Maleimide fused boron-fluorine complexes: Synthesis, photophysical and electrochemical properties

Article abstract of DOI:10.1039/c5dt01339a

Novel boron fluorine complex molecules were designed and synthesized using the maleimide core moiety. Significant features such as a large Stoke shift, high quantum yield, and long range absorption and emission wavelengths were observed for these molecules. The lower LUMO level of these molecules indicates their potential application as electron transport materials. The optical band gap was calculated and compared by using UV-absorption edge, density functional theory and electrochemical studies, revealing the charge transfer characteristics.

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Maleimide fused Boron-Fluorine complexes: Synthesis, Photophysical and
electrochemical properties.
==Received 00th January 20xx,
Accepted 00th January 20xx
DOI: 10.1039/x0xx00000x
www.rsc.org/
†
a
†
a
a
Pranila B. Thale , Pravin N. Borase and Dr. Ganapati S. Shankarling* .
Novel Boron Fluorine complex molecules were designed and synthesized using maleimide core moiety. Significant features
such as large stoke shift, high quantum yield, long range absorption and emission wavelength were observed for these
molecules. The lower LUMO level of these molecules indicates their potential application as electron transport materials.
The optical band gap was calculated and compared by using UV- absorption edge, Density functional theory and
electrochemical studies, reveal the charge transfer characteristics.
B–N coordinate patterns have been efficiently synthesized. Only,
1
. Introduction:
1
few of these shows high emission efficiencies both in solution and
Boron dipyrromethene dyes (BODIPY) are most important
1
0
solid state. In recent years, incorporation of low electron density
fluorescent dyes as they have wide application in the field of energy
2
3
4
materials such as pyridine, quinoline into imide moiety to give
transfer cassettes , laser dyes , fluorescent indicators bio
1
1
5
6
7
boron fluorine complexes has been reported . These complexes
exhibit good optical properties, robust thermal stability and high
electron transporting properties which is required for organic light
emitting diodes.
labelling , photodynamic therapy and in dye sensitized solar cells .
These dyes have spectacular photophysical properties such as high
extinction coefficient, high fluorescence quantum yield, sharp
absorption and fluorescence spectra. The photophysical properties
can be easily tuned by structural modification which is an added
advantage to meet diverse application. But, the main drawback in
BODIPY dyes is their small Stokes shift which leads to self-
quenching and measurement error due to excitation and scattering
of light. They have compact ꢀ ꢁ ꢀ stacking in solid state, which
leads to greater molecular interaction resulting in fluorescence
Dye with solid state emissive properties and large stokes shift are in
12
demand for practical application in molecular switches and
13
OLED . Having this in mind, we have reported the synthesis and
fluorescence properties of novel non-pyrrolic boron fluorine
complexes based on maleimide derivatives. The synthesized
complexes show broad absorption, high Stokes shift and intense
fluorescence in solid as well as in the liquid state.
8
quenching . Owing to above drawback, non-pyrrolic BODIPY
9
analogue have attracted considerable interest in recent years. They
possess many advantages like readily available and cheap starting
material, large stokes shift and good photostability. Thus, new types
of fluorescent dyes based on borate complexes with N–B–O and N–
2
. Experimental Section:
2
.1 Materials:
All the chemicals were procured from Spectrochem and Merck
chemicals. and were used without purification. The spectroscopic
grade solvents were used in the study.
a
Dyestuff Technology Department,
Institute of Chemical Technology, Mumbai 400019, India.
Tel: 91ꢀ22ꢀ33612708, Fax: +91ꢀ22ꢀ33611020
Eꢀmail address: gsshankarling@gmail.com
2
.2 Instrumentation:
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1
The
H NMR spectra were recorded on Bruker 300 MHz characterized by different spectroscopic techniques such as HR-MS,
1
13
11
Spectrometer in CDCl
3
as
a
solvent in the presence of
H NMR, C NMR, B NMR and elemental analysis.
