Synthesis, characterization of a novel conjugated structural oligomer

Article abstract of DOI:10.4067/S0717-97072015000200023

An octupolar star-shaped ladder-type oligomer composed of electron deriving from 1,3,5-triazine core end-capped by either an electron donating carbazolemoiety(TA(TL)-Ph(3)-CBZ) have been designed and synthesized to investigate the structure-properties relationship of highly efficient multiphoton absorbing materials. The newly synthesized molecules were characterized by ¹H NMR, ¹³C NMR and mass spectrometry. Linear optical properties of the oligomer were investigated by UV-vis and fluorescence spectrometries, as well as the nonlinear optical properties were characterized by two-photon excited fluorescence (2PEF) measurement.

Full text of DOI:10.4067/S0717-97072015000200023

J. Chil. Chem. Soc., 60, Nº 2 (2015)
SYNTHESIS, CHARACTERIZATION OF A NOVEL CONJUGATED STRUCTURAL OLIGOMER
DONG AN, ZHIWEN YE*
Department of Chemical Engineering, Nanjing University of Science and Technology, Nanjing 210094 P. R. China
ABSTRACT
An octupolar star-shaped ladder–type oligomer composed of electron deriving from 1,3,5-triazine core end-capped by either an electron donating
carbazolemoiety(TA(TL)-Ph(3)-CBZ) have been designed and synthesized to investigate the structure-properties relationship of highly efficient multiphoton
absorbing materials. The newly synthesized molecules were characterized by 1H NMR, 13C NMR and mass spectrometry. Linear optical properties of the oligomer
were investigated by UV-vis and fluorescence spectrometries, as well as the nonlinear optical properties were characterized by two-photon excited fluorescence
(2PEF) measurement.
Keywords: Oligomer, TA(TL)-Ph (3)-CBZ, MPA, diphenylamine, ter(p-phenylene.
connected by polarizable π-bridge. The molecules possess MPA properties
are mainly categorized into three classes (Fig.1) which included: (i) dipolar:
A-π-D; (ii) quadruolar: A-π-A; D-π-D; A-π-D-π-A; D-A-π-D; (iii) octupolar:
3-branched, D-core with A branch, A-core with D3 branch. Multiphoton
absorption activities can be c3ommonly observed in these types of compounds
that drawing our attention to investigate the structure-properties relationship
by either tuning the structure of end capped terminal or the acceptor or donor
core [11].
To determine the sensitivity of a 2PA molecular entity in a quantitative
approach, 2PA cross-section (σ ) is employed as a parameter which describes
electronic eigenstates as well a2s transition behavior of a molecule. Thus, the
pivotal factor is utilized to evaluate the performance of a 2PA active molecule.
Basically, the greater the value of 2PA cross-section, the higher of the ability
is in preceding the intramolecular charge-transfer[12-14]. Reported by Wong,
et al, multi-photon absorption activities are more desirable for the (L)-Ph(n)-
NPh (with the number of phenyl rings n, ranged from 3 to 7) with a longer
distance of conjugation system showed generally increasing 2PA and 3PA
cross-section value. The intramolecular charge transfer would be the main
focus on the following experiment on clarifying conjugated system. The MPA
activities as electric polarization plays an important role in adjusting the MPA
activites (Fig.2).
INTRODUTION
Multi-photon absorption was first theoretically predicted by Maria
Goeppert-Mayer (1906-1972) in her doctoral thesis in 1931. In her hypothesis,
it was proposed that simultaneous two-photon absorption may take place
in the quantum theory of radiation [1]. The theory was not confirmed until
the construction of the first laser in 1960s. Invention of laser allowed the
verification of two-photon absorption which is a third order optical process
required a strong coherent light via the detection of two-photon-excited
fluorescence in a europium doped crystal [2].
Three decades after the invention of laser, investigation of two-photon
absorption was enhanced by higher viability of sub-picosecond level pulsed
laser and the two-photon fluorescence microscopy by Webb and co-workers.
In 1990s, development of femtosecond lasing techniques provided more spaces
for in-depth nonlinear optical studies which drawn greater attentions from
either chemical or physical scientists [3-5] .
Figure 2. Structure of MPA active organic molecule (L)-Ph(7)-NPh
Composed of strong π-Donor or strong π-Acceptor, the π-conjugated
system normally has a large transition dipole moment and low excitation value
which enhances the 2PA capacities as well as the 2PA cross section[15].
