scholarly journals Coordination Behavior of 1,4-Disubstituted Cyclen Endowed with Phosphonate, Phosphonate Monoethylester, and H-Phosphinate Pendant Arms

Molecules ◽  
2019 ◽  
Vol 24 (18) ◽  
pp. 3324 ◽  
Author(s):  
Jiří Bárta ◽  
Petr Hermann ◽  
Jan Kotek
Keyword(s):  
Metal Ions ◽  
Metal Ion ◽  
Variable Temperature ◽  
Phosphinic Acid ◽  
Earth Metal ◽  
Structural Motif ◽  
Vis Spectroscopy ◽  
Order Of Magnitude ◽  
Pendant Arms ◽  
The Eu

Three 1,4,7,10-tetraazacyclododecane-based ligands disubstituted in 1,4-positions with phosphonic acid, phosphonate monoethyl-ester, and H-phosphinic acid pendant arms, 1,4-H4do2p, 1,4-H2do2pOEt, and 1,4-H2Bn2do2pH, were synthesized and their coordination to selected metal ions, Mg(II), Ca(II), Mn(II), Zn(II), Cu(II), Eu(III), Gd(III), and Tb(III), was investigated. The solid-state structure of the phosphonate ligand, 1,4-H4do2p, was determined by single-crystal X-ray diffraction. Protonation constants of the ligands and stability constants of their complexes were obtained by potentiometry, and their values are comparable to those of previously studied analogous 1,7-disubstitued cyclen derivatives. The Gd(III) complex of 1,4-H4do2p is ~1 order of magnitude more stable than the Gd(III) complex of the 1,7-analogue, probably due to the disubstituted ethylenediamine-like structural motif in 1,4-H4do2p enabling more efficient wrapping of the metal ion. Stability of Gd(III)–1,4-H2do2pOEt and Gd(III)–H2Bn2do2pH complexes is low and the constants cannot be determined due to precipitation of the metal hydroxide. Protonations of the Cu(II), Zn(II), and Gd(III) complexes probably takes place on the coordinated phosphonate groups. Complexes of Mn(II) and alkali-earth metal ions are significantly less stable and are not formed in acidic solutions. Potential presence of water molecule(s) in the coordination spheres of the Mn(II) and Ln(III) complexes was studied by variable-temperature NMR experiments. The Mn(II) complexes of the ligands are not hydrated. The Gd(III)–1,4-H4do2p complex undergoes hydration equilibrium between mono- and bis-hydrated species. Presence of two-species equilibrium was confirmed by UV-Vis spectroscopy of the Eu(III)–1,4-H4do2p complex and hydration states were also determined by luminescence measurements of the Eu(III)/Tb(III)–1,4-H4do2p complexes.

scholarly journals SBA-15 with Crystalline Walls Produced via Thermal Treatment with the Alkali and Alkali Earth Metal Ions

Materials ◽  
2021 ◽  
Vol 14 (18) ◽  
pp. 5270
Author(s):  
Sung Soo Park ◽  
Sang-Wook Chu ◽  
Liyi Shi ◽  
Shuai Yuan ◽  
Chang-Sik Ha
Keyword(s):  
Metal Ions ◽  
Pore Size ◽  
Metal Ion ◽  
Pore Diameter ◽  
Earth Metal ◽  
Silica Matrix ◽  
Alkali Earth Metal ◽  
Alkali Earth ◽  
Large Pore ◽  
Large Pore Size

Crystalline walled SBA-15 with large pore size were prepared using alkali and alkali earth metal ions (Na+, Li+, K+ and Ca2+). For this work, the ratios of alkali metal ions (Si/metal ion) ranged from 2.1 to 80, while the temperatures tested ranged from 500 to 700 °C. The SBA-15 prepared with Si/Na+ ratios ranging from 2.1 to 40 at 700 °C exhibited both cristobalite and quartz SiO2 structures in pore walls. When the Na+ amount increased (i.e., Si/Na increased from 80 to 40), the pore size was increased remarkably but the surface area and pore volume of the metal ion-based SBA-15 were decreased. When the SBA-15 prepared with Li+, K+ and Ca2+ ions (Si/metal ion = 40) was thermally treated at 700 °C, the crystalline SiO2 of quartz structure with large pore diameter (i.e., 802.5 Å) was observed for Ca+2 ion-based SBA-15, while no crystalline SiO2 structures were observed in pore walls for both the K+ and Li+ ions treated SBA-15. The crystalline SiO2 structures may be formed by the rearrangement of silica matrix when alkali or alkali earth metal ions are inserted into silica matrix at elevated temperature.

