Formation and Fragmentation Chemistry of Tripositive Ln(TMGA)33+ Complexes in the Gas Phase.

Abstract

Electrospray ionization (ESI) of LnCl3 (Ln = La-Lu except Pm) and TMGA (tetramethyl glutaramide) mixtures resulted in the formation of gas-phase Ln(TMGA)33+ complexes, where tripositive lanthanide cation was coordinated by three neutral TMGA ligands. Collision induced dissociation (CID) was employed to investigate the fragmentation chemistry of these tripositive complexes. Ln(TMGA)2(TMGA- 45)3+ resulting from Ccarbonyl-N bond cleavage of TMGA and hydrogen transfer is the major CID product for all Ln(TMGA)33+ except Eu(TMGA)33+ which predominantly forms divalent EuII(TMGA)22+ complex via loss of TMGA+. Analogous YbII(TMGA)22+ and SmII(TMGA)22+ complexes arising from charge reduction were also observed, in competition with the formation of charge conserving YbIII(TMGA)(TMGA-H)2+ and SmIII(TMGA)(TMGA-H)2+ products. The yield of these charge reducing products follows their reduction potentials in condensed phase. In addition to Ln(TMGA)33+, tripositive ions such as Ln(TMGA)43+ and Ln(TMGA)23+ were experimentally identified as well. While the former was observed along with Ln(TMGA)33+ during ESI, the latter was observed upon CID of Ln(TMGA)33+, suggesting two TMGA molecules can stabilize Ln3+ in the gas phase. Graphical Abstract ᅟ.