Figure 1. Primary structural motifs of dipolar, quadrupolar and octupolar
chromophores where A, D and bridge line represents π-acceptor(π-electron
deficient), π-donor (π-electron rich) and polarizable π-bridge respectively.
Contributed by many scientists and research groups, numerous Type II and
some Type III MPA active compounds were successfully synthesized [16-19]
and characterized in the past two decades as investigation of MPA structure-
properties relationship. The π-bridges could be unsaturated aliphatic chains or
aromatic ring which connected the acceptor(such as: triazine, triphenylamine)
and donors (such as, nitrogen-containing heterocyclic aromatic groups).
Inspired by the previous successful work on synthesizing highly efficient
MPA active oligomers by Wong et al, N(TL)-Ph(3)-CBZ and TA(TL)-
Ph(3)-NPH have higher potential of further development [20, 21]. In order to
continue to investigate the properties of these oligomers, some derivatives can
be made to figure out the MPA active oligomers.
On early 1990s, the focus on multi-photon studies shifted from purely
spectroscopic interests to development new muliti-photon absorption
active compounds. Nowadays, numerous principle applications are viable
upon the rapid development of multi-photon active compounds, such as,
three-dimenstional (3D) imaging [6], 3D optical data storage [7], laser up-
conversion[8], 3D microfabrication [9], Nonlinear optical transmission,
photodynamic threapy. Further studies of multiphoton absorption exhibited by
amyloid fibres which are responsible for diseases, such as Alzheimer’s and
Parkinson’s may bring out more inspiration for the therapeutic treatment of
these diseases [10].
Synthesizing weak-D D-Core oligomers for the investigation on the
relation between structural3modifications and its MPA propertie will be a new
trail.
Essentially, highly efficient multi-photon absorption active compounds
composed of three principle components: strong π-donor, strong π-donor and
e-mail: andong688@126.com
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J. Chil. Chem. Soc., 60, Nº 2 (2015)
34.67 mmol) in 150mL dry THF, 2.4M n-BuLi in hexane (10 mL, 24 mmol)
was added dropwise at -78°C under N2 protection. After stirring for 1.5hr with
the temperature below -70°C, B(OMe)3 (8 mL, 71.8 mmol)was added dropwise
into the reaction mixture. The solution mixture was allowed to stir overnight
and slowly warmed to ambient temperature. Thereafter, the solution was
quenched with water and extracted using ethyl acetate. The combined organic
layer was washed with saturated NaCl(aq) and dried over Na2SO . Thus, it was
concentrated and purified using column chromatography to obtai4n a white solid
8.46 g in 85% yield which was directly used in the next step.
Synthesis of compound 2-4
Compound 2-3 (8.46 g, 29.45 mmol), diethyl 2,5-dibromoterephthalate
(22.4 g, 58.9mmol), palladium (II) acetate (65 mg), triphenylphosphine (0.12
g), 4M potassium carbonate (15 mL), ethanol (50 mL) and toluene (250 mL)
were added to a 500 mL two-necked round bottom flask and stirred. The reaction
mixture was heated at 45°C with nitrogen protection for 24 h. After cooling
down to room temperature, the reaction mixture was quenched with water and
acidified by 6 M HCl (3mL). Thereafter, it was extracted with 3 portions of
ethyl acetate and then dried over sodium sulphate. Thus, purification of residue
was carried out via column chromatography to afford a white solid 5.1 g in
1
32% yield. H NMR (400MHz, CDCl3, δ): 8.25-8.14 (m, 3H), 7.97-7.84 (m,
1H), 7.53-7.68 (m, 4H), 7.52-7.42 (m, 4H), 7.36-7.28 (m, 2H), 4.47 (q, J = 7.2
Hz, 2H), 4.23 (q, J = 7.2 Hz, 2H), 1.46 (t, J = 7.2 Hz, 3H), 1.59 (t, J = 7.2 Hz,
3H). MS(MALDI-TOF, m/z): found 542.0964 [M+H]+.
Figure 3. Structures for MPA Active organic molecules.
EXPERIMENTAL
Materials and apparatus
All the solvents were dried by the standard methods wherever needed.
