One and two photon fluorescent complexes of rhenium and their technetium analogues.

The synthesis of rhenium and 99m-technetium complexes of dipyrazolemethanecarboxylates directly from the tetroxometallates is reported together with a 'one pot' synthesis of mixed ligand M(V) complexes. The rhenium complexes in all three oxidation states show strong fluorescence when the pyrazole groups have aromatic substituents with emission around 330 nm with both one and two photon excitation. The emission lifetimes of the complexes and free ligands differ considerably.