Crystal engineering of chiral superstructures based on (R)-(+)-1,1′-bi-2-naphthol and the alkali derivatives of racemic (R,S)-1,1′-bi-2-naphthol

New Journal of Chemistry Pub Date: 2001-04-18 DOI: 10.1039/B009665M

Abstract

(R)-(+)-1,1′-Bi-2-naphthol [(R)-(+)-(HOC10H6C10H6OH)] has been used as a chiral building block in the construction of chiral organo-organometallic crystals. The reaction of the neutral molecule with [Co(η5-C5H5)2] in diethyl ether yields the supramolecular salts [CoIII(η5-C5H5)2][(R)-(+)-(HOC10H6C10H6O)]·[(R)-(+)-(HOC10H6C10H6OH)] (1) and [CoIII(η5-C5H5)2][(R)-(+)-(HOC10H6C10H6O)]·[(R)-(+)-(HOC10H6C10H6OH)]0.5 (2), depending on the stoichiometric ratios between the binaphthol and the organometallic sandwich compound. Molecular aggregation is achieved [italic v (to differentiate from Times ital nu)]ia a combination of neutral and charge-assisted O–H···O bonds between the binaphthol and binaphtholate components and [italic v (to differentiate from Times ital nu)]ia weaker interactions of the C–H···O and C–H···π types involving the [CoIII(η5-C5H5)2]+ cation. The same reaction with racemic 1,1′-bi-2-naphthol in diethyl ether, followed by recrystallisation from nitromethane, yields the solvate species [CoIII(η5-C5H5)2][(R,S)-(HOC10H6C10H6O)]·[(R,S)-(HOC10H6C10H6OH)][MeNO2]1.5 (3). For comparison, the alkali salts Cs[(R,S)-(HOC10H6C10H6O)]·[(R,S)-(HOC10H6C10H6OH)] (4) and Rb[(R,S)-(HOC10H6C10H6O)]· [(R,S)-(HOC10H6C10H6OH)] (5) have also been prepared by treating [(R,S)-(HOC10H6C10H6OH)] with the Cs and Rb hydroxides. Both organometallic and alkali salts show how the cations tend to be encapsulated within a niche formed by the folding of hydrogen-bonded naphthol–naphtholate chains.

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