Tailoring Photonic Transport in Cluster-Assembled Crystals via Atomic-Level Coordination Engineering

The development of efficient optical waveguides requires precise control over photonic transport properties, yet linking atomic-level structure to device performance remains challenging. This study demonstrates that atomic-level coordination engineering of metal nanoclusters enables tailored photonic transport in cluster-assembled crystals. Using bidentate phosphine ligands as molecular scalpels, we constructed a series of Pt₁Ag_x (x = 18-37) nanoclusters with identical icosahedral kernels but systematically varied peripheral structures. The resulting crystals exhibit exceptionally low optical loss coefficient, with the Pt₁Ag₁₈SR₈Cl₂(DPPP)₄ (SR = 1-adamantanethiol, DPPP = 1,3-bis(diphenylphosphino)propane. Pt₁Ag₁₈-I for short.) crystal achieving a record-low among cluster-based active optical waveguides value of 6.4 × 10^-4 dB µm^-1. We establish quantitative positive correlations between waveguide performance and four key photophysical parameters: photoluminescence quantum yield, lifetime, refractive index, and polarization degree. This work provides a quantitative empirical structure-activity relationship (SAR) model for designing advanced photonic materials, bridging atomic-scale precision with macroscopic optical device functionality for next-generation integrated photonics.