Complexes of tri- and tetra-protonated forms of 1,4,8,12-tetraazacyclopentadecane with chloride,nitrate, iodate,and sulfate ions in aqueous media: I. Formation constants,thermodynamic properties,and bonding mechanisms

Complexation stoichiometries and formation constants of tri- and tetra-protonated forms of 1,4,8,12-tetraazacyclopentadecane with NO ₃ ^– , Cl^–, IO ₃ ^– and SO ₄ ^2– ions are determined by pH potentiometric and¹³C NMR spectrometric measurements. Estimates of H and S are obtained from the values of the temperature dependent formation constants and acid dissociation constants. All four anions form only 1 : 1 complexes with the triprotonated amine species. NO ₃ ^– and Cl^– form 1 : 1 complexes only with the tetraprotonated amine, while IO ₃ ^– and SO ₄ ^2– form both 1 : 1 and 2 : 1 complexes. The complexation behavior is interpreted in terms of solvation and internal hydrogen bonding interactions.     

NMR and potentiometric determination of the high pK values and protonation sequence of dipyridino-hexaaza-28-crown-8 and its interactions with selenate,sulfate and nitrate ions in aqueous solution

The aqueous protonation and anion-binding SeO ₂ ^–/4 SO _2– ⁴ , and NO _– ³ ) constants of the macrocyclic polyamine ligand, dipyridino-hexaaza-28-crown-8(L), were measured in 0.1M KCl using a potentiometric titration technique. The protonation sequence of the aza groups of L was studied in D₂O from the chemical shifts of the nonlabile protons so as to find the charge distribution geometry as a function of pD. The study indicates that in 0.1M KC1 fully protonated L forms stable l: 1 complexes with SeO _2– ⁴ (logK=3.68) and SO _2– ⁴ (logK=3.55), but not with NO _– ³ (logK < l.5). All of the amine pK values were above 6.3, thus allowing the use of the protonated form of this ligand over a wide pH range.     

Solvent extraction of uranium(VI) with DI-2-ethylhexyldithiophosphoric acid from aqueous nitrate,chloride, sulfate and phosphate media

The extraction of uranium(VI) with di-2-ethylhexyldithiophosphoric acid (HEhdtp) in benzene from aqueous solutions containing nitrate, chloride, sulfate and phosphate anions was investigated. The data obtained show hat the mechanism of extraction is similar to that established for perchlorate media. The inorganic anions present in the aqueous phase do not participate in the extraction process but affect the magnitude of the distribution ratio by the complexation phenomena which occur in the aqueous phase. In benzene the extracted species is a 12 complex of uranium(VI) with HEhdtp.     

Characterization of aluminum species with nitrate, perchlorate and sulfate ions in the positive and negative ion mode by electrospray ionization mass spectrometry

The application of electrospray ionization mass spectrometry (ESI-MS) for aluminum speciation in the positive and negative ion modes was discussed. Aluminum nitrate, perchlorate and sulfate solutions were measured by ESI-MS. In the positive ion mode, aluminum species containing anions (Al-L; L=NO3, ClO4 and SO4) were identified, while [Al(OH)2(H2O)n]+ (n=2-4) were the main species. The affinity of the anions with Al3+ estimated by ESI-MS was consistent with the hardness of the anions (hard and soft acids and bases principle) and the results from 27Al nuclear magnetic resonance studies. This indicates that the results observed from the positive ion mode preserved the chemical state of aluminum in the solution. In the negative ion mode, [Al(OH)4-nLn]- (n=0-2, L=NO3, ClO4) were the main species, which were considered to be converted from positive aluminum species, [Al(OH)(H2O)n]+ (n=2-4), by the successive addition of anions. Anions did not only attach to one aluminum ion but also bridged two aluminum ions. In Al2(SO4)3 solution, the behavior of SO4(2-) in the negative ion mode differed from that of NO3- and ClO4-. This may reflect the affinity of SO4(2-) with Al3+ in the solution or in the mass spectrometer or in both. Finally, detection mechanisms for the aluminum species in the solution are proposed for both the positive and negative ion modes. It is shown that ESI-MS can be used to observe the interaction between Al3+ and anions. We show the importance of the interpretation of the results by ESI-MS for obtaining new information of the metal species in the solution.     

