Proton NMR study of the molecular and electronic structure of ferric chlorin complexes: evidence for .pi. bonding by the orbital derived from the porphyrin a1u orbital

The Heme Prosthetic Group of Lactoperoxidase

“…Increased relaxation rates for paramagnetically influenced nuclei results in very small NOE signal intensities. However, with the use of a viscous solvent (in this case a Me 2 SO-d 6 /D 2 O mixture at low temperatures), NOE enhancement is achieved through an increase in the rotational correlation time of the molecule, and thus an increase in crossrelaxation between nearby protons (30,31). To further enhance the possibility of NOE detection, the resonances selected for saturation were those with the smallest T 1 values of expected NOE pairs so that resulting NOEs could be detected on resonances with the slowest relaxation rates.…”

NMR and EPR Studies of Chloroiron(III) Tetraphenyl-chlorin and Its Complexes with Imidazoles and Pyridines of Widely Differing Basicities

“…[1][2][3][4][5][6][7][8][9][10][11][12] There have been a number of previous studies of synthetic and natural iron chlorin and/or isobacteriochlorin complexes by magnetic resonance techniques, including the seminal paper of Stolzenberg, Strauss and Holm in 1981 13 and additional papers from these authors, 14-18 as well as other researchers. [19][20][21][22][23][24][25][26][27][28][29][30][31] Understanding the electronic properties of the iron(III) complexes of each of the individual "green" hemes is an important step in understanding their mechanisms of action.…”

Electronic Structure of Iron Chlorins: Characterization of Bis(l-valine methyl ester)(meso-tetraphenylchlorin)iron(III)triflate and Bis(l-valine methyl ester)(meso-tetraphenylchlorin)iron(II)

“…16 Pyrrole. The spectrum of 1 shows the pyrrole proton signals at -0.8, -16.4, and -48.3 ppm (298 K).…”

“…For the saturated pyrroline ring, the protons are expected to exhibit low-field π-contact shifts. 16 11 We used a medium value of 7.8 ppm for the chemical shifts of the diamagnetic pyrroles because the relative assignment was not possible at this stage d Chemical shift of the amino ester ligand complexed to a diamagnetic ruthenium porphyrin complex at 298 K with TMS as an internal reference. 53 e Isotropic shift of 1 with a diamagnetic bis(NH2CH(CO2CH3)(CH(CH3)2) Ru(II) complex as the reference.…”

“…Iron chlorins are porphyrin-derived iron-containing prosthetic groups in which one of the peripheral double bonds of the porphyrin ring has been reduced to yield a dihydroporphyrin. Although some investigations of the NMR and EPR spectra of low-spin iron(III) complexes of reduced porphyrins have been investigated by us 11,12 and others, 10,[13][14][15][16][17][18][19][20][21][22] the nature of the electronic ground state is not always clear, and more information is needed on these systems. Magnetic circular dichroism spectroscopy has also been shown to be of great utility in the identification of proximal and distal axial ligands in chlorin-containing proteins.…”