Effect Of Complex Formation Research Articles

The effect of complex formation on the static and frequency-dependent nonlinear optical properties: A combined experimental and theoretical investigation

A novel mixed ligand Mn(II) complex of 6-Bromopyridine-2-carboxylic acid (6Brpca) and 4,4′-dimethyl-2,2′-dipyridyl has been prepared and structurally characterized using single-crystal X-ray diffraction. The spectroscopic properties were also analyzed by using FT-IR and UV–Vis spectral techniques. The coordination complexes having transition metal ions are known to have promising optical nonlinearity behavior. Therefore, B3LYP level density functional theory was used to investigate first- and second-order hyperpolarizabilities (β and γ) and provide a deep understanding of the relation between the structure and NLO properties. The calculations of frequency-dependent α, β, and γ at frequencies of ω = 0.0856252 and 0.0428126 au. for 6Brpca and Dmdpy ligands as well as Mn(II) complex have been also carried out using B3LYP/LanL2DZ level. Especially second harmonic generation (SHG) first and second hyperpolarizabilities (β(−2ω;ω,ω) and γ (−2ω;ω,ω,0)) parameters for Mn(II) complex have been calculated as 11448 × 10−30 and 680035 × 10−36 esu, respectively. It has been determined that there is a tremendous increase in β and γ parameters when 6Brpca and Dmdpy ligands coordinate to the high spin multiplicity Mn(II) ion. Theoretical calculations revealed that the large first- and second-order hyperpolarizabilities are caused by strong intramolecular charge transfer between the transition metal and the coordinated ligands. These results indicate that the the organometallic complex under investigation is valuable candidate for optoelectronic and photonic applications.

Effect of complex formation on the mass transfer during anodic dissolution of rotating disk electrode

The effect of complexation on the mass transfer during the anodic dissolution of metal rotating disk electrode involving anions of electrolyte with the formation of stable and unstable metal-anion complexes is theoretically studied. The unstable complexes can decompose with the formation of anions, which can be involved in the electrochemical reaction, i.e. the catalytic mechanism of anodic metal dissolution is realized. The developed mathematical model enables us to solve numerically the problem without using the approximations of the Nernst diffusion layer, equal diffusion coefficients of all solution components, and the condition of equilibrium complexation reaction.For several special cases (solution within the model of the Nernst diffusion layer, equal ionic diffusion coefficients), the analytical solution of the problem was compared with the numerical one. The conditions for the limiting current of anodic dissolution are determined. The role of convection and migration of solution components is revealed.The factors that have the strongest effect on the efficiency of the catalytic mechanism of metal dissolution with the formation of unstable intermediate complex are revealed.

Experimental and computational investigation of novel dihydrated organic single crystal of 2,4,6-triaminopyrimidine and 3,5-dintrobenzoic acid: Linear and nonlinear optical response with limiting performance

Newly synthesized dihydrated organic crystal (TAP+DNB−.2H2O) of 2,4,6-triaminopyrimidine (TAP) with 3,5-dinitrobenzoic acid (DNB) was grown by slow evaporation technique and this crystal belongs to monoclinic P-1 space group. Infrared spectroscopy combined with DFT calculation has been used to confirm the presence of the expected functional group of the titular crystal. Further, the UV–Vis absorption spectroscopy has been utilized to determine various optical parameters such as excitation wavelength, optical band gap, and extinction coefficient from the point of view of optical application. In addition to this, TD-DFT/B3LYP computational theory was also applied to simulate the UV–Vis absorption spectrum for supporting the experimental result. The effect of complex formation from its constituents has been explored using frontier molecular orbitals analysis. Furthermore, the mapping of the 3D Hirshfeld surface and its related fingerprint plots were used for qualitative and quantitative analysis of the intermolecular interactions which involve among different molecular moiety in the synthesized crystal. The third-order nonlinear optical response of this molecular complex (TAP+DNB−.2H2O) have been investigated in detail using the z-scan technique with CW diode laser (520 ​nm). Also, theoretical nonlinear optical parameters have been investigated by the DFT method. The thermal characteristic of the growth dihydrate crystal has been studied by thermal gravimetric-differential thermal analysis (TG-DTA).

