Electrochemical, spectroelectrochemical and X-ray absorption spectroscopic study of some iron(II) and iron(III) polypyrazolylborato complexes

A Synthetic, Structural, Magnetic, and Spectral Study of Several {Fe[tris(pyrazolyl)methane]2}(BF4)2Complexes: Observation of an Unusual Spin-State Crossover

“…The 295 and 78 K X-ray absorption near-edge structure spectra, the XANES spectra, of 2 and 1 are shown in parts a and b, respectively, of Figure . This figure also shows the changes in the absorption which occur upon cooling from 295 to 78 K. The spectra of 2 are very similar to those reported , for Fe[HB(pz) 3 ] 2 , and the conventional labels have been used for the different observed peaks, whose energies and intensities are given in Table . The position and shape of the edge jump are identical for both complexes, but the shape of absorption C is broader in Fe[HB(pz) 3 ] 2 than in 2 , and its intensity is higher at 295 K. Further, in 2 an additional absorption line is observed between lines C and D at 78 K. As expected, because 2 is LS at both 295 and 78 K, there is little change in its spectrum upon cooling, and the assignments of the different bands are essentially identical to that discussed 26 for Fe[HB(pz) 3 ] 2 .…”

A Synthetic, Structural, Magnetic, and Spectral Study of Several {Fe[tris(pyrazolyl)methane]2}(BF4)2Complexes: Observation of an Unusual Spin-State Crossover

“…The 295 and 78 K X-ray absorption near-edge structure spectra, the XANES spectra, of 2 and 1 are shown in parts a and b, respectively, of Figure . This figure also shows the changes in the absorption which occur upon cooling from 295 to 78 K. The spectra of 2 are very similar to those reported , for Fe[HB(pz) 3 ] 2 , and the conventional labels have been used for the different observed peaks, whose energies and intensities are given in Table . The position and shape of the edge jump are identical for both complexes, but the shape of absorption C is broader in Fe[HB(pz) 3 ] 2 than in 2 , and its intensity is higher at 295 K. Further, in 2 an additional absorption line is observed between lines C and D at 78 K. As expected, because 2 is LS at both 295 and 78 K, there is little change in its spectrum upon cooling, and the assignments of the different bands are essentially identical to that discussed 26 for Fe[HB(pz) 3 ] 2 .…”

X-ray Absorption Spectroscopic Study of the Temperature and Pressure Dependence of the Electronic Spin States in Several Iron(II) and Cobalt(II) Tris(pyrazolyl)borate Complexes

“…Rather strangely, Zamponi et al do not observe the shoulder, B, in the spectrum of 2 but do observe it in the spectrum of 1 and, in spite of its high intensity, assign this shoulder to the forbidden 1s to 3d transition, an assignment we cannot accept, especially in the view of the presence of the pre-edge peak, P, in all of our spectra and in the spectra of Zamponi et al …”

“…The relative energies and normalized intensities of the XANES absorptions are given in Table 1. The XANES spectra of 1 and 2 were reported very recently by Zamponi et al, 30 but as will be noted below, there are small differences between their spectra and the spectra reported herein, differences which probably are due to differences in resolution. Further, as will be discussed below, we make assignments completely different from those proposed by Zamponi et al 30 The interpretation of the edge structure in the XANES spectra is not simple, and a detailed analysis of the absorption profiles shown in Figure 1 requires a complete multiple-scattering analysis, which will be given in a future paper.…”

“…The XANES spectra of 1 and 2 were reported very recently by Zamponi et al, 30 but as will be noted below, there are small differences between their spectra and the spectra reported herein, differences which probably are due to differences in resolution. Further, as will be discussed below, we make assignments completely different from those proposed by Zamponi et al 30 The interpretation of the edge structure in the XANES spectra is not simple, and a detailed analysis of the absorption profiles shown in Figure 1 requires a complete multiple-scattering analysis, which will be given in a future paper. 31 However, in conjunction with the known structures of the compounds, firstapproximation assignments of the absorption peaks below or in the rising edge can be made with a one-electron model based on electronic dipole transitions.…”

