Structural, (Spectro)Electrochemical and Molecular Conductance Studies on Cyclic Diruthenium Complexes and Their Open Analogs

We report on four anchor-group modified diruthenium macrocycles obtained from two different bis(alkenyl)-diruthenium precursors and two dicarboxylate linkers by coordination-driven self-assembly. They were characterized using NMR spectroscopy and UHR ESI mass spectrometry, and, in the case of three metallamacrocycles, by single-crystal X-ray diffraction, and investigated via cyclic voltammetry. We also examined the mono- and doubly oxidized forms of the complexes using IR/NIR and UV/Vis/NIR spectroelectrochemistry as well as EPR spectroscopy. Additional insights into the structural and electronic properties of these compounds were gained through TD-DFT studies. Our studies are complimented by single molecule conductance measurements employing the scanning tunneling microscopy break-junction technique, and the results were compared with those obtained for monoruthenium complexes that represent one half of the macrocycles.