Silver(I) as a Noncovalent Bond Acceptor: A Theoretical Study of ClAgL₃ Complexes (L = etu, dmtu, ettu, pip)

A systematic theoretical study was conducted on the interactions of ClAgL₃ (L = imidazolidine-2-thione (etu), dimethylthiourea (dmtu), N-ethylthiourea (ettu), piperidine (pip)), and the corresponding Cu-containing compounds with typical σ-hole donors (I₂/1,4-C₆F₄I₂) and π-hole donors (C₆F₆/1,4-C₆F₄I₂). The d_z²-nucleophilicity of the metal centers is enhanced by the presence of strong electron-donating ligands, thus functioning as a halogen bond acceptor. The majority of metal-involving Ag···I halogen bonds and three-center bifurcated (Ag-S)···I halogen bonds exhibit the closed-shell characteristics of weak interactions, while the Ag···I halogen bond in ClAg(pip)₃···I₂ and the Cu···I halogen bonds in XCuL₃···I₂ display partially covalent character. The coordination S atoms in the metal compounds were observed to form medium conventional S···I halogen bonds, which exhibit a partially covalent nature. The {d_z²-AgS₃}/{d_z²-AgN₃} moiety functions as an integrated four-center acceptor toward the π-hole of electron-deficient arenes. The chemical bonds between ClAgL₃ and π-hole donors are characterized by closed-shell noncovalent interactions. It has been demonstrated that electrostatic interaction is typically responsible for the stability of complexes. For S···I halogen bonds in XML₃···I₂(B), electrostatic interactions have been shown to account for a substantial proportion of the total attraction, while the correlation contribution is comparatively negligible. The contribution of the electrostatic term is observed to decrease gradually in the Ag/Cu···I, (Ag-S)···I halogen bonds and π-hole interactions, while the contribution of dispersion is found to increase gradually.