Synthesis and spectroscopic characterization of gallic acid and some of its azo complexes

Mamdouh S. Masoud a, Sawsan S. Hagagg a, Alaa E. Ali b, , Nessma M. Nasr c a Chemistry Department, Faculty of Science, Alexandria University,

Alexandria, Egypt b Chemistry Department, Faculty of Science, Damanhour University,

Damanhour, Egypt c Science Park for Pharmaceuticals, Faculty of Pharmacy, Alexandria

University, Alexandria, Egypt

a b s t r a c t A series of gallic acid and azo gallic acid complexes were prepared and characterized by elemental analysis,IR, electronic spectra and magnetic susceptibility. The complexes were of different geometries: Octahedral,Tetrahedral and Square Planar. ESR was studied for copper complexes. All of the prepared complexes were of isotropic nature. The thermal analyses of the complexes were studied by DTA and DSC techniques. The thermodynamic parameters and the thermal transitions, such as glass transitions, crystallization and melting temperatures for some ligands and their complexes were evaluated and discussed. The entropy change values, DS#, showed that the transition states are more ordered than the reacting complexes. The biological activities of some ligands and their complexes are tested against Gram positive and Gram negative bacteria. The results showed that some complexes have a well considerable activity against different organisms.

Keywords: Gallic acid complexes Azo derivatives IR UV spectroscopy Biological activity Thermal analysis

Published In: Elsevier B.V.

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Solvatochromaticity and pH dependence of the electronic absorption spectra of some purines and pyrimidines and their metal complexes

Mamdouh S. Masouda, Medhat A. Shakerb, Alaa E. Ali b, , Gehan S. Elasal b

a Chemistry Department, Faculty of Science, Alexandria University, Egypt

b Chemistry Department, Faculty of Science, Damanhour University, Egypt

a b s t r a c t

The solvatochromic responses of uric acid (Ua), 6-amino-2-thiouracil (ATU) and a series of their complexes dissolved in ten solvents of different polarity have been measured. The solvent-dependent UV/Vis spectroscopic absorption maxima, _max, are assigned to the corresponding electronic transitions and analyzed using SPSS program, regression analysis and Kamlet and Taft methods. The observed solvatochromism is discussed using various solute–solvent interaction mechanisms. The electronic absorption spectra of ATU were investigated in aqueous buffer solutions of varying pH and utilized for the determination of dissociation constants. The ranges of pH, where individual ionic species are predominant have been determined.

Keywords: Uric 6-Amino-2-thiouracil Complexes Solvatochromic

Dissociation constants pH-effect

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Synthesis, computational, spectroscopic, thermal and antimicrobial activity studies on some metal–urate complexes

Mamdouh S. Masoud a, Medhat A. Shaker b, Alaa E. Ali b, , Gehan S. Elasal b

a Chemistry Department, Faculty of Science, Alexandria University, Egypt

b Chemistry Department, Faculty of Science, Damanhour University, Egypt

a b s t r a c t

New sixteen uric acid metal complexes of different stoichiometry, stereo-chemistries and modes of interactions were synthesized using different metals Cr, Mn, Fe, Co, Ni, Cu, Cd, UO2, Na and K. The synthesized complexes were characterized by elemental analysis, spectral (IR, UV–Vis and ESR) methods, thermal analysis (TG, DTA and DSC) and magnetic susceptibility studies. Molecular modeling calculations were used to characterize the ligation sites of the free ligand. Furthermore, quantum chemical parameters of uric acid such as the energies of highest occupied molecular orbital (EHOMO), energies of lowest unoccupied molecular orbital (ELUMO), the separation energy (_E = ELUMO − EHOMO), the absolute electronegativity, _, the chemical potential, Pi, the absolute hardness, _ and the softness (_) were obtained for uric acid. Eight different microbial categories were used to study the antimicrobial activity of the free ligand and ten of its complexes. The results indicate that the ligand and its metal complexes possess antimicrobial properties.

The stoichiometry of iron–uric acid complex was studied by using different spectrophotometric methods.

