Photo‐activation of Tolane‐based Synthetic Ion Channel for Transmembrane Chloride Transport

Abstract

While natural channels respond to external stimuli to regulate ion concentration across cell membranes, creating a synthetic version remains challenging. Here, we present a photo‐responsive uncaging technique within an artificial ion channel system, which activates the ion transport process from a transport‐inactive o‐nitrobenzyl‐based caged system. From the comparative ion transport screening, 1 b emerged as the most active transporter. Interestingly, its bis(o‐nitrobenzyl) derivative, i.e., protransporter 1 b′ was inefficient in transporting ions. Detailed transport studies indicated that compound 1 b is an anion selective transporter with a prominent selectivity towards chloride ions by following the antiport mechanism. Compound 1 b′ did not form an ion channel, but after the o‐nitrobenzyl groups were photocleaved, it released 1 b, forming a transmembrane ion channel. The channel exhibited an average diameter of 6.5±0.2 Å and a permeability ratio of . The geometry‐optimization of protransporter 1 b′ indicated significant non‐planarity, corroborating its inefficient self‐assembly. In contrast, the crystal structure of 1 b demonstrates strong self‐assembly via the formation of an intermolecular H‐bond. Geometry optimization studies revealed the plausible self‐assembled channel model and the interactions between the channel and chloride ion.