scholarly journals Alkali and alkaline earth metal ion binding by a foldamer capsule: selective recognition of magnesium hydrate

2017 ◽  
Vol 53 (67) ◽  
pp. 9300-9303 ◽  
Author(s):  
Pedro Mateus ◽  
Barbara Wicher ◽  
Yann Ferrand ◽  
Ivan Huc
Keyword(s):  
Metal Ions ◽  
Metal Ion ◽  
Alkaline Earth ◽  
Earth Metal ◽  
Selective Recognition ◽  
Alkaline Earth Metal ◽  
Ion Binding ◽  
Metal Ion Binding

A foldamer capsule selectively recognizes some metal ions solely through second-sphere coordination.

scholarly journals Complexation of Mn(II) by Rigid Pyclen Diacetates: Equilibrium, Ki-netic, Relaxometric, DFT and SOD Activity Studies.

2020 ◽  
Author(s):  
Zoltán Garda ◽  
Enikő Molnár ◽  
Nadège Hamon ◽  
Jose Barriada ◽  
David Esteban-Gómez ◽  
...  
Keyword(s):  
Water Molecule ◽  
Metal Ion ◽  
Kinetic Rate Constant ◽  
Sod Activity ◽  
Kinetic Rate ◽  
Order Of Magnitude ◽  
Amine Groups ◽  
Exchange Kinetics ◽  
Coordinated Water ◽  
Pendant Arms

We report the Mn(II) complexes with two pyclen-based ligands (pyclen = 3,6,9,15-tetraazabicyclo[9.3.1]pentadeca-1(15),11,13-triene) functionalized with acetate pendant arms either at positions 3,6 (3,6-PC2A) or 3,9 (3,9-PC2A) of the macrocyclic fragment. The 3,6-PC2A ligand was synthesized in five steps from pyclen-oxalate by protecting one of the secondary amine groups of pyclen using Alloc protecting chemistry. The complex with 3,9-PC2A is characterized by a higher thermodynamic stability (logKMnL = 17.09(2) than the 3,6-PC2A analogue (logKMnL = 15.53(1), 0.15 M NaCl). Both complexes contain a water molecule coordinated to the metal ion, which results in relatively high 1H relaxivities (r1p = 2.72 and 2.91 mM-1 s -1 for the complexes with 3,6- and 3,9-PC2A, respectively, 25 ºC, 0.49 T). The coordinated water molecule displays fast exchange kinetics with the bulk in both cases; the rates (kex 298) are 140106 and 126106 s -1 for [Mn(3,6-PC2A)] and [Mn(3,9- PC2A)], respectively. The two complexes were found to be remarkably inert with respect to their dissociation, with halflives of 63 and 21 h, respectively, at pH 7.4 in the presence of excess Cu(II). The r1p values recorded in blood serum remain constant at least over a period of 120 h. Cyclic voltammetry experiments show irreversible oxidation features shifted to higher potentials with respect to [Mn(EDTA)]2- and [Mn(PhDTA)]2- , indicating that the PC2A complexes reported here have a lower tendency to stabilize Mn(III). The superoxide dismutase activity of the Mn(II) complexes was tested using the xanthine/xanthine oxidase/NBT assay at pH 7.8. The Mn(II) complexes of 3,6-PC2A and 3,9-PC2A are capable to assist the decomposition of superoxide anion radical. The kinetic rate constant of the complex of 3,9-PC2A is smaller by one order of magnitude than that of 3,6-PC2A.

