1H NMR Conformational Study of Viologen-Linked Porphyrins

Novel porphyrins to which the viologen is linked (m-PCnV) were synthesized. The linkage methylene chain between the porphyrin and the bipyridine moieties was systematically changed from (CH2)3 to (CH2)6. The molecular structure of m-PCnV was characterized by 1H NMR in some detail. The orientation of the viologen with respect to the porphyrin plane in m-PCnV was semiquantitatively estimated from the porphyrin ring current induced chemical shift changes on the resonances from the viologen moiety. The NMR conformational analyses on m-PCnV in dimethyl sulfoxide and acetonitrile clearly revealed the effect of the solvent on its molecular structure.