A competitive polarographic study of complexation of ammonium,anilinium, hydrazinium and pyridinium ions with some macrocyclic ligands in binary ethanol-water mixtures using a Pb(II)/Pb(Hg) couple as an electrochemical probe

The formation of ammonium, anilinium, hydrazinium and pyridinium ion complexes with the crown ethers 18-crown-6 (18C6) and 1,10-diaza-18-crown-6 (C22) and the cryptand C222 in different binary ethanol-water mixtures has been studied by a competitive polarographic method using a Pb²⁺/Pb(Hg) couple as a sensitive electro-chemical probe. Lead ion was found to form very stable complexes with the ligands used, in all solvent mixtures studied; Pb²⁺–C222 cryptate revealed a pronounced cryptate effect compared to the corresponding complexes with the monocyclic crown ethers used. In all solvent mixtures studied, the stability of the resulting 11 complexes between the protonated amines and macrocyclic ligands used vary in the order C22>C222>18C6. The observed selectivity order of each macrocyclic ligand used for different protonated amines is discussed based on the chemical and structural features of the host-guest partners in solution. In all cases studied there is an inverse linear relationship between the complex formation constants and the mole fraction of water in the mixed solvent.     

Electrospray Mass Spectrometry Study on Polynuclear Pd(II) and Ni (II) Complexes of 3, 6, 9, 16, 19, 22‐Hexaazatricyclo [22. 2.2.211,14] triaconta‐11, 13, 24, 26 (1), 27, 29‐Hexaene

Polynuclear Pd(II) and Ni(II) complexes of macrocyclic polyamine 3,6,9,16,19,22‐hexaazatricyclo[22.2.2.2^11,14]‐triaconta 11,13,24,26(l),27,29‐hexaene (L) in solution were investigated by electrospray ionization mass spectrometry (ESIMS). For methanol solution of complexes M₂LX₄ (M = Pd(II) and Ni(II), X= Cl and I), two main clusters of peaks were observed which can be assigned to [M₂LX₃]⁺ and [M₂LX₂]²⁺. When Pd₂LCl₄ was treated with 2 or 4 mol of AgNO₃, it gave rise formation of Pd₂LCl₂ (NO₃)₂ · H₂O and [Pd₂L(H₂O)_m(NO₃)_n]^(4‐n)+, respectively. ESMS spectra show that the dissociation of the former in the ionization process gave peaks of [Pd₂LCl₂]²⁺ and [(Pd₂LCl₂)NO₃]⁺, while dissociation of the later gave the peaks of [Pd₂L(CH₃CO₂)₂]²⁺ and [Pd₂L(CH₃CO₂)₂](NO₃) ⁺ in the presence of acetic acid. Similar species were observed for Pd₂LI₄ when treated with 4 mol of AgNO₃. When [Pd₂L · (H₂O)_m(NO₃)_n]^(4‐n)+ reacted with 2 mol of oxalate anions at 40°C, [Pd₄L₂(C₂O₄)₂(NO₃)₂]²⁺ and [Pd₄L₂(C₂O₄)₂ (NO₃)]³⁺ were detected. This implies the formation of square‐planar molecular box Pd₄L₂(C₂O₄)₂(NO₃)₄ in which C₂O₄^? may act as bridging ligands as confirmed by crystal structure analysis. The dissociation form and the stability of complex cations in gaseous state are also discussed. This work provides an excellent example of the usefulness of ESIMS in the identification of metal complexes in solution.     

Complexation of CH3Hg+ with chloride,sulfate and carbonate in NaClO4: construction of thermodynamic models

The complexation of CH₃Hg⁺ with major ions present in sea and estuary waters (Cl^?, SO₄^2? and CO₃^2?) was studied potentiometrically in an NaClO₄ medium in the ionic strength range 0.1–3.0 mol dm^?3 at 25 °C. The potentiometric data, treated with non‐linear least squares computer programs, led us to establish the formation of the species CH₃HgCl in equilibrium with chloride, CH₃Hg(SO₄)^? species with sulfate and no complex with carbonate. The stoichiometric stability constants obtained at the different ionic strengths were correlated by means of the modified Bromley methodology (MBM) to determine the corresponding thermodynamic constants and interaction parameters. This study is the second of a series designed to simulate, using the MBM thermodynamic model, the behaviour of methylmercury in different conditions of sea and estuary waters. In the first study of the series, the hydrolysis equilibria of methylmercury in NaClO₄ ionic media were established. Copyright © 2002 John Wiley & Sons, Ltd.     

