Oxidation and Oxygenation of Carbonyl Ruthenium(II) Azuliporphyrin

Chemical oxidation and oxygenation of carbonyl ruthenium­(II) azuliporphyrin [Ru­(TPAP)­(CO)] were explored. [Ru­(TPAP)­(CO)] reacts with dioxygen giving carbonyl ruthenium­(II) 21-oxyazuliporphyrin [Ru­(TPAP-O)­(CO)] revealing the activation the Ru–C bond inside azuliporphyrin coordination cavity. Solution and X-ray structural studies confirmed the tendency of [Ru­(TPAP-O)­(CO)] to form dimeric [Ru­(TPAP-O)­(CO)]₂. The dimer adopts a head-to-tail structure with the azulenolate groups forming bridges from one macrocycle to the ruthenium­(II) in the adjacent unit. One-electron oxidation of [Ru­(TPAP)­(CO)] gives the first π-cation radical of metallo­carbaporphyrinoid[Ru­(TPAP)­(CO)]^+•with extraordinary participation of the azulene unit in the spin delocalization. The most characteristic ¹H NMR features of the radical are large, sign-alternating isotropic shifts of resonances assigned to <i>meso</i>-aryl, azulene, and pyrrolic hydrogen atoms. The spin distribution determined by density functional theory confirmed the π-cation radical electronic structure reproducing the diagnostic spectroscopic features including π-delocalization at <i>meso</i>-aryl resonances and very characteristic sign alternation of contact shifts for an azulene moiety