Synthesis,crystal structure and magnetic properties of 2D bi-layered coordination polymer

A new coordination polymer, [Ni(pydc)(H₂O)₂]?·?H₂O (1) (H₂pydc?=?pyridine-3,4-dicarboxylic acid), have been synthesized by treating Ni(II) nitrate with 3,4-pyridinedicarboxylic acid under hydrothermal conditions. The single-crystal X-ray structure reveals that 1 is a 2D bi-layered coordination polymer. Single-crystals are triclinic, space group P 1 , with a?=?7.065(3), b?=?7.812(4), c?=?9.031(4)?Å, α?=?75.568(8), β?=?68.970(8), γ?=?75.927(8)°, V?=?444.0(3)?ų, Z?=?2. Variable temperature magnetic susceptibility measurements demonstrate a ferromagnetic interaction in 1.     

Crystal structure studies and antimicrobial activities of transition metal complexes of pyridine-2,6-dicarboxylic acid and imidazole containing water clusters

Two new copper(II) and chromium(III) complexes of tridentate 2,6-pyridinedicarboxylic acid (H₂pydc) with imidazole (im), (Him)[Cu(Hpydc)(pydc)]?H₂pydc?5H₂O (1) and (Him)[Cr(pydc)₂]?H₂pydc?5H₂O (2), have been prepared and characterized by elemental analysis, TGA measurements, FT-IR, and UV–Vis spectroscopy, powder and single crystal X-ray crystallography. Crystal structure analyses reveal that both copper(II) and chromium(III) ions are in a distorted octahedral environment. The optimized geometrical parameters were calculated using methods based on the density functional theory (DFT). These calculations agree closely with the X-ray structure. The antimicrobial activities of the ligand and the complexes were evaluated in vitro and compared with drugs in use. The results show that the complexes had stronger antibacterial activity than the corresponding ligand and the effectiveness was confirmed against Bacillus subtilis (gram positive) and Klebsiella pneumoniae (gram negative) for 1, and Escherichia coli and K. pneumoniae (gram negative) for 2 by the well diffusion method.     

Synthesis, Structural Characterization and Luminescence of Lanthanide Coordination Polymers with Pyridine-2,5-dicarboxylic Acid

The complexes of formulas [Ln₂(pydc)₂(Hpydc)₂(H₂O)₄]·2H₂O [Ln=Ce ( 1 ), Pr ( 2 ), H₂pydc=pyridine‐2,5‐di‐carboxylic acid] have been hydrothermally synthesized and characterized by elemental analysis, IR, TG and single‐crystal X‐ray diffraction. The structure analyses for 1 and 2 indicate that one‐dimensional metal helical chains are linked through carboxylate groups, and the helical chains are connected with the bridging pydc^2? anion, forming two‐dimensional layered polymeric structures. The luminescent properties of complexes were also discussed.     

A disparate 3-D silver(I) coordination polymer of pyridine-3,5-dicarboxylate and pyrimidine with strong intermetallic interactions: X-ray crystallography,photoluminescence and antimicrobial activity

A polymeric silver(I) complex, [Ag₄(μ-pydc)₂(μ-pm)₂]_n (1) (pydc = pyridine-3,5-dicarboxylate and pm = pyrimidine), has been synthesized and characterized by elemental analysis, IR spectroscopy, thermal analysis, and single-crystal X-ray diffraction. X-ray crystallographic data of 1 revealed that pydc exhibits two different coordinaton modes that play a key role in the construction of the 3-D crystal network including Ag–carboxylate clusters in which close Ag–Ag distances exist. The magnitudes of close Ag–Ag interactions in second-order energy (E²) have been revealed by natural bond orbital analysis performed with single point energy calculation using the experimental geometry of 1. Furthermore, the luminescent properties of 1 show strong fluorescence with two emission maxima in the visible region. Also, 1 has antifungal activity on Candida albicans (MIC value, 4 μg mL^?1) and good antibacterial activity on micro-organisms (MIC value, 64–256 μg mL^?1).     

