Characterization of NCs and their Stability. In the positive mode electrospray ionization mass spectrometry (ESI-MS), a discernible peak at m/z = 3204.74 unequivocally affirms the existence of the molecular peak corresponding to [Cu58H20(SPr)36(PPh3)0] 2+ (Figure ). However, achieving the molecular cluster peak featuring all the triphenylphosphine units attached to the cluster node poses considerable challenges due to its dynamic nature. Additionally, this task becomes even more difficult when defects are present in the structure. Nevertheless, we managed to attribute some of these units, m/z = 3335.78, 3467.83 and 3729.95 correspond to by transmission electron microscope (TEM) images, which show that their sizes are consistent with those measured by the SCXRD (Figure ). Given the highly stable nature of the synthesized NC in the solution medium, we proceeded to examine the effects of such defects on the optical properties. However, no changes were observed in the UV-vis absorbance spectrum in the solvent medium compared to our previously reported Cu58 NC (Figure ). So, it can be assumed that the distortion in the vertex Cu(I) atoms and the associated ligand vacancies have no impact on their electronic charge transition.