TY - JOUR

T1 - Thermodynamic Study of Solubilization of Crown-Substituted Magnesium Phthalocyaninate in Aqueous Solutions of Sodium Dodecyl Sulfate

AU - Rusanov, Anatoly

AU - Movchan, Tamara

AU - Plotnikova, E.V.

N1 - Funding Information: The work was carried out within the state order of the Ministry of Science and Higher Education of the Russian Federation (Registration no. NIOKTR АААА-А19-119031490082-6) and supported by the Russian Foundation for Basic Research (project no. 20-03-00641).

PY - 2021/1

Y1 - 2021/1

N2 - Abstract: A spectrophotometric study of the solubilization of crown-substituted magnesium phthalocyaninate (I) has been carried out in an aqueous solution of sodium dodecyl sulfate (II). The experiments have been performed with saturated solutions of I at a thermodynamic equilibrium of a solution with a precipitate of I. The known transition from dimers of I to monomers upon solubilization has been studied in detail. It has been found that monomerization of I begins at concentrations much lower than the critical micelle concentration (CMC) of II, while specific micelles of II are formed with involvement of I dimers at still lower surfactant concentrations. The presence of dimers is also observed when I is dissolved in pure water; the solubility of I has appeared to be 7.38 μM (chemists usually suppose I to be insoluble in water). Extinction coefficients of monomers and dimers of I have been determined in the methodological part of the work. The following thermodynamic characteristics of solubilization have been found on the basis of experimental data: solubilization capacity of micelles, coefficient of solubilizate partition between micelles and an ambient solution, and the standard solubilization affinity of I. The found value of the solubilization capacity as calculated per one molecule of I in a micelle leads to an abnormally large aggregation number (309). One explanation of this fact is the possible development of a bimodal distribution of micelles, at which solubilisate-containing micelles coexist with “empty” micelles; as a result, the average number of solubilizate molecules in a micelle can appear to be smaller than unity.

AB - Abstract: A spectrophotometric study of the solubilization of crown-substituted magnesium phthalocyaninate (I) has been carried out in an aqueous solution of sodium dodecyl sulfate (II). The experiments have been performed with saturated solutions of I at a thermodynamic equilibrium of a solution with a precipitate of I. The known transition from dimers of I to monomers upon solubilization has been studied in detail. It has been found that monomerization of I begins at concentrations much lower than the critical micelle concentration (CMC) of II, while specific micelles of II are formed with involvement of I dimers at still lower surfactant concentrations. The presence of dimers is also observed when I is dissolved in pure water; the solubility of I has appeared to be 7.38 μM (chemists usually suppose I to be insoluble in water). Extinction coefficients of monomers and dimers of I have been determined in the methodological part of the work. The following thermodynamic characteristics of solubilization have been found on the basis of experimental data: solubilization capacity of micelles, coefficient of solubilizate partition between micelles and an ambient solution, and the standard solubilization affinity of I. The found value of the solubilization capacity as calculated per one molecule of I in a micelle leads to an abnormally large aggregation number (309). One explanation of this fact is the possible development of a bimodal distribution of micelles, at which solubilisate-containing micelles coexist with “empty” micelles; as a result, the average number of solubilizate molecules in a micelle can appear to be smaller than unity.

UR - http://www.scopus.com/inward/record.url?scp=85101305950&partnerID=8YFLogxK

UR - https://www.mendeley.com/catalogue/fd0640ac-d641-3304-9c79-9e9b87706e6b/

U2 - 10.1134/S1061933X21010087

DO - 10.1134/S1061933X21010087

M3 - Article

VL - 83

SP - 97

EP - 106

JO - Colloid Journal

JF - Colloid Journal

SN - 1061-933X

IS - 1

ER -