基于非共价镊合作用的线形超分子聚合物

Construction of Linear Supramolecular Polymers on the Basis of Non-covalent Molecular Tweezer/Guest Recognition

基于"镊合导向自组装"策略构筑超分子聚合物,可实现电子给受体基元在组装体层次的精确排列,设计并制备了基于三联吡啶铂(Ⅱ)炔分子镊子主体的AA型单体分子,以及基于芘客体的BB型单体分子.通过在芘客体上引入酰胺基元,在非共价镊合过程中可产生分子间NH―N氢键作用.通过氢键和供受体相互作用力的高效协同,显著提高了非共价镊合体系的结合强度,其结合常数可达到(3.58±0.01)×105(mol/L)?1,相比于未取代芘客体,其结合强度呈现出2个数量级的显著提高.在此基础之上,对AA、BB型单体分子的超分子聚合行为展开了深入的研究.结合实验及理论计算,证实在高浓度状态下,两单体分子通过自组装可获得具有高分子量特征的线形超分子聚合物.同时,考察了超分子聚合物的动态可逆性,通过温度的改变及链终止剂的加入,可实现超分子聚合物的可逆自/解组装过程.

Supramolecular polymers represent a novel class of macromolecules, in which self-assembly serves as a powerful tool and holds the monomeric units together via reversible non-covalent bonds. The ideal non-covalent recognition units should concomitantly fulfill high complexation directionality, strong binding affinity and stimuli-sensitive responsiveness. To meet the requirements, hydrogen bond, metal-ligand and macrocyclic host-guest interactions have been widely served as the non-covalent driving forces for controlled supramolecular polymerization processes. The expansion of novel driving forces and the corresponding recognition motifs are of paramount importance for the current supramolecular polymers researches. In this regard, integration of donor and acceptor chromophores in a mixed supramolecular polymeric array is intriguing, since it is an efficient way to construct nano-sized optoelectronic devices. However, due to the non-specific and non-directional properties of electron donor-acceptor interactions, a variety of erratic stacking modes （such as phase segregation, random or alternating mixing） could potentially exist in the resulting supramolecular polymeric assemblies. Hence, the precise organization of multi-component z-aromatic systems is highly desirable. Our research group has recently developed a ＂tweezering directed self-assembly＂ strategy for the construction of well-ordered supramolecular donor-acceptor polymers. As a research extension, herein a novel alkynylplatinum（II） terpyridine molecular tweezer/pyrene recognition motif is investigated, which features with intermolecular NH--N hydrogen bond between the amide unit on the guest and the pyridine moiety on the molecular tweezer. Ascribing to the elaborate combination of donor-acceptor and hydrogen-bonding interactions, it demonstrates rather strong binding affinity （K~ = 3.58 x 105 （mol/L）-l）. Moreover, by modulating the intermolecular NH--N hydrogen bonds involved in the system, its binding affinity exhibits significantly large variations towards external stimuli. Such non-covalent recognition motifs are further employed as the connecting units for the fabrication of high-molecular-weight supramolecular polymers. Moreover, the resulting polymeric assemblies exhibit interesting dynamic temperature-responsive behaviors, which are promising for the development of adaptive π-functional materials.