8-Phenyl-Substituted Dipyrromethene·Bf2 Complexes as Highly Efficient and Photostable Laser Dyes

Article abstract of DOI:10.1021/jp0312464

We report on the synthesis and the photophysical and lasing properties of two new dipyrromethene·BF₂ dyes, analogues of the commercial dye PM567, dissolved in liquid solutions or in polymeric matrices of poly(methyl methacrylate) and as solid c

Full text of DOI:10.1021/jp0312464

J. Phys. Chem. A 2004, 108, 3315-3323
3315
8
-Phenyl-Substituted Dipyrromethene‚BF2 Complexes as Highly Efficient and Photostable
Laser Dyes
I. Garc ´ı a-Moreno,* A. Costela, and L. Campo
Instituto de Qu ´ı mica-F ´ı sica “Rocasolano”, C.S.I.C., Serrano 119, 28006 Madrid, Spain
R. Sastre
Instituto de Ciencia y Tecnolog ´ı a de Pol ´ı meros, C.S.I.C., Juan de la CierVa 3, 28006 Madrid, Spain
F. Amat-Guerri and M. Liras
Instituto de Qu ´ı mica Org a´ nica, C.S.I.C., Juan de la CierVa 3, 28006 Madrid, Spain
F. L o´ pez Arbeloa, J. Ba n˜ uelos Prieto, and I. L o´ pez Arbeloa
Departamento de Qu ´ı mica-F ´ı sica, UPV-EHU, Apartado 644, 48080 Bilbao, Spain
ReceiVed: NoVember 13, 2003
We report on the synthesis and the photophysical and lasing properties of two new dipyrromethene‚BF
2
dyes, analogues of the commercial dye PM567, dissolved in liquid solutions or in polymeric matrices of
poly(methyl methacrylate) and as solid copolymers with methyl methacrylate, where the chromophore is
covalently bound to the polymeric chains. The new dyes have the 8 position substituted by the group
p-(acetoxypolymethylene)phenyl or p-(methacryloyloxypolymethylene)phenyl (number of methylenes ) 1
or 3). Good correlations between the photophysical properties in dilute solutions and the lasing characteristics
in moderately concentrated solutions have been observed. The presence of the 8-phenyl substituent does not
significantly modify the photophysics of the chromophore. Theoretical calculations were performed to
rationalize this behavior. Under transversal pumping at 534 nm, laser efficiencies up to 46% were obtained
for liquid solutions, which were found to be nearly independent of the nature of the solvent and the length
of the polymethylene chain. For solid samples, lasing efficiencies of up to 23% and good photostabilities,
with 96% of the initial laser output after 100 000 pump pulses at 10 Hz, were established.
I. Introduction
SCHEME 1: Molecular Structures of the PM567 Dye
and the PnAc and PnMA Analogues
As a result of the continuous effort to produce improved dyes
for laser applications, in the late 1980s Pavlopoulos, Boyer, and
co-workers developed the dipyrromethene‚BF2 (P‚BF2) dyes.
This new family of dyes promised enhanced lasing efficiency
and photostability1 because they exhibited high fluorescence
quantum yields owing to their low triplet (T-T) absorption
losses at the fluorescence emission wavelengths.7 However,
when reviewing the spectroscopic and photochemical parameters
of the P‚BF2 complexes, one concludes that these dyes are not
yet the ultimate high-efficiency and photostable laser dyes
because they are not stable enough for the required uses and
-6
,8
studied the effect of introducing a number of substitutions at
the 8 position of this molecule while maintaining the four methyl
9
are particularly sensitive to photoreactions with oxygen. In
trying to improve the lasing performance of these dyes, recent
studies have demonstrated that adequate substituents in the
molecular core can enhance the laser action.10
groups in the 1, 3, 5, and 7 positions and the ethyl groups in
13-16
positions 2 and 6.
The presence of an 8-(ω-acetoxy)-
polymethylene or an 8-(ω-methacryloyloxy)polymethylene sub-
stituent (dyes PnAc and PnMA, respectively; Scheme 1) does
not significantly modify the photophysics of the chromophore
with regard to that of PM567, especially if the linear polym-
Special attention has been paid to the dye 1,3,5,7,8-pentam-
ethyl-2,6-diethyl dipyrromethene‚BF2 (PM567, Scheme 1)
because of the simplicity of its chemical structure and its good
1
1,12
14
laser performance in both the liquid and solid state.
The
ethylene chain has five or more methylene groups. These new
photophysical behavior and the photochemical stability of this
dye can be modulated by changes in the substitution pattern on
the tricyclic ring system. Over the last few years, we have
dyes, when dissolved in a variety of organic solvents, lased more
efficiently than PM567 and, under continuous UV irradiation,
1
3,15
demostrated improved photostability.
In addition, these
newly synthesized analogues of PM567, either dissolved in poly-
(methyl methacrylate) (PMMA) or covalently bound to methyl
*
Corresponding author. E-mail: iqrfm84@iqfr.csic.es.
1
0.1021/jp0312464 CCC: $27.50 © 2004 American Chemical Society
Published on Web 03/24/2004

3316 J. Phys. Chem. A, Vol. 108, No. 16, 2004
Garc ´ı a-Moreno et al.
SCHEME 2: Synthesis of the New Dipyrromethene‚BF2
we have proceeded to characterize properly the photophysical
and lasing properties of these new dyes in air-equilibrated liquid
solutions of apolar, polar nonprotic, and polar protic solvents,
paying attention to the effect of the dye concentration. To gain
deeper insight into the characteristics of these high-emitting
dyes, we have also studied their properties in the solid state
either by the copolymerization of PArnMA monomers with
MMA, yielding solid copolymers COP(PArnMA-MMA) where
the covalently bound chromophore is separated from the
polymeric chain by a polymethylenephenyl group, or simply
by dissolving the PArnAc model dyes into PMMA, rendering
materials named PArnAc/PMMA.
Dyes PArnAc and PArnMAa
II. Experiment
Materials. PM567 (laser grade, from Exciton) was used as
received. The purity of the dye was found to be >99%, as
determined by spectroscopic and chromatographic methods. All
solvents (Merck, Aldrich, or Sigma) were spectroscopic grade
and were used without further purification. Methyl methacrylate
(MMA, Aldrich, 99% purity) was successively washed with 5%
NaOH in water and pure water and then dried over Na2SO4
and distilled under reduced pressure. 2,2′-Azobis(isobutyroni-
trile) (AIBN, from Merck) was crystallized in the dark from
methanol. Chemicals were purchased from Aldrich and were
used without further purification. p-(3-Bromopropyl)benzoyl
chloride was obtained in three steps from (1) the 1-bromo-3-
phenylpropane (25 mmol) reaction with acetyl chloride to yield
a
Conditions: (i) CH
2
Cl
2
, Ar, 50 °C, 2 h; (ii) Et
3
N, MePh-CH
‚Et O, 50 °C, 1.5
dC(Me)CO K (for
2 2
Cl ,
9
5:5, Ar, room temperature, 30 min, followed by BF
h; (iii) MeCO Na (for PArnAc dyes) or CH
PArnMA dyes), DMF, Ar, 1-20 h.
