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

Hydrothermal pH-specific reactivity in the binary/ternary
systems of Pb­(II) with the carboxylic acids N-hydroxyethyl-iminodiacetic
acid (Heida), 1,3-diamino-2-hydroxypropane-N,N,N′,N′-tetraacetic
acid (Dpot), and 1,10-phenanthroline (Phen) afforded the new well-defined
crystalline compounds [Pb­(Heida)]n·nH2O­(1), [Pb­(Phen)­(Heida)]·4H2O­(2), and [Pb3(NO3)­(Dpot)]n(3). All compounds were characterized
by elemental analysis, FT-IR, solution or/and solid-state NMR, and
single-crystal X-ray diffraction. The structures in 1–2 reveal the presence of a Pb­(II) center coordinated
to one Heida ligand, with 1 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 2 projects the significance
of nature and reactivity potential of N-aromatic chelators, disrupting
the binary lattice in 1 and influencing the nature of
the ultimately arising ternary 3D lattice. 3 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 1–3 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.