Stereochemistry of low-spin cobalt porphyrins. 9. Molecular stereochemistry of two picket fence cobalt(II) derivatives.

The preparation and molecular structures of two five-coordinate cobalt(II) picket fence porphyrinates with imidazole ligands are described, [Co(TpivPP)(L)] (TpivPP, dianion of picket fence porphyrin). The ligands are the unhindered imidazole, 1-ethylimidazole, and the sterically hindered imidazole, 1,2-dimethylimidazole. Although the equatorial aspects of the geometry are quite equivalent, the axial coordination group geometry strongly reflects the differing steric requirements of the axial ligand.

How Does a Heme Carbene Differ from Diatomic Ligated (NO, CO, and CN) Analogues in the Axial Bond?

Compared to well studied diatomic ligands (NO, CN, CO), the axial bonds of carbene hemes is much less known although its significance in biological chemistry. The unusually large quadrupole splitting (Δ E = +2.2 mm·s) and asymmetric parameter (η = 0.

Characterization of Metalloporphines: Iron(II) Carbonyls and Environmental Effects on νCO.

The synthesis and characterization of two new iron(II) porphine complexes is described. Porphine, the simplest porphyrin derivative, has been studied less than other synthetic porphyrins owing to synthetic difficulties and solubility issues. The subjects of this study are two six-coordinate iron(II) species further coordinated by CO and an imidazole ligand (either 1-methylimidazole or 2-methylimidazole).

Hydrogen-Bonding Effects in Five-Coordinate High-Spin Imidazole-Ligated Iron(II) Porphyrinates.

The influence of hydrogen binding to the N-H group of coordinated imidazole in high-spin iron(II) porphyrinates has been studied. The preparation and characterization of new complexes based on [Fe(TPP)(2-MeHIm)] (TPP is the dianion of tetraphenylporphyrin) are reported. The hydrogen bond acceptors are ethanol, tetramethylene sulfoxide, and 2-methylimidazole.

What Can Be Learned from Nuclear Resonance Vibrational Spectroscopy: Vibrational Dynamics and Hemes.

Nuclear resonance vibrational spectroscopy (NRVS; also known as nuclear inelastic scattering, NIS) is a synchrotron-based method that reveals the full spectrum of vibrational dynamics for Mössbauer nuclei. Another major advantage, in addition to its completeness (no arbitrary optical selection rules), is the unique selectivity of NRVS. The basics of this recently developed technique are first introduced with descriptions of the experimental requirements and data analysis including the details of mode assignments.