Structure and solvent-induced tuning of laser property and photostability of a boradiazaindacene (BODIPY) dye

- Highly lasing efficient B-substituted BODIPY laser dye was synthesized.
- The BODIPY dye was 34 times more photostable in non-polar 1,4-dioxane solvents than in polar ethanol.
- High photostability of the BODIPY dye in non-polar solvent is due to its lower reactivity with 1O2.
- Rationalization of the results was done by theoretical calculations.
- The photostability of the new BODIPY dye in 1,4-dioxane is comparable to that of Rhodamine 6G in ethanol.

Boradiazaindacene (BODIPY) class of laser dyes are highly efficient but degrade rapidly in alcohol solution during lasing action, progressively reducing output power. Photodegradation of these dyes is mainly due to reaction with the in situ generated singlet oxygen (1O2). With the aim to increase the lasing lifetimes of these dyes, we have designed and synthesized a new congener of the widely used BODIPY dye (PM567) by substitution at its B-centre. The new dye was highly fluorescent, and showed comparable lasing efficiency, but better photostability relative to PM567 in both polar (ethanol) and non-polar (1,4-dioxane) solvents, when excited by 2nd harmonic (532 nm) of a pulsed Nd-YAG laser. More interestingly, the lasing efficiency and photostability of both the dyes were much better in 1,4-dioxane than in ethanol. The relative photostabilities of the dyes were rationalized by absorption spectroscopic analyses of their triplet state properties in the respective solvents in the presence of a 1O2 generator or quencher as an additive, pulse radiolysis studies and quantum chemical calculations.

Enhancement of photostability of BODIPY dye based on changes in its structure in conjunction with solvent polarity.79