Luminescent Thermochromism in a Gold(I)–Copper(I) Phosphine–Pyridine Complex

Abstract

AbstractThe AuI complex [Au(Ph2PCH2py)2]BF4 (1) was prepared by mixing (tetrahydrothiophene)gold(I) chloride with 2‐[(diphenylphosphino)methyl]pyridine (Ph2PCH2py) in dichloromethane. The addition of [Cu(NCCH3)4]BF4 to 1 produced green‐luminescent [AuCu(Ph2PCH2py)2(NCCH3)2](BF4)2 (2). When crystals of 2 were exposed to air, two acetonitrile molecules were lost to form crystals of yellow‐luminescent [AuCu(Ph2PCH2py)2](BF4)2 (3). This simple solvent loss perturbs the environment around the CuI center, and the Au···Cu distance shortens from 3.3 to 2.8 Å. Crystallization of 2 or 3 from dichloromethane produced the two‐coordinate CuI–solvate complex, [AuCu(Ph2PCH2py)2](BF4)2·CH2Cl2 (3·CH2Cl2). Compound 3 exhibits temperature‐dependent emissions from 77 to 298 K (543 nm), 298 to 343 K (551 nm), and above 343 K (505 nm) that is reversed upon return to room temperature. The low‐temperature emission is typical of complexes with luminescent rigidochromic properties. However, based on differential scanning calorimetry, a phase change is responsible for the high‐temperature emission of 3.