Nadia M. Shuaib

Synthesis and characterization of binuclear and polymeric five-coordinate copper(II) complexes derived from 3,3′,3″-triaminotripropylamine (trpn): Crystal structure of [Cu(trpn)(N3)]ClO4 (I) and [Cu2(trpn)(tren)(NO2)(H2O)](ClO4)3 (II)

Abstract The synthesis and characterization of five-coordinate copper(II) complexes derived from 3,3′,3″-triaminotripropylamine (trpn) are described. The X-ray diffraction studies have established the structures [Cu(trpn)(N3)]ClO4 (I) and [Cu2(trpn)(tren)(NO2)(H2O)](ClO4)3 (II). Compound (I) consists of a polymeric cation chain and ClO4− counter ions. The coordination geometry of the Cu(II) centers may be described as distorted square pyramidal (SP) with the azido group at the apical site and three nitrogen donors of the trpn molecule occupy the basal sites. The CuN5 chromophore is completed by a bridging aminopropyl group of neighboring trpn ligand. Compound (II) is a dinuclear complex cation with two different cation geometries in the unit cell. The geometry of the Cu(II) binding tren ligand is close to trigonal bipyramidal (TBP), with the basal and apical sites are occupied by the four nitrogen atoms of the tren ligand. The fifth coordination site is bridged to one of the aminopropyl arms of the trpn ligand. The geometry of the second Cu(II) center may be described as close to distorted SP, where the trpn ligand is binding the Cu(II) ion via the two primary aminopropyl groups and the tertiary nitrogen. The remaining two sites are occupied by oxygen atoms of a water molecule and nitrite ion. The intramolecular Cu…Cu distance in I and II ranges from 7.55 A to 7.94 A. The visible spectra of the complexes in DMSO are consistent with the X-ray results found for I and II and show a greater tendency toward SP geometry.

Azido-amine-cobalt(III) complexes

Abstract The structures of the two complexes cis-[Co(tren)(N3)2]ClO4 (I) and trans-[Co(3,2,3-tet)(N3)2]ClO4 (II) (tren=2,2′,2″-triaminotriethylamine; 3,2,3-tet=1,10-diamino-4,7-diazadecane) have been determined by X-ray crystallography. The compounds consist of isolated complex cations [Co(tren)(N3)2]+ and [Co(3,2,3-tet)(N3)2]+ with distorted octahedral geometry and ClO4− counter ions. The two single coordinated azido ligands are arranged cis and trans in the cations of I and II, respectively. The Co–N(azido) distances vary from 1.946(3) to 1.964(3) A. The configurational geometry for these complexes were previously reported based on the position of the asymmetric stretching mode of vibration of the coordinated azido ligands, νa(N3) in the 2000–2065 cm−1 region. The results of X-ray studies are consistent with the previous assigned geometry based on the IR of νa(N3) and strongly support its use as a valuable tool for elucidating the geometrical isomerism in octahedral diazido metal complexes.

Interaction of Phosphate with Iron(III) in Acidic Medium, Equilibrium and Kinetic Studies

Equilibrium reactions of iron(III) with phosphate were studied spectrophotometrically by UV-Vis in the pH range of ∼ 1.0-2.20. The STAR-94 Program was used to determine the number of absorbing species as well as the stoichiometries and formation constants of the complex species. Some literature values were further confirmed and new values of different stoichiometries were obtained. The kinetics and mechanism of Fe(III) with phosphate were studied in acidic medium. The reactive phosphate species were found to be only H3PO4 and H2PO− 4 and for Fe(III) were only Fe3+, FeOH2+ and Fe(OH)+ 2. The observed rate constants were pH as well as Tphos (total concentration of phosphate) dependent, i.e. Kobs,i = A i + B i Tphos + C i T2 phos (at a given pH).

