Thermodynamic Characteristics Of Complexation Research Articles

Designed complexes based on betanidin and L0 Dyes for DSSCs: thermodynamic and optoelectronic properties from DFT study

ABSTRACT A combination of natural betanidin (Bd) or decarboxylated betanidin (dBd) dyes possessing efficient carboxylic anchoring groups with synthetic dye L0 containing strong electron donor triphenylamine moiety has been engineered on purpose to improve the dye’s optoelectronic properties for DSSCs application. Novel complex D–π–A organic dyes, L0–Bd and L0–dBd with structural isomers, have been designed via esterification reactions. The DFT/B3LYP5/6-31G(d,p) approach is used in computations of geometry, vibrational spectra and thermodynamic characteristics of complexes; the TD–DFT method – for optoelectronic properties. Due to the combination, broader coverage of the solar spectrum with greater light-harvesting efficiency of the designed sensitisers was achieved compared to individual dyes. The dye complexes′ attachment to the TiO2 cluster was simulated in terms of the different possible adsorption modes; binding energies and electronic spectra of the dye@TiO2 systems were computed, and electron density distributions over frontier molecular orbitals were analysed.

Structural inspection for novel Pd(II), VO(II), Zn(II) and Cr(III)- azomethine metal chelates: DNA interaction, biological screening and theoretical treatments

An alternative sequence of bioactive series, using novel Schiff base derivative (1-Quinolin-8-yliminomethyl-naphthalen-2-ol), was produced (HNQ). Elements analysis, molar conductivity, magnetic moment, IR, 1H NMR, UV-Vis, and TGA were used to define the chemical forms. As a result, an appropriate geometry has been proposed for each complex. The HNQ ligand functions as a tri-dentate via NNO donors to the metal ions within octahedral geometry with Cr3+, square pyramidal with VO2+, tetrahedral with Zn2+, and square planner with Pd2+ ion. The Coats-Redfern approach was used to determine the kinetic and thermodynamic characteristics of complexes, and their values revealed the ordered state of active complexes. The binding effectiveness of the examined compounds with calf thymus DNA (ct-DNA) was analyzed using various methods, and the binding function was assumed to be electrostatic, intercalation, or replacement mode. Furthermore, the compounds' antibacterial and anticancer efficacy was tested in vitro. In a concentration-dependent way, the chemicals had a considerable influence on lowering cell viability of breast cancer cells (MCF-7). The antioxidant activity of the compounds was examined in vitro, and the results revealed that the ligand's activity was similar to that of the reference drug. This study was reinforced by different theoretical implementations. The geometry optimization process supported the manner of ligand-metal ion interaction. The stability of complexes was shined and the reduced polarity was recorded with HNQ, HNQPd and HNQVO, which is promising in biological applications. Biological simulation was performed using Pharmit link to search on drug-like compounds and to discover the extent of interaction with DNA-protein (1bna). In addition, MOE-docking was implemented to put a clear view about the interaction features between the compounds and 1bna protein. The simulation study reveals the priority of HNQ ligand towards the DNA and the negligible role of complexes, was expected. While, comparing in-vitro with in-silico results, this difference was noticed, which may suggest a presence of any unknown mechanism improves the behavior of complexes inside living-cells.

Thermodynamics of Complexation of Sm3+ and Ce3+ Ions with L-Leucine in Aqueous Solution at 298.15 K

The enthalpies of complexation of the Sm3+ and Ce3+ ions with L-leucine at 298.15 K and an ionic strength of 0.5 (KNO3) have been determined by the calorimetric method. The thermodynamic characteristics of complexation of lanthanide ions with amino acids have been calculated. The potentiometric method was used to determine the stability constants of cerium and samarium complexes with the L-leucinate ion at 298.15 K and an ionic strength of 0.5 (KNO3).

Thermodynamic characteristics of complexation between Ho3+ and ethylenediamine-N,N'-disuccinic acid in aqueous solutions at 298.15 K

The thermodynamic characteristics of complexation between ethylenediamine-N,N'-disuccinic acid (H4Y; EDDA) and Ho3+ ion were determined calorimetrically and potentiometrically at 298.15 K and ionic strengths of 0.1, 0.5, 1.0, and 1.5 (KNO3). The logK, ΔrG, ΔrH, and ΔrS values for the formation of HoY– and HOHY complexes were calculated at the studied and zero ionic strength values. The changes in thermodynamic parameters of the reactions are discussed.

Thermodynamic characteristics of the formation of Cd2+ ion-L-serine complexes in aqueous KNO3 solutions at 288–308 K

The heats of formation of complexes of L-serine and doubly charged cadmium ions are determined by calorimetry. The heat effects of the reaction between an amino acid solution and a cadmium(II) solution and the respective heats of dilution of cadmium nitrate solution are measured at temperatures of 288.15, 298.15, and 308.15 K and ionic strengths of 0.25, 0.50, and 0.75 against the background of KNO3. The standard thermodynamic characteristics of complexation are calculated. Standard enthalpies of formation of mono-, bis-, and tris-coordinated complexes of cadmium(II) in an aqueous solution are found.