tetramethylsilane as internal standard. TLC was performed on TLC-
< Insert Figure:1>
Grade silica gel-G/UV 254 nm plate. The UV-visible spectra were Figure1: ORTEP view of compound BF3(I)
recorded on PerkinElmer LAMBDA 25 UV/VIS spectrophotometer at 3.1 X-ray crystal structure: By slow evaporation of the samples in
chloroform and acetone, single crystal of BF3(I) suitable for X-ray
room temperature using quartz cells with 1.0 cm path length. The
diffraction analysis were obtained. The crystal is monoclinic in
fluorescence spectra was obtained on Varian Cary Eclipse
1
nature with space group P2 /n. BF3(I) exhibits a slightly distorted
Flourimeter. Time resolved fluorescence measurements were tetrahedral geometry around boron atoms. The bond lengths of B4-
F1, B4-F2, B4-N1 and B4-N2 were 1.382(2), 1.377(2), 1.605(2) and
performed on a time correlated single photon counting system
°
1
.528(2) A. Bond angle around B atom were ranging from
from IBH with excitation by a pulsed light emitting diode. The
emission from the sample was collected at the right angle to the
direction of excited beam, at a magic angle polarisation (54.7). The
decay has been fitted to multiexponential functions by an iterative
°
°
1
07.08(9) to 112.2(1) . The crystal refinement data is shown in
Table S2.
The crystal structure of BF3(I) shows interesting supramolecular
interaction. The distance of supramolecular interaction are shown
in Table S1. In packing diagram C(29)-H(29)…..F(1), C(9)-H(9)…..F(1),
C(9)-H(9)…..O(4), C(14)-H(14) …..F(2) interactions form zigzag like
structure along c-axis (Fig.2). The non-covalent intermolecular
interaction provide rigid structure to inhibit planar ꢀ ꢁ ꢀ stacking in
crystal structure because of which solid state fluorescence is
observed.
1
4
reconvolution method using JY Horiba IBH DAS v6.0 software .
3
. Result and discussion:
3.1 Synthesis:
<
Insert Figure: 2 >
Figure 2: Packing diagram of BF3(I) (a) View along c-axis (b) View
along a-axis.
<
<
<
Insert Scheme: 1>
Insert Scheme: 2>
Insert Scheme: 3>
3
.2 Photophysical studies: The photophysical study of the Boron-
The synthetic procedure of compounds BF1, BF21 BF3(I), BF3(II) are
,
Fluorine (BF) compounds are shown in Table 1. In DCM, BF1, BF3(I),
BF3(II) show single absorption band at 403 nm, 402 nm, 402 nm
respectively whereas, BF21 shows two absorption bands at 439 and
shown in scheme 1, 2 and 3. Condensation of compound 3a with 2-
methylpyridine and 2-methylquinaldine was carried out with fused
2
ZnCl without any solvent in a sealed tube which gave compound 4
4
65 nm (fig.3a). The shift in absorption spectrum of BF21 is due to
and 5 in good yield. The yield of the products were 47% and 52%
respectively. The electron donating properties of 2-methylpyridine
and 2-methylquinoline reduce the reactivity of second carbonyl
group present at the opposite end of imide. Therefore, only mono
substituted derivative is formed predominantly. Similarly,
condensation of 3b with 2-methylpyridine gave compound 6 in 57%
yield. Two isomers of compound 6 were, directly used for further
larger conjugation system of quinoline compared to pyridine in BF1.
All the BF compounds shows intense and structured absorption
bands. Minor solvatochromism effect (fig.S10-fig.S13 Supporting
information) in the absorption band was observed which supports
∗
ꢀ
ꢁ ꢀ transition localized on the conjugated ring system.
<
Insert Figure: 3>
3 2
reaction. The compound 4, 5 react with BF .Et O in presence of N-
Figure 3: Normalized (a) absorbance (b) emission spectra of BF
compounds in DCM at 3µM concentration.
ethyl-N,N-diisopropylamine in dichloromethane (DCM) for 24 h to
give BF1, BF21 in yield of 42%, 44% respectively. Similarly,
compound 6 was reacted with N-ethyl-N,N-diisopropylamine and
<
Insert Figure: 4>
Figure 4: (a) Normalized absorption (A) and fluorescence spectra (F)
of compound BF21 in acetone solution at five different
concentrations (1) 1 µM (2) 1.5 µM (3) 2.0 µM (4) 2.5 µM (5) 3.0 µM
with λEx = 434 nm.
