Ag(I) complexes with the ampicillin,amoxicillin, and cephalexin anions

Constants of formation of Ag(I) complexes with the anions of ampicillin, amoxicillin, and cephalexin at 20°C with a 0.1 M KNO₃ background electrolyte are determined by potentiometric titration. The possible structures of the complexes are discussed.     

Neodymium(III) complexing with ampicillin,amoxicillin, and cephalexin

The interaction of Nd³⁺ ions with ampicillin, amoxicillin, and cephalexin anions (L) in aqueous solution at 20°C and ionic strength of 0.1 (KNO₃) was studied by pH titration. The NdL and Nd(OH)L complexes are formed in weak alkaline solution. The distribution curves of neodymium(III) complex species depending on pH were constructed. The formation constants of the complexes were determined.     

Copper(II) complexation with ampicillin,amoxicillin, and cephalexin

The interaction of Cu²⁺ ions with ampicillin, amoxicillin, and cephalexin (L) anions in an aqueous solution at 20°C with 0.1 M KNO₃ as a background electrolyte was studied by pH-potentiometry. Formation of CuL⁺ and Cu(OH)L complexes was revealed, and their stability constants were determined.     

Preparation,characterization and biological evaluation of copper(II) and zinc(II) complexes with Schiff bases derived from amoxicillin and cephalexin

Copper(II) and zinc(II) complexes of Schiff bases obtained by condensation of amoxicillin and cephalexin with salicylaldehyde/pyridoxal were prepared and characterized by microanalytical, thermogravimetric, magnetic and spectroscopic data. All the complexes were found to be six‐coordinate and containing two water molecules. The electron paramagnetic resonance spectral lines exhibited rhombic distortion from axial symmetry, with g_|| > g_? > g_e, in the copper(II) complexes. The geometry of the zinc(II) complexes appears to be octahedral. All the compounds under investigation showed antibacterial activity. The antibacterial activity showed the following trend: copper(II) complexes > zinc(II) complexes > Schiff base ligands > parent drugs. The copper(II) complexes with the Schiff bases derived from cephalexin showed substantially enhanced activity against Pseudomonas aeruginosa compared with the parent drug. All the copper complexes were also found to be active against kaolin paw oedema, whereas the parent drugs were inactive. Copyright © 2005 John Wiley & Sons, Ltd.     

Reactivity of Al(III) complexes with substituted phthalocyanines

The results of a study of reactivity of Al(III) complexes with acido ligands (Cl^?, OH^?) and substituted phthalocyanine, containing 4 and 8 substituents (Cl, Br, NO₂ or COOH) in different positions of annelated benzene residues, are reviewed. Reactivity of coordinated phthalocyanines is studied by quantum-chemical and spectrophotometric methods for acid-base reactions and reactivity of coordination core is estimated by chemical kinetics methods using reactions of dissociation at the Al-N bonds. The Hammett-Taft correlation equations are derived for mono-and diprotonated tetrasubstituted phthalocyanines of Al(III) with positive ρ values of 10.2 and 59.8, respectively     

Synthesis and physicochemical properties of the Al(III), Ga(III) and In(III) complexes with chrysin

New solid compounds of Al(III), Ga(III) and In(III) with chrysin were obtained. Their composition and some physicochemical properties were studied by thermogravimetric analysis, UV-vis, infrared and solid state ¹³C NMR spectroscopies. Upon heating the hydrated compounds M(C₁₅H₉O₄)₃·nH₂O decomposed to the oxides. The structure of the compounds was elucidated on the basis of obtained results.     

Synthesis, spectral and electrochemical properties of Al(III) and Zn(II) complexes with flavonoids

The synthesis, electrochemical and spectral (UV-vis, 1H NMR, IR, fluorescence) properties as well as thermal behaviors of Al(III) and Zn(II) complexes with the flavonoids quercetin (H2L(1)), rutin (H2L(2)) and galangin (HL(3)) are presented. The complexes may be formulated as [Al2(L(1))(H2O)8]Cl4, [Al3(L(2))2(H2O)12]Cl5, [Al(L(3))(H2O)4]Cl2, [Zn2(L(1))(H2O)4]Cl2, [Zn3(L(2))2(H2O)6]Cl2 and [Zn(L(3))(H2O)2]Cl. The higher fluorescence intensities of the complexes related to the free flavonoids, are attributed to the coordination of the ligands to the small, highly charged Al(III) and Zn(II) ions. The coordination effectively increases the rigidity of the ligand structure and increases the fluorescence quantum yield by reducing the probability of non-radiative energy dissipation process. Antioxidant activities of the compounds were also investigated under an electrochemical point of view. The cyclic voltammetric data show a considerable decrease of the oxidation potentials of the complexes related to that of the free flavonoids. Thus, the flavonoid-metal complexes are more effective antioxidants than the free flavonoids.     

