Synthesis, pH-Dependent Structural Characterization, and Solution Behavior of Aqueous Aluminum and Gallium Citrate Complexes

Matzapetakis, Manolis; Kourgiantakis, Markos; Dakanali, Marianna; Raptopoulou, Catherine P.; Terzis, A.; Lakatos, Andrea; Kiss, Tamás; Bányai, István; Iordanidis, Lykourgos; Mavromoustakos, Thomas; Salifoglou, A.

doi:10.1021/ic000461l

Cited by 103 publications

(82 citation statements)

References 54 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In solutions containing 1 µm Fe 3ϩ and 0.1 mm citrate at pH ϭ 5Ϫ6, [Fe(citH) 2 ] 3Ϫ and [Fe(cit)] Ϫ were observed. [35] More recently, different complexes formed from Fe III and citric acid in the pH range 1Ϫ13 have been studied by magnetic susceptibility measurements. [36] The crystal structures of several mononuclear dicitrate complexes with metal(iii) ions, with different degrees of protonation, have been obtained in our laboratory.…”

Section: Zero-field Splitting Parameters and Structures Of Compounds mentioning

confidence: 99%

High‐Field EPR Study of Frozen Aqueous Solutions of Iron(III) Citrate Complexes

et al. 2005

View full text Add to dashboard Cite

Keywords: High-field EPR spectroscopy / Iron / Coordination chemistry / Citrate ligand / Tripodal ligand / Spin crossover High-field electron paramagnetic resonance spectra have been measured for frozen aqueous solutions of Fe III citrate at acidic and neutral pH values. At high fields (up to 12 T) and high frequencies (95, 190 and 285 GHz), fine-structure peaks due to resonance between Kramers doublets (±1/2, ±3/2, ±5/ 2) of an S = 5/2 species can be observed when the experiments are performed at high temperatures. A full-matrix diagonalisation approach has been used to derive the spinHamiltonian parameters for the S = 5/2 spin state. In acidic media (pH = 2), the spacing of the fine structure reveals that the value of the axial zero-field splitting (ZFS) parameter D is −0.12 cm −1 without rhombicity. A small but significant g anisotropy can be observed which depends slightly on the frequency and the temperature (g x = 2.014, g y = 2.014 and

show abstract

Section: Zero-field Splitting Parameters and Structures Of Compounds mentioning

confidence: 99%

High‐Field EPR Study of Frozen Aqueous Solutions of Iron(III) Citrate Complexes

et al. 2005

View full text Add to dashboard Cite

show abstract

“…The search for both a reductant and buffer has led us to Ti III citrate which is useful in a wide pH range owing to its three carboxyl groups having pK a s of 3.13, 4.76, and 6.40. [15] Citrate is also an excellent ligand that binds strongly to a number of metals [15][16][17] including titanium. [18] Owing to its good reducing properties and stability at physiological pH, titanium(III) citrate has found use as a reductant in enzymatic reactions.…”

Section: Introductionmentioning

confidence: 99%

Catalytic Generation of Hydrogen with Titanium Citrate and a Macrocyclic Cobalt Complex

Szajna-Fuller

Bakač

2010

Eur J Inorg Chem

View full text Add to dashboard Cite

Hydrogen evolution from acidic aqueous solutions of TiIIIcitrate is strongly catalyzed by Co(dmgBF2)2. The reaction generates an intermediate with maximum absorbance at 770 nm. The slow disappearance of this intermediate takes place simultaneously with the generation of H2 in a process that was most efficient at pH 1.6 (turnover number 53). The loss of the catalytic activity is caused by the loss of the macrocyclic ligand and formation of Coaq2+. Control experiments implicate CoIII as the most likely oxidation state responsible for catalyst destruction, and thus provide indirect evidence for the involvement of CoIII in the catalytic cycle. Taken together, the data suggest that hydrogen generation takes place at least in part by the H+/HCoIII(dmgBF2)2 route. Incitrate‐containing solutions at 7 ≤ pH ≤ 8, the protonation of CoI(dmgBF2)2– to yield HCoIII(dmgBF2)2 has a rate constant kH = 1.4 × 106 M–1 s–1. This reaction is about ten times slower in the absence of citrate.

show abstract

“…In plants citric acid is closely linked with iron acquisition being the main iron ligand for the iron transport in the xylem sap (Pitch et al 1991). The binding of other metals such as copper (Field et al 1974), cobalt (Matzapetakis et al 2000a), lead (Kourgiantakis et al 2000), manganese (Matzapetakis et al 2000b), aluminium (Matzapetakis et al 1999) and gallium (Matzapetakis et al 2001) to citrate has also been described and may prove to be of biological relevance.…”

Section: Introductionmentioning

confidence: 99%

“…From many X-ray crystallography studies it becomes apparent that citrate coordinates metals through its carboxylate and hydroxyl groups (Matzapetakis et al 1998(Matzapetakis et al , 1999(Matzapetakis et al , 2000b(Matzapetakis et al , 2001Shweky et al 1994;Bino et al 1998;Gautier-Luneau et al 2005;Strouse et al 1977). Citric acid (Fig.…”

Section: Introductionmentioning

confidence: 99%

Determination of the pKa value of the hydroxyl group in the α-hydroxycarboxylates citrate, malate and lactate by 13C NMR: implications for metal coordination in biological systems

2009

View full text Add to dashboard Cite

Citric acid is an important metal chelator of biological relevance. Citric acid helps solubilizing metals, increasing their bioavailability for plants and microbes and it is also thought to be a constituent of both the extracellular and cytoplasmic low molecular iron pools occurring in plants and vertebrates. Metal coordination by citric acid involves coordination both by the carboxylate and hydroxyl groups, of particular interest is its alpha-hydroxycarboxylate function. This structural feature is highly conserved in siderophores produced by evolutionarily distant species and seems to confer specificity toward Fe(III) binding. In order to understand the mechanism of metal coordination by alpha-hydroxycarboxylates and correctly evaluate the respective complex stability constants, it is essential to improve the knowledge about the ionisation of the alcohol group in these compounds. We have evaluated the hydroxyl pKa value of citric, malic and lactic acids with the objective of understanding the influence of alpha-carbon substitution. Studies at high pH values, utilizing (13)C NMR, permitted estimation of the pKa values for the three acids. The pKa (alcohol) values (14.4 for citric acid, 14.5 for malic acid, and 15.1 for lactic acid) are considerably higher than the previously reported value for citric acid (11.6) but still lower than the value of 15.5 for methanol. A comparative analysis of the three compounds indicates that different substitutions on the alpha-carbon introduce changes to the inductive effect experienced by the hydroxyl group thereby modulating its ionisation behaviour. Comparison with the siderophore rhizoferrin, which pKa (alcohol) values were confirmed to be 10 and 11.3, suggests that intra-molecular hydrogen bonding may also aid in the hydroxyl ionisation by stabilizing the resulting anion. Studies of metal coordination by alpha-hydroxycarboxylates should take these factors into account.

show abstract

Synthesis, pH-Dependent Structural Characterization, and Solution Behavior of Aqueous Aluminum and Gallium Citrate Complexes

Cited by 103 publications

References 54 publications

High‐Field EPR Study of Frozen Aqueous Solutions of Iron(III) Citrate Complexes

High‐Field EPR Study of Frozen Aqueous Solutions of Iron(III) Citrate Complexes

Catalytic Generation of Hydrogen with Titanium Citrate and a Macrocyclic Cobalt Complex

Determination of the pKa value of the hydroxyl group in the α-hydroxycarboxylates citrate, malate and lactate by 13C NMR: implications for metal coordination in biological systems

Contact Info

Product

Resources

About