3 2
BF .Et O in DCM which gave two isomers. These were separated by
column chromatography. The structure of BF3(I) isomer was
confirmed by single X-ray crystallography data (fig 1). Since the
solubility of BF3(II) was less, we could not obtain a single crystal of
this compound. The structure of these compounds were fully
(
b) Normalized emission spectra of BF compounds in solid state.
Table 1: Optical properties of BF compounds.
Insert Table: 1 >
<
2
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The photoluminescence of the BF compounds in different solvents monoexponential decay function with lifetime in the range of 1.08-
was studied at room temperature. Excitation of these compounds 2.86 ns (fig.S6-fig.S9 Supporting information)
shows green to blue fluorescence. The normalized emission spectra
Table 2: Quantum yield (Φ
compounds in different solvents (DCM, Acetone, Acetonitrile) and
(b). In DCM, BF1, BF3(I), BF3(II) show single emission band at 478 fluorescence lifetime (ꢂ) in DCM.
F F
), energy yield of fluorescence (E ) of BF
of the BF compounds in DCM at 3µM concentration are shown in fig
3
nm, 533 nm, 535 nm respectively whereas, BF21 shows two
emission bands at 479 and 509 nm. The normalized spectra of BF21 In order to confirm charge transfer characteristic of these
fig.4a) in acetone at five different concentrations show minimum compounds, difference between the ground state and excited state
<
Insert table: 2>
(
overlap between absorbance and emission band leading to larger dipole moment ꢃμ
ꢁ μ
ꢆꢇis calculated by Lippert and Mataga
ꢄ
ꢅ
1
5
Stokes shift. The absorption and emission spectra display mirror equation as follows .
symmetry, which indicate, the main bands correspond to S -S
0
1
ꢔ
ꢌ
ꢃꢐ
ꢑ
ꢒꢐ
ꢓ
ꢆ
ꢈν ꢇ–ꢇν ꢋ = ꢃ∆ꢏꢆ
+ ꢗꢘꢙꢚꢛꢜꢙꢛꢁ (1)
ꢉ
ꢊ
ꢖ
transition. Whereas, BODIPY shows maximum overlap between
absorbance and emission band. The Stokes shift, oscillator strength
and quantum yield are the important properties of fluorescent
compounds. Stokes shift indicates the difference in the properties
ꢍꢎ
ꢕ
Where h is Planck’s constant, c is velocity of light, (∆f) is solvent
polarizability parameter and a is the Onsager radius of the dipole-
solvent interaction sphere. The Onsager radius of the compound is
estimated from ground state optimized structure using Turbomole-
V6.6 program.
and structure of the compound between ground state S
excited state S . The quantum yield (Φ ) and energy yield of
fluorescence (E ) are listed in Table 2. Compared to smaller Stokes
0
and first
1
F
F
shift and insensitivity to the solvents of most BODIPY, larger Stokes The solvent polarizability (∆f) is calculated by following equation (2)
shift and remarkable spectral changes are observed in the solvents as shown in Table. S3 (supporting information).
for these compounds. The emission spectra of BF1, BF3(I), BF3(II)
ꢔ
Ɛꢒꢝ
ꢟ
ꢒꢝ
ꢃ∆ꢏꢆ =
ꢁ
ꢞꢝꢁꢁ. (2)
are solvent dependent. In toluene, BF1, BF3(I), BF3(II) showed
emission maxima at 474nm, 501nm and 501nm respectively
whereas, in a polar solvent like methanol, the compounds showed
emission maxima at 520 nm, 568 nm and 573 nm respectively.
These compounds display positive solvatochromic effect, decrease
in fluorescence quantum yield and increase in Stokes shift with
increase in the solvent polarity which explains the intersystem
charge transfer (ICT) process. In polar solvent, the dipole moment
of the molecule is enhanced upon excitation due to electron density
redistribution. Hence the excited state is more stabilized in polar
solvent due to stronger interaction with the dipole moment of
solvents. Whereas, BF21 does not show solvatochromism, as there
is small difference between ground state and excited state dipole
moment of these molecule. This is illustrated by Lippert-Mataga
equation later.