Kinetics of the oxidation of hydrogen peroxide by aquosilver(II) ions in aqueous perchlorate media and comparison with oxidation by CoaqIII,MnaqIII, CeaqIV and FeaqIII

Detailed measurements on the kinetics and stiochiometry of the oxidation of hydrogen peroxide by aquosilver(II) ions are reported. Two Ag_aq^II ions are consumed for each H₂O₂ which disappears, and for [H₂O₂]>[Ag^II] the reaction is first order in Ag_aq^II and zero order in H₂O₂ with the rate independent of acidity in the range 2·0–4·8 M HClO₄. The activation energy for the decomposition of the Ag^IIH₂O₂ complex ∼zero, similar to the oxidations of H₂O₂ by Ce_aq^IV and Mn_aq^III. The contrasting orders in the oxidative reactivity towards H₂O₂ and in the redox potentials of the transition metal cations are discussed. It is suggested that, whereas Ag_aq^II, Ce_aq^IV, Mn_aq^III and Fe_aq^III oxidise H₂O₂ in one-electron transfers involving monomeric cations, the oxidation of H₂O₂ by Co_aq^III may involve a two-electron step with dimeric Co^III.     

Pendant-Arm Macrocycles Derived from the Cyclocondensation Reaction of Sodium 2,6-Diformyl-4-substitutedphenolates and Tris-(2-aminoethyl)amine Derivatives. Preparation, Characterization and Properties of their Dinuclear Copper(II) Complexes

A series of pendant-arm Schiff base macrocycles have been obtained via the cyclocondensation reaction between sodium 2,6-diformyl-4-substitutedphenolates and tris-(2-aminoethyl)- amine derivatives followed by transmetallation with Cu(ClO₄)₂·6H₂O. The resulting dinuclear copper(II) complexes have been characterized by elemental analysis, infrared and mass spectra as well as magnetic moments at room temperature. All complexes have been electrochemically investigated, and two typical compounds have been studied with ESR spectra as well.     

Binuclear and polynuclear transition metal complexes with macrocyclic ligands. 2. New macrocyclic Schiff"s base in the reaction of 4-tert-butyl-2,6-diformylphenol with 1,2-diaminobenzene. Synthesis and structural,spectroscopic, and theoretical study

Condensation of 4-tert-butyl-2,6-diformylphenol with 1,2-diaminobenzene in ethanol is accompanied by partial reduction of the azomethine double bonds to form symmetrical macrocyclic Schiff"s base containing the alternating >C=N and >CH—NH fragments. In solution, this compound exists as the only isomer in which two endocyclic hydrogen atoms are bound to the oxygen atoms of the phenol groups and two other endocyclic H atoms are attached to the nitrogen atoms of the CH₂—NH fragments. All endocyclic protons are involved in hydrogen bonding and undergo rapid exchange with each other at room temperature. In the crystal, the planar macrocyclic molecules are arranged in closely packed stacks. The steric hindrances resulting from overlapping of the bulky tert-butyl groups are eliminated through rotation of the molecules with respect to each other in the adjacent layers. Study of the potential energy surface for the Schiff"s base under consideration by the DFT method demonstrated that the structure corresponding to the global minimum is similar to that found in solution. However, the isolated molecule is nonplanar, its macrocycle adopting a ladder conformation. The local minimum on the potential energy surface whose energy is 2.6 kcal mol^–1 higher than that of the global minimum corresponds to the zwitterionic structure in which all four endocyclic hydrogen atoms are attached to the nitrogen atoms and the macrocycle adopts a tub conformation. Flattening of the ring is considered as a consequence of stacking interactions between the molecules in the crystal.     