1H NMR spectra were produced using either Bruker advanced- III 400 NMR
spectrometer with a reference of the residual CHCl3 7.26 ppm or DMSO 2.5
ppm. 13C NMR spectra were obtained using Bruker advanced-III 400 NMR
spectrometer with a reference of the residual CHCl3 77.15 ppm or DMSO
39.5 ppm. Mass spectrometer measurements were carried out using fast atom
bombardment (FAB) on the API ASTAR Pulsar I Hybrid mass spectrometer
or matrix-assisted laser desorption ionization-time-of-flight(MALDI-TOF)
technique. Thermal stabilities were determined by thermal gravimetric
analyzer (PE-TGA6) with a heating rate of 20 ˚C/min under N2. All the physical
measurements were performed in toluene including electronic absorption
(UV-Vis) recorded by a Varian Cary UV 100 Scan Spectrophotometer and
fluorescence spectra attained by PTI-QM4 Luminescence Spectrophotometer.
The fluorescence quantum yields in toluene and chloroform were determined
by dilution method using Norharman (Φ330~390=0.58) as standard.
Synthesis of TAZ
4-bromobenzonitrile (4 g, 22 mmol) in dry chloroform (60 mL) was
added dropwise into a trifluoromethanesulfonic acid (4 mL, 44 mmol) in dry
chloroform (10 mL) containing two necked round bottom flask with stirring
at 0°C under nitrogen gas protection. Heat was given out upon the addition
of4-bromobezonitrile. The reaction mixture was stirred for 2 hours at 0°C
and continued to stir for 48hours under ambient temperature and nitrogen gas
protection. It was neutralized by adding small amount of ammonium hydroxide
dropwise in water. The organic layer was washed with water for three times
and then dried over anhydrous sodium sulphate. Solvent was removed in
vacuo. The residual was recrystallized from CH3Cl to obtain a white powder
3.2g in 80% yield. 1H NMR (400MHz, CDCl , δ): 8.55 (d, J = 8.5 Hz, 6H), 7.67
(d, J = 8.5 Hz, 6H). MS(MALDI-TOF, m/z):3calcd. for C21H12Br3N3, 545.8634,
found 545.8658 [M+H]+.
Synthesis of compound 2-2
To
a 500 mL two-necked round bottom flask containing para-
dibromobenzene (16.8 g, 71.8 mmol), carbazole (8.01 g, 47.9 mmol),
1,10-phenathroline(0.86g, 4.79 mmol ), copper(I) chloride(0.474 g, 4.79
mmol), potassium carbonate(19.85 g, 143.6 mmol), 150 mL of ortho-xylene
was added with stirring. The reaction mixture was heated at 150°C for 48h
with nitrogen gas protection. The mixture was diluted with hydrochloric acid
and extracted with ethyl acetate. The crude product was purified by column
chromatography to afford a white crystal 11.13g in yield 72%. 1H NMR
(400MHz, CDCl3, δ): 8.07-8.05 (m, 2H), 7.65-7.62 (m, 2H), 7.39-7.28 (m, 6H),
7.24-7.20 (m, 2H).
Scheme 1. Synthetic route of TA(TL)-Ph(3)-CBZ. Reagent and
conditions: (a) CuCl, 1,10-phenathroline, K CO3, o-xylene, 150°C, 48 h; (b) 1:
n-BuLi, dry THF, -78°C; 2: B(OMe)3, -78°2C to room temperature, overnight.
(c) Pd(OAc) , PPh , 4M K2CO3, H2O/Ethanol/Toluene, 45°C, 36 h; (d)
PdCl2(dppf), 2bis(pin3acolato)diboron, KOAc, 1,4-dioxane, 80°C (e) Pd(OAc)2,
PPh3, 4M K CO , H2O/Ethanol/Toluene, 80°C, reflux, 36 h; (f) 1-bromo-
4-decylbenez2ene,3 n-BuLi, THF, -78°C, 1.5h, then r.t. for 24h; (g) CF3SO3H
dissolved in THF/CH2Cl2, 24 h.
Synthesis of compound 2-3
To a 200 mL two-necked round bottom flask containing 2-2 (11.13 g,
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J. Chil. Chem. Soc., 60, Nº 2 (2015)
Synthesis of compound 2-5
ring-closure catalyzed by trifluoromethanesulfonic acid (Scheme1).
