Ruthenium Carbon-Rich Group as a Redox-Switchable Metal Coupling Unit in Linear Trinuclear Complexes

The preparation and properties of novel ruthenium carbon-rich complexes [(Ph–CC−)_2–<i>n</i>Ru­(dppe)₂(−CC-bipyM­(hfac)₂)_<i>n</i>] (<i>n</i> = 1, 2; M = Cu^II, Mn^II; bipy = 2,2′-bipyridin-5-yl) characterized by single-crystal X-ray diffraction and designed for molecular magnetism are reported. With the help of EPR spectroscopy, we show that the neutral ruthenium system sets up a magnetic coupling between two remote paramagnetic Cu^II units. More specifically, these copper compounds are unique examples of bimetallic and linear heterotrimetallic compounds for which a complete rationalization of the magnetic interactions could be made for exceptionally long distances between the spin carriers (8.3 Å between adjacent Cu and Ru centers, 16.6 Å between external Cu centers) and compared at two different redox states. Surprisingly, oxidation of the ruthenium redox-active metal coupling unit (MCU), which introduces an additional spin unit on the carbon-rich part, leads to weaker magnetic interactions. In contrast, in the simpler parent complexes bearing only one paramagnetic metal unit [Ph–CC–Ru­(dppe)₂-CC–bipyCu­(hfac)₂], one-electron oxidation of the ruthenium bis­(acetylide) unit generates an interaction between the Cu and Ru spin carriers of magnitude comparable to that observed between the two far apart Cu ions in the above corresponding neutral trimetallic system. Evaluation and rationalization of this coupling with theoretical tools are in rational agreement with experiments for such complex systems

Inexpensive and Efficient Ullmann Methodology To Prepare Donor-Substituted Porphyrins

The preparation of porphyrins functionalized with one or two carbazoles (or phenoxazines) is described. The electron donors were introduced into one or two porphyrin <i>meso</i> positions by using the inexpensive Ullmann coupling procedure. Very good yields were obtained, and for two new compounds, the X-ray structures were solved. Preliminary electrochemical data coupled with electronic spectroscopy are also reported