Effect of Complex Formation on Mass Transfer during Metal Electrodeposition on Rotating Disk Electrode

The effect of complex formation on the mass transfer during the metal electrodeposition on a rotating disk electrode from the solution containing three types of ions (metal cation, cationic complex, and non-electroactive anion) is studied theoretically. The dimensionless Nernst–Planck equations in the approximation of solution electroneutrality, which take into account the electro-diffusion and convective transfer of all types of ions and the homogeneous reaction of complex formation, are used as the mathematical model. The kinetics of electrochemical reactions is taken into account using the Butler–Volmer equations. In contrast to the known works, the approximations of the Nernst layer, equal diffusion coefficients of all types of ions, and equilibrium complex formation reaction are not used. As a result of numerical solution, the distributions of concentration, potential, and the rate of complex formation reaction are obtained at various parameters of the system under consideration. It is shown that the equilibrium and rate constants of complex formation reaction and the ratio between the diffusion coefficients of complex cation and anion have the strongest effect on the mass transfer.

Experimental and theoretical investigations on the interaction of glucose molecules with myoglobin in the aqueous solution using theoretical and experimental methods

Osmolytes are generally well-known for the stabilization of proteins. The stabilizing impact of glucose on the dynamics and structure of myoglobin was probed through molecular simulation‚ docking and spectroscopic procedures. Using thermal stability examinations, the thermodynamic folding properties, point of melting temp. (Tm ), thermodynamic enthalpy change (ΔH°) and thermodynamic entropy change (ΔS°) were determined to find out the depiction of myoglobin folding. Glucose operated as an enhancer relative to myoglobin stabilization. The quenching static model was demonstrated by fluorescence spectroscopy. There was one binding site. According to the spectroscopy analysis, glucose was capable of protecting the native structural conformation of protein as well as preventing from protein unfolding. The fluorescence spectroscopy together with simulation through molecular docking method revealed that definitely hydrogen bonding plus van der Waals forces had major contributions to the stabilization of the myoglobin–glucose complex. Hence, the direct interactions contributed slightly to the stabilization impact whereas indirect interactions resulted from the hydration arise from a molecular mechanism primarily inducing the glucose stabilizing impacts. An elevation occurred in the Tm of the myoglobin–glucose complex because of the greater H-bond creation and limited surface hydrophobic activity. Our findings indicate that glucose was capable of protecting the native conformation of myoglobin, clearly describing that glucose stabilization is preferred to be omitted from myoglobin surface. This is because water is more inclined to provide desirable interacting with myoglobin functional groups as compared to glucose. Also, MD results confirmed that the structural changes of myoglobin is the effect of complex formation with glucose. Communicated by Ramaswamy H. Sarma

Energy of Intramolecular Interactions and Structure of Metallophosphate Polycomplexes with Water Molecules and Nitrogen-Containing Compounds

The interaction energies of fragments of aluminoborophosphate chains with water molecules and nitrogen-containing compounds are calculated using a density functional theory (DFT). The conformational changes of monomer units of aluminophosphate and molecular complexes during the formation of hydrogen bonds are analyzed. The complexation of aluminoborophosphate with various nitrogen-containing compounds, which leads to the displacement of water from the chain surface, is considered, and the thermal effects of complex formation are calculated. The moisture absorption of mixtures of oligomeric aluminoborophosphate with amines was measured upon various ratios of components.

Influence of electrolysis mode, complex formation and micropassivation on the roughness of niobium and tantalum coatings

It is shown that the use of pulsed electrolysis has significant advantages compared with the stationary mode and allows obtaining coatings with a lower level of roughness. The effect of complex formation on the quality of niobium and tantalum coatings is discussed. The effect of micropassivation on the roughness of niobium coatings obtained by the electrolysis of molten salt based on an equimolar mixture of sodium and potassium chlorides has been established.

