Electronic Properties of π-Conjugated Nickel Bis(dithiolene) Network and Its Addition Reactivity with Ethylene

Density functional theory computations were performed to study the structure and electronic properties of the recently achieved two-dimensional nickel bis(dithiolene) single-layer sheet, as well as its cycloaddition activity with ethylene. The nickel bis(dithiolene) monolayer has a planar and porous network, and electrically acts as an indirect band gap semiconductor. Its lowest unoccupied state mainly distributes onto p orbitals of S atoms, which makes S atoms active to accept electrons from the occupied p orbitals of C═C bonds in ethylene. This is indeed confirmed by our computations, and the formation of the cis-interligand S,S′-adduct with an activation energy barrier of about 21 kcal/mol is energetically favored. When an extra electron is added, the addition product becomes destabilized and would dissociate into ethylene and nickel bis(dithiolene) anion. Therefore, with a controllable manner, the nickel bis(dithiolene) monolayer can bind and release ethylene molecules in neutral and reduction conditions, respectively. Because of its unique chemical reactivity, this newly achieved nickel bis(dithiolene) sheet can be potentially developed as an electrocatalyst in olefin separation and purification.