ꢌƐꢞꢝ
ꢌꢟ
ꢔ
The graph of Stokes shift (ν
A
F
– ν ) v/s solvent polarizability (∆f)
shows a linear relationship with the substantial slope which
illustrate the ICT process fig 5(b). From the slope of the graph, the
difference between the ground state and excited state dipole
moment ꢃμ ꢁ μ ꢆ is calculated (Table 3). The dipole moment
ꢄ
ꢅ
difference of BF3(I) and BF3(II) is more than BF1, BF21 which
indicates that these compounds are more polarized in the excited
F
state. The graph of Φ v/s (∆f) shows that the quantum yield
decreases with increase in the solvent polarity fig 5(a). The near
independence of Stokes shift on solvent polarity in BF21 with
substantial lower value of the slope (Table.3) indicates that the
permanent dipole moment (if any) are similar in the ground and
excited state.
Table 3: Ground state and excited state dipole moment difference
All BF compounds have noticeable solid-state emissions, which ꢃμ
ꢁ μ
ꢅ
ꢆ of BF compounds.
Insert Table: 3>
Insert Figure: 5>
ꢄ
cover a wide range of 431-670 nm (fig.4b) while, BODIPY dyes show
fluorescence in their solid state. Time resolved emission of these
dyes were studied and fluorescence lifetime (ꢂ) was determined by
Time-correlated Single photon counting (TCSPC). These dyes gave
<
<
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Fig 5(a): Plot of ΦF v/s (∆f) of BF compounds (DCM, Acetone, 325°C because of the presence of naphthyl ring on the anhydride
Acetonitrile). (b) Plot of Stokes shift (ν – ν ) v/s solvent
polarizability (∆f) of BF compounds in various solvents.
A
F
core moiety.
3
.3 Electrochemical studies: The electrochemical properties of BF In order to investigate the photo stability, 10 ppm solutions of BF
compounds were determined by cyclic voltammetry in compounds in acetonitrile were subjected to UV irradiation (254
-1
2
dichloromethane (DCM) at a scan rate of 100 mVs using tetrabutyl nm, 0.025W/cm ) for 500 min (fig.7). The kinetics of photo
ammonium hexafluorophosphate (TBAPF
as supporting degradation was monitored spectroscopically. It was found that
electrolyte. Potential was standardized with ferrocene-ferrocenium there is no change in optical density for all the compounds under
6
)
+
18
couple (Fc/Fc ) as an internal reference vs Ag/AgNO
3
. The cyclic study. This indicates that they have good photo stability which is
voltammograms of all compounds are illustrated in fig 6. and their important for their application in photo electronics.
electrochemical properties are summarized in Table 3. The
<
Insert Figure 7:>
corresponding energy levels of highest occupied molecular orbital
HOMO) and lowest unoccupied molecular orbital (LUMO) for BF
Figure 7: Change in optical density of BF compounds v/s time (min)
on irradiation with UV light (0.025W/cm ).
2
(
compounds are calculated from the onset of the oxidation and
reduction peaks. As predicted in the Table.4, the calculated HOMO
values were ranging from -6.16 to - 6.02 eV which are lower than
3
.4 Theoretical studies: To understand the electronic properties,
molecular orbital calculation were carried out by Turbomole-V6.6
program using density functional theory (DFT) (B3LYP as functional
those of BODIPY (-5.45eV) and Alq (-5.7 eV). The electron affinity
19
3
and def-SVP basis set) . The ground state electron density
values (LUMO level) were –3.26 to - 2.84 eV which are close to the
distribution of HOMO and LUMO are illustrated in fig. 8 and the
energy difference is presented in Table 4. The ꢀ electron densities
in HOMO of BF1 and BF21are spread over part A while, their ꢀ
electron densities in their LUMO are mainly localized on the part B.
