Hybrid organic-inorganic framework structures: influence of cation size on metal-oxygen-metal connectivity in the alkaline earth thiazolothiazoledicarboxylates

We report the synthesis of four organic-inorganic frameworks of alkaline earth cations with the organic ligand 2,5-thiazolo[5,4-d]thiazoledicarboxylate (C6N2S2O4(2-), Thz(2-)). Structures with remarkably different connectivities result when Mg(2+), Ca(2+), Sr(2+), and Ba(2+) react with Thz(2-). Mg(Thz)(H2O)4 (I) forms a 1-D coordination polymer in which one carboxylate oxygen on each terminus of the ligand connects individual MgO6 octahedra from their axial positions, while the remaining equatorial sites are coordinated by water molecules. Ca2(Thz)2(H2O)8 (II) forms a 1-D coordination polymer in which dimeric clusters with 7-fold Ca coordination are connected via the ligand in a linear fashion, with a second, uncoordinated Thz(2-) providing charge balance. Sr(Thz)(H2O)3 (III) has 1-D infinite inorganic connectivity built from edge-sharing SrO7N polyhedra having one carboxylate oxygen and one water molecule acting as M-O-M bridges. Ba2(Thz)2(H2O)7 (IV) has 2-D inorganic connectivity based upon face- and edge-sharing BaO9N polyhedra. One carboxylate oxygen and all water molecules act as bridges between each Ba(2+) and its three neighbors. We shall discuss the manner in which the increasing coordination requirements of the cations (MgO6 < CaO7 < SrO7N < BaO9N) lead to an increase in inorganic connectivity through the series.     

Evaluation of alkali and alkaline earth metal cation selectivities of lariat ether amides by electrospray ionization mass spectrometry

Lariat ethers with pendant amide groups have shown promise as new ion sensors because of their selectivity towards particular metal ions. In this study we report alkali and alkaline earth metal binding selectivities of dibenzo-16-crown-5 and fifteen dibenzo-16-crown-5 lariat ether amides (LEAs) as determined by electrospray ionization mass spectrometry (ESI-MS). Additionally, the influence of the acid/base nature of the solution on metal cation selectivity is investigated. The validity of using ESI-MS for determination of selectivities is established by analogous experiments using hosts with known binding constants for the same metal cations and solvent systems. Collisionally activated dissociation (CAD) is used to evaluate the influence of the alkali metal cation binding on the fragmentation of the LEAs.     

Some intense sources of radiation for the alkali and alkaline earth elements

Five new methods are described for the preparation of intense narrow line sources of resonance radiation for the alkali and the alkaline earth elements. Optimum conditions for their preparation and operation are described and their suitability for atomic fluorescence spectrometric purposes has been investigated. The most successful method involves a discharge in flowing atmospheric pressure argon in a quartz tube. A small quantity of the element (or element halide) of interest is suspended in a quartz cup in the discharge stream. The resulting source is applicable to a wide range of relatively involatile elements and, although it is somewhat short lived, it may be recharged readily. Microwave excitation of hollow cathode lamps was not found to be very useful for analytical purposes.     

Thermal stability of alkali metal borates and alkaline earth metal borates

The correlation between the enthalpies of formation of alkali metal and alkaline earth metal borates and the composition of the vapor in equilibrium with their melts is considered. The thermal stabilities of the studied borates have been estimated. A method is suggested for determination of the relative composition of the vapor over borate melts on the basis of their enthalpies of formation.

---

Zusammenfassung Es wurde die Beziehung zwischen den Bildungsenthalpien von Alkali- (Erdalkali-)metallboraten und der Zusammensetzung der sich mit der Schmelze im Gleichgewicht befindlichen Gasphase betrachtet. Die thermische Stabilität der untersuchten Borate wurde geschätzt. Es wurde ein Verfahren entwickelt, die relative Zusammensetzung der Gasphase über Boratschmelzen auf Grund ihrer Bildungsenthalpien zu bestimmen.

     

Distribution of ionic charge carriers and migration barriers in binary alkali silicate glasses

Likely spatial distributions of network-modifying (and mobile) cations in (oxide) glasses are discussed here. At very low modifier concentrations, the ions form dipoles with non-bridging oxygen centres while, at higher levels of modification, the cations tend to order as a result of Coulombic interactions. Activation energies for cation migration are calculated, assuming that the ions occupy (face-sharing) octahedral sites. It is found that conductivity activation energy decreases markedly with increasing modifier content, in agreement with experiment.     

NMR parameters in alkali, alkaline earth and rare earth fluorides from first principle calculations

(19)F isotropic chemical shifts for alkali, alkaline earth and rare earth of column 3 basic fluorides are measured and the corresponding isotropic chemical shieldings are calculated using the GIPAW method. When using the PBE exchange-correlation functional for the treatment of the cationic localized empty orbitals of Ca(2+), Sc(3+) (3d) and La(3+) (4f), a correction is needed to accurately calculate (19)F chemical shieldings. We show that the correlation between experimental isotropic chemical shifts and calculated isotropic chemical shieldings established for the studied compounds allows us to predict (19)F NMR spectra of crystalline compounds with a relatively good accuracy. In addition, we experimentally determine the quadrupolar parameters of (25)Mg in MgF(2) and calculate the electric field gradients of (25)Mg in MgF(2) and (139)La in LaF(3) using both PAW and LAPW methods. The orientation of the EFG components in the crystallographic frame, provided by DFT calculations, is analysed in terms of electron densities. It is shown that consideration of the quadrupolar charge deformation is essential for the analysis of slightly distorted environments or highly irregular polyhedra.     

