Theory of the temperature dependence of the NMR shift of intermediate spin (S = 1) four-coordinate ferrous porphyrins

Journal Article · Wed Dec 14 00:00:00 EST 1988 · Inorganic Chemistry; (USA)

DOI:https://doi.org/10.1021/ic00299a004· OSTI ID:5447893

McGarvey, B R ^[1]

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1. Univ. of Windsor, Ontario (Canada)

The theory of the NMR shift (pseudocontact and contact) for the intermediate spin state (S = 1) of four-coordinate ferrous porphyrins in developed for the general case of axial symmetry. The theory is then fitted to temperature data for the {sup 1}H NMR shifts of Fe(OEP) (iron (II)), Fe(OEC) (iron(II)), and Fe(TPP). It is also fitted to temperature data for the magnetic susceptibility and magnetic anisotropy of solid Fe(TPP) and Fe(PC) ((phthalocyaninato)iron(II)). The theory assumes the ground state to be a {sup 3}A{sub 2g} state that is spin-orbit coupled with the {sup 3}E{sub g} state at energy {Delta}. In low symmetry the {sup 3}E{sub g} state is split by the energy {delta}. In solution {Delta} = 600 cm {sup {minus}1} for Fe(OEC) and Fe(OEC) and {approximately} 1000 cm {sup {minus}1} for Fe(TPP). {Delta} is reduced to 400 cm {sup {minus}1} in solid Fe(TPP) and is {minus}900 cm{sup {minus}1} in solid Fe(PC) ({sup 3}E{sub g} ground state). In solution {delta} = {minus}700 cm{sup {minus}1} in Fe(OEC). In Fe(OEP) and Fe(OEC), enough experimental data are available to allow the determination of the geometrical factors for the pseudocontact shift of the methyl resonances from the NMR shifts. The theory is successful in explaining the temperature dependence of the pseudocontact shifts and magnetic susceptibilities but does not fully account for the temperature behavior of the contact shifts.

• OSTI ID: 5447893
• Journal Information: Inorganic Chemistry; (USA), Vol. 27:25; ISSN 0020-1669
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
IRON COMPOUNDS
CHEMICAL SHIFT
NUCLEAR MAGNETIC RESONANCE
SPIN-LATTICE RELAXATION
PORPHYRINS
CHEMICAL STATE
MAGNETIC SUSCEPTIBILITY
MOLECULAR STRUCTURE
SPIN
TEMPERATURE EFFECTS
ANGULAR MOMENTUM
CARBOXYLIC ACIDS
HETEROCYCLIC ACIDS
HETEROCYCLIC COMPOUNDS
MAGNETIC PROPERTIES
MAGNETIC RESONANCE
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PARTICLE PROPERTIES
PHYSICAL PROPERTIES
RELAXATION
RESONANCE
TRANSITION ELEMENT COMPOUNDS
400101* - Activation
Nuclear Reaction
Radiometric & Radiochemical Procedures
400201 - Chemical & Physicochemical Properties