The electron densities in HOMO of BF3(I), BF3(II) are localized on
the electron rich Napthyl ring part A whereas, electron densities in
the LUMO level are entirely shifted to part B. Therefore,
intermolecular charge transfer from part A to part B in BF
compounds can be explained, which could partly explain their
1
6
17
3
LUMO level of BODIPY (-3.05 eV) and Alq (-2.8 eV) . From the
above studies, it is clear that BF compounds have better electron
accepting features and have potential as an electron transport
material in OLEDs. For better understanding, we have compared the
values of HOMO, LUMO level, band gap by DFT and UV studies
(Table.4). The results are in good agreement with the experimental
and theoretical calculations.
<
Insert Figure: 6>
Figure 6: Cyclic voltammograms of BF compounds measured in broad absorption band and larger stokes shift. The calculated
6
DCM solution, containing 0.1 M TBAPF at 20°C. Ferrocene was used
HOMO-LUMO band gap of BF1 was larger than that of BF21 which is
consistent with the trend observed in the spectra.
as an internal standard, and potential was calculated relative to the
+
SCE assuming E1/2 (Fc/Fc ) to be +0.43.
Table 4: Electronic states (HOMO/LUMO levels) values and energy
gap (eV).
<
Insert Figure: 8 >
<
Insert Table 4:>
Figure 8: Diagram showing HOMO and LUMO level of BF
compounds.
V : Value from cyclic voltammetry; V : Value from MO calculation;
cv
ca
v
uv= Value obtained from UV-vis absorption edge studies.
4
. Conclusion: In summary, we have successfully synthesized
Thermal stability of BF compounds was investigated by thermo
gravimetric analysis (TGA) as shown in fig.S14 (Supporting
information). Thermal stability is defined as temperature up to
which 95% of the composition of the compound remains stable.
Stepwise ramping up to 600°C at 10°C/minute was performed in
nitrogen atmosphere. The change in weight of the compound was
measured as a function of temperature. The Compound BF1, BF21
were stable up to 275°C whereas, BF3(I), BF3(II) were stable up to
novel Boron-fluorine molecules with longer wavelength absorption
and emission by introducing methylpyridine and methylquinoline
group at the carbonyl position of maleimide derivative. The
synthesized derivatives have longer absorption, emission
wavelength, high quantum yield and large Stokes shift. Intense solid
state fluorescence, thermally robust nature and low LUMO level of
4
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synthesized molecules indicate their potential for use in OLED (d) L. Gai, H. Lu, B. Zou, G. Lai, Z. Shen, and Z. Li, RSC Adv., 2012, 2,
8
840.
material.
(
9) D. Frath, J. Massue, G. Ulrich, and R. Ziessel, Angew. Chemie -
Acknowledgment:
Int. Ed., 2014, 53, 2290–2310.
Authors are greatly thankful to Prof. Anindya Datta IIT, Bombay for
(
10) (a) W. Li, W. Lin, J. Wang, and X. Guan, Org. Lett., 2013, 15,
providing fluorescence decay measurement instrument facility. 1768–1771. (b) D. Frath, A. Poirel, G. Ulrich, A. De Nicola, and R.
Ziessel, Chem. Commun., 2013, 49, 4908. (c) J. Massue, D. Frath, P.
Retailleau, G. Ulrich, and R. Ziessel, Chem. - A Eur. J., 2013, 19,
Authors are also thankful to UGC-SAP, Technical Education Quality
Improvement Programme (TEQUIP), for providing financial 5375–5386. (d) K. Benelhadj, J. Massue, P. Retailleau, G. Ulrich, and
1
R. Ziessel, Org. Lett., 2013, 15, 2918–2921.
assistance and SAIF IIT, Bombay for recording H NMR and
elemental analysis.
(
11) (a) Y. Zhou, Y. Xiao, D. Li, M. Fu, J. Org. Chem., 2008, 73, 1571–
1
4
574. (b) J. Feng, B. Liang, D.Wang, L. Xue, X. Li, Org. Lett.,2008, 10,
437-4440.
Notes and references:
(
12) S. J. Lim, B. K. An, D. J. Sang, M. A. Chung, and Y. P. Soo, Angew.
Chemie - Int. Ed., 2004, 43, 6346–6350.
