Antimony(V) and bismuth(V) complexes of lapachol: synthesis, crystal structure and cytotoxic activity.

Antimony(V) and bismuth(V) complexes of lapachol have been synthesized by the reaction of Ph₃SbCl₂ or Ph₃BiCl₂ with lapachol (Lp) and characterized by several physicochemical techniques such as IR, and NMR spectroscopy and X-ray crystallography. The compounds contain six-coordinated antimony and bismuth atoms. The antimony(V) complex is a monomeric derivative, (Lp)(Ph₃Sb)OH, and the bismuth(V) complex is a dinuclear compound bridged by an oxygen atom, (Lp)₂(Ph₃Bi)₂O. Both compounds inhibited the growth of a chronic myelogenous leukemia cell line and the complex of Bi(V) was about five times more active than free lapachol. This work provides a rare example of an organo-Bi(V) complex showing significant cytotoxic activity.