Two-Photon Photosensitized Production of Singlet Oxygen in Water

Abstract

Singlet molecular oxygen (a(1)Delta(g)) has been produced and optically detected in time-resolved experiments upon nonlinear two-photon excitation of a photosensitizer dissolved in water. For a given sensitizer, specific functional groups that impart water solubility and that give rise to larger two-photon absorption cross sections are, in many cases, not conducive to the production of singlet oxygen in high yield. This issue involves the competing influence of intramolecular charge transfer that can be pronounced in aqueous systems; more charge transfer in the chromophore facilitates two-photon absorption but decreases the singlet oxygen yield. This phenomenon is examined in a series of porphyrins and vinyl benzenes.

Singlet Oxygen in a Cell: Spatially Dependent Lifetimes and Quenching Rate Constants

“…35 The absorption spectrum of TMPyP, which is typical of porphyrins, is shown in Figure 2. Singlet oxygen can be produced upon irradiation into either the intense Soret band at ~ 420 nm or the weaker Q-band system over the range 500-600 nm.…”

Applying green chemistry to the photochemical route to artemisinin

“…This suggested that the reaction might perhaps be run in aqueous solvent mixtures, with corresponding benefits in the context of green chemistry. Even though reactions involving photochemically generated 1 O 2 in the presence of H 2 O have occasionally been reported, [32][33][34] the use of aqueous solutions in preparative photochemistry has been largely overlooked, probably because water and other protic solvents are excellent quenchers which reduce the lifetime of 1 O 2 . 35,36 With these facts in mind, the effect of the presence of 3 on the emission lifetimes of Conducting the photo-oxidation of 3 with O 2 (0.1 MPa) in mixtures of THF or EtOH with H 2 O and water-soluble photosensitizers confirmed this finding; indeed, the yields of 1 were similar to those obtained in DCM and in one case higher (see Table 2, entry 2).…”

3MLCT excited states in Ru(II) complexes: Reactivity and related two-photon absorption applications in the near-infrared spectral range

“…However, the currently used systems (porphyrins and tetrapyrroles) are poor two-photon absorbers [54] and only very few examples can be found in the literature. First attempts relied on the use of the meso-substituted and water-soluble porphyrins with two-photon absorption cross-section (s TPA ) of the order 100 Göppert-Mayer (1 GM ¼ 10 À50 cm 4 s photon À1 molecule À1 ) in the near infrared [55]. In order to increase s TPA values via antenna effect, these porphyrins have been incorporated into two-photon chromophore-based dendrimers.…”