Fe(III) and cobalt(II) coordination compounds of 5-bromo-6-methyl-2-morpholinepyrimidinium-4-amine pyridine-2,6-dicarboxylate

New coordination compounds, (bmmpaH)[Fe(pydc)₂] · (EtOH)_0.8(H₂O)_0.2 (1), (8QH)[Fe(pydc)₂] · H₂O (2), (2ampyH)₂[Mn(pydc)₂] · H₂O (3), (2ampyH)[Cr(pydc)₂](2ampy)_0.5 · H₂O (4), [Co(H₂O)₅-μ-(pydc)Co(pydc)] · 2H₂O (5), [Ni(pydcH)₂] · H₂O (6), and [Cu(pydcH)₂] (7), where bmmpa, 8Q, 2ampy, pydcH₂ are 5-bromo-6-methyl-2-morpholinepyrimidine-4-amine, 8-hydroxyquinoline, 2-amino-6-methylpyridine, and pyridine-2,6-dicarboxylic acid, respectively, have been synthesized and structurally characterized by elemental analyses, infrared, UV spectroscopic methods, and X-ray crystallography. Metal ions of 1 and 5 are six-coordinate with distorted octahedral geometries. Compound 1 is an anionic mononuclear complex and 5 is a binuclear compound constructed from cationic and anionic parts. The crystal data of 5 reveal that the cationic part is formed by five terminal waters and one μ-carboxylate oxygen O2 from the anionic portion and the anionic complex is built from two deprotonated (pydc)^2? moieties. In the compounds, pydcH₂ is tridentate by one nitrogen of pyridine ring and two oxygens of carboxylate.     

Synthesis,crystal structures,and magnetic properties of three K[M(bpb)(CN)2]-based trinuclear sandwich-like heterobimetallic M(III)–Ni(II) (M = Fe,Cr, Co) complexes

Three trinuclear sandwich-type cyanide-bridged M^III–Ni^II complexes, {[Ni(cyclm)[Fe(bpb)(CN)₂]₂}·8H₂O (1), {[Ni(cyclm)[Cr(bpb)(CN)₂]₂}·2H₂O (2), and {[Ni(cyclm)[Co(bpb)(CN)₂]₂}·CH₃OH·2H₂O (3) (cyclm?=?1,4,8,11-tetraazacyclotetradecane), have been synthesized using K[M(bpb)(CN)₂] (M?=?Fe, Cr, Co; bpb?=?1,2-bis(pyridine-2-carboxamido)benzenate) as building block and one Ni(II) compound containing a 14-membered macrocycle ring as assembling segment. All the complexes have been characterized by elemental analysis, IR spectroscopy, and X-ray structure determination. Single X-ray diffraction analysis shows similar sandwich-like structures, in which the two cyanide-containing building blocks are monodentate through one of their two cyanides, coordinated face to face to the central Ni(II). Investigation of the magnetic properties of 1 and 2 reveals ferromagnetic magnetic coupling between the neighboring Fe(III)/Cr(III) and Ni(II) through the bridging cyanide. A best-fit to the magnetic susceptibilities of 1 and 2 based on the trinuclear M₂Ni model leads to magnetic coupling constants J?=?5.47(1)?cm^?1 for 1 and J?=?6.37(2)?cm^?1 for 2.     

Synthesis,crystal structure and characterization of a series of complexes constructed from coordinated Lanthanides(III) and the heteropolyanion [SiMo12O40]4−

The reaction of α-[SiMo₁₂O₄₀]^4? with trivalent cations Ln³⁺ and N-methyl-2-pyrrolidone leads to a series of complexes of formula [Ln(NMP)₄(H₂O) _n ]H[SiMo₁₂O₄₀]?·?2NMP?·?mH₂O [where Ln?=?La (1), Pr (2), Nd (3), Sm (4), Gd (5), n?=?4, Ln?=?Dy (6), Er (7), n?=?3. NMP?=?N-methyl-2-pyrrolidone]. The syntheses, X-ray crystal structures, IR, and ESR spectra and thermal properties of the complexes 1, 2, 4, 6, 7 have been reported previously. Here, we report X-ray crystal structures, IR, UV, ESR spectra and thermal properties of the complexes [Nd(NMP)₄(H₂O)₄]H[SiMo₁₂O₄₀]?·?2NMP?·?1.5H₂O (3), and [Gd(NMP)₄(H₂O)₄]H[SiMo₁₂O₄₀]?·?2NMP?·?H₂O (5). In addition, the electrochemical behaviour of this series of complexes in aqueous solution and aqueous-organic solution has been investigated and systematic comparisons have been made. All these complexes exhibit successive reduction process of the Mo atoms.     

