Reductive dechlorination of DDT electrocatalyzed by synthetic cobalt porphyrins in N,N′-dimethylformamide

2011 ◽  
Vol 15 (01) ◽  
pp. 66-74 ◽  
Author(s):  
Weihua Zhu ◽  
Yuanyuan Fang ◽  
Wei Shen ◽  
Guifen Lu ◽  
Ying Zhang ◽  
...  
Keyword(s):  
Cyclic Voltammetry ◽  
Reaction Time ◽  
Oxidation State ◽  
Reductive Dechlorination ◽  
Reaction Products ◽  
Ms Analysis ◽  
Controlled Potential Electrolysis ◽  
Cobalt Porphyrins ◽  
Controlled Potential ◽  
Uv Visible

Two cobalt porphyrins, (OEP) CoII and (TPP) CoII , where OEP and TPP are the dianions of octaethylporphyrin and tetraphenylporphyrin, respectively, were examined as electrocatalysts for the reductive dechlorination of DDT (1,1-bis(4-chlorophenyl)-2,2,2-trichloroethane) in N,N′-dimethylformamide (DMF) containing 0.1 M tetra-n-butylammonium perchlorate (TBAP). No reaction is observed between DDT and the porphyrin in its Co(II) oxidation state but this is not the case for the reduced Co(I) forms of the porphyrins which electrocatalyze the dechlorination of DDT, giving initially DDD (1,1-bis(4-chlorophenyl)-2,2-dichloroethane), DDE (1,1-bis(4-chlorophenyl)-2, 2-dichloroethylene) and DDMU (1,1-bis(4-chlorophenyl)-2-chloroethylene) as determined by GC-MS analysis of the reaction products. A further dechlorination product, DDOH (2,2-bis(4-chlorophenyl)ethanol), is also formed on longer timescales when using (TPP)Co as the electroreduction catalyst. The effect of porphyrin structure and reaction time on the dechlorination products was examined by GC-MS, cyclic voltammetry, controlled potential electrolysis and UV-visible spectroelectrochemistry and a mechanism for the reductive dechlorination is proposed.

Electroreductive dechlorination of α-hexachlorocyclohexane catalyzed by iron porphyrins in nonaqueous media

2014 ◽  
Vol 18 (06) ◽  
pp. 519-527 ◽  
Author(s):  
Weihua Zhu ◽  
Cui Ni ◽  
Lili Liang ◽  
Junwen Li ◽  
Minzhi Li ◽  
...  
Keyword(s):  
Degradation Products ◽  
Iron Porphyrins ◽  
Nonaqueous Media ◽  
Isomeric Mixture ◽  
Ms Analysis ◽  
Controlled Potential Electrolysis ◽  
Controlled Potential ◽  
Uv Visible ◽  
Stepwise Formation

Two iron porphyrins, ( TPP ) FeCl and ( OEP ) FeCl , where TPP and OEP are the dianions of tetraphenylporphyrin and octaethylporphyrin, respectively, were utilized as catalysts for the electroreductive dechlorination of α-hexachlorocyclohexane (α- HCH ) which was monitored by electrochemistry, in situ UV-visible spectroelectrochemistry and controlled potential electrolysis in N , N ′-dimethylformamide. GC-MS analysis of the α- HCH degradation products revealed the stepwise formation of pentachlorocyclohexene and tetrachlorocyclohexadiene as intermediates, prior to generation of the final dechlorination products which consisted of an isomeric mixture of trichlorobenzenes. Based on identification of the intermediates and final products in the reaction, an overall dechlorination mechanism of α-hexachlorocyclohexane is proposed.

DDT-reductive dechlorination catalyzed by cobalt phthalocyanine, 2,3- and 3,4-tetrapyridoporphyrazine complexes in non-aqueous media

2010 ◽  
Vol 14 (02) ◽  
pp. 133-141 ◽  
Author(s):  
Jianguo Shao ◽  
Abegayl Thomas ◽  
Baocheng Han ◽  
Christopher A. Hansen
Keyword(s):  
Cyclic Voltammetry ◽  
Reductive Dechlorination ◽  
Catalytic Properties ◽  
Aqueous Media ◽  
Cobalt Complexes ◽  
Catalytic Performance ◽  
Cobalt Phthalocyanine ◽  
Controlled Potential ◽  
Bulk Electrolysis ◽  
Uv Visible

Neutral cobalt(II) phthalocyanine and 2,3- and 3,4-tetrapyridoporphyrazine complexes were examined in pyridine, dimethyl sulfoxide and N,N-dimethylformamide to evaluate their catalytic properties in the reductive dechlorination of 1,1-bis(4-chlorophenyl)-2,2,2-trichloroethane (p,p'-DDT). Cyclic voltammetry, controlled potential bulk electrolysis and thin-layer UV-visible spectroelectrochemistry of each compound in the presence of DDT indicated that both the singly and doubly reduced species, [Co(I)]- and [Co(I)]2- , can catalyze the dechlorination of DDT through the formation of, and a photoinduced or electrochemically induced cleavage of, the Co-C bond in the organometallic intermediates. GC-MS analysis revealed that DDT was converted to 1,1-bis(4-chlorophenyl)-2, 2-dichloroethane (p,p'-DDD), 1,1-bis(4-chlorophenyl)-2,2-dichloroethylene (p,p'-DDE) and 1,1-bis(4-chlorophenyl)-2-chloroethylene (p,p'-DDMU), upon dechlorination. The catalytic performance of the three cobalt complexes depends upon the reactive nature of each compound, the solvent, the reaction time and the equivalence of DDT. In addition, either DDD or DDE can be catalytically dechlorinated to generate DDMU, possibly through a similar mechanism.

