Spectroscopic and electrochemical properties of group 12 acetates of di-2-pyridylketone thiophene-2-carboxylic acid hydrazone (dpktch-H) complexes. The structure of [Cd(η3-N,N,O-dpktch-H)2]

Bakir, Mohammed; Lawrence, Mark A.W.; McBean, Shameal

doi:10.1016/j.saa.2015.03.079

Cited by 17 publications

(4 citation statements)

References 30 publications

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“…Generally, the potentials were more positive relative to the free quin. The shift in the values of the redox potentials of the ligand upon complexation to the cobalt metal centre clearly indicated that the cyclic voltamograms of [Co(quin)Cl 2 ] is not a simple addition of the cyclic voltammograms of the metal centre and quin ligand ( Figure S13) [69,70]. The non-additive nature of the cyclic voltammogram also indicated that the [Co(quin)Cl 2 ] species does not undergo complete solvolysis in the CH 3 CN-H 2 O mixture, i.e.…”

Section: Electrochemical Behaviour Of Quin and [Co(quin)cl 2 ]mentioning

confidence: 99%

Assessing the stability of the Co(I) species of two mononuclear dichlorocobalt compounds bearing 2,2′-bipyridine and trans-2-(2′-quiolyl)methylene-3-quinuclidione via 59Co NMR spectroscopy, electrochemical, and catalyzed proton electroreduction studies

Lawrence

Holder

2016

Inorganica Chimica Acta

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The Co(I) species resulting from the reduction of two mononuclear species [CoL n Cl 2 ] (where L = 2,2'bipyridine (bpy) and n = 2, or L = trans-2-(2'-quiolyl)methylene-3-quinuclidione (quin) and n = 1), was studied by 59 Co NMR spectroscopy, UV-visible-NIR spectroscopy, and spectroelectrochemical techniques. A quasi-stable Co(I) species produced by the reduction of [Co(bpy) 2 Cl 2 ] was studied and gave a 59 Co NMR spectroscopic chemical shift of 2934 ppm in CD 3 CN-D 2 O (4:1, v/v) and a broad peak of  max = 600 nm in the UV-visible region of the spectrum. The Co(I) species generated from [Co(quin)Cl 2) (when reduced by electrochemical methods) was found to be unstable and produced a transient of  max = 530 nm. Both [CoL n Cl 2 ] species were examined as electrocatalysts for the proton reduction in an acetonitrile-water solvent mixture in the presence of p-cyanoanilinium tetrafluoroborate. The electrochemical properties of both species showed a dependence on the supporting electrolyte which also affected the electrocatalytic behavior. The simulation of the cyclic voltammograms in CH 3 CN-H 2 O (4:1, v/v) allowed for the extraction of kinetic data and suggested a homogenous reaction following the reduction to a Co(I) metal centre with rate constants k = 0.01 s-1 and 2 M s-1 for the Co(I) species with the ligands, bpy and quin, respectively. Analysis of the head space of controlled potential electrolysis experiments for an hour, in the presence of p-cyanoanilinium tetrafluoroborate, confirmed the production of hydrogen, and also showed that the supporting electrolyte affected the production of hydrogen at a glassy carbon electrode in CH 3 CN-H 2 O (either 1:1 or 4:1, v/v). A mechanism was postulated which involved a Co III-H species as the most likely candidate and appeared to involve both a homolytic and a heterolytic pathway towards the production of hydrogen.

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Section: Electrochemical Behaviour Of Quin and [Co(quin)cl 2 ]mentioning

confidence: 99%

Assessing the stability of the Co(I) species of two mononuclear dichlorocobalt compounds bearing 2,2′-bipyridine and trans-2-(2′-quiolyl)methylene-3-quinuclidione via 59Co NMR spectroscopy, electrochemical, and catalyzed proton electroreduction studies

Lawrence

Holder

2016

Inorganica Chimica Acta

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“…The presence of [Co(phen) 3 ](PF 6 ) 3 in the sample may be unreacted 1,10-phenanthroline brought forward from the preparation of the [Co(phen) 2 CO 3 ]ClÁ5H 2 O or may be the result of ligand scrambling in solution [41]. Ligand scrambling might also account for the weak 59 Co NMR signal observed at 6807 ppm which could be the result of [Co(bpy) 3 ](PF 6 ) 3 as the [Co(phen) 2 (H 2 O) 2 ] shows a 59 Co NMR resonance at 7019 ppm (see Fig S5).…”

