A Reversible Polymorphic Phase Change Which Affects the Luminescence and Aurophilic Interactions in the Gold(I) Cluster Complex, [μ3-S(AuCNC7H13)3](SbF6)

Abstract

Crystallographic examination of [μ₃-S(AuCNC₇H₁₃)₃](SbF₆) shows that it undergoes a reversible phase change from orthorhombic to monoclinic upon cooling. At 190 K, the structure shows that two cations self-associate to form a pseudo-octahedral array of six gold atoms connected by both intra- and interionic aurophilic interactions. On cooling, the clusters become less symmetric, and in one, the interionic Au···Au separations increase, while they decrease in the second cluster. The luminescence of crystalline [μ₃-S(AuCNC₇H₁₃)₃](SbF₆) shows corresponding changes in emission, with two emissions of similar lifetimes but with different excitations at 77 K, but only a single emission at 298 K. In contrast, [μ₃-S(AuCNC₆H₁₁)₃](PF₆), which has a similar structure to that of the high-temperature form of [μ₃-S(AuCNC₇H₁₃)₃](SbF₆), does not undergo a phase change or change in its luminescence upon cooling.