Omyma E. Sherif

PREPARATION AND THERMAL STUDY OF NEW COMPLEXES OF SALICYLIDENE-2-AMINOTHIOPHENOL SCHIFF BASES

ABSTRACT New complexes of the Schiff base salicylidene-2-aminothiophenol with VO(IV), Co(II), Ni(II), Cu(II) and Zn(II) have been synthesized and studied by thermogravimetric analysis and a general scheme of thermal decomposition of these complexes is proposed. The thermal dehydration and decomposition of these complexes were studied kinetically using the integral method applying the Coats-Redfern equation. It was found that the thermal decompositions of the complexes follow first order kinetics. The thermodynamic parameters of the decomposition are also reported.

Characterization of transition metal ion chelates with 8-(arylazo) chromones using thermal and spectral techniques

Transition metal chelates of TiO IV , VO IV , Cr III , Fe III , Co III and Pd II ions with 8-(arylazo)chromones have been isolated and investigated by elemental analysis, IR, electronic spectra, thermogravimetric analysis, conductance and magnetic moment measurements. Chelates of general formula [ML or M 2 LX m .nH 2 O].yH 2 O, where, X=OH - or Cl or SO 2 4 ion, m=1, 2 or 4, n=1, 2, 4 or 5, y=1-6, M=TiO IV , VO IV , Cr III , Fe III , Co III and Pd ions and L=8-(arylazo) chromones have been synthesized. IR spectra indicate that the chromone carbonyl in position four and oxygen anion in position five participate in chelation in the 1:1 (M:L) chelates, whereas, for 2:1 (M:L) chelates the interaction of the metal ion takes place via the chromone carbonyl in position four and oxygen anion in position five as first chelation site, for the second metal ion chelation takes place through the formyl carbonyl in position six and oxygen anion in position seven for some chelates or through the azo group and any acidic substituent in ortho position to it. Octahedral or square planar structures were proposed for the prepared chelates based on their electronic spectra and magnetic moments. Thermogravimetric analysis suggests the presence of hydrated and coordinated water molecules. Non electrolytic nature was assigned based on molar conductance values.

Separation and spectroscopic characterization of new metal chelates of 8-arylazo-6-formyl-7-hydroxy-5-methoxy-2-methyl chromones

Transition metal chelates of the title compounds have been prepared and characterized by elemental analyses, i.r., 1H-n.m.r., electronic spectra, thermogravimetric analysis, conductometric and magnetic measurements. Chelates of general formulae MLjX · nH2O for 1:1 (M:L), where X=OH− or Cl−, j=1 or 2, n=1– 4 and M=VO2+, Cr3+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+ and Zn2+ ions or ML2 for 1:2 (M:L) Ni-(1a), ML2·2H2O where M=Co2+, Ni2+ and Cu2+ or M2LjX·nH2O for 2:1 (M:L) Cr3+, Fe2+, Ni2+ and Cu2+, L=Ligand, have been prepared. I.r. and 1H-n.m.r. spectra indicate that the aldehydic group in position six and the hydroxylic group in position seven are involved in chelation in the 1:1 and 1:2 (M:L) chelates, whereas for 2:1 (M:L) chelates with (1c), the interaction of the metal ion takes place through CHO, OH, CO2H and NN groups. Tetrahedral, octahedral and square planar geometries are proposed for the chelates based on their electronic spectra and magnetic moments.

Charge–transfer complexes of pyrimidine Schiff bases with aromatic nitro compounds

Charge-transfer (CT) complexes of pyrimidine Schiff bases, derived from condensation of 2-aminopyrimidine and substituted benzaldehydes, with some aromatic polynitro compounds were prepared and investigated using IR, UV, visible and (1)H NMR spectroscopy. For all solid complexes, the main interaction between the donor and acceptor molecules takes place through the π-π* interaction. Strong and some weak acidic acceptors, in addition interact through proton transfer from the acceptor molecule to the basic centre of the electron donor. Also, an n-π* transition was detected in some complexes.