To a 250mL two-necked round bottom flask containing compound 2-4
(5.1 g, 9.43 mmol), bis(pinacolato)-diboron (4.78 g, 18.8 mmol), KOAc (3.7
g, 37.7 mmol) and PdCl2(dppf) (0.15 g, 0.184 mmol), 1,4-dioxane (180 mL)
was added with stirring under N protection. The reaction mixture was allowed
to heat 80°C for 24h. Solvent 2was removed by rotary evaporator and then
the residue was diluted with water. The aqueous solution as extracted using
dichloromethane. The organic layer was combined and dried over Na2SO4. The
crude product was purified via column chromatography to afford a light yellow
Linear optical properties
Thermal properties of the synthesized compound TA(TL)-Ph(3)-CBZ
were characterized by thermogravimetric analysis. TA(TL)-Ph(3)-CBZ
exhibits similar decomposition temperature with the synthesized prototypes
of MPA active oligomers N(TL)-Ph(3)-CBZ, TA(TL)-Ph(3)-NPh and (L)-
Ph(3)-NPh.
1
powder of 2.94 g with 53% yield. H NMR (400MHz, CDCl3, δ): 8.13 (d, J
= 7.7 Hz, 2H), 8.04 (d, 16 Hz, 2H), 7.57 (m, 4H), 7.43 (m, 4H), 7.28 (m, 2H),
4.44(q, J = 7.2 Hz, 2H), 4.19(q, J = 7.2 Hz, 2H), 1.55 (m, 12H), 1.40 (t, J = 7.1
Hz, 3H), 1.09 (t, J = 7.1 Hz, 3H). 13C NMR (100MHz, CDCl , δ): 168.3, 167.3,
142.1, 140.8, 139.8, 137.2, 136.6, 137.2, 136.6, 134.1, 1334.0, 130.6, 130.0,
126.7, 126.1, 123.5, 120.5, 120.2, 109.8, 84.5, 75.0, 67.1, 61.7 (d), 25.0, 24.9,
24.6. MS(MALDI-TOF, m/z): found 589.2680 [M+H]+.
Synthesis of compound 2-6
Compound 2-5 (2.94 g, 4.99 mmol), TAZ (0.68 g, 1.25 mmol), palladium
(II) acetate (60 mg), triphenylphosphine(0.66 g, 2.5 mmol), 4M potassium
carbonate (5 mL), ethanol (40 mL) and toluene (50 mL) were added to a 250
mL two-necked round bottom flask. The reaction mixture was refluxed at 80°C
with nitrogen protection for 36 hr. After cooling down to room temperature,
the reaction mixture was quenched with water and acidified by 6M HCl (3
mL). Thereafter, it was extracted with 3 portions of ethyl acetate and then dried
over sodium sulphate. Thus, purification of residue was carried out via column
1
chromatography to afford a light yellow crystal of 659 mg in yield 31%. H
NMR (400MHz, CDCl3, δ): 9.00 (d, J = 8.2Hz, 6H), 8.16 (m, 12H), 7.74 (m,
18H), 7.53 (m, 12H), 7.37 (t, J = 7.2 Hz, 6H), 4.30 (m, 12H), 1.20 (m, 18H). 13
C
NMR (100MHz, CDCl3, δ): 171.5, 167.8 (d), 144.6, 141.0, 140.8, 139.3, 137.4,
135.7, 133.7 (d), 132.2 (d), 130.1, 129.0 (d), 126.8, 126.1, 123.6, 109.8, 61.7
(d), 14.0. MS(MALDI-TOF, m/z): found 1693.6163 [M+H]+.
Synthesis of TA(TL)-Ph(3)-CBZ
To a dried 250 mL two-necked round bottom flask containing compound
2-6 (659 mg, 0.389 mmol), 1-bromo-4-decylbenzene (3.47 g, 11.67 mmol) and
anhydrous THF (40 mL) with stirring and N protection at -78°C, 2.5M n-BuLi
(3.6 mL, 9.0 mmol)was added dropwise ove2r 20min. The reaction solution was
continued to stir for 2hr with the temperature lower than -70°C then warmed
overnight under ambient temperature and N2 protection. The mixture was then
quenched with hydrochloric acid at 0°C and extracted using three portions of
ethyl acetate. The organic layers were combined, washed with brine and dried
over Na2SO4. A sticky yellow oil was obtained after concentration in vacuo and
then directly used in the next step. To the yellow oil obtained in the previous
step, 40mL dichloromethane was added followed by trifluoromethanesulfonic
acid(0.15 M, 10 mL) in CH2Cl2/THF (100/1). The reaction mixture was
continued to stir for 24 hr at room temperature with N2 protection. The solution
mixture was quenched with water and its organic layer was extracted with two
portions of DCM. The organic layers were combined, washed with H2O and
dried over Na2SO4. The solution was then concentrated by rotary evaporator.
