An electrospray ionization mass spectrometric study of beryllium chloride solutions and complexes with crown ether and cryptand macrocyclic ligands

Abstract

The speciation of beryllium chloride solutions has been investigated using electrospray ionization mass spectrometry in both positive and negative ion modes. The majority of observed species were mixed beryllium-chlorido-oxido-hydroxido species, with the degree of hydration of the observed ions depending on the number of chloride ions. The observed species contain between 1 and 6 Be ions. The interactions of BeCl2 with a selection of crown ether ligands and cryptand[2.2.2] were also investigated using ESI MS. These ligands have low affinity for Be2+, instead the observed ions are dominated by species formed from adventitious Na+ or K+ ions. The crown ether 12-crown-4 showed the most complex spectra, as a result of greater interactions with Be2+, as evidenced by observed ions such as [BeX(12-crown-4)]+ (X = Cl or OH). The interactions of crown ethers with beryllium ions (as well as coordinated Cl- or OH- ancillary ligands) were investigated using Density Functional Theory [B3LYP/6-311++G(dp)], where it was shown that the species [BeX(crown ether)]+ (X = Cl or OH) are considerably more stable than [Be(crown ether)]2+ species, with 12-crown-4 forming the most stable complex. The combination of ESI MS and DFT investigations indicates that full encapsulation of the Be2+ by crown ethers is unfavorable, and coordination with an accompanying hydroxide or chloride is preferred.