Spectroscopic and Molecular Modeling Studies of the Inclusion Complex of TNBAB with β-cyclodextrin in Aqueous Solution

Abstract

In this investigation, a novel surfactant (N, N, N-trimethyl-4-(5-(octyloxy) naphthalene-1-yloxy) butan-1-aminium bromide, TNBAB) with a naphthalene chromophore moiety was designed and synthesized. The UV, fluorescence and ¹H NMR measurements and molecular modeling have been carried out at 298.2 K for TNBAB + H₂O, and TNBAB +β-CD + H₂O systems. The stoichoimetry, stability constant and potential energy surface for the inclusion complex of TNBAB and β-CD have been determined. The results of UV and fluorescence suggested that β-CD formed strong complex with TNBAB, the stoichoimetry was found to be almost 1:1, and the inclusion constants obtained are larger than 2.1×10⁴ L mol^-1. ¹H NMR and molecular modeling studies indicated β-CD and TNBAB could form a two different inclusion complexes (Fig. 9), the two part of the aliphatic chain (one including partly naphthalene nucleus) were encapsulated in the cavity of the β-CD through hydrophobic interaction, respectively.