Solid-phase ligand substitution reactions by borohydride anions in chromium(III) and cobalt(III) amine complexes

The kinetic and thermodynamic characteristics of solid-phase ligand substitution reactions were determined for chromium(III) and cobalt(III) amine complexes with B₁₀H ₁₀ ^2– and C₂B₉H ₁₂ ^– in the outer sphere. The kinetic equation of the topochemical process was found to be of the formf()=(1–)^2/3, corresponding to a reaction proceeeding on the interface between the phases (shrinking sphere). Two types of solid-phase ligand substitution reactions were found: endothermic and exothermic reactions taking place either through thermal activation of the metal-ligand bond (in substitution reactions by the anion B₁₀H ₁₀ ^2– ), or through the acid-base proton-exchange reaction between the anion C₂B₉H ₁₂ ^– entering the coordination sphere and the amine leaving it; in this case the process proceeds without mass loss. It could be demonstrated that the reactions occurring in crystalline complex salts cannot proceed by purely dissociative or associative mechanisms; depending on the structure of the crystal lattice, mutually adapted dissociative or associative mechanisms are feasible. Reactions proceeding by the first mechanism haveE _a=300–500 kJ/mol and logA=30–50; the values for reactions proceeding by the second mechanism areE _a= =180–250 kJ/mol and logA=15–25.

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Zusammenfassung Die kinetischen und thermodynamischen Kennwerte der Ligandensubstitutionsreaktionen in fester Phase bei Chrom(III)- und Kobalt(III)-Aminkomplexen mit B₁₀H ₁₀ ^2– und C₂B₉H_12/– als Anionen in der externen Sphäre wurden untersucht. Die kinetische Gleichung des topochemischen Prozesses hat die Formf()=(1–)^2/3, was einer an der Grenzfläche zwischen zwei Phasen verlaufenden Reaktion entspricht. Zwei Typen von Ligandsubstitutionsreaktionen in fester Phase wurden gefunden: endotherme und exotherme Reaktionen verlaufen entweder infolge thermischer Aktivierung der Metall-Ligand-Bindung (in Substitutionsreaktionen des Anions B₁₀H ₁₀ ^2– ) oder durch Protonenaustausch zwischen dem in die Koordinationssphäre eintretende Anion C₂B₉H ₁₂ ^– und dem daraus austretenden Amin; in diesem Falle verläuft der Prozeß ohne Massenverlust. Es konnte gezeigt werden, daß die in kristallinen Komplexsalzen vor sich gehenden Reaktionen nicht nach einem rein dissoziativen oder assoziativen Mechanismus verlaufen können; abhängig von der Struktur des Kristallgitters ist ein wechselseitig angepasster dissoziativer oder assoziativer Mechanismus wahrscheinlich. Die nach dem ersten Mechanismus verlaufenden Reaktionen weisen fürE _a Werte von 300 500 kJ/mol und für logA von 30–50 auf, während bei nach dem zweiten Mechanismus verlaufenden Reaktionen die entsprechenden Werte zwischen 180 und 250 kJ/mol bzw. 15 und 25 liegen.

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() () B₁₀H ₁₀ ^2- C₂B₉ H _12/- . , f()=(1-)^2/3, ( ). : - , - ( B₁₀H ₁₀ ^2- ), - _{29 12} ^- ; ., . . , , _a =300–500 / logA=30–50, –ina=180–250 / log=15–25.

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The authors are grateful to F. G. Szabó (ETALON Factory, Baku) for help in the application of the derivatograph for quantitative measurements and for development of a method to record thermoanalytical curves for measuring enthalpies of reactions.     

Synthesis and crystal structure of Fe(III) and Al(III) complexes with 2-diphenylacetyl-1,3-indandione

Iron(III) and aluminum(III) complexes with 2-diphenylacetyl-1,3-indandione (HL) have been synthesized. The structures of the obtained compounds FeL₃(I) and AlL₃(II) were studied. The isostructural crystals are monoclinic, I: Z = 8, space group P2_1/c, a = 16.061(3) Å, b = 16.658(3) Å, c = 22.015(4) Å, β = 111.41(3)°; II: Z = 8, space group P2_1/c, a = 16.115(14) Å, b = 16.476(8) Å, c = 21.949(20) Å, β = 111.04(11)°. The structural units of crystals I and II are neutral molecules in which each ligand is bidentately coordinated to a central metal atom through the oxygen atom of the acyl keto group and an oxygen atom of the indandione fragment to form a six-membered chelate ring. In the crystals, neutral molecules I and II form pseudodimers due to stacking of indandione moieties of two adjacent coordination spheres and additional C-H…O contacts. Each pseudodimer is in contact with six neighboring dimers also through hydrogen bonds C-H…O to form an infinite framework.     

