Trimeric perfluoro-ortho-phenylene mercury(II) cluster is a prototypical example of a macrocyclic multidentate Lewis acid. In this study we report the electronic structure, the calculated absorption and vibrational spectra via all-electron scalar and spin-orbit relativistic DFT calculations for [Hg(o-C6H4)](3) (1), [Hg(o-C6F4)](3) (2), and the dimeric form of 2, ([Hg(O-C6F4)](3))(2) (3). Due to the inclusion of the spin-orbit interaction, double point groups were used (D-3h* and D-3d*). The calculations suggest small paratropic ring currents at the center of 1 and being smaller for 2 due to the withdrawn properties of the perfluorated ligand. The luminescent properties of the solid state of 2 are well represented by the postulated model of dimer 3, which mimic the solid state, where the proposed mechanism involves a vibronically coupled emission process. The calculated lambda(max)(absorption) of 3 show an intense peak at 347 mn, which compares well with the reported band at 355 nm; also, the calculated lambda(emission) = 431 nm is close to the experimental value of 440 nm. Moreover, the calculated structural changes of the first excited state (3*) are reflected in the large value of the calculated Stoke shifts of 84 nm, which is in quite good agreement with the value of 85 nm extracted from the experimental data.