Complexes Of Divalent Metal Ions Research Articles

املاح الفلزات الانتقالية الأولى للدايازونيوم المشتق من مركب حلقي غير متجانس للنيتروجين تحضيرو تشخيص و الفعالية الحيوية

يتضمن البحث تحضيرمعقدات لايونات الكروم (III) والمنغنيز (II) والحديد (III) والكوبلت (II) والتيكل (II) والنحاس (II) والخارصين (II) مع (3- امينو -2- کلوروبیریدین) ديازونيوم ذات الصيغة [Cl-C5H3N=N]n[MXm], حيث ان n=2 او 3 و 4=m او 6 للايونات ثنائية او ثلاثية التكافؤعلى التوالي . شخصت المعقدات المحضرة بوساطة الامتصاص الذري والتحليل الدقيق للعناصر .C.H.N والتوصيلية الكهربائية وطيف الاشعة تحت الحمراء والاطياف الالكترونية وطيف الرنين النووي المغناطيسي للبروتون وقياسات الحساسية المغناطيسية بالاضافة الى التحاليل الحرارية TGA و DTA اظهرت القياسات ان معقدات العناصر ثنائية التكافؤ تكون بنسبة مولية 1:2 (ليكند: فلز) وتمتلك شكل هندسي رباعي السطوح حول الايون الفلزي في حين تمتلك ايونات الفلزات ثلاثية التكافؤ شكل هندسي ثماني السطوح وبنسبة مولية (1:3) (ليكند: فلز) . ودرست الفعالية الحيوية تجاه نوعين من البكتريا Gram, positive (Staphylococcus aureus) , Gram, negative (Klebsieiaella pneumonia)) حيث اظهرت المعقدات 2 و 3 و 5 و 6 فعالية متوسطة في حين المعقدان 1 و 7 اظهرتا فعالية عالية مقارنة مع المادة القياسية.

New azo derivative and their divalent metal ion complexes: Synthesis, characterization, and evaluation of their antibacterial activity

A new azo derivative 3-((4-H1benzo[d]imidazole-2-yl)-4-hydroxy benzaldehyde was prepared by reaction of benzimidazole derivative with 4-hydroxy benzaldehyde. The all-final compounds were diagnosis and determined the structure of these compounds using a variety of spectroscopic methods, including 1H-NMR, FT-IR, UV-Vis, mass spectrometry magnetic susceptibility and atomic absorption spectroscopy. The results showed that all metal ion complexes have an octahedral shape. Antimicrobial activity of the ligand and its metal ion complex had been tested against some selected microorganism such Streptococcus pyogenes a species of Gram-positive and Pseudomonas aeruginosa is a common bacterium gram-negative, all prepared compounds displayed a strong antibacterial activity. Taken together, the results of the current study indicated that the new Azo derivative and their divalent metal ion complexes could be used as a future strategy for other biomedical applications.

Preparation and Characterization of New (Halogenated Azo-Schiff) Ligands with Some of their Transition Metal Ions Complexes

Two new halogenated azo-Schiff ligands were prepared in two steps. The first step included a condensation between 4-amino acetophenone and 2-fluoro-4-bromo aniline to give the corresponding Schiff base. In the second step, the diazonium salt of this Schiff base reacted with 2-naphthol and 4,5-diphenylimidazole to form two new azo-Schiff base derivatives as ligands; (3-((E)-(4-((E)-1-((4-bromo-2-fluorophenyl) imino)ethyl) phenyl) diazenyl) naphthalen-2-ol (HSBAN) (L1) and ((E)-N-(4-bromo-2-fluorophenyl)-1-(4-((E)-(4,5-diphenyl-1H-imidazol-2-yl)diazenyl) phenyl) ethan-1-imine) (HSBAI) (L2), respectively. These new ligands were characterized by mass spectrometry, FT-IR, 1H NMR, UV-Visible spectroscopy and elemental microanalysis (CHN). Five divalent transition metal ion complexes (Co, Ni, Cu, Cd, and Hg) were prepared and characterized, beyond the determination of the optimal condition (concentration, pH value, and the mole ratio M:L) using UV-visible studies. Additionally, complementary techniques, such as atomic absorption, electrical conductivity and magnetic susceptibility, were performed to deduce their geometries. The comprehensive study suggested an octahedral geometry for all complexes except Cd and Hg complexes of the first ligand.

