The electronic absorption spectra (UV-visible-NIR) of a range of molec
ular metal cluster compounds, including new spectra of Pt309(phen)36O
28 in solution and Au55(PPh3)12Cl6 in the solid state, are discussed a
nd compared with the spectra of colloidal particles of the correspondi
ng metals. We consider frontier orbital separations, the development o
f 'interband' absorptions, the possible appearance of molecular plasma
resonances, and charge-transfer in the solid state.