Potentiometric and spectroscopic studies on yttrium(III) complexes of dihydroxybenzoic acids

The equilibrium reactions of yttrium(III) ion with dihydroxybenzoic acids (2,3-dihydroxybenzoic acid (2,3-DHBA) and 3,4-dihydroxybenzoic acid (3,4-DHBA)) (H(3)L) were investigated in aqueous solution by means of potentiometric and spectroscopic methods, in 0.1 mol.l(-1) ionic strength medium at 25 degrees C. The stability constants are reported for YL, YL(HL)(2-) and YL(2)(3-)- type mononuclear complexes. 2,3-DHBA can bind Y(III) ion strongly and the salicylate mode is effective over the acidic pH range. But in higher pH range, 2,3-DHBA and 3,4-DHBA act more efficiently through catecholate groups. The complexes of 2,3-DHBA are more stable than the complexes of 3,4-DHBA.     

Potentiometric investigations of some catechol derivatives of scandium

The equilibrium reactions of scandium(III) with some triprotic catechol derivatives (H₃L) were studied. The selected ligands that are 2,3-dihydroxybenzoic acid (2,3-DHBA), 3,4-dihydroxybenzoic acid (3,4-DHBA), 3.4-dihydroxyhydrocinnamic acid (3,4-DHHCA), and 3,4-dihydroxyphenylacetic acid (3,4-DHPA) were investigated in aqueous solution by means of potentiometry in 0.1 M ionic medium at 25°C. The stability constants are reported for the ScL and ScL(H₂L)^– mononuclear complexes. 2,3-DHBA can bind to Sc³⁺ ion strongly and the salicylate mode (COO^–, O^–) is effective over the acidic pH range. But in higher pH range, 3,4-DHBA, 3,4-DHHCA, and 3,4-DHPA act more efficiently through catecholate groups (O^–, O^–).Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 3, 2005, pp. 229–233.Original Russian Text Copyright © 2005 by Türkel, Özer.This revised version was published online in April 2005 with a corrected cover date.This revised version was published online in April 2005 with a corrected cover date.     

Thermogravimetric and spectroscopic studies on La(III) and Ce(III) complexes with some thio-schiff bases

Solid complexes of five derivatives of thio-Schiff bases with La(III) and Ce(III) ions were prepared and characterized by elemental and thermogravimetric analyses. The suggested general formula of the solid complexes is [ML₂(H₂O)X]·2H₂O, whereM=trivalent lanthanide ion,L=Schiff base andX=Cl^? or ClO ₄ ^? . Information about the water of hydration, the coordinated water molecules, the coordination chemistry and the thermal stability of these complexes was obtained and is discussed. Additionally, a general scheme of thermal decomposition of the lanthanide-Schiff base complexes is proposed.     

Synthesis,spectroscopic and crystal field studies on some azido-chromium(III)-pyridine complexes

The new complexes mer-Cr(py)₃(N₃)₃, NaCr(py)₄(N₃)₄, KCr(py)₄(N₃)₄, and RbCr(py)₃(N₃)₄ (py = pyridine) have been prepared. Infrared (4000-50 cm⁻¹) and diffuse reflectance spectra (region 300-77 K) of powdered samples have been measured and discussed on bases of the known structures of these complexes. Single crystal absorption spectra for the mer-complex were obtained in the temperature range from 300 to 10 K revealing extensive vibronic structure associated with the ²E_g(O_h) and ²T_1g(O_h) electronic origins. Crystal field calculations were used to assign the bands in the vibronic region and to obtain estimates for the crystal field and Racah parameters for this class of substances. The parameters found for the mer-complex at 10 K are 10 Dq = 17906 cm⁻¹, B = 387 cm⁻¹ and C = 3381 cm⁻¹.     

Mixed-ligand complexes of Ru(III) and Rh(III): ESR studies on some Ru(III) complexes

Reactions of 2-mercapto-3-phenyl-4-quinazolinone (LH) with RuCl₃·xH₂O and RhCl₃·xH₂O afforded the compounds [RuL₂Cl(H₂O)]H₂O, [RuL₂Cl·DMFI and RhL(LH)Cl₂·2H₂O. Reactions of LH with RuCl₃·xH₂O in the presence of N-heterocyclic bases led to the formation of complexes of type [RuL₂ClB]·H₂O (B = pyridine, 3-picoline or imidazole) and [RuLCl₂(o-phen)] H₂O (o-phen = 1, 10-phenanthroline). These complexes were characterized on the basis of analytical, conductivity, magnetic, IR and electronic spectral and ESR studies. Tentative structures for the complexes are proposed.     