Complexation Equilibria and Determination of Stability Constants of Some Divalent Metal Ion Complexes of L-Cysteine and Diphenylamine in Aqueous Media

<i>Background. </i>Metal complexes of biologically active ligands had considerable interests. L-cysteinate residue, L-Cys, is a biologically abundant and important versatile binding site of proteins. Diphenylamine, DPA, is an important aromatic amine containing two phenyl groups. Complexation equilibria of the divalent metal ions, Ca²⁺ and Zn²⁺ with the bio- relevant α-amino acid, L-cysteine and the nitrogen-containing diphenylamine ligand were investigated by means of the potentiometric technique at 25.0 ± 0.1°C and constant ionic strength of 0.200 ± 0.001 mol·dm^-3 NaNO₃. <i>Objective.</i> The stability constants and standard free energy changes of the α-amino acid, L-cysteine and diphenylamine complex species were determined at 0.200 ± 0.001 mol·dm^-3ionic strength. <i>Methods.</i> The formation of the different 1:1 and 1:2 binary complexes and 1:1:1 ternary complexes were inferred from the potentiometric titrations. <i>Results.</i> The concentration distribution of L-cysteine species formed in solution was evaluated. The dissociation constants of the α-amino acid and diphenylamine were determined at different ionic strength. The stability constants of these binary and ternary systems were calculated. The values of ∆ log₁₀ K, percent relative stabilization, %R.S. and log₁₀ X for the ternary systems were evaluated and discussed. <i>Concussion.</i> The ternary complex formation occurred in a stepwise manner with L-cysteine acting as the primary ligand. The obtained values of ∆ G⁰ indicated that Complex formation reactions are spontaneous. Also, for all systems studied, the ternary complexes formed are more thermodynamically stable than the binary complexes.

Experimental and computational investigation of divalent, trivalent, and tetravalent metal ion complexes of polyvinyl alcohol as adsorbents for fluoride remediation

Divalent, trivalent and tetravalent metal ion complexed polyvinyl alcohol (PVA) films are synthesised via solvent casting and used for fluoride removal from groundwater. Scanning electron microscopy depicts a variation in the morphology on the incorporation of these metal ions, while energy dispersive spectroscopy confirms the presence of the metal ions in the films. XRD analysis shows a decreased degree of crystallinity while TGA affirms the thermal stability of the metal ion complexed PVA films. The possible metal ion-binding interactions to PVA chains are elucidated by Density Functional Theory calculations. The quantum reactivity descriptors and natural bond orbital analysis assert that the complexation of two PVA chains with Zr4+ [(PVA)2Zr2(OH)4] is highly stable. The fluoride uptake by (PVA)2Zr2(OH)4 is thermodynamically favourable and occurs mainly by ligand to metal charge transfer interactions. Experimental fluoride adsorption studies confirm that PVA-Zr films remove ∼90% fluoride from 5 mg L−1 fluoride solution at pH 3–7. Moreover, the PVA-Zr films lower the fluoride content from 2.84 mg L−1 to 0.9 mg L−1 in the groundwater sample, which is below the permissible limit. Thus, it is proven experimentally and computationally that PVA-Zr films have potential commercial applicability in fluoride remediation.