3
3
2
2
2
methacrylate (MMA), lased more efficiently than the parent dye
PM567 incorporated into PMMA. Once more, the photophysical
properties of PM567 were not significantly modified by the
18
p-(3-bromopropyl)acetophenone (yield 90%); (2) the conver-
sion of this acetophenone into p-(3-bromopropyl)benzoic acid
substituents, except that the fluorescence quantum yield of some
1
9,20
solid samples increased to up to 0.89.16
with Br2/NaOH (yield 64%);
and (3) the treatment of the
resulting carboxylic acid with thionyl chloride.
In light of the former results, the question that arises is
whether the presence of other 8-substituent groups in the PM567
chromophore core, such as a phenyl group, could enhance its
photophysical properties and lasing performance in both liquid
and solid phases. Initially, we speculated that an 8-phenyl-
substituted molecular structure might be less sensitive to
chemical reactions with oxygen. This fact, together with the
ability of this structure to modify the degree of polarization
under excitation, which facilitates the dissipation of the absorbed
energy not converted into emission, should render more pho-
tostable dyes that are valuable for solid-state lasers.
The photophysical properties of some 8-phenyl P‚BF2 dyes
previously described in the literature are controversial. Pav-
lopoulos et al. synthesized the 1,3,5,7-tetramethyl-8-(p-meth-
oxy)phenyl-P‚BF2 dye and concluded that this substitution does
not result in any significant improvement of the laser action
properties because it brings a blue shift as well as an intensifica-
tion of the T-T absorption over the fluorescence spectral
Synthesis of Precursors PAr1Cl and PAr3Br. p-(Chlo-
romethyl)benzoyl chloride (1.5 g, 8 mmol) or p-(3-bromopro-
pyl)benzoyl chloride (2.1 g, 8 mmol), respectively, was added
dropwise to a stirred solution of freshly distilled 2,4-dimethyl-
3
-ethylpyrrole (2.2 mL) in dichloromethane (90 mL) at room
temperature and under Ar, and the mixture was heated to 50°
with stirring for 2 h. After the vacuum evaporation of the
solvent, toluene (190 mL), dichloromethane (10 mL), and
triethylamine (3.88 g, 38 mmol) were added to the residual solid,
the mixture was stirred at room temperature for 30 min under
Ar, and boron trifuoride diethyl etherate (7.82 g, 55 mmol) was
then added. After heating to 50° for 1.5 h, the subsequent
workup yielded a residue that was purified by column chro-
matography (silica gel, hexanes-EtOAc mixtures as eluents)
and crystallization from hexane at -78 °C. For data, see the
Appendix.
Synthesis of Models PArnAc and Monomers PArnMA.
A solution of sodium acetate (1 mmol) or potassium methacry-
late (1 mmol) and PAr1Cl (0.25 mmol) or PAr3Br (0.25 mmol)
in DMF (30 mL) was stirred at room temperature for 5-7 days
or at 40 °C for 1-20 h under an Ar atmosphere and in the
dark. The subsequent workup yielded a residue that was purified
by column chromatography (silica gel, hexanes-EtOAc 98:2
to 80:20) and crystallization from hexane at -78 °C. For data,
see the Appendix.
7
region. Recently, Liang et al. reported the spectroscopic and
laser action properties of three 1,3,5,7-tetramethyl-2,6-diethyl-
P‚BF2 dyes with phenyl, p-methoxyphenyl, and p-fluorophenyl
substituents at the 8 position.17 They concluded that their
corresponding T-T absorption values are rather low over their
fluorescence spectral regions and that they, along with their high
fluorescence quantum yields, are the main factors that enable
these laser dyes to perform efficiently.
To develop improved laser dyes and in an attempt to clarify
this controversy, we have synthesized new P‚BF2 dyes with the
same substituents as PM567 in positions 1 to 7 but containing
at position 8 a p-(acetoxypolymethylene)phenyl group with 1
or 3 methylene groups (dyes PArnAc, Scheme 2) or a p-
Preparation of Solid Polymeric Samples. The dyes were
incorporated into solid matrices of methyl methacrylate (MMA)
following the procedure previously described.
Laser Experiments. Liquid solutions of dyes were contained
in 1-cm optical-path quartz cells that were carefully sealed to
avoid solvent evaporation during the experiments. The solid
samples for laser experiments were cast in a cylindrical shape,
forming rods of 10-mm diameter and 10-mm length. A cut was
1
5
(
methacryloyloxypolymethylene)phenyl group with the same
number of methylenes (dyes PArnMA). The PArnAc dyes are
model compounds of the PArnMA monomers. In this paper,

8-Phenyl-Substituted Dipyrromethene‚BF2 Complexes
J. Phys. Chem. A, Vol. 108, No. 16, 2004 3317
made parallel to the axis of the cylinder to obtain a lateral flat
2
surface of ca. 4 × 10 mm . This surface was prepared for lasing
experiments by conventional grinding and polishing. The ends
of the laser rods were also hand-polished to an optical-grade
finish. The samples were transversely pumped at 534 nm with
5.5-mJ, 6-ns fwhm pulses from a frequency-doubled Q-switched
Nd:KGW laser (Monocrom STR-2+) at a repetition rate of up
to 10 Hz. Details of the experimental system can be found
2
1
elsewhere.
Photophysical Properties. Photophysical properties of dilute
-6
solutions (2 × 10 M) were measured in 1-cm optical path
length quartz cuvettes. Fluorescence quantum yields (φ) were
determined using a dilute solution of PM567 in methanol as a
reference (φ ) 0.91).22 The fluorescence decay curves were
Figure 1. Absorption and corrected fluorescence spectra of dilute
2
analyzed as monoexponentials (ø < 1.3), and the fluorescence
-6
solutions (2 × 10 M) of (a) PAr3Ac and (b) PAr1Ac dyes in ethanol.
decay time (τ) was obtained from the slope.
The absorption spectrum of PM567 in ethanol (- - -) is also included
for comparison.
-
3
For concentrated solutions (up to 10 M), 0.01- and 0.001-
cm path length cuvettes were employed, and to reduce the
reabsorption and reemission effects,23 the emission signals were
recorded in the front-face configuration, orientating the cuvette
3
5 and 55° with respect to the excitation and emission beams,
respectively. Samples in 0.001-cm cuvettes were carefully
manipulated to avoid solvent evaporation and to get reproducible
fluorescence intensities. Indeed, the reported fluorescence
quantum yields are always the average of at least three
independent measurements.
Photophysical properties of solid polymeric samples were
measured from disk-shaped samples with a thickness of 0.2 mm
-
3
and a dye concentration of 1.5 × 10 M. Absorption was
registered in transmittance, and fluorescence measurements were
recorded by employing the above-mentioned front-face setup.
Fluorescence quantum yields were determined by using a solid
disk of the dye PM567 in a copolymer of trifluoromethyl
2
4
methacrylate (30%) and methyl methacrylate (70%) as a
reference. All measurements were performed at 20 ( 0.2 °C.
