Self-Assembled Luminescent Au(I)-Adamantylamine Coordination Polymer Needles With Thermoresponsive Optical Properties

A luminescent Au(I) coordination polymer, [AuCl(1-AdmNH₂)]_n was synthesized under mild conditions via spontaneous reduction of HAuCl₄ by excess 1-adamantylamine (1-AdmNH₂). The resulting needle-like, hydrophobic solid exhibits intense red phosphorescence (λ_em≈ 680 nm) under UV light (254 nm). Single-crystal X-ray diffraction reveals linear Au(I) chains stabilized by aurophilic interactions and hydrogen bonding. The needles have diameters around 500 nm and lengths of tens of microns. Photophysical studies, including quantum yield (QY ≈ 2.4%), microsecond-scale lifetimes, and time-dependent density functional theory (TD-DFT) calculations, indicate a triplet-state phosphorescence mechanism involving metal-centered (MC) and ligand-to-metal-metal charge transfer (LMMCT) transitions. The material exhibits thermal stability up to 160°C but degrades in coordinating solvents, forming gold nanoparticles. When evaluated for luminescent thermometry, it shows high sensitivity up to 160°C, a performance unprecedent among non-lanthanide-based coordination polymers. It remains operational up to 100°C with a sensitivity not previously achieved in coordination polymer (CPs) systems.