In the mixed crystal series of the cubic three-dimensional networks of composition [Zn1-xRux(bpy)3][NaCr(ox)3] (0e x e1, ox = C2O4 2-, bpy = 2,20-bipyridine), high-resolution absorption spectroscopy in the region of the 4A2f2E transition (R-lines) reveals the creation of five specific spectroscopic sites for the [Cr(ox)3]3- complex. The concentration of these spectroscopic sites follows a binomial distribution of [Zn(bpy)3]2þ and [Ru(bpy)3]2þ among the four nearest neighbors of a given [Cr(ox)3]3- complex within the network. The tris-bipyridine complexes occupying those positions have an optimal π-π interaction with the oxalate ligands of the tris-oxalate chromophore. The energy of each spectroscopic [Cr(ox)3]3- site depends on the total concentration of [Ru(bpy)3]2þ in the mixed crystal and on its specific distribution among the four nearest neighbors. Single crystal X-ray diffraction indicates a reduction of the unit cell volume when [Zn(bpy)3]2þ (a = 15.6365(18)A° ) is substituted by [Ru(bpy)3]2þ (a = 15.5098(6)A° ). This alone would lead to a red-shift of the R lines in analogy to the red-shift of 25.2 cm-1/GPa due to the decrease of the metal ligand Cr-O bond length as observed in high-pressure luminescence experiments. However, specific π-π interactions with the nearest neighbors have the opposite effect and shift the transition in discrete jumps to higher energies with increasing [Ru(bpy)3]2þ mole fraction.