A persistent manganese carbonyl radical with infrared absorption and fluorescence modality

A manganese carbonyl radical complex, Cp∗Mn(CO)2(2-aminoanthracenyl) was prepared and characterised using IR, ESR and UV–visible absorption and emission spectroscopic methods. The radical persists in solution for more than one week and its ESR spectrum shows a sextet of lines which is consistent with a metal-centred radical complex. Two broad intense electronic absorption bands were observed, corresponding to the 2-aminoanthracene ligand-to-ligand transition (300–420 nm) and a ligand-to-metal charge transfer (LCMT) transition centred at 685 nm. Cp∗Mn(CO)2(2-aminoanthracenyl) exhibits fluorescence with a quantum yield of 0.6 and halflife of 6.4 ns upon excitation at 350 nm.