E.P.R. studies of three cupric complexes with nitrogenous ligands

HSU, Y. T.

doi:10.1080/00268977100102241

Cited by 25 publications

(5 citation statements)

References 17 publications

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“…To better understand the resting state electronic structure of the Cu 2 FP complex, EPR and XP spectroscopic studies were undertaken. Figure a (red) depicts the X-band (9.44 GHz) EPR spectrum of CuP in dichloromethane at 30 K. The observed spectral features are consistent with the presence of a single Cu(II) species, − showing a broad signal containing multiline patterns due to hyperfine coupling (hfc) interactions between the magnetic moment of the unpaired electron and the magnetic moments of neighboring nuclei, including a four-line splitting due to the hfc interaction with the 63 Cu ( I = 3/2) nucleus. To obtain the EPR parameters, the respective spin Hamiltonian (see SI page S2 for details) was fit to the data (Figure a, black).…”

Section: Resultsmentioning

confidence: 62%

“…The g -tensor obtained for CuP , as expected, has axial symmetry with values similar to those previously reported for copper tetraphenylporphyrin chelates and cupric protoporphyrin IX dimethyl ester (Table ). , The electron–nuclear hfc interaction also provides information on the local electronic properties of the Cu(II) complex, that is, the electron spin density distribution. In this case, the parameter A ∥ Cu i represents an indirect measure of the electron spin density at the Cu(II) nucleus and the values of g ∥ and A ∥ Cu i obtained for CuP indicate that Cu(II) is coordinated to the porphyrin via four nitrogens in a square planar geometry (Table ).…”

Section: Resultsmentioning

confidence: 99%

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Electrocatalytic Properties of Binuclear Cu(II) Fused Porphyrins for Hydrogen Evolution

et al. 2018

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Binuclear copper(II) porphyrins in which two copper(II) porphyrin macrocycles are doubly fused at the meso-beta positions are shown to be active electrocatalysts for the hydrogen evolution reaction (2H+ + 2e– → H2). Structural characterization, including use of electron paramagnetic resonance and X-ray photoelectron spectroscopies, verifies the fused species contains two copper(II) metal centers in its resting state. In comparison to the nonfused copper(II) porphyrin complex, the fused species is reduced at significantly less applied bias potentials (ΔE 1/2 ∼ 570 mV for the first reduction process). Electrochemical characterization in the presence of substrate protons confirms the production of hydrogen with near-unity Faradaic efficiency, and kinetic analysis shows the catalyst achieves a maximum turnover frequency above 2 000 000 s–1. The enhancement in catalytic performance over analogous nonfused copper(II) porphyrins indicates extended macrocycles provide an advantageous structural motif and design element for preparing electrocatalysts that activate small molecules of consequence to renewable energy.

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Section: Resultsmentioning

confidence: 62%

Section: Resultsmentioning

confidence: 99%

Electrocatalytic Properties of Binuclear Cu(II) Fused Porphyrins for Hydrogen Evolution

et al. 2018

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“…The second-order perturbation theory expressions for the resonance field values were essentially those of Abragam and Bleaney (1970). Correction terms for the nitrogen SHFS were the same as found in the papers by Abkowitz et al (1968), Chen et al (1969), and Hsu (1971). Empirical allowance for line-width anisotropy was included as an option, assuming that the principal source of line-width variation vs. angle was due to unresolved HFS (Pilbrow, 1973;Venable, 1967).…”

Section: Methodsmentioning

confidence: 99%

Role of the copper in galactose oxidase

Cleveland¹,

Coffman²,

Coon³

et al. 1975

Biochemistry

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Galactose oxidase is a metalloenzyme containing a single copper atom per molecule. The mechanism of action of galactose oxidase is studied in this paper by investigating substrate specificity and activation by peroxidase, and probing the copper site by electron spin resonance (ESR) spectroscopy. Line-shape simulation of ESR spectra are also reported and a comparison is made between observed and simulated spectra for galactose oxidase. A comparison is also reported for the enzyme from various commercial sources and enzyme isolated from a fungus in this laboratory. The results of this investigation suggest that the copper is in an environment of four in-plane nitrogens with axial symmetry.

