Investigation of indole chalcones encapsulation in β-cyclodextrin: determination of stoichiometry,binding constants and thermodynamic parameters

The study focuses on the formation of inclusion complexes of indole chalcone (IC) derivatives with β-cyclodextrin (β-CD), which involves absorption and steady state fluorescence spectroscopies. The formation of inclusion complexes is validated by increase in their absorbance and fluorescence intensity as well as the blue shift with increase in the concentration of β-CD in the aqueous solution. The stoichiometries and binding constants (K_in) of these complexes have been investigated by monitoring their absorbance and fluorescence spectral profiles. The data are analyzed by Benesi–Hildebrand plots as well as Job’s method, which indicate 1:1 stoichiometry of IC:β-CD complexes. Fluorescence measurements are also used to investigate the effect of temperature on the stability of inclusion complexes. Stability of IC:β-CD complexes is significantly affected with variation in substituents on the phenyl ring and temperature. It is observed that the stability of the inclusion complex decreases with increase in temperature; K_in(293 K)?>?K_in(298 K)?>?K_in(308 K)?>?K_in(318 K). All the experimental results and the geometrical data obtained using PM3 semiempirical method illustrate the partial inclusion of IC derivatives from the phenyl ring side in β-CD cavity. The binding process of IC derivatives with β-CD is found to be exothermic in nature and seems to be controlled by electrostatic and hydrophobic forces. The binding free energies calculated using semiemprical PM3 method for IC:β-CD complexes are found to be in the order: I?<?OH–I?<?Me–I?<?OMe–I?<?NH₂–I, which largely supports the findings based on the experimental binding constants.     

Individual extraction constants of some divalent metal cations in the two-phase water–nitrobenzene system

From extraction experiments and γ-activity measurements, the exchange extraction constants corresponding to the general equilibrium M²⁺(aq) + Sr²⁺(nb) ? M²⁺(nb) + Sr²⁺(aq) taking part in the two-phase water–nitrobenzene system (M²⁺ = Mg²⁺, Ca²⁺, Ba²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Pb²⁺, ${\text{UO}}_{2}^{2 +} $ , Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺; aq = aqueous phase, nb = nitrobenzene phase) were evaluated. Furthermore, the individual extraction constants of the M²⁺ cations in the mentioned two-phase system were calculated; they were found to increase in the following cation order: ${\text{UO}}_{2}^{2 + } $  < Zn²⁺, Ni²⁺ < Cu²⁺, Cd²⁺ < Co²⁺ < Mg²⁺ < Ca²⁺ < Mn²⁺, Fe²⁺ < Sr²⁺ < Pb²⁺ < Ba²⁺.     

Precipitation of mixed Ca–Ba,Ca–Cd and Ca–Mn carbonates with distinct morphologies under cooperativity of divalent metal ions and protein

According to the basic principles of biomineralization, a homogeneous precipitation process involving BSA as the matrix was used to precipitate mixed Ca–Ba, Ca–Cd and Ca–Mn carbonate particles with distinct morphologies and structures at room temperature. The structures and morphologies of these carbonates were investigated using SEM and XRD. It was found that there were distinct differences when two different kinds of divalent metal ions were simultaneously precipitated in the reacting solutions. Moreover, according to the results of FT-IR and TG-DTA, we could conclude that bovine serum albumin also affected the diverse morphologies of Ca–M carbonates besides the influence of divalent metal ions. A self-assembly process coupled with an Ostwald ripening mechanism was also discussed based on a series of time-dependent SEM observations.     

Tautomerism of uracil and 5-bromouracil in a microcosmic environment with water and metal ions. What roles do metal ions play?

The base tautomerization processes of uracil/5-bromouracil were investigated in a microcosmic environment with both H2O and Na+ (W-M environment). It was found that uracil was more stable in the W-M environment than in the microcosmic environment with only water, which suggested that the metal ions and water work cooperated to maintain the classical nucleic acid bases. However, 5-bromouracil, a chemical mutagen, was found to be less stable than uracil in the W-M environment. Why the 5-bromouracil is easier to tautomerize and therefore induce gene mutation was explained to some extent. Further research revealed that the water molecule would assist the tautomerization in the W-M environment. However, the metal ions in different regions play absolutely opposite roles: in one region, the metal ions can prevent the base from tautomerizing, whereas in another region, the metal ion can assist the tautomerization process. Furthermore, from the viewpoint of ionization of the base, it seems BrU has a stronger tendency to lose the proton at N3, which is an intrinsic consequence of the bromine atom and is not affected by the metal cation.     

