Carboxylic acids Catechol complexes

Adamic and Bartak [6] used high pressure aqueous size exclusion chromatography with reverse pulse amperometric detection to separate copper(II) complexes of poly(amino carboxylic acids), catechol and fulvic acids. The commercially available size exclusion chromatography columns were tested. Columns were eluted with copper(II) complexes of poly(aminocarboxylic acids), citric acids, catechol and water derived fulvic acid. The eluent contained copper(II) to prevent dissociation of the labile metal complexes. Reverse pulse electrochemical measurements were made to minimise oxygen interferences at the detector. Resolution of a mixture of DTP A, EDTA and NTA copper complexes was approximately the same on one size exclusion chromatography column as on Sephadex... 

Vanadium(III) complexes, 473 adenine, 475 alcohols, 478 amides, 474, 480 amines, 474 amino acids, 484 ammonia, 474 aqua, 477 arsines, 476 azide, 475 bipyridyl, 475 bromides, 483 carboxylates, 479 catecholates, 478 chlorides, 482 complexones, 485 cyanides, 474,476 (Wethyl sulfoxide, 480 dioxygen, 478 dithiocarbamates, 481 dithiolates, 481 dithiophosphinates, 481 ethers, 478... 

Fe3 due to its high charge density, small ion radius and low polarisability is a hard Lewis acid and forms stable bonds with hard Lewis bases as oxygen. Its octahedral complexes possess six coordination sites. They can accomodate three two-dentate ligands which for entropic reasons are frequently connected by more or less mobile chains keeping them in the right position. There are three main types of ligands, viz. a) catecholates (which form very stable complexes at pH 7, but they are acid labile), b) hydroxamic acids (ref. 15) and c) carboxylic acid derivatives with a suitably located O- or N-functionality as the second coordination site (refs. 13, 14, 16, 17). 

Mimoun and Roch used hydrazobenzene (PhNHNHPh) for oxygenation of cyclohexane, cyclohexene, and toluene." The most active complex was formed from FCCI2 and carboxylic acid in the presence of hydrazobenzene. Davis et al. used Fepy4Cl2 and PbC02H for the same reaction and proposed the hydroperoxide complex [Fe "(OOH) PhNNHPh)] as an active species."" Sheu et al. used Fe" complexes (Fe(PA) or Fc(DPAH)2) (PA picolinato) for the monooxygenation of saturated hydrocarbons, especially ketonization of methylenic carbons. "" This system was applied to the hydroxylation of aromatic hydrocarbons as reaction mimic for tyrosine hydroxylase."" With phenol as a reactant, the dominant product was catechol. 

In a related study [35], surface complexation of colloidal Ti02 by aryl carboxylic acids (benzoic acid, phthalic acid, isophthalic acid, terephthalic acid, salicylic acid and catechol) has been found to obey the Langmuir Isotherm. Surface chelation is accompanied by a decrease of the point of zero zeta potential (PZZP) and enhanced electron transfer rates from the conduction band and acceptors in solution. The enhanced electron transfer rates observed upon surface chelation (of cobaltocenium dicarboxylate, phenylfluorene and aryl carboxylic acids) suggest that trapping of electrons by Ti(IV) surface states (equation 3) can take place efficiently and removal of such traps by complexation improves the overall performance of the system. 

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