Enthalpy of dilution of aqueous systems containing S-trioxane and some amides. Analysis of the interaction of saccharides with amides in aqueous media

Enthalpies of dilution of aqueous systems of trioxane+formamide and trioxane+dimethylformamide have been determined at 25°C. The data have been treated in terms of the Savage-Wood additivity principle, and a first estimate of the pairwise group interaction enthalpy for-O-/CONH is presented. Systems of saccharides and amides are not amenable to the Savage-Wood treatment used in recent works. However, when treated in conjunction with all available data to yield a different set of group interaction parameters, saccharides behave more predictably. Implications of this state of affairs are considered.     

Kinetic study of the reaction of meso-tetrakis (p-trimethylammoniumphenyl)porphinatodiaquorhodate(II) with chloride,bromide, iodide,hexacyanocobaltate(III) and thiocyanate ions in aqueous solution

The reaction of Cl^?, Br^?, I^?, Co(CN)₆^3? and NCS^? with meso-tetrakis (p-trimethylammoniumphenyl)porphinatodiaquorhodate(III), [RhTAPP(H₂O)₂]⁵⁺, has been studied at 15, 25 and 35°C in 0.1 M [H⁺] with μ = 1.00 M (NaNO₃). The value of the acidity constant, K_al, at 25°C is 4.39 × 10^?9 M. The reactions are first order in anion concentration up to 0.9 M. The values of the stability constants, K₁, and the second order rate constants, k₁, for the reaction with Cl^?, Br^?, I^?, Co(CN)₆^3? and NCS^? are respectively 0.23 M^?1 and 2.5 × 10^?3 M^?1 s^?1, 1.1 M^?1 and 6.92 × 10^?3 M^?1 s^?1, 40.0 M^?1 and 17.0 × 10^?3 M^?1 s^?1, 550 M^?1 and 20.0 × 10^?3 M^?1 s^?1, 3400 M^?1 and 20.9 × 10^?3 M^?1 s^?1. The porphine greatly labilizes the Rh(III). There has been about a 500-fold increase in the rate constant for substitution compared to that of [Rh(NH₃)₅H₂O]³⁺. The substitution rates are however about the same as for [Rh(TPPS)(H₂O)₂]^3?, indicating that the overall charge on the complex plays only a minor role. The kinetic results indicate that dissociative activation is occurring in these reactions.     

Gas-phase reactions of the bare Th2+ and U2+ ions with small alkanes, CH4, C2H6, and C3H8: experimental and theoretical study of elementary organoactinide chemistry

The gas-phase reactions of two dipositive actinide ions, Th(2+) and U(2+), with CH(4), C(2)H(6), and C(3)H(8) were studied by both experiment and theory. Fourier transform ion cyclotron resonance mass spectrometry was employed to study the bimolecular ion-molecule reactions; the potential energy profiles (PEPs) for the reactions, both observed and nonobserved, were computed by density functional theory (DFT). The experiments revealed that Th(2+) reacts with all three alkanes, including CH(4) to produce ThCH(2)(2+), whereas U(2+) reacts with C(2)H(6) and C(3)H(8), with different product distributions than for Th(2+). The comparative reactivities of Th(2+) and U(2+) toward CH(4) are well explained by the computed PEPs. The PEPs for the reactions with C(2)H(6) effectively rationalize the observed reaction products, ThC(2)H(2)(2+) and UC(2)H(4)(2+). For C(3)H(8) several reaction products were experimentally observed; these and additional potential reaction pathways were computed. The DFT results for the reactions with C(3)H(8) are consistent with the observed reactions and the different products observed for Th(2+) and U(2+); however, several exothermic products which emerge from energetically favorable PEPs were not experimentally observed. The comparison between experiment and theory reveals that DFT can effectively exclude unfavorable reaction pathways, due to energetic barriers and/or endothermic products, and can predict energetic differences in similar reaction pathways for different ions. However, and not surprisingly, a simple evaluation of the PEP features is insufficient to reliably exclude energetically favorable pathways. The computed PEPs, which all proceed by insertion, were used to evaluate the relationship between the energetics of the bare Th(2+) and U(2+) ions and the energies for C-H and C-C activation. It was found that the computed energetics for insertion are entirely consistent with the empirical model which relates insertion efficiency to the energy needed to promote the An(2+) ion from its ground state to a prepared divalent state with two non-5f valence electrons (6d(2)) suitable for bond formation in C-An(2+)-H and C-An(2+)-C activated intermediates.     

