25812-77-5Relevant articles and documents
Br?nsted Basicities and Nucleophilicities of N-Heterocyclic Olefins in Solution: N-Heterocyclic Carbene versus N-Heterocyclic Olefin. Which Is More Basic, and Which Is More Nucleophilic?
Li, Zhen,Ji, Pengju,Cheng, Jin-Pei
, p. 2974 - 2985 (2021)
A Br?nsted basicity scale comprising nine representative N-heterocyclic olefins (NHOs) was established by measuring the equilibrium acidities of their corresponding precursors in DMSO using an ultraviolet-visible spectroscopic method. The basicities (pKaHs) of the investigated NHOs cover a range from 14.7 to 24.1. The basicities of unsaturated NHOs are stronger than those of their N-heterocyclic carbene (NHC) analogues; however, the basicities for the saturated ones are much weaker than those of their NHC analogues, which is largely due to the aromatization effect that intrinsically influences the acidic dissociations of NHC and NHO precursors. The nucleophilicities of four NHOs were measured photometrically by monitoring the kinetics of reactions of these NHOs with common reference electrophiles for quantifying nucleophilic reactivities. In general, the nucleophilicity of the NHOs is much stronger than that of commonly used Lewis bases such as Ph3P or DMAP [4-(dimethylamino)pyridine] but weaker than that of their NHC analogues; however, caution should be taken when generalizing this conclusion to a wide range of electrophiles with distinctively electronic and structural properties.
Anisotropic, Organic Ionic Plastic Crystal Mesophases from Persubstituted Imidazolium Pentacyanocyclopentadienide Salts
Goossens, Karel,Rakers, Lena,Heinrich, Beno?t,Ahumada, Guillermo,Ichikawa, Takahiro,Donnio, Bertrand,Shin, Tae Joo,Bielawski, Christopher W.,Glorius, Frank
, p. 9593 - 9603 (2019/12/24)
We describe the synthesis, supramolecular organization, and thermal characteristics of an unprecedented family of symmetric 1,2,3,4,5-pentaalkylimidazolium ([(Cn)5im]+) salts equipped with halide, nitrate, or pentacyanocyclopentadienide ([Cp(CN)5]-) counterions. Salts containing relatively small anions were obtained as low-melting solids, whereas those with [Cp(CN)5]- anions were found to be ionic liquids even below room temperature. A permethylated derivative, [(C1)5im][Cp(CN)5], proved to be exceptional. Upon heating, the salt self-organized into a new type of organic ionic plastic crystal (OIPC) mesophase, which was termed Mhex and whose anisotropic structure featured hexagonally ordered, rotating anionic stacks positioned within a continuum composed of disordered cations. The structure of the mesophase resembles that of classical columnar liquid-crystalline phases, despite the absence of long, flexible chains. In the Mhex phase, the cations surrounding the anionic columns effectively fulfill the role of "softening" structural constituents, much in the same way as flexible chains. The discovery of the novel mesophase, which displays a two-dimensional, and thus intrinsically anisotropic, lattice resulting from the rotation of entire ionic assemblies around a columnar axis, represents a new paradigm in the field of OIPCs. Relatively high ionic conductivities were measured in the Mhex phase, particularly after doping with the corresponding sodium salt, Na[Cp(CN)5], demonstrating the materials' potential for use in electrochemical applications such as sodium-ion batteries.
Controlled preparation of amphiphilic triblock-copolyether in a metal- and solvent-free approach for tailored structure-directing agents
Balint, Alexander,Papendick, Marius,Clauss, Manuel,Müller, Carsten,Giesselmann, Frank,Naumann, Stefan
supporting information, p. 2220 - 2223 (2018/03/06)
Under mild conditions, PPO-PEO-PPO ("reverse Pluronics") and PBO-PEO-PBO copolyether were generated by way of N-heterocyclic olefin-based organocatalysis. Reverse Pluronics with molar masses > 20 000 g mol-1 could be synthesized with excellent control (DM ≤ 1.03) and were converted into (ordered) mesoporous carbons via organic self-assembly to showcase the need for tailor-made copolymer as structure-directing agent.
