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A number of compounds of general formula M(PPO)nX2 are described, the metal ion being Zn(II), Cd(II) and Hg(II) and the anions Cl−, Br−, I−, NO3−, ClO4− and NCS−; PPO stands for 2,5-diphenyloxazole and n = 1, 2, 4. The complexes are prepared by reaction of the corresponding metal salts with the molten ligand in the required stoicheiometrical ratio and are characterized by chemical analyses and physical measurements. Their stereochemistry has been assigned on the basis of IR, far IR spectroscopy and molar conductivity values. The ligand PPO is shown to co-ordinate with metal ions via the lone-pair electrons of the nitrogen atom. All the complexes have generally a distorted tetrahedral stereochemistry.

Cyclic voltammetry is proposed for evaluating the ability of cork wastes to remove Mn(II) ions by sorption from waters to be used for public supply. As the first stage, the concentration of several naturally occurring cations (Ca2+, Mg2+, K+ and Na+) were analyzed in the acid washings that were performed to remove them from the cork. The obtained results were then related to the total concentrations of cations released, as measured by flame atomic absorption spectroscopy of solutions made by dissolving ashed samples. Cyclic voltammetry is proposed to measure the manganese concentration in the uptake solutions because it allows the metal oxidation state to be controlled, and was determined to be suitable for use with standard addition methods. Contact time and particle size effects on Mn(II) sorption were evaluated.

One new macrocycle, 4,10-bis(2-hydroxy-5-nitrobenzyl)-4,10-diaza-1,7,-dioxadodecane ( L0 ) has been synthesised and characterised. Its basicity behaviour, as well as that of the two related azamacrocycles 1,7-bis(2-hydroxy-5-nitrobenzyl)-4,10-dimethyl-1,4,7,10-tetraazadodecane ( L1 ) and 1,13-bis(2-hydroxy-5-nitrobenzyl)-4,10-dimethyl-4,7,10,16-tetramethyl-1,4,7,10,13,16-hexaazaoctadecane ( L2 ), was studied by potentiometry in 0.1 M N(CH 3 ) 4 Cl at 25 °C, characterising moreover the ionisation processes related to macrocyclic nitrogens and to nitrophenolic moieties on the base of spectral variations. The equilibria of the three ligands with iron(II) were studied. 1:1 complexation models with different protonation degrees were found for the three ligands and the related formation constants were estimated from potentiometric results. The pH distribution curves are discussed on the basis of spectrophotometric findings.

The coordination of Pd(II) with a set of different mercapto and dimercapto compounds has been investigated by potentiometric titration at 25°C in KCl 0.1 M. The ligand concentration ranged from 10−4 M to 10−3 M, and for each ligand concentration the 0.25, 0.50, 0.75 and 1.00 Metal/Ligand ratios were examined in the 2.5–11 pH range. Using KCl 0.1 M as an ionic strength medium the reported formation constants are implicitly referred to the complexation reaction starting from [PdCl4]2− as is generally done for the aquo ion. On the bases of the estimated complexation stoichiometries some coordination models are proposed. The influence of -SH basicity, total charge of complexes and steric factors on the coordination properties of the various ligands is discussed.

The use of biomasses that result from the agriculture and food industries in removing heavy metals from wastewaters is attracting increasing interest. We present a joined potentiometric and cross polarization magic angle spinning (CP-MAS) carbon-13 (13C) nuclear magnetic resonance (NMR) study on the interaction of olive stones with copper(II), nickel(II), and cadmium(II). The potentiometric measurements allow both to distinguish two kind of basic sites in the olive stones and to postulate the coordination models for the three studied metals. The NMR spectral analysis allows the attribution of the different signals to the components of the olive stone matrix. A comparison of CP-MAS 13C NMR spectra of the samples after metal treatment suggests a specific complexation between metal ions and hydroxyl groups on guaiacyl and syringyl moieties.

