Cobalt complexes with α-amino acid ligands catalyze the incorporation of CO into cyclic carbonates.

Arguably one of the largest research areas involving carbon dioxide (CO) fixation is the coupling of CO to epoxides to form cyclic carbonates and polycarbonates. In this sense, there is an ever-increasing demand for the development of higher-performing catalytic systems that could counterbalance sustainability and energy efficiency in the production of cyclic carbonates. The use of abundant first-row transition metals combined with naturally occurring amino acids may be an ideal catalytic platform to fulfill this demand.

Characterization of a Threonine-Ligated Molybdenyl-Sulfide Cluster as a Putative Cyanide Poisoning Antidote; Intracellular Distribution, Effects on Organic Osmolyte Homeostasis, and Induction of Cell Death.

Binuclear molybdenum sulfur complexes are effective for the catalytic conversion of cyanide into thiocyanate. The complexes themselves exhibit low toxicity and high aqueous solubility, which render them suitable as antidotes for cyanide poisoning. The binuclear molybdenum sulfur complex [(thr)MoO(μ-S)(S)] (thr - threonine) was subjected to biological studies to evaluate its cellular accumulation and mechanism of action.

Towards a selective synthetic route for cobalt amino acid complexes and their application in ring opening polymerization of -lactide.

Catalysts based on cobalt amino acids and 2,2 bipyridine (bipy) present an attractive and cost-effective alternative as ring opening polymerization catalysts, yet this system remains underexplored despite the advantageous coordination properties of amino acids and bipy as ligands combined with the variety of accessible oxidation states and coordination geometries of cobalt. Here, metal complexes of type [Co(aa)(bipy)] with amino acids (aa: glycine, leucine and threonine) as ligands are reported. The complexes were characterized spectroscopically (IR, UV-vis and H, C NMR for diamagnetic species), and by MS spectrometry and elemental analysis.

Synthesis, Characterization, and Reaction Studies of Pd(II) Tripeptide Complexes.

The aqueous synthesis of Pd(II) complexes with alkylated tripeptides led to the hydrolysis of the peptides at low pH values and mixtures of complexed peptides were formed. A non-aqueous synthetic route allowed the formation and isolation of single products and their characterization. Pd(II) complexes with α-Asp(OR)AlaGly(OR), β-Asp(OR)AlaGly(OR), and TrpAlaGly(OR) (R = H or alkyl) as tri and tetradentate chelates were characterized.

Water-Soluble α-Amino Acid Complexes of Molybdenum as Potential Antidotes for Cyanide Poisoning: Synthesis and Catalytic Studies of Threonine, Methionine, Serine, and Leucine Complexes.

Water-soluble complexes are desirable for the aqueous detoxification of cyanide. Molybdenum complexes with α-amino acid and disulfide ligands with the formula K[(L)MoO(μ-S)(S)] (L = leu (), met (), thr (), and ser ()) were synthesized in a reaction of [(DMF)MoO(μ-S)(S)] with deprotonated α-amino acids; leu, met, thr, and ser are the carboxylate anions of l-leucine, l-methionine, l-threonine, and l-serine, respectively. Potassium salts of α-amino acids (leu (), met (), thr (), and ser ()) were prepared as precursors for complexes -, respectively, by employing a nonaqueous synthesis route.

Directed coordination study of [Pd(en)(HO)] with hetero-tripeptides containing C-terminus methyl esters employing NMR spectroscopy.

Alkylation of the C-terminus acids in small peptides allows direction to amine and amide coordination, while changing the peptide composition to form tetradentate κ[n,5,5], where n = 5-, 6-, 7-, or 8-membered ring coordination geometries, can be achieved. The alkylated tripeptide ligands, TrpAlaGly(OMe), β-Asp(OtBu)AlaGly(OMe), Asp(OtBu)AlaGly(OMe), and the fully methylated GSH, γ-Glu(OMe)Cys(SMe)Gly(OMe), were synthesized and their coordination properties to [Pd(en)(HO)] were studied. pH-dependent coordination was analyzed by NMR spectroscopy and the coordination to the alkylated tripeptides at selected pH values inferred from their NMR spectra.

Reaction Chemistry of the -[MoO(μ-S)(S)(DMF)] Complex with Cyanide and Catalytic Thiocyanate Formation.

Removal of cyanide as nontoxic thiocyanate under physiological conditions may serve as a catalytic detoxification route . Aqueous catalytic reaction conditions were explored where at the conditions employed the reaction proceeded to exhaustion in 1 h. The complex, -[MoO(μ-S)(S)(DMF)] , participates in a ligand exchange reaction of the dimethylformamide ligands and cyanide.

Chemical and Clinical Aspects of Metal-Containing Antidotes for Poisoning by Cyanide.

Physiological metabolism of cyanide takes place by a single major pathway that forms non-toxic thiocyanate that is subsequently excreted. Rhodanese is the primary enzyme to execute metabolism of cyanide with minor pathways from other sulfurtransferases in vivo. The rhodanese enzyme depends on sulfur donor availability to metabolize cyanide and poisoning occurs at elevated cyanide concentrations in vivo.

Cytotoxicity studies of water soluble coordination compounds with a [Mo2O2S2](2+) core.

Selected molybdenum sulfur compounds with the formulas (M)[Mo2O2S4L] where (Et4N)2(1), L=S4(2-), (Et4N)(2), L=Cp, (3), L=DMF, K(5), L=serine, M=Et4N(+), K(+), Na(+) and [Mo2O2S2L2] where Na2(4), L=cysteine, and (6), L=threonine, were prepared and subjected to cytotoxicity studies in vitro. The results were analyzed to rank the compounds according to their relative cytotoxicity and to correlate the observed toxicity to specific composition. The results guide future efforts to synthesize highly water soluble, non-toxic, compounds.