- Acid-base behavior and Al3+ complex formation of synthesized 2,3-dihydroxyterephthalic acid (DHTPA) at pH 3 as a model compound of Inogashira fulvic acid (IFA)
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The interaction between the aluminum ion (Al3+) and Inogashira fulvic acid (IFA) at pH 3 was investigated using the calibration curve method for 27Al NMR spectra. The average conditional stability constant (log K) can be calculated to be 2.00-2.04 (M-1) (bidentate-monodentate) from the results of 27Al NMR measurements. In addition, because IFA has various coordination sites, including COOH, phenolic and/or alcoholic OH groups, we attempted to synthesize 2,3-dihydroxyterephthalic acid (DHTPA) as a model compound with the functional groups of IFA for the investigation of the microscopic coordination mechanism between Al3+ and IFA by potentiometric titration and 27Al NMR measurements. The pK ai values of DHTPA could be determined successfully (pKa1 = 2.3, pKa2 = 3.4 and pKa3 = 7.2; pKa4 was not determined), and these values indicate that DHTPA can act as a powerful chelating ligand, even at pH 3. DHTPA can interact with Al3+, and it predominantly forms 1:1 and 2:1 Al-DHTPA complexes. The calculated average conditional formation constant (log K1 and K2) of each complex can be determined as 1.09 (1:1) and 4.81 (M-1) (2:1). The results obtained showed that both the 1:1 and 2:1 Al-DHTPA complexes are formed and Al3+ interacts with IFA at pH3.
- Kurisaki, Tsutomu,Etou, Mayumi,Okaue, Yoshihiro,Wakita, Hisanobu,Yokoyama, Takushi
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- Cyclic Structural Transformations from Crystalline to Crystalline to Amorphous Phases and Magnetic Properties of a Mn(II)-Based Metal-Organic Framework
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A three-dimensional Mn(II) framework, [Mn2(H2L)(L)0.5(MeOH)(DEF)]·0.1MeOH·0.1DEF·1.4H2O (1; H4L = 2,3-dioxido-1,4-benzenedicarboxylic acid), was synthesized under solvothermal conditions in diethylformamide/methanol (DEF/MeOH), where the Mn centers adopt octahedral and unusual pentagonal bipyramidal geometries. The ligand H4L was subject to deprotonation to create μ4-H2L2- and μ6-L4- anionic bridges, leading to the construction of a coordination network. The MeOH exchange process of crystalline 1 allowed for another crystalline phase (1a), which reversibly returned to the original crystalline state upon resolvation in DEF/MeOH. After evacuation of 1a, the amorphous phase 1b was irreversibly formed, followed by the restoration of the original phase 1 upon resolvation in DEF/MeOH. Consequently, this framework underwent cyclic structural transformations from the crystalline (1) to crystalline (1a) to amorphous (1b) and back to crystalline (1) phase, which are unique transformations for soft coordination networks. Magnetic measurements demonstrated that antiferromagnetic interactions were operative between the Mn(II) ions and were effectively mediated by the oxygen moieties of the μ6-L4- bridge.
- Lee, Han Geul,Jo, Hyuna,Eom, Sunhwi,Kang, Dong Won,Kang, Minjung,Hilgar, Jeremy,Rinehart, Jeffrey D.,Moon, Dohyun,Hong, Chang Seop
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- Solvothermal synthesis of a novel calcium metal-organic framework: High temperature and electrochemical behaviour
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The rapid growth in the field of metal-organic frameworks (MOFs) over recent years has highlighted their high potential in a variety of applications. For biological and environmental applications MOFs with low toxicity are vitally important to avoid any harmful effects. For this reason, Ca-based MOFs are highly desirable owing to their low cost and high biocompatibility. Useful Ca MOFs are still rare owing to the ionic character and large size of the Ca2+ ion tending to produce dense phases. Presented here is a novel Ca-based MOF containing 2,3-dihyrdoxyterephthalate (2,3-dhtp) linkers Ca(2,3-dhtp)(H2 O) (SIMOF-4). The material undergoes a phase transformation on heating, which can be followed by variable temperature powder X-ray diffraction. The structure of the high temperature form was obtained using single-crystal X-ray diffraction. The electrochemical properties of SIMOF-4 were also investigated for use in a Na ion battery.