“…The XANES spectra of 1 and 2 were reported very recently by Zamponi et al., but as will be noted below, there are small differences between their spectra and the spectra reported herein, differences which probably are due to differences in resolution. Further, as will be discussed below, we make assignments completely different from those proposed by Zamponi et al

1 XANES spectra of Fe[HB(pz) 3 ] 2 , 1 , Fe[HB(3,5-(CH 3 ) 2 pz) 3 ] 2 , 2 , Fe[HB(3,4,5-(CH 3 ) 3 pz) 3 ] 2 , 3 , and Co[HB(pz) 3 ] 2 , 4 , measured at 450, 295, or 77 K, as indicated. The zero of the energy scale is given relative to 7112 and 7709 eV, the K-edges of iron and cobalt foil, respectively.

…”

A Synthetic, Structural, Magnetic, and Spectral Study of Several {Fe[tris(pyrazolyl)methane]2}(BF4)2Complexes: Observation of an Unusual Spin-State Crossover

“…The 295 and 78 K X-ray absorption near-edge structure spectra, the XANES spectra, of 2 and 1 are shown in parts a and b, respectively, of Figure . This figure also shows the changes in the absorption which occur upon cooling from 295 to 78 K. The spectra of 2 are very similar to those reported , for Fe[HB(pz) 3 ] 2 , and the conventional labels have been used for the different observed peaks, whose energies and intensities are given in Table . The position and shape of the edge jump are identical for both complexes, but the shape of absorption C is broader in Fe[HB(pz) 3 ] 2 than in 2 , and its intensity is higher at 295 K. Further, in 2 an additional absorption line is observed between lines C and D at 78 K. As expected, because 2 is LS at both 295 and 78 K, there is little change in its spectrum upon cooling, and the assignments of the different bands are essentially identical to that discussed 26 for Fe[HB(pz) 3 ] 2 .…”

X-ray Absorption Spectroscopic Study of the Temperature and Pressure Dependence of the Electronic Spin States in Several Iron(II) and Cobalt(II) Tris(pyrazolyl)borate Complexes

“…Rather strangely, Zamponi et al do not observe the shoulder, B, in the spectrum of 2 but do observe it in the spectrum of 1 and, in spite of its high intensity, assign this shoulder to the forbidden 1s to 3d transition, an assignment we cannot accept, especially in the view of the presence of the pre-edge peak, P, in all of our spectra and in the spectra of Zamponi et al …”

“…The relative energies and normalized intensities of the XANES absorptions are given in Table 1. The XANES spectra of 1 and 2 were reported very recently by Zamponi et al, 30 but as will be noted below, there are small differences between their spectra and the spectra reported herein, differences which probably are due to differences in resolution. Further, as will be discussed below, we make assignments completely different from those proposed by Zamponi et al 30 The interpretation of the edge structure in the XANES spectra is not simple, and a detailed analysis of the absorption profiles shown in Figure 1 requires a complete multiple-scattering analysis, which will be given in a future paper.…”

“…The XANES spectra of 1 and 2 were reported very recently by Zamponi et al, 30 but as will be noted below, there are small differences between their spectra and the spectra reported herein, differences which probably are due to differences in resolution. Further, as will be discussed below, we make assignments completely different from those proposed by Zamponi et al 30 The interpretation of the edge structure in the XANES spectra is not simple, and a detailed analysis of the absorption profiles shown in Figure 1 requires a complete multiple-scattering analysis, which will be given in a future paper. 31 However, in conjunction with the known structures of the compounds, firstapproximation assignments of the absorption peaks below or in the rising edge can be made with a one-electron model based on electronic dipole transitions.…”

“…The XANES spectra of 1 and 2 were reported very recently by Zamponi et al., but as will be noted below, there are small differences between their spectra and the spectra reported herein, differences which probably are due to differences in resolution. Further, as will be discussed below, we make assignments completely different from those proposed by Zamponi et al

1 XANES spectra of Fe[HB(pz) 3 ] 2 , 1 , Fe[HB(3,5-(CH 3 ) 2 pz) 3 ] 2 , 2 , Fe[HB(3,4,5-(CH 3 ) 3 pz) 3 ] 2 , 3 , and Co[HB(pz) 3 ] 2 , 4 , measured at 450, 295, or 77 K, as indicated. The zero of the energy scale is given relative to 7112 and 7709 eV, the K-edges of iron and cobalt foil, respectively.