Complexes of general formula MLmCl2 · nH2O, where M=cobalt(II) or nickel(II); L=2-(4′-methyl, 2′-pyridyl)-benzimidazole (mpbi), 2-(4′-methyl, 2′-pyridyl)benzothiazole (mpbt), 2-(4′-methyl, 2′-pyridyl)benzoxazole (mpbo), 2-(4′-methyl, 2′-quinolyl)benzoxazole (mqbo), or 2-(4′-methyl, 8′-quinolyl)benzoxazole (mq′bo); m=1,2; n=0–3, were prepared and characterized by t.g.a., conductance and magnetic measurements, i.r. and diffuse-reflectance electronic spectra.

Palladium(II) oxalato complexes with heterocyclic ligands have been prepared and characterized by spectroscopic and biological studies. The compounds are of the general formula Pd(ox)(L) n where ox = oxalato For n = 1, the ligand is isoxazole, 3,5-dimethylisoxazole, 2-methyl-benzoxazole, 2,5-dimethylbenzoxazole, and ethylenediamine, for n = 2, the ligand is N methylimidazole, N -ethylimidazole, N -propylimidazole, 3-amino, 5-methylisoxazole, and 5-amino 3,4 dimethylisoxazole. The Pd(ox)(L) 2 soluble in water are monomeric square-planar; the Pd(ox)(L) that are little soluble in water are dimeric square-planar with the ligand bridging bidentate except to the chelate ethylenediamine. All the compounds exhibit a certain inhibitorial effect with the exception of the Pd(ox)(en) derivative.

The copper(II), cobalt(II) and nickel(II) chloride and bromide complexes with the ligands 2-(2′-quinolyl)-benzimidazole (qbi), 2-(4′-methyl-2′-quinolyl)benzimidazole (mqbi), 2-(4′-methyl-8′-quinolyl)benzothiazole (m'q'bt) have been prepared and characterized by analytical methods, magnetic measurements as well as by electronic absorption, e.s.r. and far i.r. spectra. Complexes of various stoichiometries have been isolated, namely MLX2 (all cobalt complexes with exception of the bromide qbi complex; the chloride and bromide nickel m'q'bt and mq'bt complexes), ML2X2 (M=Co,L=qbi and X=Br; M=Ni, L=mqbi, X=Cl or Br, M=Ni, L=qbi, X=Cl) and ML3X2(M=Ni, L=qbi or mqbi, X=Br). The cobalt ion has a distorted tetrahedral N2X2 coordination in all the CoLX2 complexes, whereas Co(qbi)2Br2 is six-coordinate. The following conclusions may be drawn for the nickel complexes: in those with the 1∶1 metal-to-ligand molar ratio the metal ion is four-or five-coordinate; in those with the 1∶2 and 1∶3 ratios the metal ion is hexa-coordinate, being essentially bound to four nitrogen atoms with halogens, oxygens from water or methanol or nitrogen atoms (from the third ligand) occupying the axial positions.

Palladium(II) malonato complexes with heterocyclic ligands have been synthesized and characterized by spectroscopic and biological studies. The compoun

Preparation of new complexes of 2 - fluoro,5 - nitroaniline (2-F,5-NA) and 4 - fluoro,2 - nitroaniline (4-F,2-NA) of the type ML n X 2 · m H 2 O (where M = Cu(II), Ni(II), Co(II); L = 2-F,5-NA; 4-F,2-NA; n = 2,4,6; X = Cl − , Br − , SCN − , ClO 4 − ; m = 0–2) are described and their i.r., electronic spectra, and magnetic moments are reported. The ligands act always as monodentate O-bonded. The compounds are generally high spin, non electrolytes, and present square planar, tetrahedral and hexacoordinate structures.

EPR studies have been carried out on three copper(II) complexes of 3-amino-5-methylisoxazole(3-AMI), namely(l)Cu(3-AMI) 4 Cl 2 ,(2)Cu(3-AMI) 2 (NO 3 ) 2 and(3)Cu(3-AMI) 2 Br 2 , in polycrystalline, solution and frozen solution forms in order to elucidate the stereochemistry, metal-ligand bond nature and solute-solvent interactions. The magnitude of the spectral parameters obtained from polycrystalline samples are found to represent the approximate local copper(II) environment with the ground state dominated by the d x 2 - y 2 orbital. The molecular species obtained in pyridine and N,N ' -dimethyl formamide (DMF) solutions of Cu(3-AMI) 2 (NO 3 ), and Cu(3-AMI) 2 Br 2 are similar to the corresponding species in complexes of isoxazole and its derivatives studied earlier. But, unlike the above two complexes the spectral parameters obtained in the pyridine and DMF solutions of Cu(3-AMI) 4 Cl 2 are characteristic of CuN 4 and CuO 4 , chromophores respectively with strong metal-ligand σ-bonding. The 4s-character in the ground state is estimated in all the complexes to indicate the axial field strength.

