Emine Coşkun

Electrochemical study of the complexes of aspartame with Cu(II), Ni(II) and Zn(II) ions in the aqueous medium

The voltammetric behaviours of aspartame in the presence of some metal ions (Cu(II), Ni(II), Zn(II)) were investigated. In the presence of aspartame, copper ions reduced at two stages with quasi-reversible one-electron and, with increasing the aspartame (L) concentration, Cu(II)L(2) complex reduces at one-stage with irreversible two-electron reaction (-0.322 V). Zn(II)-aspartame complex (logbeta=3.70) was recognized by a cathodic peak at -1.320 V. Ni(II)-aspartame complex (logbeta=6.52) is reduced at the more positive potential (-0.87 V) than that of the hydrated Ni(II) ions (-1.088 V). In the case of the reduction of Ni(II) ions, aspartame serves as a catalyst. From electronic spectra data of the complexes, their stoichiometries of 1:2 (metal-ligand) in aqueous medium are determined. The greatness of these logarithmic values is agreement with Irwing-Williams series (NiZn).

DFT and TDDFT investigation of the Schiff base formed by tacrine and saccharin

AbstractSchiff bases have many chemical and biological applications in medicine and pharmaceuticals due to the presence of an imine group (−C=N−). These bases are used in many different fields of technology, and in photochemistry because of their photochromic properties. Here, the structural and electronic properties of the Schiff base formed by tacrine and saccharin (TacSac) were explored using density functional theory with the B3LYP, M06-2X, M06L, and ωB97XD functionals in combination with the 6-311++G(d,p) basis set. The time-dependent formalism was used at the B3LYP/6-311++G(d,p) level to obtain electronic transitions. The calculations were repeated in an implicit solvent model mimicking water, using the polarizable continuum model in conjunction with a solvation model based on a density approach. The results indicate that TacSac cannot form spontaneously, but can be obtained in mild reactions. However, the resulting Schiff base displays different characteristics to its monomers. It also has the potential for use in photochemical intramolecular charge-transfer systems. Graphical AbstractIntramolecular charge transfer between HOMO and LUMO of TacSac

2-{[3-Chloro-4-(4-chloro­phen­oxy)phen­yl]imino­meth­yl}-4-nitro­phenol

In the title compound, C19H12Cl2N2O4, the imine bond length of 1.257 (6) Å is typical of a double bond. The dihedral angle between the para-nitro benzene ring and the central benzene ring is 12.06 (3)° and that between the central benzene and the para-chloro benzene ring is 73.81 (2)°. An intramolecular O—H⋯N hydrogen bond generates an S(6) ring motif. In the crystal, molecules are linked together by two pairs of C—H⋯O interactions (to the same O atom acceptor), forming inversion dimers. A short Cl⋯Cl contact [3.232 (4) Å] is observed.

Crystal structure of (E)-4-nitro-2-((2-phenoxyphenylimino)methyl)phenol, C19H14N2O4

Abstract C19H14N2O4, monoclinic, P21/c (no. 14), a = 11.8219(12) Å, b = 6.1210(4) Å, c = 22.356(2) Å, β = 94.403(8)°, V = 1612.9(3) Å3, Z = 4, Rgt(F) = 0.0545, wRref(F2) = 0.0938, T = 293(2) K.

Crystal structure of 2-{[2-meth­oxy-5-(tri­fluoro­meth­yl)phen­yl]iminomethyl}-4-nitro­phenol

In the title compound, C15H11F3N2O4, the N=C bond of the central imine group adopts an E conformation. The dihedral angle between two benzene rings is 6.2 (2)°. There is an intramolecular bifurcated O—H⋯(N,O) hydrogen bond with S(6) and S(9) ring motifs. In the crystal, molecules are linked by C—H⋯O hydrogen bonds into a helical chain along the 31 screw axis parallel to c. The –CF3 group shows rotational disorder over two sites, with occupancies of 0.39 (2) and 0.61 (2).