Chelation of somebisazophenyl-β-diketone derivatives with lanthanide metal ions

Summary The chelation behaviour ofbisazo--diketone compounds with La, Ce, Nd, Sm, Gd, Er, and Lu ions was investigated. Composition and stability constants of the chelates have been determined by conductometric and potentiometric techniques. Electronic absorption, IR, and¹H NMR spectra as well as molar conductance and elemental and thermal analyses were used to characterize the complexes.

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Komplexierung einiger Lanthaniden mitBisazophenyl--diketon-Derivaten

Zusammenfassung Das Komplexierungsverhalten einigerBisazophenyl--diketone mit La, Ce, Nd, Sm, Gd, Er und Lu wurde untersucht. Zusammensetzung und Stabilitätskonstanten der Chelate wurden mit konduktometrischen und potentiometrischen Methoden bestimmt. Zur Charakterisierung der Komplexe wurden UV/Vis-, IR- und¹H-NMR-Spektroskopie sowie molare Leitfähigkeit, Elementaranalyse und thermische Analyse herangezogen.

     

Competing binding of metal ions with protein studied by microdialysis

A method has been established to study the competing binding of metal ions with protein by a combined technique of microdialysis with high performance liquid chromatography (HPLC). Ni2+, Cd2+, Zn2+, Cu2+ and human serum albumin (HSA) were chosen as model metal ions and protein. The experimental results show that Ni2+ and Cu2+ share a common primary binding site on HSA, and Zn2+ and Cd2+ share a different common primary binding site from them, but there is a common multi-metal binding site for all of those four metal ions. This method show advantages of fast sampling, easily to be operated and especially to be useful when ideal spectroscopic probes are not available for the study of interaction between protein and metal ions.     

Low-temperature heat capacity and thermodynamic parameters of γ-aminobutyric acid

Thermodynamic properties of γ-aminobutyric acid were studied in the temperature interval from 5.7 to 300 K using a vacuum adiabatic calorimeter. The curve C _p (T) in the mentioned temperature interval is S-shaped without any anomalies. Based on the smoothed values of heat capacity, the calorimetric entropy $ S_{m}^{0} (T) - S_{m}^{0} (0) $ and the difference in the enthalpies $ H_{m}^{0} (T) - H_{m}^{0} (0) $ were calculated and tabulated. At the standard temperature 298.15 K, these values are equal to 158.1 ± 0.3 J K^?1 mol^?1 and 23020 ± 50 J mol^?1, respectively. At temperatures from 5 to 10 K, the function C _p (T) was found to obey the Debye law C = AT ³. Contrary to what has been supposed previously, the empirical Parks–Huffman rule for estimating entropy in the homologous series was shown to be not valid for the series glycine–β-alanine–γ-aminobutyric acid.     

Mechanism of Formation and Molecular Structure of α-Halothioacetones

The mechanism of formation of -halo thioketones in reactions of haloacetones with H₂S in the presence of HCl was studied by quantum-chemical methods. The cause of failure in attempted preparation of iodo thioketone by this procedure was elucidated. The stereoelectronic structure and capability for 1,3-proto- tropic rearrangements of -halothioacetones were studied.     

Diaza-crown ethers—V: Stability constants of N,N′-disubstituted diaza-crown ether complexes with various metal ions

Stability constants have been determined at 25°C in an aqueous 0.500 M Li(ClO₄) medium by potentiometric methods using the following ligands and metal ions 1,7,10,16-tetraoxa-4,13-diazacyclooctadecane (2,2), N,N′-bis-(2-methoxyethyl)-2,2(BME-2,2), N,N′-bis-(2-hydroxyethyl)-2,2(BHE-2,2), N,N′-bis-(carbamoylmethyl)- 2,2(BCAM-2,2) and Na⁺, K⁺, Mg²⁺, Ca²⁺, Cu²⁺, Ag⁺, Cd²⁺, Pb²⁺, respectively. The magnitude of the stability constants are discussed in terms of metal ion hydration, metal ion/cavity size, hardness/softness of the various acceptors, the type of donor atom and the topology of the ligand. Comparisons are made with other cyclic and bicyclic diazapolyethers.     

