Pairs Of Metal Ions Research Articles

Catena-Poly[[[diaqua[3-(pyridin-4-yl)benzoato-κ2O,O′]gadolinium(III)]-bis[μ-3-(pyridin-4-yl)benzoato-κ2O:O′]] monohydrate

In the title coordination polymer, {[Gd(C12H8NO2)3(H2O)2]·H2O}n, the GdIII ion is ligated by one bidentate carboxyl­ate group, four monodentate bridging carboxyl­ate O atoms and two water mol­ecules. The resulting GdO8 polyhedron approximates to a square anti­prism. The bridging ligands link the metal ions into a [100] chain, with each pair of adjacent metal ions being bridged by two ligands. Inter-chain O—H⋯O and O—H⋯N hydrogen bonds help to establish the packing.

The role of the bridging group in exchange coupling in dinuclear homo- and heterometallic Ni(ii) and Co(ii) complexes with oxalate, oxamidate and dithiooxamidate bridges

Six homodinuclear and two heteronuclear complexes Tp(Np)Co-C(2)O(4)-CoTp(Np) (1), Tp(Np)Co-C(2)O(4)-NiTp(Cy) (2), Tp(Cy)Ni-C(2)O(4)-NiTp(Cy) (3), Tp(Np)Co-C(2)O(2)(NH)(2)-CoTp(Np) (4), Tp(Cy)Ni-C(2)O(2)(NH)(2)-NiTp(Cy) (5), Tp(Np)Co-C(2)S(2)(NH)(2)-CoTp(Np) (6), Tp(Np)Co-C(2)S(2)(NH)(2)-NiTp(Cy) (7), Tp(Cy)Ni-C(2)S(2)(NH)(2)-NiTp(Cy) (8) (Tp(Np) = tris(3-neopentylpyrazolyl)borate, Tp(Cy) = tris(3-cyclohexylpyrazolyl)borate), were synthesized and characterized by mass spectrometry, electronic spectroscopy and X-ray crystallography. These compounds possess similar molecular structures, with the metal ions linked by bridging oxalate (1-3), oxamidate (4 and 5) or dithiooxamidate (6-8) ions. The heteronuclear nature of compounds 2 and 7 was additionally confirmed by high-resolution mass spectrometry. The magnetic properties of the Co(2+) complexes were modelled taking into account zero-field splitting of this ion, yielding D-values for Co(2+) in the range -17(1) to -50(1) cm(-1). All the metal ion pairs in compounds 1-8 are antiferromagnetically-coupled, with J values between -10.0(1) and -45.0(2) cm(-1) (via the exchange Hamiltonian Ĥ(ex.) = -2JŜ(1)Ŝ(2)) and |J| increasing in the order oxalate < oxamidate < dithiooxamidate. This tendency can be attributed to greater M-S bond covalency compared to M-N or M-O bonds (M = Co(2+) and Ni(2+)). It was found that this antiferromagnetic coupling of Co(2+) and Ni(2+) ions through oxalate is more efficient for these tris(pyrazolyl)borate complexes than for similar oxalate-bridged systems with neutral aliphatic amine ligands.

Syntheses, crystal structures and supramolecular topologies of nickel(II)–s/p/d10/NH4+ complexes derived from a compartmental ligand

