Size matters—sometimes. The [CuxIy](y−x)−(NR4)+(y−x) systems

Abstract

A systematic study of compounds formed by solvolysis of Cu in a solution of iodine in acetol in the presence of homotetraalkylammonium iodide has resulted in five new compounds: catenatetrakis(tetramethylammonium) bis(μ₃-iodo)-μ₂-iodo-tri-copper(I), hexakis(tetrabutylammonium) tetrakis(μ₃-iodo)-tris(μ₂-iodo)-di-iodo-hexa-copper(I) pentakis(μ₃-iodo)-tetrakis(μ₂-iodo)-di-iodo-hepta-copper(I), tris(tetrapentylammonium) μ₆-iodo-bis(μ₃-iodo)-hexakis(μ₂-iodo)-hexa-copper(I), hexakis(tetrahexylammonium) tetrakis(μ₅-iodo)-octakis(μ₂-iodo)-nona-copper(I)bis(μ₅-iodo)-bis(μ₄-iodo)-heptakis(μ₂-iodo)-octa-copper(I) and bis(tetraheptylammonium) hexakis(μ₂-iodo)-tetra-copper(I). Further the previously reported compounds catenatetraethylammonium bis(μ₃-iodo)-μ₂-iodo-di-copper(I) and catenatetrapropylammonium tetra(μ₃-iodo)-tri-copper(I) were produced by the same method. The complexity of the cuprous iodide clusters increases with increasing chain length of the counter ion. In the system with tetraheptylammonium as counter ion, the onset of crystallization was about two years! The luminescence properties that make some cuprous iodide cluster species interesting from an applications perspective are conspicuously absent in the compounds formed with the smaller tetraalkylammonium counter ions, but the compound formed with tetraheptylammonium contains the [Cu₄I₆]²⁻ unit that shows vivid luminescence when exposed to UV light.