 Arene- and cyclopentadienyl complexes are kinetically inert platforms for the design of new radiopharmaceuticals.Furthermore, there have been made studies utilizing exogenous semi-synthetic ligands; specifically to the dopamine transporter, observing increased resultant efficacy in regard to reward facilitating behavior (incentive salience) and habituation, namely with the phenyltropane compound [η6-(2"β"-carbomethoxy-3"β"-phenyl)tropane]tricarbonylchromium.Carbon monoxide releasing organometallic compounds are also actively investigated, due to the importance of carbon monoxide as a gasotransmitter.