Rh(III) complexes of singly and doubly reduced phthalocyanine ligands generated by chemical and electrochemical reduction

2001 ◽  
Vol 05 (05) ◽  
pp. 442-448 ◽  
Author(s):  
M. J. CHEN ◽  
R. J. KLINGLER ◽  
J. W. RATHKE
Keyword(s):  
Cyclic Voltammetry ◽  
Electrochemical Reduction ◽  
Aromatic Compounds ◽  
Radical Anion ◽  
Nmr Spectra ◽  
H Nmr ◽  
Paramagnetic Complexes ◽  
Electron Reduction

The paramagnetic complexes ( FPc )( Me ) Rh - (4) and (FPc)( PMe 3)( Me ) Rh - (10) have been prepared by reducing ( FPc )( Me ) Rh (1) and ( FPc )( PMe 3)( Me ) Rh (2) with NaBH 4 in methanol-d4 [ FPc 2- = dianion of 1,4,8,11,15,18,22,25-octakis(trifluoromethyl)phthalocyanine]. Compounds 4 and 10 are further reduced by NaBH 4 to complexes, which are assigned to ( DFPc )( Me ) Rh - (5) and ( DFPc )( PMe 3)( Me ) Rh - (11), respectively. Based on the 1 H NMR spectra of these complexes, 4 and 10 are assigned to the Rh (III) complexes of the singly reduced radical anion FPc ·3-, while 5 and 11 are assigned to the Rh (III) complexes of the doubly reduced, antiaromatic anion DFPc 3-, which has the deuteron bonded to one of its meso nitrogens. As expected, the antiaromatic complexes 5 and 11 are not stable. At -40 °C, 5 was transformed successively into three aromatic compounds, the first of which was assigned to the ring-contracted α,β,γ-triazatetrabenzocorrole complex ( TBC )( Me ) Rh - [ TBC 3- = trianion of 3,6,10,13,17,20,24,27-octakis(trifluoromethyl)-α,β,γ-triazatetrabenzocorrole]. Cyclic voltammetry of 1 and 2 was also carried out. Two reversible one-electron reduction waves were observed for both 1 and 2.

scholarly journals Metallkomplexe mit Tetrapyrrol-Liganden, XXXVIII [1]. Zur Kenntnis der Alkyl- und Arylimidovanadium(IV)-Porphyrine / Metal Complexes with Tetrapyrrole Ligands, XXXVIII [1]. On the Knowledge of Alkyl- and Arylimidovanadium(IV) Porphyrins

1985 ◽  
Vol 40 (10) ◽  
pp. 1362-1370 ◽  
Author(s):  
Johann W. Buchler ◽  
Stefan Pfeifer
Keyword(s):  
Mass Spectra ◽  
Nmr Spectra ◽  
Primary Amines ◽  
Reactive Intermediate ◽  
H Nmr ◽  
Vanadyl Complex ◽  
Elemental Analyses ◽  
Paramagnetic Metal ◽  
Paramagnetic Complexes ◽  
Proton Resonances

A series of novel alkyl or aryiimidovanadium(IV) 5,10,15,20-tetra(p-tolyl)porphyrinates, VNR(TTP) (4a-4g), is described. They are obtained from the vanadyl complex, VO(TTP) (2a) via the reactive intermediate VCl2(TTP) (3b) which undergoes aminolysis with the respective primary amines RNH2 (R = tBu, Ph, pTol, pClPh, pAnis, pBiph, ptBuPh)**. The formulae are proved by elemental analyses and mass spectra. The paramagnetic complexes are stable to water and may thus be purified by chromatography but are hydrolyzed to give 2 a on treatment with acetic acid. The UV/VIS and 1H NMR spectra of 4a-4g are of the same type as 2a, but the former are slightly hypsochromically shifted, and the latter do not show the proton resonances of the organylimide ligands due to the proximity of the paramagnetic metal center.

scholarly journals (2,3-Bis(methylen)bicycIo[2.2.2]octan)zirconocen: Synthese, Struktur und elektrochemische Reduktion/(2,3-Bis(methylene)bicyclo[2.2.2]octane)zirconocene: Synthesis, Structure, and Electrochemical Reduction

1985 ◽  
Vol 40 (2) ◽  
pp. 150-157 ◽  
Author(s):  
Gerhard Erker ◽  
Klaus Engel ◽  
Carl Krüger ◽  
Yi-Hung Tsay ◽  
Edmond Samuel ◽  
...  
Keyword(s):  
Electrochemical Reduction ◽  
Structure Determination ◽  
Radical Anion ◽  
Nmr Spectra ◽  
Activation Barrier ◽  
Intramolecular Rearrangement ◽  
Dynamic Nmr ◽  
Space Group ◽  
X Ray