Theoretical Calculations. These were performed with the
MOPAC 2000 (Fujitsu) method. The semiempirical AM1
method was recommended for the geometry optimization of the
dyes instead of the more commonly used semiempirical PM3
method because of the unsatisfactory parametrization of the
boron atom in the latter method.
Figure 2. Fluorescence decay curves of (A) PAr1Ac in dilute solution
2
in acetone, analyzed as a one exponential (τ ) 4.82 ns with ø ) 1.14),
and (B) COP(PAr1MA-MMA) analyzed as growing (τ ) 3.88 ns)
1
2
and decaying (τ ) 11.35 ns) (ø ) 1.01).
2
ties of P‚BF2 dyes and rule out any possible intramolecular
interaction between the π electrons of the phenyl group and
the P‚BF2 chromophoric core affecting their photophysics.26
Theoretical calculations corroborate this assumption. Figure 3
shows the geometry of the ground state of the PAr3Ac dye
optimized by the AM1 semiempirical method in which the
phenyl ring is in a nearly perpendicular conformation with
respect to the boron-dipyrromethene plane. Experimental data
obtained by single-crystal X-ray diffraction confirm this geom-
III. Results and Discussion
Photophysical Properties in the Liquid Phase. The pho-
tophysical characteristics of the new dyes in liquid solution were
studied in polar protic (2,2,2-trifluoroethanol, ethanol, and
methanol), polar nonprotic (acetone and ethyl acetate), and
apolar (cyclohexane) solvents. The absorption and fluorescence
spectra of dyes PAr1Ac and PAr3Ac in ethanol solution are
shown in Figure 1, where the absorption spectrum of PM567
in the same solvent is also included for comparison. Both the
absorption and the fluorescence bands of the 8-phenyl-
substituted analogues are bathochromically shifted (around 5
nm) with respect to those of PM567.25 The shape and position
of the absorption and fluorescence bands are similar in both
2
7
etry. Such conformation is a consequence of the geometrical
restrictions imposed by the two methyl groups in the 1 and 7
2
8-31
positions
because an 8-aromatic substituent in the P‚BF2
chromophore without 1- and 7-methyl groups leads to important
changes in the fluorescence properties owing to the nearly planar
30
conformation of both π systems in the excited state.
The photophysical properties of dilute solutions of PAr1Ac
are similar to those of PAr3Ac in a common solvent (Table 1),
with only a slight bathochromic shift (around 1 nm) in both the
absorption and fluorescence bands of PAr3Ac with respect to
PAr1Ac and a slight increase in the molar absorption coefficient
and fluorescence quantum yield and lifetime (which is reflected
in a slight increase in the fluorescence processes probability,
kfl) in the former dye. These results indicate that the length of
the linking polymethylene chain at the para position of the
phenyl group does not affect the photophysics of the chro-
8
-phenyl dyes and are reminiscent of the corresponding bands
observed in PM567. The absorption and fluorescence intensities
are slightly lower than those of PM567, mainly in the
fluorescence emission. The fluorescence decay curves of
PAr1Ac and PAr3Ac in dilute solution are analyzed as one-
exponential decays (Figure 2) with a lifetime of around 5-6
ns, which is close to that of PM567 in dilute solution.
These results suggest that the presence of the 8-phenyl
substituent does not extensively affect the photophysical proper-

3318 J. Phys. Chem. A, Vol. 108, No. 16, 2004
Garc ´ı a-Moreno et al.
TABLE 1: Photophysical and Lasing Properties of the PArnAc Dyes in Several Solventsa
-
4
λ
ab
ꢀ
max × 10
λ
fl
φ
τ
k
fl
k
nr
λ
la
-
1
-1
(10 s-1)
8
(10 s-1)
8
solvent
((0.1 nm)
(M cm
)
((0.4 nm)
((0.05)
((0.05 ns)
(nm)
%eff
PAr1Ac
0.81
0.71
0.68
0.65
0.65
0.45
F
3
-ethanolb
521.6
522.3
523.6
522.2
522.6
526.0
6.56
7.38
7.53
7.02
7.59
8.05
535.2
535.6
536.0
536.0
536.0
538.0
6.35
5.18
5.18
4.82
5.00
3.68
1.27
1.37
1.31
1.34
1.30
1.22
0.30
0.56
0.62
0.73
0.70
1.49
552
556
555
554
554
555
43
41
43
44
42
40
methanol
ethanol
acetone
ethyl acetate
c-hexane
PAr3Ac
0.90
0.77
0.72
0.65
0.69
0.49
F
3
-ethanol
520.2
521.3
522.4
521.4
521.7
525.1
6.90
7.81
7.95
7.91
7.91
8.63
534.0
534.8
535.2
535.2
534.8
537.2
6.51
5.33
5.31
4.92
5.08
3.88
1.38
1.44
1.35
1.32
1.35
1.26
0.15
0.43
0.52
0.71
0.61
1.31
548
549
552
549
548
552
46
44
45
44
43
41
methanol
ethanol
acetone
ethyl acetate
c-hexane
a
Wavelength of maximum absorption (λab), fluorescence (λfl) and laser (λla) emission, molar absorption coefficient (ꢀmax), and fluorescence
-
6
quantum yield (φ) and lifetime (τ) as well as percent lasing efficiency (%eff). Concentration: 2 × 10 M in absorption and fluorescence data;
-
4
-4
[
PAr1Ac] ) 8.0 × 10 M and [PAr3Ac] ) 4.5 × 10 M in lasing data. b 2,2,2-Trifluoroethanol.
deactivation mechanism of the new dyes, the probability of
intersystem crossing in PAr1Ac with respect to that in PM567
in aerated benzene solutions was analyzed through the corre-
sponding T-T absorption spectrum as well as the quantum yield
3
4
of singlet oxygen generation. The results attained from these
experiments demostrated that the spectral characteristics of the
T-T absorption band and the formation of singlet oxygen
(quantum yields in benzene: 0.090 and 0.078 for PM567 and
PAr1Ac, respectively) are similar in both dyes.
The above arguments led to the assignment of the nonradia-
tive deactivation from the excited state to internal conversion
35
processes. The internal conversion of aromatic compounds has
been ascribed to the flexibility/rigidity of the molecular structure,
which is related, for instance, to a possible rotation of a pendant
2
8,36
phenyl group.
However, as discussed above, the presence
of the 8-phenyl group in the PM567 chromophore does not
support an extra deactivation channel associated with its rotation.
In previous work, it was observed that aromatic solvents
(
benzene, toluene, etc.) decrease the fluorescence quantum yields
Figure 3. Optimized geometry for PAr3Ac obtained by the AM1
semiempirical method in the ground state. The geometry is shown in
two perspectives to emphasize the near-perpendicular disposition of
of P‚BF2 dyes because of an augmentation of the nonradiative
rate constant in these solvents.
1
9,33
Such an extra internal
the 8-phenyl group with respect to the dipyrromethene‚BF
2
π system.
conversion process could be related to the dissipation of
excitation energy through the vibrational movement of the
8-phenyl skeleton.
Because the laser signal is normally obtained in concentrated
solutions of dyes, it is interesting to study the photophysical
properties of the new compounds under these conditions.