Structural studies on 3-acetyl-1,5-diaryl and 3-cyano-1,5-diaryl formazan chelates with cerium(III), thorium(IV) and uranium(VI)

SummarySolid complexes of 3-acetyl-1,5-diaryl and 3-cyano-1,5-diaryl formazans were prepared and characterized by elemental analysis, IR, NMR, TGA and DTA analyses. Based on these studies, the suggested general formula for the complexes is [M(HL)m(OH−)n or (NO3− or Cl−)x·(H2O)y or (C2H5OH orDMSO)z, where HL=formazanM=Ce3+, Th4+, and UO22+,m=1–2,n=0–3,x=0–3,y=0–4 andz=0–3. The metal ions are expected to have coordination numbers 6–8.ZusammenfassungDie hergestellten Chelate wurden mittels Elementaranalyse, IR, NMR, TGA und DTA charakterisiert. Darauf basierend wird die generelle Formel [M(HL)m(OH−)n bzw. (NO3− oder Cl−)x·(H2O)y oder (C2H5OH bzw.DMSO)z] vorgeschlagen, wobei HL=Formazan,M=Ce3+, Th4+ oder UO22+,m=1–2,n=0–3,x=0–3,y=0–4 undz=0–3. Die Metallionen haben Koordinationszahlen von 6–8.

Chelation Behaviour of Ce(III), Th(IV), and UO2(VI) with 5,7-Dihydroxy-6-formyl-2-methylbenzopyran-4-one Schiff Bases

Summary. The stability constants of the stepwise chelate formation between Ce3+, Th4+, and UO2+2 ions and some Schiff bases derived from 5,7-dihydroxy-6-formyl-2-methylbenzopyran-4-one were determined conductometrically as well as potentiometrically applying the Irving and Rossotti techniques. The results indicate the formation of 1:1 and 1:2 (M:L) chelates. The stability constants increase with decreasing ionic strength, decreasing temperature, and decreasing percentage of ethanol. In different organic solvents (70% v/v solvent-water media), the stability constant values follow the order MeOH < EtOH < 1-propanol < 2-propanol < acetone < DMSO depending on both the dielectric constant and the hydrogen bonding structure of the medium. The thermodynamic parameters (ΔG, ΔH, and ΔS) were calculated; they indicate that the chelate formation is an exothermic process and that the degree of disorder of the solution increases upon chelation.Zusammenfassung. Die Stabilitätskonstanten fr die stufenweise Chelatbildung von Ce3+-, Th4+- und UO2+2-Ionen mit von 5,7-Dihydroxy-6-formyl-2-methylbenzopyran-4-onen abgeleiteten Schiff- schen Basen wurden konduktometrisch und potentiometrisch mit Hilfe der Irving-Rossotti-Technik bestimmt. Die Ergebnisse zeigen die Bildung von 1:1- und 1:2-Chelaten (M:L) an. Die Stabilitäkonstanten steigen mit steigender Ionenstärke, abnehmender Temperatur und abnehmendem Anteil von Ethanol. In verschiedenen organischen Lösungsmitteln (70% v/v Lösungsmittel-Wasser-Gemische) folgen die Stabilitätskonstanten der Reihe MeOH < EtOH < 1-Propanol < 2-Propanol < Aceton < DMSO, hängen also sowohl von der Dielektrizitätskonstante als auch von der Wasserstoffbrückenbindungsstruktur des Mediums ab. Die thermodynamischen Parameter (ΔG, ΔH und ΔS) wurden bestimmt; sie weisen darauf hin, daß die Bildung solcher Chelate exotherm verläuft und daß und der Unordnungsgrad der Lösung bei der Chelierung steigt.