(
1) (a) A. Loudet, K.Burgess, Chem. Rev., 2007, 107, 4891-4932. (b)
G. Ulrich, R. Ziessel, A. Harriman, Angew. Chemie - Int. Ed., 2008, 47,
184-1201. (c) L. C. D. D. L. Rezende, S. Emery, F. Emery, Orbital-The (13) (a) H. Sasabe, J. Kido, Chem. Mater., 2011, 23, 621–630. (b) a.
Electron. J. Chem., 2013, 5, 62-83. (d) Y.Ni, J. Wu, Org. Biomol. Hepp, G. Ulrich, R. Schmechel, H. Von Seggern, R. Ziessel, Synth.
1
Chem., 2014, 12, 3774-3791.
Met., 2004, 146, 11–15. (c) S. J. Yeh, M. F. Wu, C. T. Chen, Y. H.
Song, Y. Chi, M. H. Ho, S. F. Hsu, C. H. Chen, Adv. Mater., 2005, 17,
2
85–289. (d) S. W. Wen, M. T. Lee, C. H. Chen, IEEE/OSA J. Disp.
(
3
2) M.Benstead, G. H. Mehl, R. W. Boyle, Tetrahedron, 2011, 67,
573-3601.
Technol.,2005, 1, 90–99.
(
1
14) D. Panda, S. Khatua, and A. Datta, J. Phys. Chem. B, 2007, 111,
648–1656.
(
3) T. L. Arbeloa, F. L. Arbeloa, I. L. Arbeloa, I. Garcıa
Costela, R. Sastre, F. Amat-Guerri, Chem. Phys. Lett., 1999, 299,
15-321.
́
- Moreno, a
3
(
15) M. Shaikh, J. Mohanty, P. K. Singh, a. C. Bhasikuttan, R. N.
Rajule, V. S. Satam, S. R. Bendre, V. R. Kanetkar, H. Pal, J. Phys.
Chem. A, 2010, 114, 4507–4519.
(
4) (a) J. L. Bricks, A. Kovalchuk, C. Trieflinger, M. Nofz, M. Büschel,
A. I. Tolmachev, J. Daub, K. Rurack, J. Am. Chem. Soc., 2005, 127,
3522–13529. (b) K. Yamada, Y. Nomura, D. Citterio, N. Iwasawa, K.
1
Suzuki, J. Am. Chem. Soc., 2005, 127, 6956–6957. (c) A. Coskun, E. (16) Y. Zhou, Y. Xiao, S. Chi, X. Qian, Org. Lett., 2008, 10, 633–636.
U. Akkaya, J. Am. Chem. Soc., 2006, 128, 14474–14475. (d) A.
Coskun, M. D. Yilmaz, E. U. Akkaya, Org. Lett., 2007, 9, 607–609. (e)
(
17) P. E. Burrows, Z. Shen, V. Bulovic, D. M. McCarty, S. R. Forrest,
N. Boens, V. Leen, W. Dehaen, Chem. Soc. Rev., 2012, 41, 1130–
172.
J. A. Cronin, M. E. Thompson, J. Appl. Phys., 1996, 79, 7991-8006.
1
(
18) (a) T. Konstantinova, R. Lazarova, A. Venkova, V. Vassileva,
Polym. Degrad. Stab., 2004, 84, 405–409. (b) T. Konstantinova, R.
6) A. Kamkaew, S. H. Lim, H. B. Lee, L. V. Kiew, L. Y. Chung, K. Lazarova, V. Bojinov, Polym. Degrad. Stab., 2003, 82, 115–118.
(
5) M. Sameiro, T. Gonçalves, Chem. Rev., 2009, 109, 190–212.
(
Burgess, Chem. Soc. Rev., 2012, 42, 77–88.
(
19) (a) TURBOMOLE V6.6 (2014), A Development of University of
Karlsruhe and Forschungszentrum Karlsruhe GmbH, 1989–2007,
TURBOMOLE GmbH, since 2007, available from
(7) (a) S. Erten-Ela, M. D. Yilmaz, B. Icli, Y. Dede, S. Icli, E. U. Akkaya,
Org. Lett., 2008, 10, 3299–3302. (b) T. Rousseau, A. Cravino, T.
