In our search for efficient and photostable laser dyes, four new dyes with the basic structure of the
commercial BODIPY laser dye PM567, with either an 8-diphenylene or an 8-p-triphenylene group,
both substituted at the terminal polyphenylene position with an acetoxymethyl (dyes P2Ar1Ac and
P3Ar1Ac, respectively) or a methacryloyloxymethyl group (dyes P2Ar1MA and P3Ar1MA,
respectively), have been synthesized. The photophysical and lasing properties of the dyes have been
studied both dissolved in liquid solvents (acetoxymethyl dyes) and incorporated into solid polymeric
matrices, in the latter case as solutions (acetoxymethyl dyes) or as copolymers with methyl methacrylate
(methacryloyloxymethyl dyes). In liquid solution, the photophysics of P2Ar1Ac and P3Ar1Ac is
scarcely affected by the number (two or three) of p-phenylene units. Quantum mechanical calculations
reveal that the p-phenylene units in these dyes are twisted ca. 37◦ each other, an that the first
8-p-phenylene group stands nearly perpendicular to the aromatic BODIPY plane, resulting in electronic
decoupling of the two chromophores. P2Ar1Ac exhibits a somewhat lower photodegradation quantum
yield under UV and visible irradiation, if compared with P3Ar1Ac or with PM567, likely because of its
also lower rate constant for the reaction with in situ-generated singlet molecular oxygen. Both
acetoxymethyl dyes emit laser radiation in solution in all the solvents tried, under transversal pumping
at 532 nm. In ethyl acetate, with a dye concentration of 0.80 × 10−3 M, laser efficiencies as high as 80%
have been observed. When the 8-polyphenylene dyes were incorporated into solid poly(methyl
methacrylate) (PMMA) matrices, as solutions or as copolymers, the fluorescence emission increased
with respect to that of the parent PM567 dye dissolved in the same matrix, and lasing efficiencies in the
range 18–31% were obtained, with good photostability. The dye P2Ar1Ac dissolved in PMMA was
found to exhibit the best overall laser behavior, with a good balance between efficiency and
photostability.This work was supported by Project MAT2004-04643-C03-01 of
the Spanish CICYT. M. Liras thanks Comunidad Aut´onoma
de Madrid for a predoctoral scholarship and Ministerio de
Educaci´on y Ciencia for a Juan de la Cierva contract.M. A´ lvarez
thanks Ministerio de Educaci´on y Ciencia for a predoctoral scholarship.
The 8-polyphenylene-substituted boron-dipyrromethene
dyes described in this paper and their utilization in liquid and solidstate
dye lasers are covered by Spanish PatentNo. P200701763 filed
on 25 June 2007.Peer reviewe
