Anion‑π and H‑Bonding Interactions Supporting Encapsulation of [Ln(NO3)6/5]3–/2– (Ln = Nd, Er) with a Triazine-Based Ligand

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, [(H3dpat)2]­[(Nd­(NO3)6)2]·2CH3CN (1), and the related [(H3dpat)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 (H2dpat)­(NO3)2. Finally, the pH-dependent ability of the ligand to extract LaIII and nitrate ions from aqueous into toluene solution is demonstrated.