Synthesis, spectroscopy, electrochemistry and thermal study of vanadyl unsymmetrical Schiff base complexes

Synthesis, spectroscopic characterization and pH dependent photometric and electrochemical fate of Schiff bases

A new Schiff base, 1-((4-bromophenylimino) methyl) naphthalen-2-ol (BPIMN) was successfully synthesized and characterized by (1)H NMR, (13)C NMR, FTIR and UV-Vis spectroscopy. The results were compared with a structurally related Schiff base, 1-((4-chlorophenylimino) methyl) naphthalen-2-ol (CPIMN). The photometric and electrochemical fate of BPIMN and CPIMN was investigated in a wide pH range. The experimental findings were supported by quantum mechanical approach. The redox mechanistic pathways were proposed on the basis of results obtained electrochemical techniques. Moreover, pH dependent UV-Vis spectroscopy of BPIMN and CPIMN was carried out and the appearance of isosbestic points indicated the existence of these compounds in different tautomeric forms.

Immobilization of cobalt(III) Schiff base complexes onto Montmorillonite-K10: Synthesis, experimental and theoretical structural determination

The [Co(naphophen)(PPh3)(OH2)]ClO4 and [Co(naphophen)(PBu3)(OH2)]BF4 (where naphophen=bis(naphthaldehyde)1,2-phenylenediimine) complexes were synthesized and chracterized by FT-IR, UV-Vis, (1)H NMR, (13)C NMR spectroscopy and elemental analysis techniques. The coordination geometry of the synthesized complexes were determined by X-ray crystallography. Cobalt (III) complexes have six-coordinated pseudo-octahedral geometry in which the O(1), O(2), N(1) and N(2) atoms of the Schiff base forms the equatorial plane. These complexes showed a dimeric structure via hydrogen bonding between the phenolate oxygen and the hydrogens of the coordinated H2O molecule. The theoretical calculations were also performed to optimize the structure of the complexes in the gas phase to confirm the structures proposed by X-ray crystallography. In addition, UV-Visible and IR spectra of complexes were calculated and compared with the corresponding experimental spectra to complete the experimental structural identification. The synthesized complexes were incorporated onto the Montmorillonite-K10 nanoclay via simple ion-exchange reaction. The structure and morphology of the obtained nanohybrids were identified by FT-IR, XRD, TGA/DTA, SEM and TEM techniques. Based on the XRD results of the new nanohybrid materials, the Schiff base complexes were intercalated in the interlayer spaces of clay. SEM and TEM micrographs of the clay/complex shows that the resulting hybrid nanomaterials has layer structures.

Novel nanohybrids of cobalt(III) Schiff base complexes and clay: synthesis and structural determinations

The [Co(Me(2)Salen)(PBu(3))(OH(2))]BF4 and [Co(Me(2)Salen)(PPh(3))(Solv)]BF(4), complexes were synthesized and characterized by FT-IR, UV-Vis, (1)H NMR spectroscopy and elemental analysis techniques. The coordination geometry of [Co(Me(2)Salen)(PPh(3))(H(2)O)]BF(4) was determined by X-ray crystallography. It has been found that the complex is containing [Co(Me(2)Salen)(PPh(3))(H(2)O)]BF(4) and [Co(Me(2)Salen)(PPh(3))(EtOH)]BF(4) hexacoordinate species in the solid state. Cobalt atom exhibits a distorted octahedral geometry and the Me(2)Salen ligand has the N2O2 coordinated environment in the equatorial plane. The [Co(Me(2)Salen)(PPh(3))(H(2)O)]BF(4) complex shows a dimeric structure via hydrogen bonding between the phenolate oxygen and hydrogens of coordinated H2O molecule. These complexes were incorporated into Montmorillonite-K10 nanoclay. The modified clays were identified by FT-IR, XRD, EDX, TGA/DTA, SEM and TEM techniques. According to the XRD results of the new nanohybrid materials, the Schiff base complexes are intercalated in the interlayer spaces of the clay. SEM and TEM micrographs show that the resulting hybrid nanomaterials have layer structures. Also, TGA/DTG results show that the intercalation reaction was taken place successfully.

