Miniglass,an interactive program for the evaluation of stability constants of metal/ligand complexes from potentiometric data

MINIGLASS is a microcomputer program for the treatment of pH titrations for evaluation of stability constants and adjustment of the parameters defining the titration curve. The program is written in PASCAL for the HP-200 computer series, and contains procedures for blank titrations, acidity constants and metal/ligand stability constants. Graphics support is provided for easy interaction with the user. The data files can be written by the editor of the operating system or can be created automatically from an automatic titration system. The program is tested for the determination of the formation constants of the well-studied Ni²⁺/glycine system. The results obtained agree well with literature values.     

POLAG-a general computer program to calculate stability constants from polarographic data

A general computer program, POLAG, that will calculate stability constants from polarographic data, has been written. The program requires no pretreatment of the experimental data. Any equilibrium model, consisting of species having the general formula M(m)H(j)(OH)(k)L(n)L'(p) may be fitted to the data. The performance and versatility of POLAG has been demonstrated by reprocessing polarographic data previously published by four different research groups.     

Multiparametric curve fitting-XI: POLET computer program for estimation of formation constants and stoichiometric indices from normalized potentiometric data

The FORTRAN computer program POLET(84) analyses a set of normalized potentiometric titration curves to find a chemical model, i.e., the number of species present and their stoichiometry, and to determine the corresponding stability constants log beta(pqrs) and unknown stoichiometric indices p, q, r, and s of up to quaternary M(p)L(q)Y(r)H(s) complexes. The program belongs to the ABLET family, based on the LETAG subroutine, and can use an algorithmic and/or heuristic minimization strategy, or a beneficial combination of both. The data, a set of potentiometric titration curves plotted as volume and potential, are converted into normalized variables (formation function, pH) and then a computer-assisted search for a chemical model by POLET(84) is applied. The procedure for efficient application of POLET(84) in an equilibrium analysis is described and the program is validated by use of literature and simulated data. The reliability of the chemical model and its parameters is established by the degree-of-fit achieved, and the closeness of the stoichiometric indices to integral values.     

Miniquad-A general computer programme for the computation of formation constants from potentiometric data

A new computer programme for the computation of formation constants of complex species in solution is presented. The programme can be applied to all kinds of potentiometric titration data, including multi-reactant and multi-electrode systems. A statistical analysis is made of the results in order to assess their validity, and to assist in hypothesis testing.     

An improved scoring function for suboptimal polar ligand complexes

Learning strategies can be used to improve the efficiency of virtual screening of very large databases. In these strategies new compounds to be screened are selected on the basis of the results obtained in previous stages, even if truly good ligands have not yet been identified. This approach requires that the scoring function used correctly predicts the energy and geometry of suboptimal complexes, i.e. weak complexes that are not the final solution of the screening but help direct the search toward the most productive regions of chemical space. We show that a small modification in the treatment of the solvation of polar atoms corrects the tendency of the original Autodock 3.0 scoring function to bury ligand polar atoms away from solvent, even if no complementary groups are present in the target and improves the performance of Autodock 3.0 and 4.0 in reproducing the experimental docking energies of weak complexes, resembling the suboptimal complexes encountered in the intermediate stages of virtual screening.     

A general computer approach for calculating rate constants from near-equilibrium kinetic studies

A general computer approach for estimating rate constants from relaxation times is described. The programme CORNEK is essentially a least-squares refinement programme applied to non-linear systems. It uses directly the differential forms of the first derivatives of mass-balance and rate equations, thus avoiding the time-consuming derivations of near-equilibrium rate equations. The programme has been tested for binary systems such as Cu-histamine, Cu-serine, and the ternary system Cu-histamine-serine.     

A desk computer program for the calculation of rate constants

A desk computer program has been written in BASIC programming language to optimize the values of rate constants determined from kinetic measurements of time and concentration data. The program is capable of the simultaneous refinement of a maximum of 5 rate constants. A FORTRAN version using the Gear method is also available.

---

, BASIC , . 5 . FORTRAN .

     

Prediction of formation constants for actinide complexes in solution

A numerical treatment for predicting the formation constants of actinide complexes from the properties of the metal ion and the ligand is presented. Comparison of predicted and averaged literature values of the formation constants shows excellent agreement, and the method will be most useful for modelling transport from radioactive waste repositories.     

CONSEL, a least-squares program for estimating stability constants from polarographic data

This article describes CONSEL, a least-squares linear-regression program which, when applied to polarographic data, provides estimates of stability constants suitable for priming non-linear optimization programs. The use of CONSEL avoids the need for recourse to traditional graphical methods. The results of its application to three systems are presented.     

Spectrophotometric determination of formation constants of various types of complexes by use of another competing ligand

A method has been developed for determining the formation constants of various colored complexes, ML and ML₂, and their protonated forms, spectrophotometrically, by measuring the absorbance of all forms of the colored complexes in the absence and presence of another ligand, Y, which forms the colorless complex MY, with a known formation constant. This method is based on the competition between the two ligands, L and Y, for the metal ion. An experimental test has been done for the Zn(II)-4-(2-pyridylazo)resorcinol (PAR) (H₂L) system by using nitrilotriacetic acid (NTA) as another ligand, Y. The results showed that the concentrations of PAR used were suitable for the study of 1:2 complexes, ZnL₂, ZnL(HL) and Zn(HL)₂, but were too high to study the 1:1 complexes. With the aid of the formation constants of ZnL and ZnHL determined previously, the experimental data gave an approximate value for the formation constant of ZnY (Y = NTA) which agreed with the published value.     

