Towards the design of ionic traps incorporating thermolabile units: structural characterization of copper(II), palladium(II) and rhodium(II) complexes with the aminoalcohol ligand 2-(pyridin-2-ylamino)ethanol.

Abstract

Aminoalcohol-based ligands incorporating heteroaromatic moieties, such as 2-(pyridin-2-ylamino)ethanol (L¹), are of particular interest in coordination chemistry due to their dual donor character and conformational adaptability. A series of L¹-based transition-metal complexes, namely, diacetatobis[2-(pyridin-2-ylamino)ethanol]palladium(II), [Pd(C₂H₃O₂)₂(C₇H₁₀N₂O)₂] or [PdL¹₂(OAc)₂] (1), and the copper(II) analogue (4), tetra-μ-acetato-bis{[2-(pyridin-2-ylamino)ethanol]rhodium(II)}, [Rh₂(C₂H₃O₂)₄(C₇H₁₀N₂O)₂] or [Rh₂L¹₂(OAc)₄] (2), and the copper(II) analogue (3), and the nitrate salt 2-[(2-hydroxyethyl)amino]pyridinium nitrate, C₇H₁₁N₂O⁺·NO₃^- or L¹·NO₃ (5), were structurally characterized using single-crystal X-ray diffraction (SCXRD). Crystallographic analyses revealed well-defined coordination modes and distinct supramolecular architectures influenced by the nature of the metal centre. These findings demonstrate the ability of the L¹ ligand to form well-defined crystalline complexes with Cu, Pd and Rh ions, providing valuable crystallographic benchmarks for understanding the coordination preferences and crystal packing effects in pyridyl-aminoalcohol systems. The presented results provide a foundation for the further design of ionic traps involving thermolabile moieties.