Novel Blue Phosphorescent Group 15 Compounds MR₃ (M = P, Sb, Bi; R = p-(N-7-Azaindolyl)phenyl)

New blue phosphorescent organometallic compounds of group 15, M[p-C₆H₄(N-7-azain)]₃ with M = P (1), Sb (2), Bi (3) and 7-azain = 7-azaindolyl, have been synthesized from the reaction of MCl₃ with Li[p-C₆H₄(N-7-azain)]. The crystal structures of these new compounds have been determined by single-crystal X-ray diffraction, which revealed that the group 15 elements in all three complexes are in a trigonal-pyramidal environment with the bond angles of C−M−C around the central atom decreasing from 1 to 3, attributed to the diminution of s character of the M−C bond and the size increase of the central atom. All three compounds are blue luminescent. Both fluorescent and phosphorescent emissions (λ_max = 371 nm, λ_max = 488 nm) were observed for compound 1 at 77 K. In contrast, at 77 K, only phosphorescence was observed for compounds 2 and 3 (λ_max = 483 nm for 2; λ_max = 478 nm for 3), attributable to the increased heavy-atom effects. Experimental data and molecular orbital calculations (restricted Hartree−Fock methods) support the view that luminescences from all three compounds are ligand-based emissions with contributions from the lone-pair electrons of the central atom. The orange Bi(V) compound Bi[p-C₆H₄(N-7-azain)]₃Cl₂ (4) was obtained by the oxidation of 3 with PhI·Cl₂. Compound 4 displays a distorted-trigonal-bipyramidal structure and a weak phosphorescence at λ_max = 510 nm at 77 K, which is most likely caused by charge-transfer transitions from the chloride ligand to the Bi(V) center.