The syntheses, characterization and crystal structures of ten complexes of composition [{NiIILLiI(H2O)2}{NiIIL}2](ClO4) (1), [NiIILNaI(ClO4)(CH3OH)] (2), [(NiIIL)2NaI](BPh4)·CH3COCH3 (3), [(NiIIL)2RbI](BPh4)·CH3COCH3 (4), [(NiIIL)2CsI](ClO4)·CH3CN (5), [{NiIILMgII(H2O)3}{NiIIL}2](ClO4)2 (6), [NiIILCaII(NO3)2(H2O)]·1.5H2O (7), [NiIILCdII(NO3)2]·CH3CN (8), [NiIILPbII(NO3)2] (9) and [(NiIIL)2(NH4)](PF6) (10) are reported, where H2L = N,N′-ethylenebis(3-ethoxysalicylaldimine). The crystal systems and space groups are: triclinic Pī for 1, 4, 5 and 8, monoclinic P21/c for 2, 3, 7 and 9, monoclinic C2/c for 6 and monoclinic P21/n for 10. In 1–10, the salen type N2O2 compartment of [L]2− is occupied by a NiII ion, while the larger and open O(phenoxo)2O(ethoxy)2 compartment interacts with LiI in 1, NaI in 2 and 3, RbI in 4, CsI in 5, MgII in 6, CaII in 7, CdII in 8, PbII in 9 and NH4+ in 10. Compounds 1 and 6 are [2 × 1 + 1 × 2] tetrametallic cocrystals of one diphenoxo-bridged dinuclear NiIILiI (for 1) and NiIIMgII (for 6) unit and two mononuclear [NiIIL] moieties. Compounds 2, 7, 8 and 9 are diphenoxo-bridged dinuclear NiIINaI, NiIICaII and NiIICdII and NiIIPbII systems, respectively. On the other hand, compounds 3, 4 and 5 are trinuclear NiII2NaI, NiII2RbI and NiII2CsI systems, respectively, in which each of the two adjacent pairs of metal ions is diphenoxo-bridged. The rubidium(I) and cesium(I) analogues are also double-decker sandwich systems. The ammonium ion in [(NiIIL)2(NH4)](PF6) (10) is sandwiched in between two [NiIIL] moieties due to hydrogen bonds between ammonium hydrogen atoms and O4 compartments. Weak interaction assisted following self-assemblies are observed: dimeric in 1 and one-dimensional in 10 due to Ni⋯Ni weak interaction; one-dimensional in 2 due to C–H⋯π and O–H⋯O hydrogen bonds; nice cyclic topology in 5 due to Ni⋯Ni interaction and C–H⋯O hydrogen bonds; one-dimensional in 6 due to Ni⋯Ni interaction and C–H⋯O hydrogen bond; one-dimensional in 8 due to π···π stacking.

JCE Classroom Activity Connections: NaCl or CaCl2, Smart Polymer Gel Tells More

This classroom activity connection demonstrates the differences between the effects of NaCl (a salt of monovalent metal ions) and CaCl2 (a salt of polyvalent metal ions) on swollen superabsorbent polymer gels. Being ionic compounds, NaCl and CaCl2 both collapse the swollen polymer gels. The gel contracted by NaCl reswells in deionized water, but that contracted by CaCl2 does not reswell. The CaCl2 contracted gel is subsequently immersed in concentrated NaCl solution to reverse the ion exchange. The Ca2+ ions in the contracted gel are released, and Na+ ions are redistributed in the polymer network. The ion-exchange cycle is accomplished and the water-absorbing ability of the gel is recovered. Other compound pairs of monovalent versus polyvalent metal ions involving LiCl, NaCl, KCl, CaCl2, BaCl2, and ZnCl2 give similar results.

