Tripositive Ln(TMTDA)(3)(3+) complexes (Ln = La-Lu except Pm, TMTDA = tetramethyl 3-thio-diglycolamide) were observed in the gas phase by electrospray ionization of LnCl(3) and TMTDA mixtures. Collision-induced dissociation (CID) was employed to investigate their fragmentation chemistry, which revealed the influence of metal center as well as ligand on the ligated complexes. Ln(TMTDA)(2)(TMTDA-45)(3+) resulting from C-carbonyl-N bond cleavage of TMTDA and hydrogen transfer was the major CID product for all Ln(TMTDA)(3)(3+) except Eu(TMTDA)(3)(3+), which predominantly formed charge-reducing product Eu-II(TMTDA)(2)(2+), via electron transfer from TMTDA to Eu3+. Density functional theory calculations on the structure of La(TMTDA)(3)(3)+ and Lu(TMTDA)(3)(3+) revealed that Ln(3+) was coordinated by six O-carbonyl atoms from three neutral TMTDA ligands, and both complexes possessed C-3h symmetry. The S-ether atom deviating from the ligand plane was not coordinated to the metal center. On the basis of the CID results of Ln(TMTDA)(3)(3+), Ln(TMGA)(3)(3+), and Ln(TMOGA)(3)(3+), the fragmentation chemistry associated with the ligand depends on the coordination mode, while the redox chemistry of these tripositive ions is related to the nature of both metal centers and diamide ligands.