Search

Six heterometallic Zn(II) coordination polymers, Zn(H2O)3(FNA) (1), [NH4]2[Zn(H2O)2(FNA)2] (2), [ZnNa2(FNA)2]·3H2O (3), [ZnK2(FNA)2]·H2O (4), [ZnRb2(FNA)2]·2H2O (5) and [ZnMg(FNA)2]·4H2O (6) (H2FNA = 4-nitrobenzene-1,2-dicarboxylic acid), were synthesised by introducing different alkali/alkaline earth (AeI/AeII) metals. These complexes exhibit diverse structures with the different AeI/AeII metals used and distinct ligand coordination modes the ions provide. For 1 and 2, the Zn(II) centres with distorted octahedra are connected by FNA to form 1-D chain structures. The Zn(II) centres in 3–6 with distorted tetrahedra are linked by FNA to form 2-D anionic grid layers. For 3–5, these 2-D anionic grid layers are connected by alkali metal (Na, K and Rb) with the O–AeI–O connectivity to exhibit 3-D framework structures, while 6 features a 2-D Zn–Mg network. Luminescence properties of 1–6 have been investigated.

Based on density functional calculations (B3LYP/LANL2DZp (LANL2DZp=LANL2DZ augmented with polarization functions on non-hydrogen atoms)), the selectivity of the {2}-metallocryptand [Fe2L3] (L2− = 2,6-dibutane-1,3-dionylpyridine dianion) was investigated and the experimentally known K+, Sr2+ and Ba2+ cation selectivity rationalized. The rigidity of L2−, visible in the small torsion angles compared to previously investigated classical organic cryptands, can be identified as the origin of this discrimination. Derived from the hosted alkali and alkaline earth cations, the size of the {2}-metallocryptand’s [Fe2L3] cavity is analogous to the cryptand [2.2.phen]. Additionally, the quantum chemical calculations identified the {2}-metallocryptand [Fe2L3] as the first experimentally verified metalloproton sponge (calculated (B3LYP/LANL2DZp) proton affinity −259.8 kcal mol−1). This high gas-phase proton affinity clearly explains why empty [Fe2L3] was never observed, and only [(HN)3Fe2L3]3+ or [MFe2L3]m+ are known.

Three new alkaline earth metal complexes, [Ca2(H2O)8(μ2-HTBA-O,O′)2(HTBA-O)2] (1), [Ca(H2O)5(HTBA-O)2]·2H2O (2), and [Sr(H2O)4(μ2-HTBA-O,S)2]n (3) (H2TBA = 2-thiobarbituric acid, C4H4N2O2S), were synthesized and characterized by FT-IR spectroscopy, TG-DSC, and single-crystal and powder X-ray diffraction analysis. The single-crystal X-ray diffraction data revealed that 1 and 2 are discrete structures, whereas 3 is a polymer. In 1 and 2, Ca2+ is seven-coordinate and forms a monocapped trigonal prism. In 1, the prisms are pairwise connected with the assistance of two [μ2-HTBA-O,O′]− ligands. In 3, Sr2+ is coordinated by four monodentate HTBA− via S or O donors and four waters, with the formation of a distorted square antiprism. The antiprisms are connected by μ2-O,S bridging HTBA−. Hydrogen bonding involving coordinated water and π–π interactions plays an important role in construction of the supramolecular 3-D structures in 1–3. Infrared spectroscopic data supported the structural data. The thermal stabilit...

In neutral and acidic solution, homonuclear s-block metal complexes [Sr2(1,3-pdta)(H2O)3.5] n (1), {[Ba2(1,3-pdta)(H2O)6]·H2O} n (2), {[Sr(1,3-H2pdta)]·(H2O)} n (3), and [Ba(1,3-H2pdta)(H2O)3] n (4) {1,3-H4pdta=1,3-propanediamine-N,N,N′,N′-tetraacetic acid, CH2[CH2N(CH2CO2H)2]2} were isolated. In 1 and 2, hexadentate 1,3-pdta joins two metal ions via the diamine chain. In 3 and 4, the nitrogens of 1,3-H2pdta were protonated and show no coordination. There is no coordinated water in 3, unusual coordination for strontium. In 4, the coordination number is nine and there are three coordinated waters for each barium. One carboxy group of pdta is free without coordination. Thermal decomposition shows that temperatures of ligand elimination start at 408, 423, 298, and 250 °C for 1–4, respectively. Acidic condition is favorable for preparation of metal oxide at low temperature.