EPR studies have been carried out on a series of copper(IIcomplexes with the general formula CuL(NCS) x Y 2- x [L = N,N,N',N″,N ″-pentamethyldiethylenetriamine (Me 5 den); x = 1 or 2; and Y = ClO 4 , NO 3 or Bϕ 4 ], dissolved in different solvents. These studies have revealed that the symmetry around copper(II) in [Cu(Me 5 den)(NCS) 2 ] and [Cu(Me 5 ,den)-NCS]NO 3 is not trigonal-bipyramidal as predicted by IR, conductivity and optical data. The 4 s contribution to the ground state is found to influence the isotropic contact term and bond parameters. The hyperfine line-widths observed for the copper(II) ion in solutions of these complexes dissolved in pyridine at room temperature are explained using the theory of Wilson and Kivelson. The isotropic spin—rotational relaxation contribution to the residual line-width is found to be smaller for all the complexes when they are dissolved in pyridine.

EPR studies have been carried out on the title complex in polycrystalline and solution forms at room and low temperatures. These studies in polycrystalline sample are indicative of oxygen coordination. In N , N '-dimethylformamide and pyridine solutions of this complex, the solvent molecules are found to occupy the coordination positions of copper(II).

The complexes formed by zinc(II), cadmium(II) and mercury(II) halides and perchlorates with N-ethylimidazole and N-propylimidazole have been prepared and characterized by molecular conductance and i.r. spectral data down to 100 cm −1 . On the basis of the assignments of the metal—halogen and the metal—ligand vibrations, the stereochemistry of the compounds was inferred.

The complexes of manganese(II) halide and thiocyanate with 3.5-diphenylisoxazole (3,5-diPhisox), 3-amino-5-methyl-isoxazole(3-AMI) and 5-amino-3,4-dimethylisoxazole (5-ADI) have been prepeared and characterized by spectrocopic and magnetic methods and by conductivity measurements. The 3,5-diPhisox ligand is N-bonded, while the isoxazolamine ligands are bridging N(ring)- and O-bonded. All the compounds are nonelectrolytes, high-spin, with an octahedral stereochemistry.

Complexes of the type M(4-F3-NA)nX2·mH2O (where M = Cu (II), Ni (II), Co (II); 4-F3-NA = 4-fluoro, 3-nitroaniline; (n = 1–4; X = Cl, Br, SCN, ClO4; m= 0–4) have been studied by i.r. and electronic spectroscopy, magnetic and conductivity measurements. The ligand behaves as monodentate O-bonded. All the compounds are high spin and non-conductors except of the perchlorato derivatives, and have different stereochemistries.

Platinum(IV) chloride complexes with heterocyclic ligands have been prepared and characterized by infrared and electronic spectra. The compounds are of general formula Pt(L) n Cl 4 , where L = N -ethylimidazole, N -propylimidazole, isoxazole, 3,5-dimethylisoxazole, benzoxazole, 2-methylbenzoxazole, 2,5-dimethylbenzoxazole, ethylenediamine, n = 2, 4, and also Pt(enEt 2 ) 3 Cl 4 ·2H 2 O, where enEt 2 = N , N -diethylethylenediamine. These complexes are hexacoordinate with cis or trans configuration. The antitumoral activity of some complexes in mice inoculated with leukemia L1210 is reported.

