Polymorphism in [Co(SCN)4(ppz-H)2] (ppz, piperazine)

A one-pot reaction of [Co(NO3)2 · 6H2O and piperazine] with NH4SCN/NaSCN in water–methanol (1:1) solvent leads to two polymorphs of [Co(SCN)4(ppz-H)2] (ppz, piperazine) (I and II). X-ray crystal structure reveals both have same space group but the differences in the alignment of pendant SCN− leads to two polymorphs. In I, trifurcated N–H⋯S hydrogen bonding plays a prominent role in crystal packing leading to S⋯S interactions between SCN fragments but in II, no such trifurcation arises and thereby the crystal packing occurs through hydrogen bonding interactions only leading to a distinctly different network topology. TG/DSC and FT-IR study reveal they are enantiotropically related.

Graphical abstractA reactions of [Co(NO3)2 · 6H2O and piperazine (ppz)] with NH4SCN/NaSCN in water–methanol (1:1) solvent leads to two enantiotropically related polymorphs [(I) and (II)] of [Co(SCN)4(ppz-H)2].Figure optionsDownload full-size imageDownload as PowerPoint slide