Composite Molecular Assemblies: Nanoscale Structural Control and Spectroelectrochemical Diversity

The controlled deposition of metal complexes from solution on inorganic surfaces offers access to functional materials that otherwise would be elusive. For such surface-confined interfaces to form, specific assembly sequences are often used. We show here that varying the assembly sequence of two well-defined and iso-structural osmium and ruthenium polypyridyl complexes results in interfaces with strikingly different spectroelectrochemical properties. Successivedeposition of redox-active layers of osmium and ruthenium polypyridyl complexes, leads to self-propagating molecular assemblies (SPMAs) with distinct internalinterfaces and individually addressable components. In contrast, the clearseparation of these interfaces upon sequential deposition of these two complexes, results in charge trapping or electrochemical communication between the metal centers, as a function of layer thickness and applied assembly sequence. TheSPMAs were characterized using a variety of techniques, including: UV−visspectroscopy, spectroscopic ellipsometry, electrochemistry, synchrotron X-ray reflectivity, angle-resolved X-ray photoelectronspectroscopy, and spectroelectrochemistry. The combined data demonstrate that the sequence-dependent assembly is a decisivefactor that influences and provides the material properties that are difficult to obtain otherwise.