Hydrothermal reactions of alkaline earth metal nitrates with two ditopic carboxylic acids, trans-1,4-cyclohexanedicarboxylic acid (H2CDC) and 1,4-phenylenedipropionic acid (H2PDP), generate two 3-D metal–organic frameworks (MOFs) with empirical formulas [Ca(CDC)(H2O)2]·H2O (1) and [Sr(PDP)(H2O)] (2), respectively. Compound 1 consists of Ca–COO–H2O chains cross-linked through the –C6H10– spacers of the CDC anions, showing slightly open 1-D channels along the crystallographic c axis that accommodate the guest water molecules. Compound 2 exhibits a MOF consisting of wavy 2-D Sr–COO–H2O nets linked by –CH2CH2C6H4CH2CH2– tethers, and the condensed structure appears to arise from conformational flexibility of the ligand spacer.

Alkaline earth metal nitrate coordination compounds with hexamethylenetetramine, [ ]], have been synthesized and characterized by elemental and thermal analysis, IR spectroscopy, and X-ray crystallography. Introduction of hmta to the outer coordination sphere allows changing of the inner coordination sphere giving the dinuclear coordination compounds of calcium and strontium nitrates. The compounds are air stable at room temperature and soluble in water. The ions and molecules are assembled via , and hydrogen bonds. Thermal analyses show crucial differences in decomposition processes (especially in the case of 3 that finally decomposes to the mixture of SrO and Sr(NO3)2). The IR spectrum of 3 shows lack of bending vibration (present in the spectra of the respective pure salts at 741–759 cm−1), while in 2 this band is weakened and shifted to lower frequencies. Only the IR spectrum of 3 clearly exhibits bands originating from overtones and combination bands (in the spectral range 2073–2474 cm−1).

Three barbital-based alkaline earth metal complexes, [Ca(Barb)2] · 3H2O (1), [Ba2H(Barb)5] (2) and [Mg(Barb)2] · 2H2O (3) (Barb = 5,5-diethyl barbiturate sodium salt), were synthesized and characterized with elemental analysis, thermal analysis, and infrared, Raman, ultraviolet, and NMR (1H and 13C) spectroscopies. Single-crystal X-ray diffraction studies reveal that 2 is a dimer. Each barium(II) is surrounded by an O7N2 donor set in an approximate monocapped square antiprism with Ba–O distances ranging from 2.6512(14) to 2.9168(15) A and Ba–N distances of 2.7601(15) and 3.2558(17) A. The complex forms polymeric networks in the solid state with different coordinating abilities of O and N donors and N–H···O hydrogen bonds. The antimicrobial activities of 1–3 were observed against different gram-positive and gram-negative bacteria, yeast, and molds. Variable antimicrobial activity against the different bacteria strains was observed and compared with that of standard antibiotics; minimum inhibitory concentra...

Four alkaline earth metal-organic frameworks, [Mg(H2O)6] · (pmtz)2 (1), [Ca(pmtz) 2(H2O)3] · H2O (2), [Sr(pmtz)2(H2O)4] (3), and [Ba(pmtz)2(H2O)2] · 4H2O (4) [pmtz = 5-(pyrimidyl)tetrazole anion], were synthesized and characterized by elemental analysis, IR spectroscopy, and X-ray crystallography. The crystal structures reveal that 1–3 are mononuclear while 4 displays a 2-D layer structure by bis(bidentate) bridging pmtz−. The luminescence properties of 1–4 were investigated in the solid state at room temperature.

A new 3-D wheel-like calcium–cobalt phosphotungstate, Na6Ca3[Ca2(H2O)6Co9(OH)3(H2O)6(HPO4)2(PW9O34)3], is reported and characterized by IR, UV, and single-crystal X-ray diffraction. The crystal structure consists of an infinite 3-D array of [Ca2(H2O)6Co9(OH)3(H2O)6(HPO4)2(PW9O34)3]12− anions (1) connected by sodium and calcium metal cations. The novel feature is the presence of two Ca2+, bonded to oxygen of HPO4− and to H2O spanning opposite sides in the complex anion. The stability of the crystalline product and its morphology were studied by SEM-EDX and DSC techniques.