…”

A Synthetic, Structural, Magnetic, and Spectral Study of Several {Fe[tris(pyrazolyl)methane]2}(BF4)2Complexes: Observation of an Unusual Spin-State Crossover

“…The 295 and 78 K X-ray absorption near-edge structure spectra, the XANES spectra, of 2 and 1 are shown in parts a and b, respectively, of Figure . This figure also shows the changes in the absorption which occur upon cooling from 295 to 78 K. The spectra of 2 are very similar to those reported , for Fe[HB(pz) 3 ] 2 , and the conventional labels have been used for the different observed peaks, whose energies and intensities are given in Table . The position and shape of the edge jump are identical for both complexes, but the shape of absorption C is broader in Fe[HB(pz) 3 ] 2 than in 2 , and its intensity is higher at 295 K. Further, in 2 an additional absorption line is observed between lines C and D at 78 K. As expected, because 2 is LS at both 295 and 78 K, there is little change in its spectrum upon cooling, and the assignments of the different bands are essentially identical to that discussed 26 for Fe[HB(pz) 3 ] 2 .…”

X-ray Absorption Spectroscopic Study of the Temperature and Pressure Dependence of the Electronic Spin States in Several Iron(II) and Cobalt(II) Tris(pyrazolyl)borate Complexes

“…Rather strangely, Zamponi et al do not observe the shoulder, B, in the spectrum of 2 but do observe it in the spectrum of 1 and, in spite of its high intensity, assign this shoulder to the forbidden 1s to 3d transition, an assignment we cannot accept, especially in the view of the presence of the pre-edge peak, P, in all of our spectra and in the spectra of Zamponi et al …”

“…The relative energies and normalized intensities of the XANES absorptions are given in Table 1. The XANES spectra of 1 and 2 were reported very recently by Zamponi et al, 30 but as will be noted below, there are small differences between their spectra and the spectra reported herein, differences which probably are due to differences in resolution. Further, as will be discussed below, we make assignments completely different from those proposed by Zamponi et al 30 The interpretation of the edge structure in the XANES spectra is not simple, and a detailed analysis of the absorption profiles shown in Figure 1 requires a complete multiple-scattering analysis, which will be given in a future paper.…”

“…The XANES spectra of 1 and 2 were reported very recently by Zamponi et al, 30 but as will be noted below, there are small differences between their spectra and the spectra reported herein, differences which probably are due to differences in resolution. Further, as will be discussed below, we make assignments completely different from those proposed by Zamponi et al 30 The interpretation of the edge structure in the XANES spectra is not simple, and a detailed analysis of the absorption profiles shown in Figure 1 requires a complete multiple-scattering analysis, which will be given in a future paper. 31 However, in conjunction with the known structures of the compounds, firstapproximation assignments of the absorption peaks below or in the rising edge can be made with a one-electron model based on electronic dipole transitions.…”

“…The XANES spectra of 1 and 2 were reported very recently by Zamponi et al., but as will be noted below, there are small differences between their spectra and the spectra reported herein, differences which probably are due to differences in resolution. Further, as will be discussed below, we make assignments completely different from those proposed by Zamponi et al

1 XANES spectra of Fe[HB(pz) 3 ] 2 , 1 , Fe[HB(3,5-(CH 3 ) 2 pz) 3 ] 2 , 2 , Fe[HB(3,4,5-(CH 3 ) 3 pz) 3 ] 2 , 3 , and Co[HB(pz) 3 ] 2 , 4 , measured at 450, 295, or 77 K, as indicated. The zero of the energy scale is given relative to 7112 and 7709 eV, the K-edges of iron and cobalt foil, respectively.

…”