Synthesis, spectral, thermal and thermodynamic studies of oxovanadium(IV) complexes of Schiff bases derived from 3,4-diaminobenzoic acid with salicylaldehyde derivatives

Synthesis and evaluation of three new oxovanadium(IV) complexes, formed by the interaction of vanadyl acetylacetonate and the Schiff bases: 3,4-bis((E)-2-hydroxybenzylideneamino)benzoic acid (L(1)), 3,4-bis-((E)-2-hydroxy-3-methoxybenzylideneamino)benzoic acid (L(2)) and 3,4-bis((E)-2,4-dihydroxybenzylideneamino)benzoic acid (L(3)) in methanol. The complexes have been characterized and studied by IR spectra, UV-Vis spectroscopy and thermogravimetry in order to evaluate their thermal stability and thermal decomposition. According to the results discussed from TG curves, the order of thermal stability for the complexes is VOL(3)>VOL(1)>VOL(2). Their formation constants (Kf) were obtained by UV-Vis spectroscopic titration at 15, 25, 35 and 45 °C in methanol by SQUAD software. The trend of formation constants of the complexes as follows: VOL(3)>VOL(2)>VOL(1).

Synthesis, spectroscopy and thermal study of some nickel(II) complexes containing tridentate Schiff bases and substituted amine ligands, X-ray crystal structure of nickel(II) complex

Some new tridentate ONO and ONS Schiff base complexes of [NiL(amine)] (L=Salicylidene2-aminophenol and Salicylidene2-aminothiophenol, amine=benzylamine, morpholine, pyrrolidine and piperidine) were synthesized and characterized by IR, UV-vis, (1)H NMR spectroscopy and elemental analysis. The geometry of [NiL(2)(bzlan)] determined by X-ray crystallography indicates that the complex has planar structure and has four coordinate in the solid state. The thermogravimmetry (TG) and differential thermoanalysis (DTA) of the synthesized complexes were carried out in the range of 20-700°C, leading to decomposition of ONO type in two stages and of ONS type in three stages. The ONO and ONS complexes were decomposed to NiO and NiS respectively. Thermal decomposition of the complexes is closely the depends upon nature of the Schiff base ligands and proceeds via first order kinetics.

Synthesis, spectroscopy, and thermal study of uranyl unsymmetrical Schiff base complexes

The new uranyl complexes with tetradentate unsymmetrical N(2)O(2) Schiff base ligands were synthesized and characterized by IR, UV-vis, NMR and elemental analysis. The DMF solvent is coordinated to uranyl complexes. The thermogravimetry (TG) and differential thermoanalysis (DTA) of the uranyl complexes were carried out in the range of 20-700°C. The UO(2)L(1) complex was decomposed in two and the others were decomposed in three stages. Up to 100°C, the coordinated solvent was released then the Schiff base ligands were decomposed in one or two steps. Decomposition of synthesized complexes is related to the Schiff base characteristics. The thermal decomposition reaction is first order for the studied complexes.

Synthesis, spectroscopy, electrochemistry and thermal study of vanadyl tridentate Schiff base complexes

The VO(IV) complexes of tridentate ONO Schiff ligands were synthesised and characterized by IR, UV-vis and elemental analysis. The electrochemical properties of the vanadyl complexes were investigated by cyclic voltammetry. A good correlation was observed between the oxidation potentials and the electron withdrawing character of the substituents on the Schiff base ligands, showing the following trend: MeO<H<Br<NO(2) and H<Cl. The thermogravimetry (TG) and differential thermoanalysis (DTA) of the VO(IV) complexes were carried out in the range of 20-700°C. The VOL(1)(OH(2)) decomposed in two steps whereas the remaining six complexes decomposed in three steps. The thermal decomposition of these complexes is closely related to the nature of the Schiff base ligands and proceeds via first order kinetics.