Synthesis, Redox, and Amphiphilic Properties of Responsive Salycilaldimine-Copper(II) Soft Materials

Abstract

Hydrolysis of the asymmetric pyridine- and phenol-containing ligand HL (1) (2-hydroxy-4-6-di- tert-butylbenzyl-2-pyridylmethyl)imine) led to the use of bis-(3,5-di -tert-butyl-2-phenolato-benzaldehyde)copper(II), [Cu (II)(L (SAL)) 2] ( 1) as a precursor for bis-(2,4-di- tert-butyl-6-octadecyliminomethyl-phenolato)copper(II), [Cu (II)(L (2)) 2] ( 3), bis-(2,4-di- tert-butyl-6-octadecyl aminomethyl-phenolato)copper(II), [Cu (II)(L (2A)) 2] ( 3'), and bis-(2,4-di- tert-butyl-6-[(3,4,5-tris-dodecyloxy-phenylimino)-methyl]-phenolato)copper(II), [Cu (II)(L (3)) 2] ( 4). These complexes exhibit hydrophilic copper-containing head groups, hydrophobic alkyl and alkoxo tails, and present potential as precursors for redox-responsive Langmuir-Blodgett films. All systems were characterized by means of elemental, spectrometric, spectroscopic, and electrochemical techniques, and their amphiphilic properties were probed by means of compression isotherms and Brewster angle microscopy. Good redox activity was observed for 3 with two phenoxyl radical processes between 0.5 and 0.8 V vs Fc (+)/Fc, but this complex lacks amphiphilic behavior. To attain good balance between redox response and amphiphilicity, increased core flexibility in 3' and incorporation of alkoxy chains in 4 were attempted. Film formation with collapse at 14 mN.m (-1) was observed for the alkoxy-derivative but redox-response was seriously compromised. Core flexibility improved Langmuir film formation with a higher formal collapse and showed excellent cyclability of the ligand-based processes.

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

“…However, the A c increase is less noticeable than that of a phenanthroline-based surfactant upon copper insertion, [41] but is significantly smaller than that of a bipyridyl-A C H T U N G T R E N N U N G rhenium(I) surfactant [5b] with the same hydrocarbon chain length. Comparison with another recently published cuproamphiphile, [29] in which the surfactant head group is a tert-butyl-substituted phenolate, also suggests that the pyridine-based systems give higher collapse values and more organized films. Differences in the ligand head groups, the oxidation states of the ions, and their electronic structures explain the significant variation in A c between the 3d cop-A C H T U N G T R E N N U N G per(II) and the 5d rhenium(I) surfactants.…”

“…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.…”

Synthesis of Amphiphilic Azo‐Anion‐Radical Complexes of Chromium(III) and the Development of Ultrathin Redox‐Active Surfaces by the Langmuir–Schaefer Technique

“…The signal owing to the rest of the alkyl-chain protons appeared in the range d = 1.19-3.97 ppm. [17,11] The 1 H NMR spectrum of ligand L d is given in Figure S1 (1 a-1 d) in almost quantitative yield (> 90 %), [5] for which satisfactory elemental analyses were obtained (see the Experimental Section). Electrospray mass spectrometry of the complexes corroborated their formulations as www.chemeurj.org and S4, respectively).…”

“…[12] The former approach has been used with impressive results in the design of responsive thin films. [11,13,14] This fact points to the potential role of discrete metallosurfactant materials (i.e. surfactants containing transition-metal ions) in the emerging field of molecular devices.…”

“…The thicknesses of the films can be controlled at the molecular level upon repeated deposition, thereby leading to optimized optical and electrical properties of the final products. The fabrication of transition-metal complexes that exhibit rich spectraland redox properties on a solid surface can be achieved by the above-mentioned techniques using either surfactant derivatives of the metal complex [11] or mixed monolayers of the metal/complex ion with amphiphilic molecules. [12] The former approach has been used with impressive results in the design of responsive thin films.…”