Abstract: The present invention relates to novel bifunctional chelates that are based on asymmetrical cyclen derivatives. The chelates contain either three acetates and one methylphosphonic arm or three acetates and one methylphosphonic arm enabling to link the chelate through P-alkyl within phosphoric acid derivative or through P—O-alkyl within phosphonic derivative to any organic back-bone suited for targeting. Suitable targeting moieties are monoclonal antibodies, their fragments and recombinant derivatives such as single chain antibodies, diabodies, triabodies, humanized, human or chimeric variants but also peptides, aptamers, spiegelmers, nucleotides, anti sense oligomers and conventional small molecules. These novel bifunctional chelates are suited for the production of kits for the routine labelling of targeting moieties to be used in radiotherapy with radiometals such as Yttrium-90, or for Magnetic Resonance Imagining (MRI) using Gadolinium.