Potentiometric studies of indium(III) azide complexes in aqueous medium

The stability constants of indium-azide complexes were determined by the potentiometric method (glass electrode). The effect monitored was the change in pH of a solution of azide and hydrazoic acid (N(-)(3)/HN(3)) when indium(III) cations were added. The azide concentration was varied from close to zero to 90mM, the ionic strength being kept at 2.000 M with sodium perchlorate and the temperature at 25.0 degrees . Evaluation of experimental data showed only mononuclear species, and the global constants found were beta(1) = (2.0 +/- 0.1) x 10(3), beta(2) = (7 +/- 2) x 10(5), beta(3) = (5 +/- 1) x 10(7) and beta(4) = (7 +/- 3) x 10(8).     

Syntheses and spectroscopic studies on tetraaza macrocyclic complexes of praseodymium(III)

Praseodymium(III) macrocyclic complexes of types [Pr(L)(H₂O)₂]Cl₃, [Pr(mac₁)]Cl₃ and [Pr(mac₂)(H₂O)₂]Cl₃ (L = ligands derived by the condensation of diacetyl or benzil with semicarbazide or thiosemicarbazide; mac₁ = macrocyclic ligands derived by the condensation of diacetyl or benzil with carbohydrazide; mac₂ = macrocyclic ligands derived by the condensation of diacetyl or benzil with semicarbazide, thiosemicarbazide or thiocarbohydrazide) have been prepared and characterized by conductance magnetic moment, spectral data, thermal and elemental analyses.     

Synthesis and spectroscopic studies of Sb(III) and Bi(III) complexes of semicarbazones

Summary New complexes of Sb(III) and Bi(III) with semicarbazones of the general formulae SbCl₃ L and BiCl₃ L (whereL=semicarbazones) have been prepared and characterized by IR,¹H- and¹³C-NMR spectral measurements. The results of the spectroscopic studies indicate that the semicarbazone ligands act as bidentate in all the complexes. All complexes are non-electrolytes inDMF solution. The molecular weight determinations indicate that the compounds are monomeric.

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Synthese und spektroskopische Untersuchungen von Sb(III)- und Bi(III)-Komplexen mit Semlcarbazonen

Zusammenfassung Es wurden neue Komplexe von Sb(III) und Bi(III) mit Semicarbazonen von der allgemeinen Formel SbCl₃ L und BiCl₃ L (L=verschiedenene Semicarbazone) dargestellt und mittels IR,¹H- und¹³C-NMR charakterisiert. Die spektroskopischen Untersuchungen zeigten, daß die Semicarbazon-Liganden in allen Komplexen zweizähnig agieren. Molekulargewichtsbestimmungen zeigten die monomere Natur der Verbindungen an.

     

Potentiometric studies on complexes in Cr(III)-l-aspartic acid-dl-methionine or dl-ethionine systems

Simple and mixed-ligand complexes of Cr(III) with l-aspartic acid and dl-methionine or dl-ethionine have been investigated by potentiometric measurements at 25°C and 0.1 M (NaClO₄) ionic strength. The stability constants of the complexes and tendency toward mixed-ligand complex formation have been determined.     

Thiocyanation reaction and spectroscopic studies on some chromium(III) 1,3-diketonates

Complexes of Cr(III) with acetoacetanilide (AAAH), acetoacet-o-toloididide (AATH), 2,4-acetoacexylidide (AAXH), acetoacet-o-chloroanilide (CAAAH), acetoacet-o-anisidide (OAAAH), benzoylacetanilide (BAAH) and benzoyl-m̄-nitroacetanilide (NBAAH) have been prepared and thiocyanated with thiocyanogen in methanol. Rates of reaction and relative yields have been discussed in terms of steric and electronic effects of the substituents in the chelate rings. IR data have been recorded and discussed. All these thiocyanated Cr(III) compounds have been found to be non-electrolytes by conductance measurements in dioxane.     

Synthesis and spectroscopic studies of some halogen-dimethylsulphoxide/tetramethylenesulphoxide-ruthenium(II) and ruthenium(III) complexes with 2-aminobenzimidazole

Synthesis and characterization of seven ruthenium(II) and ruthenium(III) complexes of sulphoxide with 2-aminobenzimidazole are reported. Three different formulations exist; [cis-RuCl₂(SO)₃(2-ABZ)]; [trans-RuCl₂(SO)₃)(2-ABZ)]; and [trans-RuCl₄(SO)(2-ABZ (where SO?=?dimethylsulphoxide(DMSO)/tetramethylenesulphoxide(TMSO); 2-ABZ?=?2-aminobenzimidazole). These complexes are characterized by elemental analysis, conductivity magnetic susceptibility, ¹H-NMR, ¹³C{¹H}-NMR and electronic spectroscopy.     

