Gamil A. Al-Hazmi

Spectral, magnetic, thermal and electrochemical studies on new copper(II) thiosemicarbazone complexes

The chelation behavior of some =N(1) and NH(4) thiosemicarbazones towards copper(II) ions has been investigated. The isolated complexes are characterized by elemental analysis, magnetic moment, electronic, IR, ESR and ms spectra, and by thermal and voltammetric measurements. The substituents on =N(1) and/or NH(4) thiosemicarbazones and the log K values of the ligands play an important role in complex formation. The IR spectra showed that the reagents HAT, HAET, HAPT, HApClPT, H2ST and HBT are deprotonated in the complexes and act as mononegative SN donors; H2SET, H2SpClPT, H2HyMBPT and H2HyMBpClPT, as binegative NSO donors while H2SPT is a mononegative NSO donor. The ESR spectra of the complexes are quite similar and exhibit axially symmetric g-tensor parameters with g ‖ > g ⊥ > 2.0023. The loss of thiol and/or hydroxyl hydrogen was confirmed from potentiometric titrations of the ligands and their copper(II) complexes. The protonation constants of the ligands as well as the stability constants of their Cu(II) complexes were calculated. Thermogravimetric analysis of the complexes suggests different decomposition steps. The Coats–Redfern and Horowitz–Metzger equations have been used to calculate the kinetic and thermodynamic parameters for the different thermal decomposition steps of some complexes. The redox properties, nature of the electroactive species and the stability of the complexes towards oxidation are strongly dependent on the substituents on the precursor NH(4) thiosemicarbazone. The redox data are discussed in terms of the kinetic parameters and the reaction mechanism.

Synthesis and spectral feature of benzophenone-substituted thiosemicarbazones and their Ni(II) and Cu(II) complexes

The ligational behavior of 2-hydroxybenzophenone and 2-hydroxy-4-methoxybenzophenone N-substituted thiosemicarbazones towards Ni(II) and Cu(II) ions has been investigated. The isolated complexes were identified by elemental analyses, molar conductance, magnetic moment, IR, UV-vis and ESR spectral studies. The IR spectra indicated that the investigated thiosemicarbazones lost the N(2) proton or the N(2) and OH protons and act as mononegative or binegative tridentate ligands. The ligands containing methoxy group facilitate the deprotonation of OH by resonance more than the SH. Most of the Ni(II) complexes measured subnormal magnetic moments due to square-planar+tetrahedral configuration and supported by the electronic spectra. The percentage of square-planar to tetrahedral was calculated and found in agreement with the ligand splitting energy (10Dq). Also, Cu(II) complexes measured subnormal values due to the interaction between copper centers; the lower the value the higher the interaction. It was found that the substitutent has a noticeable effect on the distortion of the complex. The ESR spectra of some solid Cu(II) complexes at room temperature exhibit g(parallel)>g( perpendicular)>2.0023 confirming a square-planar structure.

Synthesis, spectroscopy and thermal analysis of copper(II) hydrazone complexes

The chelating behavior of some hydrazones towards Cu(II) has been investigated. The isolated complexes were characterized by elemental analysis, magnetic moment, spectra (electronic, IR and ms) and thermal measurements. The IR spectra showed that the ligands are deprotonated in the complexes as bidentate, tridentate and binegative tridentate. Protonation constants of the ligands and the stability constants of their Cu(II) complexes were calculated. Square-planar, square-pyramidal, tetrahedral and/or distorted octahedral structures are proposed. The TGA data help to confirm the chemical formula of the complexes and indicated the steps of their thermal degradations.

