Search results for "COPP"
showing 10 items of 3147 documents
Effect of temperature and ligand protonation on the electronic ground state in Cu( ii ) polymers having unusual secondary interactions: a magnetic an…
2018
International audience; Two new copper(II) polymeric complexes, {[Cu(HPymat)(H2O)](NO3)}n (1) and [Cu2(Pymat)2(H2O)3]n (2), have been synthesized using the Schiff base ligand H2Pymat [H2Pymat = (E)-2-(1-(pyridin-2-yl)-methyleneamino)terephthalic acid]. Complex 1 is a cationic 1D polymer, whereas complex 2 is a two dimensional polymer. Both complexes were crystallographically, spectroscopically and magnetically characterized. Theoretical studies were performed and the catecholase activity of the complexes was also examined. Complex 1 is a ferromagnetically coupled complex with J = 2.8 cm−1 and 2 shows antiferromagnetic coupling with J = −1.6 cm−1. Both complexes show notable features in the …
Unusual Formation of a Stable 2D Copper Porphyrin Network
2013
Copper(II) 5,15-bis(diethoxyphosphoryl)-10,20-diphenylporphyrin was obtained and characterized by means of cyclic voltammetry, electron paramagnetic resonance, Fourier transform infrared, and UV-visible spectroscopy. Three crystalline forms were grown and studied by means of X-ray diffraction methods (single crystal and powder). The highly electron-withdrawing effect of phosphoryl groups attached directly to the porphyrin macrocycle results in a self-assembling process, with formation of a stable 2D coordination network, which is unusual for copper(II) porphyrins. The resulting 2D structure is a rare example of an assembly based on copper(II) porphyrins where the copper(II) central metal io…
Electrochemical synthesis and structural characterization of Co(II), Ni(II) and Cu(II) complexes of N,N-bis(4,5-dimethyl-2-hydroxybenzyl)-N-(2-pyridy…
2009
The electrochemical oxidation of anodic metal (cobalt, nickel or copper) in a cell containing an acetonitrile solution of the ligand N,N-bis(4,5-dimethyl-2-hydroxybenzyl)-N-(2-pyridylmethyl)amine (H2L) affords complexes [Co2L2].H2O (1), [Ni3L3] (2) and [Cu2L2] 3H2O (4). On using nickel as the anode and the addition to the solution electrolytic phase of the amount of water necessary to saturate the solution, the electrolytic process gave rise to the new compound [Ni2L2(H2O)1.5].CH3CN (3). Compounds 1 and 4 are dimeric and the metal atoms are pentacoordinated. Compound 3 also consists of dimeric neutral molecules with the nickel atoms in both penta- and hexacoordinated environments. The cryst…
Hydrogen and Copper Ion Induced Molecular Reorganizations in Two New Scorpiand-Like Ligands Appended with Pyridine Rings
2010
The synthesis of two new ligands constituted of a tris(2-aminoethyl)amine moiety linked to the 2,6 positions of a pyridine spacer through methylene groups in which the hanging arm is further functionalized with a 2-pycolyl (L1) or 3-pycolyl (L2) group is presented. The protonation of L1 and L2 and formation of Cu(2+) complexes have been studied using potentiometric, NMR, X-ray, and kinetic experiments. The results provide new information about the relevance of molecular movements in the chemistry of this kind of so-called scorpiand ligand. The comparison between these two ligands that only differ in the position of the substituent at the arm reveals important differences in both thermodynam…
A phenoxo-bridged dicopper(ii) complex as a model for phosphatase activity: mechanistic insights from a combined experimental and computational study
2017
A μ-phenoxo-bis(μ2-1,3-acetato)-bridged dicopper(II) complex [CuII2(L1)(μ-O2CMe)2][NO3] (1) has been synthesized from the perspective of modeling phosphodiesterase activity. Structural characterization was done initially with 1·3Et2O (vapour diffusion of Et2O into MeOH solution of 1; poor crystal quality) and finally with its perchlorate salt [CuII2(L1)(μ-O2CMe)2][ClO4]·1.375MeCN·0.25H2O, crystallized from vapour diffusion of n-pentane into a MeCN–MeOH mixture (comparatively better crystal quality). An asymmetric unit of such a crystal contains two independent molecules of compositions [CuII2(L1)(μ-O2CMe)2][ClO4] and [CuII2(L1)(μ-O2CMe)2(MeCN)][ClO4] (coordinated MeCN with 0.75 occupancy), …