Section: Spectroscopic Characterizationmentioning

confidence: 99%

Synthesis, X-ray Crystallographic, Electrochemical, and Spectroscopic Studies of Bis-(1,10-phenanthroline)(2,2′-bipyridine)cobalt(III) Hexafluorophosphate

et al. 2015

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The synthesis, X-ray crystallographic, electrochemical, and spectroscopic studies of bis-(1,10-phenanthroline)(2,2 0 -bipyridine)cobalt(III) hexafluorophosphate with acetone solvent of crystallization ([Co(phen) 2 (bpy)](PF 6 ) 3 Á1.6(CH 3 ) 2 CO) is reported. The compound crystallized in a monoclinic space group P2(1)/n with a = 13.215 (3) The cobalt(III) metal center has a slightly distorted octahedral geometry. 1,10-Phenanthroline and 2,2 0 -bipyridine ligands were generally planar, and did not exhibit p-p overlap. The packing of the cations was stabilized by hydrogen bonding with hexafluorophosphate anions. The electrochemical studies revealed the Co III/II , Co II/I and Co I/0 redox couples at E 1/2 = ?0.32, -0.91 and -1.61 V (vs AgCl/Ag) respectively in acetonitrile. 59 Co NMR spectroscopic studies revealed that the [Co(phen) 2 (bpy)](PF 6 ) 3 Á0.5 (C 2 H 5 ) 2 O species has a chemical shift of 6900 ppm in DMSO-d 6 . GraphicalAbstract The mononuclear complex, [Co(phen) 2 (bpy)](PF 6 ) 3 Á1.6(CH 3 ) 2 CO) was synthesized and characterized, but more revealing 59 Co NMR spectroscopic studies on the complex revealed interesting species in DMSO-d 6 .

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“…Our interest in the electron transfer processes involving transition metal complexes,, as well as the electro‐catalytic reduction of protons and other small molecules,, has led to the development of these pincer ligands, bearing sulfur and nitrogen coordination sites. In this report, we outline the rich electrochemistry of two pincer ligand systems, along with the electro‐catalytic behavior of the Pd(II) coordination complexes of these systems containing “κ 3 ‐SNS” and “κ 3 ‐SNN” coordination modes, respectively, towards the reduction of protons in DMF.…”

Section: Introductionmentioning

confidence: 99%

SNS versus SNN Pincer Ligands: Electrochemical Studies and Their Palladium(II) Complexes as Electro‐Catalyst for Proton Reduction

Lawrence

Mulder

2018

ChemistrySelect

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Electrochemical measurements on pincer ligands bis‐N‐(2,5‐dimethoxyphenyl)pyridine‐2,6‐dicarbothioamide (pdcta) and 6‐(4,7‐dimethoxy‐2‐benzothiazolyl)‐N‐(2,5‐dimethoxyphenyl)‐2‐pyridinecarbothioamide (pbcta) in N,N‐dimethylformamide (DMF) and dimethylsulfoxide (DMSO) on a glassy carbon working electrode revealed sulfur centred electrochemical processes. Spectroscopic, elemental and electrochemical analyses indicated that pdcta coordinated to Pd(II) via a κ3‐SNS mode to give 1 whereas pbcta coordinated via a κ3‐SNN mode to give 2. Electrochemical measurements in DMF indicated that the reduction of Pd(II)→Pd(0) proceeded in a concerted manner in the 2, whereas reduction was resolved into the Pd(II)→Pd(I)→Pd(0) in the case of 1. In the presence of p‐toluenesulfonic acid, both palladium complexes displayed electro‐catalytic proton reduction in DMF, with associated overpotentials calculated to be 97 mV and 156 mV for 1 and 2, respectively. The data suggests that the κ3‐SNS pincer ligand enhances the activity of the Pd(II) towards proton reduction relative to 1.

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Spectroscopic and electrochemical properties of group 12 acetates of di-2-pyridylketone thiophene-2-carboxylic acid hydrazone (dpktch-H) complexes. The structure of [Cd(η3-N,N,O-dpktch-H)2]

Cited by 17 publications

References 30 publications

Assessing the stability of the Co(I) species of two mononuclear dichlorocobalt compounds bearing 2,2′-bipyridine and trans-2-(2′-quiolyl)methylene-3-quinuclidione via 59Co NMR spectroscopy, electrochemical, and catalyzed proton electroreduction studies

Assessing the stability of the Co(I) species of two mononuclear dichlorocobalt compounds bearing 2,2′-bipyridine and trans-2-(2′-quiolyl)methylene-3-quinuclidione via 59Co NMR spectroscopy, electrochemical, and catalyzed proton electroreduction studies

Synthesis, X-ray Crystallographic, Electrochemical, and Spectroscopic Studies of Bis-(1,10-phenanthroline)(2,2′-bipyridine)cobalt(III) Hexafluorophosphate

SNS versus SNN Pincer Ligands: Electrochemical Studies and Their Palladium(II) Complexes as Electro‐Catalyst for Proton Reduction

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