Reinvestigation of growth of 2-aminopyridine bis thiourea zinc sulphate single crystal

In an earlier published paper, Srineevasan and Rajasekaran (J. Mol. Struc. 1048, (2013) 238-243) [1 reported to have grown a so called 2-aminopyridine bis thiourea zinc sulphate single crystal (1) by slow evaporation technique at room temperature. A reinvestigation of the reported crystal growth reaction reveals that addition of 2-aminopyridine into an aqueous solution containing zinc sulphate heptahydrate and thiourea in 1:2 mol ratio initially results in the formation of a white precipitate. Filtration of the precipitate followed by slow evaporation of the filtrate results in the crystallization of the known compound sulphatotris(thiourea)zinc(II) (2) and NOT any 2-aminopyridine bis thiourea zinc sulphate. (C) 2019 Elsevier B.V. All rights reserved.