Research On Molecular Assembly And Properties Based On Non-covalent Interactions

The structure of supramolecular assembly based on noncovalent interactions is sensitive to the changes of the external environment.It is easy to achieve the construction and regulation of micro/nano scale assembly by changing external conditions.The original molecular structure and properties are still maintained especially in the assembly structure,which facilitates the targeted application of their assembly materials in practical applications.In this paper,the[1+1]and[2+2]Schiff base macrocycles containing the group of pyridine 2,6-dicarboxamide were synthesized from the reaction of the precursors diamine and dialdehyde derivatives,and the solid microspheres of different sizes and structures were obtained by suitable molecular assembly technology.It has been shown that three kind of microspheres with nuclear core-shell structures of different sizes can be obtained from the[2+2]Schiff base L_a containing phenol rings.The solid microspheres can be obtained from the[2+2]Schiff macrocycle L_c containing the furan units.The equilibrium and transformation of[2+2]Schiff base(L_c)and[1+1]Schiff base(L_b)was achieved through the modification of the polar properties of the assembled solvent using the reversible principle of the Schiff base condensation reaction and the microspheres were induced and assembled to form core-shell or hollow-tructures.??The synthesis and characterization of Schiff base macrocycles L_a?L_b and L_c(1)Synthesis of precursors dialdehydes and diamines5,5'-methylene-bis-salicylaldehyde was synthesized from salicylic aldehyde;2,2-bis(5-formyl-2'-furyl)propanewassynthesizedfromfuran;and N,N'-(2-amino-phenyl)-2,6-bis-formyliminepyridine was synthesized from the reaction of 2,6-pyridine dicarboxylic acid with o-Nitroaniline.(2)The synthesis of[2+2]Schiff base macrocycles L_a and L_c and[1+1]Schiff base macrocycles L_bThe Schiff base macrocycle L_c was synthesized from the reaction of2,2-bis(5-formyl-2'-furyl)propane with N,N'-(2-amino-phenyl)-2,6-bis-formylimine pyridine under the catalysis of acid.The[2+2]Schiff base macrocycle L_a?[1+1]Schiff base macrocycle L_b and[2+2]Schiff base macrocycle L_c were characterized by ~1H NMR and MS spectrometry.Their structures were analyzed by X-ray single diffraction,and their supramolecular assembly structures and properties were obtained based on the intermolecular noncovalent interactions.??Microspheres self-assembly and characterization of Schiff base macrocycles L_a and L_c(1)Conditions of self-assembly microspheres:The sizes and structures of microspheres based on the acids,acidity solvent polarity were investigated and the optimum parameters for the self-assembled microspheres were obtained.(2)Microspheres were characterized by MS,FT-IR,thermal analysis,scanning electron microscopy(SEM),and transmission electron microscopy(TEM).3.ConclusionThe Schiff base macrocycles containing the group of pyridine 2,6-dicarboxamide is a sort of widely used artificial anion receptor in the study of anion recognition.However,only a few papers have been reported,in which micro/nano materials were obtained from Schiff base macrocycles based on intermolecular noncovalent interaction.This research will provide a new way for similar macrocycles in micro/nano materials assembly and their application research.