Ferrocene-based nanoelectronics: Design, synthesis, and evaluation

A new strategy for the construction of a ferrocene-based molecular diode is presented. The key design element is the asymmetric 2,5-diethynylpyridine bridging unit that serves to switch the system between two states. Synthetic methods for constructing a new structural class of organometallic compounds and the assembly of well-defined molecular assemblies are described.; Definitive proof that the 2,5-diethynylpyridyl bridge could serve as a viable switching element was provided by a study of the electrochemical properties of model representations of state 1 and state 2 of the proposed ferrocene-based molecular diode scheme. Model compounds 17 and 18 (state 1 and state 2, respectively), consisting of a 2,5-diethynyl pyridyl unit that linked two ferrocenes, were synthesized. Electrochemical evidence revealed a single two-electron redox couple for the two ferrocenes in model compound 17 (state 1), and two one-electron redox couples for the two ferrocenes in model compound 18 (state 2) with a Δ E_1/2 of 161 mV.; A general method for the synthesis of hetero-disubstituted 1,1 ′-diethynyl ferrocene derivatives based on the key building block, 1-iodo-1′-ethynylferrocene (35), was demonstrated. The syntheses of the target diferrocene dithioacetates, 31 and 32, were achieved. In addition, the syntheses of the diferrocene monothioacetates, 33/59 and 34/63, were accomplished for the purpose of modifying gold electrode surfaces and determining relative rates of ET through these organometallic-based assemblies.; The diferrocene monothiol derivatives 78 and 79 were selectively and covalently attached to Au(111) electrodes. Electrochemical studies of the well-defined electroactive SAMs 86–89 , composed of the diferrocene monothiol derivatives 78 and 79, qualitatively determined that electron transport at a SAM with a ferrocene-pyridinium cation-ferrocene-thiol linked molecule was efficient. However, information regarding the stability of these SAMs in a 1.0 M HClO₄ supporting electrolyte solution suggested that the analytical AC voltammetry technique was not adequate for quantitative electrochemical characterization of ET rates in the molecular assemblies 87 and 89.