A. Medek et al., CO-59 NMR-STUDIES OF DIAMAGNETIC PORPHYRIN COMPLEXES IN THE SOLID-PHASE, JOURNAL OF PHYSICAL CHEMISTRY B, 101(44), 1997, pp. 8959-8966
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.