Quasi-Isomeric Anion-Templated Silver Nanoclusters: Effect of Bulkiness on Luminescence

Anion-templated silver nanoclusters are fascinating to study because of their diverse structures, which are dictated by the nature of both anions and ligands. Here, we used the bulky 1-ethynyladamantane as one of the protecting ligands alongside trifluoracetate to successfully synthesize a chlorine-templated silver nanocluster─Cl@Ag₁₉(C₁₂H₁₅)₁₁(C₂O₂F₃)₇. Elucidation of its structure by single crystal X-ray diffraction revealed the structure to be a chlorine-centered Ag₁₉ cage with protection by alkynyl and carboxylic ligands. This cluster is non-emissive at room temperature and showed green emission with a large Stokes shift at low temperature. The crystal structure was found to be quasi-isomeric with a previously reported Ag₁₉ cluster protected by tert-butyl acetylene, which is emissive at room temperature. Detailed photoluminescence studies and structure-property correlation revealed that the arrangement of the silver skeleton which is influenced by the bulky substituent of the ligand might be responsible for the difference in emission properties.