MPI für bioanorganische Chemie / MPI für bioanorganische Chemie |
|Möbius-Hückel topology switching in an expanded porphyrin cation radical as studied by EPR and ENDOR spectroscopy|
|Authors:||Möbius, Klaus; Plato, Martin; Klihm, Gudrun; Laurich, Christoph; Savitsky, Anton; Lubitz, Wolfgang; Szyszko, Bartosz; Stepien, Marcin; Latos-Grazynski, Lechoslaw|
|Date of Publication (YYYY-MM-DD):||2015|
|Title of Journal:||Physical Chemistry Chemical Physics|
|Issue / Number:||9|
|Review Status:||Internal review|
|Abstract / Description:||The symmetry of the arrangement of objects has fascinated philosophers, artists and scientists for a long time, and still does. Symmetries often exist in nature, but are also created artificially, for instance by chemical synthesis of novel molecules and materials. The one-sided, non-orientable Mobius band topology is a paradigm of such a symmetry-based fascination. In the early 1960s, in synthetic organic chemistry the interest in molecules with Mobius symmetry was greatly stimulated by a short paper by Edgar Heilbronner. He predicted that sufficiently large [n]annulenes with a closed-shell electron configuration of 4n pi-electrons should allow for sufficient pi-overlap stabilization to be synthesizable by twisting them with a 1801 phase change into the Mobius symmetry of their hydrocarbon skeleton. In 2007, the group of Lechoslaw Latos-Grazynski succeeded in synthesizing the compound di-p-benzihexa-phyrin(220.127.116.11.1.1), compound 1, which can dynamically switch between Huckel and Mobius conjugation depending, in a complex manner, on the polarity and temperature of the surrounding solvent. This discovery of "topology switching'' between the two-sided (Huckel) and one-sided (Mobius) molecular state with closed-shell electronic configuration was based primarily on the results of NMR spectroscopy and DFT calculations. The present EPR and ENDOR work on the radical cation state of compound 1 is the first study of a ground-state open-shell system which exhibits a Huckel-Mobius topology switch that is controlled by temperature, like in the case of the closed-shell precursor. The unpaired electron interacting with magnetic nuclei in the molecule is used as a sensitive probe for the electronic structure and its symmetry properties. For a Huckel conformer with its higher symmetry, we expect - and observe - fewer ENDOR lines than for a Mobius conformer. The ENDOR results are supplemented by and in accordance with theoretical calculations based on density functional theory at the ORCA level.|
|Comment of the Author/Creator:||Date: 2015, 2015|
|External Publication Status:||published|
|Version Comment:||Automatic journal name synchronization|
|Communicated by:||N. N.|
|Affiliations:||MPI für bioanorganische Chemie|
|External Affiliations:||[Möbius,K.; Plato,M.;] Free Univ.Berlin, Fachbereich Phys., D-14195 Berlin, Germany.
[Szyszko,B.; Stepien,M.; Latos-Grazynski,L.] Uniwersytet Wroclawski, Wydzial Chem., PL-50383 Wroclaw, Poland.
|Identifiers:||ISI:000351435300055 [ID No:1] |
ISSN:1463-9076 [ID No:2]
DOI:10.1039/C4CP05745G [ID No:3]
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