Spectroscopic properties of 2-phenylbenzothiazole and 1-phenylpyrazole luminophores metalated with platinum metals

The effect of metalation of 2-phenylbenzothiazole and 1-phenylpyrazole with Pd(II), Pt(II), and Rh(III) on the structure and optical properties of luminophore complexes is studied by 1H NMR spectroscopy, IR spectroscopy, and electronic absorption and emission spectroscopy. It is shown that metalation of luminophores leads to the formation of five-membered {M(C∧N)} fragments in the composition of square planar and octahedral complexes, which exhibit a long-wavelength charge-transfer band. The luminescence properties of the complexes are characterized by quenching of the fluorescence and by enhancement of the phosphorescence from the mainly intraligand excited state. Fluorescence quenching of complexes is attributed to the thermally activated energy transfer to metal-centered states and their efficient nonradiative decay.