The stability of some porphyrin-calixarene sodium-ion complexes were determined by a collision-activated decomposition (CAD) method utilizing electrospray ionization mass spectrometry (ESI-MS). Comparing the values of E1/2, the collision energy at which the relative intensity of the complex ion is 0.5, we found that the porphyrin-calixarene complex with the higher value of E1/2 corresponded to that with the larger association constant (Kass), as measured by 1H-NMR in CDCl 3. Both our ESI-MS and NMR studies proved that the number of hydrogen bonds and the rigidity of the calixarene stabilized the complex. The ESI-MS technique could be successful in screening the binding affinity in host-guest systems with a small amount of sample.
ASJC Scopus subject areas
- Analytical Chemistry