New divalent metal ion complexes with 1,8-diaminonapthalene-2-thione: Synthesis, Spectroscopic, anti-bacterial and anticancer activity studies

Treatment of two molar equivalents of 1,8-diaminonaphthalene-2-thione with one molar equivalent of the metal's(II) salt (Pd, Pt, Hg, Cd, Zn) afforded both neutral thione complexes and thionate derived complexes. The prepared ligand and its complexes (1-8) were characterized via different spectroscopic technics including: FT-IR, 1H, 13C-NMR, and mass spectroscopy. The spectroscopic data analysis suggested that these compounds adopt different structural geometries. For instance, Pd(II) and Pt(II) complexes show square planar geometry. Whereas, thione complexes of Hg(II), Zn(II), and Cd(II) showed probable tetrahedral structure. However, thionate derived complexes of Hg, and Ph-Hg are expected to be linear. The thionato-Cd(II) complex show bidentate chelating mode through its N and S donor atoms. Furthermore, the newly prepared complexes exhibit nano-structural characteristics, which were measured by SEM and X-Ray diffraction of the powder. SEM data showed that complexes from (3, 5) and (8) gave irregular nano-structure, nano-rod structure, and nano-sphere structural pattern respectively. On the other hand, Complexes (1) and (2) were tested against MCF-7 (breast) and LoVo (colon) cancer cells using MTT assay. It was found that the palladium complex showed a promising antiproliferative activity against colon (LoVo) and breast (MCF-7) cancer cells with IC50 values 21.13 and 22.25 µM respectively. In addition the anti-bacterial activity was study against two different pathogenic bacteria, and the Pd(II) complex displayed highest activity compared with other complexes.

Application of salicylaldehyde based-metal binuclear dithiocarbamate complexes for iron and copper removal from wastewater

This research includes synthesization and characterization of dinuclear transition metal(II) macrocyclic dithiocarbamate complexes (DTC) of the general formula [M(L)]2, where M(II) could be Mn, Fe, Co, Ni, Cu, and Zn, while L is the potassium mono-dithiocarbamate. Then, these complexes were used to remove iron and copper from wastewater. DTC complexes are prepared via a one-pot reaction by mixing secondary amine, CS2, KOH, and metal chloride. All compounds are characterized by FTIR, UV-visible, mass spectra, magnetic moment, conductance, melting point, mass spectroscopy, and 1H-, 13C-NMR spectroscopy. The complexes of divalent metal ions appear to be tetrahedral geometry for Fe(II), Co(II), and Zn(II) complexes, while octahedral geometry is suggested for Mn(II), Ni(II), and Cu(II) complexes. The ligands showed effective Cu and Fe removal efficiency of up to 75.96, 48.9% from wastewater.

Molecular Structure and Electron Affinity of Metal-Solvent Complexes: Insights from Density Functional Theory Simulations

A molecular level understanding of the structure and energetics of the monovalent and divalent metal ion complexes is of great importance for development of next-generation batteries. In this contribution, Density Functional Theory (DFT) simulations at the ωb97xD/6–31 + G(d,p) level of theory are performed to investigate the interaction of metal ions (Li+, Na+, K+, Mg2+, Ca2+, Zn2+) with 26 organic solvent molecules. The reduction energetics (electron affinity and reduction potential) and structural responses of the solvent molecules and the molecular complexes are discussed. The DFT calculations are carried out to investigate the structure, energetics and electron affinities of chelated complexes of water (H2O), tetrahydrofuran (THF) and di-methoxy ethane (DME) solvent molecules. Additionally, ab initio dynamic simulations (AIMD) at 298 K using atom centered density matrix propagation (ADMP) formalism are performed to understand the spontaneous structure formation upon electron attachment of the metal ion-solvent complexes. The ADMP simulations indicate the decomposition of Mg+−(DME)3 complex via cleavage of C–O bond of one of the three DME molecules indicating irreversible decomposition of DME in the presence of the Mg+ radical. We believe that the data collected as part of this investigation serves as a library of fundamental knowledge towards a deeper understanding of the electrode-electrolyte interfacial reactions.