Chromium(III) and oxovanadium (IV) complexes of some urea derivatives

Summary The preparation of eight new complexes of Cr^III and VO^IV with urea derivatives is reported here. The ligands used were 2-imidazolidinone (ethyleneurea, EU),N,N'-dimethyl-2-imidazolidinone (N,N -dimethylethyleneurea, DMEU), 2-imidazolidinethione (ethylenethiourea, ETU), andN, N, N, N -tetramethyl-2-imidazolidone (tetramethylurea, TMU). The previously reported complex VOCl₂(TMU)₂ was also prepared. All nine complexes were investigated with regard to conductimetry as well as visible and i.r. spectroscopy. All carbonyl-containing complexes exhibit a metal-oxygen bond, whereas in ETU complexes a metal-nitrogen bond seems to be favoured.     

Iron(III) complexes of the tris-(3-aminopropyl) derivative of a 14-membered tetraazamacrocycle: Potentiometric,spectroscopic and electrochemical studies

The properties of the iron(III) complexes of the ditopic macrocyclic ligand with three aminopropyl pendant arms, L¹ = 3,7,11-tris-(3-aminopropyl)-3,7,11,17-tetraazabicyclo[11.3.1]heptadeca-1(17),13,15-triene were investigated in aqueous solution. Potentiometric studies indicated the presence of mononuclear [FeH_hL¹]^h+3 (h = 0–3), and dinuclear [Fe₂L¹]⁶⁺, [Fe₂L¹(OH)]⁵⁺ and [Fe₂L¹(OH)₂]⁴⁺ complexes, and their stability constants were determined at 298.2 K and ionic strength 0.10 mol dm⁻³ in KNO₃. The log K values of mononuclear protonated species indicated the consecutive deprotonation of the aminopropyl arms, suggesting the nitrogen donor atoms from the macrocycle as the preferred coordination environment for the first metal centre, and the amines from the pendant arms for the second one. The dinuclear complex is formed at about 85% of the total amount of the metal ion for 2:1 Fe:L¹ ratio solutions at pH 4.0–4.5. The log K values of the deprotonation of dinuclear hydrolysed species are consistent with the presence of two water molecules directly bound to the metal centres. Spectroscopic UV–Vis and IR data for 2:1 Fe³⁺:L¹ ratio samples confirmed the existence of dinuclear and hydroxo dinuclear species. EPR spectra of these solutions were interpreted by an equilibrium of two high-spin d⁵ state of iron(III) species with different rhombic E/D distortions. Electrochemical studies also established the formation of mono- and dinuclear complexes, showing irreversible redox behaviour. The two metal centres on the dinuclear complexes have only weak interactions.     

Synthetic and spectroscopic studies of some mono-hydrido-bridged complexes of platinum(II)

The mono-hydrido-bridged complexes (PEt₃)₂(Ar)Pt(μ₂-H)Pt(Ar)(PEt₃)₂]-[BPh₄] (Ar = Ph, 4-MeC₆H₄ and 2,4-Me₂C₆H₃) have been obtained by treating trans-[Pt(Ar)(MeOH)(PEt₃)₂][BF₄] with sodium formate and Na[BPH₄]. The cations [PEt₃)₂(Ar)Pt(μ₂-H)Pt(Ar^b')(PEt₃)₂]^b+ (Ar = Ph and Ar^b' - 2,4-Me₂C₆H₃ and 2,4,6-Me₃C₆H₂ have bee identified in solution. Their ^b1H- and ^b31P-NMR data are reported. The X-ray crystal structure of [(PEt₃)₂(Ph)Pt(μ₂-H)Pt(Ph)(PEt₃)₂][BPh₄] is reported.     

Thermal and spectroscopic studies of terbium(III) and dysprosium(III) complexes with piperidin-4-ones

Terbium(III) and dysprosium(III) nitrate complexes with variously substituted 2,6-diphenylpiperidin-4-ones (L¹)-(L¹⁰) of general formula [Ln(L)(NO₃)₂(H₂O)₂]NO₃ have been synthesized. These complexes have been characterized by analytical, spectral and thermal studies. Molar conductance data show that these complexes are 1:1 electrolytes. The presence of two coordinated water molecules is confirmed by thermal and infrared spectral studies. IR spectral data indicate that piperidin-4-ones, in spite of having two coordinating sites, are monodentate, coordinating only through ring nitrogen. The IR and conductance data reveal the presence of two bidentate and one ionic nitrate groups. The nephelauxetic ratio (β), covalency factor (b^1/2) and Sinha’s parameter (δ) evaluated from electronic spectral data of dysprosium(III) complexes indicate a little covalency in metal-ligand bonding.     

