Supramolecular Encapsulation of [Nd(NO ₃ ) ₆ ] ^3– by <i>dpat</i> Retained in Acetonitrile

Understanding how outer-sphere interactions influence the inner-sphere structure of lanthanide complexes in solution is crucial for advancing applications in separations, materials, and nuclear chemistry. Here, we investigate the solution-phase coordination environment of Nd(NO₃)₃ in acetonitrile encapsulated by the dipicolylamine-functionalized triazine ligand <i>dpat</i>. Extended X-ray absorption fine structure (EXAFS) spectroscopy at the Nd L₃-edge was used to probe the solution structures, while ab initio molecular dynamics (AIMD) simulations provided atomistic models of the ion coordination environment. The supramolecular encapsulation complex [Nd(NO₃)₆(H₃<i>dpat</i>)₂]³⁺, previously identified in the solid state, is shown to persist in an acetonitrile solution without substantial changes to its structure or first coordination shell. Theoretical EXAFS spectra derived from the AIMD simulations reproduce the experimental features, confirming that <i>dpat</i> encapsulation stabilizes the high-nitrate coordination environment in solution. These findings underscore the role of weakly coordinating molecules (nitrate, acetonitrile, and <i>dpat</i>) in shaping the structure of solvated lanthanide complexes.