Because of the similar photophysical behavior exhibited by both
analogues, the dye concentration effect was studied only in
PAr1Ac.
mophoric core and that the acetoxy group is far away from the
chromophore, avoiding any possible intra- or intermolecular
interaction with the P‚BF2 π system. Similar conclusions were
previously reported for the PM567 analogues PnAc, with a linear
ω-acetoxypolymethylene chain at the 8-position with more than
three methylene linking units.14
The evolution of the photophysical properties with the solvent
for both dyes is nearly the same (Table 1) and is similar to that
observed for other P‚BF2 dyes:14,19 the absorption and fluores-
cence bands are shifted toward higher energies, and the
fluorescence quantum yields and lifetimes increase when
changing from apolar to polar protic solvents. These evolutions
are related to the influence of the solvent on the stabilization
of the resonant structures of P‚BF2 dyes, as discussed else-
where.1
Figure 4 shows the absorption and fluorescence spectra of
PAr1Ac at different concentrations. The shape of the absorption
band is nearly independent of the dye concentration, suggesting
that aggregation in this dye is negligible, at least at a concentra-
-
3
tion of up to 10 M. This low (if any) aggregation tendency
of P‚BF2 dyes is important when pyrromethenes dyes are
compared with rhodamines as active media in tunable lasers
because the aggregation of rhodamines (probably the most
commonly used laser dyes) results in efficient quenching of the
9,33
The fluorescence quantum yield and lifetime of PAr1Ac and
PAr3Ac are lower than those observed for the PM567 dye
2
2
37
monomer fluorescence emission. The fluorescence band of
mainly because of an increase in the probability of the
nonradiative processes due to the presence of the phenyl group.
The radiative deactivation probability of these 8-aromatic
analogues remains high, as reflected in their high molar
absorption coefficient. To gain more insight into the nonradiative
PAr1Ac is shifted toward lower energies (Figure 4) in highly
concentrated samples when measurements are made in 0.01-
cm path length cuvettes. However, the band returns to its
position in dilute solutions when the fluorescence spectra are
registered using a narrower cuvette (0.001 cm). This dependence

8-Phenyl-Substituted Dipyrromethene‚BF2 Complexes
J. Phys. Chem. A, Vol. 108, No. 16, 2004 3319
TABLE 3: Laser Efficiency (%eff) for the 8-Phenyl
Dipyrromethenes Dyes as a Function of the Dye
Concentration in Three Representative Solvents
[dye] × 10-
3
M
dye
solvent
0
.07 0.14 0.20 0.45 0.60 0.80 1.00 1.60 2.00
PAr1Ac F3-EtOH
EtOH
12 22 38 41 44 40 36
7
1
15 31 38 43 41 32
10 22 37 40 36 29
c-hexane
PAr3Ac F3-EtOH 11
23 39 46 46 45 43 39
EtOH
7
16 33 45 44 44 41 36 36
c-hexane
8
19 42 41 40 38 33 31
that these new dyes lase efficiently (Table 1), with energy
conversion efficiency nearly solvent-independent, following the
same behavior previously observed for other analogues.1
The dependence of the laser action on the dye concentration
was analyzed in 2,2,2-trifluoroethanol, ethanol, and cyclohexane
in solutions with optical density in the range of 1.5-35, keeping
the other experimental parameters constant (Table 3). As
expected, the lasing efficiency of the dyes increases significan-
tively with the concentration, reaching a maximum value for
solutions with an optical density of ca. 13. From this point on,
further increases in the dye concentration result in a slight
decrease in the lasing efficiency. The laser emission is shifted
to lower energies as the concentration increases. This trend must
be related to the effect of reabsorption/reemission phenomena
on the emission intensity and could also be the origin of the
decrease in the lasing efficiency observed in the more highly
3,38
Figure 4. Absorption and fluorescence (scaled to the fluorescence
quantum yield) spectra of PAr1Ac in cyclohexane: dilute solutions (2
-
6
×
10 M) and 1-cm path length cuvettes (s); concentrated solutions
-
3
(
10 M) and 0.01-cm (- ‚ -) and 0.001-cm (- - -) path length cuvettes.
TABLE 2: Fluorescence Quantum Yields (O) and Lifetimes
-
3
(
τ) of Concentrated PAr1Ac Solutions (10 M) in 0.01- and
0
.001-cm Path Length (l) Cuvettesa
l ) 0.01 cm
l ) 0.001 cm
φ (φb)
((0.05)
τ (τb)
((0.05 ns)
φ
τ
solvent
((0.10)
((0.05 ns)
F
3
-ethanol
0.57 (0.68)
0.58 (0.68)
0.56 (0.66)
0.55 (0.67)
0.55 (0.64)
0.39 (0.48)
7.67 (6.88)
6.43 (5.71)
6.63 (5.92)
6.15 (5.33)
6.41 (5.67)
4.60 (4.00)
0.75
0.75
0.64
0.68
0.67
0.46
6.30
5.28
5.27
4.90
5.16
3.81
methanol
ethanol
acetone
ethyl acetate
c-hexane
2
3
concentrated solutions.
The actual effect of the solvent on the lasing efficiency can
be detected only in moderatly concentrated samples (optical
density < 10) and follows the same dependence as that exhibited
by PM567: the polar protic nature of the solvent (2,2,2-
trifluoroethanol and ethanol) improves the lasing efficiency of
the dyes with respect to the values registered in polar nonprotic
and apolar solvents. Consequently, and in good agreement with
the behavior of the PM567 dye, polar protic solvents such as
a
Other photophysical properties are not included because they are
b
the same as those obtained in diluted solutions. Values corrected from
reabsortion and reemission effects.
3
of the recorded fluorescence band on the path length of the
cuvette suggests an important influence of the reabsorption/
reemission effects when high-optical-density solutions are
analyzed.23
2,2,2-trifluoroethanol are recommended as the best liquid media
for the laser operation of these new dyes. In addition, for all of
the selected solvents and in moderately concentrated solutions,
the lasing efficiency increases with the length of the polym-
ethylene chain, following the same behavior as that observed
Table 2 lists the fluorescence quantum yields (φ) and lifetimes
-3
(
τ) in concentrated solutions (10 M) with two different optical
path length cuvettes in several solvents. The φ and τ values
obtained in the 0.01-cm cuvette are lower and higher, respec-
tively, than the corresponding values recorded in the narrower
14
for PnAc dyes.
The lasing characteristics observed in moderately concentrated
solutions of PArnAc dyes show good correlations with their
photophysical properties in dilute solution. Thus, the highest
fluorescence quantum yield was observed in 2,2,2-trifluoroet-
hanol for both homologous, which is related to the highest lasing
efficiencies obtained in polar protic solvents. In addition, the
lasing efficiency of these new dyes compares well with those
obtained for P1Ac, P3Ac, and P5Ac dyes in all of the solvents
studied and gives results that are slightly lower than those
reached with P10Ac and P15Ac dyes as well as with the
0
.001-cm cuvette, which are similar to those observed in dilute
solutions (Table 1). The influence of reabsorption/reemission
phenomena in the φ and τ values observed in the 0.01-cm
23
cuvette is not completely corrected by mathematical methods,
but these phenomena are practically negligible in the 0.001-cm
cuvette, although in this case a higher experimental error in the
φ value is obtained. The augmentation of the dye concentration
produces a diminution in the φ value in the polar solvent 2,2,2-
trifluoroethanol, from 0.81 to 0.75 in concentrated solutions (l
)
0.001 cm), and to 0.68 after reabsorption/remission correction
13,14
difunctionalized analogues.