Guest editor's tribute to Friedrich Baucke on the occasion of his 80th birthday

For many years, Dr. Baucke has been a well-known figure at conferences concerned with the electrochemistry of glasses and related materials. I first met Dr. Baucke in 1972 at a EUCHEM Molten Salts conference in Cirencester, England. We discussed several topics, but mainly the chemistry of glass melts and their acid–base properties, and he suggested that I should visit him at his laboratory at Jenaer Glaswerk Schott und Genossen in Mainz, Germany. This was the start of several visits to Schotts when initially I worked with both Dr. Baucke and his electron microscopist colleague, Dr. H. Bach. These two Schott employees had just been pursuing groundbreaking work, that later established, for the first time, the real mechanism of the glass electrode. The excellent quality of this work was recognised by the American Ceramic Society in conferring on both workers the Morey Award in 1978. Dr. Baucke had joined Schotts in 1968, after returning from the USA, where he had held a post-doctoral fellowship at Berkeley, University of California. Erich Schott, son of Otto Schott (who founded the original Schott company in Jena), required him to establish a research laboratory that would specialise in the electrochemistry of glass, in both the vitreous and the molten state. Naturally, his tasks encompassed a much wider role, and included work on thin films deposited onto glass and also the development of electrochromic devices. During the 1960s and early 1970s, the atmosphere at Schotts encouraged scientists of the calibre of Dr. Baucke to pursue creative ideas in addition to dealing with the more day-to-day problems that arose in the factory. His laboratory, indeed, had an academic atmosphere, although a visitor was always aware that ‘both feet were on the ground’. Some of Dr. Baucke's academic interests overlapped certain areas of my own research (jointly being developed with my colleague, Prof. Malcolm Ingram), and it became appropriate that he should be appointed as an Honorary Visiting Research Fellow in the University of Aberdeen. For more than 20 years, he made regular visits to Aberdeen and it was always a great pleasure when he presented a lecture detailing his latest work at Schotts. He established himself as a popular figure in the Chemistry Department, equally with the staff and research students. During my visits to his laboratory in Mainz, we discussed many ideas. A number of research programmes were devised, such as on the transport of ions through glass and also the redox reactions of metal ion pairs that are important in the manufacture of glass. Work was also undertaken on certain fundamental aspects of electrochromism. When Dr. Baucke retired from Schotts, he handed over to his successor a first-class laboratory that included a loyal team of well-trained personnel. However, retirement did not Dr. Friedrich G. K. Baucke, DSc

Superheated Water Ion-Exchange Chromatography: An Experimental Approach for Interpretation of Separation Selectivity in Ion-Exchange Processes

Cation-exchange selectivity for alkali and alkaline-earth metal ions and tetraalkylammonium ions on a strongly acidic sulfonic acid cation-exchange resin has been investigated in the temperature range of 40-175 degrees C using superheated water chromatography. Dependence of the distribution coefficient (ln KD) on the reciprocal of temperature (1/T) is not linear for most of the ions studied, and the selectivity coefficient for a pair of alkali metal ions or that of alkaline-earth metal ions approaches unity as temperature increases. On the other hand, the retention order of tetraalkylammonium ions is reversed at 160 degrees C or above when eluted with Na2SO4 aqueous solution and the larger ions are eluted faster than the smaller ones contrary to the retention order obtained at ambient temperature. The change in ion-exchange selectivity with temperature observed with superheated water chromatography has been discussed on the basis of the effect of temperature on hydration of the ions and specific adsorption or distribution of ionic species between the external solution and ion-exchange resin. In superheated water, the electrostatic interaction or association of the ions with the fixed ion becomes a predominant mechanism resulting in different separation selectivity from that obtained at ambient temperature.

Predesigned Hexanuclear CuII and CuII/NiII Metallacycles Featuring Six‐Node Metallacoronand Structural Motifs

Crowning glory: The assembly of CuII or CuII and NiII and a new 1,4-aryl-linked bis(triketonato) ligand designed to adopt a ‘bent’ configuration leads to unusual Cu6−nNinL3 (n=0, 3) metallacycles that feature unique hexanuclear metallacoronand structural motifs. In the case of the hexanuclear CuII species, strong antiferromagnetic interactions exist between proximate pairs of metal ions in each structure.

Role of Coordinated Water and Hydrogen‐Bonding Interactions in Stabilizing Monophenoxido‐Bridged Triangular CuIIMII­CuII Compounds (M = Cu, Co, Ni, or Fe) Derived from N,N′‐Ethylenebis(3‐meth­oxysalicylaldimine): Syntheses, Structures, and Magnetic Properties