Automatic ion-exchange chromatograph for analysis of alkali and alkaline earth metal mixtures

A new automatic chromatograph for ultramicro determination of alkali and alkaline earth metals has been developed. It combines a high-sensitivity hydrogen flame-ionization detector with ion-exchange chromatography. Zirconium phosphate was chosen as ion-exchanger.     

Ion chromatographic determination of alkali and alkaline earth metals in mineral waters

Summary The rapid, simultaneous, suppressed ion chromatographic determination of alkali, alkaline earth metals and ammonium in highly mineralized waters has been examined using the novel cation exchange IonPac CS12 column. General ability for the determination of lithium, sodium, ammounium, potassium, magnesium, calcium and strontium in concentrations from a few g to several mg per liter was studied. The relative standard deviations of retention times of all seven cations were below 0.7% and the relative standard deviations of the measurements of peak areas and peak heights were mostly below 5%. Six natural mineral waters of different types were selected for evaluation of the method. It was not possible to determine lithium in the one run and ammonium usually partially coelutes with sodium precluding quantitative determination. Strontium was undetectable because of the necessary dilutions. All the reltionships between peak areas and concentrations or peak height and concentrations were linear and there was also no evidence of the effect of different matrices on the slope of regression lines.     

Titrimetric microdetermination of sulfur in compounds containing alkali or alkaline earth

Summary The titrimetric dry combustion method can be employed for micro-determination of sulfur in organic compounds containing both alkali metal or alkaline earth metal and sulfur.The residue of alkali or alkaline earth sulfate in the boat, formed during the combustion, is fused with 3 to 4 times its weight of boron trioxide, whereby sulfur trioxide is displaced by the boron trioxide.

---

Zusammenfassung Die Bestimmung des Schwefels durch Verbrennung und Titration der gebildeten Schwefelsäure kann mit organischen Verbindungen ausgeführt werden, die Alkalien oder alkalische Erden enthalten.Der Metallsulfate enthaltende Verbrennungsrückstand wird im Schiffchen mit der 3- bis 4fachen Menge Bortrioxyd versetzt. Beim darauffolgenden Erhitzen wird das Schwefeltrioxyd in Freiheit gesetzt.

---

Résumé On peut employer la méthode par combustion à sec et titrage pour le dosage du soufre dans des composés organiques contenant un métal alcalin ou un métal alcalino-terreux.Le résidu de sulfate alcalin ou alcalino -terreux formés pendant la combustion dans la nacelle est fondu avec trois ou quatre fois son poids de trioxyde de bore; l'anhydride sulfurique est déplacé par le trioxyde de bore.

     

Evaluation of column temperature as a means to alter selectivity in the cation exchange separation of alkali metals, alkaline earth metals and amines

The merits of varying column temperature in a cation exchange separation of alkali metals, alkaline earth metals and amines are considered. Increasing the column temperature (up to 60 degrees C) reduced the retention of all cations, but by varying extents. Consequently, selectivity changes were seen, with reversals in elution order in some cases. To ascertain when temperature is most useful as a separation aid, analytes were classed into three groups according to their temperature behaviour: alkali metals; alkaline earth metals; and amines. Adjusting the column temperature caused selectivity changes between analytes in different groups, but no selectivity changes occurred between analytes in the same group. Further, temperature was compared to the addition of modest amounts of acetonitrile as another means to alter selectivity. The benefits of elevated temperature were not just limited to selectivity changes. Improvements in the efficiencies of all analytes were noted at 60 degrees C. This was especially true for the amines which are severely tailed at ambient temperatures.     

Ion-pair chromatography of alkali and alkaline earth ions with the new reagent n-hexylsuccinic acid

Summary Alkali, alkaline earth, zinc and manganese(II) ions are separated by ion-pair chromatography on a LiChrospher RP-18 column with 2 mmol/l n-hexylsuccinic acid as a new ion-pair reagent and 1 mmol/l oxalic acid in the eluent and are detected by conductivity. The separation mechanism is discussed, the applicability for wine and mineral water samples including comparison to AAS results are presented.     

The application of extraction chromatography for analysis of alkali and alkaline earth uranates

A method for rapid analysis of alkali and alkaline earth uranates is proposed. The method is based on the use of an HDEHP extraction chromatographic column, which makes possible quantitative separations of alkali or alkaline earth ions from macroamounts of uranium (VI).     

Transport of alkali and alkaline earth cations by a crown ether-alkylphosphoric acid system

Abstract

Competitive transport of alkali and alkaline earth cations has been carried out by using a mixed carrier system composed of dibenzo-14-crown-4 and bis(2-ethylhexyl)phosphoric acid. In the absence of crown ether, bis(2-ethylhexyl)phosphoric acid transported alkaline earth cations with high selectivity. The combination of dibenzo-14-crown-4 and bis(2-ethylhexyl)phosphoric acid showed a synergistic enhancement in lithium transport, and the enhancement effect was not apparent in transport of other cations. On the other hand, the mixed carrier systems consisting of dibenzo-14-crown-4 and dodecylbenzenesulfonic acid, and of dibenzo-14-crown-4 and 1-bromohexadecanoic acid exhibited the enhancement effects both in lithium transport and in sodium transport. The formation of the synergistic complex was analyzed by using fast atom bombardment mass spectrometry.