Antimicrobial Hexaaquacopper(II) Complexes with Novel Polyiodide Chains

• Main Authors: Zehra Edis, Radhika Raheja, Samir Haj Bloukh, Richie R. Bhandareh, Hamid Abu Sara, Guido J. Reiss
• Format: Article
• Language: English
• Published: MDPI AG 2021-03-01
• Series: Polymers
• Subjects: antimicrobial agents; polymeric pentaiodides; copper; crown-ether; halogen bonding; crystal structure
• Online Access: https://www.mdpi.com/2073-4360/13/7/1005

The non-toxic inorganic antimicrobial agents iodine (I₂) and copper (Cu) are interesting alternatives for biocidal applications. Iodine is broad-spectrum antimicrobial agent but its use is overshadowed by compound instability, uncontrolled iodine release and short-term effectiveness. These disadvantages can be reduced by forming complex-stabilized, polymeric polyiodides. In a facile, in-vitro synthesis we prepared the copper-pentaiodide complex [Cu(H₂O)₆(12-crown-4)₅]I₆ ´ 2I₂, investigated its structure and antimicrobial properties. The chemical structure of the compound has been verified. We used agar well and disc-diffusion method assays against nine microbial reference strains in comparison to common antibiotics. The stable complex revealed excellent inhibition zones against <i>C. albicans WDCM 00054</i>, and strong antibacterial activities against several pathogens. [Cu(H₂O)₆(12-crown-4)₅]I₆ ´ 2I₂ is a strong antimicrobial agent with an interesting crystal structure consisting of complexes located on an inversion center and surrounded by six 12-crown-4 molecules forming a cationic substructure. The six 12-crown-4 molecules form hydrogen bonds with the central Cu(H₂O)₆. The anionic substructure is a halogen bonded polymer which is formed by formal I₅⁻repetition units. The topology of this chain-type polyiodide is unique. The I₅⁻repetition units can be understood as a triodide anion connected to two iodine molecules.