Bura, G. Ulrich, R. Ziessel, J. Roncali, Chem. Commun. (Camb)., 2009,
http://www.turbomole.com (b) O.T. Ahlrichs, R. Ahlrichs, Efficient
1673–1675.
molecular numerical integration schemes, J. Chem. Phys. 1995,102,
3
46–354. (c) M. Von Arnim, R. Ahlrichs Performance of parallel
(
8) (a) T. Ozdemir, S. Atilgan, I. Kutuk, L. T. Yildirim, A. Tulek, M. TURBOMOLE for density functional calculations, J. Comput. Chem.
Bayindir, and E. U. Akkaya, Org. Lett., 2009, 11, 2105–2107. (b) D. 1998, 19, 1746-1757.
Zhang, Y. Wen, Y. Xiao, G. Yu, Y. Liu, and X. Qian, Chem. Commun.
(Camb)., 2008, 4777–4779. (c)H. Lu, Q. Wang, L. Gai, Z. Li, Y. Deng,
X. Xiao, G. Lai, and Z. Shen, Chem. - A Eur. J., 2012, 18, 7852–7861.
This journal is © The Royal Society of Chemistry 20xx
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Figure Caption:
Scheme 1:
Scheme 2:
Scheme 3:
Figure1: ORTEP view of compound BF3(I).
Figure 2: Packing diagram of BF3(I) (a) View along cꢀaxis (b) View along aꢀaxis.
Figure 3: Normalised (a) absorbance (b) emission spectra of BF compounds in DCM at 3µM
concentration.
Figure 4: (a) Normalised absorption (A) and fluorescence spectra (F) of compound BF21 in
acetone solution at five different concentrations (1) 1 µM (2) 1.5 µM (3) 2.0 µM (4) 2.5 µM
(
5) 3.0 µM with λ = 434 nm.
Ex
(b) Normalised emission spectra of BF Compounds in solid state.
F
Fig 5: (a) Plot of Φ v/s (∆f) of BF compounds (DCM, Acetone, Acetonitrile). (b) Plot of
Stokes shift (ν – ν ) v/s solvent polarizability (∆f) of BF compounds in various solvents.
A
F
Figure 6: Cyclic voltammograms of BF compounds measured in DCM solution, containing
.1 M TBAPF at 20°C. Ferrocene was used as an internal standard, and potential was
calculated relative to the SCE assuming E (Fc/Fc ) to be +0.43.
0
6
+
1/2
Figure 7: Change in optical density of BF compounds v/s time (min) on irradiation with UV
2
light (0.025W/cm ).
Figure 8: Diagram showing HOMO and LUMO level of BF compounds.

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Figure1: ORTEP view of compound BF3(I).
Figure 2: Packing diagram of BF3(I) (a) View along cꢀaxis (b) View along aꢀaxis.

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(a)
(
b)
Figure 3: Normalised (a) absorbance (b) emission spectra of BF compounds in DCM at 3µM
concentration.
Figure 4: (a) Normalised absorption (A) and fluorescence spectra (F) of compound BF21 in
acetone solution at five different concentrations (1) 1 µM (2) 1.5 µM (3) 2.0 µM (4) 2.5 µM
(5) 3.0 µM with λEx = 434 nm.
(b) Normalised emission spectra of BF Compounds in solid state.

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Fig5: (a) Plot of Φ
F
v/s (∆f) of BF compounds (DCM, Acetone, Acetonitrile). (b) Plot of
F
) v/s solvent polarizability (∆f) of BF compounds in various solvents.
Stokes shift (ν – ν
A

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Figure 6: Cyclic voltammograms of BF compounds measured in DCM solution, containing
.1 M TBAPF at 20°C. Ferrocene was used as an internal standard, and potential was
0
6
+
calculated relative to the SCE assuming E1/2 (Fc/Fc ) to be +0.43.
Figure 7: Change in optical density of BF compounds v/s time (min) on irradiation with UV
2
light (0.025W/cm ).

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Figure 8: Diagram showing HOMO and LUMO level of BF compounds.

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Table 1: Optical properties of BF compounds.
