We perform first principles density functional pseudopotential calculation for the description of band structure and optical responses a prototypical family of quasi-molecular layered solid of the type 3 AI where A  Sb,Bi and As. Our report on calculation of the anisotropic frequency-dependent optical properties and density of states of these compounds and find excellent agreement with the available experimental data. The optical properties show two main structures that can attributed to transitions between the np-orbitals of A3 - cations and 5s25p5 orbitals of I  -anions.