In conclusion, following the "building block" strategy using metallocyanate building block and monodentate ligand, we have successfully synthesized Cr III -Mn II two-dimensional network which on extension along b-axis forms a "stair" system. Detailed theoretical analysis revealed that considerable antiferromagnetic exchange among Mn(II) and Cr(III) ions mediated by cyanido ligands leads to large magnetic moments of 1D ladder-like units at lower temperatures due to topology of the exchange coupling.