Estimation of the Noncovalent Bond Dissociation Energies of the Gas-Phase Complexes of Macrocyclic Polyethers with Alkali Metal Cations Using an Electrospray Ionization/Triple Quadrupole Mass Spectrometer

摘要

An attempt to use the commercial triple quadrupole mass spectrometer,equipped with an electrospray ion source,to estimate the noncovalent bond dissociation energies of gas-phase complexes of macrocyclic polyethers with metal cations has been made.It was found that,after standardization of the experimental conditions,the collision cell voltage required for decomposition of 50% of the selected complex ions (CE_(50%)) is proportional to the binding energies with reasonable accuracy.Even better correlation was obtained after recalculation of the CE_(50%) values to the center-of-mass frame (ECM_(50%)).Measurements were made for 12-crown-4,15-crown-5,18-crown-6,and dibenzo-18-crown-6 complexes with alkali metal cations from Li~+ to Cs~+.These results indicate,that it is possible to estimate values of the binding energies after correct setting of the experimental conditions and using model compounds as the reference.