Nature of the Excited State of Triangulo Silver N-Heterocyclic Carbenes. Insights from Relativistic DFT Calculations

Abstract

Insights into the ground and excited states involved in the reported luminescent behavior of a complex involving the Ag(3) core stabilized by pyridil derivatives of N-heterocyclic carbenes has been achieved by means relativistic DFT calculations including scalar and spin-orbit coupling. The stabilization of the [Ag(3)](3+) core is enhanced by the population of a highly symmetric bonding Ag(3) orbital, composed of 75% from the 5s, 15% from 5p, and 10% from 4d. Thus, stabilization of the Ag(3) core involves a slightly bonded d(10) metallic core in addition to the pure nonbonding argentophilic interaction picture. It is suggested that the population of this highly bonding [Ag(3)](3+) orbital is responsible of the short Ag-Ag bond length observed in the studied compounds. The characterized electronic excitations allows to rule that the metal-ligand to ligand charge-transfer transitions account for the luminescent properties. The calculated Stokes shifts are in good agreement with the experimental data.