Axial ligand field strength

On the other hand, the simple complexes (hemins I and II) have a reverse relation between the ICD magnitudes in the Soret region and the ligand field strengths of the axial ligands bound to the heme for peptides and proteins. This difference between our models 199) and Urry s findings 196 198> may be partly due to the existence of the ring(s) with optically active center(s). 

Fe3+ derivatives of porphyrins and chlorins are all high spin in the absence of N-donor axial ligands and in chlorinated solvents [41,42] the low spin state observed in the case of iron corrolate demonstrates that the ligand field strength of corrole is very different from that of other macrocycles. 

These compounds are the first examples for the stabilization of the LS state of iron(II) with saturated nitrogen as the most abundant donors this has been ascribed by the authors to the enhanced ligand field strength due to the constrictive effect of the mechanically confining in-plane macrocyclic ligand . Six-coordinate iron(II) complexes are formed with relatively weak axial ligands such as X = CH3C002 >... 

Substituting Equation 1 into Equation 5 and defining Dg and Dq as the equatorial (in-plane) and axial (out-of-plane) ligand field strengths, respectively, then (48) ... 

The stereochemical parameters of these three low-spin species are presented in Table II. It can be seen, as in the five-coordinate intermediate-spin complexes, that there is significant variation in the parameters. The general decreases in Fe-Np and displacement follow the binding and ligand field strength of the axial ligand. A particularly noteworthy feature is the variation in the out-of-plane displacement of the low-spin iron(III) atom. 

Ligand field strength of axial ligand increase <... 

The unique electronic structure of these (L-A3)MoO(dithiolene) complexes arises from two basic factors. The first is the strong axial a- and Ji-donor properties of the terminal oxo ligand, which dominates the ligand field and predetermines the energy of the Mo-based dxz, dyz, and dzi acceptor orbitals. The second is the equatorial dithiolene sulfur donors, from which the low-energy LMCT transitions arise. Dithiolene covalency contributions to the electroactive C, or redox, orbital can be directly probed via the relative oscillator strengths of the / —> ixy and /fp —> (/", transitions (see above). These three wave functions may be expanded in terms of Mo- and dithiolene sulfur-based functions ... 

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