This lasing behavior also follows
in the 0.01-cm cuvette (fluorescence recorded with high
reabsorption/reemission effects). This tendency leads to the
equalization of the φ value for concentrated solutions in polar
media, although the lowest φ and τ values of PAr1Ac are still
obtained in cyclohexane. From this photophysical study, there
is no evidence for an intermolecular interaction affecting the
photophysical properties of PAr1Ac in the very polar 2,2,2-
trifluoroethanol environment.
the trend observed in the photophysical properties: the φ values
of PnAc dyes (n ) 1, 3, and 5) are similar to those of PArnAc
and are slightly lower than those registered for P10Ac and
P15Ac dyes.
Despite having both lower φ and higher knr values, the
PArnAc dyes lase more efficiently than the commercial PM567
22
dye in ethanol, ethyl acetate, acetone, and cyclohexane. The
laser emission of the PArnAc dyes shifts up to 13 nm to shorther
wavelengths with respect to that of PM567. As a result, laser
action in PArnAc complexes takes place at a wavelength closer
to its maximum of fluorescence than in the case of PM567,
where the laser emission peaked at a wavelength where its
Lasing Properties in the Liquid Phase. The concentrations
-
4
of PAr1Ac and PAr3Ac in these experiments were 8 × 10
-
4
and 4.5 × 10 M, respectively, leading to solutions with an
optical density at the pump laser radiation of ca. 13. It is seen

3320 J. Phys. Chem. A, Vol. 108, No. 16, 2004
Garc ´ı a-Moreno et al.
TABLE 4: Photophysical Parameters of PArnAc/PMMA and COP(PArnMA-MMA) with n ) 1 and 3a
λ
ab
ꢀ
max
λ
fl (λflb
(nm)
)
τ (τb)
(ns)
(10 M cm-1
4
-1
)
φ (φb)
material
(nm)
PAr1Ac/PMMA
COP(PAr1MA-MMA)
PAr3Ac/PMMA
524.7
524.9
523.7
524.1
6.90
8.00
8.36
8.65
546.4 (536.4)
546.0 (536.8)
542.8 (534.4)
543.2 (535.2)
0.69 (0.82)
0.69 (0.84)
0.65 (0.82)
0.61 (0.80)
11.14 (9.37)
11.35 (9.42)
10.62 (8.25)
10.56 (8.01)
COP(PAr3MA-MMA)
a
-3
Dye concentration: 1.5 × 10 M. Absorption (λab) and fluorescence (λfl) wavelengths, molar absorption coefficient (ꢀmax), fluorescence quantum
yield (φ) and lifetime (τ) for the decay component. Values corrected from reabsorption and reemission effects.3
b
a
TABLE 5: Laser Parameters for 8-Phenyl
2
Dipyrromethene‚BF Dyes in PMMA as a Solution (PArnAc/
PMMA, n ) 1 and 3) or Copolymerized with MMA
(
COP(PArnMA-MMA))b
lifetimec
(mM) (nm) (nm) %eff 60 000 100 000
[c]
λ
la
∆λ
material
PM567/PMMA
PAr1Ac/PMMA
PAr1Ac/PMMA
COP(PAr1MA/MMA) 0.8
COP(PAr1MA/MMA) 1.5
PAr3Ac/PMMA
PAr3Ac/PMMA
COP(PAr3MA/MMA) 0.45 551
1.5
0.8
1.5
562
555
558
556
558
7
8
15
5
9
6
12
5
9
12
23
18
21
20
21
18
20
16
0
62
73
88
96
0.45 551
1.5 554
75
83
75
96
COP(PAr3MA/MMA) 1.5
555
Figure 5. Absorption and normalized fluorescence (corrected for
reabsorption and reemission effects) spectra of PAr1Ac/PMMA (s)
and COP(PAr1MA-MMA) (- - -).
a
λ
la, peak wavelength of the laser emission; ∆λ, FWHM of the laser
b
emission, %eff, energy-conversion efficiency. Nd:KGW laser (second
harmonic) pump energy: 5.5 mJ/pulse; repetition rate: 10 Hz. Data
for PM567 are included for comparison c Percent intensity of the dye
laser output after n pump pulses with reference to the initial intensity.
fluorescence intensity had considerably declined. Consequently,
in PArnAc dyes the laser gain coefficient, which is proportional
to the population inversion, is significantly enhanced with
respect to that of PM567, performing efficient laser emission
despite their photophysical properties.
When the laser signals are obtained in highly concentrated
solutions, the laser efficiency becomes independent of the
environment, and both the influence of the solvent on the laser
emission and the good agreement between photophysics and
lasing properties is somewhat lost. The high optical density of
these samples, in which the saturation of the excitation beam is
more probable and reabsorption/reemission effects must be very
important, could lead to this low environmental dependence of
the fluorescence and laser intensity.
solution, which is attributed to changes in the vibronic structure
of the electronic band in the solid environment. Table 4 lists
the photophysical properties of PArnAc in solid polymers. The
peak wavelengths of the absorption and emission bands are close
to those obtained in polar solvents, indicating that the framework
of the solid polymer does not extensively affect the photophysics
of PArnAc dyes. However, the rigid structure of the polymeric
matrices could lead to a reduction in the flexibility of the dye’s
molecular structure, decreasing the probability of internal
conversion and explaining the observed increase in the φ values
in solid polymers (Table 4) with respect to the values reached
in polar liquid solvents (Table 1). Although the covalent linkage
of the 8-phenyl P‚BF2 dyes to the polymeric chain does not
cause any appreciable modification of the φ values, the important
improvements formerly observed in the photo- and thermosta-
bility of several P‚BF2 dyes bound to polymeric chains16 led us
to study the laser behavior of a number of samples of the new
Photophysical Properties in the Solid State. The PArnAc
dyes have been incorporated into a poly(methyl methacrylate)
(PMMA) matrix as dopants (PAr1Ac/PMMA and PAr3Ac/
PMMA), and their analogues PArnMA have been covalently
bound to the PMMA chain (COP(PAr1MA-MMA) and COP-
(PAr3MA-MMA)). The photophysical properties of all of these
8
-phenyl analogues incorporated into solid matrices of MMA.
Lasing Properties in the Solid-State. The experiments were
carried out in samples with the same dye concentration as that
producing the highest lasing efficiency in liquid solution. To
assess the effect of the optical density on laser operation,
solid materials were also measured.
