Sequential assembly of layers containing redox-active dinuclear Ru complexes that differ in their redox potential on ITO substrates afforded a series of layered structures with different potential gradients. The Ru complexes Ru-NP and Ru-CP contain tetrapodal phosphonate anchors and bridging 2,3,5,6-tetra(2-pyridyl)pyrazine or 1,2,4,5-tetra(2-pyridyl)benzene ligands, respectively. Oxidation potentials of E-1/2 2 = +0.83 and +1.04 V vs. Fe+/Fc (Ru-NP) and E-1/2 = 0.37 and 0.09 V (Ru-CP) were observed for the Ru(II)Ru(II)/Ru(II)-Ru(III) and Ru(II)-Ru(III)/Ru(III)-Ru(III) couples. As the Ru-NP and Ru-CP units contain several accessible redox-active electronic states, electron transfer (ET) blockage and mediation occurred at the Ru-NP/Ru-CP heterojunction on account of the large potential gradient. An examination of the electrochemical behavior of the multilayer diblock parallel to TO parallel to(Ru-CP) 1(Ru-NP) (n = 1-5) heterofilms revealed that in ITOII(Ru-CP)41(Ru-NP)4, the Ru(III)-Ru(III)/Ru(III)-Ru(IV) couple is involved in the electron mediation pathway on the Ru-NP/Ru-CP heterojunction. In the case of the multilayer triblock IT011(RuNP) 1(Ru-CP) 1(Ru-NP) (n = 4) heterofilms, two catalytic peaks were observed, indicating that the inner and outer Ru-NP/Ru-CP junctions display two different catalytic ET processes. In the alternating Ru-NP/Ru-CP multilayer heterofilms, the ET mediation processes are governed by the sequence order of the RuNP/Ru-CP heterojunction attached to the ITO electrode. In multilayer homo- and heterofilms, the dependence of the ET distance on the layer number is discussed on the basis of potential -step chronoamperometry (PSCA) results. In the multilayer Ru-NP and Ru-CP homofilms, relatively low 13 values were observed, while in the multilayer heterofilms, the ET rate of the catalytic wave was not affected by the number of layers, as the energy gap between the Ru-NP/Ru-CP units is the rate determining factor. Therefore, the molecular sequence in such multilayer heterofilms, composed of layers containing Ru-NP or Ru-CP complexes, plays an important role. (C) 2016 Elsevier Ltd. All rights reserved.