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 K d 1 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 K d 1 and K d 2 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 K d values obtained from fluorescence spectroscopy were in agreement with those from ESI‐MS titration. Copyright © 2010 John Wiley & Sons, Ltd.