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“…The electron paramagnetic resonance (EPR) spectra of PS-CuTPyP and PSAgTPyP gave well-resolved peaks with metal hyperfine and nitrogen superhyperfine features. The spin-Hamiltonian parameters were evaluated by the known procedure [15][16][17]. An essential step in developing strongly bound porphyrin pairs on the support involves exhaustive quaternisation of all the remaining pyridyl sites of PS-MTPyP to generate their tetracationic species (Step II).…”

Section: Ionically Bound Metalloporphyrin Pairs On Solid Polymer Supportmentioning

confidence: 99%

Ionically bound metalloporphyrin pairs on solid polymer support

Vinodu

Padmanabhan

2001

J. Porphyrins Phthalocyanines

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ABSTRACT:The present work demonstrates a simple and elegant strategy by which synthetically simple porphyrins are grafted on solid polymer support to generate porphyrin pairs held together by strong coulombic forces. Metalloporphyrins of tetra(4-pyridyl)porphyrins (MTPyP) were reacted with chloromethylated polystyrene (PS) beads to get covalently bound monocationic porphyrins on the polymer support (PS-MTPyP ). These were then converted to their tetracationic species (PS-MTMe 3 PyP 4 ) by exhaustive quaternisation, using CH 3 I. IONICALLY BOUND METALLOPORPHYRIN PAIRS ON SOLID POLYMER SUPPORTBiological relevance and varied chemical utilities have made porphyrins in their dimeric/oligomeric form very interesting systems [1][2][3][4][5][6][7][8]. Selective positioning of such dimers and tetramers in the protein envelope is crucial in several life processes. We have demonstrated that considerable electronic and redox tuning of porphyrins is possible by grafting or incorporating them in polymer matrices and also by varying the mode of association between the host matrix and the pigment [9]. We have also attempted to model a few enzyme functions by making use of such a 'polymer effect' and utilising the easy workability of solid polymerimmobilised porphyrins [10][11][12]. In this communication we demonstrate a simple and elegant method by which novel porphyrin pairs could be grafted on a solid polymer surface and present the possibility of generating a wide variety of both homo-and hetero-porphyrin pairs associated through strong coulombic interaction.The strategy for developing the porphyrin pairs involves interacting the surface-functionalised solid polymer with porphyrins having reactive peripheral groups to affect initially a covalent linkage and then converting the grafted porphyrin moieties to tetracationic species and subsequently making them bind coulombically with tetraanionic porphyrins. The reaction process involved in the porphyrin pair generation is depicted in Scheme 1. The polymer support employed for the purpose was Merrifield resin (PS), which is divinylbenzene cross-linked polystyrene functionalised at the surface by chloromethylation containing 2.0 meq of Cl/g of polymer. The porphyrins used for initial grafting were either free-base or metalloderivatives of 5,10,15,20-tetra-4-pyridylporphyrin (MTPyP, M = H 2 , Mn, Cu, Zn, Ag), which were prepared by reported procedures [13,14]. The reaction involved for the grafting process was quaternisation of pyridyl moieties of MTPyP with the surface-CH 2 Cl functions of PS in dimethylformamide (DMF) medium (80°C, 72 h) (Step I in Scheme 1). A typical reaction process involved reacting 1 g of PS with 100 ml of a dilute porphyrin solution of 1 mM strength. The immobilisation of the porphyrin was evident from the characteristic colour formation on the polymer surface, which was persistent and unleachable with any solvent, whether polar or nonpolar, even under boiling condition. Spectrophotometric estimation showed that the extent of MTPyP uptake was in the range ...

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E.P.R. studies of three cupric complexes with nitrogenous ligands

Cited by 25 publications

References 17 publications

Electrocatalytic Properties of Binuclear Cu(II) Fused Porphyrins for Hydrogen Evolution

Electrocatalytic Properties of Binuclear Cu(II) Fused Porphyrins for Hydrogen Evolution

Role of the copper in galactose oxidase

Ionically bound metalloporphyrin pairs on solid polymer support

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