Linear Trimer Formation by Three-Center-Four-Electron Bonding in RuP

TL;DR

This paper reports the discovery of a linear ruthenium trimer with three-center-four-electron bonding in ruthenium monopnictide, formed during a metal-insulator transition, highlighting the role of molecular bonding in solid-state properties.

Contribution

It introduces a new type of molecular bonding in a solid-state material, demonstrating the formation of a 3c4e bonded ruthenium trimer during a phase transition.

Findings

Formation of a linear ruthenium trimer with 3c4e bonding

Charge transfer induces molecular formation during MIT

Molecular bonding influences electronic properties of solids

Abstract

In molecules like hydrogen, most chemical bonds are formed by sharing two electrons from each atom in the bonding molecular orbital (two-center-two-electron (2c2e) bonding). There are, however, different kinds of chemical bonding. The I3- molecule, for example, is noteworthy because three iodine atoms are linearly united by sharing four electrons (three-center-four-electron (3c4e) bonding). Some inorganic solids undergo phase transitions that result in the formation of "molecules" in their crystalline frameworks, which are often accompanied by dramatic changes in physical properties; the metal-to-insulator transition (MIT) in vanadium dioxide, for example, occurs with the formation of dimer molecules with 2c2e bonding. We repot the creation of a linear ruthenium trimer with 3c4e bonding in ruthenium monopnictide at its MIT. Charge transfer from polymerized phosphorous to ruthenium produces this unusual molecule, with all conduction electrons trapped by the bonding molecular orbital. Our results demonstrate that molecules are crucial even in solid crystals as they impact their electronic properties.