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

Abstract

A general approach toward amphiphilic systems bearing multimetallic clusters and their ability to form Langmuir-Blodgett films is presented. The synthetic strategy to stabilize these clusters involves the use of a ligand (HL) containing an N(2)O-donor set and long octadecanoic chains to obtain the carboxylate-supported [L(2)Cu(4)(mu(4)-O)(mu(2)-OAc)(4)]EtOH (1) and [L(2)Cu(4)(mu(4)-O)(mu(2)-OBz)(4)] (2) in which OAc(-) and OBz(-) represent acetate (1) and benzoate (2) co-ligands. These species were thoroughly characterized and had their structures solved by X-ray crystallography. We observed that the mu-oxo Cu(4) cluster is antiferromagnetically coupled and used broken-symmetry density functional theory (DFT) calculations to describe the main superexchange pathways of the tetracopper core. We also describe the amphiphilic properties of the ligand and the cluster-containing systems by means of area versus pressure isotherms and show that these cluster-bearing species can be transferred onto solid substrates yielding homogeneous Langmuir-Blodgett films, as characterized by atomic force microscopy and contact angle measurements.

Interfacial Behavior and Film Patterning of Redox‐Active Cationic Copper(II)‐Containing Surfactants

“…Overall, the C 16 species start organizing at lower area per molecule values and collapse at slightly lower pressures than their C 18 counterparts, which thus reflects the influence of the chain length. In contrast to 1 and 4, species 2 and 5 display similar A c values of [26][27][28] 2 at collapse, with 5 showing a steeper slope. The reported collapse pressures for 1, 2, 4, and 5 are significantly greater than those observed for other metal-surfactant complexes.…”

“…We have demonstrated the feasibility of Langmuir-Blodgett (LB) films with magnetic copper(II) clusters, [27] the redox-state control and dependence of a collapse mechanism on cobalt(II) films, [28] and the factor that determines the delicate equilibrium between redox activity and amphiphilicity in copper/phenoxyl species. [29] Herein, we present an in-depth investigation of the properties of novel single-tail cationic copper(II)-containing surfactants with the ligands L PyC 18 , L PyC 16 , L PyC 14 , and L PyC 10 , in which Py = pyridine and C n indicates the alkyl chain length.…”

Diastereomerism in tetranuclear copper(II) complexes of a phenol based “end-off” compartmental ligand

“…Inspection of geometrical data in 1a allows to observe a fair trend of shorter Cu\Cu distances associated with a narrower Cu\O(oxo)\Cu angle for the bridged metals. A search in CCDC on structurally characterized complexes with a Cu 4 (O) core with compartmental phenolate ligands bridged by four carboxylate fragments (acetate, benzoate, trifluoroacetato) retrieved thirteen structures and in the majority of these [14][15][16][17] the carboxylates assume an arrangement similar to complex 1a, and only in three cases [17][18][19] was observed a configuration analogous to that of 1. As a matter of completeness, one structure with benzoate bridging ligands shows an additional diastereomer, with three carboxylates pointing towards the same copper ion, thus having a distorted octahedral coordination sphere.…”

On the Effect of Coordination and Protonation Preferences in the Amphiphilic Behavior of Metallosurfactants with Asymmetric Headgroups

“…Nevertheless, the small body of work available on the isolation and air/water interface behavior of metallosurfactant precursors still poses a major drawback to the approach. [13,14] At the forefront of this area, our group has focused on synthetic, modeling, and surface protocols involving the incorporation of magnetic µ-oxo-Cu 4 clusters in LangmuirBlodgett films, [15,16] the observation of distinctive collapse mechanisms on cobalt(II) films, [17] and the design of redoxactive copper-containing amphiphiles. [18,19] In a series of studies with iron(III), [20] cobalt(II/III), [21] and gallium-(III) [22] we have demonstrated that structural and electronic effects can determine the preferential geometry of redoxactive asymmetric NNЈO ligands in [ML 2 ] metallosurfactants.…”