Effect of ionic strength on the thermodynamic characteristics of complexation between Fe(III) ion and nicotinamide in water-ethanol and water-dimethyl sulfoxide mixtures

Solutions of iron(III) perchlorate in water, water-ethanol, and water-dimethyl sulfoxide solvents (\(x_{H_2 O} \) = 0.7 and 0.25 mole fractions) at ionic strength values I = 0.1, 0.25, and 0.5 are studied by IR spectroscopy. Analysis of the absorption bands of perchlorate ion shows that it does not participate in association processes. It is demonstrated that in the range of ionic strength values between 0 and 0.5 (NaClO4), it affects neither the results from potentiometric titration to determine the stability constants of the iron(III)-nicotinamide complex nor the thermal effects of complexation determined via direct calorimetry in a binary solvent containing 0.3 mole fractions (m.f.) of a non-aqueous component.

Thermodynamic Characterization of Polypeptide Complex Coacervation

The interactions between a series of oppositely charged polypeptide pairs are probed using isothermal titration calorimetry (ITC) in combination with turbidity measurements and optical microscopy. Polypeptide complex coacervation is described as a sequence of two distinct binding steps using an empirical extension of a simple ITC binding model. The first step consists of the formation of soluble complexes from oppositely charged polypeptides (ion pairing), which in turn aggregate into insoluble interpolymer complexes in the second step (complex coacervation). Polypeptides have identical backbones and differ only in their charged side groups, making them attractive model systems for this work. The poly(l-ornithine hydrobromide) (PO)/poly(l-glutamic acid sodium salt) (PGlu) system is used to examine the effects of parameters such as the salt concentration, pH, temperature, degree of polymerization, and total polymer concentration on the thermodynamic characteristics of complexation. Complex coacervation in all probed systems is found to be endothermic, essentially an entropy-driven processes. Increasing the screening effect of the salt on the polyelectrolyte charges diminishes their propensity to interact, leading to a decrease in the observed energy change and coacervate quantity. The pH plays an important role in complex formation through its effect on the degree of ionization of the functional groups. Plotting the change in enthalpy with temperature allows the calculation of the heat capacity change (ΔC(p)) for the PO/PGlu interactions. Finally, ITC revealed that complex coacervation is promoted when higher total polymer concentrations or polypeptide chain lengths are used.

Calculating the solvation contributions from reagents to the change in enthalpy of silver(I) complexation with 18-crown-6 ether in binary methanol-acetonitrile solvents

The enthalpies of the transfer of silver(I) ions from methanol to mixed methanol-acetonitrile solvents are calculated using the literature data. An estimative calculation of the enthalpies of transfer of the reaction of formation of [Ag18C6]+ upon a change in the solvent composition MeOH → AN is performed on the basis of previously found laws of change in the thermodynamic characteristics of complexation and solvation of reagents. It is shown that the governing factor in the change in the energy of the reaction is the enhancement of the solvation of the central ion.

Theoretical study of donor-acceptor ability of borazine, alumazine, and boraphosphinine

Donor-acceptor complexes of borazine, alumazine, and boraphosphinine were studied by a quantum-chemical method. Structural and thermodynamic characteristics of complexes with Lewis acids (BCl3 and AlCl3) and bases (NH3 and pyridine Py) were calculated by the B3LYP method with the TZVP basis set. Energies of donor-acceptor bonds and energies of reorganization of donors, acceptors, and heterocycles upon the complex formation were found. Analysis of the energy variations occurring at the complex formation has shown that the reorganization energies of acceptors (BCl3 and AlCl3) and heterocycles play a key role in the complex stabilizations, whereas the reorganization energies of donors (NH3 and Py) are small and do not bring essential contribution to the complex-formation energy. The stability of donor-acceptor complexes decreases in the sequence alumazine > boraphosphinine > borazine. High alumazine reactivity toward chlorine atoms of the acceptor molecules BCl3 and AlCl3 was noted.

Decomposition of cumene hydroperoxide over molybdenum oxo-peroxo compounds

The features of the catalytic decomposition of cumene hydroperoxide (CHP) were studied by the pulse technique in an inert gas atmosphere over the temperature range 90–120°C and the concentration range 0.1–2.5 mol/l. As a catalyst, molybdenum(VI) oxo-peroxo compounds active in the olefin oxidation reaction were used, which were prepared from cumene hydroperoxide and hydrogen peroxide. The rate and activation parameters for the formation and degradation of the CHP-catalyst complex were determined, as well as the thermodynamic characteristics of complexation.

Thermodynamic Characteristics of Gaseous GaCl3pyz and GaCl3pyzGaCl3 Complexes

Thermodynamic characteristics of vaporization and gas-phase dissociation of the complexes GaCl3pyz and GaCl3pyzGaCl3 (pyz is pyrazine) were determined by static tensimetry with a membrane zero gage. Structural and thermodynamic characteristics of the complexes were calculated by the B3LYP/pVDZ quantum-chemical method.

