A new 9-diphenylphosphinophenanthrene ligand (9DPP, 1), its oxide (9DPPO, 2), and its gold complex [(AuCl(9DPP)] (3) were synthesized. The Au(I) complex 3 was found to exhibit intense blue-green, room-temperature phosphorescence (Phi(p) = 0.06 and tau(T) = 22.7 mus) originating in the locally excited triplet of the phenanthrene moiety ((LE)-L-3) in degassed 2-methyltetrahydrofuran solution. On the assumption that Phi(ST) = 1.0 for 3, the radiative rate constant (k(r)) in the triplet state is calculated to be 2.6 x 10(3) s(-1). This value is 4 orders of magnitude larger than the radiative rate constant of the triplet phenanthrene (0.26 s(-1)). Thus, the coordinated Au(I) atom is concluded to have a markedly large heavy-atom effect on k(r) of the phenanthrene chromophore in 3.