AbstractThe syntheses, structures, and magnetic properties of the trinuclear triangular compounds [{CuIIL1}2CuII(H2O)2](ClO4)2·H2O (1) and [{CuIIL1}2MII(H2O)2](ClO4)2 {M = Ni (2), Co (3), Fe (4)} derived from N,N′‐ethylenebis(3‐methoxysalicylaldimine) (H2L1) are described. Compound 1 crystallizes in the monoclinic P21/n space group, while the crystal system for the isomorphous compounds 2–4 is monoclinic P21/c. In the cations of these compounds, two copper(II) ions occupy the salen type N2O2 cavity of two [L1]2– ligands, while one phenoxido and one methoxy oxygen atom of each of these two [CuIIL1] moieties coordinate to a central metal ion, which results in the formation of the trinuclear CuII2MII systems in which the two pairs of central···terminal metal ions are monophenoxido‐bridged. In addition, to the two phenoxido bridges, the central metal ion is coordinated to two methoxy and two water oxygen atoms. The coordinated water molecules are strongly hydrogen bonded to the phenoxido and methoxy oxygen atoms. The presence of the coordinated water molecules and the interaction of these water molecules with the phenoxido and methoxy oxygen atoms are proposed to be the governing factors for the stabilization of the rare example of the monophenoxido‐bridged CuII3 compound 1 and of the first examples of the monophenoxido‐bridged CuII2MII compounds 2–4. The three metal ions define an isosceles triangle. The phenoxido bridge angles in these compounds are significantly obtuse and vary between 121.10(12)° and 129.84(13)°. On the other hand, the trinuclear cores are highly twisted as evidenced from the range of the dihedral angles (58.5–143.7°) between the basal planes of the terminal and the central metal ions. The variable‐temperature (2–300 K) magnetic susceptibilities of compounds 1–4 have been measured. The magnetic data for 1 have been analyzed by using a model of two exchange integrals for the two pairs of adjacent metal ions, while one J value is considered for the other three complexes. The exchange integrals obtained are: CuII3 compound 1: J1 = –97.6 cm–1, J2 = –89.5 cm–1; CuII2NiII compound 2: J = –25.4 cm–1; CuII2CoII compound 3: J = –9.0 cm–1; CuII2FeII compound 4: J = –6.5 cm–1. These moderate to weak antiferromagnetic interactions in 1–4 are related to the twisting of the trinuclear cores. The relative order of the exchange integrals can been understood from the nature of the magnetic orbitals. The structural and magnetic results have been compared with previously reported related compounds.(© Wiley‐VCH Verlag GmbH &amp; Co. KGaA, 69451 Weinheim, Germany, 2009)

A Simple Hydrogen Electrode

This article describes the construction of an inexpensive, robust, and simple hydrogen electrode, as well as the use of this electrode to measure potentials. In the experiment described here the students can measure the reduction potentials of metal–metal ion pairs directly, without using a secondary reference electrode. Measurements with this electrode normally deviate less than 0.03 V from the standard reduction potential given in tables.

Ion Transport to the Interior of Metal−Organic Pyrogallol[4]arene Nanocapsules

Metal ions or ion pairs (silver nitrate shown) are transported to the interior of metal-organic pyrogallol[4]arene nanocapsules via aqueous "gates". This transport has been studied by X-ray crystallography and shows the affinity of the ions to reside deep in the polyaromatic regions of the assemblies.

Mutual Effects of Cationic Ligands and Substrate on Activity of the Na+-Transporting Pyrophosphatase of Methanosarcina mazei

The PP(i)-driven sodium pump (membrane pyrophosphatase) of Methanosarcina mazei (Mm-PPase) absolutely requires Na(+) and Mg(2+) for activity and additionally employs K(+) as a modulating cation. Here we explore relationships among Na(+), K(+), Mg(2+), and PP(i) binding sites by analyzing the dependency of the Mm-PPase PP(i)-hydrolyzing function on these ligands and protection offered by the ligands against Mm-PPase inactivation by trypsin and the SH-reagent mersalyl. Steady-state kinetic analysis of PP(i) hydrolysis indicated that catalysis involves random order binding of two Mg(2+) ions and two Na(+) ions, and the binding was almost independent of substrate (Mg(2)PP(i) complex) attachment. Each pair of metal ions, however, binds in a positively cooperative (or ordered) manner. The apparent cooperativity is lost only when Na(+) binds to preformed enzyme-Mg(2+)-substrate complex. The binding of K(+) increases, by a factor of 2.5, the catalytic constant, the Michaelis constant, and the Mg(2+) binding affinity, and these effects may result from K(+) binding to either one of the Na(+) sites or to a separate site. The effects of ligands on Mm-PPase inactivation by mersalyl and trypsin are highly correlated and are strongly indicative of ligand-induced enzyme conformational changes. Importantly, Na(+) binding induces a conformational change only when completing formation of the catalytically competent enzyme-substrate complex or a similar complex with a diphosphonate substrate analog. These data indicate considerable flexibility in Mm-PPase structure and provide evidence for its cyclic change in the course of catalytic turnover.