The synthesis and characterization of new complexes of general formula ML n X 2 · m H 2 O, where M = Ca(II), Sr(II), Ba(II); L = N-methylimidazole (N-Meim), 3-amino-5-methylisoxazole (3-AMI), 5-amino-3,4-dimethylisoxazole (5-ADI), 2,5-diphenyloxazole (PPO); n = 1–4, 6; X = Cl − , Br − , I − , SCN − and m = 0–6, have been reported. All the derivatives are studied by chemical analysis, molar conductivity, i.r. spectra and X-ray powder diagrams in order to give information about the donor atoms' competitivity of the ligands and to elucidate the structure of the complexes. The ligands act as monodentate N-ring bonded, the compounds are generally distorted tetrahedral, only the [Ba(5-ADI) 6 ](SCN) 2 , [Ca(N-Meim) 4 Cl 2 ]·4H 2 O and [Ca(3-AMI) 4 Br 2 ]·3H 2 O are octahedral.

Complexes of the type ML 2 X 2 (where M = Pd(II), Pt(II); L = benzoxazole (BO), 2-methylbenzoxazole (MeBO); X = Cl, Br, I, NO 3 , SCN) have been prepared and characterized by spectroscopic methods and conductivity measurements. The two ligands act as monodentate; the benzoxazole behaves as N-bonded, the 2-methylbenzoxazole as O-bonded. The compounds are non electrolytes and generally trans -square planar with exception of cis -square planar Pt(BO) 2 X 2 (X = Cl, Br), Pt(MeBO) 2 Cl 2 and Pd(MeBO) 2 X 2 (X = Cl, Br, NO 3 ). The biological activity of some compounds was also investigated.

Complexes of cobalt(II) and copper(II) with 5-amino-3,4-dimethylisoxazole (5-ADI) have been prepared and studied by means of magnetic susceptibility measurements, near and far i.r. spectra, electronic spectroscopy and, when possible, conductivity measurements. The 5-ADI generally behaves as bridging (Nring-, O- or Nring-, -NH2) ligand. All the complexes have an octahedral sterochemistry, except Co(5-ADI)2X2 (X = Cl, Br), Co2(5-ADI)7I4 which are tetrahedral and Cu(5-ADI)2 (ClO4)2 · 4 H2O which is square planar.

This paper presents EPR, and optical absorption studies on [Cu(tren)NCS]SCN and [Cu(Me 6 tren)NCS]SCN in solutions. Expressions derived by Barbucci and Bencini are evaluated. It is shown that the molecular motion of the complexes is anisotropic and nondiffusional.

Some 2,5-diphenyloxazole (PPO) and 2,5-dimethylbenzoxazole (Me 2 BO) complexes of palladium (II) and platinum (II) have been prepared and their molar conductivities, i.r. and electronic spectra are reported and discussed. The PPO generally acts as monodentate N-bonded, while the Me 2 BO behaves as monodentate O-bonded. The complexes are generally trans -square planar.

In the present work we have studied the complexes of the ligands 3-amino, 5-methylisoxazole (3-AMI) and 5-amino-3,4-dimethylisoxazole (5-ADI) with the metal salts CrX3·nH2O (where X = Cl, Br, I, NO3; n = 9, 10). The compounds have been characterized on the basis of spectroscopic methods, magnetism and conductivity measurements. We have calculated the ligand field parameters. All the complexes are hexa-coordinate, with exception of Cr(3-AMI)I3 which should have a distorted tetrahedral stereochemistry. The monomeric complexes are Nring bonded while the polymeric compounds are bridging bidentate Nring and Oring bonded.

The Mn(PPO)nX2 complexes (where PPO is 2,5-diphenyloxazole, n = 1, 2 or 3 and X = Cl−, Br−, I− or SCN−) have been prepared from the corresponding metal salt with the ligand in methanolic solution or with the molten ligand in the appropriate reactant ratio and studied by chemical analysis, electronic and i.r. spectroscopy, magnetic and molar conductivity values at 25°. The complexes are generally nonconducting in DMF; they are high spin and hexacoordinated. The Mn(PPO)X2 complexes are high polymers with both ligand and anions bridging. The Mn(PPO)2X2 species are polymeric with PPO monodentate N-bonded and halogens and thiocyanates bridging bonded; the Mn(PPO)3X2 derivatives have monodentate N-bonded ligands whereas the halogens and thiocyanates are terminal and bridging, respectively.