Photolysis of diphenylzirconocene and 2,3-bis(methylene)bicyclo[2.2.2]octane in toluene at -25 °C yields biphenyl and (2,3-bis(methylene)bicyclo[2.2.2]octane)zirconocene (lg) (67.5% isolated yield).1g exhibits dynamic NMR spectra indicating rapid alternation of diene faces coordinated to zirconium (ring-flip mechanism). This degenerate intramolecular rearrangement is characterized by an extremely low activation barrier (⊿G≠-131°C = 7.1 ± 0.3 kcal/mol). 1g crystallizes in space group P1̄with a = 7.215(1) Å, b = 9.654(1) Å, c = 11.831(1) Å, α = 94.97(1)°, β = 91.81(1)°, and γ = 103.22(1)°. The X-ray structure determination reveals a pronounced metal alkyl character of the (diene)ZrCp2 moiety. Accordingly, 1g is easily reduced electrochemically to give a Zr(III) radical anion (7) observed by esr (g = 1.990; a(H) = 2.976 G; a(Zr) = 18.36 G).

Correlation of the first reduction potential of selected radiosensitizers determined by cyclic voltammetry with theoretical calculations

2011 ◽  
Vol 76 (8) ◽  
pp. 937-946 ◽  
Author(s):  
Miroslav Gál ◽  
Viliam Kolivoška ◽  
Marta Ambrová ◽  
Ján Híveš ◽  
Romana Sokolová
Keyword(s):  
Experimental Study ◽  
Cyclic Voltammetry ◽  
Radical Anion ◽  
Reduction Potential ◽  
Theoretical Calculations ◽  
Dft Method ◽  
Basis Set ◽  
Radical Anions ◽  
Electron Affinities ◽  
Electron Reduction

Radiosensitizers are drugs that make cancer cells more sensitive to radiation therapy. The cytotoxic properties of such compounds are due to the fact that in the cell these compounds undergo one-electron reduction to generate radical anions. Therefore, their theoretical and/or experimental study is of high interest. To determine the correlation between reduction potential determined by cyclic voltammetry measurements and some physicochemical properties of selected radiosensitizers theoretical calculations of electron affinities based on the DFT method with B3LYP functional at the level of 6-311++G** basis set in vacuum were utilized. Very good correlation was found between electron affinities of radiosensitizers and their reduction potential and so called E71 potential that account for the energy necessary to transfer the first electron to an electroactive group at pH 7 in aqueous medium to form a radical anion.

Electrochemical Studies of Organotitanium Nitrogen Fixation Systems

1973 ◽  
Vol 51 (6) ◽  
pp. 815-820 ◽  
Author(s):  
T. Chivers ◽  
E. D. Ibrahim
Keyword(s):  
Cyclic Voltammetry ◽  
Nitrogen Fixation ◽  
Electrochemical Reduction ◽  
Argon Atmosphere ◽  
Electrochemical Studies ◽  
Controlled Potential Electrolysis ◽  
Controlled Potential ◽  
Electron Reduction ◽  
The One ◽  
Ether Solvents

The electrochemical reduction of compounds of the type (π-Cp)2Ti(R)Cl (R = Cl, CH3, C6H5, C5F5, OTiCl(π-Cp)2) in ether solvents has been studied using the techniques of polarography, controlled potential electrolysis, and cyclic voltammetry. The one-electron reduction products, presumably (π-Cp)2TiR (R = CH3, C6F5), are initially green in tetrahydrofuran but, in a dinitrogen or argon atmosphere, they form intensely blue solutions which result from the reaction of (π-Cp)2TiR with tetrahydrofuran solvent.

Syntheses and electrochemical characterization of heteroleptic cyclopentadienyl-bis(dithiolene) complexes of niobium and tantalum

2000 ◽  
Vol 78 (12) ◽  
pp. 1570-1574 ◽  
Author(s):  
I V Jourdain ◽  
F Guyon
Keyword(s):  
Cyclic Voltammetry ◽  
Key Words ◽  
General Formula ◽  
Nmr Spectra ◽  
Variable Temperature ◽  
Redox Properties ◽  
Temperature Dependent ◽  
Oxidation Processes ◽  
H Nmr

Diamagnetic niobium and tantalum complexes of general formula [M(η5-C5Me5)(dithiolene)2] have been prepared (M = Nb, dithiolene = dddt2– (5,6-dihydro-1,4dithiine-2,3-dithiolate) (1); M = Ta, dithiolene = dddt2– (2); M = Nb, dithiolene = dddt2– and dmit2– (1,3-dithiole-2-thione-4,5-dithiolate) (3)). All these complexes exhibit temperature-dependent 1H NMR spectra which result from a fluxional behavior of the dithiolene ligands. Their redox properties have been investigated by cyclic voltammetry and reversible oxidation processes involving the dithiolene ligands have been evidenced for the complexes 1 and 2.Key words: niobium, tantalum, dithiolene, voltammetry cyclic, variable-temperature 1H NMR.

