İclal Bulut

Study of binary complexes of Cu(II), Ni(II) and Co(II) with sulfamethazine by voltammetry

Cyclic voltammetry (CV) and square-wave voltammetry (SWV) techniques have been used to study the binary complexes of Co(II), Ni(II) and Cu(II) with sulfamethazine (SMZ) at a static mercury drop electrode (SMDE) in 0.04 M Britton-Robinson (B-R) buffer. SMZ gave three peaks at 0.01, −1.32 and −1.55 V. Cu(II)-SMZ complex was recognized by a cathodic peak at −0.38 V. Ni(II)-SMZ complex was reduced at more positive potential (−0.77 V) than that of the hydrated Ni(II) ions (−1.08 V). Co(II)-SMZ complex is investigated at pH 7 and 8. The Co(II) complex at pH 7 is appeared as a shoulder at −1.19 V, whereas this peak becomes a well-separated form at pH 8. The study indicated that the SMZ serves as a catalyst in the reduction of Co(II) and Ni(II) ions. From electronic spectra data of the complexes, their stoichiometries of 1: 2 (metal-ligand) in aqueous medium are determined. The stability constants of the complexes are in agreement with the Irwing-Williams series (Co < Ni < Cu).

Structural, spectroscopic and voltammetric studies of bis(acetazolamido)bis(aquo)bis(nicotinamide)copper(II).

Polymeric copper(II) complex, [Cu(Hacm)(2)(na)(2)(H(2)O)(2)] [H(2)acm; acetazolamide, na; nicotinamide] was synthesized and characterized by spectroscopic (IR; infrared spectroscopy, EPR; electron paramagnetic resonance), structural (XRD) and voltammetric structural (CV) methods. The copper(II) compound crystallizes in the triclinic space group P1¯, Z=1, with the unit-cell dimensions: a=7.672 (5)Å, b=8.681 (5)Å, c=11.938 (5)Å, α=90.807 (7)°, β=98.616 (5)° and γ=110.647 (5)°. The Cu(II) ion has a distorted octahedral coordination geometry. The crystal packing of the complex is stabilized by intermolecular O-H…O and N-H…O hydrogen bonds. The powder EPR spectrum of copper(II) complex have indicate that the paramagnetic center is in a tetragonal symmetry with the Cu(2+) ion having a distorted octahedral geometry. The vibrational investigation has been carried out on the basis of some characteristic IR bands of acetazolamide and nicotinamide molecules.

Synthesis, crystal structure, spectroscopic and electrochemical properties of nickel(II) dipicolinate complex with ethylisonicotinate

The diaqua(ethylisonicotinate)(pyridine-2,6-dicarboxylato)nickel(II) monohydrate complex was synthesized and characterized by spectroscopic (IR, UV/vis), X-ray diffraction and electrochemical methods. The Ni(II) ion is bonded to dipicolinate (dpc) through pyridine N atom and one O atom of each carboxylate group, two aqua ligands and N pyridine atom of ethylisonicotinate (ein), form the distorted octahedral geometry. The molecules are connected via O–H ··· O hydrogen bonds, forming motifs in three dimensional networks. IR and UV-Vis spectroscopies agree with the observed crystal structure. The voltammetric behaviour of the complex was investigated in aqueous solution by square-wave and cyclic voltammetry using a NH3/NH4Cl buffer. The square-wave voltammogram of the complex yields three reduction peaks at −0.88, −1.20 and −1.28 V. The irreversible reduction as a shoulder at −1.20 V is due to Ni-dpc-ein complex. The peak at −0.88 V corresponds to irreversible electrode process of Ni(II)-ein complex while the peak at −1.28 V is attributed to the reduction of the coordinated dpc ligands.

Simultaneous square-wave voltammetric determination of acetazolamide and theophylline in pharmaceutical formulations

Simple, rapid, sensitive and low cost voltammetric method for simultaneous determination of acetazolamide and theophylline in pharmaceutical formulations, was developed using a static mercury drop electrode (SMDE). Well-defined voltammetric peaks were obtained at–0.87 and–1.33 V for acetazolamide and–0.21 V (vs. Ag/AgCl) for theophylline in Britton–Robinson (B–R) buffer (pH 2.4). The reduction peak currents are found to be linearly dependent on the concentration for the both drugs. Calibration graphs were obtained over the concentration range 1.98 × 10–6 to 5.94 × 10–5 M and 2.0 × 10–5 to 5.6 × 10–4 M for acetazolamide and theophylline, respectively. The limits of detection (LOD) and quantitation (LOQ) of the procedure were also presented. Factors such as, pH of supporting electrolyte, equilibrium time, frequency, scan rate and pulse height were optimized. The validated voltammetric method was successfully applied for simultaneous determinations of the two drugs. The procedure does not require any sample pretreatment or timeconsuming separation steps.

Crystal structure of 2-ethyl-4-methyl-1-(2-oxido-3,4-dioxo­cyclo­but-1-en-1-yl)-1H-imidazol-3-ium

In the crystal of the inner salt of the title compound, N—H⋯O and C—H⋯O hydrogen bonds form an (9) ring motif.

