Aimed at finding complexes of the same family with improved bone-seeking properties and adequate tumor cell uptake profile, we have synthesized novel complexes of the type fac-[M(CO)3(k3-L)]+ (M = 99mTc/Re, Tc3/Re3–Tc5/Re5) stabilized by bifunctionalchelators with different molecular weight, overall charge, (lipo)hydrophilic nature and different positions of BP attachment. Biodistribution studies in