Synthesis And Properties Of Schiff Base Macrocycles Containing Imide Groups

In recent years,the design and synthesis of novel artificial receptors that have strong affinity and selectivity for specific anions have been receiving great attentions due to their important role in a wide range of chemical,biological,medicine and environmental applications.Urea group contains two acidic NHs which can provide double hydrogen bond with anionic so that it is a good hydrogen bond donor.In this paper,two [1+1] novel Schiff base macrocycles containing rigid urea-functionalized units were designed and synthesized.The two compounds were characterized by1 H NMR,FT-IR and MS,and their crystal structures were analyzed by single X-ray diffraction.Besides,the recognition properties of the Schiff base macrocycles with anions were studied and the adsorption properties of the Schiff base macrocycles with methanol were investigated as well.The research work of this paper is as follows:1.Synthesis and characterization of Urea-Functionalized diamideDiamine A1: 1,3-bis?3-amino-phenyl?-urea was synthesized from m-nitrobenzoic acid with m-nitroaniline,and further nitro-groups were reduced to amine-groups.Diamine A2: N,N'-?2-amino-phenyl?-2,6-bis-urea benzene was synthesized from m-nitrobenzoyl chloride with m-nitroaniline,and further nitro-groups were reduced to amine-groups.The two diamide compounds were characterized by 1H NMR and FT-IR.2.Synthesis and characterization of rigid dialdehyde.Dialdehyde B1: 1,3-bis?2-formylphenoxy?-2-propoa-nol and B2: 5,5'-methylenebis-salicylaldehyde were synthesized from salicylic aldehyde with epichlorohydrin and 1,3,5-trioxacyclohexane,repectively.The dialdehyde compounds were characterized by 1H NMR and FT-IR.3.Synthesis and characterization of urea-functionalized Schiff Base macrocycliccompounds.The Schiff base macrocycle L₁ was synthesized from the reaction of precursors1,3-bis?3-amino-phenyl?-urea?A1?with 1,3-bis?2-formylphenoxy?-2-propa-nol?B1?.The Schiff base macrocycle L₂ was synthesized from N,N'-?2-amino-phenyl?-2,6-bis-urea benzene?A2?with 5,5'-methylene-bis-salicyl-aldehyde?B2?,by a direct synthesis method.The macrocycle compounds were characterized by 1H NMR,FT-IR,and MS,and their crystal structures were determined by single X-ray diffraction.4.The research on anions recognition and methanol adsorption properties of Schiff base macrocycles.?1?The UV-vis absorption spectrum technique was adopt to investigate the coordination of macrocycle L₁ and L₂ with a series of anions in the solution.The results showed that the [1+1] Schiff base macrocycle L₁ displays a selective recognition ability for AcO-,and the [1+1] Schiff base macrocycle L₁ binds AcO-ion in a 1:1 stoichiometry with binding constants of?8.226±0.7?×104L·mol-1,and thermodynamic parameters of the coordination reaction were obtained,namely??rHm=?-12.86±0.3?kJ·mol-1,T?rSm=15.18 kJ·mol-1,?rGm =?-28.04±0.3?kJ·mol-1?.The [1+1] Schiff base macrocycle L₂ displays a selective recognition ability for AcO-,HSO4-and H2PO4-,and the [1+1] Schiff base macrocycle L₂ binds HSO4-ion in a 1:1 stoichiometry with binding constants of?2.18±0.4?×104 L·mol-1,?2?BET surface area,specific pore volume,and adsorption properties of macrocycle L₁ with methanol were also studied by ASAP 2020 physical adsorption apparatus.The results showed that the maximum adsorption amount was 2.84mmol·g-1.