Synthesis, characterisation, electrochemical studies and catecholase activity of a new series of binuclear copper (II) complexes

Parimala, S.; Gita, K.N.; Kandaswamy, M.

doi:10.1016/s0277-5387(98)00131-4

Cited by 32 publications

(8 citation statements)

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“…19 Several Cu II Cu IIbased models with catechol oxidase activity have been described. [20][21][22][23][24][25][26][27][28][29][30][31][32] In the first systematic study, Nishida et al pointed out that dinuclear copper(II) complexes show a high catalytic activity compared to mononuclear complexes and proposed that a determining factor is the presence of two metal centers located in close proximity to facilitate the binding of the two oxygen atoms of the catechol prior to the electron transfer. Our previous studies 8 on the catalytic oxidation of catechol performed with dicopper(II) complexes from HL CH 3 showed that the catecholase activities are drastically dependent on the copper-copper distance which was modified upon pH-induced changes in the coordination sphere of the complex.…”

Section: Resultsmentioning

confidence: 99%

Dicopper(II) Complexes of H-BPMP-Type Ligands: pH-Induced Changes of Redox, Spectroscopic (¹⁹F NMR Studies of Fluorinated Complexes), Structural Properties, and Catecholase Activities

et al. 2002

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Substitution of the methyl group from the H-BPMP (HL(CH)3) ligand (2,6-bis[(bis(2-pyridylmethyl)amino)methyl]-4-methylphenol) by electron withdrawing (F or CF(3)) or electron donating (OCH(3)) groups afforded a series of dinucleating ligand (HL(OCH)3, HL(F), HL(CF)3), allowing one to understand the changes in the properties of the corresponding dicopper complexes. Dinuclear Cu(II) complexes have been synthesized and characterized by spectroscopic (UV-vis, EPR, (1)H NMR) as well as electrochemical techniques and, in some cases, by single-crystal X-ray diffraction: [Cu(2)(L(OCH)3)(muOH)][(ClO(4))(2)].C(4)H(8)O, [Cu(2)(L(F))(muOH)][(ClO(4))(2)], [Cu(2)(L(F))(H(2)O)(2)][(ClO(4))(3)].C(3)D(6)O, and [Cu(2)(L(CF)3)(H(2)O)(2)][(ClO(4))(3)].4H(2)O. Significant differences are observed for the Cu-Cu distance in the two mu-hydroxo complexes (2.980 A (R = OCH(3)) and 2.967 A (R = F)) compared to the two bis aqua complexes (4.084 A (R = F) and 4.222 A (R = CF(3))). The mu-hydroxo and bis aqua complexes are reversibly interconverted upon acid/base titration. In basic medium, new species are reversibly formed and identified as the bis hydroxo complexes except for the complex from HL(CF)3 which is irreversibly transformed near pH = 10. pH-driven interconversions have been studied by UV-vis, EPR, and (1)H NMR, and the corresponding pK are determinated. In addition, with the fluorinated complexes, the changes in the coordination sphere around the copper centers and in their redox states are evidenced by the fluorine chemical shift changes ((19)F NMR). For all the complexes described here, investigations of the catechol oxidase activities (oxidation of 3,5-di-tert-butylcatechol to the corresponding quinone) are of interest in modeling the catecholase enzyme active site and in understanding aspects of structure/reactivity. These studies show the pH-dependence for the catalytic abilities of the complexes, related with changes in the coordination sphere of the metal centers: only the mu-hydroxo complexes from HL(CH)3, HL(F), and HL(OCH)3 exhibit a catecholase activity. Modification on R-substituent induces a drastic effect on the catecholase activity: the presence of an electron donating group on the ligand increases this activity; the reverse effect is observed with an electron withdrawing group.

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Section: Resultsmentioning

confidence: 99%

Dicopper(II) Complexes of H-BPMP-Type Ligands: pH-Induced Changes of Redox, Spectroscopic (¹⁹F NMR Studies of Fluorinated Complexes), Structural Properties, and Catecholase Activities

et al. 2002

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“…The first apparent result was that the reactivities of the complexes differ significantly. The binuclear complexes have higher activities than the mononuclear complexes. − For example, the binuclear complexes [Cu 2 L 1a ](ClO 4 ) 2 , [Cu 2 L 1b ](ClO 4 ) 2 , and [Cu 2 L 1c ](ClO 4 ) 2 have rate-constant values of 1.27 × 10 -2 , 2.65 × 10 -2 , and 4.23 × 10 -2 min -1 , respectively, whereas the mononuclear complexes [CuL 1a ](ClO 4 ), [CuL 1b ](ClO 4 ), and [CuL 1c ](ClO 4 ) have rate-constant values of 4.89 × 10 -3 , 4.96 × 10 -3 , and 5.41 × 10 -3 min -1 , respectively. The oxidation of catechol to o -quinone requires the presence of two metal ions in close proximity; hence, the rate-constant values of binuclear complexes are comparatively high.…”

Section: Resultsmentioning

confidence: 99%

Synthesis of Lateral Macrobicyclic Compartmental Ligands: Structural, Magnetic, Electrochemical, and Catalytic Studies of Mono- and Binuclear Copper(II) Complexes

Thirumavalavan

Akilan²,

Kandaswamy³

et al. 2003

Inorg. Chem.

