Water‐Stable, Eight‐electron Acceptor Drives Anion⋅⋅⋅Water Assisted Tunable Ionic Self‐Assembly and Proton Conduction

• Published in: Chemistry : a European journal 2024-09, Vol.30 (53), p.e202401334-n/a
• Main Authors: Shukla, Jyoti, Bera, Siba P., Ajayakumar, M. R., Konar, Sanjit, Mukhopadhyay, Pritam
• Format: Article
• Language: English
• Subjects: Anion-water chain; Anions; Aqueous solutions; Chemical bonds; Conduction; Conductivity; Electrons; Ionic assembly; Lipophilic; Multi-electron acceptors; Proton conduction; Proton conductivity; Scaffolds; Self-assembly; Water chemistry
• ISSN: 0947-6539; 1521-3765; 1521-3765
• DOI: 10.1002/chem.202401334

Organic π‐scaffolds are being envisaged for new‐age electron‐ and ion‐responsive materials that can accumulate electrons as well as transport proton. However, such systems are extremely rare as electron‐deficient scaffolds are unstable in aqueous solution. Here we detail the synthesis of a water‐stable core‐naphthalenediimide‐nitrobenzyl‐viologen based tetra‐cation, which accumulates up to eight‐electrons within an exceptionally narrow potential window of +0.05 V and −1.12 V. The supramolecular interactions and the ensuing ionic framework are tunable based on the three anions, e. g., Cl−, Br− and PF6−, that are investigated in this work. The ionic framework is formed and supported by a range of H‐bonds, in which, the nitro benzyl groups act as pillars connecting the 1D water‐tapes and the halide anions. The water molecules are hydrogen‐bonded with the halide anions and bestow a facile pathway for the proton conduction, with proton conductivity up to 3.19×10−3 S cm−1. In contrast, the ionic assembly formed by the lipophilic PF6− anions do not host the water tapes and consequently the proton conductivity is found to be four orders of magnitude lower. This is a unique example, whereby proton conductivity is realized and is tunable within a highly electron‐deficient, eight‐electron acceptor, water‐stable ionic supramolecular system. A highly electron‐deficient, water‐stable, eight‐electron acceptor scaffold has been used as a platform to realize proton conduction through ionic self‐assembly. In this unique self‐assembled material, 1D water tapes are revealed, that undergo hydrogen‐bonding with halide anions, thereby generating a pathway for anion‐assisted, tunable proton conduction.