Syntheses,structures, and properties of CdII and CoII complexes with 5-(pyridin-4-yl)isophthalate

A N-donor containing carboxylic ligand, 5-(pyridin-4-yl)isophthalic acid (H₂L), was applied to construct two new coordination polymers [Cd(L)(DMF)] _n (1, DMF?=?N,N-dimethylformamide) and {[Co(L)(H₂O)₂]?·?0.5CH₃OH?·?1.5H₂O} _n (2) under different conditions. The complexes were characterized by IR, elemental, and thermogravimetric analyses, powder and single crystal X-ray diffraction. In 1 each L^2? links four Cd^II to form a 3-D framework, while in 2 each L^2? connects three metals to form a 2-D layer structure, which is further connected together by hydrogen bonds to form a 3-D architecture. The thermal stability of the complexes and the photoluminescence of 1 were investigated.     

A comparison of solution and solid state coordination environments for calcium(II), zirconium(IV), cadmium(II) and mercury(II) complexes with dipicolinic acid and methylimidazole derivatives

Four new supramolecular compounds, (2-mimH)[Ca(pydcH)₃][Ca(pydcH₂)(pydc)(H₂O)₂]·4H₂O (1), (1-mimH)₂[Zr(pydc)₃] (2), (2-mimH)₂[Cd(pydc)₂]·8H₂O (3), and (2-mimH)₂[Hg(pydc)₂]·8H₂O (4) [where pydcH₂ = pyridine-2,6-dicarboxylic acid (dipicolinic acid), 1-mim = 1-methylimidazole, and 2-mim = 2-methylimidazole], have been synthesized and characterized by elemental analyses, spectroscopic techniques (IR, UV–vis, ¹H NMR, and ¹³C NMR), thermal (TG/DTG/DTA) analysis as well as single-crystal X-ray diffraction. All four compounds are proton-transfer salts of the methylimidazolium cations and metal complex anions that crystallized from a solution of pyridine-2,6-dicarboxylic acid, methylimidazole, metal nitrates or chlorides as starting materials. The coordinating dicarboxylic acid is deprotonated at the carboxyl group and methylimidazole is protonated to balance the charge. In the crystal structures of 1–4, hydrogen bonding and π–π stacking play important roles. Water clusters are formed in 1, 3, and 4. The equilibrium constants of dipicolinic acid (pydc) and methylimidazole derivatives (1-mim and 2-mim), pydc-2-mim, pydc-1-mim proton-transfer systems as well as those of their complexes were investigated by a potentiometric pH titration method. The stoichiometries of most of the complex species in solution were very similar to the cited crystalline metal ion complexes.     

A Novel Proton Transfer Self‐Associated Compound from Dipicolinic Acid and Guanidine and Its Cadmium(II) Complex: Synthesis,Characterization, Crystal Structure,and Solution Studies

A novel 1:2 proton transfer self‐associated compound LH₂ , (GH⁺)₂(pydc^2—), was synthesized from the reaction of dipicolinic acid, pydcH₂, (2, 6‐pyridinedicarboxylic acid), and guanidine hydrochloride, (GH⁺)(Cl^—). The characterization was performed using IR, ¹H and ¹³C NMR spectroscopy and single‐crystal X‐ray diffraction. LH₂ · H₂O crystallizes in the space group C2/c of the monoclinic system and contains eight molecules per unit cell. The unit cell dimensions are: a = 26.480(5)Å, b = 8.055(2)Å, c = 14.068(3)Å. The first coordination complex (GH)₂[Cd(pydc)₂] · 2H₂O, was prepared using LH₂ and cadmium(II) iodide, and characterized by ¹H and ¹³C NMR spectroscopy and X‐ray crystallography. The crystal system is triclinic with space group P1¯ with one molecule per unit cell. The unit cell dimensions are: a = 8.5125(7)Å, b = 11.0731(8)Å, c = 13.2404(10)Å. The cadmium(II) atom is six‐coordinated with a distorted octahedral geometry. The two pydc^2— units are almost perpendicular to each other. The protonation constants of the building blocks of the pydc‐guanidine adduct, the equilibrium constants for the reaction of pydc^2— with guanidine and the stoichiometry and stability of the Cd²⁺ complex with LH₂ in aqueous solution were accomplished by potentiometric pH titration. The solution studies strongly support a self‐association between pydc^2— and GH⁺ with a stoichiometry for the Cd^II complex similar to that observed for the isolated crystalline complex. In fact, the [Cd(pydc)₂]^2— complex was found as the most abundant species in solution (> 90 %) at a pH >5.     

