Synthesis and crystal structure of tetra-kis-(ethyl-ammonium) hepta-iodide(3-) iodide.

Abstract

The crystal structure of the title salt, 4C2H5NH3+·I73-·I-, comprises disordered ethyl-ammonium cations accompanied by an isolated and disordered I- anions and [I7]3- polyiodide anions. The positional disorder of the ethyl-ammonium cations and isolated I- anions is caused by the crystallographically imposed mirror symmetry. The entire [I7]3- polyanion exhibits point group symmetry 2/m and is composed of two neutral I2 mol-ecules acting as connectors between three I- anions. The hepta-iodide anion has a unique linear conformation and forms a slipped-stack layered arrangement along the c axis. The organic cations are accommodated between the anionic units and are linked to them via N-H⋯I hydrogen bonds, establishing a supra-molecular framework. As a novel polyiodide compound, the reported structure expands the known structural diversity and topologies of complex iodine-based systems.

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