"Abstract A series of platinum(II) and palladium(II) complexes bearing N-heterocyclic carbene ligands functionalized by specific functionalities such as alcohol, nitrile or ester were synthesized. The novel complexes were fully characterized and X-ray diffraction was used for the structure determination of eight derivatives. The reactivity of the functional groups has been studied; for example, Pt and Pd \NHC\ complexes containing tBu ester functions were easily hydrolyzed giving water-soluble \NHC\ complexes. The palladium complex 21 containing dangling \COOH\ group was evaluated in copper-free Sonogashira coupling reaction. In addition, platinum \NHC\ complexes are attractive metal-based systems for the development of anticancer drugs. Preliminary results of the biological effects on various human cancer and non-cancer cells are also reported. "