Binding of axial ligands to the nickel(II) of isolated factor F430 from the methyl reductase enzyme of Methanobacterium thermoautotrophicum is demonstrated. Evidence of bis-ligand coordination is obtained from the x-ray absorption, optical, and resonance Raman spectral characterization of F430 and its 12,13-diepimeric isomer in the presence of a large excess of cyanide, pyridine, or 1-methylimi...

Bond-stretch isomerism is predicted not to occur in the parent compound Si4H6 and the substituted 1,3-di-tert-butyl derivative, although the existence of bond-stretch isomerism in the 1,3-dimethyl derivative is a possibility. Bulky bridgehead moieties induce a preference for a short Si−Si bridge bond, while a longer bridge bond length (2.840 Å at the MP2/6-31G(d,p) level) is predicted for the u...

Two-quasiparticle K58 isomeric states in the A;130 and 180 regions are studied with configurationconstrained calculations of potential-energy surfaces. Strong shape-polarization effects due to the two quasiparticles are found. In particular, the nuclei Pb,Hg, and Te can be polarized from ground-state spherical or oblate shapes to prolate shapes, indicating a combination of K isomerism and shape...

The self-assembly of two emeraldine base tetra(aniline) derivatives is investigated using scanning tunneling microscopy. A combination of the scanning tunneling microscopy data and calculations reveals the presence of predicted cis/trans isomerism in this oxidation state. This isomerism is shown to hinder self-assembly into ordered structures, and provides indications as to why the properties o...

The ester functionality does not introduce a center of asymmetry and thus optical and geometric isomerism does not result from the presence of this functional group. The ester functionality (the carbonyl and ether oxygen) is composed of an sp hybridized carbon so it cannot be chiral, and since there is free rotation about the ether bond geometric isomerism also is not possible at the sp center....