Keywords: Uric Complexes Synthesis Spectroscopy Thermal analysis Computational

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Solvatochromic behavior of the electronic absorption spectra of gallic acid and

some of its azo derivatives Mamdouh S. Masoud a, , Sawsan S. Hagagg a, Alaa E. Ali b, Nessma M. Nasr c

a Chemistry Department, Faculty of Science, Alexandria University, Alexandria, Egypt

b Chemistry Department, Faculty of Science, Damanhour University, Damanhour, Egypt

c Faculty of Pharmacy, Alexandria University, Alexandria, Egypt

a b s t r a c t The electronic absorption spectra of gallic acid and its azo derivatives have been studied in various solvents of different polarities. Multiple regression techniques were applied to calculate the regression and correlation coefficients based on an equation that relates the wavenumbers of the absorption band maxima (_max −) to the solvent parameters; refractive index (n), dielectric constant (D), empirical Kamlet–Taft solvent parameters, _*(dipolarity/polarizability), ˛ (solvent hydrogen-bond donor acidity) and ˇ (solvent hydrogen-bond acceptor basicity). The fitting coefficient obtained from this analysis allows estimating the contribution of each type of interactions relative to total spectral shifts in solution. The dependence of _max − on the solvent parameters indicates that the obtained bands are affected by specific and non-specific solute-solvent interactions.

Keywords: Gallic acid Solvent effect Kamlet–Taft equation

Azo complexes Refractive index Dielectric constant

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Spectral, Coordination and Thermal Properties of 5-Arylidene Thiobarbituric Acids

Mamdouh S. Masoud a, Adel El-Marghany b, Adel Orabi c , Alaa E. Ali d

, Reham Sayed b. aChemistry Department, Faculty of Science, Alexandria University, Egypt.

bChemistry Department, Faculty of Education, Suez Canal University, Egypt. cChemistry Department, Faculty of Science, Suez Canal University, Egypt.

dChemistry Department, Faculty of Science, Damanhour University, Egypt.

Abstract Synthesis of 5-arylidine thiobarbituric acids containing different functional groups with variable electronic characters were described and their Co+2, Ni+2 and Cu+2 complexes. The stereochemistry and mode of bonding of 5-(substituted benzylidine)-2- TBA complexes were achieved based on elemental analysis, spectral (UV-VIS, IR, 1HNMR, MS), magnetic susceptibility and conductivity measurements. The ligands were of bidentate and tridentate bonding through S, N and O of pyrimidine nucleolus. All complexes were of octahedral configuration. The thermal data of the complexes pointed to their stability. The mechanism of the thermal decomposition is discussed.

The thermodynamic parameters of the dissociation steps were evaluated and discussed. Keywords: 5-arylidine thiobarbituric acids, complexes, NMR, Thermal analysis

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Solvatochromaticity and pH dependence of the electronic absorption spectra of

some purines and pyrimidines and their metal complexes

Mamdouh S. Masouda, Medhat A. Shakerb, Alaa E. Ali b,∗, Gehan S. Elasalb

a Chemistry Department, Faculty of Science, Alexandria University, Egypt

b Chemistry Department, Faculty of Science, Damanhour University, Egypt

abstract

The solvatochromic responses of uric acid (Ua), 6-amino-2-thiouracil (ATU) and a series of their complexes dissolved in ten solvents of different polarity have been measured. The solvent-dependent UV/Vis spectroscopic absorption maxima, _max, are assigned to the corresponding electronic transitions and analyzed using SPSS program, regression analysis and Kamlet and Taft methods.

The observed solvatochromism is discussed using various solute–solvent interaction mechanisms. The electronic absorption spectra of ATU were investigated in aqueous buffer solutions of varying pH and utilized for the determination of dissociation constants. The ranges of pH, where individual ionic species are predominant have

been determined.

Keywords:

Uric

6-Amino-2-thiouracil

Complexes

Solvatochromic

Dissociation constants

pH-effect

published in

Spectrochimica Acta Part A 79 (2011) 538–547

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