Synthesis, characterization and photo physical-theoretical analysis of D-π-A compounds. 2. Chain length effect through even-odd effect on the photophysical properties

Article abstract of DOI:10.1016/j.dyepig.2017.07.069

In the continuous search for new compounds for solar devices, the family of dipolar D-π-A molecules, which have a donor (D) and an acceptor (A) charge joined by a conjugate bridge, have been the focus of attention in the recent years due their different properties. As we have shown before, there is a connection between the geometry of molecules based on tertiary asymmetric amines and their quantum yield. In the current work, four new compounds based on the same backbone molecule ((E)-2-cyano-3-(5-((E)-2-(9,9-diethyl-7-(phenylamino)-9H-fluoren-2-yl)vinyl)thiophen-2-yl)acrylic acid), but with different substituent, were synthesized. It is shown that the chain-size of the substituent group modifies the quantum yield. The news substituents introduced are a propyl (M8-3), butyl (M8-4), pentyl (M8-5) or hexyl (M8-6) group. In general, it was possible to see that the new substituents were able to increase their performances. Furthermore, an odd-even substituent effect, between propyl/pentyl and butyl/hexyl, was found and the theoretical geometrical data was able to follow the trend. However, theoretically, this substituent effect was inverted in the case of M8-3 and M8-4, which may be due to the disappearance in the emission patterns of an excited state close to 450 nm (at λ₂), as it was shown in the experimental data. The most suitable behaviour belongs to [(E)-2-cyano-3-(5-((E)-2-(9,9-diethyl-7-(phenyl(propyl)amino)-9H-fluoren-2-yl)vinyl)thiophen-2-yl)acrylic acid] (M8-3). M8-3 has the highest quantum yields on average in all studied solvents; even higher than the last reported compounds with methyl (M8-1) and ethyl (M8-2) groups. Theoretically, the most likely explanation is that the dihedral angle formed between the carbonyl acceptor and nitrogen electron donor (Aryl-CO), should be as small as the molecule M8-3. This isolated compound has an average quantum yield including all solvents of 58.1% (average value), showing that a long group is not necessary to improve the performance.

Full text of DOI:10.1016/j.dyepig.2017.07.069

Accepted Manuscript
Synthesis, characterization and photo physical-theoretical analysis of D-π-A
compounds. 2. chain length effect through even-odd effect on the photophysical
properties
E. Ortega, A. Ramirez, L. Cattin, F.R. Díaz, M.A. del Valle, J.C. Bernède
PII:
S0143-7208(17)31392-X
10.1016/j.dyepig.2017.07.069
DYPI 6158
DOI:
Reference:
To appear in: Dyes and Pigments
Received Date: 20 June 2017
Revised Date: 28 July 2017
Accepted Date: 30 July 2017
Please cite this article as: Ortega E, Ramirez A, Cattin L, Díaz FR, del Valle MA, Bernède JC, Synthesis,
characterization and photo physical-theoretical analysis of D-π-A compounds. 2. chain length effect
through even-odd effect on the photophysical properties, Dyes and Pigments (2017), doi: 10.1016/
j.dyepig.2017.07.069.
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ACCEPTED MANUSCRIPT
HOMO
LUMO
60
55
50
45
40
35
60
55
50
45
40
35
M8-3
M8-3
M8-5
M8-5
M8-4
M8-4
M8-6
M8-6
169,0 169,5 170,0 170,5 171,0 171,5 172,0 172,5
Al-CO (Degrees)
18,5 19,0 19,5 20,0 20,5 21,0 21,5 22,0 22,5
Ar-CO (Degrees)
Dihedral angle
Even and odd substituent effect on ΦF

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Synthesis, characterization and photo physical-theoretical analysis of D-π-A compounds. 2.
