Iron(III) 2,3-dihydroxyterephthalamides revisited. Charge effects on highly stable ferric complexes

Abstract

A series of substituted 2,3-dihydroxyterephthalamides has been prepared and investigated by means of potentiometry, spectrophotometry and 1 H NMR spectroscopy at 25 °C. Proton association constants for the ligand and formation constants for the ferric complexes are as follows: 2,3-dihydroxy-N,N'-diethylterephthalamide, log β 011

A Bidentate Terephthalamide Ligand, TAMmeg, as an Entry into Terephthalamide-Containing Therapeutic Iron Chelating Agents

“…The benzyl-protected TAM thiaz activated ester 8 is treated with two equivalents of 2-methoxyethylamine to afford the protected TAMmeg ligand (9). The free 2-mercaptothiazoline and excess 2-methoxyethylamine are then removed from the product solution with an aqueous base wash, giving the protected ligand in good yield after condensation of the solution.…”

“…In a recent survey of various terephthalamide ligands, two with neutral side chains (DEATAM (11) and ETAM (12)), one with positively charge side chains (DMETAM (10)), and one with negatively charged side chains (taurTAM (13)), it was found that DMETAM (10) formed significantly more stable iron complexes than the ligands with neutral or negatively charged side chains. 9 This added stability was attributed to the ability of the N,Ndimethylaminoethyl side chains on the terephthalamide to offset the negative charge of the ligand-iron complex when the tertiary amines are protonated at netural pH, thereby increasing the electrostatic attraction between partially formed complexes and additional ligands. Support for this conclusion can be found in comparing the K 2 and K 3 values for the different ligands.…”

“…7 The strong iron binding ability of this unit 8,9 makes it a promising candidate for use in therapeutic chelators. An added advantage of terephthalamide is the ease of tailoring the properties of this unit relative to other chelating units (e.g., hydroxypyridinone) used in the development of iron chelators.…”

Solution interactions between the uranyl cation [UO22+] and histidine, N-acetyl-histidine, tyrosine, and N-acetyl-tyrosine

“…The design includes a platform for the placement of an 'x' shaped stir bar above the cuvette; stirring is introduced remotely by a stir plate directly below the cuvette about 4 cm from the stir bar. The use of a quartz cuvette in this design allows for the collection of data into the UV range, and expands the usefulness of two previously reported spectrometric cells [13,14].…”

“…A 50.00 mL 0.100 M KCl solution, containing histidine was titrated with 0.1000 N KOH at different temperatures. Before each experiment, the electrode was calibrated as described before with an acid to base titration [14,17]. The protonation constants for the carboxylate groups were determined by titration with 0.1000 N HCl after calibration at low pH using previously described methods [14].…”