Clam-shaped cyclam-functionalized porphyrin for electrochemical reduction of carbon dioxide

2019 ◽  
Vol 23 (04n05) ◽  
pp. 453-461
Author(s):  
Sumana Tawil ◽  
Hathaichanok Seelajaroen ◽  
Amorn Petsom ◽  
Niyazi Serdar Sariciftci ◽  
Patchanita Thamyongkit
Keyword(s):  
Carbon Dioxide ◽  
Carbon Monoxide ◽  
Cyclic Voltammetry ◽  
Catalytic Activity ◽  
Electrochemical Reduction ◽  
Target Compound ◽  
Faradaic Efficiency ◽  
Controlled Potential Electrolysis ◽  
Improved Stability ◽  
Controlled Potential

A clam-shaped molecule comprising a Zn(II)-porphyrin and a Zn(II)-cyclam is synthesized and characterized. Its electrochemical behavior and catalytic activity for homogeneous electrochemical reduction of carbon dioxide (CO[Formula: see text] are investigated by cyclic voltammetry and compared with those of Zn(II)-meso-tetraphenylporphyrin and Zn(II)-cyclam. Under N2-saturated conditions, cyclic voltammetry of the featured complex has characteristics of its two constituents, but under CO2-saturated conditions, the target compound exhibits significant current enhancement. Iterative reduction under electrochemical conditions indicated the target compound has improved stability relative to Zn(II)-cyclam. Controlled potential electrolysis demonstrates that, without addition of water, methane (CH[Formula: see text] is the only detectable product with 1% Faradaic efficiency (FE). The formation of CH4 is not observed under the catalysis of the Zn(II)-porphyrin benchmark compound, indicating that the CO2-capturing function of the Zn(II)-cyclam unit contributes to the catalysis. Upon addition of 3% v/v water, the electrochemical reduction of CO2 in the presence of the target compound gives carbon monoxide (CO) with 28% FE. Dominance of CO formation under these conditions suggests enhancement of proton-coupled reduction. Integrated action of these Zn(II)-porphyrin and Zn(II)-cyclam units offers a notable example of a molecular catalytic system where the cyclam ring captures and brings CO2 into the proximity of the porphyrin catalysis center.

The Electrochemical Evaluation of the Metal-Carbon Bond Energies (−ΔGBF) of Alkylated Iron and Cobalt Porphyrins [(por)M-R]

1997 ◽  
Vol 01 (02) ◽  
pp. 125-134 ◽  
Author(s):  
AIMIN QIU ◽  
DONALD T. SAWYER
Keyword(s):  
Iron Porphyrins ◽  
Carbon Bond ◽  
Reduction Potentials ◽  
Oxidation Reduction ◽  
Alkyl Derivatives ◽  
Controlled Potential Electrolysis ◽  
Reduction Cycle ◽  
Cobalt Porphyrins ◽  
Controlled Potential ◽  
The Difference

The electron-transfer oxidation-reduction chemistry for the alkyl derivatives of iron and cobalt porphyrins [( por ) M III − R ] has been characterized on the basis of cyclic voltammetric and controlled-potential-electrolysis measurements. The electrogenerated anions of iron and cobalt porphyrins [( por ) M − and ( por −·) M −] are strong nucleophiles that react with alkyl halides ( RX ) via a nucleophilic displacement process to form metal-carbon bonds [( por ) M - R and ( por −·) M - R ]. The difference in the reduction potentials for RX and ( por ) M II provides an approximate measure of the ( por ) M - R bond-formation free energy (−ΔG BF ). The −ΔG BF values for iron porphyrins (14–35 kcal mol−1) and for cobalt porphyrins (20-38 kcal mol−1) depend on the electron density of the porphyrin ring ( OEP > TPP > Cl 8 TPP > F 20TPP) and the structure of the alkyl group (1° > 2° > 3°). Thus, the apparent metal-carbon bond energy (−ΔG BF ) for ( OEP ) Fe III- Bu -n is 28 ± 2 kcal mol−1, and for [( MeO )4 TPP ] Co III- Bu -n is 36 ± 2 kcal mol −1. The ( por −·) M − dianions react with carbon dioxide in an electrocatalysed reduction cycle to give CO and CO 32− via the apparent transient formation of a metal-carbon bond [( por −·) M - C ( O ) O −; −Δ G BF ≥ 12 kcal mol −1 for iron porphyrins].

Electrochemical behavior of C-methoxy, amino, cyano, and mercapto nitrones

1992 ◽  
Vol 70 (7) ◽  
pp. 2076-2080 ◽  
Author(s):  
Bruce J. Acken ◽  
David E. Gallis ◽  
James A. Warshaw ◽  
DeLanson R. Crist
Keyword(s):  
Cyclic Voltammetry ◽  
Electrochemical Behavior ◽  
Spin Trapping ◽  
Redox Behavior ◽  
Electron Process ◽  
Controlled Potential Electrolysis ◽  
Controlled Potential

The redox behavior of various C-substituted nitrones was investigated by cyclic voltammetry in acetonitrile. These included C-methoxynitrones (MeO)CR = N(O)t-Bu with R = C6H5(1a), p-MeOC6H4 (1b), p-NO2C6H4 (1c), and H (1d) and nitrones YCH = N(O)t-Bu with Y = n-BuS (2a), CN (2b), and C6H5NH (2c). All gave anodic peaks which can be identified as oxidations of the nitrone function. Controlled potential electrolysis of 1a at 1.05 V (SCE) showed that its oxidation was a one-electron process. Reduction of 1a occurs stepwise at −2.08 and at −2.47 V, the same potential for reduction of methyl N-tert-butylbenzimidate (MeO)CPh = Nt-Bu. With electrochemical windows of ca. 3 V, all of the nitrones studied appear suitable for spin-trapping experiments.

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