Phosphorescent organogels via "metallophilic" interactions for reversible RGB-color switching

A trinuclear Au(I) pyrazolate complex bearing long alkyl chains (1) in hexane self-assembles via a Au(I)-Au(I) metallophilic interaction, to form a red-luminescent organogel (λ_em = 640 nm, λ _ext = 284 nm). Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis of an air-dried gel with 1 show the presence of heavily entangled fibers, each consisting of a rectangularly packed columnar assembly of 1. Doping of the organogel with a small amount of Ag⁺ results in a blue luminescence (λ_em = 458 nm, λ_ext = 370 nm) without disruption of the gel, while removal of doped Ag⁺ with cetyltrimethylammonium chloride results in complete recovery of the original red-luminescent gel. Upon heating, these organogels undergo gel-to-sol transition due to the destabilization of the metallophilic interactions, where the red luminescence of the nondoped system becomes hardly visible, while the blue luminescence of the Ag⁺-doped system turns green (λ_em = 501 nm, λ_ext = 370 nm). On cooling, these solutions undergo gelation and synchronously recover the original luminescences. The observed RGB (red-green-blue) luminescences are all long-lived (3-6 μs) and assigned to electronic transitions from triplet-excited states.