Surface and Aggregation Behavior of Aqueous Solutions of Ru(II) Metallosurfactants:  4. Effect of Chain Number and Orientation on the Aggregation of [Ru(bipy)₂(bipy‘)]Cl₂ Complexes

Abstract

The structure of aggregates formed by eight surfactant [Ru(bipy)2(p,p'-dialkyl-2,2'-bipy)]Cl2 complexes-which we express as Ru(p)(q)Cn, where n (=12 or 19) is the alkyl chain length, p (=4 or 5) refers to the substitution position on the bipyridine ligand, and q (=1 or 2) is the number of substituted alkyl chains-in aqueous solutions has been examined using small-angle neutron scattering for a range of concentrations close to the critical micelle concentration and for several combinations of n, p, and q. A number of general results emerge. The double-chain surfactants possess a smaller headgroup charge but a larger aggregate size than their single-chain analogues. Over the concentration range studied, the micelles of the single-chain surfactants grow as the concentration is increased, whereas for the double-chain systems, the aggregate size remains unchanged. For both single- and double-chain surfactants, an increase in alkyl chain length is accompanied by an expected increase in aggregate size and an increase in average headgroup charge. The aggregates formed in solutions of resolved double-chain complexes are larger than those found in solutions of racemic mixtures. The Ru(4)(1)C12 and Ru(5)(1)C12 systems form aggregates with high water content. Variation of the substitution position for the single-chain surfactants produces dramatic changes in the structure of the micelles. The aggregates formed in solutions of Ru(4)(1)C19 and Ru(5)(1)C19 display particularly different structures. The Ru(4)(1)C19 system forms essentially spherical aggregates. In contrast, in the Ru(5)(1)C19 system, wormlike aggregates are formed in which the rigid rodlike sections appear to undergo a transition from a noninterdigitated to an interdigitated structure as the concentration is increased. For double-chain surfactants, the aggregation number for p = 4 surfactants is considerably larger than that for p = 5 surfactants.

Self‐Assembly of a Triangle‐Shaped, Hexaplatinum‐Incorporated, Supramolecular Amphiphile in Solution and at Interfaces

“…Evaporation of an amphiphilic porphyrin from acetone yields globular mesoscopic aggregates 7a. Ru II ‐based metallosurfactants in doped mesoporous silicates form surface aggregates at the air–water interface,7b whereas wormlike aggregates were found in aqueous solutions 7c. A ruthenium‐based amphiphilic macrocycle with four voluminous hydrophobic groups has been reported to form inverted aggregates in apolar solvents 7d.…”

Amphiphilic and Magnetic Properties of a New Class of Cluster‐Bearing [L2Cu4(μ4‐O)(μ2‐carboxylato)4] Soft Materials

“…Recent advances in the field of metal-containing soft materials point to successful applications toward molecular electronics, [1][2][3][4] responsive thin films, [5,6] and hierarchical materials. [7] Other emerging applications focus on metallopolymers [8][9][10] and dendrimers [11,12] or metallosurfactants [13][14][15] and mesogens [16][17][18][19] taking advantage of the geometric, redox, and magnetic properties of transition-metal centers to build up organized supramolecular architectures based on organic scaffolds. The inclusion of three-dimensional metal clusters Abstract: A general approach toward amphiphilic systems bearing multimetallic clusters and their ability to form Langmuir-Blodgett films is presented.…”

Interactions between Catalysts and Amphiphilic Structures and their Implications for a Protocell Model

“…To increase the association between the bilayers and the ruthenium complex catalyst, [14,15] new ligands were synthesized that possessed an aliphatic hydrocarbon side chain (C 10 H 21 The interactions of the catalysts (Figure 1 B/I-IV) with oily precursor droplets were identical or very similar to those described for decanoic acid/decanoate bilayers. More specifically, the aqueous ruthenium and the ruthenium-8-oxoguanine compounds coated the surface of the oily droplets.…”