The MC-QTAIM analysis reveals an exotic bond in the coherently quantum superposed Malonaldehyde

TL;DR

This study uses advanced quantum analysis to reveal an exotic, stabilizing hybrid bond in malonaldehyde arising from quantum superposition, challenging traditional views of molecular bonding.

Contribution

The paper introduces a novel quantum analysis revealing a unique hybrid oxygen-hydrogen bond in malonaldehyde due to superposition effects.

Findings

Disappearance of the hydrogen basin in superposed states

Appearance of hybrid oxygen-hydrogen basins with equal proton distribution

Stabilization of the hybrid bond via Coulomb interaction between basins

Abstract

The proton between the two oxygen atoms of the malonaldehyde molecule experiences an effective double-well potential in which the proton wavefunction is delocalized between the two wells. Herein we employed the state-of-the-art multi-component quantum theory of atoms in molecules partitioning scheme to obtain the molecular structure, i.e. atoms in molecules and bonding network, from the superposed ab initio wavefunctions of malonaldehyde. In contrast to the familiar clamped-proton portrayal of malonaldehyde, in which the proton forms a hydrogen basin, for the superposed states the hydrogen basin disappears and two novel hybrid oxygen-hydrogen basins appear instead, with an even distribution of the proton population between the two basins. The interaction between the hybrid basins is stabilizing thanks to an unprecedented mechanism. This involves the stabilizing classical Coulomb interaction of the one-proton density in one of the basins with the one-electron density in the other basin. This stabilizing mechanism yields a bond foreign to the known bonding modes in chemistry.