Synthesis and Structures of Alkali Metal Complexes of Isophthalic Acid: The Interplay of Organic Supramolecular Interactions and Flexible Metal Coordination As Structure-Directing Factors

The supramolecular interactions of classical O-H center dot center dot center dot O hydrogen bonding and aromatic pi-pi stacking found in the crystal structure of isophthalic acid are retained, with minor modifications, in the structures of its complexes with lithium, sodium, rubidium, and cesium, where stacked hydrogen-bonded ribbons of partially deprotonated isophthalate anions are combined with alkali metal ion coordination. The coordination number increases as expected with cation size, from irregular tetrahedral for Li+, through a mixture of octahedral, trigonal prismatic, and irregular pentacoordinated for Na+, to cubic for Rb+ and Cs+. The arrangement of metal ions around the anions also varies considerably in these structures, despite the relative constancy of the arrangement of anions among themselves. The supramolecular properties of the acid thus have potential for design purposes in complexes of this type.