1:1 and 1:2 Complexes of Mercury(II) Halides with 1,3-Thiazolidine-2-thione. Spectral, Thermal, and Crystal Structure Studies

The series of compounds of the general formulae HgX₂(tzdtH) and HgX₂(tzdtH)₂ (X = Cl, Br, I; tzdtH = 1,3-thiazolidine-2-thione) have been prepared, as well as Hg(tzdt)₂. IR, ¹H, and ¹³C NMR spectral data of the complexes indicate thione donation, which is confirmed by the crystal structure analyses of [HgBr₂(tzdtH)]₂, [HgI₂(tzdtH)]₂, and HgI₂(tzdtH)₂. The structures of [HgBr₂(tzdtH)]₂ and [HgI₂(tzdtH)]₂ consist of centrosymmetric doubly bridged dimers, but they are not isostructural. The asymmetry in the HgX₂Hg bridge is more pronounced in the bromo than in the iodo derivative [S–Hg–X(terminal) is 138.19(9)° for X = Br and 123.49(10)° for X = I], which is accompanied by the stronger Hg–S covalent bond in the bromo than in the iodo complex [2.435(4) vs. 2.510(3) Å]. The Hg–X(bridging) (X = Br, I) bond distances are shorter than the sum of van der Waals radii for mercury and X. Dimeric centrosymmetric complex units are held together only by van der Waals forces in [HgI₂(tzdtH)]₂, while in [HgBr₂(tzdtH)]₂ there is an intramolecular hydrogen bond of N–H Br type (3.34(1) Å). HgI₂(tzdtH)₂ exists as a mononuclear tetrahedral complex with two long Hg–S [2.672(1) Å] and two short Hg–I bond distances [2.688(1) Å] related by a twofold axis. The molecules of HgI₂(tzdtH)₂ are linked into infinite chains along the c axis by intermolecular N–H S [3.38(1) Å] hydrogen bonds.     

Mixed-Ligand Metal Succinate Complexes with 1,10-Phenanthroline and Ethylenediamine: Synthesis,Characterization, Spectroscopic and Thermal Studies. Crystal Structure of Succinatocobalt(II) Complex with Phenanthroline

The novel mixed-ligand metal succinate (suc) complexes with 1,10-phenanthroline (phen) and ethylenediamine (en) have been synthesized and characterized by elemental analyses, magnetic moments, UV-VIS and IR spectra. Thermal reactivity of the complexes was studied in air using DTA and TG, and decomposition of the complexes resulted in the formation of corresponding metal oxides. The crystal structure of the [Co(suc)(H₂O)(phen)₂]·1.5H_CO·C₄H₁₀O complex was determined by x-ray diffraction. The Co(II) complex crystallizes as a monobutanol solvate. In the complex, the cobalt ion lies on an inversion center and displays a distorted octahedral coordination with one aqua, one suc and two phen ligands. The suc ligand acts as a monodentate ligand through one of the negatively charged O atoms, while phen behaves as N-donor bidentate ligand. The crystal also contains disordered lattice water molecules and the structure is stabilized by extensive hydrogen bonding to form a three-dimensional infinite network.     

Hyperbranch‐polyethyleniminated functional polymers. I. Synthesis,characterization of novel ABA type of dumbbell‐like polyethyleniminated polyoxypropylenediamines,and their complexing properties with copper(II) ions in aqueous solution