Metal Ion‐Coordinating Properties in Aqueous Solutions of the Antivirally Active Nucleotide Analogue (S)‐9‐[3‐Hydroxy‐2‐(phosphonomethoxy)propyl]adenine (HPMPA) – Quantification of Complex Isomeric Equilibria

Acyclic nucleoside phosphonates are of medical relevance and deserve detailed chemical characterization. We focus here on (S)‐9‐[3‐hydroxy‐2‐(phosphonomethoxy)propyl]adenine (HPMPA) and include for comparison 9‐[2‐(phosphonomethoxy)ethyl]adenine (PMEA), as well as the nucleobase‐free (phosphonomethoxy)ethane (PME) and (R)‐hydroxy‐2‐(phosphonomethoxy)propane (HPMP). The acidity constants of H3(HPMPA)+ were determined and compared with those of the related phosph(on)ate derivatives; they are also needed to understand the properties of the metal ion complexes. Given that in vivo nucleotides and their analogues participate in reactions typically as divalent metal ion (M2+) complexes, the stability constants of the M(H;HPMPA)+ and M(HPMPA) species with M2+ = Mg2+, Ca2+, Sr2+, Ba2+, Mn2+, Co2+, Ni2+, Cu2+, Zn2+, and Cd2+ were measured. Comparisons between the results for HPMPA2– and the previous data for PMEA2–, HPMP2– and PME2– revealed that for most M(HPMPA) complexes the enhanced stability (the enhancement relative to the stability of a simple phosphonate‐M2+ coordination), can solely be explained by the formation of 5‐membered chelates involving the ether oxygen. These chelates occur in equilibrium with simple ′open′ phosphonate‐M2+ species, the phosphonate group being the primary binding site. The only exceptions are the M(HPMPA) complexes of Ni2+, Cu2+, and Zn2+, which show an additional stability enhancement; in these instances not only the indicated 5‐membered chelates are formed, but M2+ coordinates in addition to N3 of the adenine residue forming a 7‐membered chelate ring. This observation regarding N3 is important because it emphasizes the metal ion affinity of this site (which is often ignored). Note that in the DNA double helix N3 is exposed to the solvent in the minor groove. The stability data for the monoprotonated M(H;HPMPA)+ complexes suggest that these carry H+ at the phosphonate group whereas M2+ is partly at the nucleobase and partly also at the phosphonate group. The ratios of these isomers depend on the metal ion involved, e.g., for Cu(H;HPMPA) the ratio of the isomers is about 1:1.

Coordination Chemistry of the Chiral, Facially Coordinating Tridentate Ligand 1,2‐Bis(benzimidazol‐2‐yl)ethanol with 3d Transition Metals

1,2‐Bis(benzimidazol‐2‐yl)ethanol (1) and its bis‐N‐methylated derivative (2) act as chiral tridentate facially coordinating ligands capable of binding metals right across the d‐series. Octahedral complexes of divalent and trivalent metal ions are synthesised and characterised by X‐ray crystallography. Only two of the three possible diastereomers are observed in complexes of the type [M(1,2)2] and appear to be close in energy. In complexes of MII ions, the alcohol function of the ligand stays protonated, but the proton is lost in complexes of MIII ions. Electronic and CD spectra are reported. Slow oxidation of the vanadium(III) complex leads to a mixed valence compound where one ligand has been oxidised.

