Encapsulation of N-phenyl p-phenylenediamine into β-CD: Spectral, molecular modelling studies and sensor application for detecting Fe2+ ion

Abstract

Encapsulation of N-phenyl p-phenylenediamine (NPpPDA) into β-cyclodextrin (β-CD) has been investigated by various experimental techniques as well as theoretical methods. The results of PXRD, FT-IR, NMR and SEM analysis confirm the formation of inclusion complex. Significant change occurs in the fluorescence spectral intensity of inclusion complex during the addition of Fe2+ ion as compared to other metal ions. This indicates Fe2+ chemo-sensing ability of this host-guest complex. Geometrical optimization and stability of the structure have been carried out using density functional method (DFT/B3LYP) with 6-31g (d,p) basis set. The delocalisation energy of various types of bonding interactions were investigated by Natural bond orbital (NBO) analysis. Topological parameters for bonds of interacting atoms of complex C1 have been calculated and intramolecular interactions were analysed using Atoms in molecule (AIM) theory. Both experimental as well as theoretical methods suggest that the orientation 1 is more favourable structure among the proposed two orientations. NBO results confirms the presence of strong interactions between occupied orbitals of host and vacant orbitals of NPpPDA molecule which play a key role with respect to the stability of NPpPDA:β-CD complex.