Interfacial Activity of Metal β-Diketonato Complexes: In Situ Generation of Amphiphiles by Water Coordination

Abstract

Symmetric transition metal complexes of 2,4-pentanedione (acetyl acetone) are interfacially active: Spinning drop tensiometry reveals lowering of the interfacial tension at the water-organic interface, most pronounced for [Cr(acac)(3)], [Fe(acac)(3)], [Zr(acac)(4)], and [Hf(acac)(4)]. The interfacial activity is explained by the in situ generation of amphiphilic species. Based on tensiometry and (1)H and diffusion-ordered NMR spectroscopy (DOSY NMR), hydrogen bonding of the organically dissolved complexes with water, in some cases in combination with inner-sphere hydrolytic coordination, is identified as the primary origin of this amphiphilicity. The complexes are a rare example of symmetric molecules that turn amphiphilic only upon interfacial interaction with water.

Precursor directed synthesis – “molecular” mechanisms in the Soft Chemistry approaches and their use for template-free synthesis of metal, metal oxide and metal chalcogenide nanoparticles and nanostructures

“…29,41 It can be said in a simplied manner that the ligands act as surfactants in stabilization of the particles and a quantitative evaluation of this role has been reported. 42 The particles are thus both individual molecular entities and also colloid particles stabilized in solution by interaction between the ligands and the solvent by the forces typical for colloid systems, which led to a proposal to denote them as Micelles Templated by Self-Assembly of Ligands (MTSALs). 39 The non-hydrolytic (including solvothermal) processes 38,[44][45][46][47] are in their nature quite analogous to the hydrolytic ones, but at higher temperatures they offer particles that are much more completely crystalline and also the surface ligand-containing layer which is much thinner and less chemically reactive.…”

Surface Patterning with Colloidal Monolayers

“…Parts of this results were published in the articles "Platinum Nanoparticles from Size adjusted functional colloidal particles generated by a seeded emulsion polymerization process" [181] and "Interfacial activity of uncharged, highly symmetric metal β-diketonato complexes -in situ generation of amphiphiles by water coordination". [182] …”

A molecular “screw-clamp”: accelerating click reactions in miniemulsions

“…Previously, aliphatic carboxylic acids were deprotonated in the heterophase to generate ionic surfactants 20,21 while metallosurfactants and transition metal acetyl acetonates have also been produced in situ. 22,23 The generation of a surfactant in situ can have advantages such as faster stabilization of the (mini)emulsion and less secondary nucleation processes. 24 Here, we used the interfacial ''screw clamp'' for mediating a click reaction in a direct miniemulsion between dodecyl propiolate dispersed in styrene as the organic phase and N-e-azido-L-lysine hydrochloride dissolved in the aqueous phase.…”

“…Previously, aliphatic carboxylic acids were deprotonated in the heterophase to generate ionic surfactants 20,21 while metallosurfactants and transition metal acetyl acetonates have also been produced in situ. 22,23 The generation of a surfactant…”