Studies of Ni(II) and Cu(II) complexes with schiff base derived from salicylaldehyde and aniline

The schiff base ligand and its complexes of divalent metal ions of Ni (II) and Cu (II) were synthesized. The ligand and the complexes were characterized by elemental analysis, potentiometry, molar conductance, melting point or decomposition temperatures and infrared analyses. The elemental analysis data show the formation of 1:2 metal-ligand ratio. The ligand and complexes were screened for antibacterial activity against Escherichia coli and Staphylococcus aureus , and antifungal activity against Aspergillums niger and Candida albican , using discs diffusion method. It has been found that the ligand and the complexes showed different activities against microorganisms. The complexes show higher activity than the free Schiff base ligand. The molar conductance of the complexes measured is low, indicating their non-electrolytic nature. The potentiometric studies of the complex compounds revealed 1:2 metal to ligand ratio. Keywords: salicylaldehyde, aniline, ligand, potentiometry, antibacterial, antifungal

Synthesis and Spectroscopic Studies of new ligand N-((4-(phenylamino)phenyl)carbamothioyl)acetamide with some Divalent Metal Ion Complexes

Synthesis and Spectroscopic Studies of new ligand N-((4-(phenylamino)phenyl)carbamothioyl)acetamide with some Divalent Metal Ion Complexes

Transition metal(II) complexes of histidine-containing tripeptides: Structures, and infrared spectroscopy by IRMPD

Complexes of divalent metal ions (Cu2+ and Ni2+) with histidine tripeptide complexes (HAA, AHA and AAH) are interesting gas-phase models for some of the most widely observed patterns of metal ion binding to peptides and proteins. Gas-phase structures were characterized using infrared multiple photon dissociation (IRMPD) spectroscopy in ion-trapping mass spectrometers, along with density functional theory (DFT) computations. Ground states are square-planar with two deprotonated amide nitrogens bound to the metal ion via a double iminol rearrangement (IM binding mode), but contrary to expectations based on solution behavior, the histidine imidazole group is not bound to the metal, but instead is hydrogen bonded remote from the metal ion. The alternative “charge-solvated” (CS) binding mode (amide carbonyl oxygens binding the metal ion) lies higher in energy, but in many cases was observed to be present as conformationally unrelaxed ions with an abundance (relative to the IM conformation) that was dependent on instrument configuration and source and trap conditions. Taking advantage of the ability to form and trap both IM and CS conformations for a few of the complexes, the infrared spectroscopy of both conformations was explored in the fingerprint (1000–1800 cm−1) and hydrogen-stretching (3200–3800 cm−1) regions. For the fingerprint region, agreement is very good between the observed IRMPD spectra and the spectra predicted by DFT calculations at the B3LYP/6–311 + +g(d,p) level. Agreement in the H-stretching region is not perfect, but the characteristic IM and CS spectral patterns are evident.

Complexation of the Zn, Co, Cd, and Pb ions by metallothioneins: A QM/MM simulation

Complexation of divalent metal ions (Zn, Co, Cd and Pb) with metallothioneins (MT), typical low-molecular proteins of diverse higher organisms, has been theoretically studied within the all-electron approximation B3LYP/DZP. The active site of MT (metal ions and cysteine residues) adopts the structure, in which cadmium, cobalt and zinc ions reveal a tetrahedral location of the sulfur atoms. A pyramidal structure is typical for the coordination environment of the lead complexes in the MT active site. The Gibbs energies of the active site formation were calculated accounting the influence of water medium in terms of the IEFPCM approximation. For all studied metallothioneins, the metal–active site complexes demonstrate close Gibbs formation energies per one metal ion. The influence of the amino acid environment of the MT active sites has been studied with the two-shell ONIOM model and B3LYP/DZP:UFF approximation. A simple scheme for calculation of relative metal–MT binding energies has been developed. Even under the pronounced destabilization of the lead complexes by a polypeptide shell, the total energetic effect is sufficient to make accumulation of lead ions by metallothioneins more efficient than Cd and, especially, Zn and Co. The following general trend of stability of the MT complexes has been found: Co≈Zn≪Cd≪Pb. These results compared with the experimental regularities of bioaccumulation of heavy metal salts by bacteria Bacillus are briefly discussed.

