Polyiodides are interesting compounds with unique structures depending on the surrounding molecules. A vast number of polyiodide structures exist already in literature. These compounds are stabilized by counterions or complexation and lead from basic structures to extended three-dimensional networks of polyiodides. Iodine is known as a microbicide since centuries throughout many cultures. We prepared a copper-12-crown-4-hexahydrate complexed pentaiodide with polymeric structure and investigated its structure and antimicrobial properties against nine microbial reference strains. The compound [Cu(H₂O)₆(12-crown-4)₅]I₆ ´ 2I₂ showed excellent antifungal and intermediate antibacterial properties in comparison to common antibiotics. The structure of the chain-type pentaiodide is remarkable and can be described as triiodide ions connected to two iodine molecules.