Syntheses, structures, optical properties, and electronic structures of KBaMSe3 (MÂ =Â As, Sb)

KBaMSe3 (M = As, Sb) are isostructural and crystallize in the centrosymmetric monoclinic space group P21/c with zero-dimensional structures containing totally isolated MSe3 (M = As, Sb) pyramids with K+ and Ba2+ cations lying between them.