1,4-双正丙氧基柱[7]芳烃的合成及主客体化学

我们以1,4-二正丙氧基-2,5-双甲氧甲基苯为原料用对甲苯磺酸为催化剂在二氯甲烷中制备了1,4-双正丙氧基柱5]芳烃, 1,4-双正丙氧基柱6]芳烃和1,4-双正丙氧基柱7]芳烃. 我们用氢谱, 碳谱和质谱对它们进行了表征. 它们有不同的氢谱却有相似的碳谱. 对比它们的空腔尺寸, 柱5]的内径大约是4.6 Å, 与葫芦脲6]及α-环糊精类似. 柱6]的内径大约是6.7 Å, 与葫芦脲7]及β-环糊精类似. 柱7]的内径大约是8.7 Å, 与葫芦脲8]及γ-环糊精类似. 我们用正辛基三乙基六氟磷酸铵盐作为模型客体研究了它们之间的主客体络合. 柱5]与之有微弱的络合, 柱6]显示了良好的络合, 而柱7]与之没有络合.

Synthesis of 1,4-Bis(n-propoxy)pillar[7]arene and Its Host-guest Chemistry

Pillarn]arenes,as a new type of macrocyclic hosts,have attracted more and more attention in recent years.Their repeating units are connected by methylene bridges at the para-positions so they have a pillar architecture,which is different from the basket-shaped structure of meta-bridged calixarenes.Herein,1,4-Bis(n-propoxy)pillar5]arene(P5),1,4-bis(n-propoxy)pillar6]arene(P6) and 1,4-bis(n-propoxy)pillar7]arene(P7) were synthesized from the condensation of 1,4-di(n-propoxy)-2,5-bis(methoxymethyl)benzene using p-toluenesulfonic acid as the catalyst in dichloromethane.They were characterized by1H NMR,13C NMR and mass spectrometry.They had different1H NMR spectra but similar13C NMR spectra.The diameter of the internal cavity of P5 is ca.4.6,similar to those of cucurbit6]uril(ca.5.8) and α-cyclodextrin(ca.4.7).The diameter of the internal cavity of P6 is ca.6.7,similar to those of cucurbit7]uril(ca.7.3) and β-cyclodextrin(ca.6.0).The diameter of the internal cavity of P7 is ca.8.7,similar to those of cucurbit8]uril(ca.8.8) and γ-cyclodextrin(ca.7.5).The host-guest binding properties of them were investigated with n-octyltriethyl ammonium hexafluorophosphate G as a model guest.P6 showed complexation with G while weak complexation was observed between G and P5,but no complexation occurred between P7 and G.The1H NMR spectrum of an equimolar solution of P6 and G in chloroform-d showed only one set of peaks,indicating fast-exchange complexation between P6 and G on the 1H NMR time scale at 22 ℃.A mole ratio plot indicated that the complexation stoichiometry was 1∶1 between P6 and G.This was further confirmed by a low resolution electrospray ionization mass spectroscopy peak at m/z 1451.7 corresponding to P6G-PF6]+.The association constant of the 1∶1 complex P6G in chloroform-d was determined to be(740±86) L mol-1 by a proton NMR titration.These experiments demonstrate that G fits the cavity of P6 while it is too big for the cavity of P5 and too small for the cavity of P7.