- Armstrong, A. Robert,Cordes, David B.,Desai, Aamod V.,Main, Russell M.,Morris, Russell E.,Slawin, Alexandra M. Z.,Wheatley, Paul
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- MACROCYCLES
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The invention provides macrocycles useful in chelating metal ions, particularly radionuclides, to provide metal ion complexes. The invention also provides methods of using the compounds and complexes of the invention, such as in therapeutic and diagnostic applications.
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Paragraph 0172; 0173; 0174; 0175; 0176; 0177
(2015/06/17)
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- Synthesis of the isocoumarin portion of the rubromycins
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A synthesis of the isocoumarin found in the rubromycin class of natural products is reported. The isocoumarin ring system is formed via Heck coupling of a pyruvate synthon with a terephthalic acid derivative followed by an intramolecular acid-catalyzed cyclization. The requisite terephthalic acid precursor is generated by carboxylation of catechol and then desymmetrization of the aromatic ring by halogenation. The isocoumarin derivative that has been produced is an appropriate precursor for the synthesis of γ-rubromycin, purpuromycin, and heliquinomycin.
- Waters, Stephen P.,Kozlowski, Marisa C.
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p. 3567 - 3570
(2007/10/03)
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- Electroorganic reactions. Part 55. Quinodimethane chemistry. Part 3. Transition metal complexes as inter- and intra-molecular redox catalysts for the electrosynthesis of poly(p-xylylene) (PPX) polymers and oligomers
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The role of metal complexes as redox mediators in the electrosynthesis of poly(p-xylylenes) (PPXs) has been explored, with a view to designing metal-containing precursors that can act both as mediators and starting materials for metal-containing polymers. A number of transition metal complexes [Cr(III), Ni(II) and Co(II)] are efficient redox catalysts for production of quinodimethanes, and hence PPXs. Following encouraging results from experiments using mediators based on anthranilic acid and salicylaldehyde ligands a macrocyclic compound was designed, and successfully prepared by a convergent route that incorporated both a 1,4-bis(chloromethylarene) function as a precursor to a quinodimethane and a Ni(II) salen unit as an intramolecular redox catalyst. The macrocycle was successfully reduced cathodically to yield a PPX polymer with bound Ni(II). Evidence is presented for the operation of intramolecular redox catalysis (homomediation).
- Janssen,Utley,Carre?,Simon,Schirmer
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p. 1573 - 1584
(2007/10/03)
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- Synthetic Enterobactin Analogues. Carboxamido-2,3-dihydroxyterephthalate Conjugates of Spermine and Spermidine
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Two examples of a new class of synthetic polycatecholate ligands, the carboxamido-2,3-dihydroxyterephthalate conjugates of spermine (8) and spermidine (10), have been synthesized via the generally useful synthon methyl-2,3-dimethoxyterephthaloyl chloride (6).Initial biological evaluation reveals tetrameric terephthalate (8) to be an extremely effective agent for sequestering and removing plutonium from mice; a single 25-μmol/kg (ip) dose of 8 removed 73percent of the plutonium citrate previously injected (iv,1h earlier).Under the same conditions, trimeric terephthalate (10) ex creted only 49percent injected plutonium.In vitro kinetic experiments have shown that 10 rapidly and quantitatively removed Fe from human transferrin.These results are discussed in relation to the design of metal-ion specific sequestering agents.
- Weitl, Frederick L.,Raymond, Kenneth N.,Durbin, Patricia W.
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p. 203 - 206
(2007/10/02)
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