Chain length effect through even-odd effect on the photophysical properties
E. Ortegaa, A. Ramireza, L. Cattinb, F. R. Díazc, M. A. del Vallea*, J. C. Bernèded*
a Pontificia Universidad Católica de Chile, Av. V. Mackenna 4860-Macul, BP 7820436, Santiago, Chile.
b Institut des Matériaux Jean Rouxel (IMN), Université de Nantes, CNRS, 2 rue de la Houssinière, BP
32229, 44322 Nantes cedex 3, France.
c
Departamento de Química y Biología, Facultad de Ciencias Naturales, Universidad de Atacama,
Copayapu 485, Copiapó, Chile.
d
MOLTECH-Anjou, CNRS, UMR 6200, Université de Nantes, 2 rue de la Houssinière, BP 92208,
Nantes, F-44000 France.
Abstract
In the continuous search for new compounds for solar devices, the family of dipolar D-π-A molecules,
which have a donor (D) and an acceptor (A) charge joined by a conjugate bridge, have been the focus
of attention in the recent years due their different properties. As we have shown before, there is a
connection between the geometry of molecules based on tertiary asymmetric amines and their
quantum yield. In the current work, four new compounds based on the same backbone molecule ((E)-
2-cyano-3-(5-((E)-2-(9,9-diethyl-7-(phenylamino)-9H-fluoren-2-yl)vinyl)thiophen-2-yl)acrylic acid),but with
different substituent, were synthesized. It is shown that the chain-size of the substituent group modifies
the quantum yield. The news substituents introduced are a propyl (M8-3), butyl (M8-4), pentyl (M8-5)
or hexyl (M8-6) group. In general, it was possible to see that the new substituents were able to
increase their performances. Furthermore, an odd-even substituent effect, between propyl/pentyl and
butyl/hexyl, was found and the theoretical geometrical data was able to follow the trend. However,
theoretically, this substituent effect was inverted in the case of M8-3 and M8-4, which may be due to
the disappearance in the emission patterns of an excited state close to 450 nm (at λ2), as it was shown
in the experimental data. The most suitable behaviour belongs to [(E)-2-cyano-3-(5-((E)-2-(9,9-diethyl-
7-(phenyl(propyl)amino)-9H-fluoren-2-yl)vinyl)thiophen-2-yl)acrylic acid] (M8-3). M8-3 has the highest
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quantum yields on average in all studied solvents; even higher than the last reported compounds with
methyl (M8-1) and ethyl (M8-2) groups. Theoretically, the most likely explanation is that the dihedral
angle formed between the carbonyl acceptor and nitrogen electron donor (Aryl-CO), should be as
small as the molecule M8-3. This isolated compound has an average quantum yield including all
solvents of 58.1% (average value), showing that a long group is not necessary to improve the
performance.
Keywords: Dye, quantum efficiency, dihedral angle, chain length effect, odd-even substituent effect.
Corresponding authors: María Angélica del Valle, mdvalle@uc.cl and Christian Bernède,
jean-christian.bernede@univ-nantes.fr
1. Introduction
Due to their promising optical properties for use in optoelectronic devices, D-π-A compounds, which
have a donor (D) and an acceptor (A) joined by a conjugate bridge, are attracting increasing scientist
interest. Dyes based on this backbone, ((E)-2-cyano-3-(5-((E)-2-(9,9-diethyl-7-(phenylamino)-9H-
fluoren-2-yl)vinyl)thiophen-2-yl)acrylic acid) (fig.1), were used with some success in organic solar cells
[1]. This type of compounds has a donor moiety, an electron rich component, generally a triarylamine,
oligothiophene or some heterocycles moiety. On the other hand, acceptors have two functions, firstly
to attract the electron density after light absorption and to deliver it to the anchor material and second
to chemically bond over this material (adsorption). Classical structures are fractions of cyanoacetic
acid [2], fluorene, aniline and thiophenes fractions have commonly been used because of their photo-
electrochemical properties [3-7]. Previously we reported the synthesis and characterization of four D-π-
A -type dyes, in two series: alkyl- and alloy-substituted, M8-n and M8-On (Figure 1, R = Me (n=1) or Et
(n=2)) [2]. The alkyl substituted series exhibited good photophysical properties. We showed that these
D-π-A compounds have a connection between their geometry and quantum yield values. Therefore, in
the present work we have synthesized four new molecules, which keep the structure and only increase
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the substituent chain-size. Actually, in our previous work, the molecules showed an excellent
performance, only in specifics solvents, such as 1, 4 dioxane. The quantum yield (in average) does not
reach high values or the behaviour is not continuous on the studied solvents due the short substituent.
