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.

Three ternary complexes of sulfaquinoxaline (SQO – 4-amino-N-2-quinoxalinylbenzenesulfonamide) or sulfamethazine (SMT – 4-amino-N-(4,6-dimethylpyrimidin-2-yl)-benzenesulfonamide) with Cu(II) or Ni(II) and 2,2′-biquinoline (BQ) as an auxiliary ligand have been studied. Their structures have been determined by single-crystal X-ray crystallography as Ni(SQO)₂(BQ)·2H₂O (I), Cu(SQO)(BQ)Cl·CH₃OH (II) and Cu(SMT)(BQ)Cl (III). Compounds I and II crystallize in the triclinic space group P while complex III crystallizes in the monoclinic P2₁/c space group. The crystal lattice of all complexes is stabilized by the presence of diverse intermolecular interactions as verified by Hirshfeld surface analysis. Besides, electronic spectroscopies have also been used to characterize the compounds. The thermal behavior of the complexes was investigated by thermogravimetric and differential thermal analyses. Furthermore, the cytotoxic effect of the compounds has been tested against A549 (lung cancer) and MG-63 (human osteosarcoma) cell lines using the MTT methodology.