The complex anion bis(azido)(tetraphenylporphinato)ferrate(III) has been synthesized and characterized by variable-temperature X-ray structure determinations, powder and single-crystal EPR, IR, and Mössbauer spectroscopy, and magnetic susceptibility measurements. The synthesis utilizes 18-crown-6 to solubilize sodium azide in the synthetic procedure. All physical data for [Na(18C6)(H(2)O)(2)][Fe(TPP)(N(3))(2)].2C(6)H(5)Cl are consistent with a thermal spin-equilibrium system: low spin (S = (1)/(2)) right harpoon over left harpoon high spin (S = (5)/(2)). Structure determinations at 130 and 293 K show equatorial and axial Fe-N bond elongation at 293 K. Fe-N(p) = 1.9991(11) Å, Fe-N(az) = 1.9734(14) Å at 130 K, and Fe-N(p) = 2.010(4) Å, Fe-N(az) = 1.998(2) Å at 293 K. The EPR g values for a powder sample at 4.2 K are 1.81, 2.18, and 2.70. A fit of the powder EPR spectrum at 4.2 K with a crystal field model that allows quartet and sextet admixtures suggests that the first sextet state is approximately 655 cm(-)(1) above the ground doublet. Single-crystal EPR data indicate that the largest g value occurs at an angle of 56 degrees from the porphyrin normal and at 35 and 81 degrees from the Fe-N(p) vectors. The asymmetric azide IR absorption bands at 2014 and 2036 cm(-)(1) can be assigned to low- and high-spin species, respectively, and display temperature-dependent intensities. The Mössbauer experiments reveal a gradual decrease in the quadrupole splitting as the temperature increases from 140 to 300 K. The magnetic susceptibility measurements show a gradual increase of &mgr;(eff) with temperature. Crystal data for [Na(18C6)(H(2)O)(2)][Fe(TPP)(N(3))(2)].2C(6)H(5)Cl (130 K): a = 11.417(2) Å, b = 12.371(4) Å, c = 12.628(2) Å, alpha = 64.30(2) degrees, beta = 77.18(3) degrees, gamma = 77.67(2) degrees, triclinic, space group P&onemacr;, Z = 1. Crystal data (293 K): a = 11.7652(12) Å, b = 12.6488(6) Å, c = 12.8608(13) Å, alpha = 62.02(2) degrees, beta = 75.996(7) degrees, gamma = 75.465(9) degrees.
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Inorg Chem
April 2020
Research Center for Thermal and Entropic Science, Graduate School of Science, Osaka University, 1-1 Machikaneyama-cho, Toyonaka, Osaka 560-0043, Japan.
Two crystal polymorphs of Ni(cyclam)I (cyclam = 1,4,8,11-tetraazacyclotetradecane) were synthesized, and their magnetic properties were investigated. Temperature-dependent X-ray structural analysis and magnetic measurements revealed gradual spin transition in molecular-crystal polymorph -[Ni(cyclam)I] (), whereas the zigzag-chain polymorph -[Ni(cyclam)(μ-I)]I () did not show an obvious spin transition. The entropy difference between high- and low-spin states of estimated by assuming the spin-equilibrium model is much smaller than those in typical iron(II)-based spin-crossover (SCO) complexes, suggesting that the normal mode softening is less remarkable in .
View Article and Find Full Text PDFChem Commun (Camb)
November 2017
Biophysics and Department of Chemistry, University of Michigan, Ann Arbor, MI 48109-1055, USA.
Heme's spin-multiplicity is key in determining the enzymatic function of cytochrome P450 (cytP450). The origin of the low-spin state in ferric P450 is still under debate. Here, we report the first experimental demonstration of P450's membrane interaction altering its spin equilibrium which is accompanied by a stronger affinity for cytochrome b.
View Article and Find Full Text PDFJ Inorg Biochem
July 2014
Department of Physiology and Biophysics and The Massey Cancer Center, Virginia Commonwealth University School of Medicine, Richmond, VA 23219, United States. Electronic address:
The acidic residues of the "acid-alcohol pair" in CYP51 enzymes are uniformly replaced with histidine. Herein, we adopt the Mycobacterium tuberculosis (mt) enzyme as a model system to investigate these residues' roles in finely tuning the heme conformation, iron spin state, and formation and decay of the oxyferrous enzyme. Properties of the mtCYP51 and the T260A, T260V, and H259A mutants were interrogated using UV-Vis and resonance Raman spectroscopies.
View Article and Find Full Text PDFBiotechnol Appl Biochem
August 2014
Skaggs School of Pharmacy and Pharmaceutical Science, University of California, San Diego, La Jolla, CA, USA.
We have explored the adaptation of the cytochromes P450 (P450) of deep-sea bacteria to high hydrostatic pressures. Strict conservation of the protein fold and functional importance of protein-bound water make P450 a unique subject for the studies of high-pressure adaptation. Earlier, we expressed and purified a fatty-acid binding P450 from the deep-sea bacteria Photobacterium profundum SS9 (CYP261C1).
View Article and Find Full Text PDFBiochemistry
December 2010
Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, 9500 Gilman Drive, La Jolla, California 92093-0703, United States.
We report cloning, expression in Escherichia coli, and purification of cytochrome P450 from a deep-sea bacterium Photobacterium profundum strain SS9 (P450-SS9). The enzyme, which is predominately high spin (86%) in the absence of any added ligand, binds fatty acids and their derivatives and exhibits the highest affinity for myristic acid. Binding of the majority of saturated fatty acids displaces the spin equilibrium further toward the high-spin state, whereas the interactions with unsaturated fatty acids and their derivatives (arachidonoylglycine) have the opposite effect.
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