Crown compounds for anions. Sandwich complexes of cyclic trimeric perfluoro-o-phenylenemercury with hexacyanoferrate(III) and nitroprusside anions

Cyclic trimeric perfluoro-o-phenylenemercury (o-C₆F₄Hg)₃ (1) is able to bind hexacyanoferrate(III) and nitroprusside anions to form complexes {[(o-C₆F₄Hg)₃]₂[Fe(CN)₆]}³⁻ and {[(o-C₆F₄Hg)₃]₂[Fe(CN)₅NO]}²⁻, respectively, which contain one anionic species per two macrocycles. According to X-ray diffraction data, the complexes have unusual sandwich structures wherein the anionic guest is located between the planes of two molecules of 1 and is coordinated to each of these through two types of Fe-C-N-Hg bridges. One type is the simultaneous coordination of a cyanide ligand to all three Hg centres of the cycle. The other type is the coordination of a cyanide group to a single Hg atom of the macrocycle. In both types, the bonding of the anionic guest with the macrocyclic host is accomplished with the participation of π-electrons of the cyanide ligands. The synthesized compounds are the first examples of host-guest complexes of a macrocyclic multidentate Lewis acid with anionic metal complexes.     

Detection of Al(III) and Ga(III) complexes with morin by electrospray ionization mass spectrometry.

The Al(III) and Ga(III) complexes formed by morin (M) in aqueous solution were investigated by means of electrospray ionization mass spectrometry (ESI-MS). In the full scan mass spectra, Al:M showed 1:2 and 2:3 stoichiometric ratios. When (S)-N-acetylserine methyl ester (Ser), as a partial mimic of the serine residue in silk, was added to Al:M and Ga:M complexes in aqueous solution, the mass spectra of Ser:Al:M showed 1:1:1 and 1:1:2 stoichiometric ratios. The patterns of the mass spectra of Ga:M and Ser:Ga:M complexes were similar to those for the corresponding Al(III) complexes. Calculated heats of formation of potential structures of the complexes, with and without bound water, were obtained using semiempirical PM3 calculations.     

Dimeric scandium(III) and monomeric lanthanide(III) complexes with perfluoropropane-1,3-disulfonates as counter anions for Lewis acid catalysis

A novel scandium(III) complex with disulfonates as counter anions, [Sc(μ-OH)(H₂O)₅]₂[O₃S(CF₂)₃SO₃]₂ (5), was prepared from scandium oxides (Sc₂O₃) and perfluoropropane-1,3-disulfonic acid (1, HO₃SCF₂CF₂CF₂SO₃H). By X-ray analysis, 5 was found to be a μ-OH-bridged dimeric structure bearing two perfluoropropane-1,3-disulfonates without bonding to scandium(III) centers. A series of lanthanide(III) complexes were also prepared from 1 and lanthanide oxides (Ln₂O₃; Ln = La, Nd, Sm, and Gd). In sharp contrast to the dimeric scandium(III) complex, the corresponding lanthanide(III) complexes had monomeric structures. Interestingly, the dimeric scandium(III) complex, but not the monomeric lanthanide complexes, with perfluoropropane-1,3-disulfonates served as an efficient Lewis acid catalyst for the hydrolysis of esters.     

Octahedral (cis-cyclam)iron(III) complexes with O,N-coordinated o-iminosemiquinonate(1-) pi radicals and o-imidophenolate(2-) anions

Three octahedral complexes containing a (cis-cyclam)iron(III) moiety and an O,N-coordinated o-iminobenzosemiquinonate pi radical anion have been synthesized and characterized by X-ray crystallography at 100 K: [Fe(cis-cyclam)(L(1-3)(ISQ))](PF(6))(2) (1-3), where (L(1-3)(ISQ)) represents the monoanionic pi radicals derived from one-electron oxidations of the respective dianion of o-imidophenolate(2-), L(1), 2-imido-4,6-di-tert-butylphenolate(2-), L(2), and N-phenyl-2-imido-4,6-di-tert-butylphenolate(2-), L(3). Compounds 1-3 possess an S(t) = 0 ground state, which is attained via strong intramolecular antiferromagnetic exchange coupling between a low-spin central ferric ion (S(Fe) = 1/2) and an o-imino-benzosemiquinonate(1-) pi radical (S(rad) = 1/2). Zero-field M?ssbauer spectra of 1-3 at 80 K confirm the low-spin ferric electron configuration: isomer shift delta = 0.26 mm s(-1) and quadrupole splitting DeltaE(Q) = 1.96 mm s(-1) for 1, 0.28 and 1.93 for 2, and 0.33 and 1.88 for 3. All three complexes undergo a reversible, one-electron reduction of the coordinated o-imino-benzosemiquinonate ligand, yielding an [Fe(III)(cis-cyclam)(L(1-3)(IP))](+) monocation. The monocations of 1 and 2 display very similar rhombic signals in the X-band EPR spectra (g = 2.15, 2.12, and 1.97), indicative of low-spin ferric species. In contast, the monocation of 3 contains a high-spin ferric center (S(Fe) = 5/2) as is deduced from its M?ssbauer and EPR spectra.     