In this work; the aim is to improve this behaviour, introducing new longer substituent which could be
able to increase the performance in different solvents, even in polar solvents usually useful in solar cell
manufacturing for instance. These new organic compounds were tested, in terms of photophysical
properties, to obtain information about their behaviour [9-13]. Synthesis and characterization via UV-
vis. spectroscopy, elemental analysis, NMR, FT-IR, mass and fluorescence spectroscopy of four new
dyes: M8-3, M8-4, M8-5 and M8- 6 (Fig. 1a), were performed (Table 1). The study, both photophysical
and theoretical, was conducted using eight solvents, sorted in ascending order relative to their polarity
index: dichloromethane (DCM), tetrahydrofuran (THF), ethyl acetate (ETA), such as 1,4-dioxane (DIO),
acetone (ACT), acetonitrile (ACN), dimethylformamide (DMF) and dimethylsulfoxide (DMSO). In DCM
and ACN, studies were qualitative since the dyes are not completely soluble therein. We show there is
a relationship between the substituent length and the quantum yield. There is a difference between the
molecules with methyl, propyl and pentyl substituents and ethyl, butyl and hexyl substituents.
Theoretically, it is possible to follow each different experimental trend. This effect has been named
ODD-EVEN effect, because it only occurs between the different substituents, the even ones (M8-2, 4
and 6) and the odd ones (M8-1, 3, 5) (Fig. 1).
2. Materials and methods
In general, the conditions are the same as reported in our previous work [2]. All solvents used in both
syntheses and subsequent analyses were high purity anhydrous, and purchased from Aldrich.
Synthesis methods are shown in “dyes synthesis” section (SI-2. Section 2). FT-IR spectra were
recorded on a Bruker, VECTOR 22 model spectrophotometer (Spectra available on the SI-3. Section
3). NMR spectra were recorded on a Bruker 400 MHz Spectrometer (Spectra available on the SI-3.
Section 3.). Subsequently, measurements of solutions of each dye, concentrations between 0.5 and 3
1
mmol L , were used for quantum yield determinations. UV-Vis spectra were recorded on an Agilent
spectrophotometer and fluorescence on a HORIBA Scientific Fluoromax-4spectrofluorometer. The
samples have been prepared with KBr (for solid ones), and KBr liquid film (for oils), the resolution used
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-1
-1
is 16 cm with 32 scans and a range of measurement of 600-4500 cm . For mass spectrometry, a
Triple Quad, 4500 AB SCIEX-mass spectrometer was employed. Theoretical calculations were per-
formed with the Gaussian 09 program, utilizing the density functional theory (DFT), specifically, the
B3LYP method and 6-31 g(d) basis set for optimizations. As for photo-physical, calculations were
performed using time dependent methods, TD-DFT, to obtain three of the most important dyes
intensities [1, 2].
3. Results and discussion
3.1 Dye synthesis
The synthetic route to obtain these products is signalled in the scheme 1. The synthesis of these new
products is similar to that reported in our previous work [2], although in this case, to generate
compounds with longer substituent chains, the amine (reactant) in the of Buckwald-Hartwig reaction is
changed by N-propylaniline, N-butylaniline, N-pentylaniline and N-hexylaniline, respectively. As
already mentioned, details of synthetic methodology and classical characterization are given at
supplementary material (SI-2).IR and NMR spectra are also showed (SI-3).
3.2. Photophysical properties
3.2.1. UV-Vis spectrophotometry
Similar to the previously described M8-n series [2], two notable bands are shown in the UV-Vis region.
It can be seen that there is an hypsochromic effect of the absorption maxima of the n-π*
transition. (Table 2) [14].In solvents wherein the compounds were soluble, the molar extinction
coefficient (ε0) (Table 2) was determined and were similar to those of the previously studied
compounds, they have values in the 104 M-1 cm-1 range.
