New Surfactant Phosphine Ligands and Platinum(II) Metallosurfactants. Influence of Metal Coordination on the Critical Micelle Concentration and Aggregation Properties

Abstract

We have prepared the first platinum(II) metallosurfactants from a new family of linear surfactant phosphines Ph(2)P(CH(2))(n)SO(3)Na {1 (n = 2), 2 (n = 6), and 3 (n = 10)}, which were synthesized by reaction between the halosulfonates X(CH(2))(n)SO(3)Na and sodium diphenylphosphide. The metallosurfactants cis-[PtCl(2)L(2)] (L = 1-3) were obtained after reaction between the phosphines and PtCl(2) in dimethylsulfoxide. All compounds were fully characterized by the usual methods {NMR ((1)H, (13)C, (31)P, (195)Pt), IR, MS-ESI and HRMS}. By exploring the surfactant properties of phosphines 1-3 and their respective platinum metallosurfactants cis-[PtCl(2)L(2)] (L = 1-3) through surface tension measurements, dynamic light scattering spectroscopy, and cryo-TEM microscopy, we were able to analyze the influence of the metal coordination on the critical micelle concentration (cmc) and the aggregation properties. The cmc values of platinum metallosurfactants were considerably lower than those obtained for the free phosphines 1-3. This behavior could be understood by an analogy between the structure of cis-[PtCl(2)L(2)] complexes and bolaform surfactants. The calculated values of area per molecule also showed different tendencies between 1-3 and cis-[PtCl(2)L(2)] complexes, which could be explained on the basis of the possible conformations of these compounds in the air-water interface. The study of aggregates by dynamic light scattering spectroscopy and cryo-TEM microscopy showed the formation of spherical disperse medium size vesicles in all cases. However, substantial differences were observed between the three free phosphines (the population of micellar aggregates increased with long chain length) and also between phosphines and their respective metallosurfactants.

Supramolecular Arrangement of Molybdenum Carbonyl Metallosurfactants with CO-Releasing Properties

“…Molybdenum pentacarbonyl complexes 4-6 {[Mo(CO) 5 L] (L = 1, 2, 3)} were prepared from Mo(CO) 6 using methods similar to those reported for the related ionic complexes [M(CO) 5 (TPPTS)] (TPPTS = sodium triphenylphosphine trisulfonate) 22 with some modifications in the experimental procedure (Scheme 4). Thus, complexes [Mo(CO) 5 L] can be synthesized by direct reaction with Mo(CO) 6 , or by a substitution reaction with a [Mo(CO) 5 L'] complex that contains a labile L' ligand.…”

“…Thus, complexes [Mo(CO) 5 L] can be synthesized by direct reaction with Mo(CO) 6 , or by a substitution reaction with a [Mo(CO) 5 L'] complex that contains a labile L' ligand. We found that the direct reaction between Mo(CO) 6 and ligands 1-3 in a methanol/THF medium allows obtaining the complexes (4-6) using a convenient procedure and, in addition, it leads to pure products.…”

“…This procedure is very useful to obtain small quantities (≈ 100 mg) of pure complexes 4-6, but it has the problem that large quantities of Mo(CO) 6 are necessary to prepare the complexes on a larger scale (≈ 1.0 g ). 24 and [Mo(CO) 5 (TPPTS)]. 22 The 31 P NMR spectra display a singlet around 27 ppm for the three complexes, showing the normal shift of this signal after coordination to the {Mo(CO) 5 } fragment with respect to the position of free ligands 1-3 (≈ -16 ppm).…”

“…Hence, an excellent example of an alternative design for metallosurfactants is found in metal complexes of functionalized phosphines, in which the phosphine contains a hydrophobic group and a polar group, such as sulphonate. 2,4,5 In this approach, the polar headgroup and the hydrophobic group are located in the molecular structure of the ligand, and consequently, the ligand can act as a surfactant independently of whether it is free or linked to a metal atom. These former groups of ligands (surfactant phosphines) have been relevant in organometallic chemistry, as one important property of surfactants is the selfaggregation and accumulation at the interfaces; properties that have incentivized the study of metallosurfactants in catalytic reactions.…”

Advancing the Pharmaceutical Potential of Bioinorganic Hybrid Lipid‐Based Assemblies

“…Recently, Barnadas‐Rodríguez and co‐workers developed new metallosurfactants with alternative designs 54, 55, 63. Usually, the metal atom form the polar headgroup of the metallosurfactants (Figure 3a), while, in this design, metallic fragments are embedded in the hydrophobic end of the surfactants (Figure 3c).…”