Reversible Stimuli‐Responsive Transmembrane Ion Transport Using Phenylhydrazone‐Based Photoswitches

Abstract

Phenylhydrazone‐based synthetic receptors are reported as stimuli‐responsive anion transporters. The X‐ray crystallographic studies confirmed the preorganized anion binding E‐state and closed non‐binding Z‐state. The detailed ion transport mechanistic studies confirmed Cl−/anion exchange as the primary ion transport process. Their light‐stimulated E‐to‐Z isomerization led to a substantial decrease in the ion transport activity across the lipid bilayer membrane. Reversible “OFF” and “ON” activity switching was studied by light and acid stimuli, respectively.

Progress and prospects toward supramolecular bioactive ion transporters

“…Recently, highly selective methods, including stimuli-responsive protransporters, have been developed by several research groups including us to achieve control over the locus of action of the anionophores. 61,79,85,[87][88][89][90][91][92][93][94][95][96][97][98][99][100] Taken together, synthetic ion transport systems undoubtedly possess immense potential to be used as therapeutic agents in curing life-threatening diseases like cystic fibrosis and cancer. This field has grown rapidly, and new systems with improved efficiencies have recently been reported.…”

“…Phenylhydrazones based on pyridine have a highly stabilized excited state due to the formation of six-membered hydrogen bonding. 149 Keeping all these things in mind, we designed the phenylhydrazone-based in carriers 88 as shown in Fig. 29.…”

“…Recently, highly selective methods, including stimuli-responsive protransporters, have been developed by several research groups including us to achieve control over the locus of action of the anionophores. 61,79,85,87–100…”

Stimulus-Controlled Anion Binding and Transport by Synthetic Receptors

“…Subsequently, phenylhydrazone-based derivatives 75a−d were investigated (Figure 35), 233 which function in similar way as the acylhydrazone transporters described above. Chloride can be bound to the E isomer through the hydrazone N−H and adjacent protons, as was observed in a 1 H NMR titration experiment in MeCN-d 3 (K a ranging from 30−160 M −1 ).…”

pH and light dual stimuli-responses of mixed system of 2-hydroxyl-propanediyl-α,ω-bis(dimethyldodecyl ammonium bromide) and trans-ortho-hydroxyl cinnamic acid

“…Most organisms' life processes are reliant on multiple stimuliresponses rather than single ones. For example, the selective transport of molecules and ions across cell membranes, 1,2 the complex folding of nucleic acid and protein 3,4 and the permeability variations of human skin, 5 are all responses to the perception of comprehensive changes of environment. Inspired by these natural processes, scientists turned their attention to the supramolecular self-assembled functional materials with multiple stimuli-responsiveness to cope with more complex and accurate application scenarios in recent years.…”