Syntheses and Characterization of Main Group, Transition Metal, Lanthanide, and Actinide Complexes of Bidentate Acylpyrazolone Ligands

The synthesis of acylpyrazolone salts and their complexes of main group elements, transition metals, lanthanides, and actinides are described and characterized inter alia by means of single-crystal X-ray crystallography, NMR, and IR spectroscopies. The complexes consist of two, three, or four acylprazolone ligands bound to the metal atom, resulting in a structurally diverse set of coordination complexes with (distorted) octahedral, pentagonal-bipyramidal, or antiprismatic arrangements. Several complexes proved to be polymeric in the solid state including heterobimetallic sodium/lanthanide coordination polymers. A selection of the polymeric compounds was analyzed via TG/DTA measurements to establish their stability. The ligands, in turn, were readily synthesized in good yields from commercially available hydrazine hydrochloride salts. These findings demonstrate that acylpyrazolone ligands can form complexes with metals of varying ionic radii, highlighted by their utility in other areas such as analytical and metal organic framework chemistry.

On the Capability of Oxidovanadium(IV) Derivatives to Act as All-Around Catalytic Promoters Since the Prebiotic World

For a long time the biological role of vanadium was not known, while now the possibility of using its derivatives as potential therapeutic agents has given rise to investigations on their probable side effects. Vanadium compounds may inhibit different biochemical processes and lead to a variety of toxic effects and serious diseases. But, on the other hand, vanadium is an essential element for life. In recent years, increasing evidence has been acquired on the possible roles of vanadium in the higher forms of life. Despite several biochemical and physiological functions that have been suggested for vanadium and notwithstanding the amount of the knowledge so far accumulated, it still does not have a clearly defined role in the higher forms of life. What functions could vanadium or its very stable oxidovanadium(IV) derivatives have had in the prebiotic world and in the origins of life? In this review, we have briefly tried to highlight the most useful aspects that can be taken into consideration to give an answer to this still unresolved question and to show the high versatility of the oxidovanadium(IV) group to act as promoter of several oxidation reactions when coordinated with a variety of ligands, including diketones like acylpyrazolones.

Synthesis, spectroscopy and biological investigations of manganese(III) Schiff base complexes derived from heterocyclic β-diketone with various primary amine and 2,2'-bipyridyl

The mixed ligand mononuclear complex [Mn(bipy)(HPMFP)(OAc)]ClO(4) was synthesized by reaction of Mn(OAc)(3)·2H(2)O with HPMFP and 2,2'-bipyridyl. The corresponding Schiff base complexes were prepared by condensation of [Mn(bipy)(HPMFP)(OAc)]ClO(4) with ethylenediamine, ethanolamine and glycine (where HPMFP=1-phenyl-3methyl-4-formyl-2-pyrazolin-5one, bipy=2,2'-bipyridyl). All the compounds have been characterized by elemental analysis, magnetic susceptibility, conductometry measurements and (1)H and (13)C NMR, FT-IR, mass spectrometry. Electronic spectral and magnetic susceptibility measurements indicate square pyramidal geometry around manganese(III) ion. The thermal stabilities, activation energy E*, entropy change ΔS*, enthalpy change ΔH* and heat capacity of thermal degradation for these complexes were determined by TGA and DSC. The in vitro antibacterial and antifungal activity of four coordination compounds and ligand HPMFP were investigated. In vitro activates of Bacillus subtillis (MTCC-619), Staphylococcus aureus (MTCC-96), Escherichia coli (MTCC-722) and Klebsiella pneumonia (MTCC-109) bacteria and the fungus Candida albicans (ATCC-90028) were determined. All the compounds showed good antimicrobial activity. The antimicrobial activities increased as formation of Schiff base.

Synthesis, spectral, crystallography and thermal investigations of novel Schiff base complexes of manganese (III) derived from heterocyclic beta-diketone with aromatic and aliphatic diamine

The Schiff base tetradentate ligands N,N-bis-(3,5-dimethyl-1-p-tolyl-1H-pyrazol-4-ylmethylene)-ethane-1,2-diamine (H(2)L(1)), N,N-bis-(3,5-dimethyl-1-p-sulfonyl-1H-pyrazol-4-ylmethylene)-ethane-1,2-diamine (H(2)L(2)), N,N-bis-(3,5-dimethyl-1-p-tolyl-1H-pyrazol-4-ylmethylene)-benzene-1,2-diamine (H(2)L(3)) and N,N-bis-(3,5-dimethyl-1-p-sulfonyl-1H-pyrazol-4-ylmethylene)-benzene-1,2-diamine (H(2)L(4)) were prepared from the reaction between 5-oxo-3-methyl-1-p-tolyl-1H-pyrazole-4-carbaldehyde or 4-(4-formyl-5-oxo-3-methyl-pyrazol-1-yl)-benzenesulfonic acid and o-phenylenediamine or ethylenediamine. And these are characterized by elemental analysis, FT-IR, (1)H NMR and GC-MS. The corresponding Schiff base complexes of Mn(III) were prepared by condensation of [Mn(3)(mu(3)-O)(OAc)(6)(H(2)O)(3)].3H(2)O with ligands H(2)L(1), H(2)L(2), H(2)L(3) and H(2)L(4). All these complexes have been characterized by elemental analysis, magnetic susceptibility, X-ray crystallography, conductometry measurement, FT-IR, electronic spectra and mass (FAB) spectrometry. Thermal behaviour of the complexes has been studied by TGA, DTA and DSC. Electronic spectra and magnetic susceptibility measurements indicate octahedral stereochemistry of manganese (III) complexes, while non-electrolytic behaviour complexes indicate the absence of counter ion.

Synthesis, spectral investigation and thermal aspects of coordination polymeric chain assemblies of some transition metal ions with bis-pyrazolones

A few coordination chain polymeric assemblies of the type [M(SB)(H(2)O)(2)](n).xH(2)O or [VO(SB)(H(2)O)](n).H(2)O [where M=Mn(II), Cu(II) and Zn(II), x=1; Co(II) and Ni(II) x=2, H(2)SB=(4Z,4'Z)-4,4'-(2,2'-(4,4'-methylenebis(4,1-phenylene)bis(azanediyl))bis(1-hydroxy ethan-2-yl-1-ylidene))bis(3-methyl-1-phenyl-1H-pyrazol-5(4H)-one)] have been investigated. Structural and spectroscopic properties have been studied on the basis of elemental analyses, infrared spectra, (1)H and (13)C NMR spectra, electronic spectra, magnetic measurements and thermo gravimetric analyses. FT-IR, (1)H and (13)C NMR studies reveal that the ligand (H(2)SB) exists in the tautomeric enol form in both the states with intramolecular hydrogen bonding. Magnetic moment and reflectance spectral studies reveal that an octahedral geometry has been assigned to all the prepared coordination polymers. The kinetic parameters such as order of reaction (n) and the energy of activation (E(a)) have been reported using Freeman-Carroll method. The pre-exponential factor (A), the activation entropy (DeltaS(#)), the activation enthalpy (DeltaH(#)) and the free energy of activation (DeltaG(#)) have been calculated.