Cyclopalladated complexes of 2-phenylbenzothiazole with 4,4′-bipyridyl

Complexes [Pd(bt)(4,4′-bpy)OOCCH3], [Pd(bt)NO3]2(m-4,4′-bpy), [Pd(bt)(m-4,4′-bpy)]4(NO3)4 (bt− is deprotonated form of 2-phenylbenzothiazole, bpy is 4,4′-bipyridyl) are prepared and characterized by 1H NMR, electron absorption and emission spectroscopy, as well as by voltammetry. The upfield shift of the signal of proton in the ortho-position to the donor carbon atom of the cyclopalladated ligand in the complexes [(Δδ = −(1.1–1.5) ppm] is assigned to the anisotropic effect of the ring current of the pyridine rings of the 4,4′-bipyridyl moiety, which are orthogonal to the coordination plane. Characteristic longwave absorption bands λ = (387±4) nm and the low-temperature phosphorescence bands λ = (512±3) nm in the complexes are assigned to the chromophore {Pd(bt)} metal complex fragment. The reduction waves in the complexes [E1/2 = −(1.54±0.04) and Ep = −(1.83±0.03) V] are assigned to the ligand-centered processes of the successive electron transfer to the π* orbitals localized predominantly on the coordinated pyridine components of the 4,4′-bipyridyl moiety.