Metal Complexes Of Type Research Articles

Coordination of zwitterionic 8-quinolinol (oxine) to mixed oxinate-carboxylate complexes of divalent nickel, manganese, and magnesium

Three types of metal complexes containing coordinated zwitterionic 8-Quinolinol(oxine) are isolated from the reaction ofMOx 2 (M=divalent Ni, Mn, or Mg; HO x =oxine) and haloacetic acidsRCO2H (R=CF3, CCl3, CHCl2, or CH2Cl) in benzene. These types are:M(O2CR)Ox·HOx forM=Ni,R=CCl3, CHCl2, and CH2Cl and forM=Mn,R=CHCl2.MOx(HOx) (RCO2)MOx·nH2O forM=Ni, Mn, or Mg,R=CF3 andn=1,1, and 4, respectively.MO x (HOx) (RCO2)2 MOx forM=Mn andR=CCl3. These types are compared with the simple mixed chelateMn(O2CCH2Cl)Ox. Interrelated reactions are suggested to explain the formation of these metal complexes and the contributing factors are discussed. The coordination of the zwitterion to the metal ion through its phenolate oxygen and the presence of the triatomic system+N−H...O in the three types of metal complexes are evidenced by typical infrared bands. Analytical and spectral data are in accordance with the suggested formulations.

Synthesis and characterization of a new series of rare earth compounds with diselenito and nitrato ligands

The selenite anion is a versatile ligand capable of forming different types of metal complexes. For instance, several manganese(II) selenites can be prepared as crystalline solids where the anion acts as a selenito, hydrogenselenito or as a diselenito ligand depending on reaction conditions (1-3). X-ray studies have revealed that the same types of complexes exist for the rare earths also, although only two structures have been determined so far (4,5). As a part of our continuing investigations of metal selenites and rare earth compounds we have prepared and characterized a new series of rare earth complexes with the composition RE(Se205)NO3-3H20 where RE = Y, Pr, Nd, Sm-Lu.

Types of metal complexes of the ligand 7-nitroso-8-hydroxyquinoline-5-sulphonic acid

Types of metal complexes of the ligand 7-nitroso-8-hydroxyquinoline-5-sulphonic acid

Elasmobranch Carbonic Anhydrase: PURIFICATION AND PROPERTIES OF THE ENZYME FROM TWO SPECIES OF SHARK

Homogeneous carbonic anhydrase has been prepared from erythrocytes of the bull and tiger shark. Molecular and equivalence weight determinations indicate molecular weights in the range of 36,000 to 40,000 depending on the method employed. Amino acid compositions are similar to those reported for mammalian carbonic anhydrases with several notable exceptions. The bull and tiger shark enzymes contain ∼25 and 18 half-cystine residues per molecule, respectively. These residues are apparently present as disulfide cross-links, since neither the native nor denatured molecules react with sulfhydryl reagents, but do react after reduction with mercaptoethanol. There are high contents of glutamic and aspartic acid compatible with the very acidic nature of these proteins. The isoelectric point of the bull shark enzyme is ∼pH 4.5. The shark enzymes catalyze both the hydration of CO2 and the hydrolysis of certain aromatic esters. Maximal catalytic rates are comparable to the high activity forms of mammalian carbonic anhydrases. Aromatic sulfonamides are powerful inhibitors. Circular dichroic spectra in the ultraviolet region indicate the presence of many structural features similar to those found in the mammalian enzymes. The shark enzymes contain 1 g atom of zinc per mole of enzyme. A stable metal-free, inactive apoenzyme can be prepared which is completely reactivated by Zn(II) or Co(II) ions. The Co(II) derivatives have intense visible absorption maxima at 510, 555, 618, and 645 nm. These spectra, as well as the spectra of sulfonamide complexes of the Co(II) enzymes, are almost identical with those of the Co(II) derivatives of mammalian carbonic anhydrases, and suggest that similar coordination geometries exist at the active centers of the elasmobranch and mammalian enzymes. Since fossil morphological evidence suggests that present day shark species have not evolved much since the Devonian period, this particular type of metal complex would appear to have been a constant feature of carbonic anhydrase over 400 million years of animal evolution.