Magnetic structure and analysis of the exchange interactions inBiMO(PO4) (M = Co, Ni)

The magnetic structures of the two bismuth oxy-phosphate compoundsBiMPO5 (M2+ = Ni2+,Co2+) have been determined by neutron powder diffraction using group theory analysis as apreliminary tool. Both compounds adopt a monoclinic crystal structure (S.G.P 21/n,a = 7.1642(2) Å,b = 11.2038(3) Å,c = 5.1740(2) Åand β = 107.296(2)° for Ni2+ and a = 7.2441(1) Å, b = 11.2828(1) Å, c = 5.2258(1) Åand β = 107.841(1)° for Co2+). The refinement of the magnetic structures belowTN = 17.5 and 15 K,respectively, for both compounds show that the magnetic structure is characterized by the propagationvector k = (−1/2, 0, 1/2), with components given with respect to the reciprocal lattice of the nuclear structure. Thismeans a magnetic unit cell that is a multiple of the nuclear cell. The magnetic structure isconstituted of ferromagnetic pairs of metal ions antiferromagnetically coupled withindouble chains. The relative strength of the intra and inter double chains exchangeinteractions has been examined by establishing a theoretical magnetic phase diagram. Mostof the interactions come from M–O–O–M super–super-exchange paths. At its ground state,BiNiPO5 shows a nearly collinear arrangement of magnetic moments withm1.5 K = 2.13(3) μB/Ni. Due to the strongmagnetic anisotropy of Co2+ (m1.5 K = 3.52(3) μB/Co), the collinear character is largely lost while the magnetic structure remainsanalysable on the basis of the greatest isotropic component of the local moments.

Pre-concentration and separation of heavy metal ions by chemically modified waste paper gel

Iminodiacetic acid was immobilized on waste paper by chemical modification in order to develop a new type of adsorption gel for heavy metal ions. Adsorption behavior of the gel was investigated for a number of metal ions, specifically Cu(II), Pb(II), Fe(III), Ni(II), Cd(II), and Co(II) at acidic pH. From batch adsorption tests, the order of selectivity was found to be as follows: Cu(II) ≫ Fe(III) > Pb(II) > Ni(II) ≫ Co(II) > Cd(II). Column tests were carried out for pairs of metal ions to understand the separation and pre-concentration behavior of the gel. It was found that mutual separation of Ni(II) from Co(II) and that of Pb(II) from Cd(II) can be achieved at pH 3. Similarly, selective separation of Cu(II) from Cu(II)–Fe(III) and Cu(II)–Pb(II) mixtures at pH 1.5 and 2, respectively, was observed by using this new adsorption gel. In all cases, almost complete recovery of the adsorbed metal was confirmed by elution tests with HCl.

Application of Gaussian Multi-Peak Fitting to Radial Distribution Function

Aqueous structures with salt to water molar ratios of 1∶30 (Rb2SO4) and 1∶14 (Cs2SO4) were measured by X-ray scattering of synchrotron radiation. The radial distribution functions (RDF) of the two example solutions were obtained by analyzing the scattering data. RDF overlapped peaks near the first hydration shell were dealt with Gaussian multi-peak fitting. The fitting data were agreed well with the experimental data. The adscription of every fitting peak was determined by comparing the fitting data with hydrated ion and crystal structure data reported in literatures. The analysis of fitting result indicates that the coordination number of Rb+ and Cs+ is six in the first hydration shell, and the spatial structures are both distorted octahedrons. The contact ion pairs of metal ions with sulphate ion exist in two solutions where the characteristic distances of Rb—S and Cs—S were determined to be 0.407 and 0.427 nm, respectively. The study demonstrated that multi-peak fitting was useful for interpreting the hydrated structure of ions.