F
Table 2: Quantum yield (Φ ), energy yield fluorescence (E ) of BF compounds in different
F
solvents (DCM, Acetone, Acetonitrile) and fluorescence lifetime (ꢀ) in DCM.
.
Table 3: Ground state and excited state dipole moment difference ꢁμ − μ ꢄ of BF
ꢂ
ꢃ
compounds.
Table 4: Electronic states (HOMO/LUMO levels) values and energy gap (eV).
Table 1: Optical properties of BF compounds.
λab
nm)
Ɛ
λF
ꢀ1
max
ꢀ1
Compound Solvent
ꢀ1
ν
A
ꢀ ν
F
(cm )
ꢅ
(
(M cm ) (nm)
Toluene
Dioxane
THF
DCM
Acetone
ACN
410
404
404
403
400
395
394
23100
37600
30800
40700
36600
26000
84000
474
474
476
478
478
479
520
3293
3655
3744
3893
4079
4440
6150
0.44
0.66
0.61
0.77
0.73
0.49
1.80
BF1
Methanol
Toluene
445
42100
486
1895
0.66
Dioxane
THF
DCM
Acetone
ACN
Methanol
Toluene
Dioxane
THF
DCM
Acetone
ACN
Methanol
Toluene
Dioxane
THF
442
441
439
436
434
432
411
407
404
402
400
401
395
413
406
405
402
399
396
395
43700
37700
33500
40300
30400
46100
55200
19300
27300
36900
33800
26800
49200
21900
38100
31400
29400
24500
30000
16700
484
482
479
478
477
481
501
501
508
533
537
549
568
501
510
518
535
538
557
573
1963
1928
1902
2015
2077
2358
4370
4609
5067
6113
6378
6722
7710
4252
5022
5386
6184
6475
7299
7864
0.38
0.65
0.54
0.69
0.62
1.08
1.27
0.37
0.76
0.73
0.68
0.52
1.41
0.38
0.88
0.59
0.54
0.46
0.59
0.34
BF21
BF3(I)
BF3(II)
DCM
Acetone
ACN
Methanol

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Table 2: Quantum yield (Φ
F F
), energy yield fluorescence (E ) of BF compounds in different
solvents (DCM, Acetone, Acetonitrile) and fluorescence lifetime (ꢀ) in DCM.
Compound
BF1
Solvent
DCM
Acetone
ACN
DCM
Acetone
ACN
DCM
Acetone
ACN
DCM
Acetone
ACN
Φ
F
E
F
ꢀ
1.86
(ns)
0.56
0.30
0.17
0.54
0.27
0.45
0.26
0.22
0.11
0.16
0.12
0.09
0.48
0.25
0.14
0.43
0.24
0.20
0.20
0.16
0.08
0.12
0.09
0.06
1
.23
BF21
BF3(I)
BF3(II)
2.86
1.08
Table 3: Ground state and excited state dipole moment difference ꢁμ − μ ꢄ of BF
ꢂ
ꢃ
compounds.
Onsager
radius (A°)
ꢁμ − μ ꢄ
ꢂ ꢃ
Compound Slope
D
BF
BF
1
1779.00
270.00
3079.00
3255.00
7.05
7.58
7.69
7.66
0.78
0.34
1.18
1.20
2
BF (I)
3
BF (II)
3
Table 4: Electronic states (HOMO/LUMO levels) values and energy gap (eV).
LUMO (eV)
HOMO (eV)
E
g
(eV)
Compound
Vcv
Vca
Vcv
Vca
Vcv
Vca
Vuv
BF1
ꢀ2.84
ꢀ3.04
ꢀ2.95
ꢀ2.81
ꢀ6.13
ꢀ6.15
ꢀ6.06
ꢀ6.05
3.29
3.11
3.11
3.24
2.68
2.54
2.78
2.67
ꢀ2.86
ꢀ3.26
ꢀ2.90
ꢀ2.84
ꢀ6.16
ꢀ6.15
ꢀ6.10
ꢀ6.02
3.29
2.88
3.20
3.18
BF21
BF3(I)
BF3(II)
Vcv: Value from cyclic voltammetry; Vca: Value from MO calculation; Vuv = Value obtained from UVꢀ
vis absorption edge studies.