• Ayman El-Faham

      Articles written in Journal of Chemical Sciences

    • Molecular structure and DFT investigations on new cobalt(II) chloride complex with superbase guanidine type ligand

      Saied M Soliman Morsy A M Abu-Youssef Jörg Albering Ayman El-Faham

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      The new [Co(btmgn)Cl2] complex and the 1,8-bis(tetramethylguanidino)naphthalene (btmgn) ligand were synthesized and characterized. The X-ray single crystal investigation showed distorted tetrahedral geometry around the Co(II) ion. The geometry of the btmgn and [Co(btmgn)Cl2] complex was optimized using the B3LYP/6–311G(d,p) method. The calculated geometric parameters at the optimized structure of the [Co(btmgn)Cl2] complex showed good agreement with our reported X-ray structure. The two tetramethylguanidino groups are in a cis-type position to the naphthalene ring plane both in the free and coordinated btmgn. The large red shift of the 𝜈C=N mode upon coordination indicates the strong ligand–metal interactions. The calculated natural charges using natural bond orbital (NBO) analysis at the two coordinated Cl-atoms are not equivalent. Also the two LP(4)Cl$\rightarrow$LP*(3)Co intramolecular charge transfer interaction energies (E(2)) are 29.00 and 39.17 kcal/mol, respectively. The two Co-Cl bonds are not equivalent where the longer Co-Cl bond has more electronegative chlorine atom than the shorter one. Molecular electrostatic potential (MEP) study of the btmgn ligand showed that the N4 and N7 atoms are the most reactive nucleophilic centers for the coordination with the Co2+ ion. The [Co(btmgn)Cl2] complex has higher polarizability (𝛼0), first hyperpolarizability (𝛽0) and lower energy gap (𝛥E) than the free ligand. The TD-DFT calculations predicted the transition bands at 337.2 nm (f=0.2299, H$\rightarrow$L) and 342.6 nm (f=0.1465, H-2/H$\rightarrow$L) for the btmgn and [Co(btmgn)Cl2], respectively.

    • Synthesis, crystallographic characterization, DFT and TD-DFT studies of Oxyma-sulfonate esters


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      Three oxyma sulfonate esters were prepared using dichloromethane-water (two-phase method) in the presence of sodium carbonate for scavenging HCl. The products were characterized by FT-IR, NMR (¹H and ¹³C), UV-Vis spectra and elemental analysis. X-ray single crystal diffraction experiments proved the molecular structures of three esters. Their molecular structures were also calculated using DFT/B3LYP method. The optimized structures agreed well with the X-ray structures. Time-dependent density functional theory (TDDFT)was used to assign the electronic absorption bands observed experimentally. Pyridine derivative showed two bands at shorter λmax compared to the others, both experimentally and theoretically. The NMR chemical shifts were computed for protons and carbons using GIAO method, which correlated well with the experimental data. Natural charges, dipole moments and chemical reactivity of these molecules, as well as their non-linear optical activity, were computed and compared.

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