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Major advances over the last few years have facilitated the synthesis of a large variety of meso-only substituted corroles that display interesting catalytic, therapeutic and photophysical properties. This work is the first to study extensively the NMR spectral characteristics of both metallated and non-metallated triarylcorroles in various organic solvents and provide guidelines for easy and reliable assignments of 1D 1H spectra from trends of J coupling constants and chemical shifts. An excellent correlation is found between C=C bond lengths derived from 3J(H,H) values and experimental lengths determined by x-ray crystallography of the same molecules. The nuclear Overhauser effect provides a robust 1D 1H NMR tool for determining the selectivity of electrophilic substitutions. Variable-temperature NMR and isotopic labelling reveal a single preferred tautomerization state and unsymmetric ring orientations at -70 degrees C. The beta-pyrrole protons demonstrate long-range heteronuclear couplings with the coordination core (15N) and with the ortho-19F nuclei of the meso-carbon aryl rings. In sum, application of multinuclear magnetic resonance to corroles and their metal complexes, through the compilation of chemical shifts and J couplings and the recognition of trends therein, provides basic information essential to reliable spectral assignments. Additionally, the conclusions drawn about the structures of corroles and the electron densities at various positions of the corrole macrocycle resulting from the application of high-resolution NMR techniques are of importance to an in-depth understanding of the molecular interactions and processes of this relatively new and rapidly expanding class of compounds.

First published as an Advance Article on the webThe X-ray structure, magnetic susceptibility, and high-field (high-frequency) EPR spectrum of manganese 5,10,15-tris-(pentafluorophenyl) corrole unambiguously establish that the complex contains an isolated, slightly rhombic, manganese(III) center.Manganese(III) porphyrins are very efficient catalysts for functionalization of hydrocarbons in processes that involve high valent intermediates. 1,2 Spectroscopic identification of odd-spin manganese(IV) and spin-coupled manganese(V) porphyrins by magnetic resonance measurements is relatively straightforward, via utilization of EPR and NMR, respectively. 3-6 However, even-spin manganese(III) porphyrins are EPR-silent (X-band) and their NMR spectra are not easily interpretable. For example, an early assignment of the origin of the paramagnetic shifts in manganese(III) porphyrins was recently revised, 7 and there is some evidence indicating that the complexes might better be described as manganese(II) porphyrin radical cations. 8 A recent development relevant to this question is the utilization of highfield (high-frequency) EPR (HF-EPR) spectroscopy for elucidation of the electronic structures of high-spin manganese(III) complexes. 9 The close relationship of porphyrins and corroles suggests that metallocorroles could also be very interesting catalysts. This proposal was only recently explored, taking advantage of the novel electron-poor 5,10,15-tris(pentafluorophenyl)corrole, H 3 tpfc, 10 whose substitution pattern matches that of the most active porphyrin-based catalysts. First, it was demonstrated that the iron and rhodium complexes of H 3 tpfc are potent catalysts for oxygen and carbene transfer to olefins and alkanes, 11 followed by full characterization of H 3 tpfc 12 and its Cr V O, Fe IV Cl and Rh III (PPh 3 ) complexes. 13,14 The manganese corrole [(tpfc)Mn] was also found to be an epoxidation catalyst, as well as an excellent precursor to a relatively stable oxomanganese(V) corrole. 1b,15 The apparent importance of this result together with the rather limited information on the electronic structures of manganese corroles 16,17 were the driving forces for the current investigations. A combination of HF-EPR spectroscopy, X-ray crystallography, and magnetic susceptibility measurements, led to the conclusion that [(tpfc)Mn(OPPh 3 )] is an authentic manganese(III) complex that does not experience significant intermolecular interactions.Obtaining X-ray quality crystals of [(tpfc)Mn] was a difficult task; NMR examination of material from different crystallization batches revealed significant variations in chemical shifts. Since we suspected that these differences were due to solvent coordination, we added external ligands to the recrystallization mixtures. These attempts finally met with success: with triphenylphosphine oxide as additive, X-ray quality crystals of [(tpfc)Mn(OPPh 3 )] were isolated. 18 The structure of [(tpfc)Mn(OPPh 3 )] (Fig. 1) is quite different from that of the previously reported square planar ma...

The investigations of complete nitrogen atom transfer reactions from (nitrido)manganese(V) salen to manganese(III) complexes of porphyrins and corroles revealed that stabilization of the [Mn(N)]2+ moiety is in the order of corrole > porphyrin > salen. The first kinetic examination of this quite fundamental reaction exposed a large solvent effect on both the enthalpy and entropy activation energies. Oxidation of the (nitrido)manganese(V) corroles leads to the first (nitrido)manganese(VI) complexes that are coordinated by tetrapyrrolic ligands.