The supramolecular interaction of anthracene (ANT) and phenanthrene (PHN) with cucurbit[n]uril, CB [n] (n = 6-8) has been investigated in aqueous media for the first time. The inclusion complexes were investigated and characterized by fluorescence spectroscopy, matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry, and 1HNMR. The stability of these complexes and the mode of inclusion in aqueous media at atomistic levels were monitored by molecular dynamic (MD) simulations. The results obtained from the experimental and MD studies have demonstrated the formation of stable 1 : 1 complexes between the two guests with all hosts in aqueous media. From the fluorescence study, the binding constants of PHN with CB[6], CB[7], and CB[8] were found to be 398 � 63, 544 � 128, and 655 � 162 M À 1 , respectively. Whereas, ANT-CB[n] formation constants are 213 � 37 M À 1 270 � 35 M À 1 , and 356 � 94 M À 1 for CB [6], CB[7], and CB[8], respectively. The results obtained show that the size of the cavity of the macrocycle and the polarity of the rim play an important role in the stability of the formed complex. Surprisingly, CB[6] forms an inclusion complex with ANT while it interacts by its side with PHN through dipole-dipole interaction. The larger cavity sizes of CB[7], CB[8], were found to encapsulate the two guests forming highly stable inclusion complexes.

The inclusion complexes of cucurbit[n]uril, CB[n] (n = 6–8), with poly aromatic hydrocarbon (PAH) Benzo(a)Pyrene (BaP), and fluoranthene (FLT) were investigated carefully in aqueous media. Fluorescence and 1H NMR spectroscopy were used to characterize and investigate the inclusion complexes that were prepared in the aqueous media. The most predominant complexes of both guests with hosts were the 1:1 guest: host complexes. Stability constants of 2322 ± 547 M−1, 7281 ± 689 M−1, 3566 ± 473 M−1 were obtained for the complexes of BaP with CB[6], CB[7], and CB[8], respectively. On the other hand, stability constants of 5900.270 ± 326 M−1, 726.87 ± 78 M−1, 3327.059 ± 153 M−1 were obtained for the complexes of FLT with CB[6], CB[7], and CB[8], respectively. Molecular dynamic (MD) simulations were used to study the mode and mechanism of the inclusion process and to monitor the stability of these complexes in aqueous media at an atomistic level. Analysis of MD trajectories has shown that both BaP and FLT form stable inclusion complexes with CB[7] and CB[8] in aqueous media throughout the simulation time, subsequently corroborating the experimental results. Nevertheless, the small size of CB[6] prohibited the encapsulation of the two PAHs inside the cavity, but stable exclusion complex was observed between them. The main driving forces for the stability of these complexes are the hydrophobic forces, van der Waals interactions, electrostatic effect, the π····π and C‒H···π interaction. These results suggest that BaP and FLT can form stable complexes with CB[n] (n = 6–8) in solution.