The stability of large ligated copper(I) clusters of undeca; and, dodecanuclearity encapsulating iodide and stabilized by dithio- and diseleno-phosph(in)ates was investigated by density functional theory (DFT) calculations. A bonding analysis is provided, which shows strong iono-covalent bonding between the iodide and its host. The electronic structures of the title compounds suggest the possibility for interesting photoluminescent properties, which were fully investigated by time-dependent DFT calculations including vibronic contributions to, simulate the phosphorescence spectra. The quantum mechanical results were compared to the experimental data "obtained for the new clusters [Cu-11(mu(9)-I)(mu(3)-I)(3){Se2P((OPr)-Pr-i)(2)}(6)](+) and [Cu-11(mu(9)-I)(mu(3)-I)(3)(Se2PPh2)(6])(+) whose syntheses, X-ray structures, and full characterizations are reported in this paper. From this combined theoietical/experimental investigation, it is suggested that the encapsulation by the same copper(I) cages of a formally Cu- anion is also possible. DFT calculations on these species are consistent with the existence of stable two-electron superatoms.