Under the measurement conditions (polymeric disks, dye
-
3
concentration 1.5 × 10 M, and 0.2-mm path length), the
reabsorption/reemission phenomena affect the fluorescence
properties of these systems. This is corroborated by the obtained
decay curves for COP(PAr1MA-MMA) (Figure 2, curve B),
where the deconvolution leads to a growing and a decay
component. The growing component is explained by a time
delay between the excitation pulse and the maximum population
of the fluorescence excited state, which is due to consecutive
reabsorption/reemission phenomena at the excitation beam.
Successive reabsorption/reemission processes at the emission
wavelength increase the recorded time in which the molecules
are in the excited state (long-lifetime decay component).
Figure 5 shows the absorption and fluorescence (corrected
-3
materials with a higher concentration (1.5 × 10 M) were also
prepared, and their lasing properties were registered and
compared with those exhibited by other P‚BF2 analogues
1
6,37,39
incorporated into polymeric matrices.
Broadband and efficient laser emission was obtained from
all of the studied materials (Table 5). As the dye concentration
increases, the reabsorption/reemission phenomena shift the
emission band to lower energies and widen the bandwidths. The
8-phenyl P‚BF2 dyes incorporated into PMMA lase much more
efficiently than the PM567 dye under the same conditions.
However, the lasing efficiencies of the new dyes, in the range
of 16-23%, are somewhat lower than those obtained with other
monofunctionalized dipyrromethene dyes dissolved or copoly-
23
for reabsorption/reemission effects) bands of PAr1Ac/PMMA
and COP(PAr1MA-MMA). The spectral bands in polymeric
matrices are slightly broader than those obtained in liquid

8-Phenyl-Substituted Dipyrromethene‚BF2 Complexes
J. Phys. Chem. A, Vol. 108, No. 16, 2004 3321
into solid polymeric matrices. The presence of an 8-phenyl group
in the chromophore leaves the photophysics of the dye practi-
cally unmodified so that in liquid solution it depends mainly
on the solvent polarity. Very polar protic solvents are recom-
mended as the best liquid media for laser operation because
the highest values of the fluorescence quantum yields are
obtained in these solvents.
Despite having both lower φ and higher knr values, the new
dyes lase more efficiently that PM567 in solvents such as
ethanol, ethyl acetate, acetone, and cyclohexane under the same
experimental conditions. The reference dye PM567 exhibited a
lasing efficiency of 12% when doped in PMMA, whereas the
lasing efficiency of the new materials ranged from 16 to 23%.
The emission of PM567 incorporated into PMMA drops to zero
after less than 40 000 pump pulses, whereas the laser emission
of COP(PAr1MA/MMA) and COP(PAr3MA/MMA) materials
remains at 96% of its initial value after 100 000 pump pulses
at a 10-Hz repetition rate.
The results presented in this work indicate that appropriate
chemical modifications in the dipyrromethene molecules can
yield dyes that lase efficiently and with remarkable photostability
when properly incorporated into polymeric matrices, rendering
materials that can actually compete with the liquid dye lasers
and make possible the implementation of a commercial solid-
state dye laser.
Figure 6. Normalized laser output as a function of the number of pump
pulses for the PAr1Ac dye dissolved in PMMA, (PAr1Ac/PMMA) (A),
and for PAr1MA copolymerized with MMA, COP(PAr1MA/MMA)
-
3
(
B). Dye concentration: 0.8 × 10 M. Pump energy and repetition
rate: 5.5 mJ/pulse and 10 Hz, respectively.
merized with MMA,13,37,39 following the same behavior exhib-
ited by the fluorescence quantum yields.
The evolution of the laser output as a function of the number
of pump pulses in the same position in the sample was studied
for the different materials. The intensities of the laser output
after n pump pulses with reference to the initial intensity of the
laser emission (In (%) ) (In/I0) × 100, where I0 is the initial
intensity), with n ranging from 60 000 for the model dyes to
Acknowledgment. This work was supported by Projects
MAT2000-1361-C04-01 and MAT2000-1361-C04-02 of the
Spanish MCYT. J.B.P. thanks the Universidad del Pa ´ı s Vasco
for a predoctoral grant. L.C. thanks the CNPq of Brazil for a
research grant. Thanks are also given to Profesors N. A. Garc ´ı a
and S. Bertolotti for the determination of quantum yields of
singlet oxygen generation.
1
00 000 for the copolymer samples, are listed in Table 5.
For the sake of clarity, the evolution of the laser output with
the number of pump pulses is shown in Figure 6 for the model
dye PAr1Ac/PMMA and the copolymer COP(PAr1MA-MMA).
It can be appreciated that the material where the chromophore
is covalently bonded to the polymeric chains exhibits a higher
photostability than that of the material where the same dye is
simply dissolved in the polymer, confirming that the covalent
linkage provides additional channels for the elimination of the
absorbed pump energy that is not converted into emission, which
prevents the accumulation of heat in the material.
For a given concentration, the lasing efficiency and lifetime
become nearly independent of the length of the polymethylene
linking chain, following the same behavior observed for the
fluorescence quantum yield values. In all cases, the increase in
the chromophore concentration resulted in a slight decrease in
lasing efficiency (correlated with a decrease in the fluorescence
quantum yield) but a significant increase in laser photostability
because the increased concentration of the dye can compensate
to some extent for the photodegradation of the dye molecules
caused by the excitation pulses, resulting in apparently enhanced
laser photostability.
Appendix
General Methods. Analytical thin-layer chromatography was
performed on silica gel-precoated aluminum foils (Merck
6
0F254, 0.25 mm). Flash column chromatography was per-
formed on silica gel (Merck, 230-400 mesh). Melting points
were measured on a Reichert-Kofler hot-stage microscope and
are uncorrected. Yields are reported in reference to isolated pure
1
13
compounds. H and C NMR spectra were taken on an INOVA-
00 spectrometer. Chemical shifts are reported in ppm using
3
as an internal reference the peak of a trace amount of
undeuterated solvent or the carbon signal of the deuterated
solvent: δ 7.26 and 77.0 in CDCl3. The following abbreviations
are used to describe the signals: s (singlet), d (doublet),
t (triplet), q (quartet), and m (complex multiplet). Infrared
-1
spectra (in cm ) were recorded on a Perkin-Elmer 681
spectrophotometer. Low-resolution mass spectra were recorded
by electron impact (70 eV) in a Hewlett-Packard 5973 spec-
trometer in the direct injection mode. High-resolution mass
spectra were determined by electron impact (70 eV) in an
AutoSpec Micromass (Waters) apparatus in direct-injection
mode (peak matching) with perfluorokerosene as an exact mass
standard. UV-vis absorption spectra were registered on a
Perkin-Elmer Lambda-16 spectrophotometer.
The lasing stabilities of the new materials studied in this work
clearly improve the useful lifetime of PM567 and analogues
16
PnAc and PnMA, all incoporated into PMMA. This enhance-
ment could be related to a higher photochemical stabilization
of the chromophore rather than to a decline in the nonradiative
deactivation processes because all dyes present similar values
for the knr rate constant.
