Studies on the non‐covalent interactions between cyclodextrins and aryl alkanol piperazine derivatives by mass spectrometry and fluorescence spectroscopy

The non-covalent complexes of α- and β-cyclodextrins (α-, β-CDs) with two aryl alkanol piperazine derivatives (Pipe I and Pipe II) have been studied by electrospray ionization mass spectrometry (ESI-MS) and fluorescence spectroscopy. The ESI-MS experimental results demonstrated that Pipe I can conjugate to β-CD and form 1:1 or 1:2 stoichiometric non-covalent complexes, and Pipe II can only form 1:1 complexes with α- or β-CD. Fluorescence spectra indicated that the fluorescence intensities of Pipe I and Pipe II can be enhanced by increasing the content of β-CD. The mass spectrometric titration experiments showed that the dissociation constants Kd1 were 5.77 and 9.52 × 10−4 mol L−1 for the complexes of α-CD with Pipe I and Pipe II, respectively, revealing that the binding of α-CD-Pipe I was stronger than α-CD-Pipe II. The Kd1 and Kd2 values were 9.81 × 10−4 mol L−1 and 1.11 × 10−7 (mol L−1)2 for 1:1 and 1:2 complexes of Pipe I with β-CD, respectively. The Kd values obtained from fluorescence spectroscopy were in agreement with those from ESI-MS titration. Copyright © 2010 John Wiley & Sons, Ltd.