An interactive computer program for analysis of ultrasonic modulus data on anisotropic materials

The program computes stiffness components, compliances and engineering elastic constants for composite materials, using velocity measurements taken from the ultrasonic immersion method. The method is applicable to transversely isotropic, tetragonal and orthotropic materials. A fully worked example is included.     

Chain transfer in ethylene polymerization. III. An improved method of calculating polymerization chain-transfer constants

The method of determining chain-transfer constants in polymer systems, originally developed by Mayo, has been extended to the simultaneous determination of constants for several transfer agents. The validity of various calculation methods was examined. Particular attention was devoted to the question of how precisely chain-transfer constants are known. This extended method was applied to the determination of chain-transfer constants in ethylene polymerization under conditions where the limiting molecular weight in the absence of transfer agents cannot be directly measured, and it was shown that precision is improved (uncertanty reduced) by simultaneously determining more than one transfer constant.     

A program for evaluating equilibrium constants from spectrophotometric data by non-linear regression analysis

A new program, CFTSP, is described for computing stability constants and molar absorptivities from data on the absorbances of mixtures of a metal ion with a ligand. It is written in FORTRAN 77, can run on personal computers, and has facilities for interactive data analysis and presentation that ease the operator's task in searching for the equilibrium model that best fits the experimental data. A critical evaluation of the performance of the program is presented, and some general criteria for selecting equilibrium parameters, making use of both synthetic and experimental data, are described.     

Minipol, a desk-computer program for refinement of protonation constants from differential-pulse polarographic data

The program MINIPOL, designed to run on a desk-computer with 32 kbytes of memory, can calculate the optimum values of overall protonation constants and molar intensities of up to 8 species with composition H_XXXL_ρ, from differential-pulse polarographic data.     

SPECA: a program for the calculation of thermodynamic equilibrium constants from spectrophotometric data

A computer program called SPECA and written in compiled BASIC (Microsoft QuickBasic Ver. 4.5) has been written for the calculation of thermodynamic constants in solution equilibria studies from spectrophotometric measurements. In order to calculate the thermodynamic constants it is necessary to introduce different theories to estimate the activity coefficients of the system involved under investigation. In this version of the program the equations proposed in the models of Debye-Hückel. Specific Interaction Theory (SIT) or the Modified's Bromley Theory can be chosen. To achieve its purpose, the program uses absorbance and activity or free concentration data of one of the components, normally H(+), and it is not limited with respect to the number of components that can be studied. Minimization of the error square sum in the absorbance, which can be absolute or relative, is carried out using the Levenberg-Marquardt-Nash algorithm at three different levels: equilibrium constants in the first level, molar absorptivities in the second and interaction coefficients in the third for those systems using the SIT or the Modified Bromley's Theories.     

Determination of the equilibrium formation constants of two U(VI)-peroxide complexes at alkaline pH

The formation of uranyl-peroxide complexes was studied at alkaline media by using UV-Visible spectrophotometry and the STAR code. Two different complexes were found at a H(2)O(2)/U(VI) ratio lower than 2. A graphical method was used in order to obtain the formation constants of such complexes and the STAR program was used to refine the formation constants values because of its capacity to treat multiwavelength absorbance data and refining equilibrium constants. The values obtained for the two complexes identified were: UO(2)(2+) + H(2)O(2) + 4OH(-) UO(2)(O(2))(OH)(2)(2-) + 2H(2)O: log β°(1,1,4) = 28.1 ± 0.1 (1). UO(2)(2+) + 2H(2)O(2) + 6OH(-) UO(2)(O(2))(2)(OH)(2)(4-) + 4H(2)O: log β°(1,2,6) = 36.8 ± 0.2 (2). At hydrogen peroxide concentrations higher than 10(-5) mol dm(-3), and in the absence of carbonate, the UO(2)(O(2))(2)(OH)(2)(4-) complex is predominant in solution, indicating the significant peroxide affinity of peroxide ions for uranium and the strong complexes of uranium(VI) with peroxide.     

Bond strengths and reproportionation constants of mixed ligand complexes of lanthanones

111 mixed ligand complexes of lanthanones with nitrilotriacetic acid (NTA) and 2-hydroxy-2,4,6-cycloheptatrien-1-one (tropolone:TR) have been studied potentiometrically in 50% (v/v) aq. dioxane medium at 0.1M-NaClO₄ at 30±1°C. For these systems, complexation of primary ligand (NTA) with lanthanones is complete before complexation withTR takes place. The formation constants have been calculated by a weighted least squares method. The results show thatNTA andTR are incompatible ligands towards lanthanones and hence the mixed ligand complexes formed have lower stability than either of the parent complexes.

---

Komplexbildungskonstanten von Lanthaniden mit gemischten Liganden

Zusammenfassung Es wurden 111-Komplexe von Lanthaniden [Ln(III)] mit Nitrilotriessigsäure (NTA) und 2-Hydroxy-2,4,6-cycloheptatrien-1-on (Tropolon;TR) als gemischte Liganden potentiometrisch in 50% (v/v) wäßr. Dioxan bei 0,1M-NaClO₄ und 30±1°C untersucht. Die Komplexbildungskonstanten wurden mittels einer gewichteten Fehlerquadrat-Methode berechnet. Es zeigte sich, daßNTA undTR inkompatible Liganden gegenüberLn(III) sind und die gemischten Komplexe somit eine geringere Stabilität als die jeweiligen einfachen Komplexe haben.