Effects of Complex Formation on Motion in DNA Binding Domains of ARFs

The auxin response factor (ARF) family is a set of DNA binding transcription factors found in the model plant Arabidopsis thaliana in addition to many other food and fuel crops. Along with two other frequently conserved domains, all ARFs contain an N‐terminus DNA binding domain (DBD) that includes a B3 DNA binding motif and a dimerization subdomain. While the structure of example DBDs have been solved, motion within this domain is poorly understood. The interplay of these domains may provide selectivity in binding to variants of target DNA constructs. Our work examines the DBDs of ARF1 and ARF5, a transcription repressor and transcription activator respectively, as ARF5 is known to be more permissive than ARF1 to a larger spacing between binding sites on DNA. Our work directly tests the hypothesis that the ability to bind to a broader range of DNA targets relates to observable differences in structural flexibility. We combine spectroscopic and chromatographic methods of resolving both complex formation and molecular motion for different combinations of target DNA and DBD. We utilize fluorescence spectroscopy as it resolves protein motions and associations that occur on the same timescale as the fluorescent lifetimes (~ns). Labeled proteins can also be studied at low physiological concentrations and within an aqueous buffer. We optimized the expression and purification of the protein as well as two alternative fluorophore conjugation methods to compare thiol‐reactive fluorophore labeling to a newer technique that targets the N‐terminus. Under conditions of known dissociated versus associated states, we apply both steady‐state and time‐resolved fluorescence anisotropy to sense rotational correlation times of these proteins and distinguish subdomain motions in the presence and absence of DNA. Our work demonstrates that the N‐terminal probes are more sensitive to molecular changes likely due to its placement at the hinge between the DNA binding domain and the dimerization domain. Consistent with our hypothesis, ARF5 shifts from a highly dynamic state to a more rigid state upon complex formation while ARF1 remains more unperturbed. These differences in the available structural ensemble provide valuable insights into the structural basis of target specificity as well as the interplay of these transcriptional on‐ and off‐switches.This abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

Improve Solubility of Acetamidophenol from PEG and Witepsol Suppositories via Formation of Inclusion Complex by β-Cyclodextrin with a Controlled Release Profile

Acetamidophenol (ACP) is used to treat mild to moderate pain and reduce fever, but low water solubility and poorly dissolution of this compound restricted its bioavailability. To overcome these problems and enhance the solubility of ACP, inclusion complex between ACP and β-cyclodextrin (β-CD) is formed with various mass ratios of β-CD:ACP (1:1, 1:2, 1:4, 1:8), and the effect of complex formation on solubility and release of ACP from PEG and Witepsol-based suppositories through rectal route of administration is investigated. Inclusion complexes formed with various ratios of β-CD:ACP and loaded in the formulation of suppositories by fusion method utilizing different suppository bases, i.e., Witepsol H15 and polyethylene glycol (4000, 400). FTIR, SEM, and XRD results indicate formation of inclusion complex between β-CD and ACP. Physical characteristics and in vitro drug release of the obtained suppositories are determined by several tests such as weight variation, melting point, hardness, and release rate. Results indicate that PEG-based suppositories containing β-CD:ACP 1:1 mass ratio show the best in vitro drug release characteristic which released 19.3% of ACP after 8 h.

Role of macrocyclic effect in complex formation of palladium(II) with ligands anchored on a solid support

The method for grafting dithiacrown ether and its linear analogue to the silica surface using preliminary prepared organosilicon derivative is developed. The importance of the acylation step in the process of grafting is underlined. The acylation is required to prevent sorption of platinum metals complex anions by the anion exchange mechanism, the probability of which increases due to protonation of the spacer in an acidic medium. The interaction of palladium(II) with anchored ligands in hydrochloric acid media was studied in details. The comparative study of two sorbents revealed that the macrocyclic effect plays a negligible role in binding of palladi um(II) ions. Therefore, linear ligands are preferred for the development of sorbents for molecular recognition of platinum metals ions.

Effect of complex formation by taxifolin and naringenin with Cu(i) ions on the distribution of the components of complexes in the octanol–water system

The interaction of two structurally close flavanones: taxifolin and naringenin with copper(I) ions and its effect on the distribution of flavonoids and the corresponding ions in a biphasic system octanol–water have been studied. It has been shown that these polyphenols form complexes with copper ions of different stoichiometric ratio depending on the pH of medium (5.4, 7.4, and 9.0). The interaction of the flavonoids with copper ions leads to an increase in the fraction of polyphenols in the water phase at all pH values examined. The fraction of metal ions in octanol in the presence of both taxifolin and naringenin is maximal in the range of neutral pH values. The parameters obtained in the study, such as the partition coefficient and the coefficient of distribution in a biphasic system octanol–water (logP and logD) form the physicochemical basis necessary for the estimation of the bioavailability of flavonoids and the corresponding metal ions upon their combined consumption.

