This Perspective Article highlights recent theoretical developments, and summarizes the current understanding of the photolytic properties of cobalamins from a computational point of view. The primary focus is on two alkyl cobalamins, methylcobalamin (MeCbl) and adenosylcobalamin (AdoCbl), as well as two non-alkyl cobalamins, cyanocobalamin (CNCbl) and hydroxocobalamin (HOCbl). Photolysis of al...

Strapped or "basket-handle" porphyrins have been investigated previously as hemoglobin mimics and catalysts. The facial selectivity of their interactions with axial ligands is a sensitive test for noncovalent bonding. Here the binding of pyridyl ligands to zinc porphyrins with thioester-linked alkyl straps is investigated in solution by NMR spectroscopy and UV-vis titration, and in the solid st...

Integrins contain two structurally homologous but distantly related domains: an I-like domain that is present in all -subunits and an I domain that is present in some -subunits. Atomic resolution and mutagenesis studies of I domains demonstrate a C-terminal, axial displacement of the 7-helix that allosterically regulates the shape and affinity of the ligand-binding site. Atomic resolution studi...

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...

The nature of the axial ligands of a heme group is an important factor in maintaining the oxidation-reduction potential of a c-type cytochrome. Cytochrome c3 from Desulfovibrio vulgaris Hildenborough contains four bis-histidinyl coordinated hemes with low oxidation-reduction potentials. Site-directed mutagenesis was used to generate a mutant in which histidine 70, the sixth axial ligand of heme...

A spiropyran-based switchable ligand isomerizes upon reaction with lanthanide(III) precursors to generate complexes with an unusual N3 O5 coordination sphere. The air-stable dysprosium(III) complex shows a hysteresis loop at 2 K and a very strong axial magnetic anisotropy generated by the merocyanine phenolate donor.

A series of tunable axial chiral bisphosphine ligands have been synthesized from (S)-MeO-Biphep. The Ir complex of the MeO-PEG-supported ligand (S)-4k has been successfully applied in asymmetric hydrogenation of quinolines with up to 92% ee. The catalyst system is air-stable and recyclable.

Ligand binding and substitution reactions are important for metalloprotein folding and function. The heme sensor of a methyl-accepting chemotaxis GSU0935 is a c-type cytochrome from the bacterium Geobacter sulfurreducens. The heme domain switches one of its axial ligands from H(2)O to a low-spin ligand, presumably Met, upon reduction. The study analyzes the stability and folding kinetics of the...

The title compound, [FeCl2(C12H26N4)]PF6, is the first mononuclear Fe3+ complex of an ethylene cross-bridged tetraaza-macrocycle to be structurally characterized. Comparison with the mononuclear Fe2+ complex of the same ligand shows that the smaller Fe3+ ion is more fully encapsulated by the cavity of the bicyclic ligand. Comparison with the mu-oxo dinuclear complex of an unsubstituted ligand o...

We describe a novel titanium phthalocyanine that shows no aggregation when anchored to nanocrystalline TiO2 films through its axial carboxylated ligand without the use of co-adsorbents; state selective electron injection into the TiO2 is demonstrated, resulting in efficient photocurrent generation in dye sensitised photoelectrochemical solar cells.