Influence of the core conformation on the NH-tautomerism in porphyrins: a study of meso-(1,3-dithian-2-yl)porphyrins |
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Authors: | Wacker Philipp Dahms Katja Senge Mathias O Kleinpeter Erich |
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Affiliation: | Institut für Chemie, Universit?t Potsdam, Karl-Liebknecht-Strasse 24-25, D-14476 Golm, Germany. |
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Abstract: | In order to investigate the mechanism of the NH-tautomerism in porphyrins, three meso-dithianyl-substituted porphyrins of different substitution pattern were studied theoretically. The corresponding trans-, cis- and saddle-point geometries were optimized with DFT methods, and the macrocyclic conformations obtained were analyzed using normal-structure-decomposition (NSD) analysis. Special attention was given to the influence of the participating out-of-plane and in-plane conformations on the NH-tautomerism, and the interplay of substituents, core conformations and energies of the transition-state structures was critically evaluated. The calculated energy barriers of the preferred pathways are compared with experimental activation enthalpies determined by variable-temperature (VT) NMR spectroscopy. |
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