3.2.2 Fluorescence Spectroscopy
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In the emission or fluorescence spectra of the synthesized dyes, from 1 to 4 different bands can be
observed, depending on the solvent and the excitation wavelength. In this case, the fluorescence
patterns are obtained by excitation at two different wavelengths (λ1 and λ2). λ1, is the maximum
absorption wavelength (table 2).λ2, is a wavelength selected to measure quantum yield values. In
general, no clear trend between these maxima exists, even when it is compared with the increasing
polarity of the used solvent.
In all spectra, each molecule, shows different patterns, where 1 to 4 bands can be found. In table 3, it
a summary of the maxima and intensities are shown. The different bands are related to different
excited states, in particular, each one was labelled (ordered from lowest energy to highest energy), S1,
S2, S3 and S4, which have a value (in average) of 640, 600, 500 and 450 nm, all this according to the
reference [2]. The intensities are labelled from 1 to 3 or 4, where 1 is the highest and 3 or 4 the lowest.
When these molecules are excited at two different wavelengths, different patterns are obtained. When
they are excited at λ1 (Figs. 2 [a, b] and SI1.1, SI1.2, SI1.3 [a, b]), different bands are seen.
Nevertheless, when they are excited at different wavelength (Figs. 2 [c, d] and SI1.1, SI1.2, SI1.3 [c,
d]), a solvent-dependent change of the previous pattern occurs. As summary, in the tables 3 and
SI1.1, SI1.2, SI1.3, are the different values of each emission maximum. It is possible to see that only
M8-5 has an S4 state at λmax. Moreover, the appearance of S1 and S2 is common for all molecules. In
the other hand, at another wavelength (λ2), the quenching of S1 and S2 signals is common. The Föster
resonance energy transfer (FRET) effect is still appearing in these compounds, therefore this effect is
definitively associated with the molecular architecture D-π-A [1].In addition, the quenching of the first
two excited states (at λ2 excitation wavelength) can be attributed to the fact that the excited states (S1
and S2), do not generate stable excited complexes in the employed solvent [15-16].
3.2.3 Excited states polarity estimation, absorption and emission graphic analysis using
Lippert equation and Lippert−Mataga plots
To estimate the difference of dipole moment change of the compounds, the Lippert equation is used
(S0). Therefore, by plotting the Stokes shift (Table SI1.4) absolute value of all solvents vs. the dipolar
factor of the same solvent (Lippert-Mataga plot), the difference in dipole moment for each dye is
obtained from the respective slope [17-19].
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A plot of the Stokes shift (in frequency units (cm-1)) vs. dipolar solvent factor (So, Eq. 1), allows
inferring a high value slope (fig. 3[a, b, c, d]), indicating the dye presents a greater difference between
its ground state and excited states, which is ascribed to nitrogen nonbonding electron pair donation.
For the estimation of the polarity of the excited state, Onsager radius (a), is estimated as the ninth of
the distance between the carbon corresponding to carbonyl and nitrogen [2], currently 17.87 Å. The
difference of the dipole moment in this case corresponds to the difference between the ground state
and the excited state dipole moment. Having in mind the kind of transition occurring in these
molecules, the ground state is more polar than the excited state [20]. Ground state values are
estimated by performing theoretical calculations using the Gaussian 09 program and optimizing the
chemical structures [2].
As it has been seen in our previous work [2], the points in the graphs tend to diverge. Nevertheless,
this is not an isolated fact and other compounds show this behaviour [21]. In summary, the aim is to
compare, then this plot has been made to obtain some information related with substituents and only
qualitative information could be obtained. Comparing dipole moment difference of dyes (Table 4), M8-6
exhibits the largest difference as compared to the other dyes (among the molecules of this work). If it is
included two molecules from our last work (M8-1 and M8-2), it is possible to realize that the difference
decrease until M8-6. Therefore, the length of the N-alkyl chain has an inversely proportional relation
with the difference between these two states (ground and excited). In terms of state polarity, ground
and excited state increase progressively their polarity with the substituent chain length (not the case of
M8-6).
3.2.4 Quantum yield (ΦF)
For the determination of quantum yields, a comparative method reported by Williams et al. [22, 23],
using zinc phthalocyanine (ZnPc) as standard in a 1% pyridine solution in toluene (Eq. 1) was utilized.
For solvents where solubility is not total, such as DCM and ACN, the above method is used but as an
equation with unknowns not as an equation derived from a plot (Eq. 2).
