Positive Constructs: Charges Localized on Surface-Confined Organometallic Oligomers

Assemblies with molecular-level organization based on organic chromophores and a bimetallic palladium complex are presented. A layer-by-layer strategy is employed by alternately coordinating vinylpyridine-terminated chromophores to the metal centers to form cationic oligomers. These new structures are formed from solution on quartz and silicon substrates functionalized with a covalently bound template layer. Twelve consecutive deposition steps result in structurally regular assemblies as demonstrated by linear increases in the ellipsometrically determined thickness and UV-vis optical absorption. The increase in thickness for each additional layer shows that the long-range order of the system is determined by the structure of the chromophores and by the square-planar geometry of the metal centers. Furthermore, the optical properties indicate that the conjugation length of the assembly component does not increase in the surface-bound oligomers with each additional deposition cycle. Structural communication is transferred via the system components, but they remain electronically isolated. This is supported by density functional theory (DFT) calculations.