Nickel(II) complexes of oligopeptides containing aspartyl and glutamyl residues. Potentiometric and spectroscopic studies

Nickel(II) complexes of di-, tri- and tetra-peptides built up from Asp and/or Glu residues have been studied by potentiometric, UV–Vis and circular dichroism spectroscopic methods. The stoichiometry of the complexes are the same as in the case of common oligopeptides, but the presence of the side chain carboxylate groups results in differences in their stabilities and coordination modes. The presence of the β-carboxylate groups increases the metal binding affinity of the peptides in all cases. This is due to the coordination of the first, second and third aspartic acid residue in the case of the NiL, NiH₋₁L and NiH₋₂L complexes, respectively. The high negative charge of Asp₄ suppresses the metal ion coordination of the third amide function, therefore the NiH₋₃L complex does not form with this tetra-peptide. In the case of peptides containing glutamic acid, no stability enhancement appears because there is only a weak interaction between the nickel(II) ion and the γ-carboxylate group, which is not able to compensate the disfavoured effect of the increasing negative charge of the complexes.     

Potentiometric studies on the complexes of tetracycline (TC) and oxytetracyclin (OTC) with some metal ions

Summary The interaction of Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Zn(II), Cd(II), Hg(II), Pb(II), Al(III), and UO₂(II) ions with tetracycline (TC) were studied by potentiometricpH titrations. The formation constants of the different binary complexes formed in such systems have been determined at 25±0.1°C and =0.1 moll^–1 (NaNO₃). PotentiometricpH equilibrium measurements have been made under the same conditions for the interaction of oxytetracycline (OTC) and Cu(II), Cd(II), Pb(II), and UO₂(II). The formation of (1:1) binary complexes are inferred from the potentiometricpH tritration curves. The protonation constants ofTC andOTC were also determined under the same conditions and refined (ESAB2M computer program). The transition metal stability constants are consistent with the Irving-Williams series.

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Potentiometrische Untersuchungen der Komplexe von Tetracyclin (TC) and Oxytetracyclin (OTC) mit einigen Metall-Ionen

Zusammenfassung Die Wechselwirkungen von Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Zn(II), Cd(II), Hg(II), Pb(II), Al(III) und UO₂(II) Ionen mit Tetracyclin (TC) wurden mittels potentiometrischerpH-Titrationen untersucht. Die Komplexbildungskonstanten wurden bei 25±0.1°C und =0.1 mol/1(NaNO₃) bestimmt. Unter den gleichen Bedingungen wurden die Komplexierung von Cu(II), Cd(II), Pb(II) und UO₂(II) mit Oxytetracyclin (OTC) mittel potentiometrischerpH Gleichgewichtsmessungen untersucht. Aus den potentiometrischenpH-Titrationskurven ergab sich die Bildung von (1:1) binären Komplexen. Die Protonierungskonstanten vonTC undOTC wurden ebenfalls bestimmt und rechnerisch verfeinert (ESAB2M Computer Programm). Die Stabilitätskonstanten für die Übergangsmetalle stimmen mit der Irving-Williams Reihe überein.

     

Complex formation equilibria between aluminum(III), gadolinium(III) and yttrium(III) ions and some fluoroquinolone ligands. Potentiometric and spectroscopic study

Complex formation equilibria of aluminum(III), gadolinium(III), and yttrium(III) ions with the fluoroquinolone antibacterials moxifloxacin, ofloxacin, fleroxacin, lomefloxacin, levofloxacin, and ciprofloxacin were studied in aqueous solution by potentiometric and spectroscopic methods. The identity and stability of metal–fluoroquinolone complexes were determined by analyzing potentiometric titration curves (310 K, μ = 0.15 M NaCl, pH range = 2–11, C_L/C_M = 1?:?1 to 3?:?1, C_M = 1.0 mM) with the aid of Hyperquad2006 program. The main species formed in the system may be formulated as M_pH_qL_r (p = 1, q = ?2 to 2, r = 1–3, L = fluoroquinolone anion, logarithm of overall stability constant, log β_p,q,r = in the range ca. ?10 to 45). The stability of complexes is mostly influenced by metal ion properties (ionization potential, ionic radius) indicating partial ionic character of the coordination bond. The complexes were also characterized by spectroscopic measurements: spectrofluorimetry, ¹H-NMR, and ESI-MS. Fluorimetric data were evaluated with the aid of HypSpec2014 and indicated the formation of ML_r (r = 1–3) complexes with cumulative conditional stability constants significantly lower than the thermodynamic ones. NMR and MS data corroborate potentiometrically determined speciation. Calculated plasma mobilizing capacity of the ligands generally follows the order levofloxacin > moxifloxacin > ciprofloxacin at concentration levels of the ligands higher or equal to ca. 10^?4 M.