Multitracer study on adsorption of metal ions on α-Fe2O3

pH dependence of the adsorption of Na, Sc, Ga, As, Se, Rb, Sr, Y, Zr, Nb, Mo, Tc, Ru, Rh, and Pd on -Fe₂O₃ from a 0.1 mol dm^–3 NaCl solution was studied by using a multitracer technique. Desorption of the metal ions from the -Fe₂O₃ with the adsorbed metal ions at pH 11 was also studied by lowering the pH of the suspensions. The desorption curve of each element was in good agreement with the adsorption curve except for Ru and Rh under conditions studied. Adsorption kinetics showed that the adsorption of most metal ions increases with shaking time before an adsorption equilibrium is attained. An increase in the adsorption was also observed with an elevation in temperature for the elements, suggesting that the adsorption is involved in chemisorption.     

Hammett constants and NMR shifts of α-acyloxy carboxamide derivatives

Geometrical structures, Hammett constants, ¹H and ¹³C chemical shift values, molecular electrostatic potential maps, and several thermodynamic parameters of α-acyloxy carboxamide derivatives (4a–o) were calculated using HF and DFT/B3LYP methods with 6-31G(d) basis set. The optimized structures were compared with analogous compound. The ¹H and ¹³C NMR shielding tensors were computed with the Gauge-Independent Atomic Orbital (GIAO) method. Comparison of the experimental ¹H and ¹³C NMR chemical shifts of 4a–o molecules with the theoretical data indicates good agreement.     

Syntheses and characterization of inorganic–organic hybrids with 4-(isonicotinamido)phthalate and some divalent metal centers

Four new inorganic–organic hybrid frameworks [Mn(L)(H₂O)₂]_n (1), {[Co(L)(H₂O)₃]·2H₂O·CH₃OH}_n (2), {[Zn(L)(H₂O)]·H₂O}_n (3) and [Cd(HL)₂]_n (4) [H₂L = 4-(isonicotinamido)phthalic acid] have been synthesized and characterized by single-crystal X-ray diffraction analysis. Complex 1 has three-dimensional (3D) structure and topology related to SrAl₂ (sra) with Schläfli symbol of (4²·6³·8). And 2 displays (3,3)-connected two-dimensional (2D) network with (4,8²) topology, while 3 exhibits a uninodal (3,3)-connected (6,3) 2D network, which is further linked by N–H?O hydrogen bonding interactions to give 3D structure with hms topology and Schläfli symbol of (6³)(6⁹·8). Complex 4 with partial deprotonated HL⁻ ligands also has a 2D network structure. In addition, the magnetic property of 1, nonlinear optical property of 3 and photoluminescence of 3 and 4 were investigated.     

Interaction of adenosine 5′ triphosphate with some dipositive metal ions and isolation and characterization of some novel solid compounds

The isolation and characterization of some dipositive metal ions-ATP complexes have been described. The isolated solid compounds have the composition Na₂M(ATP)nH₂O where n = 2 for M = Ca(II), Mn(II), Fe(II), Co(II), Zn(II) and VO²⁺; n = 3 for M = Mg(II), and n = 4 for M = Ni(II), Hg(II) and Pd(II), or Na₂M₃(ATP)₂6H₂O where M = Cu(II) and Cd(II), whereas dioxouranium(VI) ion affords NaUO₂(ATPH)2H₂O. The water soluble complexes exhibit 2:1 electrolytic behaviour which is in conformity with the constitutions suggested. The magnetic susceptibilities of the Mn(II), Fe(II), Co(II) and Ni(II) complexes suggest that they have the pseudo-octahedral geometry which fact is supported for Ni(II) and Co(II) compounds by the electronic spectra. The D_q value of ATP⁴⁻ calculated from the ligand field spectra suggest that its position in the spectrochemical series should be very close to that of H₂O. IR spectra suggest that in most of the cases the metal ions are linked both to the phosphates and to the bases [N(7)] of the adenosine-5′-triphosphate molecule.     

