Molecular tuning of phenylene-vinylene derivatives for two-photon photosensitized singlet oxygen production

Article abstract of DOI:10.1021/jo9020216

(Chemical Equation Presented) Substituent-dependent features and properties of the sensitizer play an important role in the photosensitized production of singlet oxygen, O₂(a¹Δ_g). In this work, we systematically examine the effect of molecular changes in the sensitizer on the efficiency of singlet oxygen production using, as the sensitizer, oligophenylene-vinylene derivatives designed to optimally absorb light in a nonlinear two-photon process. We demonstrate that one cannot always rely on rule-of-thumb guidelines when attempting to construct efficient two-photon singlet oxygen sensitizers. Rather, as a consequence of behavior that can deviate from the norm, a full investigation of the photophysical properties of the system is generally required. For example, it is acknowledged that the introduction of a ketone moiety to the sensitizer chromophore often results in more efficient production of singlet oxygen. However, we show here that the introduction of a carbonyl into a given phenylene-vinylene can, rather, have adverse effects on the yield of singlet oxygen produced. Using these molecules, we show that care must also be exercised when using qualitative symmetry-derived arguments to predict the relationship between one-and two-photon absorption spectra.