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.