Two homotrinuclear Co(II) complexes, [Co₃(L)(OAc)₂(CH₃OH)₂] 2CHCl₃ (1) and [Co₃(L)(OAc)₂(H₂O)₂] (2) based on a naphthalenediol-based acyclic bis(Salamo)-type tetraoxime ligand were synthesized. 1 and 2 were influenced by the coordinated methanol and water molecules, respectively, and their X-ray crystal structures revealed that they have similar molecular structures. Two terminal Co(II) ions, located at the N₂O₂ coordination spheres of the Salamo moieties, are both in distorted trigonal-bipyramidal geometries, while the third Co(II) ion in the central O₄ cavity shows an octahedral geometry with two solvent molecules placed in the apical sites. Different solvent molecules lead to different supramolecular structures. The catecholase activities of 1 and 2 were examined using 3,5-di-tert-butylcatechol (3,5-DTBC) in acetonitrile solution under completely aerobic conditions. The catalytic reaction follows Michaelis–Menten enzymatic reaction kinetics with turnover numbers (K_cat) of 14.72 h⁻¹ and 26.39 h⁻¹ for 1 and 2, respectively.