Purification of crude product was carried out by column chromatography with
and obtained yellow solid (477 mg, 0.124 mmol) with the total percentage yield
(2 steps) of 31.2%. 1H NMR (400MHz, CDCl3, δ): 8.74 (m, 6H), 8.15 (d, J =
8H, 6H), 8.0-7.8 (m, 12H), 7.66 (m, 3H), 7.58 (d, J = 8 Hz, 3H), 7.43 (m, 15H),
7.30 (m, 27H), 7.22-7.03 (m, 27H), 2.59 (q, J = 8 Hz, 8H), 1.62 (d, J = 4.5Hz,
21H), 1.26 (m, 168H), 0.87 (q, J = 6.7 Hz, 36H). 13C NMR (100MHz, CDCl3,
δ): 171.5, 167.8 (d), 144.6, 141.0, 140.8, 139.3, 137.4, 135.7, 133.8 (d), 132.5,
132.2 (d), 131.0, 130.1, 129.0 (d), 128.9, 126.8, 126.1, 123.6, 120.5, 120.2,
109.8, 77.2 (t), 68.2, 61.7 (d), 38.8, 30.5, 29.8, 29.0, 23.8, 23.1, 14.2, 14.0,
11.1. MS(MALDI-TOF, m/z): found 3929.7550, requires 3929.7516 [M+H]+.
Figure 5. UV-vis absorption and fluorescence spectra of star-shaped
oligomers in toluene.
The optical properties of newly synthesized compound TA(TL)-Ph(3)-
CBZ were achieved by using UV-Visible and fluorescence spectroscopies.
TA(TL)-Ph(3)-CBZ has good solubility in either chloroform or toluene but
very insoluble in DMF unless heating, which is not suitable to characterize
its linear optical properties in DMF. The linear optical properties were listed
as well as the thermal property in Table-1.The UV-Visible and fluorescence
spectra are shown in Fig.5 and Fig.6.
As shown on the optical spectra Fig.5 and Fig.6, TA(TL)-Ph(3)-CBZ
exhibited a blue shift from the others, which suggests the intramolecular
charge transfer is significantly differ from the prototypes. Absorption below
the 320nm region represents a higher energy acquisition responsible for the
transition from n to π* of the lone pair electron of carbazole moiety. More
intensive absorption between 380 nm and 420 nm depicting the transition of π
to π* of the π-conjugated bridges.
RESULT AND DISCUSSION
Synthesis
The result suggests the carbazole moiety acts differently in terms of electron
inductive effect that means the N-substituted carbazole may largely weakens
its electron withdrawing effect when compared with TA(TL)-Ph(3)-NPh.
The observed derivation can be rationalized by the lower degree of electric
polarization of the π-conjugated system of electron accepting 1,3,5-triazine
core end-capped with carbazole.
TA(TL)-Ph(3)-CBZ has a blue shift on fluorescence spectrum upon
excitation in chloroform when compared with the excitation in toluene, which
suggests solvatochromic effect takes place in emission spectrum conducted
using chloroform.
Theacceptorcorewassynthesizedwiththeyieldof80%bycyclotrimerization
of para-bromobenzonitrile catalyzed by trifluoromethanesulfonic acid. The
compound 2-2 was efficiently synthesized by Ullmann-type condensation
which possessed a high selectivity in giving the mono-substituted, even if the
addition of 2 to 6 equivalent para-dibromobenzene. Hence, a borolyation was
carried out to give the intermediation compound 2-3 which is the precursor used
in synthesizing the compound 2-4 via palladium-catalyzed Suzuki coupling.
Thereafter, a borylation of compound 2-4 was carried out to give the precursor
compound 2-5 in the next step. A three-fold Suzuki coupling was conducted
between compound 2-5 and TAZ to afford compound 2-6 which was converted
to TA(TL)-Ph(3)-CBZ via nucleophilic attack 1-bromo-4-decylbenzene and
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J. Chil. Chem. Soc., 60, Nº 2 (2015)
CONCLUSION
In summary, star-shaped ladder-type ter(p-phenylene) compound
composed of 1,3,5-triazine core with alkylphenyl group attached π-conjugated
arms end-capped with carbazole was synthesized and characterized for its
optical and thermo properties. TA(TL)-Ph(3)-CBZ exhibits a blue shift when
compared with other compounds composed of either triazine or triphenyl core
with the terminals of diphenylamine. TA(TL)-Ph(3)-CBZ can potentially
be employed in the application of blue-light emitting materials with strong
emission of blue shifted light.
