Ru(II)- and Os(II)-Induced Cycloisomerization of Phenol-Tethered Alkyne for Functional Chromene and Chromone Complexes

Diphosphine-containing
Ru­(II)/Os­(II)–chromene and −chromone
complexes were synthesized from reactions between phenol ynone HCC­(CO)­(o-C6H4OH) and cis-[Ru/Os­(dppm)2Cl2] (dppm = 1,1-bis­(diphenylphosphino)­methane).
The structures of these complexes in the solid state along with their
pH-dependent chromene/chromone equilibrium behavior in aqueous medium
were investigated. The cis–trans equilibration in solution demonstrated by chloride-ligated Ru–chromene
and −chromone series represents a rare example for Ru complexes
bearing dppm auxiliary ligands. More importantly, these metalated
chromene and chromone complexes exhibit moderate to strong cytotoxicity
against several human cancer cell lines and stronger antioxidative
activities in comparison with their organic counterpart. Overall,
these findings highlight the potential applications of metalated chromenes
and chromones as anticancer agents and antioxidants.