Luminescence behavior of the pyridine—BCl3 complex

A phosphorescence and CNDO study of the 1:1 electron donor-acceptor complex formed between pyridine and boron trichloride has been shown to account satisfactorily for the electronic states and induced luminescence of pyridine resulting from complexation. The phosphorescence yield and formation constant of the complex in ethyl alcohol were determined to be 0.38 ± 0.04 and 1.3 × 10⁴ M⁻¹ respectively. CNDO calculations show that the lowest n,π* levels are shifted to significantly higher energies, thereby removing efficient radiationless decay routes available with these states.