(1)
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Equation 2 is used to determine quantum yields by Williams. ΦX refers to the quantum yield of the
sample and ΦST is the quantum yield of the reference standard, in this case 0.30 (30.0 %). Gradx is the
slope of integrated emission intensity vs. absorbance plot, for the sample and GradST the slope for the
standard. ηX and ηST, correspond to the refractive index of sample and standard solvent, respectively.
(2)
Equation 3, is used to determine quantum yields in solvents where the dye is not fully soluble. In this
case, ΦS refers to the quantum yield of the sample and ΦR is the quantum yield of the standard. S and
R Area stand for sample and standard integrated emission intensity, respectively. AbsR and AbsS,
correspond to sample and standard absorbance, ηS and ηR, stand for sample and standard solvent
refractive index, respectively.
As for the values of quantum yields (Table 5), they showed no linear relation with solvent polarity, but
some trends are possible to be found taking into account the main factors affecting fluorescence:
chemical structure, structural rigidity, temperature, solvent, pH and concentration effect [24]. For
measurements, temperature (room), structural rigidity, pH (not applicable) and low concentrations
(absorbance lower than 0.1 units) are kept constant. The chemical structure varies and the
modifications are mentioned in the introductory section. Different solvents were tried in order to
observe their responses. The comparison of compounds demonstrated that the quantum yield is not
proportional to neither substituent length nor to the polarity of the solvent (Table 5). It was observed
that, in general, in each studied solvent the molecules bear a relationship to viscosity. The solvents
showed a linear relationship between quantum yield and viscosity (fig. 4), attaining a maximum for DIO
and slightly decreasing for DMSO, the solvent with the highest viscosity (higher viscosities negatively
affect the quantum yield).
A general comparison of quantum yields between the previously reported M8-1,2 [2] and the new M8-
3, 4, 5, 6 molecules, shows that this yields tend to increase (on average) in the new series of
compounds
In consequence, increasing the alkyl group size favours quantum yield.
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The quantum yield results show values higher in non-polar solvent than polar solvent. An explanation
for this is that longer chains improve solubility, contact between molecules and chemical environment,
also the geometry in such a way that the excited states decay only in fluorescence [25-27] improving
yield. On average, M8-3 exhibits the largest quantum yield of the dye series, evidencing that it is
unnecessary to have such long chains in the molecular structure, as M8-6 with hexyl group, to
increase yields. Another important difference, on average (Table 6), is observed among compounds
M8-1, 3, 5 and M8-2, 4, 6. In all cases, the odd compounds have a higher yield than its next neighbour
even compounds (1>2, 3>4 and 5>6). In particular, it is possible to see (table 6), that M8-3 tends to
have the same quantum yield value (with a difference of 5.1 units) between polar and non-polar
solvents; being higher in non-polar solvent. Nevertheless, in the case of M8-4 this trend changes, this
value being higher in polar solvents (difference of 3.1 units).
3.3 Theoretical approach to molecular properties, dihedral angles and their relationship to
quantum yield.
Another way to find an answer to quantum yield values is to compare dihedral angles [2]. In this case,
the angle formed between the carbonyl acceptor and amine donor is compared, as an approximation
between these two groups, due the π-bridge linearity (fig. 5). In addition, theoretically the structure
shows this linearity among the different moieties involved in the π-bridge. This approximation is
because both, HOMO and LUMO orbitals situate around these functional groups (fig. 6 [a, b] for M8-3).
In this comparison, two possible angles exist, Aryl-CO, which refers to that formed between the
nitrogen-ring and carbonyl group, the second, Alkyl-CO, to the one formed between aliphatic chain-
nitrogen and carbonyl group. In table SI1.5, it is showed the values taken for both dihedral angles in
non-polar solvents for all the compounds into this family. M8-1 has the highest value. Separately, it is
difficult to find tendencies; nevertheless, it is possible to see the value change in M8-6. This could
have a relation with the break in the dipolar moment difference tendencies (table 4). A summary of
values is showed in the table SI 1.6. In general, values do not seem to change, whatever the different
solvents.