We present a barium metal–organic framework {[Ba(in)(H2O)6][in]} ∞ prepared via a simple acid–base reaction between BaCO3 and inH (inH = 4-pyridinecarboxylic acid). The complex crystallizes in the monoclinic space group P21/c (a = 6.2592(18), b = 44.289(12), c = 7.2754(15); α = γ = 90, β = 118.890(18); V = 1765.8(8) A3) displaying an unusual ion association mode with half of the anions metal-bound, whereas the others are associated via a hydrogen-bonded and π ··· π stacking network. Among the coordinated anions, the carboxylate functionalities bridge the metal centers.

Eight alkaline and alkaline-earth compounds derived from 2,4-dinitroimidazole (2,4-HDNI) were synthesized and characterized by elemental analysis, FT-IR, and TG–DSC, of which K(2,4-DNI) (1), Rb(2,4-DNI)(2,4-HDNI)(H2O)2 (2), and Ba(2,4-DNI)2(H2O)4 (3) were characterized by single-crystal X-ray diffraction analysis. All the three compounds were crystallized from water, but 1 was an anhydrate. The coordination number in 1 and 3 is 10, but in 2 is 9. The 2,4-DNI adopts either η3, η2, or η1 coordination modes depending on the metal cation. In 3, there is an inversion center located on the metal. Only in 2 does water play an important role for the construction of the structure; in 3 it is a hydrogen bonding participant. TG–DSC analyses of 1 were also performed, and non-isothermal decomposition reaction kinetics were obtained.

A new polyoxometalate based on saturated Wells-Dawson polyanions and calcium cations, H2[Ca2(P2W18O62)(H2O)5] · 7.5H2O (1), has been synthesized in aqueous solution and characterized by single-crystal X-ray diffraction and IR. Compound 1 is a new example of 3D framework based on Wells-Dawson anions that act as chelate ligands to coordinate with calcium cations. Cyclic voltammetry reveals that the pH of the supporting electrolytic solution has a marked effect on the electrochemical behavior.

Six new alkaline-earth metal compounds derived from dinitropyridone ligands (3,5-dinitropyrid-2-one, 2HDNP; 3,5-dinitropyrid-4-one, 4HDNP and 3,5-dinitropyrid-4-one-N-hydroxide, 4HDNPO) were synthesized and characterized by elemental analysis, FT-IR and partly by powder XRD, TG-DSC and X-ray single-crystal diffraction analysis. The structural determination revealed that one molecule of both magnesium salts (Mg(2DNP)2 · 8H2O, (1), and Mg(4DNP)2 · 6H2O (4)) comprise one cation [Mg(H2O)6]2+ and two anions displaying centro-symmetry with the Mg atom located at the center. Two anions (and crystalline water molecules) are joined by hydrogen bonds. The barium salt Ba(4DNP)2 · 4H2O (5), is a centro-symmetric dimer with each Ba(II) being coordinated by one monodentate ligand anion, two bidentate ligand anions (different coordination pattern) and five water molecules. Another barium salt, Ba(4DNPO)2 · 6H2O (6), is a coordination polymer, the ten-coordinate (BaO10) barium environment comprising four water molecu...

Two one-dimensional linear coordination polymers, [Mg(L) · 4(H2O)] (H2L = olsalazine) and 2 [Ca(L) · 4(H2O)] were obtained from self-assembly of CaCl2 or MgSO4 with olsalazine and their structures determined by single crystal X-ray diffraction. Both complexes are one-dimensional polymers, for complex 1 with crystal data: P2(1)/c, a = 9.5224(18), b = 11.309(2), c = 16.211(3) A, β = 106.648(3)°, V = 1672.6(6) A3, Z = 4, R 1 = 0.0695, wR 2 = 0.2183, for complex 2 with crystal data: P4(3)2(1)2, a = 10.4006(2), b = 10.4006(2), c = 32.0746(10) A, V = 3469.59(14) A3, Z = 8, R 1 = 0.0332, wR 2 = 0.1015. In the complexes, Mg and Ca adopt totally different coordination modes. Alkaline-earth Mg is six-coordinate octahedronal geometry, however, in 2, the local coordination geometry around calcium atom can be best described as a slightly distorted pentagonal bipyramid crystallizing in a homo-chiral space group. Olsalazine in both compounds also adopts dissimilar coordination modes.

