A conjugated diosma-octacyclic complex and its mixed-valence singly reduced state

In this work two dicationic diosma-octacyclic complexes have successfully been synthesized and fully characterized. One of them, with aromatic osmapentalene termini linked by the non-aromatic osmafuran moiety to the rigid naphthalenediolate bridge, represents the first example of a fused, fully conjugated dimetalla-octacyclic complex. A reference complex with more flexible biphenolate in the bridging position was also prepared. Their redox and electronic properties were investigated by combined methods of cyclic voltammetry and UV-vis-NIR–IR spectroelectrochemistry, supported by density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations. The rigid octacyclic complex forms a stable singly reduced mixed-valence species with the spin density localized at one of the osmapentalene termini