pH-Specific Hydrothermal Assembly of Binary and Ternary Pb(II)-(O,N-Carboxylic Acid) Metal Organic Framework Compounds: Correlation of Aqueous Solution Speciation with Variable Dimensionality Solid-State Lattice Architecture and Spectroscopic Signatures

Abstract

Hydrothermal pH-specific reactivity in the binary/ternary systems of Pb­(II) with the carboxylic acids <i>N</i>-hydroxyethyl-iminodiacetic acid (Heida), 1,3-diamino-2-hydroxypropane-<i>N</i>,<i>N</i>,<i>N</i>′,<i>N</i>′-tetraacetic acid (Dpot), and 1,10-phenanthroline (Phen) afforded the new well-defined crystalline compounds [Pb­(Heida)]_<i>n</i>·<i>n</i>H₂O­(<b>1</b>), [Pb­(Phen)­(Heida)]·4H₂O­(<b>2</b>), and [Pb₃(NO₃)­(Dpot)]_<i>n</i>(<b>3</b>). All compounds were characterized by elemental analysis, FT-IR, solution or/and solid-state NMR, and single-crystal X-ray diffraction. The structures in <b>1</b>–<b>2</b> reveal the presence of a Pb­(II) center coordinated to one Heida ligand, with <b>1</b> exhibiting a two-dimensional (2D) lattice extending to a three-dimensional (3D) one through H-bonding interactions. The concurrent aqueous speciation study of the binary Pb­(II)–Heida system projects species complementing the synthetic efforts, thereby lending credence to a global structural speciation strategy in investigating binary/ternary Pb­(II)-Heida/Phen systems. The involvement of Phen in <b>2</b> projects the significance of nature and reactivity potential of N-aromatic chelators, disrupting the binary lattice in <b>1</b> and influencing the nature of the ultimately arising ternary 3D lattice. <b>3</b> is a ternary coordination polymer, where Pb­(II)-Dpot coordination leads to a 2D metal–organic-framework material with unique architecture. The collective physicochemical properties of <b>1</b>–<b>3</b> formulate the salient features of variable dimensionality metal–organic-framework lattices in binary/ternary Pb­(II)-(hydroxy-carboxylate) structures, based on which new Pb­(II) materials with distinct architecture and spectroscopic signature can be rationally designed and pursued synthetically