Synthesis and spectroscopic characterization of cobalt(II) thiosemicarbazone complexes

Thiosemicarbazone derivatives are formed on reaction between acetophenone, salicylaldehyde, benzophenone and/or 2-hydroxy-4-methoxybenzophenone and thiosemicarbazide or its N4H substituents (ethyl-, phenyl-, and p-chlorophenyl-). The ligands were investigated by elemental analysis and spectral (IR, 1H NMR and MS) studies. The formulas of the prepared complexes have been suggested by elemental analyses and confirmed by mass spectra. The coordination sites of each ligand were elucidated using IR spectra revealing bidentate and tridentate coordination. Different geometries for the complexes were proposed on the basis of electronic spectra and magnetic measurements. The complexes have been analyzed thermally (TG and DTG) and the kinetic parameters for some of their degradation steps were calculated.

Elaborated studies on nano-sized homo-binuclear Mn(II), Fe(III), Co(II), Ni(II), and Cu(II) complexes derived from N2O2 Schiff base, thermal, molecular modeling, drug-likeness, and spectral

Abstract A series of new homo-binuclear nano Mn(II), Fe(III), Co(II), Ni(II), and Cu(II) complexes were synthesized using a Schiff base ligand derived by condensation of p-phenylenediamine with 2-hydroxy-1-naphthaldehyde. The prepared complexes were characterized using elemental, thermal analyses, FTIR, 1HNMR, 13CNMR, UV–Vis, XRD, SEM, molar conductance, and magnetic moment measurements. FTIR spectral studies revealed the interaction of the ligand as bi-negative tetra-dentate towards Mn(II) and Fe(III) atoms, whereas the ligand molecule coordinates in neutral tetra-dentate mode towards Co(II), Ni(II), and Cu(II) ions. The geometries proposed are mainly octahedral configuration surrounds the central atoms referring to the electronic spectral data and magnetic measurements. The calculations abstracted from XRD patterns propose the nano-sized complexes. The SEM images show the nano-sized appearance of the particles except for the Ni(II)-complex. Thermo-gravimetric analysis was used to ensure the nature of the presence of solvent molecules attaching to the complexes. Molecular modeling was performed to assert the structural formula proposed for the ligand and some of its complexes. Also, drug-likeness was theoretically estimated to display the probable biological activity of the free ligand through a theoretical comparison with known drugs.

AN INVESTIGATION OF THE Cu(II) COMPLEXES OF CERTAIN CEPHALOSPORIN ANTIBIOTICS: SPECTRAL, THERMAL, AND PHOTOCHEMICAL STUDIES

ABSTRACT The following Cu(II) complexes of some cephalosporin antibiotics were synthesized and characterized: [Cu(ATB)Cl]ċ-xH2O, [Cu(ATB)2]ċxH2O and [Cu(ATB)2]ċxH2, where HATB=cephalexin, cephapirin, cefamandole, cefuroxime or cefotaxime, H2ATB=ceftazidime and x=1–4. The stoichiometries and structures of the complexes were deduced from their elemental analyses, IR and electronic spectra and thermal decomposition. Thermal stabilities of the complexes were discussed and kinetic parameters were calculated using the Coats-Redfern and Horowitz-Metzger equations. The photochemical behaviour of the complexes was investigated. Upon irradiation, the Cu(II) complex of cefamandole underwent two competitive processes, one is photodegradation, the other is intramolecular hydrogen abstraction, as indicated from the spectral changes. The remaining studied Cu(II) complexes behave similar to their corresponding free antibiotics.

SPECTRAL, THERMAL, AND PHOTOCHEMICAL STUDIES ON CERTAIN FIRST, SECOND, AND THIRD GENERATION CEPHALOSPORIN ANTIBIOTICS AND THEIR CD(II) COMPLEXES

