And ring conformation

With respect to the ring size, it has been stated that neither the redox potentials nor the half-lives of the Ni species are directly correlated to the cavity of the macrocyclic ligand, but the redox potentials are dependent on solvation effects.139 The effect of fused benzene rings and ring conformation has been monitored.140 In Ni complexes of fluorine-containing cyclams (25) the higher oxidation state becomes successively destabilized with respect to Ni, while the lower oxidation state (i.e., Ni1) becomes successively stabilized.141... 

More than any other factors, single-bond conformation and ring conformation dictate overall molecular size and shape. Thus, proper assignment of ground-state conformation is a very important task for calculation. 

This method can be extended (62) to complexes of amino alcohols, such as L-(+)-alaninol, which has a similar skeletal structure to (+)-propylenediamine. However, it is not applicable to amino acid chelate rings as these are nearly planar, and ring conformational effects contribute little to the overall stability of the complex. 

As with other organophosphorus compounds, NMR spectroscopy represents the most useful diagnostic tool in the characterization of dppf complexes. From P and H NMR spectroscopic data, information can be obtained on the coordination site, the symmetry and the fluxional behavior of these complexes. Possible iron-metal interaction and ring conformational changes of the ferrocenyl moieties can also be studied using " Fe Mossbauer spectroscopy. 

We have explored other factors in a preliminary way to ascertain their influence on pV geometry and ring conformation and have isolated the monocyclic phosphorane (O) for study. X-ray analysis (40) shows the usual (a-e) ring orientation but the presence of a chair conformation. This represents the first example of the appearance of the chair conformation stabilized in the absence of hydrogen bonding interactions. Comparison with the related dithiaphosphorinane P analog (P) shows the same (a-e) ring orientation but in the normally observed boat conformation (40). 

The nature, order and ring conformation of individual monosaccharides. 

F NMR chemical shifts are also very sensitive to temperature. Although their temperature dependence has been used extensively to evaluate free energies of activation for conversion of rotamers and ring conformers in substituted ethanes and other... 

A complementary approach to energy-based conformational search methods is the informatics approach, where likely conformations of a molecule are built up from the distributions of geometric parameters (bond lengths, angles, torsions, and ring conformations) in chemically similar molecules to the molecule under investigation. Databases of crystal structures form the richest source of information on molecular... 

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