X-Ray Crystal Structure, Acid - Base Properties and Complexation Characteristics of a Methylenephosphonate Derivative of 1,4,7,10-Tetraazacyclododecane

2009 ◽  
Vol 62 (12) ◽  
pp. 1583 ◽  
Author(s):  
Ute Kreher ◽  
Milton T. W. Hearn ◽  
Leone Spiccia
Keyword(s):  
Metal Ions ◽  
Metal Ion ◽  
Dissociation Constants ◽  
Earth Metal ◽  
Intramolecular Hydrogen Bonding ◽  
Transition Metal Ions ◽  
Acid Base ◽  
Complex Formation Constants ◽  
X Ray ◽  
Alkaline Earth Metal Ions

The X-ray crystal structures of 1,4,7-tris(methylenephosphonate)-1,4,7,10-tetraazacyclododecane (DO3P·3.5H2O) and 1,7-bis(methylenephosphonate)-1,4,7,10-tetraazacyclododecane dihydrochloride trihydrate (DO2P·2HCl·3H2O) reveal that two nitrogen atoms in the trans-annular positions are protonated. The macrocyclic ring adopts a (3,3,3,3)-B conformation stabilized by intramolecular hydrogen bonding involving oxygen atoms from the phosphonate groups and the protonated amines. The acid–base dissociation constants of DO3P and metal complex formation constants (for Ca2+, Mg2+, Zn2+, Fe3+) were determined using potentiometric measurements. The first two protonations of DO3P occur at quite high pH and, consequently, were determined by NMR measurements. The stability constants indicate that DO3P forms more stable complexes with the transition metal ions Zn2+ and Fe3+ (log K [ML] = 21.23(4) and 22.74(5) respectively) than with the alkaline earth metal ions Ca2+ and Mg2+ (log K [ML] = 10.96(6) and 8.72(6) respectively). For Fe3+, Ca2+ and Mg2+, the data support the formation of dinuclear species, presumably through the coordination of an additional metal ion to the phosphonate groups.

Self-propelled droplets for extracting rare-earth metal ions

Soft Matter ◽  
2014 ◽  
Vol 10 (33) ◽  
pp. 6316-6320 ◽  
Author(s):  
Takahiko Ban ◽  
Kentaro Tani ◽  
Hiroki Nakata ◽  
Yasunori Okano
Keyword(s):  
Rare Earth ◽  
Metal Ions ◽  
Rare Earth Metal ◽  
Metal Ion ◽  
Earth Metal ◽  
Chemical Gradient ◽  
Specific Metal

We have developed self-propelled droplets having the abilities to detect a chemical gradient, to move toward a higher concentration of a specific metal ion (particularly the dysprosium ion), and to extract it.

scholarly journals Electrochemical Studies for Cation Recognition with Diazo-Coupled Calix[4]arenes

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
Author(s):  
Bongsu Kim ◽  
Tae Hyun Kim
Keyword(s):  
Transition Metal ◽  
Metal Ions ◽  
Metal Ion ◽  
Alkaline Earth ◽  
Earth Metal ◽  
Transition Metal Ions ◽  
Ester Group ◽  
Divalent Metal Ions ◽  
Alkaline Earth Metal Ions ◽  
Cation Recognition

The electrochemical properties of diazophenylcalix[4]arenes bearingortho-carboxyl group (o-CAC) andortho-ester group (o-EAC), respectively, in the presence of various metal ions were investigated by voltammetry in CH3CN.o-CAC ando-EAC showed voltammetric changes toward divalent metal ions and no significant changes with monovalent alkali metal ions. However,o-CAC preferentially binds with alkaline earth and transition metal ions, whereas no significant changes in voltammetric signals are observed ino-EAC with alkaline earth metal ions.o-EAC only binds with other transition metal ions. This can be explained on metal ion complexation-induced release of proton from the azophenol to the quinone-hydrazone tautomer followed by internal complexation of the metal ion with aid of nitrogen atoms andortho-carbonyl groups in the diazophenylazocalix[4]arenes.

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