Preparation and Analytical Properties of Amphoteric Chelating Resin

The chelating ion exchange resin AFM was synthesized by condensation of anthranilic acid with formaldehyde and m‐cresol in DMF media at 100 oC ± 6°C. The identification of resin structure was performed by elemental and FTIR analysis. The thermodynamic parameters such as activation energy (Ea), entropy (S*), enthalpy (H*) and free energy (G*) for thermal decomposition were calculated from thermal data. The morphology of AFM resin shows transition material between crystalline and amorphous phase. The rate of exchange was rapid. i.e. t1/2 &lt; 22 min for Pb(II) and pH dependence of exchange of metal ions on the resin has been determined for several metal ions [Ni(II), Cu(II), Zn(II), Cd(II) and Pb(II)]. Successive separations and recovery of some pair of metal ions [Pb(II)‐Cd(II), Pb(II)‐Zn(II) and Zn(II)‐ Cu(II)] have been performed by using distribution coefficient (Kd).

Hydrothermal synthesis, crystal structures and fluorescence properties of three novel frameworks constructed with mixed ligands of isophthalic acid (1,3-BDC) and 2,3-di-2-pyridylquinoxaline (Dpdq): [M(1,3-BDC)(Dpdq)(H 2O) m] · nH 2O (M = Co II, Cd II or Zn II)

Three novel metal–organic frameworks [M(1,3-BDC)(Dpdq)(H 2O) m ] · nH 2O, (M = Co II ( 1), Cd II ( 2) or Zn II ( 3); m = 0, 1; n = 0, 1, 2, respectively) have been obtained from hydrothermal reactions of three different metal(II) nitrates with the same mixed ligands [isophthalic acid (1,3-BDC) and 2,3-di-2-pyridylquinoxaline (Dpdq)], and structurally characterized by elemental analyses, IR spectroscopy, and single-crystal X-ray diffraction analyses. Single-crystal X-ray analyses show that each pair of metal ions are bridged by various coordination modes of 1,3-BDC ligands to form left- and right-handed helical chains in 1, linear chains in 2, and double chains in 3, respectively. N-containing flexible ligand Dpdq takes a chelating coordination mode acting as terminal ligand. In the compound 1, adjacent left- and right-handed helical chains are packed through hydrogen bonds to form a two-dimensional (2-D) structure. In the compounds 2 and 3, adjacent chains are further linked by hydrogen bonds and/or π–π stacking interactions to form a three-dimensional (3-D) distorted hexagon meshes supramolecular framework for 2 and a ZnS-related three-dimensional (3-D) topology for 3, respectively. The different structures of compounds 1– 3 illustrate that the influence of the metal ions in the self-assembly of polymeric coordination architectures. In addition, compounds 2 and 3 exhibit blue emission in the solid state at room temperature.

Polyfunctional Inorganic−Organic Hybrid Materials: An Unusual Kind of NLO Active Layered Mixed Metal Oxalates with Tunable Magnetic Properties and Very Large Second Harmonic Generation

