Controlling Metallophilic Interactions in Chiral Gold(I) Double Salts towards Excitation Wavelength-Tunable Circularly Polarized Luminescence

Angew Chem Int Ed Engl. 2020 Apr 20;59(17):6915-6922. doi: 10.1002/anie.202000792. Epub 2020 Mar 5.

Abstract

Materials exhibiting excitation wavelength-dependent photoluminescence (Ex-De PL) in the visible region have potential applications in bioimaging, optoelectronics and anti-counterfeiting. Two multifunctional, chiral [Au(NHC)2 ][Au(CN)2 ] (NHC=(4R,5R)/(4S,5S)-1,3-dimethyl-4,5-diphenyl-4,5-dihydro-imidazolin-2-ylidene) complex double salts display Ex-De circularly polarized luminescence (CPL) in doped polymer films and in ground powder. Emission maxima can be dynamically tuned from 440 to 530 nm by changing the excitation wavelength. The continuously tunable photoluminescence is proposed to originate from multiple emissive excited states as a result of the existence of varied AuI ⋅⋅⋅AuI distances in ground state. The steric properties of the NHC ligand are crucial to the tuning of AuI ⋅⋅⋅AuI distances. An anti-counterfeiting application using these two salts is demonstrated.

Keywords: anti-counterfeiting; aurophilicity; chiral N-heterocyclic carbenes; circularly polarized luminescence; excitation-dependent photoluminescence.