Acta Crystallogr B Struct Sci Cryst Eng Mater. 2014 Feb;70:132-40. doi: 10.1107/S2052520613026036. Epub 2013 Dec 10.

Creation of a ternary complex between a crown ether, 4-aminobenzoic acid and 3,5-dinitrobenzoic acid.

Acta crystallographica Section B, Structural science, crystal engineering and materials

Nicole D Boardman, Tasnim Munshi, Ian J Scowen, Colin C Seaton

PMID: 24441136 DOI: 10.1107/S2052520613026036

Abstract

The creation of ternary multi-component crystals through the introduction of 18-crown-6 to direct the hydrogen-bonding motifs of the other molecular components was investigated for 3,5-dinitrobenzoic acid (3,5-dnba) with 4-aminobenzoic acid (4-aba). The creation of a binary complex between 18-crown-6 and 4-aba (C12H24O6·2C7H7NO2)2 and a ternary salt between 3,5-dnba, 18-crown-6 and 4-aba (C12H24O6·C7H8NO2(+)·C7H3N2O6(-)·C7H4N2O6) were confirmed by single-crystal structure determination. In both structures, the amino molecules bind to the crown ether through N-H...O hydrogen bonds, leaving available only a single O atom site on the crown with restricted geometry to potentially accept a hydrogen bond from 3,5-dnba. While 3,5-dnba and 4-aba form a binary co-crystal containing neutral molecules, the shape-selective nature of 18-crown-6 preferentially binds protonated amino molecules, thereby leading to the formation of the ternary salt, despite the predicted low concentration of the protonated species in the crystallizing solution. Thus, through the choice of crown ether it may be possible to control both location and nature of the available bonding sites for the designed creation of ternary crystals.

Keywords: co-crystals; crown ethers; crystal engineering; salts

Publication Types

• Journal Article
• Research Support, Non-U.S. Gov't