Role of Anions and Mixtures of Anions on the Thermochromism, Vapochromism and Polymorph Formation of Luminescent Crystals of a Single Cation, [(C6H11NC)2Au].

Non-coordinating anions, which generally play a subordinate role in coordination chemistry, alter the structure, lumines-cence, as well as the thermochromic and vapochromic behaviors of salts of the two-coordinate cation, [(C6H11NC)2AuI]+. Thus, while the yellow polymorphs of [(C6H11NC)2AuI](PF6) and [(C6H11NC)2AuI](AsF6) contain single chains of cations and are vapochromic, yellow [(C6H11NC)2AuI](SbF6) does not form the same polymorph, is not vapochromic, but contains two distinct chains of cations connected through aurophilic interactions. Mixed crystals such as [(C6H11NC)2AuI](PF6)0.50(AsF6)0.50 have been prepared by adding diethyl ether to a dichloromethane solution containing equimolar amounts of [(C6H11NC)2AuI](PF6) and [(C6H11NC)2AuI](AsF6). The initial (kinetic) product for the three combina-tion of anions ((PF6)-/(AsF6)-; (PF6)-/(SbF6)-; and (AsF6)-/(SbF6)-) was a precipitate of fine yellow needles with a green emis-sion, which were gradually transformed at rates that depended upon the anions present, into colorless crystals with a blue emission. While neither polymorph of [(C6H11NC)2AuI](PF6) nor [(C6H11NC)2AuI](SbF6) is thermochromic, the colorless mixed crystal [(C6H11NC)2AuI](PF6)0.50(SbF6)0.50 is thermochromic and converts from blue-emitting to green-emitting at 87-95 °C. The temperature required to transform a crystal of the type [(C6H11NC)2Au](PF6)n(AsF6)1-n from colorless (blue-emitting) to yellow (green-emitting) increases as the fraction of hexafluorophosphate ion in the crystal increases. The yellow crystals of [(C6H11NC)2AuI](PF6)0.75(AsF6)0.25, [(C6H11NC)2AuI](PF6)0.50(AsF6)0.50, and [(C6H11NC)2AuI](PF6)0.25(AsF6)0.75 are vapochromic, whereas the yellow crystals of [(C6H11NC)2AuI](PF6)0.50(SbF6)0.50 and [(C6H11NC)2AuI](AsF6)0.50(SbF6)0.50 are not.