Adsorption of Polycomplexes at Solution/Air Interface

<p>The effect of complex formation of polyacids (polyacrylic (PAAc) and polymethacrylic (PMAAc)) with polyacrylamide (PAA) on their surface properties at solution/air interface has been studied by surface tension, electric conductivity and potentiometric measurements at 293±0.2 K. The relaxation time and surface activity of polycomplexes were calculated from kinetic data on the surface tension. It was found that during complex formation the relaxation time of a surface layer has a maximum and the surface activity of macromolecules is increased. Also the standard free energy of adsorption for PAA and polyacid-PAA polycomplexes were calculated. They are equal DadsG°<sub>293</sub> = - 19.1±0.1 kJ/base-mol. for PAA, DadsG°<sub>293</sub> = -21.2±0.1 kJ/basemol. for PMAAc-PAA polycomplex and DadsG°<sub>293</sub> = -23.0±0.1 kJ/base-mol. for PAAc-PAA polycomplex (calculation per base-mole of PAA monomer link). It is shown that the surface activity and ability to decrease of the water surface tension is less for PMAAc-PAA than for PAAc-PAA. Such anomalous behaviour of PMAAc-PAA polycomplex probably is caused by an excessive strengthening of inner- and intermolecular hydrophobic interactions in macromolecules of PMAAc- PAA polycomplexes due to the presence of α-methyl groups in PMAAc macromolecules. Because of the rebuilding of macromolecule segments of complex by polarity at the interface is becoming a difficult one.</p>

Stability of furosemide polymorphs and the effects of complex formation with β-cyclodextrin and maltodextrin

The effect of the formation of supramolecular binary complexes with β-cyclodextrin and maltodextrin on the chemical and physical stability of the polymorphs I and II of furosemide was evaluated in solid state. The solid samples were placed under accelerated storage conditions and exposed to daylight into a stability chamber for a 6-month. Chemical stability was monitored by high performance liquid chromatography, while the physical stability was studied by solid state nuclear magnetic resonance, powder X-ray diffraction and scanning electron microscopy. Changes in the physical appearance of the samples were evaluated. The studies showed a significant stabilizing effect of β-cyclodextrin on furosemide form II. Our results suggest that the complex formation is a useful tool for improving the stability of furosemide polymorphs. These new complexes are promising candidates that can be used in the pharmaceutical industry for the preparation of alternative matrices that improve physicochemical properties

Selective colorimetric sensing of fluoride in an aqueous solution by amino-naphthoquinone and its Co(ii), Ni(ii), Cu(ii) and Zn(ii) complexes – effect of complex formation on sensing behaviour

The complexation of metal ions with amino-naphthoquinone was found to not only enhance the HBD property of the N–H group but also accomodates ≥50% of water in the sensing medium.

The effect of complex formation on the sorption and transport of mercury(II) ions in ion-exchange membranes

The sorption and transport processes in electromembrane systems containing aqueous solutions of sodium chloride and mercury(II) chloride and MC-40, MA-40, and MA-41 ion-exchange membranes have been studied. The concentrations of complex species present in the contacting solutions have been calculated. It has been found that mercury is absorbed as a constituent of neutral and negatively charged complex particles by the anion-exchange membranes only. The specific interaction of mercury with the functional groups of the MA-40 anion-exchange membrane has been confirmed by IR spectroscopy, conductometry, and the measurements of the hydration properties of the membranes.