A series of lanthanide-organic frameworks constructed by 2-methyl imidazole dicarboxylate and oxalate: synthesis,structures, and properties

Five lanthanide(III) coordination polymers with 2-methyl-1H-imidazole-4,5-dicarboxylic acid (H₃MIDC) and ammonium oxalate, {[(Ln1)₂(HMIDC)₂(C₂O₄)(H₂O)₃]?·?3H₂O} _n (Ln1?=?Nd (1), Sm (2)), {[Eu₂(HMIDC)₂(C₂O₄)(H₂O)₃]?·?0.5EtOH?·?3H₂O} _n (3), {[Ce₂(HMIDC)₂(C₂O₄)(H₂O)₃]?·?EtOH?·?3H₂O} _n (4), and {[Gd₂(HMIDC)₂(C₂O₄)(H₂O)₃]?·?MeOH?·?3H₂O} _n (5), have been prepared and structurally characterized. Single-crystal X-ray diffraction analyses reveal that 1 and 2 are isostructural, as are 3, 4, and 5. Each exhibits a 3-D open framework, which is built by a regular 2-D grid connected by HMIDC^2? and Ln(III). The luminescence and thermal properties of these complexes have been investigated as well.     

Supramolecular networks constructed by cationic copper(II) complexes incorporating hybrid water–anionic polymeric assemblies

Two complexes, [Cu₂(TFSA)(2,2′-bpy)₄]?·?TFSA?·?8H₂O (1) and {[Cu(4,4′-bpy)(H₂O)₂]?·?TFSA?·?6H₂O} _n (2) (H₂TFSA?=?tetrafluorosuccinic acid, 2,2′-bpy?=?2,2′-bipyridine, and 4,4′-bpy?=?4,4′-bipyridine), have been synthesized and structurally characterized by X-ray structural analyses. Complex 1 is a binuclear molecule bridged by TFSA ligands; 2 is a 1-D chain bridged by 4,4′-bpy ligands. The asymmetric units of the two complexes are composed of cationic complexes [Cu₂(TFSA)(2,2′-bpy)₄]²⁺ (1) and [Cu(4,4′-bpy)(H₂O)₂]²⁺ (2), free TFSA anion, and independent crystallization water molecules. A unique 2-D hybrid water–TFSA anionic layer by linkage of {[(H₂O)₈(TFSA)]^2?} _n fragments consisting of 1-D T6(0)A2 water tape and TFSA anionic units by hydrogen bonds in 1 was observed. Unique 2-D hybrid water–TFSA anionic layer generated by the linkage of {[(H₂O)₆(TFSA)]^2?} _n fragments consisting of cyclic water tetramers with appended water molecules and TFSA anionic units, and 1-D metal–water tape [Cu–H₂O?···?(H₂O)₆?···?H₂O^?] _n in 2 were found. 3-D supramolecular networks of the two complexes consist of cationic complexes and water–TFSA anionic assemblies connected by hydrogen bonds.     

Synthesis,crystal structure,and magnetic properties of a new Fe(II) complex with reduced radical ligands

A new Fe(II) complex, [Fe(HIM2Py)₂(N(CN)₂)₂]?·?2H₂O (HIM2py?=?1-hydroxyl-2(2′-pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1?H-imidazole), has been synthesized and characterized. The X-ray analysis reveals that HIM2py ligands are coordinated to iron as an unusual six-membered bidentate chelate with κ²N(py), O(HIM) mode. The variable-temperature magnetic susceptibility suggests that weak antiferromagnetic interactions exist in the complex.     

