The choice of ligands with different spacer length and coordination orientation leads to size, shape and packing differences between two self-assembled molecular squares [Zn4H8L14][PF6]5[NO3]3·S (1) and [Zn4H8L24][PF6]6[NO3]2·S (2) (S = solvent), formed from Zn(NO3)2 and two easy-to-prepare bistridentate Schiff-base ligands.