Ligand Steric Profile Tunes the Reactivity of Indium Phosphide Clusters

Indium phosphide quantum dots have become an industrially relevant material for solid-state lighting and wide color gamut displays. The synthesis of indium phosphide quantum dots from indium carboxylates and tris(trimethylsilyl)phosphine (P(SiMe₃)₃) is understood to proceed through the formation of magic-sized clusters, with In₃₇P₂₀(O₂CR)₅₁ being the key isolable intermediate. The reactivity of the In₃₇P₂₀(O₂CR)₅₁ cluster is a vital parameter in controlling the conversion to quantum dots. Herein, we report structural perturbations of In₃₇P₂₀(O₂CR)₅₁ clusters induced by tuning the steric properties of a series of substituted phenylacetate ligands. This approach allows for control over reactivity with P(SiMe₃)₃, where meta-substituents enhance the susceptibility to ligand displacement, and para-substituents hinder phosphine diffusion to the core. Thermolysis studies show that with complete cluster dissolution, steric profile can modulate the nucleation period, resulting in a nanocrystal size dependence on ligand steric profile. The enhanced stability from ligand engineering also allows for the isolation and structural characterization by single-crystal X-ray diffraction of a new III-V magic-sized cluster with the formula In₂₆P₁₃(O₂CR)₃₉. This intermediate precedes the In₃₇P₂₀(O₂CR)₅₁ cluster on the InP QD reaction coordinate. The physical and electronic structure of this cluster are analyzed, providing new insight into previously unrecognized relationships between II-VI and III-V materials and the discrete growth of III-V cluster intermediates.