Chemical speciation of some divalent transition metal ion complexes of L-ornithine in low dielectric media

Chemical speciation of some divalent transition metal ion complexes of L-ornithine in low dielectric media

Divalent Metal-Ion Complexes with Dipeptide Ligands Having Phe and His Side-Chain Anchors: Effects of Sequence, Metal Ion, and Anchor.

Conformational preferences have been surveyed for divalent metal cation complexes with the dipeptide ligands AlaPhe, PheAla, GlyHis, and HisGly. Density functional theory results for a full set of complexes are presented, and previous experimental infrared spectra, supplemented by a number of newly recorded spectra obtained with infrared multiple photon dissociation spectroscopy, provide experimental verification of the preferred conformations in most cases. The overall structural features of these complexes are shown, and attention is given to comparisons involving peptide sequence, nature of the metal ion, and nature of the side-chain anchor. A regular progression is observed as a function of binding strength, whereby the weakly binding metal ions (Ba(2+) to Ca(2+)) transition from carboxylate zwitterion (ZW) binding to charge-solvated (CS) binding, while the stronger binding metal ions (Ca(2+) to Mg(2+) to Ni(2+)) transition from CS binding to metal-ion-backbone binding (Iminol) by direct metal-nitrogen bonds to the deprotonated amide nitrogens. Two new sequence-dependent reversals are found between ZW and CS binding modes, such that Ba(2+) and Ca(2+) prefer ZW binding in the GlyHis case but prefer CS binding in the HisGly case. The overall binding strength for a given metal ion is not strongly dependent on the sequence, but the histidine peptides are significantly more strongly bound (by 50-100 kJ mol(-1)) than the phenylalanine peptides.

Solution equilibria studies of complexes of divalent metal ions with 2-aminophenol and 3,4-dihydroxybenzoic acid

The chelation abilities of 2-aminophenol and 3,4-dihydroxybenzoic acid with divalent metal ions (Cu2+, Be2+, Zn2+, Ni2+, Co2+ and Mn2+) in binary and ternary systems at 37±0.1°C and an ionic strength of 0.15moldm−3 NaCl were systematically investigated by using the potentiometric titration method. The chelating abilities of these complexes were obtained by processing the titration data using the Hyperquad2008 program and the results are presented as stability constants. In a binary system, it was shown that metal complexation involving 3,4-dihydroxybenzoic acid (ligand D) is more stable than the one with 2-aminophenol (ligand A). The stability of the formed metal complexes, both in binary and ternary systems, decreases in the following order: Cu2+>Be2+>Zn2+>Ni2+>Co2+>Mn2+. The tendency of these metals and ligands to form binary or ternary complexes was also evaluated and discussed by calculating their ΔlogKM and logX values. In addition, the distribution of complex species in these systems was graphically presented using the HySS2009 program. UV–Vis spectrophotometry was also performed to qualitatively verify the protonation of these ligands and to confirm the model of the complex formed.

Synthesis, antimicrobial activity, structural and spectral characterization and DFT calculations of Co(II), Ni(II), Cu(II) and Pd(II) complexes of 4-amino-5-pyrimidinecarbonitrile

Co(II), Ni(II), Cu(II) and Pd(II) complexes of 4-amino-5-pyrimidinecarbonitrile (APC) have been synthesized and characterized using elemental analysis, magnetic susceptibility, mass spectrometry, infrared (4000–200cm−1), UV–Visible (200–1100nm), 1H NMR and ESR spectroscopy as well as TGA analysis. The molar conductance measurements in DMSO imply non-electrolytic complexes, formulated as [M(APC)2Cl2] where M=Co(II), Ni(II), Cu(II) and Pd(II). The infrared spectra of Co(II), Ni(II) and Cu(II) complexes indicate a bidentate type of bonding for APC through the exocyclic amino and adjacent pyrimidine nitrogen as donors whereas APC coordinated to Pd(II) ion as a monodentated ligand via a pyrimidine nitrogen donor. The magnetic measurements and the electronic absorption spectra support distorted octahedral geometries for Co(II), Ni(II) and Cu(II) complexes however a square planar complex was favored for the Pd(II) complex (C2h skeleton symmetry). In addition, we carried out B3LYP and ω-B97XD geometry optimization at 6-31G(d) basis set except for Pd(II) where we implemented LanL2DZ/6-31G(d) combined basis set. The computational results favor all trans geometrical isomers where amino N, pyrimidine N and Cl are trans to each other (structure 1). Finally, APC and its divalent metal ion complexes were screened for their antibacterial activity, and the synthesized complexes were found to be more potent antimicrobial agents than APC against one or more microbial species.

