The previous post described the fascinating 170-year history of a crystalline compound known as Herapathite and its connection to the mechanism of the Finkelstein reaction via the complex of Na + I 2 – (or Na 2 2+ I 4 2- ). Both compounds exhibit (approximately) linear chains of iodine atoms in their crystal structures, a connection which was discovered serendipitously.
AbstractWe report the preparation and X‐ray crystallographic characterization of the first crystalline homoatomic polymer chain, which is part of a semiconducting pyrroloperylene–iodine complex. The crystal structure contains infinite polyiodide I∞δ−. Interestingly, the structure of iodine within the insoluble, blue starch–iodine complex has long remained elusive, but has been speculated as having infinite chains of iodine. Close similarities in the low‐wavenumber Raman spectra of the title compound and starch–iodine point to such infinite polyiodide chains in the latter as well.