The structure and optical properties of several polynuclear gold(I) species, namely, diselenophosphate [Au{mu-Se2P(OR)(2)}](2) complexes (R = Pr-i, Et, Pr-n) respectively numbered 1, 2, and 3 and number 4 [Au{mu-Se2P(CH2)(2)Ph)(2)}](2), exhibiting interesting structural, absorption, and emission properties have been studied. The synthesis, full characterization, and experimental spectroscopic study of 3 and 4 have first been carried out, 1 and 2 being previously studied. In the solid state, 3 gives polymers, like 1 and 2, whereas 4 exists under a dinuclear monomeric form. The absorption and phosphorescence properties of 4 have been rationalized using DFT and TDDFT computations. In particular, Au-Au bonding seems to appear in its first singlet and triplet states, whereas such a bond does not exist in the ground state. Then, the influence of polymerization through aurophilic bonding on the optical properties of 2 is investigated (1 and 3 behave as 2). It is shown using TDDFT computations that its observed UV-visible excitation spectrum in solution is due to high oligomers and not to monomers or low size oligomers. ESI-MS molecular weight measurements confirm the occurrence of such oligomers of 2 in solution. An assignment of the observed bands of 2 is proposed. The transition corresponding to the first excitation band, which is mainly a HOMO to LUMO one, exhibits metal-centered character, i.e., a gold 5d to 6p orbital transition, but concomitantly transfers significant electron density from gold to phosphorus atoms so that it is also a MLCT one.