Pyridine-induced spectral changes

The pyridine-induced spectral changes were quantified in terms of Eq. (2). 

In 1974, Hush and Woolsey reported that treating the cobalt(II) corrole species discussed above with pyridine induced little in the way of spectral changes. These authors took this as an indication that the divalent cobalt corrole complex in question shows little or no tendency towards axial coordination. In 1978, however, Murakami, et al. reported a different result, stating that one pyridine molecule does in fact coordinate axially to the cobalt center of an anionic Co(II) corrole. 

Some spectral data, including PMR and UV, that have recently become available include the three examples cited below. In PMR experiments, when the solvent is changed from deuteriochloroform to the aromatic and anisotropic benzene-de or pyridine-dg which are capable of forming collision complexes, it is found that protons ortho to a phenolic hydroxyl show larger deshielding than protons in the meta or para positions. This phenomenon, commonly called aromatic solvent induced shifts (ASIS), has been used to locate the site of the phenolic function in the new alkaloid protothalipine found in Thalictrum rugosum Ait. (T. glaucum Desf.) (Ranunculaceae). ... 

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