Asymmetric triiodide-diiodine interactions in the crystal of (Z)-4-chloro-5-((2-((4-chloro-5H-1,2,3-dithiazol-5-ylidene)amino)phenyl)amino)-1,2,3-dithiazol-1-ium oligoiodide

The crystal structure and properties of (Z)-4-chloro-5-((2-((4-chloro-5H-1,2,3-dithiazol-5-ylidene)amino)phenyl)amino)-1,2,3-dithiazol-1-ium oligoiodide (C2/c) synthesized from the initial bis(4-сhloro-5H-1,2,3-dithiazolo-5-ylidene)benzene-1,2-diamine (P21/c) have been characterized by various experimental and theoretic methods. The superposition of atomic basin boundaries in the electron density and in the electrostatic potential does not confirm the halogen bonding between the triiodide anion and sulfur atoms in cation. On the other hand, in the studied oligoiodide, the charge-assisted iodine–iodine halogen bonds are observed between the strongly asymmetric triiodide and diiodine units; thus, the oligoiodide anion includes at least two diiodine fragments with bond lengths 2.7334(4) and 2.7786(5) Å bound. This key trait has resulted in characteristic spectral and thermal features. Raman spectra do not contain typical triiodide bands but only those that are expectable for bound diiodine at 157 and 179 cm−1. Thermal decomposition has demonstrated release of both diiodine molecules within one decomposition stage without melting.