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.

scholarly journals Boosting Electrochemical Performance of Hematite Nanorods via Quenching-Induced Alkaline Earth Metal Ion Doping

Processes ◽  
2021 ◽  
Vol 9 (7) ◽  
pp. 1102
Author(s):  
Qin Chen ◽  
Yanan Chong ◽  
Mumin Rao ◽  
Ming Su ◽  
Yongcai Qiu
Keyword(s):  
Transition Metal ◽  
Metal Ions ◽  
Metal Oxides ◽  
Transition Metal Oxides ◽  
Alkaline Earth ◽  
Earth Metal ◽  
Alkaline Earth Metal ◽  
Electrochemical Performances ◽  
Alkaline Earth Metal Ions ◽  
Ion Doping

Ion doping in transition metal oxides is always considered to be one of the most effective methods to obtain high-performance electrochemical supercapacitors because of the introduction of defective surfaces as well as the enhancement of electrical conductivity. Inspired by the smelting process, an ancient method, quenching is introduced for doping metal ions into transition metal oxides with intriguing physicochemical properties. Herein, as a proof of concept, α-Fe2O3 nanorods grown on carbon cloths (α-Fe2O3@CC) heated at 400 °C are rapidly put into different aqueous solutions of alkaline earth metal salts at 4 °C to obtain electrodes doped with different alkaline earth metal ions (M-Fe2O3@CC). Among them, Sr-Fe2O3@CC shows the best electrochemical capacitance, reaching 77.81 mF cm−2 at the current of 0.5 mA cm−2, which is 2.5 times that of α-Fe2O3@CC. The results demonstrate that quenching is a feasible new idea for improving the electrochemical performances of nanostructured materials.

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.

Effects of alkaline earth metal ions on the growth of Calothrix strain RC3, a natural isolate from Rock Creek, British Columbia

1998 ◽  
Vol 44 (2) ◽  
pp. 128-139 ◽  
Author(s):  
Susanne Douglas
Keyword(s):  
Metal Ions ◽  
Metal Ion ◽  
Alkaline Earth ◽  
Cell Envelope ◽  
Earth Metal ◽  
Outer Membrane Vesicles ◽  
Natural Environments ◽  
Filamentous Cyanobacterium ◽  
Photosynthetic Membrane ◽  
Alkaline Earth Metal Ions

Calothrix is a filamentous cyanobacterium that has a single terminal heterocyst and a tapering morphology. It exists in two forms: mature filaments as described and motile hormogonia, which have a distinct morphology and serve as a dispersal mechanism for the organism. These cyanobacteria are common inhabitants of freshwater environments, where they are subjected to a variety of fluctuating conditions, including levels of dissolved metal ions. The present study represented an initial investigation of the effects of increasing metal ion concentrations on Calothrix as assessed ultrastructurally by transmission electron microscopy and through alterations observable by light microscopy and growth studies. Exposure of filaments to various levels of the alkaline earth cations Ca2+, Mg2+, Sr2+, and Ba2+ led to various changes in structure, indicating effects on the organism's physiology. These included perturbation of cell envelope layers, such that the formation of outer membrane vesicles was enhanced, alteration to the patterns and abundance of sheath material formed, alteration of thylakoid (photosynthetic) membrane structure, and inhibition of hormogonium formation and release. It was interesting to note that even cations that are not typically thought of as toxic (Ca2+ and Mg2+) could have profound effects on the cells to the extent of inhibiting growth at the maximum levels used in this study (5 mM), which are below these often found in natural environments. These results give an indication that the presence of metal ions in natural environments can have an important influence on the structural and growth characteristics of commonly found cyanobacteria to the extent of making them appear, on a macroscopic basis, as different organisms entirely. This puts a note of caution on future field observations and interpretations of the effects of pollutants on natural microbial communities.Key words: cyanobacteria, metals, ultrastructure.

scholarly journals A Novel Calix[4]Crown-Based 1,3,4-Oxadiazole as a Fluorescent Chemosensor for Copper(II) Ion Detection

2021 ◽  
Vol 9 ◽  
Author(s):  
Chun Sun ◽  
Siyi Du ◽  
Tianze Zhang ◽  
Jie Han
Keyword(s):  
Metal Ions ◽  
Metal Ion ◽  
Earth Metal ◽  
Transition Metal Ions ◽  
Fluorescent Chemosensor ◽  
Acetonitrile Solution ◽  
Electron Transfer Mechanism ◽  
Alkaline Earth Metal Ions ◽  
Photo Induced Electron Transfer ◽  
Metal Ion Exchange

The synthesis and characterization of a novel florescent chemosensor 1 with two different types of cationic binding sites have been reported in this work, which is a calix[4]crown derivative in 1,3-alternate conformation bearing two 2-phenyl-5-(4-dimethylaminopyenyl)-1,3,4-oxadiazole units. The recognition behaviors of 1 in dichloromethane/acetonitrile solution to alkali metal ions (Na+ and K+), alkaline earth metal ions (Mg2+ and Ca2+), and transition metal ions (Co2+, Ni2+, Zn2+, Cd2+, Cu2+, Mn2+, and Ag+) have been investigated by UV-Vis and fluorescence spectra. The fluorescence of 1 might be quenched selectively by Cu2+ due to the photo-induced electron transfer mechanism, and the quenched emission from 1 could be partly revived by the addition of Ca2+ or Mg2+; thus, the receptor 1 might be worked as an on–off switchable fluorescent chemosensor triggered by metal ion exchange.

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