All three Cu NCs were synthesized using a one-pot direct reduction strategy, as depicted in Scheme 1. Generally, in NC synthesis, the choice of ligand plays a pivotal role in directing the assembly of metal ions, as the interaction between metal ions and ligands determines the nuclearity and structural architecture of the resulting NC. However, in this study, the carefully optimized synthetic protocols consistently yielded NCs with the same number of Cu(I) atoms in their assemblies, regardless of the variation in ligand systems. Interestingly, the study also demonstrates that altering the reaction conditions while keeping the ligand system constant can result in NCs with distinct structural geometries. In a typical synthetic route, hexagonal yellow crystals of Cu11PTT NC were obtained by reacting a Cu(I) precursor with PTT and PPh3 ligands in a CH3CN medium, using t BuNH2•BH3 as a mild reducing agent. During the transition from PTT to ABT as the ligand system, maintaining the same number of Cu(I) atoms in the resulting NC required strategic modifications to the reaction conditions. This was achieved by replacing the mild reducing agent with a stronger one and adjusting the solvent medium accordingly. Specifically, the use of NaBH4 significantly altered the reaction dynamics, leading to the formation of yellow-colored rhombohedral crystals of Cu11ABT NC while preserving the nuclearity of the NC. Conversely, when the reducing agent was altered at the initial reaction by retaining the same PTT ligand, a notable rearrangement occurred in the number of Cu atoms forming the NC. This change in reaction dynamics resulted in the synthesis of Cu18PTT, a yellow-colored NC with an elongated square gyrobicupola-like crystal morphology. These observations highlight the intricate interplay between the reducing agent and ligand in dictating the nuclearity and geometry of the resulting Cu NCs.