Metallkomplexe mit Tetrapyrrol-Liganden, LII [1]. Synthetische und elektrochemische Untersuchungen an Praseodym-bis(octaethylporphyrinat)-Systemen / Metal Complexes with Tetrapyrrole Ligands, LII [1]. Synthetic and Electrochemical Investigations on Praseodymium-bis(octaethylporphyrinate) Systems

1988 ◽  
Vol 43 (11) ◽  
pp. 1371-1380 ◽  
Author(s):  
Johann W. Buchler ◽  
Martina Kihn-Botulinski ◽  
Bernd Scharbert
Keyword(s):  
Cyclic Voltammetry ◽  
Nmr Spectra ◽  
Mixed Valence ◽  
Electron Systems ◽  
H Nmr ◽  
Transfer Processes ◽  
Reversible Electron Transfer ◽  
Sandwich Type ◽  
Electron Transfer Processes ◽  
Cyclic Voltammetry Data

The preparation of sandwich-type praseodymium-bis(octaethylporphyrinate) systems [Pr(OEP)2]n with different charges -1 ≤ n ≤+1 is described. The following derivatives have been isolated: Praseodymium(III)-hydrogen-bis(octaethylporphyrinate). PrH(OEP)2** (1; n = -1 ) . bis(octaethylporphyrinato)praseodymium(III), Pr(OEP)2 (2; n = 0). and bis(octaethylporphyrinato) praseodymium(III) diiodoaurate(I), [Pr(OEP)2][AuI2] (3; n = +1). For n = 0 or +1, one or both of the porphyrin π-electron systems have defect electrons. The compounds are identified by UV/VIS/NIR, IR and 1H NMR spectra. The cyclic voltammetry data of the "mixed valence' species Pr(OEP)2 in N.N-dimethylformamide are interpreted in terms of three reversible electron transfer processes. The behaviour of PrH(OEP)2 is complicated by a deprotonation occurring during the electrochemical experiment.

Synthesis of chloro(2-methylimidazole) ruthenium(III) complexes and their aqueous solution chemistry, and the crystal structure of [2-MeImH]2[RuCl52-MeIm]

2001 ◽  
Vol 79 (10) ◽  
pp. 1477-1482 ◽  
Author(s):  
Craig Anderson
Keyword(s):  
Crystal Structure ◽  
Aqueous Solution ◽  
Nmr Spectroscopy ◽  
Nmr Spectra ◽  
Solution Chemistry ◽  
Proton Nmr Spectroscopy ◽  
Line Broadening ◽  
Reaction Conditions ◽  
H Nmr ◽  
Paramagnetic Complexes

2-Methylimidazole (2-MeIm) reacts with RuCl3 in aqueous acidic ethanolic medium to give (2-MeImH)2[RuCl5(2-MeIm)] (1) and (2-MeImH)[RuCl4(2-MeIm)2] (2) (2-MeImH = protonated 2-methylimidazole), the ratio depending on reaction conditions used. Molecule 1 crystallizes in the space group Pnma: a = 14.046(2), b = 17.294(2), and c = 8.2778(12) Å. The 1H NMR spectra of these ruthenium(III) complexes have been measured and show peaks with large isotropic shifts and large line broadening characteristic of such paramagnetic complexes. The aquation of complexes 1 and 2 were followed by proton NMR spectroscopy. 1,2-Dimethyl imidazole (1,2-diMeIm) reacts with RuCl3 in methanolic solution to give [RuCl3(1,2-diMeIm)(H2O)S] (S=H2O (3a) or CH3OH (3b)). The aquation reactions of complexes 3a and 3b were followed by 1H NMR.Key words: ruthenium, paramagnetic, antitumour, NMR.