Complexes of the type M(4-ADI)nX2 · mH2O (where 4-ADI = 4-amino-3,5-dimethylisoxazole; n = 1–4; X = Cl, Br, I, SCN, ClO4; m = 1–4) have been studied by i.r. and electronic spectroscopy, magnetic and conductivity measurements. The ligand behaves as a monodentate -NH2 bonded species in monomeric complexes, but as a bridging ligand-NH2 and -N(ring) bonded species in polymeric complexes. All the compounds have an octahedral stereochemistry, except Co(4-ADI)2X2 (X = Cl, Br, I) complexes, which are tetrahedral.

Cobalt(II) and copper(II) halide, nitrate, thiocyanate and perchlorate complexes of 3-amino-5-methylisoxazole (3-AMI) have been prepared and characterized by means of magnetic, spectroscopic and molar conductivity measurements. In Cu(3-AMI)2X2 compounds (X = Cl, Br, N02) the 3-AMI ligand is bridging and bidentate [N (ring), O(bonded)]. In the other derivatives it is monodentate [N(ring) bonded]. All cobalt(II) complexes have an octahedral stereochemistry, if the Co(3-AMI)2X2 derivatives (X = Cl, Br), which are tetrahedral, are excluded. Copper(II) complexes have generally a distorted square pyramidal stereochemistry in the solid state and in solution.

A number of compounds of general formula M(PPO)nX2 are described, the metal ion being Zn(II), Cd(II) and Hg(II) and the anions Cl−, Br−, I−, NO3−, ClO4− and NCS−; PPO stands for 2,5-diphenyloxazole and n = 1, 2, 4. The complexes are prepared by reaction of the corresponding metal salts with the molten ligand in the required stoicheiometrical ratio and are characterized by chemical analyses and physical measurements. Their stereochemistry has been assigned on the basis of IR, far IR spectroscopy and molar conductivity values. The ligand PPO is shown to co-ordinate with metal ions via the lone-pair electrons of the nitrogen atom. All the complexes have generally a distorted tetrahedral stereochemistry.

Complexes of the type M(4-ADI)nX2 · mH2O (where 4-ADI = 4-amino-3,5-dimethylisoxazole; n = 1–4; X = Cl, Br, I, SCN, ClO4; m = 1–4) have been studied by i.r. and electronic spectroscopy, magnetic and conductivity measurements. The ligand behaves as a monodentate -NH2 bonded species in monomeric complexes, but as a bridging ligand-NH2 and -N(ring) bonded species in polymeric complexes. All the compounds have an octahedral stereochemistry, except Co(4-ADI)2X2 (X = Cl, Br, I) complexes, which are tetrahedral.

The coordination of Pt(II) with different mercapto and dimercapto compounds has been studied using both potentiometric titration at 25°C in KCl 0.1 M and UV–Vis spectroscopy. The slow complex formation kinetics has been followed spectrophotometrically for several days on samples with different ligand molar fractions ranging from 0.1 to 1, keeping the ligand and metal concentration below 8×10−4 M. For the potentiometric titration, the ligand concentrations were kept constant at 10−3 M, and the 0.25, 0.5, 0.75 and 1.00 metal/ligand ratios were titrated in the pH range 2.5–11 for each ligand. The solutions were kept in a thermostatted bath at 25°C for 2 days before titration. The stabilization of the absorbance values under these conditions after 2 days, and the back titration with hydrochloric acid 0.1 M, led us to conclude that the proper equilibrium complex formation is reached under these conditions. Using KCl 0.1 M as an ionic strength medium, the reported formation constants are referred to the complexation reaction starting from [PtCl4]2−. Some models are proposed on the basis of the estimated stoichiometries.

The Fe(2-MeBO)6Cl3 complex has been investigated by Mossbauer spectroscopy. The 85K spectrum shows that a magnetic order is present, a fact ascribed to a superexchange effect mediated by π-electrons of the ligand rings.