EFFECT OF SOLVENTS ON THE ELECTRONIC ABSORPTION SPECTRA OF SOME SUBSTITUTED DIARYLFORMAZANS

SummaryThe electronic absorption spectra of some substituted diarylformazans in organic solvents of varying polarities are studied. The absorption bands are assigned to the corresponding electronic transitions in the molecules. The solvent effects on the intramolecular charge transfer bands are discussed using various solvent parameters. The charge transfer nature of the bands was also confirmed by the solvent effects on the absorption spectra of some formazans. Molecular orbital calculations using MNDO-PM3 were performed and indicate atrans configuration as the favoured geometry.ZusammenfassungDie Absorptionsspektren einiger substituierter Diarylformazane werden in organischen Lösungsmitteln unterschiedlicher Polarität untersucht. Die Absorptionsbanden werden den entsprechenden Elekronenübergängen in den Molekülen zugeordnet. Die Lösungsmitteleffekte auf die intramolekularencharge-transfer-Banden werden unter Verwendung verschiedener Lösungsmittelparameter diskutiert. Diecharge-transfer-Natur der Banden wurde durch den Einfluß der Lösungsmittel auf die Absorptionsspektren einiger Formazane bestätigt. MO-Rechnungen (MNDO-PM3) wurden durchgeführt und bestätigen einetrans-Konfiguration als bevorzugte Geometrie.

THERMODYNAMIC PARAMETERS OF SOME SCHIFF BASES DERIVED FROM 5,7-DIHYDROXY-6-FORMYL-2- METHYLBENZOPYRAN-4-ONE

Potentiometric studies on Schiff bases derived from5,7-dihydroxy-6-formyl-2-methylbenzopyran- 4-one were carried out at different ionic strengths (0.02, 0.04, 0.06, 0.10 and 0.14 M NaCl), at different temperatures (25, 35, 45 and55°C) and in ethanol-water media of varying compositions (60, 70, 80 and 90% v/v). The ionization constants of the Schiff bases were investigated in the presence of different organic solvents (70% v/v), e.g. methanol, ethanol, n-propanol, isopropanol, acetone, DMSO and DMF-water media. The thermodynamic parameters (ΔG, ΔH and ΔS) were also calculated.

Preparation and Spectroscopic Investigation of Chelates of Divalent Transition Metal Ions with 8-(Arylazo)-Chromones

Abstract Metal chelates of the divalent transition metal ions Mn(II), Fe(II), Co(H), Ni(II), Cu(n), Zn(II) and Pd(II) with 8-(arylazo)chromones have been prepared and characterized by elemental analyses, IR and electronic spectra, thermogravimetric analyses, magnetic and conductance measurements. The obtained data suggest the formation of 1:1 and 2:1 (M:Ligand) chelates with the general formula [MHk-1LXmH2O)].yH2O or [M2Hk-2 LXn(H2O)n].yH2O where X = OH or Cl, m = 1 or 2, n = 1–3 or 6, y = 1–3 or 5, k = 2–4, M is a divalent transition metal ion and HkL represents the 8-(arylazo)-chromones. The study revealed that the ligands behave as monobasic bidentates in the case of 1:1 (M.Ligand) chelates and as dibasic tetradentares in the case of the 2:1 (M:Ligand) chelates. Electronic spectra and magnetic measurements indicate that the metal chelates have square-planar, tetrahedral or octahedral geometries. The TG analyses indicate the presence of hydrated and coordinated water molecules A nonelectrolytic nature w...

Preparation and Investigation of Ce(III), Th(IV) AND U(VI) Chelates with Some Schiff Bases Derived from 5,7-Dihydroxy-6-Formyl-2-Methylbenzopyran-4-One

Abstract Schiff bases were prepared by condensation of equimolar amounts of 5,7-dihy-droxy-6-formyl-2-rnethylbenzopyran-4-one and aniline, anthranilic acid, 2-aminophenol, 5-chloro-2-aminophenol or 4-amino-3-hydroxybenzenesulphonic acid. The molecular structure of the prepared Schiff bases was confirmed by mass and UV spectra. The chelates of Ce(III), Th(IV), and U(VI) with the above Schiff bases were prepared. All the prepared compounds were subjected to elemental analyses for C, H, N, Cl, S and metal (for the chelates), IR and 1H NMR spectroscopy. The studies show that Ce(III) and Th(IV) give 1:1, 1:2 and 2:1 (M:L) metal chelates, while U(VI) gives only 1:1 and 1:2 (M:L) chelates. This may be attributed to the difficulty of coordinating two bulky uranyl ions to the same molecule because of their steric effect. The studies revealed that the Ce(III) and Th(IV) chelates exhibit octahedral structure with the coordination number 6 while U(VI) chelates exhibit dodecahedral structure with the coordination numb...