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125

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A series of putative mono- and binuclear copper(II) complexes, of general formulas [CuL](ClO(4)) and [Cu(2)L](ClO(4))(2), respectively, have been synthesized from lateral macrocyclic ligands that have different compartments, originated from their corresponding precursor compounds (PC-1, 3,4:9,10-dibenzo-1,12-[N,N'-bis[(3-formyl-2-hydroxy-5-methyl)benzyl]diaza]-5,8-dioxacyclotetradecane; and PC-2, 3,4:9,10-dibenzo-1,12-[N,N'-bis[(3-formyl-2-hydroxy-5-methyl)benzyl]diaza]-5,8-dioxacyclopentadecane). The precursor compound PC-1 crystallized in the triclinic system with space group P(-)1. The mononuclear copper(II) complex [CuL(1a)](ClO(4)) is crystallized in the monoclinic system with space group P2(1)/c. The binuclear copper(II) complex [Cu(2)L(2c)](ClO(4))(2) is crystallized in the triclinic system with space group P(-)1; the two Cu ions have two different geometries. Electrochemical studies evidenced that one quasi-reversible reduction wave (E(pc) = -0.78 to -0.87 V) for mononuclear complexes and two quasi-reversible one-electron-transfer reduction waves (E(1)(pc) = -0.83 to -0.92 V, E(2)(pc) = -1.07 to -1.38 V) for binuclear complexes are obtained in the cathodic region. Room-temperature magnetic-moment studies convey the presence of antiferromagnetic coupling in binuclear complexes [mu(eff) = (1.45-1.55)mu(B)], which is also suggested from the broad ESR spectra with g = 2.10-2.11, whereas mononuclear complexes show hyperfine splitting in ESR spectra and they have magnetic-moment values that are similar to the spin-only value [mu(eff) = (1.69-1.72)mu(B)]. Variable-temperature magnetic susceptibility study of the complex shows that the observed -2J value for the binuclear complex [Cu(2)L(1b)](ClO(4))(2) is 214 cm(-1). The observed initial rate-constant values of catechol oxidation, using complexes as catalysts, range from 4.89 x 10(-3) to 5.32 x 10(-2) min(-1) and the values are found to be higher for binuclear complexes than for the corresponding mononuclear complexes.

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“…In Table 3, deconvolution of this region is given, where the most intensive band is related to the stretching vibrations of the phenolic O-H bonds. These vibrations are appeared at lower energies than the alcoholic O-H ones.The very intensive bands at 1660-1500 cm -1 region accounts as an important band in the infrared spectra of the Schiffbases [10][11][12][13][43][44][45]. Here, a very intensive band at 1641 cm -1 region of the IR spectrum is attributed to the symmetrical stretching modes of C8=N1 and C16=N2 bonds.…”

Section: Vibrational Spectroscopymentioning

confidence: 88%

N,N′-Dipyridoxyl(1,8-diamino-3,6-dioxaoctane) Schiff-base: Synthesis, experimental and theoretical identification

Beyramabadi¹,

Morsali²,

Bozorgmehr³

et al. 2013

Bull. Chem. Soc. Eth.

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ABSTRACT. The N,N′-dipyridoxyl(1,8-diamino-3,6-dioxaoctane) (=H2L) Schiff-base has been synthesized and characterized by IR, 1 H NMR, mass spectrometry and elemental analysis. Its optimized geometry and theoretical vibrational frequencies have been computed using density functional theory (DFT) method via the B3LYP functional. Also, its 1 H and 13 C NMR chemical shifts have been calculated at the same computational level. In optimized geometry of the H2L, the two pyridine rings are perpendicular to each other. The phenolic hydrogens are engaged in intramolecular-hydrogen bonds with the azomethine nitrogens.

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Synthesis, characterisation, electrochemical studies and catecholase activity of a new series of binuclear copper (II) complexes

Cited by 32 publications

References 23 publications

Dicopper(II) Complexes of H-BPMP-Type Ligands: pH-Induced Changes of Redox, Spectroscopic (¹⁹F NMR Studies of Fluorinated Complexes), Structural Properties, and Catecholase Activities

Dicopper(II) Complexes of H-BPMP-Type Ligands: pH-Induced Changes of Redox, Spectroscopic (¹⁹F NMR Studies of Fluorinated Complexes), Structural Properties, and Catecholase Activities

Synthesis of Lateral Macrobicyclic Compartmental Ligands: Structural, Magnetic, Electrochemical, and Catalytic Studies of Mono- and Binuclear Copper(II) Complexes

N,N′-Dipyridoxyl(1,8-diamino-3,6-dioxaoctane) Schiff-base: Synthesis, experimental and theoretical identification

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Synthesis, characterisation, electrochemical studies and catecholase activity of a new series of binuclear copper (II) complexes

Cited by 32 publications

References 23 publications

Dicopper(II) Complexes of H-BPMP-Type Ligands: pH-Induced Changes of Redox, Spectroscopic (19F NMR Studies of Fluorinated Complexes), Structural Properties, and Catecholase Activities

Dicopper(II) Complexes of H-BPMP-Type Ligands: pH-Induced Changes of Redox, Spectroscopic (19F NMR Studies of Fluorinated Complexes), Structural Properties, and Catecholase Activities

Synthesis of Lateral Macrobicyclic Compartmental Ligands: Structural, Magnetic, Electrochemical, and Catalytic Studies of Mono- and Binuclear Copper(II) Complexes

N,N′-Dipyridoxyl(1,8-diamino-3,6-dioxaoctane) Schiff-base: Synthesis, experimental and theoretical identification

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Dicopper(II) Complexes of H-BPMP-Type Ligands: pH-Induced Changes of Redox, Spectroscopic (¹⁹F NMR Studies of Fluorinated Complexes), Structural Properties, and Catecholase Activities

Dicopper(II) Complexes of H-BPMP-Type Ligands: pH-Induced Changes of Redox, Spectroscopic (¹⁹F NMR Studies of Fluorinated Complexes), Structural Properties, and Catecholase Activities