Even though many workers have studied solute–solvent interactions of paramagnetic complexes in solutions through the spin-Hamiltonian constants, the attempts made to find a single parameter to study the above are less. From a study on a number of Cu(II) complexes, the authors found that the amount of 4s-character present in the ground state of Cu(II) indicated the nature of the symmetry of the chromophore around Cu(II). In the present investigation six Cu(II) complexes viz. , ( i )[Cu(trien)](ClO 4 ) 2 ,( ii )[Cu(trien)NCS] ClO 4 , ( iii ) [Cu(trien)Br] Br, ( iv ) [Cu(trien)NCS] BPh 4 ,( v ) [Cu(Me 6 trien)NCS] ClO 4 , ( vi )[Cu(Me 6 trien)NCS] SCN (trien = triethylenetetramine;Me 6 trien = hexamethyltrien) in DMF(N,N′-dimethylformamide)solutions are chosen to find the validity of the above procedure. From the calculations, it is found that the ground-state of Cu(II) in the ( iv ) complex is free from 4s contribution indicating planar structure. Whereas in the case of the ( iii ) complex, the ground-state is found to possess 0.95% of 4s character indicating strong axial bond. This 4s character in other cases is found to be less than in the above complex. From these studies it is found that 1% of 4s in the ground-state has reduced isotropic contact term (K) by about 30 MHz. Using this value, the values of K in other complexes are computed and these are found to surprisingly coincide with the values obtained experimentally within 1% error.

In recent work [1] we studied the inhibitory activity of some ML 2 X 2 complexes (M = Pd(II), Pt(II), L = isox and its derivatives, X = Cl, Br) on the Ca, Mg dependent ATP-ase. We have now examined the inhibitory effect of the palladium(II) and platinum(II) complexes with benzoxazole (BO) and 2-methylbenzoxazole (MeBO), the palladium compounds with N-ethylimidazole (N-EtIm), N-propylimidazole (N-PropIM) and the palladium(II) oxalato complexes with heterocyclic ligands. The extraction method of the sarcoplasmatic reticulum (SR) containing Ca, Mg dependent ATP-ase and the inhibitory activity of the complexes towards the ferment and the SH groups determinations by amperometric titrations were published previously [2, 3]. Regarding the benzoxazole and 2-methylbenzoxazole complexes [4], the inhibitory activity in aqueous solution with respect to the Ca, Mg dependent ATP-ase of the palladium(II) is greater than that of the palladium(II) complexes. The chloride derivatives show a greater effect with respect to the bromide for the high lability of the former in comparison with the latter ion. The introduction of a methyl group in position two of the BO ring does not seem to modify the inhibitory effect of the Pd(II) compounds. As regards the N-EtIm and N-PropIm palladium(II) complexes [4] the inhibitory effect in salt aqueous solution of the N-PropIm compounds is higher than the N-EtIm complexes. This fact can be explained by the length of the N-PropIm chain which renders the complex soluble in the enzyme lipidic part. The [Pd(N-PropIm) 2 Cl 2 ] has an activity almost double that of [Pd(N-PropIm) 4 ]Cl 2 , because in the latter case it is difficult to substitute the ligands with water molecules and successively with thiolic groups. The [Pd(L) 4 X 4 derivatives have an activity which increase in the sequence I > Br > Cl. These results are compared with the activity of the platinum(II) complexes in aqueous solution [5]. Because the oxalato complexes are soluble in water and very important in biological systems, we have studied the monomeric, water-soluble [Pd(ox)(L) 2 ] (where L = imidazole and aminoisoxazole derivatives or L 2 = en) and the dimeric, almost insoluble in water, Pd(ox)(L) (where L = isox, 3,5diMeisox, BO and its methyl derivatives) [6]. The inhibitory activity of the Pd(ox)(L) 2 decreases in order N-PropIm > N-EtIm > N-MeIm because the greater length of the ligand chain renders the respective complex more soluble in the ATP-ase lipidic part. The Pd(ox)(en) has no inhibitory effect for the presence of strong bonds of the chelating en. In the Pd(ox)(L) derivatives this effect is generally higher than in Pd(ox)(L) 2 , because the L bridging ligand is easily substituted with water molecules and with thiol groups of the enzyme.