Effect of complex formation on nonlinear optical parameters of dye-graphene system

Abstract The effect of saturable absorption in a dye decreases significantly in the presence of functionalized hydrogen-induced exfoliated wrinkled graphene (f-HEG). The absorption spectra give strong evidence of complex formation in the ground state. The fluorescence spectra and nonlinear optical properties of the dye are affected by f-HEG and silver decorated graphene (Ag-f-HEG) by various degrees. The open aperture Z-scan and degenerate four wave mixing (DFWM) techniques have been used to record the drastic changes in the nonlinear optical parameters of dye in presence of f-HEG and Ag-f-HEG. The results indicate a reduction in the average value of the nonlinearity due to formation of the non-fluorescent ground-state charge-transfer complex. At high input irradiance the optical limiting capability of the dye-f-HEG system has been found to be enhanced. The pre-existing charge transfer between silver nanoparticles and f-HEG reduces the strength of dye-f-HEG complex formation.

The Resistivity Logging Response through Casing of Six-Layer Formations

Because difference of formation model affects the potential distribution on the metal casing, the resistivity logging response can be obtained through casing by measuring the potentials on the metal casing. In fact, the logging responses are the comprehension effects of complex formation and metal casing, so that in the coefficients of transmission line equation, we should consider the effects of formation model in radial-direction. In the following, for the formation taking on six-layer in axial-direction, and step in radial-direction, the resistivity logging responses through casing are researched and discussed, and given the recurrence formula to compute potential. Draw the curve of the resistivity logging response through casing of six-layer formations. The conductivity of formation is computed is very approximating to that of formation model. The computing examples also show that this method has a fast computing speed (the run time of computing example is less than 1s). For analysis the logging response of six-layers and block formations, and the design of logging instruments, the research is important significance and useful.

The Logging Response of Step Conductivity Formations both in Axial and in Radial

Because difference of formation model affects the potential distribution on the metal casing, the resistivity logging response can be obtained through casing by measuring the potentials on the metal casing. In fact, the logging responses are the comprehension effects of complex formation and metal casing, so that in the coefficients of transmission line equation (TLE), we should consider the effects of formation model in radial-direction. In the following, for the formation taking on six-layer in axial-direction, and step in radial-direction, the resistivity logging responses through casing are researched and discussed, and given the recurrence formula to compute potential. Draw the curve of the resistivity logging response through casing of six-layer formations. The conductivity of formation is computed is very approximating to that of formation model. The computing examples also show that this method has a fast computing speed (the run time of computing example is less than 1s). For analysis the logging response of six-layers and block formations, and the design of logging instruments, the research is important significance and useful.

The Resistivity Logging Response through Casing of Eight-Layer Formations with Cement Sheath

Because difference of formation model affects the potential distribution on the metal casing, the resistivity logging response can be obtained through casing by measuring the potentials on the metal casing. In fact, the logging responses are the comprehension effects of complex formation with cement sheath and metal casing, so that in the coefficients of transmission line equation (TLE), we should consider the effects of formation with cement sheath model in radial-direction. In the following, for the formation with cement sheath taking on eight-layer in axial-direction, and step in radial-direction, the resistivity logging responses through casing are researched and discussed, and given the recurrence formula with cement sheath to compute potential. Draw the curve of the resistivity logging response through casing of eight-layer formations with cement sheath. The conductivity of formation is computed is very approximating to that of formation with cement sheath model. The computing examples also show that this method has a fast computing speed (the run time of computing example is less than 1s). For analysis the logging response of eight-layers and block formations with cement sheath, and the design of logging instruments, the research is important significance and useful.

The Logging Response of Step Conductivity Formations with Crude Oil Emulsion Both in Axial and in Radial

Because difference of formation model affects the potential distribution on the metal casing, the resistivity logging response can be obtained through casing by measuring the potentials on the metal casing. In fact, the logging responses are the comprehension effects of complex formation with Crude oil emulsion and metal casing, so that in the coefficients of transmission line equation (TLE), we should consider the effects of formation model in radial-direction. In the following, for the formation with Crude oil emulsion taking on five-layer in axial-direction, and step in radial-direction, the resistivity logging responses through casing are researched and discussed, and given the recurrence formula with Crude oil emulsion to compute potential. Draw the curve of the resistivity logging response through casing of five-layer formations. The conductivity of formation with Crude oil emulsion is computed is very approximating to that of formation model. The computing examples also show that this method has a fast computing speed (the run time of computing example is less than 1s). For analysis the logging response of five-layers and block formations, and the design of logging instruments, the research is important significance and useful.