The present invention concerns compounds and methods of labeling peptides or other molecules with 18F or 19F or any other suitable radionuclide of use, for example, in PET or NMR in vivo imaging.A targeting molecule such as a protein or a peptide is linked to a substituted metallocene complex which is reacted with the 18F or 19F shortly before performing the PET or NMR in vivo imaging on the patient. The labeled molecule is then used for targeting a cell, tissue, organ or pathogen to be imaged or detected.