TY  - JOUR
A1  - Wacker, Philipp
A1  - Dahms, Katja
A1  - Senge, Mathias O.
A1  - Kleinpeter, Erich
T1  - Conformational Landscape of meso-(1,3-Dithian-2-yl)porphyrins
N2  - An investigation of the conformational landscape of 1,3-dithian-2-yl bearing porphyrins and the rotational behavior of the dithianyl substituents in meso position was carried out by variable-temperature (VT) NMR spectroscopy. Additionally, theoretical results for alternative conformations and energy barriers were obtained by molecular modeling. The study revealed different NH trans tautomers with regard to the orientation of the dithianyl ligands for the free base porphyrins 1-3. Relatively ruffled porphyrin core conformations were established for the transition states of the dithianyl rotation, resulting in a lower rotational energy barrier for the nickel(II) complex 4 compared to that of the free base systems. The data obtained and the first depiction of a rotational transition state for the rotation of bulky meso-alkyl substituents illustrate the close structural interplay between meso-alkyl substituents and the macrocycle conformation in porphyrins.
Y1  - 2007
UR  - http://pubs.acs.org/doi/full/10.1021/jo0708700
U6  - https://doi.org/10.1021/Jo0708700
ER  - 
TY  - JOUR
A1  - Wacker, Philipp
A1  - Kleinpeter, Erich
T1  - Stoichiometry, complex stability, molecular size and conformational variations of metal ion crown ether complexes subject to diffusion coefficients in nonaqueous solutions
N2  - Both the stoichiometry and complex stability constants of crown ether complexes with metal ions have been determined by examining gradual changes in their diffusional behavior in nonaqueous solution. Diffusion coefficients, D, were evaluated by pulsed field gradient (PFG) NMR titration experiments whilst complex stability constants were determined by nonlinear curve-fitting procedures, D versus csol., which also allow the treatment of multiple complexation equilibria (1:1 to 1:2 stoichiometries). Differences in the diffusion coefficients of the various free crown ethers with respect to their metal ion complexes indicate great sensitivity to both conformational changes and changes in molecular size upon complexation.
Y1  - 2007
UR  - http://www.springerlink.com/content/a584066q18q02857/
U6  - https://doi.org/10.1007/s10847-007-9332-1
ER  -