Pyridoxal water-soluble cobalt(II) helicates: Synthesis, structural analysis, and interactions with biomacromolecules

Helical complexes composed of organic ligand strands and metallic centers, called helicates, present interactions with biomacromolecules, such as deoxyribonucleic acid, as one of their main biological applications in bioinorganic chemistry. Despite the potential antineoplastic and antibacterial results of the interactions between helicates and biomacromolecules, there is still a gap of research in the literature, primarily in terms of solubility in aqueous media. In this study, we present the synthesis, structural analysis, and interaction with biomacromolecules of two water-soluble cobalt(II) double-stranded helicates: [Co^II₂L²₂][Co^II(NCS)₄]∙9H₂O (C1) and [Co^II₂L⁴₂]Cl₂∙11H₂O (C2). These complexes are obtained from iminic ligands (L² and L⁴) derived from pyridoxal, a vitamin B6 aldehyde derivative. Through spectroscopic assays, these helical complexes were shown to have weak and moderate binding capacities with calf-thymus deoxyribonucleic acid and human serum albumin, respectively. The theoretical assays suggest that C1 and C2 interact with the minor groove of deoxyribonucleic acid and have different main binding sites with human serum albumin. Furthermore, Van der Waals and hydrogen bonds were shown to be the main intermolecular forces for these C1-C2:biomacromolecules interactions.