Effect of the Nature of the Supporting Electrolyte on Thermodynamic Characteristics of the Formation of Zinc(II) Aminoacetates in Aqueous Solutions

The heats of formation of Zn2+ complexes with aminoacetic acid at 298.15 and at several ionic strengths of the solution in the presence of alkali metal nitrates as supporting electrolytes were determined by calorimetry. The thermodynamic characteristics of complexation of zinc(II) aminoacetates in an aqueous solution were calculated. An increase in the lithium nitrate concentration increases the exothermic effect more substantially than potassium nitrate.

Thermodynamics of nickel(II) complexation with 2-hydroxypropylene-1,3-diamine-N, N, N?, N?-tetraethanoic acid

Heat effects of formation of nickel(II) hydroxypropylenediaminetetraacetate were determined for the first time at 298.15 K and the ionic strength I = 0.1, 0.5, and 1.0(KNO3) by the direct calorimetric method. The corresponding standard thermodynamic characteristics of complexation were calculated. The results obtained were compared with published data on related compounds.

Hydrogen bond effects on the fundamental vibration frequencies of pyridine

The IR band structure and intensities, as well as normal vibration frequencies, are calculated by the density functional method using the Becke exchange functional and the Lee-Yang-Parr (B3LYP) correlation functional with the 6-311+G(d, p) basis set for pyridine and water molecules and for 1:1 and 1:2 hydrogen-bonded complexes (pyridine...H2O and pyridine...D2O). The structures of the hydrogen-bonded complexes are established. The characteristicity of the fundamental vibration frequencies and absolute IR intensities of pyridine in its hydrogen-bonded complexes is analyzed. The solvent effect is investigated within the framework of the self-consistent reactive field (SCRF) model. The thermodynamic characteristics of complexation are calculated using the modified G1, G2, and G2(MP2) models and the B3LYP/6-311+G(d, p) theoretical method including the basis set superposition error (BSSE).

Determination of the Thermodynamic Characteristics of Complexes of Chlorosubstituted Anilines with Proton Acceptors

The influence of temperature on the spectral parameters of the absorption bands ν(NH) of free and hydrogen-bonded molecules of chlorosubstituted anilines with various proton acceptors in a CCl4 medium has been studied in a temperature range of 290–330 K. The temperature dependence of the monomer–complex equilibrium constants has been investigated and the thermodynamic characteristics of the complexes have been calculated.

Thermodynamic Characteristics of Complexes with a Hydrogen Bond of Bromosubstituted Anilines with Proton Acceptors

In the range 290–330 K, the influence of temperature on the spectral characteristics of the absorption bands is studied for an amino group of bromosubstituted anilines in free molecules and in the hydrogen‐bond complexes with various proton acceptors. Using the van't Hoff formula, the thermodynamic characteristics of the complexes with the composition 1:1 are determined. It is shown that in these complexes the hydrogen bond turns out to be stronger than in those with the composition 1:2.

Temperature effects on absorption bands ν(NH) and thermodynamics of hydrogen-bonded complexes of NH-donors with proton acceptors

The temperature dependence of spectral characteristics of absorption bands ν(NH) for free and H-bonded molecules of pyrrole, indole, 2-methylindole, carbazole, benztriazole, N-methylformamide, N-methylbenzamide and N-methyltrichloroaceto-amide have been investigated in the range 290–350 K. These dependences have been demonstrated to be approximated by linear functions Y=aT+b, the parameters of linear regression equations for spectral moments Y=M (0), M (1), 2(M (2)) 1 2 having been determined. The resulting data have provided support for regularities predicted theoretically on the base of quantum mechanical calculations within the framework of three-point model of H-bond. The relationship between temperature factor ∂M c (1)/ ∂T and the of first spectral moment ΔM (1)=M m (1)-M c (1) of ν(NH) band has been studied. Complex character of this dependence was supposed to be controlled by two main factors: stretching of NH-bond and its polarization under the effect of proton acceptors. Thermodynamic characteristics of complexes with intermolecular H-bond have been inferred. The Badger-Bauer rule has been found to be incorrect for NH-donors in general case over a wide range of − ΔH and ΔM (1) magnitudes. The “intensities rules” have been tested by using more than 40 H-bonded systems including amines. For each NH-donor the proportionality between enthalpy − ΔH of H-bond and the increment of square root of integral intensity Δ B 1 2 of absorption bands ν(NH) (or the increment of dipole moment derivative with respect to normal coordinate ∂μ/ ∂Q) in moving from free molecules to bonded ones was proved to exist. However, in the same medium the coefficient of proportionality between these two values was reasoned to depend on individual proton donating ability.

Calorimetric study of complexation of calcium chloride and nitrate with 18-crown-6 in ethanol at 298.15 K

1. In the reaction of calcium nitrate and chloride with 18-crown-6, we observed the effect of the nature of the anion on the thermodynamic characteristics of complexation. 2. Although the value of the enthalpy of complexation of 18-crown-6 with calcium chloride in ethanol is 1.5 times as negative as with calcium nitrate, in the latter case the complexation constant is significantly greater because of the entropy factor.