Syntheses,structural determination,and binding studies of binuclear eight-coordinate (enH2)[GdIII 2(pdta)2(H2O)2] · 8H2O and mononuclear nine-coordinate (enH2)[GdIII(egta)(H2O)]2 · 6H2O

The (enH₂)[Gd^III ₂(pdta)₂(H₂O)₂]?·?8H₂O (1) (en?=?ethylenediamine and H₄pdta?=?propylenediamine-N,?N,?N′,?N′-tetraacetic acid) and (enH₂)[Gd^III(egta)(H₂O)]₂?·?6H₂O (2) (H₄egta?=?ethyleneglycol-bis-(2-aminoethylether)-N,?N,?N′,?N′-tetraacetic acid) complexes were synthesized and characterized by infrared spectrum, thermal analysis, and single-crystal X-ray diffraction. The complex (enH₂)[Gd^III ₂(pdta)₂(H₂O)₂]?·?8H₂O has a binuclear eight-coordinate structure with pseudo square antiprism and crystallizes in the monoclinic crystal system with C2/c space group. Through a carboxylate bridge, an infinite 1-D zigzag polymeric binuclear [Gd^III ₂(pdta)₂(H₂O)₂]^2? complex anion is formed. All infinite zigzag polymeric complex anions link through hydrogen bonds, yielding a layer structure. (enH₂)[Gd^III(egta)(H₂O)]₂?·?6H₂O has a mononuclear nine-coordinate structure with pseudo monocapped square antiprism and crystallizes in the monoclinic crystal system with P2₁/n space group. Each enH₂ ²⁺ cation, through hydrogen bonds, connects two adjacent [Gd^III(egta)(H₂O)]^? complex anions.     

A Novel Proton Transfer Compound Containing 2, 6‐Pyridinedicarboxylic Acid and Creatinine and its Zinc(II) Complex — Synthesis,Characterization, Crystal Structure,and Solution Studies

The 1:1 proton transfer compound LH₂, (creatH)⁺ (pydcH)^?, has been prepared from the reaction of creatinine, creat, and dipicolinic acid, pydcH₂, (2, 6‐ pyridinedicarboxylic acid) and characterized using IR, ¹H and ¹³C NMR spectroscopy. The first coordination complex (creatH)[Zn(pydc)(pydcH)]·4H₂O, was prepared using LH₂ and zinc(II) nitrate, and characterized using IR, ¹H and ¹³C NMR spectroscopy and single crystal X‐ray crystallography. The crystal system is triclinic with space group with two molecules per unit cell. The unit cell dimensions are a = 8.085(2) Å, b = 10.802(4) Å, c = 13.632(4) Å, α = 104.98(2)°, β = 90.31(2)° and γ = 92.55(3)°. The structure has been refined to a final value for the crystallographic R factor of 0.0381 based on 3003 reflections. The zinc atom is six‐coordinated with a distorted octahedral geometry. The (pydc)^2? and (pydcH)^? units are almost perpendicular to each other. Extensive hydrogen bondings between carboxylate groups, (creatH)⁺ and water molecules throughout the zinc(II) complex as well as π–π stacking and ion pairing play important roles in stabilizing the corresponding lattices. The protonation constants of the building blocks of the pydcH₂‐creat adduct, the equilibrium constants for the reaction of (pydc)^2? with creat and the stoichiometry and stability of the Zn^II complex with LH₂ in aqueous solution were accomplished by potentiometric pH titration. The solution studies support a self‐associated (creatH)⁺(pydcH)^? as the most abundant species at pH = 3.4. The stoichiometry of the crystalline complex (i.e. (creatH) [Zn(pydc)(pydcH)])and that of the most abundant species detected in solution were found the same.     

