  We perform first-principles calculations of electronic and dielectric
properties of bismuthene functionalized with small ligands using
first-principle calculations. We show that all functionalized structures have
topological insulating (TI) behavior with a sizeable gap by calculating the
Z$_2$ topological invariant. Furthermore the adsorption of all groups induce a
quasi-planar structure to the initially pristine bismuthene structure. Finally
we show that the dielectric properties show a large anisotropy with two main in
plane absorption peaks.
