Supramolecular assemblies of cucurbit[n]urils and 4-aminopyridine controlled by cucurbit[n]uril size(n=5,6,7 and 8)

The binding interactions between 4-aminopyridine(4-AP) and a series of cucurbit[n]urils(Q[5], Q[6],TMe Q[6], Q[7], Q[8]) have been studied using1H NMR spectroscopy, UV–vis absorption spectroscopy,isothermal titration calorimetry(ITC) and X-ray crystallography. The data indicates that the Q[5]@4-AP complex exhibits exo binding, which is not observed in the other four host-guest complexes. Furthermore,X-ray crystallography clearly reveals how the Q[n]s bind with 4-AP to form complexes, for example Q[5]forms an outer-surface complex, whilst Q[6], TMe Q[6] and Q[7] formed 1:1 host and guest type complexes, and Q[8] formed a stable 1:2 ternary complex due to its large cavity, which can accommodate two 4-AP molecules.

Large-Scale Synthesis of the Stable Co-Free Layered Oxide Cathode by the Synergetic Contribution of Multielement Chemical Substitution for Practical Sodium-Ion Battery

The O3-type layered oxide cathodes for sodium-ion batteries(SIBs)are considered as one of the most promising systems to fully meet the requirement for future practical application.However,fatal issues in several respects such as poor air stability,irreversible complex multiphase evolution,inferior cycling lifespan,and poor industrial feasibility are restricting their commercialization development.Here,a stable Co-free O3-type NaNi_(0.4)Cu_(0.05)Mg_(0.05)Mn_(0.4)Ti_(0.1O2) cathode material with large-scale production could solve these problems for practical SIBs.Owing to the synergetic contribution of the multielement chemical substitution strategy,this novel cathode not only shows excellent air stability and thermal stability as well as a simple phase-transition process but also delivers outstanding battery performance in half-cell and full-cell systems.Meanwhile,various advanced characterization techniques are utilized to accurately decipher the crystalline formation process,atomic arrangement,structural evolution,and inherent effect mechanisms.Surprisingly,apart from restraining the unfavorable multiphase transformation and enhancing air stability,the accurate multielement chemical substitution engineering also shows a pinning effect to alleviate the lattice strains for the high structural reversibility and enlarges the interlayer spacing reasonably to enhance Na^(+)diffusion,resulting in excellent comprehensive performance.Overall,this study explores the fundamental scientific understandings of multielement chemical substitution strategy and opens up a new field for increasing the practicality to commercialization.