Mixed M(II)/M(III) metal oxalates, as "stripes" connected through strong hydrogen bonding by para-dimethylaminobenzaldeide (DAMBA) and water, form an organic-inorganic 2D network that enables segregation in layers of the cationic organic NLO-phore trans-4-(4-dimethylaminostyryl)-1-methylpyridinium, [DAMS+]. The crystalline hybrid materials obtained have the general formula [DAMS]4[M2M'(C2O4)6].2DAMBA.2H2O (M = Rh, Fe, Cr; M' = Mn, Zn), and their overall three-dimensional packing is non-centrosymmetric and polar, therefore suitable for second harmonic generation (SHG). All the compounds investigated are characterized by an exceptional SHG activity, due both to the large molecular quadratic hyperpolarizability of [DAMS+] and to the efficiency of the crystalline network which organizes [DAMS+] into head-to-tail arranged J-type aggregates. The tunability of the pairs of metal ions allows exploiting also the magnetic functionality of the materials. Examples containing antiferro-, ferro-, and ferri-magnetic interactions (mediated by oxalato bridges) are obtained by coupling proper M(III) ions (Fe, Cr, Rh) with M(II) (Mn, Zn). This shed light on the role of weak next-nearest-neighbor interactions and main nearest-neighbor couplings along "stripes" of mixed M(II)/M(III) metal oxalates of the organic-inorganic 2D network, thus suggesting that these hybrid materials may display isotropic 1D magnetic properties along the mixed M(II)/M(III) metal oxalates "stripes".

Mixing effects on the protonation of some polycarboxylates in NaCl aq + KCl aq at different ionic strengths

Protonation constants of succinic, 1,2,3-propanetricarboxylic and 1,2,3,4-butanetetracarboxylic anions were determined in NaCl aq + KCl aq mixtures, at three ionic strengths, I = 1.2, 3 and 4.5 mol L −1. Experimental evidences showed that the function log K H = f( y) ( y = [Na +]/([Na +] + [K +])) is not linear, indicating mixing effects on the protonation constants. The Guggenheim zeroth approximation holds that the above function can be written as: log 10 ⁡ K Na – K H = y log 10 ⁡ K Na H + ( 1 − y ) log 10 ⁡ K K H + 4 Δ y ( 1 − y ) where K Na H and K K H represent protonation constants in pure salt solutions and Δ is a parameter that accounts for the mixing effect. Fitting of protonation constants to the above function gives excellent results. The Δ values can be treated in terms of mixing free energy. The behaviour of protonation constants in mixed salt solution can be interpreted by considering the formation of simple and mixed weak complexes; the protonation constants in mixed NaKCl electrolytes can be fitted to the equation: log 10 ⁡ K Na – K H = log 10 ⁡ K K H – log 10 ( 1 + A 1 C Na + A 2 C Na C K ) , where A 1 is a measure of the interaction of Na + with the carboxylic anion and A 2 is proportional to the triple interaction Na +–K +–L z− . Moreover, by using suitable calculation methods, it is possible to calculate the formation constants of simple and mixed ion pairs. As an example, for 1,2,3,4-butanetracarboxylic anion (L 4−), we calculated K(Na + + H i L (4− i)− = NaH i L (3− i)− ) = 0.67, 0.33 and 0.13; K(K + + NaH i L (3− i)− = KNaH i L (2− i)− ) = 1.41, 1.29 and 0.9 for i = 0, 1 and 2, respectively, indicating a significant tendency to form mixed alkali metal ion pairs.

Waste Paper Gel for the Mutual Separation of Heavy Metals

A third of the world's landfill site is covered with paper waste. Although paper is a recyclable resource, it can be recycled as paper only a few times. To utilize the huge amount of spent paper, a sorption material was prepared by immobilizing functional group of iminodiacetic acid for the purpose of removing heavy metals. Remarkable selectivity was observed for some heavy metals. The selectivity order was: Cu (II) >> Fe (III) > Pb (II) > Ni (II) >> Cd (II) > Co (II) . Also, the mutual separation between some metal ion pairs like Ni (II) and Co (II) ; Pb (II) and Cd (II) ; and Cu (II) and Pb (II) was successfully achieved.

Ising limit for a pair of transition metal ions with unquenched orbital angular momenta and its relevance to single molecule magnets

We discuss the magnetic anisotropy of exchange-coupled pair of transition metal ions with unquenched orbital angular momenta in axially distorted octahedral surroundings. The case of ground orbital doublets of the metal ions is shown to give rise to a strong magnetic anisotropy and Ising type effective exchange Hamiltonian. Providing ferromagnetic exchange such Ising interaction is shown to create a magnetization reversal barrier.