Novel ABA‐type dumbbell‐like water‐soluble copolymers [D230(EI)₄, D400(EI)₄, and D400(EI)₈] were synthesized by introducing ethylenimine (EI) groups into both sides of polyoxypropylenediamines via a simple in situ ethylamination of polyoxypropylenediamine with 2‐chloroethylamine hydrochloride. The structures of the resultant polymers were identified by Fourier transform infrared spectroscopy and ¹H NMR. The percentages of primary, secondary, and tertiary amine present were determined by the potentiometric titration method after treatments with the appropriate chemicals of salicylaldehyde and acetic anhydride. The surface tension and solubilizing behavior of pyrene in the presence of these polymers in aqueous medium were also investigated, and the efficiency to reduce the surface tension and solubilizing behavior of pyrene depends on the attachments of EI to polymer backbone. The chelating properties of these polymers were examined quantitatively by ultraviolet–visible (UV–vis) spectroscopy in the presence of Cu²⁺ ions in aqueous solution, and continuous variation analysis revealed that the most stable complex is formed at the normality ratio of [N]/[Cu²⁺] = 3.0. UV–vis spectroscopy and transmission electron microscopy were used to evaluate the dumbbell‐like water‐soluble copolymer, D400(EI)₈, as a stabilizer for preparing colloidal noble metal nanoparticles (Au and Pt) in aqueous solution. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1360–1370, 2003     

1:1 Metal Complexes of Bivalent Cobalt,Nickel, Copper,Zink, and Cadmium with the Tripodal Ligand tris[2-(dimethylamino)ethyl]amine: Their stabilities and the X-ray crystal structure of its copper(II) complex sulfate

The complex formation by Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, and Cd²⁺ with tris[2-(dimethylamino)ethyl]amine (N(CH₂CH₂NMe₂)₃, Me₆tren) was investigated at 25° and at an ionic strength of 1, using VIS spectroscopy and potentiometric measurements. The stability constants of these complexes are compared with those of tris(2-aminoethyl)amine (N(CH₂CH₂NH₂)₃, tren), obtained under the same conditions. The values of the constants for Me₆tren are much lower than those for tren, due to the bulky Me substituents. The values of the constants can be correlated with the ability of the individual metal ions to adopt coordination number 5. This appears to be easier for Cu²⁺ and Co²⁺ than for Cd²⁺ and Zn²⁺ and is very difficult for Ni²⁺. The 1:1 complexes [ML(H₂O)]²⁺ are monoprotonic acids whose pK_s values are similar or lower than those of the corresponding aquametal ions. The X-ray crystal structure of the copper(II) complex [Cu(SO₄)(Me₆tren)] · 8H₂O reveals pentacoordination at the central ion. The UV/VIS spectra of the aqueous solutions of the Co²⁺, Ni²⁺, and Cu²⁺ 1:1 complexes confirm that the same coordination number is present also in these complexes.     

Complexes of 2, 6‐Bis(hydroxymethyl)pyridine with Different Copper(II) Salts Involving the Anions Chloride,Perchlorate, Nitrate and Acetate. Synthesis and Crystal Structures of the Complexes

Complexes of 2, 6‐bis(hydroxymethyl)pyridine (dhmp) with different Cu^II salts [CuCl₂·6H₂O, Cu(ClO₄)₂·6H₂O, Cu(NO₃)₂·3H₂O, Cu(CH₃COO)₂·H₂O] are prepared ( 1 — 5 , respectively), studied by IR, and their crystal structures reported. Dependent on the anion kind, influences on the distortion of the co‐ordination polyhedron, the distribution of donor sites, the formation of a mono‐ or binuclear complex, and the resultant packing structure of the complex are observed, although in no case the counterions of the used Cu^II salts or water of hydration were found in the co‐ordination sphere. Crystal structures of 1 — 5 indicate hexaco‐ordination of the Cu^II ions with N₂O₄‐environment and show that 1 — 4 are mononuclear 2:1 (L:M) complexes, but 5 is a binuclear 4:2 complex. Crystallization of Cu(ClO₄)₂·6H₂O with dhmp yielded two different complexes ( 2 / 3 ). In 3 , one of the dhmp components is mono‐deprotonated and acts as an anionic ligand. The same behavior is found in 5 . Whereas in the neutral ligand complexes 1 , 2 and 4 the basal planes are occupied by O donors, and N atoms are in the axial positions of the octahedrons, in 3 and 5 the bases are formed by two O and two N donor atoms, and O atoms are in the axes. Moreover, complex 3 shows the N atoms in trans position, but 5 in cis position. The packing of the cationic complex units is typical of strong and weak H bond interactions involving the counterions and hydroxylic or aromatic hydrogen atoms to yield complex network structures.