Cu(II) complexes of α-oximinoacetoacetarylamide thiosemicarbazones

Dimeric Cu(II) complexes of thiosemicarbaznes derived from α-oximinoacetoacetanilide (OAATS), α-oximinoacetoacet-o-toluidide (OAOTTS), α-oximinoacetoacet-p-toluidide (OAPTTS), α-oximinoacetoacet-o-anisidide (OAOATS), α-oximinoacetoacet-p-anisidide (OAPATS), α-oximinoacetoacet-o-chloroanilde (OAOCATS), α-oximinoacetoacet-m-chloroanilide (OAMCATS), α-oximinoacetoacet-p-chloroanilide (OAPCATS) and α-oximinoacetoacet-m-(2,4)xylidide (OAMXTS) having general formula [CuL]₂ are characterised by elemental analyses, IR, ESR and Reflectance spectra and magnetic susceptibilities. From the IR spectra of the complexes it is concluded that thiosemicarbazones coordinate through oxygen of oximino group and 1-nitrogen and sulphur of of thiosemicarbazide moiety, acting as tridentate ligands. The dimeric nature of the complexes is revealed by lowering in magnetic moments at room temperature (μ_eff = 1.25–1.51 B.M.). The reflectance and ESR spectra have also been discussed to understand the nature of bonding in the complexes.     

Formation constants and coordination thermodynamics for binary complexes of Cu(II) and some α-amino acids in aqueous solution

In this study, the formation constants of 1?:?1 binary complexes of Cu(II) with L-glutamic acid, L-aspartic acid, glycine, L-alanine, L-valine, and L-leucine and 1?:?2 binary complexes of L-glutamic acid, glycine and the protonation macro- and microconstants of all these amino acids were determined potentiometrically in aqueous solutions at 5.0, 20.0, and 35.0°C at a constant ionic strength of I?=?0.10?mol?L^?1 (NaClO₄). The thermodynamic parameters ΔG _f°, ΔH _f°, and ΔS _f° were determined for the protonation of all amino acids used in this study and for the complex formation reactions of them with Cu(II). The results were analysed by means of Principle of hard and soft [Lewis] acids and bases. Additionally, in order to confirm the complex formation and determine the stability constants of complexes, UV-Vis spectroscopic studies were carried out. The stability constants obtained by spectrophotometrically are confirmed by those determined potentiometrically.     

Spectrophotometric and conductometric studies on the binuclear complexes containing Fe(III) and some divalent transition metal ions—I

Binuclear complexes were first prepared by Werner [1] who observed that the colour of complexes containing both platinum(II) and platinum(IV) is much deeper than that of the corresponding mononuclear complexes of these metal ions. In the present work the reaction of the strong complex acid HFeCl₄ with 8-hydroxyquinolate chelates of Mn(II), Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) (1:1 molar ratio) gave deep black binuclear complexes; all of them contain Fe(III) ion. Conductometric measurements, electronic and vibritional spectra in addition to the analytical data have been used as a principal guide for identification and characterization of these binuclear complexes.     

The potentiometric and thermodynamic properties of some divalent metal ions with biologically active 2-phenyl-3-(2′-hydroxy-5′-methylbenzylidine)-quinazoline-4-(3h)-one Schiff’s base

The formation constants of 1: 1 and 1: 2 complexes between Co(II), Ni(II), Zn(II), Cd(II), Hg(II), Pb(II), Cu(II), Ba(II), Mg(II), Mn(II), Th(IV), and UO₂ (II) metal ions and 2-phenyl-3-(2′-hydroxy-5′-methylbenzylidine)-quinazoline-4-(3H)-one [PHBMeQ] were determined potentiometrically at 30 ± 0.1 °C and different ionic strengths (0.025, 0.05, 0.10, 0.15, and 0.20 M NaNO₃) in 60: 40 (v/v) alcohol-water solutions. The proton-ligand and metal-ligand formation constants were determined pH-metrically by the Calvin-Bjerrum titration technique. The order of stability constants was found. The negative ΔG° values suggest that the reactions occur spontaneously. Correlations between the log K ₁ values and some fundamental central metal ion properties are discussed.     

Intramolecular heterocyclization of α,β-unsaturated ketone thiosemicarbazones

Intramolecular heterocyclization of thiosemicarbazones derived from α,β-enones under acid activation of one nucleophilic center afforded previously unknown 2-(2-arylethenyl)-2,3-dihydro-1,3,4-thiadiazoles. The transformation involves the thiol tautomer of thiosemicarbazone without participation of the conjugated carbon-carbon double bond.