Molecular Barrel by a Hooping Strategy: Synthesis, Structure, and Selective CO2 Adsorption Facilitated by Lone Pair−π Interactions
datasetposted on 04.01.2017, 00:00 by Qi-Qiang Wang, Na Luo, Xu-Dong Wang, Yu-Fei Ao, Yi-Fan Chen, Jun-Min Liu, Cheng-Yong Su, De-Xian Wang, Mei-Xiang Wang
A sophisticated molecular barrel 5 was efficiently constructed by hooping a 63-membered loop around a D3h-symmetric, shape-persistent bis(tetraoxacalixarenetriazine) core. The hooping strategy involved 3-fold ring-closing metathesis (RCM) reactions of six branched olefin arms which were preanchored on the inner core. Through hooping, the loop tightens the cage structure and significantly enhances its stability toward nucleophilic decomposition. The X-ray crystal structure showed the molecular barrel bears three enclosed fan-shaped cavities as divided by the triazine rings and each of the cavities can hold a solvent CHCl3 or CH2Cl2 molecule. With the intrinsic porosity, the amorphous solids of 5 exhibit considerable CO2 uptake with an exceptionally large isosteric enthalpy. Lone pair (lp)−π interactions between the electron-deficient triazine rings and CO2 could contribute to the strong adsorption as supported by IR studies and DFT modeling.
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electron-deficient triazine ringshooping strategyCHCl 3cage structureisosteric enthalpyD 3 hcavityHooping StrategycoreCO 2CH 2 Cl 2 moleculeIR studiesCO 2 uptakeDFT modelingSelective CO 2 Adsorption Facilitatedbarrel 5X-ray crystal structurering-closing metathesisfan-shaped cavities5 exhibitMolecular BarrelRCMtriazine ringsnucleophilic decompositionLone pairolefin arms63- membered loop