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The Sensitivity of Structure to Ionic Radius and Reaction Stoichiometry: A Crystallographic Study of Metal Coordination and Hydrogen Bonding in Barbiturate Complexes of All Five Alkali Metals Li–Cs

Lookup NU author(s): Emeritus Professor Bill CleggORCiD, Gary Nichol

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Abstract

A systematic study has been conducted on barbiturate complexes of all five alkali metals, Li–Cs, prepared from metal carbonates or hydroxides in an aqueous solution without other potential ligands present, varying the stoichiometric ratio of metal ion to barbituric acid (BAH). Eight polymeric coordination compounds (two each for Na, K, and Rb and one each for Li and Cs) have been characterised by single-crystal X-ray diffraction. All contain some combination of barbiturate anion BA⁻ (necessarily in a 1:1 ratio with the metal cation M⁺ ), barbituric acid, and water. All organic species and water molecules are coordinated to the metal centres via oxygen atoms as either terminal or bridging ligands. Coordination numbers range from 4 (for the Li complex) to 8 (for the Cs complex). Extensive hydrogen bonding plays a significant role in all the crystal structures, almost all of which include pairs of N–H···O hydrogen bonds linking BA⁻ and/or BAH components into ribbons extending in one dimension. Factors influencing the structure adopted by each compound include cation size and reaction stoichiometry as well as hydrogen bonding.

Publication metadata

Author(s): Clegg W, Nichol GS

Publication type: Article

Publication status: Published

Journal: Molecules

Year: 2024

Volume: 29

Issue: 7

Online publication date: 27/03/2024

Acceptance date: 25/03/2024

Date deposited: 29/03/2024

ISSN (electronic): 1420-3049

Publisher: MDPI

URL: https://doi.org/10.3390/molecules29071495

DOI: 10.3390/molecules29071495

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