title: Hydrogen-bonding interactions trigger a spin-flip in iron(III) porphyrin complexes.
abstract: A key step in cytochrome P450 catalysis includes the spin-state crossing from low spin to high spin upon substrate binding and subsequent reduction of the heme. Clearly, a weak perturbation in P450 enzymes triggers a spin-state crossing. However, the origin of the process whereby enzymes reorganize their active site through external perturbations, such as hydrogen bonding, is still poorly understood. We have thus studied the impact of hydrogen-bonding interactions on the electronic structure of a five-coordinate iron(III) octaethyltetraarylporphyrin chloride. The spin state of the metal was found to switch reversibly between high (S=5/2) and intermediate spin (S=3/2) with hydrogen bonding. Our study highlights the possible effects and importance of hydrogen-bonding interactions in heme proteins. This is the first example of a synthetic iron(III) complex that can reversibly change its spin state between a high and an intermediate state through weak external perturbations.
authors: Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur-208016 (India).
authors: Dipankar
authors: D
authors: Sahoo
authors: Matthew G
authors: MG
authors: Quesne
authors: Sam P
authors: SP
authors: de Visser
authors: Sankar Prasad
authors: SP
authors: Rath
mesh_terms: D003577:Cytochrome P-450 Enzyme System / Q000737:chemistry / Q000378:metabolism; D005290:Ferric Compounds / Q000737:chemistry*; D006860:Hydrogen Bonding; D008968:Molecular Conformation; D011166:Porphyrins / Q000737:chemistry*; D011789:Quantum Theory; D015204:Spectroscopy, Mossbauer; D013816:Thermodynamics
chemical_list: D005290:Ferric Compounds; D011166:Porphyrins; D003577:Cytochrome P-450 Enzyme System
keywords: electronic structure; hydrogen bonding; porphyrinoids; spin crossover; structure elucidation
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