High sensitivity of the fluorine NMR signals of difluorovinyl analogs of natural hemin: reconstituted heme proteins and self‐exchange electron transfer in model compounds

Mechanism of Electron Transfer in Heme Proteins and Models: The NMR Approach

“…113 The large variations of chemical shifts depending of the oxidation state permitted the measurements of the electron self-exchange rate constants of bis(1-methylimidazole)iron complexes in various solvents by analysis of the line broadening of the 19 F NMR signals (Figure 4). 111 The experimental rate constants were strongly affected by the nature of the solvents, varying from 3.9 × 10 7 to 24 × 10 8 M -1 s -1 for DMSO and acetone, respectively. These measured rate constants are in agreement with previously reported values for other iron porphyrins.…”

“…Incorporation of fluorine atoms in biological molecules permits a dramatic simplification of the spectra, and this advantage has been explored with many different biological systems, in particular with artificial heme proteins. − Thus, 19 F NMR can also be used to determine the self-exchange transfer rate, between ferric and ferrous porphyrins, using difluorovinyl analogues of natural hemin such as iron bis(difluorovinyl) deuterioporphyrins . Actually, this derivative was first synthesized and tested as a photosensitizer for photodynamic therapy .…”

“…Actually, this derivative was first synthesized and tested as a photosensitizer for photodynamic therapy . The large variations of chemical shifts depending of the oxidation state permitted the measurements of the electron self-exchange rate constants of bis(1-methylimidazole)iron complexes in various solvents by analysis of the line broadening of the 19 F NMR signals (Figure ) . The experimental rate constants were strongly affected by the nature of the solvents, varying from 3.9 × 10 7 to 24 × 10 8 M -1 s -1 for DMSO and acetone, respectively.…”

“…[110][111][112] Thus, 19 F NMR can also be used to determine the self-exchange transfer rate, between ferric and ferrous porphyrins, using difluorovinyl analogues of natural hemin such as iron bis(difluorovinyl) deuterioporphyrins. 111 Actually, this derivative was first synthesized and tested as a photosensitizer for photodynamic therapy. 113 The large variations of chemical shifts depending of the oxidation state permitted the measurements of the electron self-exchange rate constants of bis(1-methylimidazole)iron complexes in various solvents by analysis of the line broadening of the 19 F NMR signals (Figure 4).…”

Methodology to determine the NMR chemical shifts of carbon atoms with radical character: A case of low-spin bis(tert-butylisocyanide) complex of (meso-tetrapropylporphyrinato)iron(III)

“…1. This method is based on selfexchange electron transfer between Fe(II) and Fe(III), which has been used for the determination of the kinetic rate constants [16][17][18][19][20]. Under the assumption that the rate for electron exchange between paramagnetic 1 and diamagnetic 2 is fast on the NMR time scale, the observed 1 H and 13 C NMR chemical shifts(δ obs ) of 2 containing x equiv of 1 can be expressed by Eq.…”