Use of a reduced Schiff-Base ligand to prepare novel chloro-bridged chains of rare Cu(II) trinuclear complexes with mixed azido/oxo and chloro/oxo br…
2010
Two mixed bridged one-dimensional (1D) polynuclear complexes, [Cu(3)L(2)(mu(1,1)-N(3))(2)(mu-Cl)Cl](n) (1) and {[Cu(3)L(2)(mu-Cl)(3)Cl].0.46CH(3)OH}(n) (2), have been synthesized using the tridentate reduced Schiff-base ligand HL (2-[(2-dimethylamino-ethylamino)-methyl]-phenol). The complexes have been characterized by X-ray structural analyses and variable-temperature magnetic susceptibility measurements. In both complexes the basic trinuclear angular units are joined together by weak chloro bridges to form a 1D chain. The trinuclear structure of 1 is composed of two terminal square planar [Cu(L)(mu(1,1)-N(3))] units connected by a central Cu(II) atom through bridging nitrogen atoms of end…
Syntheses, structures, and magnetic properties of diphenoxo-bridged Cu(II)Ln(III) and Ni(II)(low-spin)Ln(III) compounds derived from a compartmental …
2010
Syntheses, characterization, and magnetic properties of a series of diphenoxo-bridged discrete dinuclear M(II)Ln(III) complexes (M = Cu or Ni, Ln = Ce-Yb) derived from the compartmental Schiff base ligand, H(2)L, obtained on condensation of 3-ethoxysalicylaldehyde with trans-1,2-diaminocyclohexane, are described. Single crystal X-ray structures of eight Cu(II)Ln(III) compounds (Ln = Ce (1), Pr (2), Nd (3), Sm (4), Tb (7), Ho (9), Er (10), and Yb (12)) and three Ni(II)Ln(III) (Ln = Ce (13), Sm (16), and Gd (18)) compounds have been determined. Considering the previously reported structure of the Cu(II)Gd(III) (6) compound (Eur. J. Inorg. Chem. 2005, 1500), a total of twelve structures are di…
Coordination of Cu2+ Ions to C2 Symmetric Pseudopeptides Derived from Valine
2010
The acid-base and coordination properties of a family of pseudopeptidic ligands with C(2) symmetry derived from valine (4a-e) have been studied using a variety of techniques as a model for metal coordination in peptides and proteins. The Cu(2+) cation has been selected for coordination studies, although, for comparison, some results for Zn(2+) are also presented. Good agreement has been obtained between the results obtained by potentiometric titrations, spectroscopic analysis, and mass spectrometry (ESI) studies. These results highlight the potential for the use of ESI MS for characterizing the nature of the complex species formed. Clearly, the Cu(2+) complexes are much more stable than the…
Tarantula Hemocyanin Shows Phenoloxidase Activity
1998
An enzyme generally catalyzes one well defined reaction with high specificity and efficiency. We report here in contrast that the copper protein hemocyanin of the tarantula Eurypelma californicum exhibits two different functions. These occur at the same active site. While hemocyanin usually is an oxygen carrier, its function can be transformed totally to monophenoloxidase and o-diphenoloxidase activity after limited proteolysis with trypsin or chymotrypsin. N-acetyldopamine (NADA) is more effectively oxidized than L-dopa or dopamine. This irreversible functional switch of tarantula hemocyanin function is limited to the two subunits b and c of its seven subunit types. A conserved phenylalani…
Tyrosinase versus Catechol Oxidase: One Asparagine Makes the Difference
2015
Tyrosinases mediate the ortho-hydroxylation and two-electron oxidation of monophenols to ortho-quinones. Catechol oxidases only catalyze the oxidation of diphenols. Although it is of significant interest, the origin of the functional discrimination between tyrosinases and catechol oxidases has been unclear. Recently, it has been postulated that a glutamate and an asparagine bind and activate a conserved water molecule towards deprotonation of monophenols. Here we demonstrate for the first time that a polyphenoloxidase, which exhibits only diphenolase activity, can be transformed to a tyrosinase by mutation to introduce an asparagine. The asparagine and a conserved glutamate are necessary to…