Two new polymorphs of trans-bis(hinokitiolato)copper(II)

The title complex [systematic name: trans-bis(3-isopropyl-7-oxocyclohepta-1,3,5-trienolato)copper(II)], [Cu(C10H11O2)2], is a substance possessing antimicrobial activity. The compound crystallizes in a number of polymorphic forms, the structures for two of which are reported here. Stacks of square-planar molecules exhibiting weak intermolecular copper-olefin pi interactions (not observed in earlier reports on this substance) are described. The molecules have crystallographically imposed inversion symmetry, with stacking and copper-olefin pi distances ranging from 3.226 (2) to 3.336 (1) A.