The already reported monomeric complex Co(SDZ)₂bpy (1) and the new ternary complex Co(SDZ)₂(6MQ)₂ (2) (SDZ = sulfadiazine, bpy = 2,2′‐bipyridine, and 6MQ = 6‐methoxyquinoline) have been synthesized in order to study their magnetic properties. X‐ray diffraction studies indicate that in both compounds the SDZ acts as a bidentate ligand coordinating through the sulfonamide and the pyrimidine N atoms giving rise to a CoN₆ coordination sphere. The complexes have been characterized based on elemental analyses, FTIR, UV/Vis spectroscopy, and thermogravimetric analysis (TGA, only for 2). Compounds 1 and 2 have been characterized magnetically, and they show slow relaxation of the magnetization below 9 and 6 K, respectively.

Five monomeric complexes of Co(II), Cu(II), Ni(II), Zn(II) and Ag(I) with 6-methoxyquinoline (6-MeOQ) as ligand have been prepared, and their crystal structures have been determined by single X-ray diffractions. The Cu(II), Ni(II) and Zn(II) complexes are formulated as M(6-MeOQ)₂Cl₂, completing MN₂Cl₂ coordination spheres. On the other hand, Co(II) and Ag(I) compounds are ionic with formulae [Ag(6-MeOQ)₂]⁺ NO₃ ⁻ and H(6-MeOQ)⁺[Co(6-MeOQ)Cl₃]⁻ (where H(6-MeOQ)⁺ is the protonated ligand). Hirshfeld surface analysis was employed to study the intermolecular interactions in the crystal lattices and from these studies it was found that π-stacking contacts play an important role. Besides, the complexes have been characterized by FTIR, UV-visible and emission spectroscopies. The singlet oxygen production and fluorescence quantum yields were measured for all the complexes employing steady-state methodologies. Finally, the antibacterial activity of the complexes was screened against both Gram-positive and Gram-negative bacteria.