Integrating Rigidity and Regular Packing in Ag 6 Clusters via Ligand Fluorination: Toward High‐Efficiency Low‐Loss Optical Waveguiding

Ligand fluorination offers an effective approach to regulate both molecular packing and excited‐state properties in metal nanoclusters for optical waveguiding. In this study, a series of Ag 6 L 6 clusters, Ag 6 (PPT) 6 , Ag 6 (FPPT) 6 , and Ag 6 (2FPPT) 6 , were constructed using stepwise fluorinated ligands. All three clusters feature a slightly distorted octahedral Ag 6 core, while fluorination reorganizes intercluster interactions through C─H···F contacts, leading to more regular and compact crystal packing with enhanced lattice rigidity. Photophysical studies reveal that fluorination modulates the emission properties and increases the photoluminescence quantum yield from 35.66% to 98.67%. Theoretical simulations elucidate that fluorination localizes the lowest charge‐transfer excited states, simplifies the composition of excited states, and shifts the emissive states from greater metal‐centered character toward increased ligand participation, thereby favoring radiative decay and suppressing excited‐state absorption. Consequently, both absorption‐ and scattering‐related losses are effectively suppressed, resulting in a substantial decrease in optical loss coefficients from 0.04164 to 0.00365 dB µm −1 . Ligand fluorination emerges as a robust approach to achieving organized molecular packing, bolstered lattice rigidity, and refined excited‐state configurations, paving the way for high‐efficiency, low‐loss cluster‐based optical waveguides.