Synthesis, Structure And Properties Of Aromatic Carboxylic Acid-Assisted Metal-Cucurbituril Complexes

Cucurbit[n]uril?abbreviated as CB[n]?and its derivatives are a series of novel macrocyclic host molecules linked by many glycoluril units.Because of their inexpensive synthetic raw materials,simple synthesis methods,rigid structures,unique hydrophobic internal cavity and ports consisting of surrounding carbonyl oxygen atoms,it has attracted a great deal of attention in recent years.This makes it possible to construct a supramolecular assembly of various functions through hydrophobic interaction,hydrogen bonding,ion-dipole,respectively,and it has great application potential in adsorption,sensor,catalysis,molecular switch,organic solvent detection,metal ion recognition and so on.In this paper,we selected isonicotinic acid?HINA?,5-sulfoisophthalic acid sodium salt?NaH₂SIP?,isophthalic acid?H₂ipa?as the auxiliary ligand,the CB[6]was used as the main ligand,and a CB[6]-based supramolecular assemblies was synthesized under the solvothermal reaction conditions.The obtained coordination compounds and structurally determined were characterized by X-ray single crystal diffraction,powder X-ray diffraction,ultraviolet-visible spectroscopy,infrared spectroscopy?IR?,thermogravimetric analysis?TG?et al.The adsorption of organic dyes by complexes and the recognition of organic solvents were studied.The specific works are as follows:1.With CB[6]as the main ligand and isonicotinic acid as a bridging ligand,a complex was prepared by reacting with CdCl₂·2.5H₂O under solvothermal conditions.The Cd²⁺ion in the complex is coordinated to the oxygen atom of an isonicotinic acid ligand,an acetic acid molecule,a water molecule,an N atom of INA^-,and a chloride ion from CdCl₂,respectively.Adsorption experiments demonstrated that the complex can rapidly and efficiently adsorb the dye molecule reactive blue 19?RB19?.{[Cd₂Cl₂?INA?₂?HCOO?₂?H₂O?₂]?CB[6]?·2?HCOOH?·5H₂O}?1?2.With CB[6]as the main ligand and 5-sulfonate isophthalic acid sodium salt as the auxiliary ligand,a supramolecular complex 2 was synthesized by reacting with CdCl₂·2.5H₂O under solvothermal reaction conditions.The Cd²⁺ion in the supramolecular complex 2 coordinates with four H₂O molecules and a carboxyl oxygen atom from two SIP^3-ligands to form a six-coordinate structure.The experimental results showed that the complex not only can effectively adsorb the organic dye molecule RB19 but also has a significant recognition effect on acetone.[Cd₂?SIP?₂?H₂O?₈·CB[6]·4H₂O]^2-?2?3.With CB[6]as the main ligand and isophthalic acid as an auxiliary ligand,a new complex based on CB[6]was obtained by reacting with CdCl₂·2.5H₂O under solvothermal conditions.The Cd²⁺ion in the complex is a seven-coordinated position in which the coordinating oxygen atom is derived from a carbonyl group in N,N-dimethylformamide?DMF?,the carbonyl group of two CB[6],two water molecules,and carboxyl group of ipa^2-.Thermogravimetric analysis revealed that the complex has strong thermal stability.[Cd?ipa?·DMF]?CB[6]?·2H₂O?3?...