Metal-Controlled Nuclearity in Phenol-Based Symmetric “End-Off” Compartmental Ligands Mediated by Acetate Anions: A DFT Study to Rationalize Their Formation

N₂O-donor Schiff-base compartmental ligands bearing pendant thienyl fragments and acetate anions were used for the synthesis of metal complexes, the nuclearity of which depends on the metal used. The X-ray structural characterization of complexes reveals the presence of tetranuclear copper(II), pentanuclear nickel(II), and hexanuclear zinc(II) ions. The presence of methylene- and ethylene-thienyl fragments, as well as different R groups (R = −CH₃, tert-But, or Cl), just alters the conformational arrangement in the complexes but not their nuclearity. All of the Cu(II) metal ions in their complexes present a slightly distorted square planar pyramidal coordination geometry, while the Ni(II) atoms exhibit a distorted octahedral O_h geometry. On the other hand, the three independent Zn(II) atoms in the hexanuclear complexes are both penta- and hexa-coordinated. In order to assess the formation of these polynuclear complexes with regard to the metal identity, a systematic study by using DFT calculations has been performed to acquire elucidation of the observed behavior.