Electrospray ionization of LnCl(3) and tetramethylpyridine-2,6-dicarboxamide (TMPDA) mixtures in methanol generated abundant tripositively charged Ln(TMPDA)2(3+) ions with an unprecedented 1:2 stoichiometry in the gas phase. Different from the very common 1:3 Ln(L) (L = TMGA, tetramethyl glutaramide; TMOGA, tetramethyl-3-oxaglutaramide; TMTDA, tetramethyl-3-thiodiglycolamide) complexes, Ln(3+) is coordinated by four O(c)and two Npyridine atoms from two perpendicular TMPDA ligands based on the DFT calculations. The observation of 1:2 Ln(TMPDA)(2) in the gas phase is due to the desolvation of Ln(TMPDA)(MeOH)(2) that is predominant in the methanol solution of LnCl and TMPDA according to the extended X-ray absorption fine structure analysis, and the 1:3 Ln(TMOGA)3and Ln(TMGA)(3)(3+) complexes observed in the gas phase also parallel the speciation in relevant solutions. Such a difference in solution speciation is most likely a result of the unfavorable steric effect caused by the pyridine ring of TMPDA.