Multistep Electrochemical Reduction Path of Clusters [Os3(CO)10(α-diimine)]: Comparison of Electrochemical and Photochemical Os-Os(α-diimine) Bond Cleavage

2006 ◽  
Vol 71 (2) ◽  
pp. 237-263 ◽  
Author(s):  
František Hartl ◽  
Josephina W. M. van Outersterp
Keyword(s):  
Electrochemical Reduction ◽  
Radical Anion ◽  
Bond Cleavage ◽  
Polymeric Chain ◽  
Parent Cluster ◽  
Diimine Ligands ◽  
Diimine Ligand ◽  
Electron Reduction ◽  
Open Core ◽  
Reactive Cluster

Electrochemical reduction of the triangular clusters [Os3(CO)10(α-diimine)] (α-diimine = 2,2'-bipyridine (bpy), 2,2'-bipyrimidine (bpym)) and [Os3(CO)10(μ-bpym)ReBr(CO)3] produces primarily the corresponding radical anions. Their stability is strongly determined by the π-acceptor ability of the reducible α-diimine ligand, which decreases in the order μ-bpym > bpym >> bpy. Along this series, increasing delocalisation of the odd electron density in the radical anion over the Os(α-diimine) chelate ring causes weakening of the axial (CO)4Os-Os(CO)2(α-diimine) bond and its facile cleavage for α-diimine = bpy. In contrast, the cluster radical anion is inherently stable for the bridging bpym ligand, the strongest π-acceptor in the studied series. In the absence of the partial delocalisation of the unpaired electron over the Re(bpym) chelate bond, the Os3-core of the radical anion remains intact only at low temperatures. Subsequent one-electron reduction of [Os3(CO)10(bpym)]•- at T = 223 K gives the open-triosmium core (= Os3*) dianion, [Os3*(CO)10(bpym)]2-. Its oxidation leads to the recovery of parent [Os3(CO)10(bpym)]. At room temperature, [Os3*(CO)10(bpym)]2- is formed along a two-electron (ECE) reduction path. The chemical step (C) results in the formation of an open-core radical anion that is directly reducible at the cathodic potential of the parent cluster in the second electrochemical (E) step. In weakly coordinating tetrahydrofuran, [Os3*(CO)10(bpym)]2- rapidly attacks yet non-reduced parent cluster molecules, producing the relatively stable open-core dimer [Os3*(CO)10(bpym)]22- featuring two open-triangle cluster moieties connected with an (bpym)Os-Os(bpym) bond. In butyronitrile, [Os3*(CO)10(bpym)]2- is stabilised by the solvent and the dimer [Os3*(CO)10(bpym)]22- is then mainly formed by reoxidation of the dianion on reverse potential scan. The more reactive cluster [Os3(CO)10(bpy)] follows the same reduction path, as supported by spectroelectrochemical results and additional valuable evidence obtained from cyclic voltammetric scans. The ultimate process in the reduction mechanism is fragmentation of the cluster core triggered by the reduction of the dimer [Os3*(CO)10(α-diimine)]22-. The products formed are [Os2(CO)8]2- and {Os(CO)2(α-diimine)}2. The latter dinuclear fragments constitute a linear polymeric chain [Os(CO)2(α-diimine)]n that is further reducible at the α-diimine ligands. For α-diimine = bpy, the charged polymer is capable of reducing carbon dioxide. The electrochemical opening of the triosmium core in the [Os3(CO)10(α-diimine)] clusters exhibits several common features with their photochemistry. The same Os-α-diimine bond dissociates in both cases but the intimate mechanisms are different.

Photochemical and Electrochemical Reduction of Carbon Dioxide Catalyzed by a Polyoxometalate-Organic Photosensitizer Complex

2018 ◽  
Author(s):  
Chandan Dey ◽  
Ronny Neumann
Keyword(s):  
Carbon Dioxide ◽  
Cyclic Voltammetry ◽  
Formic Acid ◽  
Electrochemical Reduction ◽  
Mass Spectroscopy ◽  
Photochemical Reactions ◽  
Reducing Agent ◽  
Covalent Attachment ◽  
Hybrid Complex ◽  
Open Face

<p>A manganese substituted Anderson type polyoxometalate, [MnMo<sub>6</sub>O<sub>24</sub>]<sup>9-</sup>, tethered with an anthracene photosensitizer was prepared and used as catalyst for CO<sub>2</sub> reduction. The polyoxometalate-photosensitizer hybrid complex, obtained by covalent attachment of the sensitizer to only one face of the planar polyoxometalate, was characterized by NMR, IR and mass spectroscopy. Cyclic voltammetry measurements show a catalytic response for the reduction of carbon dioxide, thereby suggesting catalysis at the manganese site on the open face of the polyoxometalate. Controlled potentiometric electrolysis showed the reduction of CO<sub>2</sub> to CO with a TOF of ~15 sec<sup>-1</sup>. Further photochemical reactions showed that the polyoxometalate-anthracene hybrid complex was active for the reduction of CO<sub>2</sub> to yield formic acid and/or CO in varying amounts dependent on the reducing agent used. Control experiments showed that the attachment of the photosensitizer to [MnMo<sub>6</sub>O<sub>24</sub>]<sup>9-</sup> is necessary for photocatalysis.</p><div><br></div>

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