Syntheses, structures and photophysical properties of metal carbonyl clusters with dansyl and acridone luminophores

A series of fluorescent transition metal complexes bearing the 5-(dimethylamino)naphthalene-1-sulfonyl (R¹) and acridone (R²) frameworks have been prepared. Reactions of the fluorescent-labeled alkyne ligands R¹CH₂C≡CH and R²CH₂C≡CH with various metal carbonyl compounds [Co₂(CO)₈], [Et₃NH][Fe₂(CO)₆(μ-CO)(μ-StBu)] and [M₃(CO)₁₀(NCMe)₂] (M = Ru, Os) readily afforded new cluster complexes of the stoichiometry [Co₂(CO)₆(μ-η²-RCH₂CCH)] (1: R = R¹, 2: R²), [Fe₂(CO)₆(μ-StBu)(μ-η²- RCH₂C=CH₂)] (3: R = R¹, 4: R²), [Ru₃(CO)₉(μ-CO)(μ₃-η2- RCH₂CCH)] (5: R = R¹, 6: R²) and [Os₃(CO)₉(μ-CO)(μ₃- η²-RCH₂CCH)] (7: R = R¹, 8: R²) in moderate to good yields. All of these new complexes have been fully characterized by FTIR, ¹H NMR spectroscopy, UV/Vis spectroscopy and fast atom bombardment mass spectrometry (FABMS). The single-crystal X-ray structural analyses and molecular orbital calculations on 1, 2, 4 and 8 have been performed. It was found that all of these compounds are fluorescent in solutions at room temperature and a luminescence band characteristic of the inherent fluorophore is observed in these metal structures. However, a strong quenching of the fluorescence intensity of the chromophoric groups was observed upon coordination of metal cluster moieties.