LAUSR

A mechanistic pathway is presented for the evolution of CdSe and CdTeSe magic‐size clusters (MSCs) in dispersion of CdTe MSC‐371 (displaying optical absorption peaking at ≈371 nm), MSC‐417, and/or MSC‐448 at room temperature. Synthesized with a 4Cd‐1Te feed molar ratio, the CdTe sample was dispersed in a mixture of octylamine and toluene, and CdTe MSCs appeared. After the presence of selenourea, CdSe MSCs evolved. Moreover, Moreover, MSC‐371 decreased and CdTeSe MSC‐399 developed, while MSC‐417 and MSC‐448 changed little. The evolution of CdSe MSCs is attributed to the reaction of selenourea and the Cd precursor in the CdTe sample, contrary to the hypothesis of anion exchange. The systematic and critical approach not only brings deeper insights into the formation and transformation of the prenucleation cluster (PNC) and the precursor compound (PC) of MSCs, but also illuminates a robust framework of monomer substitution enabling the formation of MSC‐399 instead of MSC‐417 from PC‐371.