A new imidazo[4,5-f]-1,10-phenanthroline ligand and its Pt(II), Ru(II) and Re(I) derivatives have been synthesized. It is shown that these metal complexes can be utilised as colorimetric and fluorescence chemosensors for anions. The interaction of these complexes with different anions has been characterised by UV/Vis absorption spectra, fluorescence spectra and titration studies. The results indicated that two of the three complexes showed selective recognition for F⁻, of which [Re(CO)₃ClL₁] showed an immediate change from yellow to pink when the fluoride anion was added in DMSO. The phenomenon could be observed with the naked eye. On the other hand, the emission intensities of [Ru(bpy)₂L₁](PF₆)₂ and [PtCl₂L₁] in DMSO were strongly enhanced upon the addition of F⁻.