Incommensurately modulated sodium polyiodide crystal structure discloses unconventional 1D iodine chains

Here, we report crystallographic results about gold-green crystals with metallic luster of [Na(DMSO)3]n(I2)n. XRD studies reveal that [Na(DMSO)3]n(I2)n, containing 1D iodine infinite chains is incommensurately modulated. This confutes earlier reports and potentially resolves the unclear duality about the absence/presence of bond length alternation in such chains, reported with oddities and incongruences in previously published data for several 1D iodine infinite chains, from the discovery of the starch-iodine complex (1810s) up to the first (claimed) solved structure of this kind (2016). This work is relevant for understanding chemical bonds in 1D chains, it validates the recently proposed unified view of multicenter bonds, and it helps our understanding of challenging structures, like the mentioned starch-iodine blue complex. The crystals, initially serendipitously crystallized, are obtained by fusion, mechanochemical synthesis, and I2 gas adsorption and present manifest dichroic behavior with red-brown transmittance and green reflectance.