Abstract:
Cucurbit
nurils (CB
ns) are macrocyclic host molecules with polar carbonyl groups on both portals, which enable CB
ns to bind strongly and selectively with cationic species, especially to protonated organic amines. Here, a supramolecular polymer has been successfully constructed by the self-assembly between a cucurbit5uril analogue (decamethyl substituted methylene bridge cucurbit5uril, Me
10TD5) and 1,3,6,8-tetrakis(4-aminophenyl) pyrene tetrahydrochloride salt in aqueous solution through portal interactions. Diverse measurements were used to characterize the formation of this polymer, including fluorescence emission spectrum,
1H-NMR spectroscopy, dynamic light scattering (DLS) and transmission electron microscopy (TEM). The
1H-NMR measurements and the Job's plot indicated that 1,3,6,8-tetrakis(4-aminophenyl) pyrene tetrahydrochloride salt and Me
10TD5 were combined in a mole ratio of 1∶2. The association constant (
Ka) was calculated to be (7.1 ± 0.7) × 10
4 L/mol by non-linear curve-fitting method based on the fluorescence experiments. Transmission electron microscopy image and the dynamic light scattering measurements demonstrated that 1,3,6,8-tetrakis(4-aminophenyl) pyrene tetrahydrochloride salt and Me
10TD5 could self-assemble into supramolecular polymers and the self-assembly behavior would lead to a certain degree of red shift of the maximum emission wavelength along with the decrease in fluorescence intensity. Meanwhile, the recognition performance of the polymer on metal ions was studied. Upon the addition of Ba
2+, Ca
2+, Co
2+, Ni
2+, Pd
2+, Zn
2+, Fe
2+, Mg
2+, Cd
2+, Mn
2+, Cu
2+, it was found that Ba
2+ could significantly enhance the fluorescence of the system and had a certain degree of anti-interference. Therefore, this polymer can be used to detect Ba
2+, and the detection limit of the polymer for Ba
2+ is 7.6 × 10
-6 mol/L.