Narrow Results

Chromyl(V) complexes of eleven different meso-aryl- and $\beta$-alkylcorrole ligands have been prepared and characterized by analytical, spectroscopical, electrochemical and structural means. All seven new complexes show the expected optical spectra of chromyl(V) corroles with the Soret band situated slightly above (meso-arylcorroles) or below ($\beta$-alkylcorrole) 400 nm, and with an isotropic room temperature EPR signal for the $d^1$ ion Cr(V) at about $g_{\mathrm{\text{iso}}}=1.985$. Cyclic voltammetry evidences two or three quasi-reversible one-electron redox steps, which are characterized as two ligand-centered processes and one metal-centered process based on spectroelectrochemical measurements and a Hammett analysis. Chemical reduction to a chromyl(IV) corrolate was successfully performed using NaHg and NEt₃. Citric acid, however, produces a different reduction product, for which an isocorrole structure is proposed. Six chromyl(V) corroles could be analysed by seven single crystal diffraction analyses. The obtained molecular data prove the presence of remarkably similar CrN₄O coordination units independent of the corrole substitution pattern, and of macrocyclic conformations which can be understood as comprised mainly of a doming mode, a more or less pronounced saddling mode, and one out of two different and dominating ruffling modes.

Manganese corroles with the Mn atom in the oxidation states +III and +IV have been probed as donor moieties for supramolecular stacked donor–acceptor complexes with the typical acceptor units TCNQ (tetracyanoquinone), TCNP (tetracyanopyrazine), and TCNB (tetracyanobenzene). Four new compounds formed as single crystals from different co-crystallization attempts. In those cases where a Mn(III) corrole was used as the donor component, hydrolyzed and/or oxygenated compounds [(cor)Mn(TCNQ*)] and [(cor*)Mn(TCNP*)] were obtained as the exclusive products. With chloridomanganese(IV) corroles, sandwich-like 2:1 complexes [(cor)MnCl]${}_{\mathrm{\text{2}}}$[TCNQ] and [(cor)MnCl]${}_{\mathrm{\text{2}}}$[TCNB] form, with both components left intact. Crystallographic analyses reveal partial or complete charge transfer to unusual axial ligands and thus prove the high reactivity of Mn(III) corroles in the first two cases. For the sandwich arrangements, almost-unaltered geometric parameters of the Mn(IV) corroles are observed, pointing to negligible structural consequences for metal corroles when engaged in stacking interactions.