1
PAr1Cl: Red crystals; yield 27%; mp 172-174 °C. H NMR
(
300 MHz, CDCl3, 25 °C): δ 0.89 (t, J ) 7.5 Hz, 6 H, 2 ×
CH3CH2), 1.2 (s, 6 H, CH3-C1, CH3-C7), 2.21 (q, J ) 7.5
Hz, 4 H, 2 × CH3CH2), 2.44 (s, 6 H, CH3-C3, CH3-C5), 4.58
(s, 2 H, CH2Cl), 7.19 (d, J ) 8.2 Hz, 2 H, 2 × H-Ar), 7.42 (d,
IV. Conclusions
In this paper, we report efficient and highly photostable laser
operation from newly synthesized dipyrromethene‚BF2 dyes,
analogues of PM567, in liquid solutions as well as incorporated
1
3
J ) 8.2 Hz, 2 H, 2 × H-Ar). C NMR (75 MHz, CDCl3, 25
°C): δ 11.6 (CH3Ar), 12.4 (CH3-Ar), 14.4 (CH3CH2), 17.0

3322 J. Phys. Chem. A, Vol. 108, No. 16, 2004
Garc ´ı a-Moreno et al.
(
CH3CH2), 45.5 (CH2Cl), 128.7 (CH-3′, CH-5′), 129.0 (CH-2′,
(C-3, C-5), 167.0 (CdO). MS EI m/z (%): 479 (nominal mass,
M ) (31), 478 (100), 463 (82), 393 (10), 378 (6), 189 (4). HRMS
+
CH-6′), 130.6 (C-7a, C-8a), 132.8 (C-2, C-6), 135.8 (C-4′), 136.1
(
C-1′), 138.4 (C-1, C-7), 139.4 (C-8), 153.8 (C-3, C-5). MS EI
(EI): calcd for C28H33BF2N2O2, 478.2603; found, 478.2604. IR
+
-1
m/z (%): 428 (nominal mass, M ) (96), 413 (100), 393 (9), 363
(KBr) νmax: 1721, 1540, 1474, 1315, 1185, 977 cm
1
(6), 196 (8), 189 (8). IR (KBr) νmax: 1540, 1474, 1319, 1192,
PAr3MA: Orange crystals; yield 55%; mp 120-121 °C. H
-
1
-1
-1
1
(
177, 997 cm . UV-vis (EtOH) λmax (ꢀ, M cm ): 376
NMR (300 MHz, CDCl , 25 °C): δ ) 0.98 (t, J ) 7.5 Hz, 6
3
7850), 523 (81 800) nm.
H, 2 × CH3CH2), 1.29 (s, 6 H, CH3-C1, CH3-C7), 2.04 (m,
1
3 H, CH CdCH ), 1.99-2.04 (m, 2 H, CH CH O), 2.30 (q, J
PAr3Br: Red crystals; yield 32%; mp 156-158 °C. H NMR
300 MHz, CDCl3, 25 °C): δ 0.89 (t, J ) 7.5 Hz, 6 H, 2 ×
3
2
2
2
)
7.5 Hz, 4 H, 2 × CH3CH2), 2.53 (s, 6 H, CH3-C3, CH3-
C5), 4.17 (t, J ) 7.6 Hz, 2 H, CH2-C4′′), 4.17 (t, J ) 6.6 Hz,
H, CH2O), 5.60 (m, 2 H, CHHdCH2), 6.16 (m, 2 H, CHHd
(
CH3CH2), 1.25 (s, 6 H, CH3-C1, CH3-C7), 2.22-2.12 (m, 2
H, CH2CH2Br), 2.27 (q, J ) 7.5 Hz, 4 H, 2 × CH3CH2), 2.50
2
CH2), 7.19 (d, J ) 8.0 Hz, 2 H, 2 × H-Ar), 7.31 (d, J ) 8.0
(
s, 6 H, CH3-C3, CH3-C5), 2.85 (t, J ) 7.2 Hz, 2 H, CH2-
1
3
Hz, 2 H, 2 × H-Ar). C NMR (75 MHz, CDCl3, 25 °C): δ
C4′′), 3.37 (t, J ) 6.5 Hz, 2 H, CH2Br), 7.17 (d, J ) 8.2 Hz, 2
1
3
11.6 (CH Ar), 12.3 (CH Ar), 14.5 (CH CH ), 17.0 (CH CH ),
H, 2 × H-Ar), 7.29 (d, J ) 8.2 Hz, 2 H, 2 × H-Ar). C NMR
3
3
3
2
3
2
18.5 (CH3CdCH2), 31.8, 30.1 (CH2CH2-C4′′), 60.2 (CH2O),
125.3 (CH2dC), 128.2 (CH-3′, CH-5′), 128.9 (CH-2′, CH-6′),
130.8 (C-7a, C-8a), 132.6 (C-2, C-6), 133.4 (C-1′), 136.3
(
(
3
75 MHz, CDCl3, 25 °C): δ 11.6 (CH3Ar), 12.4 (CH3Ar), 14.6
CH3CH2), 17.0 (CH3CH2), 32.77 ((CH2Br), 33.80 (CH2-C4′′),
4.1 (CH2CH2Br), 128.5 (CH-3′, CH-5′), 129.3 (CH-2′, CH-
′), 130.9 (C-7a, C-8a), 132.8 (C-2, C-6), 133.7 (C-1′), 138.4
(CH3CdCH2), 138.3 (C-1, C-7), 140.2 (C-8), 141.8 (C-4′), 153.4
6
(
C-3, C-5), 167.2 (CdO). MS EI m/z (%): 506 (nominal mass,
(C-1, C-7), 140.1 (C-8), 141.3 (C-4′), 153.0 (C-3, C-5). MS EI
+
+
M ) (100), 491 (55), 405 (10), 391 (11), 378 (5). HRMS (EI):
calcd for C H BF N O , 506.2916; found, 506.2912. IR (KBr)
νmax: 1718, 1542, 1477, 1321, 1194, 980 cm .
m/z (%): 500 (nominal mass, M ) (100), 485 (85), 405 (16),
3
-1
78 (13), 196 (13). IR (KBr) νmax: 1538, 1474, 1187, 976 cm .
30 37
2
2
2
-
1
1
PAr1Ac: Red crystals; yield 65%; mp 174-176 °C. H
NMR (300 MHz, CDCl3, 25 °C): δ 0.97 (t, J ) 7.5 Hz, 6 H,
2
References and Notes
× CH3CH2), 1.29 (s, 6 H, CH3-C1, CH3-C7), 2.17 (s, 3 H,
CH3CO), 2.31 (q, J ) 7.7 Hz, 4 H, 2 × CH3CH2), 2.54 (s, 6 H,
(1) Pavlopoulos, T. G.; Shah, M.; Boyer, J. H. Opt. Commun. 1989,
7
0, 425.
(2) Shah, M.; Thangaraj, K.; Soong, M. L.; Wolford, L. T.; Boyer, J.
H.; Politzer, I. R.; Pavlopoulos, T. G. Heteroat. Chem. 1990, 1, 389.
3) Pavlopoulos, T. G.; Boyer, J. H.; Shah, M.; Thangaraj, K.; Soong,
M. L. Appl. Opt. 1990, 29, 3885.
4) Boyer, J. H.; Haag, A. M.; Soong, M. L.; Thangaraj, K.; Pavlopou-
los, T. G. Appl. Opt. 1991, 30, 3788.