ABSTRACT The reactions of six cephalosporin antibiotics with cadmium chloride afforded the corresponding Cd(II) complexes. The antibiotics are: cephalexin, cephapirin, cefamandole, cefuroxime, cefotaxime, and ceftazidime. Their Cd(II) complexes are of the general formulas Cd(ATB)ClċxH2O, Cd(ATB)2ċ-xH2O and Cd2(ATB)Cl2ċxH2O where ATB=the respective antibiotic, x=1–3. The complexes have been characterized on the basis of elemental analyses, IR, electronic and 1H NMR spectroscopy, thermal decomposition and photochemical behaviour. Thermogravimetry and derivative thermogravimetry (TG-DTG) have been used to study the stabilities and the thermal decomposition processes of the antibiotics and their Cd(II) complexes. In some cases, the decomposition steps could be correlated with the proper decomposition products, where possible activation energies and order of the decomposition reaction have been calculated from the thermal data. The photochemical behaviour of the antibiotics under investigation and their Cd(II) complexes have been studied. Cephalexin and cefamandole show similar behaviour upon irradiation with light of 298 nm, i.e., an appearance of a new band at long wavelength attributable to the formation of a photocyclization product. The Cd(II) complex of cephalexin exhibits high light sensitivity. Mechanisms of the photolysis of the free antibiotics and Cd-complexes are suggested.

Spectral studies on a series of metal ion complexes derived from pyrimidine nucleus, TEM, biological and γ-irradiation effect.

A series of thiouracil complexes was prepared, all the prepared compounds are investigated by all possible tools. The ligand coordinates towards two central atoms as a neutral hexadentate mode. The octahedral structure was proposed with Ni(II), Pt(IV) and UO2(II) complexes. Square-pyramidal and square planar with VO(II) and Pd(II) complexes, respectively. VO(II) complex was irradiated by using Gamma radiation to through a light on the probability of geometry changes with the effect of radiation. The parameters calculated from ESR spectra before and after γ-irradiation reflect the rigidity of the complex towards the effect. Such may discuss the unaffected biological behavior before and after irradiation. XRD patterns were carried out to emphasis on the nature of the particles and the purity of products. The ligand, Pt(IV) and Pd(II) are found in nanometer range. TEM is a sensitive tool used to justify on the microstructure and surface morphology. All the investigated compounds are in nanorange. TG curves reflect a lower thermal stability of all investigated complexes due to the presence of water of crystallization. Finally, a toxic effect was observed with all investigated complexes towards Gram positive bacterium as well as a resistant behavior was observed with Gram negative bacteria.

Spectroscopic evaluation for VO(II), Ni(II), Pd(II) and Cu(II) complexes derived from thiosemicarbazide: A special emphasis on EPR study and DNA cleavage

Some thiosemicarbazide complexes were prepared and deliberately investigated by all allowed tools. The ligand coordinates as a mono negative bidentate towards VO(II) and Ni(II) as well as a neutral bidentate towards Pd(II) and Cu(II) ions. Electronic spectral data beside the magnetic measurements facilitate the structural geometry proposal. EPR spectra of Cu(II) and VO(II) complexes were recorded in their solid state. Spin Hamiltonian parameters and molecular orbital coefficient for Cu(II) and VO(II) complexes were calculated and supporting the octahedral geometry of Cu(II) complex and a square pyramidal for VO(II) one. The biological activity investigation was studied by the use of all prepared compounds. The VO(II) and Cu(II) complexes display the susceptible biotoxicity against a gram-positive bacterium. Also, Cu(II) complex displays the same toxicity against gram-negative bacteria used. The effect of all compounds on DNA were photographed. A successive degradation for the DNA target was observed with Pd(II) and Ni(II) complexes beside their original ligand.

Thermal and photochemical behaviour of Zn(II) complexes of some cephalosporins

Zn(II) complexes of some cephalosporin antibiotics namely cephalexin, cephapirin, cefamandole, cefuroxime, cefotaxime and ceftazidime were synthesised and characterized. The stoichiometrics and the mode of bonding of the complexes were deduced from their elemental analysis, IR and electronic spectroscopies. Thermal stabilities and the photochemical behaviour of the complexes were studied. The Zn(II) complex of cephalexin exhibited a high light sensitivity. The remaining Zn(II) complexes behaved similarly to their free antibiotics, upon irradiation.