Complexes derived from ampicillin (L1) and amoxicillin (L2) with (Mg(II), Ca(II), Zn(II), Cu(II), Ni(II), Co(II), Ce(III), Nd(III), UO2(VI), Th(IV)) were prepared and characterized by elemental analysis, electrical conductivity measurements, magnetic susceptibility, IR, UV/Vis, and thermogravimetry. The formed complexes can be formulated as (ML(H2O)3(NO3) n ) except for Ce(III) which gave (CeL(H2O)3(Cl)2). The 1H NMR spectra of the Zn(II) complexes are compared to spectra of the ligands. The shift (δ) gave information about the chelating center of the ligands. The ligands and the synthesized complexes, derived from some alkali earth and transition metal ions, were tested as antibacterial reagents. The formed complexes had enhanced activity.

A family of magnesium acetylides was prepared by treating Bu2Mg with two equivalents of various alkyne ligands in the presence of different donors. The resulting complexes were examined for the influence of ligand and donors on the spectroscopic and structural properties of the target compounds. The magnesium complexes are compared to the heavier alkaline earth metal analogs. †Dedicated to Peter A. Williams and his contributions to the Journal of Coordination Chemistry.

New alkaline-earth metal cryptates [ML](ClO4)2 · solvent (M = Ca2+, Sr2+, Ba2+; L = 1,4, 12,15,18,26,31,39,42,43,44-undecaazapentacyclo-[13.13.13.16,10.120,24.133,37]-tetratetraconta-4, 6, 8, 10(44), 11,18,20,22,24(43),25,31,33,35,37(42),38-pentadecaene) were synthesized by [2 + 3] template condensation of tris(2-aminoethyl)amine with 2,6-diformylpyridine and characterized by physical methods. The crystal structure of the calcium cryptate was determined. The central atom is nine coordinate with three pyridyl and six imino nitrogen atoms. The coordination polyhedron can be described as slightly distorted tricapped trigonal prism.

Complexes involving the perchlorate, chloride, bromide or iodide salts of the heavy group 2 elements, calcium, strontium or barium, and either 15-crown-5 or 18-crown-6 have been synthesized and their X-ray crystal structures determined. A variety of coordination modes are presented between the crown ether and metal ions.

The structures of dimethylsulfoxide-solvated magnesium and calcium ions have been studied in the solid state and in dimethylsulfoxide solution by X-ray crystallography and large-angle X-ray scattering (LAXS), respectively. The magnesium and calcium ions coordinate six dimethylsulfoxide molecules in both the solid state and solution with mean Mg–O and Ca–O bond distances in solid perchlorate salts of 2.062(4) and 2.303(5) A, respectively. A summary of the coordination chemistry of the hydrated and solvated alkaline earth metal ions shows that beryllium(II) and magnesium ions are tetrahedral and octahedral, respectively, in all solvents studied, while calcium and strontium are eight-coordinated in square antiprismatic fashion in water, but octahedral in dimethylsulfoxide and other organic solvents. Mean M–O bond distances of the hydrated alkaline earth metal ions were used to calculate the ionic radii of the alkaline earth metal ions.

A complexation study concerning the interaction between Ag+, NH+ 4, Li+, Na+, K+, Rb+, Cs+, Mg2+, Ca2+, Sr2+, and Ba2+ ions with the crown ethers 15-crown-5, benzo-15-crown-5, 18-crown-6, benzo-18-crown-6 and the cryptands (211), (221) and (222) in N,N-dimethylform-amide solution has been carried out at 25°C. The stability constants of the resulting complexes were determined by means of conductometric, calorimetric and potentiometric titrations. The calorimetric titration was also used to determine the reaction enthalpy. It is found that the silver ion forms with cryptands the most stable complexes. Among the investigated alkali and alkaline earth cryptates the [Li+C211], [Ca2+C211], [Na+C221], [Srf+C221], [K+C222], and [Ba2+C222] cryptates show the highest stability constants. K+ and Ba2+ form with the examined crown ethers the most stable complexes among the alkali and alkaline earth complexes; 15-crown-5 and benzo-15-crown-5 form 2:1 complexes with some of the cations.

We have investigated the ways by which magnesium (II), calcium (II) and barium (II) and their ATP complexes bind to B-DNA. Effects on native calf thymus DNA conformation were studied and compared with those involving the uncomplexed metal ions and the polymer. It was found that MgATP−2, CaATP−2 and BaATP−2, interact with the phosphates of the polynucleotide; only BaATP −2 appears to bind also through the bases. ATP complexes cause transitions mainly to the B family. The C form is induced by small amounts of MgATP −2 or CaATP−2. At high complex concentrations (r = 2.5 or 5) the polynucleotide adopts the ψ conformation, while BaATP−2 induces this transition at r = 0.6. A contribution of the A form is observed in the case of CaATP-DNA at r = 0.6 and at the beginning of the reaction in the Ba-DNA system at 22°C, for r = 5. The alkaline earth metal ions induce a stabilization of the B conformation. Structural changes with magnesium (II) at r = 2.5 are interpreted in terms of a B to C transition. Calci...

