Size-selective Pt siderophores based on redox active azo-aromatic ligands

We demonstrate a strategy inspired by natural siderophores for the dissolution of platinum nanoparticles that could enable their size-selective synthesis, toxicological assessment, and the recycling of this precious metal. From the fabrication of electronics to biomedical diagnosis and therapy, PtNPs find increasing use. Mitigating concerns over potential human toxicity and the need to recover precious metal from industrial debris motivates the study of bio-friendly reagents to replace traditional harsh etchants. Herein, we report a family of redox-active siderophore-viz. π-acceptor azo aromatic ligands (L) that spontaneously ionize and chelate Pt atoms selectively from nanoparticles of size ≤6 nm. The reaction produces a monometallic diradical complex, Pt^II(L˙^-)₂, isolated as a pure crystalline compound. Density functional theory provides fundamental insights on the size dependent PtNP chemical reactivity. The reported findings reveal a generalized platform for designing π-acceptor ligands to adjust the size threshold for dissolution of Pt or other noble metals NPs. Our approach may, for example, be used for the generation of Pt-based therapeutics or for reclamation of Pt nano debris formed in catalytic converters or electronic fabrication industries.