Complexes of hydroxamates VI: Binary and ternary complexes involved in the palladium(II) monohydroxamic acids—glycylglycine systems

Abstract Binary complexes of dl -serine-, l -histidine-, glycine-, aceto-, methionine- hydroxamic acids as well as glycylglycine (Glygly) with Pd(II) have been studied in solution. Only Pd(II) complexes with methionine hydroxamic (MX) acid were successfully studied potentiometrically because the other hydroxamic acids formed instant black precipitates. The potentiometric data for Pd(II)-MX were assessed by the SUPERQUAD program. The formation constants of only two species were determined in a limited pH range. The ternary complexes of Pd(II) with Glygly and MX were also studied, in which only two species were formed. It has been possible to determine only one species for the binary interaction of Pd(II) with Glygly, which is not usually simple to obtain in the absence of MX. The differential pulse polarographic technique was applied to the binary and ternary complexes involved in the system of Pd(II)-MX-Glygly in a wider pH range than that in the potentiometric study.

Synthesis, characterization, potentiometric and thermodynamic studies of transition metal complexes with 1-benzotriazol-1-yl-1-[( p -methoxyphenyl) hydrazono]propan-2-one†

A new series of Mn2+ and Co2+ complexes with 1-benzotriazol-2-yl-1-[(p-methoxyphenyl)-hydrazono]propan-2-one (BMHP) were synthesized and characterized by the elemental analysis, magnetic and different spectral techniques. Proton dissociation constant of the free ligand and the stepwise stability constants of its metal complexes were determined potentiometrically in 0.1 M KC1 and 40% (v/v) ethanol–water. The dissociation constants of the free ligand and its metal complexes were determined at different temperatures and the corresponding thermodynamic parameters were calculated and discussed. The dissociation process was found to be non-spontaneous, endothermic and entropically unfavorable. The changes in the standard ΔG 0 and ΔH 0 accompanying complexation were decreased with increasing metal ionic radius but increased with increasing electronegativity, ionization enthalpy, and hydration enthalpy of the metal ion. The values of (−ΔG 0) and (−ΔH 0) were in the order: Mn2+ < Co2+ < Ni2+ < Cu2+, in accord with the Irving-Williams order. The complexes were found to be stabilized by both enthalpy and entropy changes and the results suggest that complexation is an enthalpy-driven process. The distribution diagrams of the complexes in solution were evaluated. †Presented at the 37th International Conference of Coordination Chemistry (37th ICCC), Cape Town, 13–18 August, 2006.

Synthesis, characterization, and biological activity of N-methyl-2-(1H-1,2,3-benzotriazol-1-y1)-3-oxobutan- ethioamide complexes with some divalent metal (II) ions.

A new series of Zn2+, Cu2+, Ni2+, and Co2+ complexes of N1-methyl-2-(1H-1,2,3-benzotriazol-1-yl)-3-oxobutanethioamide (MBOBT), HL, has been synthesized and characterized by different spectral and magnetic measurements and elemental analysis. IR spectral data indicates that (MBOBT) exists only in the thione form in the solid state while 13C NMR spectrum indicates its existence in thione and thiole tautomeric forms. The IR spectra of all complexes indicate that (MBOBT) acts as a monobasic bidentate ligand coordinating to the metal(II) ions via the keto-oxygen and thiolato-sulphur atoms. The electronic spectral studies showed that (MBOBT) bonded to all metal ions through sulphur and nitrogen atoms based on the positions and intensity of their charge transfer bands. Furthermore, the spectra reflect four coordinate tetrahedral zinc(II), tetragonally distorted copper(II), square planar nickel(II), and cobalt(II) complexes. Thermal decomposition study of the complexes was monitored by TG and DTG analyses under N2 atmosphere. The decomposition course and steps were analyzed and the activation parameters of the nonisothermal decomposition are determined. The isolated metal chelates have been screened for their antimicrobial activities and the findings have been reported and discussed in relation to their structures.

