Face-Rotating Polyhedra:From New Building Blocks To New Cages

In recent years,discrete molecular cage compounds have attracted broad research interests due to their potential applications in catalysis,molecular recognition and gas storage.Among all types of molecular cages,chiral cages are particularly important because they possess unique asymmetric nano-sized cavity and have been applied in asymmetric catalysis,separation of small chiral molecules,and chiral recognition.Our group have reported a series of molecular face-rotating cages(FRP)and a novel approach to construct chiral cages,transferring two-dimensional chirality of facial building blocks to the three-dimension chirality of cages.The FRP have shown interesting assembly behavior and chiral optical properties.However,the FRP reported so far do not have large cavities to develop host-guest chemistry because the cavities are filled with alkyl chains of facial building block.Moreover,the molecular cages connected through non-covalent interactions have been widely investigated,it is still challenging to separate these chiral cages due to their high polarity and instability.Hence,this dissertation uses a new type of facial building blocks to construct a series of novel face-rotating polyhedra through dynamic covalent chemistry,and chiral-separate these FRP.This dissertation reviewed various dynamic covalent reactions,including olefin or alkyne metathesis reaction,boric acid condensation reaction and imine condensation reaction.This dissertation uses imine condensation reaction to construct molecular cage compounds.In addition,we introduced the facial building block triazatruxene and its assembly behavior and optoelectronic applications.Finally,we introduce the principles and contents in this dissertation:using triazatruxene based facial building blocks to construct a series of "hollow" molecular FRP through dynamic imine chemistry.This dissertation mainly includes four parts:In this dissertation,we designed and synthesized two triazatruxene aldehyde derivatives TAT-CHO-1 and TAT-CHO-2 as the facial building blocks of FRP.The core of the two facial building blocks were triazatruxene,which is a C3h symmetric planar molecule with excellent hole transporting property.The only difference between TAT-CHO-1 and TAT-CHO-2 is the positions of three aldehyde groups,and we applied two different routes to synthesize these two derivatives.More importantly,the alkyl chains of these two derivatives are almost on their molecular planes,thus preventing any form of facial interaction and resulted in "hallow" FRP.In the following work,we found that the subtle structural difference between those two facial building blocks led to distinct geometry and diastereoselectivity of the final assemblies.In chapter 2,we assembled TAT-CHO-1 and(1R,2R)-cyclohexanediamine(CHDA)into[4+6]octahedral FRP-8 through imine condensation reaction.Because in FRP-8 the faces are only connected through imine bonds and no facial interactions among the alkyl chains,the assembly process exhibits no diastereoselectivity and gave all the five possible diastereoisomers,i.e.CCCC,CCCA,CCAA,CAAA and AAAA(C stands for clockwise and A for anti-clockwise).The five diastereoisomers were separated by chiral column chromatography,and their rotational patterns were assigned through NMR spectra and circular dichroism.This work demonstrates the first example of assembly of one achiral face and one chiral vertice into five different diastereoisomers through one-pot reaction.In chapter 3,the imine condensation reaction of TAT-CHO-2 and(1R,2R)-cyclohexanediamine provided[2+3]prism cage R-FRP-9 and its assembly process exhibits high degree of diastereoselectivity.In theory,the[2+3]-prism cage has three possible stereoisomers,i.e.,AA,CA and CC.In single crystal structures of R-FRP-9,only AA prism was found,in accordance with high molecular symmetry inferred from NMR spectra.More importantly,the two faces in R-FRP-9 have ?-?interactions,which lead to apparent diastereoselectivity in the assembly process.The FRP-9 assembled into one-dimensional columns in crystals.We obtained the HOMO and LUMO energy levels of FRP-9 through its UV-vis spectroscopy,fluorescence emission spectroscopy and cyclic voltammetry curve.We also tried to use FRP-9 as the hole transporting material for perovskite solar cells.However,the distance between the two faces of FRP-9 are too small to accommodate any guest molecule,and thus can be considered as "hollow" cages.In chapter 4,we used a naphthalene diimide-based derivatives as diamine to construct FRP with larger size.Both TAT-CHO-1 and TAT-CHO-2 assembled with naphthalene diimide derivatives R-NDI-2NH2 into[2+3]prism cage,but their diastereoselectivities are completely different.By chiral HPLC analysis and NMR spectra,we confirmed that TAT-CHO-1 and R-NDI-2NH2 assembled into two diastereoisomers,i.e.CC and CA.Interestingly,TAT-CHO-2 and R-NDI-2NH2 assembled into only one diastereoisomer CA,exhibiting high degree of diastereoselectivity.