Synthesis, structural and electrochemical properties of nickel(II) sulfamethazine complex with diethylenetriamine ligand.

In this study, [Ni(dien)2]⋅smz2⋅(Hsmz: sulfamethazine and dien: diethylenetriamine) complex has been synthesized and its crystal structure has been determined by X-ray diffraction technique. The title complex crystallizes in orthorhombic system with space group Pbnb [a=8.556(5), b=16.228(5), c=28.209(5)Å, V=3917(3)Å(3) and Z=4]. The nickel(II) ion has distorted octahedral coordination geometry. The metal atom, which rides on a crystallographic center of symmetry, is coordinated by six nitrogen atoms of two dien ligands to form a discrete [Ni(dien)2](2+) unit, which captures two sulfamethazine ions, each through intermolecular hydrogen bonds. The powder EPR spectrum of Cu(2+) doped Ni(II) complex was recorded at room temperature. The vibrational investigation has been carried out by considering the characteristic bands related to the functional groups of the complex. The electrochemical behavior of Ni(II) ions in the presence and in the absence of smz and dien were studied by square wave and cyclic voltammetry. A well-defined irreversible peak at -1.112V different from those of the Ni(II)-smz (-0.876V) and the Ni(II)-dien complex (-1.064V) was observed in the solution containing Ni(II) ions, which was attributed to the formation of the new mixed ligand complex of Ni(II) with smz and dien.

3-Phenylpyridinium hydrogen squarate: experimental and computational study of a nonlinear optical material

The detailed investigation of an organic nonlinear optical (NLO) squarate salt of 3-phenylpyridinium hydrogen squarate (1), C11H10N+·C4HO4(-), was reported in this study. The XRD data indicates that the crystal structure of the title compound is in the triclinic P-1 space group. In the asymmetric unit, the 3-phenylpyridine molecule is protonated by one hydrogen atom donation of squaric acid molecule, forming the salt (1). The X-ray analysis shows that the crystal packing has hydrogen bonding ring pattern of D2(2)(10) (α-dimer) through NH···O interactions. The structural and vibrational properties of the compound were also studied by computational methods of ab initio at DFT/B3LYP/6-31++G(d,p) (2) and HF/6-31++G(d,p) (3) levels of theory. The calculation results on the basis of two models for both the optimized molecular structure and vibrational properties for the 1 are presented and compared with the experimental results. Non-linear optical properties (NLO) of the title compound together with the molecular electrostatic potential (MEP), electronic absorption spectrum, frontier molecular orbitals (FMOs) and conformational flexibility were also studied at the 2 level and the results were reported. In order to evaluate the suitability for NLO applications thermal analysis (TG, DTA and DTG) data of 1 were also obtained.

The structural study of metal complexes of bisphosphonate amide ester

As a class of materials, metal phosphonates have been known for almost 30 years, but in recent years the research has expanded rapidly due to the important applications of metal bisphosphonate compounds in industrial processes such as ion-exchange, catalysis and sorption [1-3]. Recently, several metal complexes of clodronate, (dichloromethylene)-bisphosphonate, Cl2MBP, which is one of the best-documented bisphosphonates used effectively in medical applications, and its symmetrical dialkyl ester derivatives, have been prepared for studying the properties of solid materials [4]. The arrangement of metal complexes of bisphosphonates is dependent on the size of the organic group connected to the phosphonate groups, and also on the number of donor atoms of the ligand and on the degree of protonation of the phosphonate group [2]. In this study, a new, selective and simple method for the preparation of amide ester derivatives of Cl2MBP, has been developed. Four metal complexes of one of these synthesized ligands, P-piperidinium-P umethyl-(dichloromethylene)bis-phosphonate have been prepared in order to study the effect of the cyclic amine group on the complexing properties of the ligand and on the dimensionalities of its metal complexes. The compounds were crystallised by the gel method, and the structures of the complex crystals were characterized by single crystal X-ray diffraction methods, elemental analyses and thermal analyses. The methyl ester of piperidine derivative of Cl2MBP ligand forms the first wheel-like metal complex of bisphosphonate; the packing of the copper complex consist of channels occupied by aqua ligands and lattice water molecules. The complex, which has a unique hexameric structure, differs from rather common heptanuclear transition metal clusters such as Cu6Na, Co6Na, Fe6Na, Zn7, Mn7 and Cu7, where the seventh metal ion occupies the central position as a cation template. The other three compounds are polymers; Mg, Zn and Cd complexes consist of one-dimensional chains with different composition. In addition, in the case of the zinc complex, the coordinated Na cations hold the chains together forming a two-dimensional layered construction. Divalent metal cations are capable of forming different compounds with the methyl ester of piperidine derivative of clodronic acid. These kinds of structures provide new information about the ability of the amino derivatives of clodronic acid to form polymeric structures and microporous materials that can be utilized in chemical applications.