Tuning the structural motif by tuning the countercation size: from double salts to a 1-D coordination polymer

Abstract

By increasing the size of the alkylammonium countercation, it is possible to tune the reaction product obtained from a mixture of cobalt sulfate, citric acid and tetraalkylammonium hydroxide in aqueous solution at pH = 6; products range from a double salt [NR₄]₂[Co(H₂O)₆][SO₄]₂·4H₂O containing water hexamers (R = Me) or 1-D water chains (R = Et) to a new cobalt(II) citrate 1-D coordination polymer [NBu₄]₂[Co₂(Hcit)₂(H₂O)₄]·4H₂O. Increasing the size of the cation results in a corresponding decrease in the dimensionality of the water motifs, from a 3-D network when R = Me, to a 2-D lattice when R = Et and a 1-D lattice when R = Bu.