OXYGEN‐INTERACTION LUMINESCENCE SPECTROSCOPY*

Abstract

Abstract— A new spectroscopic method has been developed in our laboratory for perturbation of singlet‐triplet transitions in organic molecules by O 2 . A dilute solution (10 ‐2 ‐10 ‐4 M ) of the molecule to be studied in various solvents is pressurized in a bomb with O 2 at 100 atm (10MPa) for 3–10h. The pressure is released, the solution pipetted into a sample tube, sealed, and frozen to a rigid glass state at 77 K. Then the luminescence spectra and excitation spectra of the sample are scanned. For benzene ‐O 2 we have evidence for a weak complex with a mild perturbation and a strong complex, with various new combination states. For the strong complex, the T 1 → S emission and excitation spectrum is observed, and also the T 2 ← S excitation spectrum. The T 1 → S emission for the benzene‐O 2 complex is seen as a highly resolved emission at 77 K in the glass solvent, but also at 298 K as a poorly resolved emission (induced triplet–triplet fluorescence in the complex). Various upconversion simultaneous transitions and downconversion simultaneous transitions are observed, e.g. ( 3 B lu + 1 Σ + g ), ( 3 B lu + 1 Δ g ) upconversions , and the ( 3 B lu + 1 Σ + g ), ( 3 B lu + 1 Δ g ) downconversions ; thus, in the latter, the third π, π* triplet is revealed for the first time. A novel structure for the benzene–O 2 strong complex is proposed as an anf jamel model. For pyridine –O 2 and perdeuteropyridine –O 2 we observe the T 1 → S emission for the first time; it is π, π* in character, analogous to benzene.