The spectroscopic and chemical behavior of the six-coordinate adducts formed by the association of chloro-meso-tetraphenylporphinatochromium(III), Cr(TPP)(CI), and neutral oxygen, sulfur, and nitrogen donor ligands in nonaqueous solutions is described. In nonaqueous media, in the presence of a neutral ligand, Cr(TPP)(CI) forms six-coordinate adducts of the type Cr(TPP)(CI)(L) and Cr(TPP)(CI)(B), where L and B denote neutral N-donor and 0-or S-donor ligands, respectively. This behavior is confirmed by visible spectroscopy, spectrophotometric titrations, and conductivity data. Equilibrium constants for the substitution reaction Cr(TPP)(Cl)(B) + L + Cr(TPP)(CI)(L) + B are reported. The N-donor ligands are found to bind much more strongly to the Cr(II1) center than the 0-or S-donors. The replacement of acetone by 1 -methylimidazole in the complex Cr(TPP)(Cl)(acetone) in 60% acetone/toluene (v/v) at 25 OC occurs with an equilibrium constant of 4.0 X IO6. Fitting the EPR spectra of the six-coordinate adducts obtained from frozen solutions at 78 K to the spin Hamiltonian H = Pe[gxHxSx + gVH,S, + g,H,S,] + D[S,* -5/4] + E[Sx2 -Sy2], and using an assumed isotropic value for g of 1.995, results in values for ID1 in the range 0.156 f 0.012 cm-' for complexes of the type Cr(TPP)(Cl)(L) and values in the range 0.232 f 0.004 cm-' for the complexes of the type Cr(TPP)(CI)(B). The only observed exception was the CH3CN adduct forwhich a value of 0.208 cm-l was obtained. In all cases ( E ( was found to be small, having a maximum value of 0.013 cm-I for the complex Cr(TPP)(Cl)(acetone). The Cr(octaethy1porphyrin) complexes behave similarly.
The authors reviewed 1 year of experience with planar and single photon emission computed tomographic (SPECT) bone scintigraphy in 162 young patients with symptoms of low-back pain possibly related to stress injury to the pars interarticularis or spondylolysis. Planar scintigraphy and SPECT revealed no abnormality in 91 patients (56%). All abnormalities detected on planar images were also detectable with SPECT. SPECT showed an abnormal focus of radiotracer uptake in the lumbar spine in 71 patients (44%). In 32 of these 71 patients, these findings were also evident with planar scintigraphy. In 39 of these 71 patients, use of SPECT. Correlation with contemporaneous radiographs was made in 72 cases (including computed tomography in 10 cases). SPECT can be used to detect stress injury not seen with planar bone imaging or radiography and is recommended in evaluation of low-back pain in young athletes.
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