| Pillar[n]arenes?pillararenes,or pillarenes for short?,synthesized and reported for the first time in 2008,has already become the new generation of supramolecular macrocycles.The pillarenes play an important role in the architecture of supramolecular polymers owing to the their host-guest properties.Inspired by the well-investigated structure and synthetic methods of pillarene,we designed and synthesized a new type of pillarene derivative—methylated leaning tower[6]arene?MeLT6?,which could be monofunctionalized or bifunctionalized successively,making it possible to act as a building block for supramolecular polymers.In comparison with the traditional pillarene,the cavity size of methylated leaning tower[6]arene is similar to the traditional pillar[6]arene,and the monofunctionalized or bifunctionalizd properties is similar to the conventional pillar[5]arene.Meanwhile,the novel macrocycle can be synthesized by utilizing the 1,4-dimethoxybenzene compound conveniently?the traditional pillar[6]arene can be only formed by 1,4-diethoxybenzene?.It was also found that the suitable cavity of methylated leaning tower[6]arene could interact with positively-charged guest molecules?pyridine quaternary ammonium salts and tetramethyl quaternary ammonium salts?at a ratio of 1:1.In this paper,the leaning tower[6]arene was either functionalized by removing one of the eight methoxyl groups and forming phenolic hydroxyl groups under the treatment of traditional boron tribromide,or oxidizing one of the four 1,4-dimethoxybenzene units quantitatively by cerium ammonium nitrate to form paraquinones,followed by two phenolic hydroxyl groups after reduction.These two kinds of methylated leaning tower[6]arene with phenolic hydroxyl groups possessed good reactivity,which fully verified that methylated leaning tower[6]arene could be easily modified by other functional groups.On the basis of the favorable features,we prepared two derivatives of leaning tower[6]arene,namely tripyridine-monomodified leaning tower[6]arene and dipyridine-modified leaning tower[6]arene.Considering the metal-coordinating ligands and macrocyclic cavities,the two functionalized leaning tower[6]arenes were capable of serving as appropriate building blocks in the fabrication of supramolecular polymers.The main contents of this paper are as follows:In the first part,we quantitatively removed a methoxyl group from the methylated leaning tower[6]arene,and then synthesized the tripyridine-monomodified leaning tower[6]arene?TPy-MeLT6?through the subsequent multi-step"click"reaction and grown single crystal in the state of aggregation.Based on the metal-coordination of tripyridine and the host-guest interaction between the macrocyclic cavity and guest moieties,a triple-stimuli-responsive fluorescent supramolecular polymer network,has been constructed by assembling with a TPE tetratopic guest linker possessing four pyridinium arms?TPE-TPy+·4PF6-?and zinc trifluoromethanesulfonate?Zn?OTf?2?,equipped with the ability of depolymerizing upon competitive binding,addition of acids and temperature changes.In the second part,quinoid leaning tower[6]arene?Q-MeLT6?was obtained after the treatment of cerium ammonium nitrate,and one of the quinoid leaning tower[6]arene with high yield was isolated,and the single crystal was also grown successfully.After reduction,Q-MeLT6 was modified by pyridine-4-boronic acid via Suzuki-Miyaura coupling reaction,giving the dipyridine leaning tower[6]arene?DPy-MeLT6?.Coordinating polymerization occurred rapidly when DPy-MeLT6 was used as a ligand to connect with copper ions.With the saturation of coordination with Cu2+,the polymer gradually turned into a morphology of ordered crystal structure from irregular polymer networks.In its crystal structure,the coordination polymer possessed the maximum adsorption capacity as 62 wt%in 1 hour towards iodine vapor.Therefore,we envisioned that this kind of coordination polymer had great potential in the field of gas and pollutant adsorption. |
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