Smart Hydrogen Atoms in Heterocyclic Cations of 1,2,4-Triazolium-Type Poly(ionic liquid)s

Abstract

Metrics & MoreArticle Recommendations * sı Supporting Information CONSPECTUS: Discovering and constructing molecular functionality platforms for materials chemistry innovation has been a persistent target in the fields of chemistry, materials, and engineering. Around this task, basic scientific questions can be asked, novel functional materials can be synthesized, and efficient system functionality can be established. Poly(ionic liquid)s (PILs) have attracted growing interest far beyond polymer science and are now considered an interdisciplinary crossing point between multiple research areas due to their designable chemical structure, intriguing physicochemical properties, and broad and diverse applications. Recently, we discovered that 1,2,4-triazolium-type PILs show enhanced performance profiles, which are due to stronger and more abundant supramolecular interactions ranging from hydrogen bonding to metal coordination, when compared with structurally similar imidazolium counterparts. This phenomenon in our view can be related to the smart hydrogen atoms (SHAs), that is, any proton that binds to the carbon in the Nheterocyclic cations of 1,2,4-triazolium-type PILs. The replacement of one carbon by an electron-withdrawing nitrogen atom in the broadly studied heterocyclic imidazolium ring will further polarize the C−H bond (especially for C5−H) of the resultant 1,2,4-triazolium cation and establish new chemical tools for materials design. For instance, the H-bond-donating strength of the SHA, as well as its Bro̷ nsted acidity, is increased. Furthermore, polycarbene complexes can be readily formed even in the presence of weak or medium bases, which is by contrast rather challenging for imidazolium-type PILs. The combination of SHAs with the intrinsic features of heterocyclic cation-functionalized PILs (e.g., Ncoordination capability and polymeric multibinding effects) enables new phenomena and therefore innovative materials applications.In this Account, recent progress on SHAs is presented. SHA-related applications in several research branches are highlighted together with the corresponding materials design at size scales ranging from nano-to micro-and macroscopic levels. At a nanoscopic level, it is possible to manipulate the interior and outer shapes and surface properties of PIL nanocolloids by adjusting the hydrogen bonds (H-bonds) between SHAs and water. Owing to the interplay of polycarbene structure, N-coordination, and the polymer multidentate binding of 1,2,4-triazolium-type PILs, metal clusters with controllable size at sub-nanometer scale were successfully synthesized and stabilized, which exhibited record-high catalytic performance in H 2 generation via methanolysis of ammonia borane. At the microscopic level, SHAs are found to efficiently catalyze single crystal formation of structurally complex organics. Free protons in situ released from the SHAs serve as organocatalysts to activate formation of C−N bonds at room temperature in a series of imine-linked crystalline porous organics, such as organic cag...

Water Molecule as a Dynamic Cross-Linker for Creating Multifunctional Poly(ionic liquid) Porous Membranes

“…According to the basic theory of heterocyclic chemistry and as judged by electron density and polarization, the 1,2,4-triazole ring features two pyridine-type N atoms and one pyrrole-type N atom, while the imidazole ring possesses one pyridine-like N atom and one pyrrole-type N atom. 37 This additional pyridinetype N atom in the 1,2,4-triazole ring features a σ lone pair in a sp 2 hybridization orbital, acting as an H-bond acceptor site. Additionally, considering the greater electronegativity of N than C, the introduction of an electron-withdrawing N atom into the 1,2,4-triazolium ring causes the C−H in the 1,2,4triazolium cation to become more polarized.…”

The marriage of porous cages and metal clusters for advanced catalysis

“…Apart from the N-based and S-based groups, as an important class of coordination groups, N-heterocyclic carbenes (NHCs) have recently attracted increasing attention for stabilizing metal species. 7 a ,20 NHCs refer to neutral carbon species with two coordinatively unsaturated electrons, and at least one nitrogen next to the carbene donor within the heterocyclic ring structure. The σ-donating and π-accepting interactions allow carbenes to form exceptionally stable metal–carbene bonds to bind a series of metal ions.…”

Facile and Eco-Friendly Approach to Multifunctional Supramolecular Poly(ionic liquid) Nanoporous Membranes Containing Hydrophilic Anions (Br–, MBry–, M = Sn, Pb, Sb, Bi)

“…Poly­(ionic liquid)­s, i.e., polymerized ionic liquids, have recently attracted focused attention in the polymer materials and functional polyelectrolyte membranes communities because they combine some special characteristics of ionic liquids with the common properties of polymers, i.e., processability, mechanical stability, etc. − Herein, we explored, for the first time, the use of PILs coupling hydrophilic Br anion as precursors for making SPPMs by the rational chemical design of polycations of PILs, and discovered that SPPMs can be manufactured in water from homo-PILs that contain coordinational, hydrophilic counteranions (MBr y – , M = Sn, Pb, Sb, Bi) by coordination of Br – with metal bromides. This had long been thought to be “impossible” for PPMs because PILs interact with water molecules primarily through the anions in aqueous media, and the highly hydrophilic nature of these anions always generates water solubility of PILs.…”