Sulfide-mediated growth of NIR luminescent Pd/Ag atomically precise nanoclusters

An essential feature of coinage metal nanoclusters (NCs) is their photoluminescence (PL), which spans a wide range of wavelengths from visible to near-infrared regions (NIR-I/II). A key challenge for synthetic chemists is to develop materials capable of efficient spectral change with maximum efficiency. Herein, we report novel dithiolate-protected bimetallic Pd-Ag NCs of the type [PdAg₁₆S₂{S₂P(OR)₂}₁₂] (R = ⁱPr, 1Pr and ⁱBu, 1Bu) and [Pd₆Ag₁₄S{S₂P(OⁱBu)₂}₁₂] (2Bu). Sulfide-mediated expansions of NCs result in unique PL in the NIR-I region for 1Pr and 1Bu (λ_max = 808 and 811 nm) and the NIR-II region for 2Pr (λ_max = 1007) at 77 K. NIR PL enhancement largely depends on structural modification with the sulfide anions at the central position. DFT calculations indicate that the PL properties are associated with 4d_π(Pd)/3p_π(S) → 5s/5p(Ag) excitation, resulting from the existence of S-Pd(0)-S motifs in both 1 and 2. The electrochemical gaps of 1Pr, 1Bu, and 2Bu are recorded by SWV.