Synthesis, structure and optical features of single adamantanoid Hg-SePh-X anionic clusters stabilized by octahedral complexes (Ph = phenyl; X = Cl, Br, I)

► Synthesis of six single adamantane like clusters stabilized by octahedral complexes. ► X-ray structural characterization of all compounds. ► Optical features and energy-gaps obtained graphically from UV-Vis absorption spectra.