Formation and Fragmentation Chemistry of Tripositive Ln(TMGA)3(3+) Complexes in the Gas Phase.

Electrospray ionization (ESI) of LnCl3 (Ln = La-Lu except Pm) and TMGA (tetramethyl glutaramide) mixtures resulted in the formation of gas-phase Ln(TMGA)3(3+) 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)3(3+) except Eu(TMGA)3(3+) which predominantly forms divalent Eu(II)(TMGA)2(2+) complex via loss of TMGA(+). Analogous Yb(II)(TMGA)2(2+) and Sm(II)(TMGA)2(2+) complexes arising from charge reduction were also observed, in competition with the formation of charge conserving Yb(III)(TMGA)(TMGA-H)(2+) and Sm(III)(TMGA)(TMGA-H)(2+) products. The yield of these charge reducing products follows their reduction potentials in condensed phase. In addition to Ln(TMGA)3(3+), tripositive ions such as Ln(TMGA)4(3+) and Ln(TMGA)2(3+) were experimentally identified as well. While the former was observed along with Ln(TMGA)3(3+) during ESI, the latter was observed upon CID of Ln(TMGA)3(3+), suggesting two TMGA molecules can stabilize Ln(3+) in the gas phase. Graphical Abstract ᅟ.