Reaction of NdIII and ErIII nitrate salts with a 1,3,5-tris­(dipicolylamine)-triazine (dpat) ligand yielded two unprecedented examples of [Ln­(NO3)6/5]3–/2– (Ln = Nd, Er) moieties completely encapsulated by the ligands. They are found in the two new complexes, [(H3 dpat)2]­[(Nd­(NO3)6)2]·2CH3CN (1), and the related [(H3 dpat)2]­[(Er­(NO3)5)3]·3CH3CN·2H2O (2). The structures of the complexes are similar and they crystallize in the triclinic P-1 space group with a = 12.1630(3), b = 12.2694(3), c = 17.6357(5) Å, V = 2611.10(12) Å3, and a = 14.3372(4), b = 17.1271(4), c = 25.2207(7) Å, V = 5934.7(3) Å3, respectively. Anion-π interactions, which are reported here for the first time for LnIII ion complexes, hydrogen bonding interactions and π–π stacking support the formation of the encapsulated species. Evidence of the protonated dpat ligand in 1 and 2 was found through isolation of (H2 dpat)­(NO3)2. Finally, the pH-dependent ability of the ligand to extract LaIII and nitrate ions from aqueous into toluene solution is demonstrated.

Dipicolylamine-functionalized 1,3,5-triazine (dpat) was isolated. When reacted with LaCl 3 , compound [(LaCl 6 )(H 3 dpat)][H 2 O] 2 (1) formed, which crystallized in the monoclinic P2 1 /n space group with parameters a = 11.47 Å, b = 19.22 Å, c = 20.98 Å, V = 4652.02 Å, and β = 90.53°. When reacted with NdCl 3 , the complex [NdCl 3 (H 2 O) 4 (H 3 dpat)][Cl] 3 (MeOH) 2 (2) crystallized in the monoclinic P2 1 /n space group with unit cell parameters a = 20.05 Å, b = 12.81 Å, c = 20.64 Å, V = 5004.40 Å, and β = 110.20°.In both cases, the dpat ligand forms a bowl-shaped cavity that partially envelops the Ln III -containing central unit, which is anionic in 1 and neutral in 2. The formation of these outer-sphere complexes is supported by secondary interactions, including π−π stacking, hydrogen bonding, and anion−π between the chlorolanthanide-(III) fragment and the electron-deficient 1,3,5-triazine ring. Evidence of protonation of the pyridine rings in dpat was substantiated through the isolation of [H 2 dpat][Cl] 2 (3). This compound crystallized in the monoclinic C2/c space group with parameters a = 11.93 Å, b = 20.22 Å, c = 15.28 Å, V = 3664.97 Å, and β = 94.35°. Four pyridine rings are pairwise protonated in 3. dpat showed a moderate ability to extract La III from an aqueous to an organic phase, indicating its potential, through judicious manipulation of secondary-sphere interactions, as the starting point for efficient extractants for Ln III ions.

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