Coordination architectures and luminescent properties of 5-(pyrimidyl)tetrazolate (Hpmtz) with group 2 metal ions

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 polyoxoniobate constructed from Lindqvist-type hexaniobates and copper coordinated cations

A new organic–inorganic hybrid polyoxoniobate [Cu(1,3-dap)₂(H₂O)][(H₆Nb₆O₁₉)₂Cu(1,3-dap)₂]?·?4(1,3-dap)·20H₂O (1) (1,3-dap?=?1,3-diaminopropane) has been synthesized by the diffusion method and structurally characterized by elemental analyses, infrared spectrum, ultraviolet spectroscopy, and single crystal X-ray diffraction. Crystal structure analysis reveals that 1 consists of a dimeric dumbbell anion [(H₆Nb₆O₁₉)₂Cu(1,3-dap)₂]^2?, a copper coordinated cation, four 1,3-dap ligands and 20 crystal water molecules. Neighboring units are combined via hydrogen bonds forming a 3-D supramolecular framework.     

Synthesis,crystal structure and luminescent properties of two complexes containing [Au(CN)2] − building blocks

Two supramolecular complexes, {{Ni(H₂O)(phen)₂[Au(CN)₂]}[Au(CN)₂]?·?1.5H₂O} _n (1) (phen?=?1,10-phenanthroline) and [H₂teta][Au₂(CN)₄]?·?2H₂O (2) (teta?=?5,7,7,12,14,14-hexamethyl-1,4,8,11-tetra-azacyocloteradeca-4,11-diene) have been synthesized and structurally characterized. Complex 1 was a one-dimensional infinite chain constructed by [Au(CN)₂]^? building blocks. In complex 2, there are one cation, one anion, and two water molecules in the asymmetric unit. The two complexes are interconnected through a combination of aurophilic attractions and hydrogen bonds and formed into 3D supramolecular structures. The aqueous solutions of 1 and 2 display interesting luminescence at room temperature.     

Synthesis,crystal structures,and properties of two heterometallic Cu(II)–M(II) (M = Zn,Ni) oxamidato-bridged coordination complexes

Two heterometallic coordination complexes, {[Cu(aeop)Zn(H₂O)₃]₂?·?3H₂O} _n (1) and [Cu(aeop)Ni(H₂O)₄]?·?4H₂O (2) (H₄aeop?=?N-(2-aminoterephthalic acid)-N′-(1,3-propanediamine)oxamidate), have been synthesized and characterized by elemental analyses, IR, UV spectroscopy, thermogravimetric analysis, and X-ray crystal diffraction. Complex 1 features a 1-D chain constructed from neutral tetranuclear units. Complex 2 is a neutral binuclear complex. Through intermolecular hydrogen-bonding interactions, 2 gives a 3-D network structure. The variable temperature magnetic susceptibility measurements (2–300?K) of 2 show a pronounced antiferromagnetic interaction between the copper(II) and nickel(II), and the exchange integral J is equal to ?42.7?cm^?1.     

Chromium(III) and Calcium(II) complexes obtained from dipicolinic acid: Synthesis, characterization, X-Ray crystal structure and solution studies

The Cr(III) and Ca(II) complexes (dmpH)[Cr(pydc)₂]?H₂O (1) and [Ca₂(pydc)₂(H₂O)₆].2pydcH₂ (2) were synthesized by reaction of 2,9-dimethyl-1,10-phenanthroline (dmp) and pyridine-2,6-dicarboxylic acid (pydcH₂) with Cr(NO₃)₃ and Ca(NO₃)₂, respectively, and characterized using IR spectroscopy, single crystal X-ray diffraction method and solution studies. The space group and crystal system of these two compounds are P2 ₁/c and monoclinic. The crystal dimensions are a = 9.785(3) Å, b = 25.671(4) Å, c = 9.3402(16) Å, β = 90.790(17)° for (1) and a = 9.1319(4) Å, b = 14.8430(8) Å, c = 12.2449(7) Å, β = 98.227(5)° for (2). In complex (1), a water molecule presents in the crystal packing, linking the anionic and cationic fragments together by hydrogen bonding and thus increases the stabilization of crystal lattices. In complex (2), the coordinated water molecules relate each dimer to adjacent dimers forming infinite molecular ribbons by strong hydrogen bondings. Hydrogen bonding and ion pairing play an important role in stabilizing these crystals. The complexation reactions of pydc, dmp and pydc+dmp with Cr³⁺ and Ca²⁺ ions in aqueous solution were investigated by potentiometric pH titrations and the equilibrium constants for all major complexes formed were evaluated.