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The chromatographic lipophilicity ( R M0 , ϕ 0 , S ) of eleven new 1,2,4-triazole derivatives has been determined by RP-TLC with methanol-water mobile phases containing sodium salts of the monovalent anions H 2 PO 4 , Cl , I , NO 3 , CF 3 COO , ClO 4 , and PF 6 . Addition of iodide anions to the mobile phase proved a key factor in obtaining lipophilicity indexes which correlated better with the log P G scale for all the solutes investigated. Addition of neutral or strong chaotropic salts (chlorides, hexafluorophosphates), according to the Hofmeister classification, improved the correlations between R M0 and S and between R M0 and ϕ 0 . Experimental log P TLC values were also established on the basis of calibration plots. These values were also correlated with the calculated lipophilicity log P G . Highly significant improvement of this correlation was achieved for mobile phases modified with sodium iodide. The results obtained are discussed in connection with the known physicochemical properties of anions in solution — lyotropic number, Jones-Dole B coefficient, entropy of hydration, surface tension increment, and effective anion polarizability.

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Abstract

Thermodynamic studies are necessary to understand the mechanism of such an interesting phenomenon as spin crossover in complex compounds. A number of reviews have already covered spin crossover in mononuclear complexes, so the suggested review considers in more detail the problems of obtaining thermodynamic data for polynuclear complex compounds of iron (II) with 4-substituted 1,2,4-triazole derivatives. The composition of trinuclear and polynuclear complexes of iron (II) with 1,2,4-triazoles was studied in terms of its effect on C p(T) dependence; magnetochemical and thermodynamic data are also confronted with each other.

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The purpose of this paper was to assess the suitability of thin-layer chromatography (TLC) as a pilot method for high-performance liquid chromatography (HPLC). The new 1,2,4-triazole and thiosemicarbazide derivatives were analyzed by use of reversed-phase (RP)-TLC and RP-HPLC techniques, applying octadecyl silica adsorbents and aqueous-organic mobile phases. Organic modifiers: methanol and acetonitrile were used at appropriate concentrations providing optimal retention factors. For both techniques, retention coefficient k in column chromatography and the retardation factor R F expressing retention in TLC were determined. The experimentally measured parameters were presented in a logarithmic scale as log k and R M, respectively. The constructed relationships between log k and R M allowed determining the possibility of TLC for anticipating HPLC retention behavior.

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The reversed-phase thin layer chromatographic retention behavior of some new derivatives of 1,2,4-triazole and thiosemicarbazide has been determined. Linear relationships were established between the retention ( R M ) of each solute and the volume fraction of organic modifier (methanol or acetonitrile) in organic-aqueous mobile phases. This enabled determination of chromatographic lipophilicity data — R MW values by extrapolation, ϕ 0 by interpolation for each organic modifier, and S denoting the slope of the linear dependences. Moderate correlation was established between chromatographic lipophilicity and log P G calculated by use of Chem Plus software. Experimental lipophilicity log P TLC was also determined for each solute by the use of a special calibration plot prepared by use of selected sulfonamide standards for the two mobile phase systems used in this study. The effect of different mobile-phase modifiers on experimentally obtained lipophilicity was studied and compared.

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As it was shown in earlier experiments, magnetic field can influence various processes taking part in nature. One of them might be the permeation of chemical compounds across biological membranes. An excellent tool for investigations on that subject is chromatography. Basing on retention measurements performed using reversed-phase thin-layer chromatography (RP-TLC) and micellar liquid chromatography—thin-layer chromatography (MLC—TLC), descriptors of lipophilicity were calculated for the group of 1,2,4-triazole derivatives. The experiments were performed in moderate (≈0.4 T) magnetic field and simultaneously outside it. The analysis of the obtained data showed that the presence of an external static magnetic field can alternate the obtained descriptor values which allows to assume that the ability of passive permeation of the investigated substances across cellular membrane also changes. The intensity of changes depends on the structure of the chromatographed substance and the lipophilicity measurement method.

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