Acid–base properties of disodium 3,3′-disulfonatobenzophenone (DSB) in the ground and excited states
Abstract
The photophysical parameters of the DSB–DSBH+ system have been determined using absorption and emission stationary and pulsed techniques. Only the neutral form was found to emit room-temperature phosphorescence with a quantum yield of 6 × 10–2 and a lifetime on the microsecond scale. These parameters were found to decrease with increasing DSB concentration and decreasing pH, owing to self-quenching (ksq= 8.4 × 106 dm3 mol–1 s–1) and interaction with the proton. The triplet state pK*(–0.7), determined from T1→ So phosphorescence titration and T1→ Tn absorption titration, indicated a marked increase in basicity of DSB upon excitation (ground-state pK=–6.6).