2000
DOI: 10.1021/ic9907866
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Electronic Effects in Transition Metal Porphyrins. 10. Effect of Ortho Substituents on the Temperature Dependence of the NMR Spectra of a Series of Spin-Admixed Perchloratoiron(III) Tetrakis(2,6- or 2,4,6-phenyl substituted)porphyrinates

Abstract: The perchloratoiron(III) complexes of a series of 2,6-disubstituted tetraphenylporphyrin ligands, where the 2,6-phenyl substituents were -H, -F, -Cl, -Br, or -OMe, as well as two 2,4,6-phenyl-substituted complexes, where the substituents were -Me and -OMe, have been investigated as a function of temperature by 1H NMR spectroscopy. Curvature in the 1/T dependence was evident in most cases. Forced linear extrapolation of the temperature dependence observed over the range of the study yielded Curie plots that inc… Show more

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Cited by 39 publications
(58 citation statements)
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“…These shift downfield when the temperature decreases but still lie in the intermediatespin state range. [(F 8 )Fe III ]ClO 4 exhibits ÎŽ pyrrole = ~15 ppm at RT) 74. In THF- d 8 , signals for both high-spin (ÎŽ pyrrole = 54.7 at RT) and intermediate spin (ÎŽ pyrrole = 14.8 at RT) are observed at all temperatures (Figure 10).…”
Section: Resultsmentioning
confidence: 93%
See 1 more Smart Citation
“…These shift downfield when the temperature decreases but still lie in the intermediatespin state range. [(F 8 )Fe III ]ClO 4 exhibits ÎŽ pyrrole = ~15 ppm at RT) 74. In THF- d 8 , signals for both high-spin (ÎŽ pyrrole = 54.7 at RT) and intermediate spin (ÎŽ pyrrole = 14.8 at RT) are observed at all temperatures (Figure 10).…”
Section: Resultsmentioning
confidence: 93%
“…Walker and co-workers74 have in fact previously studied [(F8)Fe III ]ClO 4 ; in CH 2 Cl 2 , this was shown to be an S = 3/2 and S = 5/2 spin admixture; the ground state was largely high-spin with the S = 3/2 state as the first excited state, based on EPR (4.2K) and NMR (CD 2 Cl 2 ) spectroscopic properties. Here, we compare these properties with our own [(F 8 )Fe III ]SbF 6 in CH2Cl 2 .…”
Section: Resultsmentioning
confidence: 99%
“…This is consistent with intermediate-spin iron(iii), since all resonances are expected at low field for pure high-spin iron(iii), while the reverse holds for low-spin complexes. [21] The EPR spectrum of 5 a with g 3.8 (Figure 1c, observable at RT in the solid state and in frozen solutions) also supports this conclusion, as may be deduced from the extensive work with iron(iii) porphyrins (high-spin: g c % 6, g k % 2, intermediate-spin: g c % 4, low-spin: g z b 2, g y % 2, g x`2 ). [22] Finally, the 19 F NMR spectrum shown in Figure 1b displays three sets of resonances, all in a 2:1 ratio due to the different magnetic environment of the central C 6 F 5 ring relative to the two other.…”
Section: Resultsmentioning
confidence: 99%
“…According to Mitra et al ., the Maltempo model explains only the gross magnetic behavior of the complexes and mixing with low-lying excited spin states ( 4 E, 2 E, 2 B 2 ) should also be considered. As shown diagrammatically by Figure , the relative contributions of S = 3 / 2 and S = 5 / 2 states to the ground state of spin-admixed systems varies depending upon the energy of the d( x 2 − y 2 ) orbital. As the energy of this orbital increases, the ground state will change from predominantly S = 5 / 2 to predominantly S = 3 / 2 …”
Section: 11 Theoretical Basis For the S = 3/25/2 Quantum Mechanical S...mentioning
confidence: 99%