5) Boyer, J. H.; Haag, A. M.; Sathyamoorthi, G.; Soong, M. L.;
CH3-C3, CH3-C5), 5.22 (s, 2 H, CH2O), 7.29 (d, J ) 8.1 Hz,
1
3
2
H, 2 × H-Ar), 7.49 (d, J ) 8.0 Hz, 2 H, 2 × H-Ar).
C
NMR (75 MHz, CDCl3, 25 °C): δ 11.7 (CH3Ar), 12.4 (CH3-
Ar), 14.5 (CH2CH3), 17.0 (CH2CH3), 21.0 (CH3CO), 65.6
(
(
(CH2O), 128.4 (CH-3′, CH-5′), 128.5 (CH-2′, CH-6′), 130.7 (C-
7
a, C-8a), 132.8 (C-2, C-6), 135.6 (C-4′), 136.8 (C-1′), 138.8
(
(C-1, C-7), 139.6 (C-8), 153.8 (C-3, C-5), 170.8 (CdO). MS
Thangaraj, K.; Pavlopoulos, T. G. Heteroat. Chem. 1993, 4, 39.
(6) Partridge, W. P.; Laurendean, M. N.; Johnson, C. C.; Steppel, R.
N. Opt. Lett. 1994, 19, 1630.
+
EI m/z (%): 452 (nominal mass, M ) (95), 437 (100), 423 (9),
3
4
1
93 (15), 189 (4). HRMS (EI): calcd for C26H31BF2N2O2,
(
7) Pavlopoulos, T. G.; Boyer, J. H.; Thangaraj, K.; Sathyamoorthi,
G.; Shah, M. P.; Soong, M. L. Appl. Opt. 1992, 31, 7089.
8) O’Neil, M. P. Opt. Lett. 1993, 18, 37.
52.2447; found, 452.2454. IR (KBr) νmax: 1740, 1541, 1476,
-
1
192, 979 cm .
PAr3Ac: Orange crystals; yield 73%; mp 128-130 °C. H
NMR (300 MHz, CDCl3, 25 °C): δ 0.97 (t, J ) 7.5 Hz, 6 H,
× CH3CH2), 1.28 (s, 6 H, CH3-C1, CH3-C7), 1.98-2.05
m, 2 H, CH2CH2O), 2.09 (s, 3 H, CH3CO), 2.29 (q, J ) 7.5
Hz, 4 H, 2 × CH3CH2), 2.52 (s, 6 H, CH3-C3, CH3-C5), 2.78
t, J ) 7.6 Hz, 2 H, CH2-C4′′), 4.08 (t, J ) 6.6 Hz, 2 H, CH2O),
(
1
(9) Rahn, M. D.; King, T. A.; Gorman, A.; Hamblett, I. Appl. Opt.
997, 36, 5862.
1
(10) Zeng, H.; Liang, F.; Sun, Z., Yuan, Y.; Yao, Z.; Su, Z. J. Opt.
2
(
Soc. Am. B 2002, 19, 1349.
(11) Costela, A.; Garc ´ı a-Moreno, I.; Sastre, R. In Handbook of AdVanced
Electronic and Photonic Materials and DeVices; Nalwa, H. S., Ed.;
Academic Press: San Diego, CA, 2001; Vol. 7, p 161.
(
7
2
(12) Pavlopoulos, T. G. Prog. Quantum Electron. 2002, 26, 193.
.19 (d, J ) 8.1 Hz, 2 H, 2 × H-Ar), 7.29 (d, J ) 8.1 Hz, 2 H,
(13) Costela, A.; Garc ´ı a-Moreno, I.; G o´ mez, C.; Amat-Guerri, F.; Sastre,
13
× H-Ar). C NMR (75 MHz, CDCl3, 25 °C): δ 11.6 (CH3-
R. Appl. Phys. Lett. 2001, 79, 305.
Ar), 12.5 (CH3Ar), 14.6 (CH3CH2), 17.0 (CH3CH2), 21.0 (CH3-
CO), 33.2, 31.9 (PhCH2CH2), 63.5 (CH2O), 128.3 (CH-3′, CH-
5
(14) Costela, A.; Garc ´ı a-Moreno, I.; G o´ mez, C.; Sastre, R.; Amat-Guerri,
F.; Liras, M.; L o´ pez Arbeloa, F.; Ba n˜ uelos Prieto, J.; L o´ pez Arbeloa, I. J.
Phys. Chem. A 2002, 106, 7736.
′), 128.9 (CH-2′, CH-6′), 130.8 (C-7a, C-8a), 132.7 (C-2, C-6),
33.5 (C-1′), 138.4 (C-1, C-7), 140.0 (C-8), 141.8 (C-4′), 153.5
(15) Amat-Guerri, F.; Liras, M.; Carrascoso, M. L.; Sastre, R. Photo-
1
chem. Photobiol. 2003, 77, 577.
(
C-3, C-5), 176 (CdO). MS EI m/z (%): 480 (nominal mass,
(16) L o´ pez Arbeloa, F.; Ba n˜ uelos Prieto, J.; L o´ pez Arbeloa, I.; Costela,
A.; Garc ´ı a-Moreno, I.; G o´ mez, C.; Amat-Guerri, F.; Liras, M.; Sastre, R.
Photochem. Photobiol. 2003, 78, 30.
+
M ) (100), 465 (71), 405 (6), 391 (6). HRMS (EI): calcd for
C28H35BF2N2O2, 480.2760; found, 480.2761. IR (KBr) νmax:
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-
1
1
737, 1539, 1476, 1188, 978 cm .
PAr1MA: Orange crystals; yield 52%; mp 115-117 °C. H
NMR (300 MHz, CDCl3, 25 °C): δ 0.98 (t, J ) 7.7 Hz, 6 H,
× CH3CH2), 1.28 (s, 6 H, CH3-C1, CH3-C7), 2.00 (m, 3
H, CH3CdCH2), 2.30 (q, J ) 7.7 Hz, 4 H, 2 × CH3CH2), 2.53
s, 6 H, CH3-C3, CH3-C5), 5.30 (s, 2 H, CH2O), 5.64 (m, 2
H, CHHdC), 6.2 (m, 2 H, CHHdC), 7.26 (d, J ) 7.8 Hz, 2 H,
Soc. Am. B 2001, 18, 1841.
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1
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(
(
2
13
2
× H-Ar), 7.49 (d, J ) 7.8 Hz, 2 H, 2 × H-Ar). C NMR (75
MHz, CDCl3, 25 °C): δ 11.6 (CH3Ar), 12.4 (CH3Ar), 14.1
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(
(
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25.9 (CH2dC), 128.1 (CH-3′, CH-5′), 128.5 (CH-2′, CH-6′),
30.8 (C-7a, C-8a), 132.8 (C-2, C-6), 135.5 (C-4′), 136.1 (C-
′), 136.9 (CH3CdCH2), 138.3 (C-1, C-7), 139.6 (C-8), 153.7
(

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