Synthesis and spectroscopic studies of copper(II) complexes with 1-benzotriazol-1-yl-1-[(p-X-phenyl)hydrazono] propan-2-one

A new series of copper(II) complexes resulted from the reaction of CuCl2·2H2O or Cu(ClO4)2·6H2O and 1-benzotriazol-1-yl-1-[(p-X-phenyl)hydrazono]-propan-2-one, X = H (HL1), Cl (HL2), Br (HL3), OCH3 (HL4) and CH3 (HL5) have been synthesized and characterized by different spectral, magnetic measurements and elemental analysis. IR spectral data indicate that: (i) the free ligands exist in the hydrazo-ketone rather than azo-enol form in the solid state. Furthermore, the hydrazo-NH exists as hydrogen bonded to the keto-oxygen either as intra- or as intermolecular hydrogen bond. (ii) All ligands are neutral bidentate, coordinated to the copper(II) via hydrazone-nitrogen and the keto-oxygen atoms, and (iii) the ionic nature of and coordinated and/or non-coordinated solvent molecules (H2O or EtOH) with the possibility of hydrogen bonding with either the oxo-anions and/or triazole-nitrogen. The magnetic and spectral (UV/Vis and ESR) data indicate that these complexes have square planar, trigonal bipyramidal octahedral and tetrahedral structures. The nature of metal–ligand bonding is determined from the different electronic and ESR spectral parameters. The extent of distortion from ideal symmetry is also estimated and related to the electronic effects of the p-substituents, the nature of the ligand and counter ions.

Ionization of some derivatives of benzamide, oxamide and malonamide in DMF–water mixture

The ionization of six compounds of bis-phenolic amides was studied spectrophotochemically in DMF-water mixture. The compounds showed two pK(a) values in the range of 5.97-7.32 for pK(a(1)) and 7.61-8.44 for pK(a(2)). The obtained values of K(a) were normalized using the distribution diagrams of the different species and found to be in the range of 5.81-7.42 for pK(a(1)) and 7.48-8.27 for pK(a2).

THE BINDING AFFINITY OF Fe(III) TO ASPARTIC ACID AND GLUTAMIC ACID MONOHYDROXAMATES

The solution spectra of Fe(III) complexes with aspartic acid (ASX) and glutamic acid (GLX) monohydroxamates were analyzed in the UV-Vis region for different complex species using STAR-94 programs in the pH range ¨ 1.0-4.0, at ionic strength (I) of 0.15 M NaCl and T = 25°C. Several monomeric complex species were obtained including some mixed hydroxo species. The reaction kinetics of the Fe(III)-(ASX or GLX) systems were carried out at I = 0.15 M NaCl and T = 25°C in the time range of the stopped-flow method. The pseudofirst-order rate constants were pH as well as T L (analytic concentration of ASX or GLX) dependent, i.e. k obs,i = Ai + B i TL (at a given pH i ) where Ai and Bi are pH-dependent parameters.

Complexes of vitamin B6—part XXII. The interaction of vitamin B6 compounds with CUII-glycinehydroxamic acid binary system☆

Abstract Binary complexes of the glycinehydroxamic acid (GX) with copper(II) (GX-Cu II ), as well as their interaction with vitamin B 6 compounds [pyridoxol (P), pyridoxal (PL) and pyridoxamine (PM)] were studied by pH-metric, differential pulse polarography (DPP), and electron paramagnetic resonance techniques at the ionic strength of 0.15 M NaCl and at 25°C. The formation constants of the binary and ternary species were determined using the SUPERQUAD program. The three ternary systems do not show the same stoichiometries of the different species, in addition, PL interacts with GX to form Schiff bases at pH > 4.5. Comparative studies of the DPP of the binary and ternary systems of Cu II revealed that Cu II is more stabilized toward reduction in the presence of PM than in presence of GX at pH > 6.0; in addition the redox behaviour of Cu II in the presence of PM is similar to that of the GX-Pm-Cu II ternary system. On the other hand, the DPP of the ternary systems GX-P (or PL)-Cu II are similar to those of GX-Cu II binary system at different pH values. The nuclear spin-electron spin coupling of Cu II in these systems is discussed.