Metal Ion Mediation of Interfacial Chiral Supramolecular Formation of Amphiphilic Schiff Bases Studied by In Situ Second Harmonic Generation

Abstract

The coordination effects between chiral Schiff bases and metal ions can provide an effective strategy for fabricating chiral supramolecular self-assemblies. We studied the supramolecular self-assembly of the amphiphilic Schiff base enantiomer, 2-hydroxy-1-naphthylmethylamino-N,N′-bis­(octadecyl)-l/d-glutamic diamide (l/dGJ), at the air/water interfaces by using in situ second harmonic generation linear dichroism (SHG-LD) technique combined with UV–vis spectroscopy and atom force microscopy. lGJ and dGJ monolayers can form mirror-image structures of each other at different interfaces, which can be mediated by metal ions. When Mg2+ and Zn2+ ions were added into the subphases, the l/dGJ monolayers self-assembled into a nanofiber-like structure and showed significant chirality similar to that at the pure water interface. However, when Cu2+ ions were added into the subphase, the chirality of the l/dGJ monolayer was destroyed because of the Cu2+ coordination effect. The degree of the chirality excess (DCE) value decreased with the increment of the concentration of Cu2+ in the subphase. Furthermore, when the surface pressure increased, the DCE value of Cu2+–l/dGJ complexes increased gradually, which indicated that the Cu2+–l/dGJ complex aggregated into a chiral supramolecular structure through lateral molecular packing.

Hypervalent Iodine(III) Mediated Halogen Bonded Supramolecular Chiral System with Cholesteryl Naphthalimides

“…In particular, it has been used extensively in fields such as crystal engineering, supramolecular chemistry, [14] drug design [15][16] and biomolecular engineering. [17] Halogen bonding has become a very effective tool in supramolecular chemistry for the synthesis of new functional materials. Among the various type of halogen bonds, hypervalent iodine(III) [18][19] compounds have been widely studied and utilized as an important halogen bond donor due to their high electron deficiencies and strong binding ability.…”

Studies on the Surface Adsorption of Binary Molten Salts

“…Their analysis showed that the interfacial water layer adopted the most ordered arrangement when the interfacial potential of the adsorbed layer reached saturation which was not at the adsorption-saturated surfactant concentration. Zhang et al 21 investigated the coordination effects between chiral Schiff bases and metal ions by SFG and found that the chirality will change with the increase of metal ions. Levin et al 22 proposed a model with one adjustable parameter to simulate experimental surface tension data for aqueous solutions of NaF, NaCl, and NaBr.…”

“…Due to advances in experimental techniques such as small angle neutron scattering (SANS) − and sum frequency generation vibrational spectroscopy (SFG), − as well as the development of adsorption models, − the surface adsorption of liquid has received great attention and has become a very active field. For instance, Thomas et al , demonstrated SANS limitations in the use of surface tension and the Gibbs equation to determine surface excesses of surfactants.…”

2,6-Bis((benzoyl-R)amino)pyridine (R = H, 4-Me, and 4-NMe2) Derivatives for the Removal of Cu(II), Ni(II), Co(II), and Zn(II) Ions from Aqueous Solutions in Classic Solvent Extraction and a Membrane Extraction

“…Schiff bases are a nitrogen analogue of an aldehyde or ketone in which the carbonyl group (C=O) is replaced by an imine (C=N) [3]. Imines have very good donor properties and can form chemically stable complex compounds with various metals [4][5][6] including transient metal ions [1,7], which makes them useful and widely used in coordination chemistry as organic ligands [8,9]. Many Schiff bases have been successfully used in separation processes for the recovery of metal ions (e.g., N,N -bis(salicylidene)ethylenediamine (Salen) was applied for the removal of copper(II) ions by solvent extraction [10]) and also for the recovery of copper(II), nickel(II), and zinc(II) ions by liquid-liquid extraction and by using polymer inclusion membrane sorption/desorption and transport across the membrane [11].…”

“…Schiff bases were also applied in polymer membranes for the recovery of metal ions (e.g., Mashhadizadeh and Sheikhshoaie used a bis [5-((4-nitrophenyl)azo salicylaldehyde as a carrier in polymer inclusion membrane for the removal of mercury(II) ions [18]). Other carrier groups applicable to the removal of metal ions are calixarenes (e.g., Ulewicz and co-authors used a p-tert-butylcalix [4]arene derivative to transport Pb(II) ions across PIMs [19], whereas a calix [4]-crown-6-derivative nest carrier was used to recover Zn(II), Cd(II), and Pb(II) ions by a PIM membrane [20]). However, research on the recovery of different metal ions from aqueous solutions is not based solely on the search for new compounds (extractants and carriers); well-known compounds with relatively simple structures are increasingly being used for this purpose [21,22].…”