The complexation of alkali and alkaline earth cations in aqueous solution by crown ethers, diaza crown ethers and cryptands has been studied using pH-metric, calorimetric and competitive calorimetric titrations. Use of different experimental techniques makes it possible for the first time to obtain a large number of stability constants and thermodynamic parameters for complexation between these cations and ligands.

Complexation of Ca2+, Sr2+ and Ba2+ with cryptands C222, C221, C211 and C22 have been studied in dimethylsulfoxide solution by means of a competitive spectrophotometric technique using murexide as a metal ion indicator. Stabilities of the resulting 1:1 complexes were investigated at different temperatures and enthalpies and entropies of complexation were determined from the temperature dependence of the formation constants. In most cases, a pronounced “cryptate effect” was observed for bicyclic cryptates over corresponding monocyclic complexes; this was characterized by high selectivity and stability. The increased stability is caused by favourable entropic contributions.

The complexation of Li+, Na+, Mg2+ and Ca2+ with 1,10-phenanthroline, 2,2′-bipyridine, 1,2-phenylenediamine, 2-aminopyridine, 8-hydroxyquinoline, catechol and ethylene glycol was studied in 95% ethanol by means of a competitive spectrophotometric method using murexide as indicator. Formation constants of 1:1 conplexes were determined. In the case of all ligands used, the stability of the complexes was found to vary in the order Mg2+ > Ca2+ > Li+ > Na+. It was found that the structure influences the formation and stability of resulting complexes. Effects of various parameters on complexation are discussed.

The interaction between alkaline earth cations and 4-(2-pyridylazo)resorcinol in C2H5OH-H2O mixtures has been studied spectrophotometrically. Formation constants for the resulting 1:1 complexes with different amounts of water in ethanol were determined. There is an inverse relationship between the complex formation constant and amount of water in the mixed solvent. In all solvent mixtures used, the stability of the complexes was found to vary in the order Mg2 + > Ca2+ > Sr2+ > Ba2 +. A linear relationship is observed between log Kt for complexes and the mole fraction of ethanol.

Ca(Pic)2 (Pic = 2,4,6-trinitrophenolate) and 2,2′-bipyridyl (BIPY) react fast to produce Ca(Pic)2(BIPY)2 irrespective of whether the reaction medium is protic (alcoholic) or aprotic (acetone). Crys...

The coordination in aqueous solution of 4-chloro-1,2-phenylenediamine-N',N',N',N'-tetraacetic acid (4-Cl-o-PDTA) with Be(II) and with the transition metal cations cobalt(II), nickel(II) and copper(II) was reported in earlier publications.1,2 In this note a study is presented of the coordination in aqueous solution (25°C, 1 = 0.1 M in KC1) of 4-CI-o-PDTA acid with magnesium(II), calcium(II), strontium(II), barium(II), zinc(II) and cadmium(II).

Potentiometric studies show that in solutions containing a 1:1:1 molar ratio of adenosine-5 ' -triphosphate, 1,10-phenanthroline and a bivalent metal ion, stable ternary complexes are formed with transition metal ions (metal=Cu(II), Zn(II) and Mn(II)) but not with alkaline earth metal ions (metal=Ca(II) and Mg(II)). Potentiometric studies further show that the 1:1 adenosine-5 ' -triphosphate-metal chelates have very little or no tendency to further interact with another adenosine-5 ' -triphosphate molecule or a sulphosalicylic acid molecule. Stability constants for the various binary and ternary metal complexes are reported at 35.0° and μ=0.1 (KNO3).

The N1s and S2p core binding energies have been obtained from X-ray photoelectron spectra (XPS) of a series of alkaline earth metal compounds of the ligand 1,1-Dicyanoethylene-2,2-dithiolate (i-mnt). The binding energies are effected by various metal cations indicating a polarization effect within the series Ba–Mg. A linear relationship between v CN and the N1s binding energies was observed. The 01s core binding energies of crystal water in the investigated species have also been obtained. Different bonded water molecules exhibit different binding energies of the 01s electrons. A linear relationship between the temperature of thermal dehydration and the 01s core binding energies has been proposed.