We theoretically study optical excitations in K-4[Pt-2(pop)(4)X-2] monomers (X=Cl, Br, I), using an extended Hubbard model. We show that long-range transfer integrals and long-range Coulomb interactions are substantially large to reproduce the experimental results, and discuss effects of long-range Coulomb interactions on the electronic phases and the optical conductivity spectra of the MMX chains.