ACKNOWLEDGEMENTS
We acknowledge support of this work by the National Science Foundation
of China (Grant no.11076017).
REFERENCES
1. M. M.Goppert, Ann. Physik, 9, 273-295, (1931)
2. W. Kaiser, C. G. Garrett, Phys. Rev. Lett. 7, 229–232, (1961)
3. W. Denk, J. H. Strickler, W. W. Webb, Science. 248, 73, (1990)
4. C. S. Lai, W. Franke, T. F. Gan, Nature. 483, 87-91, (2012)
5. M. L. Drobizhev, N.S. Makarv, S.E. Tillo, T.E. Hughes, A. Rebane,
Nature Methods. 8, 393–399, (2011)
6. I. Polyzos, G. Tsigaridas, M. Fakis, Chem. Phys. Lett. 369, 264-268,
(2003)
7. S. M. Zhang, B. Zhu, S. F. Zhou, S. Q. Xu, J. R. Qiu, Opt Express.15(11),
6883-6888, (2007)
8. H. B. Sun, S. Kawata, Adv. Polym. Sci, 170, 169-273, (2004)
9. C. W. J. Spangler, Material Chemistry. 398, 2013, (1999)
10. W. W. Fisher, W. P. Paratridge, Photochem. Photobiol. 66, 141, (1997)
11. P. Hanczyc, M. Samoc, B. Norden, Nat. Photonics. 7, 969-972, (2013)
12. G. Ramakrishna, T. Goodson, J. Phys. Chem. A. 111, 993, (2007)
13. K. A. L. Nguyen, J. E. Rogers, J. E. Slagle, P. N. L, J. Phys. Chem. A. 110,
13172, (2006)
Figure 6. UV-vis absorption and fluorescence spectra of star-shaped
oligomers in Chloroform.
14. M. Drobizhev, Y. Stepanenko, Y. Dzenis, J. Am. Chem. Soc. 2004, 126,
15352–15353, (2004)
15. Y. Yi, L. Zhu, Z. Shuai, Macromol. Theory Siuml. 17, 12, (2008)
16. R. Kannan, G. S. He, L. Yuan, F. Xu, Chem. Mater. 13, 1896-1904, (2001)
17. A. G. Dillard, J. C. Bhatt, R. Kannan, L. Yuan, Chem. Mater. 10, 1863-
1874, (1998)
18. C. Delacourt, Chem. Mater, 16, 93-99, (2004)
19. M. Drobizhev, Y. Stepanenko, Y. Dzenis, A. Karotki, J. Am. Chem.
Soc. 126, 15352–15353, (2004)
Table 1: Summary of linear optical measurements of star-shaped
oligomers.
(L)-
Ph(3)-
NPh
TA(TL)-
Ph(3)-
CBZ
N(TL)-
Ph(3)-NPh
TA(TL)-
Ph(3)-NPh
Compounds
λ a /nm (ε)
405(0.77)
417,443
404(0.64)
421, 444
403
429(1.74)
443
427(1.65)
461
399(1.40)
430
20. L. Guo, K. F. Li, M. S. K. W. Wong, Chem. Commun. 49, 3597, (2013)
21. P. L.Wu, X. J. Feng, M. S. Wong, J. Am. Chem. Soc. 131, 886–887, (2009)
max
λ a /nm
em
λ b /nm (ε)
max
423(1.35)
451
426(1.54)
510
399(1.42)
459
λ b /nm
em
λ d / nm
max
λ d /nm
em
Φ a
427
427
Insoluble
Insoluble
0.87c
428
457
591
0.85c
0.86c
463
0.90c
426
Tde/˚C
435
448
aaverageofthreeindependentmeasurementsusingtoluene,molarabsorption
coefficientε (×105×M-1·cm-1). baverage of three independent measurements
using chloroform, molarabsorption coefficientsε (×105×M-1·cm-1). cusing
Norharman (Φ330~390=0.58) as standard. daverage of two independent
e
measurements using DMF. determined by TGA analyzer with a heating rate
of 20˚C/min under nitrogen
Non Linear Optical Properties
Two-photon excited fluorescence will be achieved as to determine the 2PA
and 3PA cross-section as well as the frequency up-conversion efficiency when
the related instruments are repaired.
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