Porphyrins. XXVII. Spin-orbit Coupling and Luminescence of Group IV Complexes
Gouterman, M., Schwarz, F.P., Smith, P.D., and David Dolphin
J. Chem. Phys.
Luminescence studies were reported on MX2 R (M = Si, Ge, Sn, Pb; X = F, Cl, Br, iodo, OH, benzoate; R = etioporphyrin or octaethylporphin). Fluorescence yields, phosphorescence yields, and phosphorescence lifetimes were determined. The contrasting vibronic envelopes of phosphorescence for octaethylporphin and tetraphenylporphin derivatives were attributed to transitions 3 Θ±1 → 1 ΘGND and 3 Θ±9 → 1 Θ ±GND (±1 and ±9 were pseudoangular momentum quantum numbers). The spin-orbit interaction was calculated by the extended Hueckel model; the ligands had more effect than the metal, in agreement with the data. However, a simple relation between decay rates and spin-orbit coupling failed quantitatively, and the extended Hueckel model exaggerated the contribution of the ligand to the spin-orbit coupling.