Ruthenium(III) and iridium(III) complexes with nicotine

A new chloride-dimethylsulfoxide-ruthenium(III) complex with nicotine trans-[Ru^IIICl₄(DMSO)[H-(Nicotine)]] (1) and three related iridium(III) complexes; [H-(Nicotine)]trans-[Ir^IIICl₄(DMSO)₂] (2), trans-[Ir^IIICl₄(DMSO)[H-(Nicotine)]] (3) and mer-[Ir^IIICl₃(DMSO)(Nicotine)₂] (4) have been synthesized and characterized by spectroscopic techniques and by single crystal X-ray diffraction (1, 2, and 4). Protonated nicotine at pyrrolidine nitrogen is present in complexes 1 and 3 while two neutral nicotine ligands are observed in 4. In these three inner-sphere complexes coordination occurs through the pyridine nitrogen. Moreover, in the outer-sphere complex 2, an electrostatic interaction is observed between a cationic protonated nicotine at the pyrrolidine nitrogen and the anionic trans-[Ir^IIICl₄(DMSO)₂]^¯ complex.     

Study of the thermal behavior of Al(III) and In(III)-diclofenac complexes in solid state

The Al and In-diclofenac compounds were prepared. Thermogravimetry (TG) and X-ray diffraction powder patterns were used to characterize these compounds. Details concerning the dehydration and thermal decomposition as well as data of kinetic parameters have been described here. The kinetic studies of these stages were evaluated from several heating rates with mass sample of 2 and 5 mg in open crucibles under nitrogen atmosphere. The results of the present study improve the knowledge on these compounds including their dehydration and thermal stability. The obtained data leads to a dependence on the sample mass, which results in two kinetic behavior patterns.     

Disproportionation of hydrogen peroxide in the presence of Mn(III) complexes with various porphyrins and acid anions

The kinetics of homogeneous decomposition of H₂O₂ in the presence of Mn(III) complexes with octaethylporphine or meso-phenyloctaethylporphines and acid anions Cl^?, AcO^?, and SCN^? was studied by volumetry. The ionic-molecular mechanism of the transformation, involving reversible coordination of the H₂O₂ molecule, its irreversible decomposition with the release of H₂O and removal of two electrons from the metal porphyrin, reversible coordination of the second peroxide molecule in the form of HO ₂ ^? , and slow irreversible reduction of the catalyst with the release of O₂ and H₂O was substantiated by electronic absorption spectra. The catalytic activity of Mn(III) porphyrin complexes is independent of the acid anion present as extra ligand, but depends on the structure of the porphyrin ligand, which can be used for controlling the catalytic activity. Unsymmetrical (chloro)(monophenyloctaethylporphinato)managanese(III) is the most active; it increases the rate of O₂ evolution by a factor of 2 at the peroxide: catalyst molar ratio of (3 × 10⁵): 1.     

Synthesis, structural characterization, and properties of aluminum (III) meso-tetraphenylporphyrin complexes axially bonded to phosphinate anions

Aluminum (III) meso-tetraphenylporphyrins axially bonded to phosphinate anions have been synthesized and characterized by NMR and UV-visible spectroscopy, single-crystal X-ray diffraction, and FAB+ mass spectrometry. According to the solvent and the size of the anion, these compounds are able to self-assemble in two different manners.     

Mass spectra of partially fluorinated β-diketonato complexes of Al(III), Cr(III), Fe(III) and Co(III)

The mass spectra of the Al(III), Cr(III), Fe(III) and Co(III) complexes of the anions of hexafluoroacetylacetone (hfac) trifluoroacetylacetone (ttac), benzoyltrifluoroacetone (btac) and thenoyltrifluoroacetone (ttac) have been determined and are discussed here. Emphasis is placed on discerning which of the observed reactions may properly be attributed to the influence of the metal in the complex and those which may be thought of as arising from the nature of the ligand. The most important influence of the coordinated metal is related to its ability to be reduced²; however, the presence of the metal serves to prohibit or facilitate certain rearrangement reactions relative to the free protonated ligand. Since essentially all fragmentation occurs within or by loss of a ligand, the nature of the ligand determines the nature of the observed fragments. Where intramolecular com-petition of fragment types is possible (tfac, btac and ttac complexes), the most probable fragment of a given class, odd electron or even electron, is easily determined. The most commonly eliminated fragments are CF₃and CF₂. Certain metastable peaks are associated with consecutive decomposition in the field free region. Such a phenomenon appears to be common for molecules of the type studied here.