CO-59 NMR-STUDIES OF DIAMAGNETIC PORPHYRIN COMPLEXES IN THE SOLID-PHASE

Solid state Co-59 nuclear magnetic resonance (NMR) spectra were record ed on diamagnetic complexes with general structure Co(Por)L-2, where P or = tetraphenylporphyrin, tetramethoxyphenylporphyrin, and octaethylp orphyrin; and L = imidazole, methylimidazole, pyridine, and isoquinoli ne. Measurements were carried out at different magnetic field strength s (4.7, 7.1, and 11.7 T) on both static and spinning samples. Iterativ e fitting of these data yielded the shielding and quadrupolar paramete rs that characterize the various cobalt(III) sites in the complexes. T hese results are only in partial agreement with data inferred from pre vious solution NMR measurements. The values measured for the anisotrop ic components of the Co-59 NMR tensors also deviate from traditional c orrelations observed for simpler nonaromatic solid cobalt complexes. P ossible sources for the discrepancies observed between the solution an d the solid phase parameters as well as for the anomalous behavior obs erved with the anisotropic Co-59 coupling constants are discussed.