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On average, it was found Aryl-CO values are smaller in polar than in non-polar solvents and Alkyl-CO
values are bigger in polar than in non-polar solvents (table 7). This means, the geometrical factor has
an important effect or influence in quantum yield and all depends on the type of solvent. In this case, to
explain the experimental changes, it favours Alkyl-CO lower values and Aryl-CO higher values. As
quantum yield values, here a difference was found between even and odd chain length substituents.
However, the tendencies are diverse. For Aryl-CO values, M8-1 is bigger than M8-2, which is correct.
M8-3 is smaller than M8-4, which does not follow the tendency. M8-5 is higher than M8-6, which is
correct. Moreover, for Alkyl-CO values, M8-1 is smaller than M8-2, which is correct. M8-3 is bigger
than M8-4, which does not follow the trend. M8-5 is smaller than M8-6, which is correct. As summary,
only M8-3 and M8-4 do not follow the trend, for the rest, it is true. It is this fact together with the
disappearance of the state close to 450 nm (S4), at the moment to measure quantum yields (at λ2);
which could explain the different behaviour of M8-3 and 4 in the studied solvent.
3.3.1 Theoretical photophysics, comparison of assignments
In order to corroborate the assignments of the patterns of fluorescence spectra, theoretical calculations
were conducted using the Gaussian 09 program, employing the density function theory (DFT),
specifically the B3LYP method and the 6-31g (d) basis set for optimizations. In the photophysics case,
it is calculated using time-dependent methods, TD-DFT, in order to obtain three of the most important
intensities of the molecules [2].Most transitions occur between frontier orbitals and other nearby
orbitals. The HOMO (H), the orbital previous to HOMO (H-1) and the anterior to this (H-2) appear in
this case. As for LUMO (L), the next to LUMO (L+1) and the next to this (L+2) also appear (fig. SI1.6
[a, b, c, d]). The orbitals, both HOMO and LUMO, for both families are seen in fig. SI1. 5(a, b). In
general, the Stokes shifts are explained by the Franck-Condon principle, and at the same time explain
that at two different excitation wavelengths (λ1 andλ2), where the former has less energy than the
second, some or all of the excited states are shown [28]. In table SI1.7, the different values of each
peak are shown (experimental). In addition, the theoretical values are also shown (table SI1.8). As it
was reported [2], the state S2 is not possible to estimate in M8-5 and 6. In M8-3 and 4, it does not exist
with that value. Nevertheless, the first state, S1, it is accurately predicted, for M8-3, 4 and 5, with an
error of 3.1% and for M8-6, with an error of 3.6%.
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4. Conclusions
Four new dyes, aimed at determining whether lengthening the chains of the previously synthesized
molecules, M8-1 and 2, could improve their quantum yields, were synthesized. The yields of the total
synthesis of M8-3, 4, 5 and 6 were 8.6, 8.3, 7.5 and 8.1%, respectively. In general, a trend to maintain
the previous general hypsochromic behaviour was observed. For the value of the difference between
the ground and the excited state, it decreases from M8-1 until M8-6. M8-3 has the highest quantum
yield on average, 58.1%. Searching for an explanation for quantum yields, it was concluded that the
dihedral angle Alkyl-CO should be small and the angle Aryl-CO should be large, to favour better yields.
In general, an odd substituent improves yields, making M8-1 > M8-2, M8-3 > M8-4 and M8-5 > M8-6.
Nevertheless, M8-3 and M8-4 do not follow the dihedral angle trend (inverse relation), and this seems
to have some relation with both do not show the excited state at 450 nm, which appears in all other
members of the series. Finally, all this data points to these compounds as possible candidates for solar
cells. As consequence, future additional measurements will be made.
Acknowledgements
The authors gratefully acknowledge financial support through Fondecyt 1141158 and Ecos-Conicyt C
14 E05 projects.
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Figure index
Figure 1. Structural formula of the synthesized dyes and the previous reported ones. In red, it is
signalled the non-changing backbone.
Figure 2. M8-3 emission spectra in the surveyed solvents, excited at λ1: (a) and (b), and at λ2: (c)
and (d).
Figure 3. Dyes Lippert-Mataga plots: (a) M8-3. (b) M8-4. (c) M8-5. (d) M8-6.
