New tripodal uranyl ion chelators containing gem-bisphosphonic units have been synthesized. All bisphosphonic units present a side chain with 0, 1, or 2 methylene group terminated by -NH2 or -COd(2)H group. These units were respectively coupled with a -CO2H or -NH2 functions of a suitable tri-functional platform. The shape and size of the new designed ligands were selected and validated through computer molecular modelization. (c) 2007 Elsevier Ltd. All rights reserved.