchange corrections are effectively considered. Furthermore, while bulk palladium is renowned for its high hydrogen affinity, our mean-field models and quantum calculations demonstrate the opposite: Pd nanocontacts merely physisorb H2 (H–H ~0.08 nm), behaving as a noble metal at this quantum limit. These findings illustrate how geometric confinement can drive novel chemical events, opening new avenues for zerotemperature catalysis at the single-atom limit.
Source: ChemRxiv
Authors: Yamila García, Yamila Garcia-Martinez
Institution: Universidad Internacional de La Rioja
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7214768941