Switching on the Phosphorescence of Pyrene by Cycloplatination

1-Diphenylphosphinopyrene (1-PyP) and 1,6-bis(diphenylphosphino)pyrene (1,6-PyP) can be metalated at C5 and C10 to give cyclometalated complexes [M(L)(1-PyP-H)]+ and [M2(L)2(1,6-PyP)]2+ (M = Pd or Pt, L = diphosphines). The π → π* transitions of the pyrenyl ring are strongly perturbed by the PPh2 groups at C1/6, while the perturbation of the metal ions at C5/10 is weak. The phosphorescence of the pyrenyl ring is strongly enhanced by the heavy atom effect of the Pt ion up to a quantum yield of 1.5 × 10−2. Direct coordination of the Pt ion to the pyrenyl ring is needed for enhancement of the phosphorescence.