Previously synthesized crystals of [(C6H11NC)2Au]PF6 and [(C6H11NC)2Au]AsF6 both display polymorphism; each has a known yellow, green-luminescent polymorph and colorless, blue-luminescent polymorph. Thermochromic properties have only been observed in the colorless AsF6- polymorph, which turns yellow prior to melting. However, introducing trace amounts of AsF6- to PF6- crystals can produce the same result. The effects of mixing various ratios of the AsF6- to PF6- anions in these [(C6H11NC)2Au]+ crystals have been studied to explore the extent of thermochromic behavior in these crystals. Additionally, a newly synthesized crystal of [(C6H11NC)2Au]SbF6 only has as a pale yellow, blue-luminescent form; no polymorphism is known. However, upon crystallization of [(C6H11NC)2Au]+ with mixed SbF6- and PF6- anions, a colorless, blue-luminescent crystal form was produced that is isostructural to the colorless PF6- crystal. Mixing these anions has allowed the SbF6- species to crystallize in a different structural arrangement for the first time. Furthermore, neither the SbF6- and PF6- species individually possess thermochromic properties; but together in the mixed anion crystal, thermochromic behavior has been observed as the crystal changes from colorless to yellow with increasing temperature. No single-crystal-to-single-crystal phase transition has been observed in any case of these new mixed anion crystals.

Thermochromic properties of mixed anion crystals of bis(cyclohexyl isocyanide) gold(I) complexes

2019 Fall National Meeting

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