Two-photon ionisation of the antitumor drug pazelliptine (BD40) by 355 nm laser photolysis

Abstract The effect of 2 ns pulses of 355 nm laser light on aqueous solutions of pazelliptine (PZE) was investigated and biphotonic ionization was observed. The absorption spectrum corresponding to the pazelliptine radical cation (PZE ·+ ) and the hydrated electron simultaneously formed in this process was determined. In the absence of oxygen, e aq − reacted with unexcited PZE ( k = 1.6 × 10 10 M −1 s −1 ) to give the pazelliptine radical anion (PZE ·− ). This latter species was identified by separate pulse radiolysis experiments. The radicals cation and anion disappeared by recombination on the millisecond time range. In presence of oxygen, e aq − was scavenged by O 2 leading to the formation of the superoxide radical (O 2 ·− ) in competition to the formation of the radical PZE ·− . PZE ·+ reacted with O 2 ·− to produce H 2 O 2 ( k =9x10 9 M −1 s −1 ). The spectral analysis revealed that PZE triplet was also formed during the laser pulse. In the absence of oxygen, the triplet-triplet absorption decreased on the μs time scale (2 k = 1.5 x 10 10 M −1 s −1 ). In oxygenated solutions, e aq − and the pazelliptine triplet decayed exponentially in the same time range.