Imperfect coordination chemistry facilitates metal ion release in the Psa permease

The relative stability of divalent first-row transition metal ion complexes, as defined by the Irving-Williams series, poses a fundamental chemical challenge for selectivity in bacterial metal ion acquisition. Here we show that although the substrate-binding protein of Streptococcus pneumoniae, PsaA, is finely attuned to bind its physiological substrate manganese, it can also bind a broad range of other divalent transition metal cations. By combining high-resolution structural data, metal-binding assays and mutational analyses, we show that the inability of open-state PsaA to satisfy the preferred coordination chemistry of manganese enables the protein to undergo the conformational changes required for cargo release to the Psa permease. This is specific for manganese ions, whereas zinc ions remain bound to PsaA. Collectively, these findings suggest a new ligand binding and release mechanism for PsaA and related substrate-binding proteins that facilitate specificity for divalent cations during competition from zinc ions, which are more abundant in biological systems.

Stabilities of the Divalent Metal Ion Complexes of a Short-Chain Polyphosphate Anion and Its Imino Derivative

The stability constants of ML-type complexes of the two linear triphosphate ligand anion analogues triphosphate ( {text{P}}_{ 3} {text{O}}_{10}^{5 - } ) and diimidotriphosphate ( {text{P}}_{ 3} {text{O}}_{ 8} ( {text{NH}})_{2}^{5 - } ) were investigated thermodynamically using potentiometric titrations according to Schwarzenbach’s procedure. The stability constants of the ML-type complexes of different divalent metal ions with {text{P}}_{ 3} {text{O}}_{ 8} ( {text{NH}})_{2}^{5 - } are larger than those of the corresponding complexes with {text{P}}_{ 3} {text{O}}_{10}^{5 - } because of the greater basicity of the imino group. The order of the stability constants for the ML-type complexes follows the Irving–Williams order, indicating that only non-bridging oxygen atoms are coordinated directly to the different metal ions in both ligands, and that the imino groups cannot participate in coordination to the metal ions. In the complexation reactions of the Ca2+, Sr2+, Ba2+– {text{P}}_{ 3} {text{O}}_{10}^{5 - } and Cu2+, Zn2+, Ni2+– {text{P}}_{ 3} {text{O}}_{ 8} ( {text{NH}})_{2}^{5 - } systems, each metal ion forms an enthalpically stable complex, and there was no suggestion of a conspicuous entropic effect based on the chelate effect. Monodentate complexes that are strongly coordinated with the ligands were therefore formed, whereas entropically stable bidentate complexes were formed in the complexation reactions of the Cu2+, Zn2+, Ni2+– {text{P}}_{ 3} {text{O}}_{10}^{5 - } and Ca2+, Ba2+, Sr2+– {text{P}}_{ 3} {text{O}}_{ 8} ( {text{NH}})_{2}^{5 - } systems. According to the HSAB concept, hard metal cations such as Ca2+, Ba2+ and Sr2+ should bind to the harder oxygen atoms rather than the softer nitrogen atoms of the imidopolyphosphate anions, preventing direct coordination to the imino nitrogen atom.Graphical Electronic supplementary materialThe online version of this article (doi:10.1007/s10953-013-0099-2) contains supplementary material, which is available to authorized users.