Orthogonal Polymeric Architecture And Dynamic Pseudo[1]rotaxane Based On Functionalized Pillar[5]arene

In the past few decades,molecular devices constructed by functionalized macrocycle molecules through intermolecular or intramolecular binding have been extensively investigated.Pillar[5]arenas,a new class of macrocycles for supramolecular chemistry,has proved to be excellent hosts for alkyl chain derivatives,viologen cations,(bis)imidazolium cations,ammonium cations and neutral bis(imidazole)derivatives,neutral guest.In the last five years since its first discovery,it has been widely applied in the field of molecule recognition,rotaxanes,supramolecular polymers,molecular springs,artificial transmembrane channels,vesicles,and MOFs(metal-organic frameworks).Although the intensity of the host-guest interactions,hydrogen bonding et al.are weak,under the cooperative effect of several orthogonal interactions,small molecules could assemble into polymeric structures and more stable architectures.This dissertation focus on the synthesis and applications of pillar[5]arene derivatives and consists of four parts of research work:Part 1,ureidopyrimidinone functionalized pillar[5]arene(2-UPyP5)was synthesized and employed to complex with a bisparaquat derivative(G7)to form supramolecular polymers at relatively high concentration(150 mM).The complexation of 2-UPyP5 with bisparaquat derivative was studied by 1H NMR titration experiment and ESI-MS,and the association constant was estimated by fluorescent titration experiment on model compounds.Although the binding between 2-UPyP5 and G7 are weak interactions,various concentration 1H NMR,2D NOESY NMR,DOSY,viscosity measurements and cyclic voltammetry confirmed the formation of the supramolecular polymer at high concentration by two orthogonal interactions:quadruple hydrogen bonding and host-guest interactions.Part 2,we reported the preparation of an unconventional pseudo[1]rotaxane 3-lconfl,which could be isolated from its non-inclusion analogue 3-lu temporarily and exhibited spontaneous but slow isomerization in polar solvent.HR-ESI-MS,various concentration 1H NMR measurements and 2D ROESY NMR proved the intramolecular self-inclusion structure of 3-loonfl.Different from previous pseudo[1]rotaxanes,it could be seen from the NMR spectra directly that 3-lu transform into 3-1confl and another threaded form 3-lconf2 even in high polar solvent,and vice versa.The difference between 3-lconfl and 3-1conf2 is in the position of the binding site,the formation of 3-lconfl was induced by H-bond of amide group and urea group,while 3-1,onf2 is stabilized mainly by H-bond of amide group and the steric hindrance of N-Boc moiety.The addition of fluoride ion could accelerate the transformation from 3-loonfl to 3-lconf2.The reason that self-inclusion structure 3-lconfl and 3-1conf2 remain stable in polar solvent was due to two factors:(1)Urea moiety.Lengthening the distance between the urea moiety and the P5 cavity or eliminating the urea moiety will decrease its stability in polar solvent.This assumption was supported by the experimental evidence:total dethreading of 3-2 happened in 50 days and penetration structure of 3-6 was destroyed in DMSO.(2)Stopper size.Replacing the N-Boc stopper by some small moieties such as amino or acetyl group resulted in the conventional solvent dependent pseudo[1]rotaxane 3-3 and 3-4,which would not form penetrated structure in polar solvent.Replacing the N-Boc stopper with bulky 3,5-di-tert-butylbezene moiety result in mechanically interlocked[1]rotaxane 3-5.From these experimental facts we reach a conclusion that the threaded form and open form of the pseudo[1]rotaxane always exists in equilibrium,if the stopper is as small as amino or acetyl group,the axle threads or dethreads smoothly without barriers,when in polar solvent d6-DMSO,the pseudo[1]rotaxane will exist mainly in the open form.For our system 3-1oonfl/3-1conf2/3-lu,the size of tert-butoxy carbonyl moiety(diameter-2.9 A)makes the axle possible but laborious to thread or dethread the P5 cavity(internal cavity diameter 4.7 A),once the axle is included,it will be trapped in the cavity under the cooperative effect of the H-bonding,host-guest interactions and the steric effect from the bulky N-Boc moiety.Even in polar solvent,the competitive solvent molecules were still unable to defeat this multiple cooperative effect,thus the self-inclusion form 3-1conf1 is more stable than usual pseudo[1]rotaxane,and that may be the reason why it could be separated by chromatography and observed in polar solvent.Part 3,two urea-modified pillar[5]arene derivatives was synthesized and utilized in the construction of polymers with higher aggregation size based on the dual recognition system,in which the P5 cavities included the alkyl chains and the urea moieties capture the anions.This system is the continuous work of the orthogonal assembly of supramolecular polymer.The first compound 4-1 is a ditopic host with two urea modified pillar[5]arenes covalently attached to a beneze moiety,it forms complexes with ditopic guest G9,G10 and Gll with several possible binding modes.The second compound 3-3 is a mono-functionalized pillararene derivative with both urea and amino moieties on the side chain,3-3 was designed to polymerize when triggered by acids,and the ion pair recognition would enhance the binding between the molecules.However,the experimental results showed that the 1H NMR spectra of 3-3 was concerntration independent,and the decrease of the diffusion coefficient was not that obvious,no evidence was found for the formation of higher molecular weight species.All these information lead to the conclusion that didn't 3-3 tend to form stable cyclic oligomer or monomer rather than polymeric structure.In summary,this dissertation has studied the intermolecular and intramolecular self-assemble behavior of functionalized pillar[5]arene molecules in depth,and paved a way for succeeding works on the controllable tuning of the molecular device.