Figure 4. Viscosity vs average quantum yield.
Figure 5. Approximate structures for the determination of dihedral angles of: a) M8-3 and M8-4.
b) M8-5 and M8-6.
Figure 6. Surfaces for the frontier orbitals of M8-3: (a) HOMO, (b) LUMO.
Scheme index
Scheme 1.Sinthetic route to the M8 compounds i) KOH, KI, CH3CH2Br, DMSO; ii) n-BuLi, DMF,
THF, -78ºC; iii) NaBH4, MeOH, THF; iv) PHPh3Br, CHCl3, reflux; v) thiophen-2-carbaldehyde, t-
BuOK, reflux, toluene. vi) secondary amine, PdCl2, (t-bu)3PHBF4, t-BuOK, toluene; vii) n-BuLi,
DMF, THF, -78ºC; viii) cyanoacetic acid, ammonium acetate, acetic acid, 120 ºC.
Table index
Table 1. Nomenclature employed for the synthesized dyes.
Table 2. Dyes maximum absorption wavelength (λmax) in different solvents.
Table 3. M8-3 λem excited at λ1 and λ2. The numbers indicated are related to intensity.
Table 4. Dipole moment from Lippert plots.
Table 5. Dyes quantum yield in different solvents.
Table 6. Average quantum yield in polar and non-polar solvents.
Table 7. Angles grouped according non polar and polar solvents.
14

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Table 1.Nomenclature employed for the synthesized dyes.
Dye IUPAC Name
Code Name
(E)-2-cyano-3-(5-((E)-2-(9,9-diethyl-7-(phenyl(propyl)amino)-9H-fluoren-
2-yl)vinyl)thiophen-2-yl)acrylic acid
M8-3
(E)-2-cyano-3-(5-((E)-2-(9,9-diethyl-7-(phenyl(butyl)amino)-9H-fluoren-
2-yl)vinyl)thiophen-2-yl)acrylic acid
M8-4
(E)-2-cyano-3-(5-((E)-2-(9,9-diethyl-7-(pentyl(phenyl)amino)-9H-fluoren-
2-yl)vinyl)thiophen-2-yl)acrylic acid
(E)-2-cyano-3-(5-((E)-2-(9,9-diethyl-7-(hexyl(phenyl)amino)-9H-fluoren-
2-yl)vinyl)thiophen-2-yl)acrylic acid
M8-5
M8-6

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Table 2. Dyes maximum absorption wavelength (λmax) in different solvents.
Dye
Parameter DCM THF ETA DIO ACT ACN DMF DMSO
M8-3
480
1.4
600
462
1.5
572
444
1.8
552
460
1.4
617
458
1.2
575
428
1.3
531
412
1.6
593
430
2.3
514
λmax
ɛo·104
λem
M8-4
M8-5
486
2.9
595
466
3.7
622
460
3.9
590
474
3.1
621
464
2.9
576
434
2.8
518
424
3.7
605
433
3.6
520
λmax
ɛo·104
λem
470
3.9
584
456
4.4
597
460
3.5
580
464
3.8
618
464
7.0
574
430
3.2
496
418
4.1
504
430
5.1
517
λmax
ɛo·104
λem
M8-6
479
4.0
594
464
4.2
651
462
3.9
654
466
4.5
620
465
3.8
574
427
3.4
554
426
3.9
605
430
3.1
627
λmax
ɛo·104
λem
Polarity Index
3.1
4.0
4.4
4.8
5.1
5.8
6.4
7.2

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Table 3: M8-3 λem obtained from excitations at the wavelengths λ1 and λ2.
Solvent Excitation
Excitation
λem(nm)
λem(nm)
at λ1 (nm)
at λ2(nm)
State
S1
S2
S3
State
S1
S2
S3
DCM
480
638(2)
600(1)
395
635(3)
612(2)
490(1)
THF
462
640(2)
572(1)
382.3
4723(1)
ETA
444
460
458
428
412
430
638(2)
637(2)
639(2)
639(3)
638(3)
638(3)
552(1) 473(3)
617(1)
575(1)
604(2) 531(1)
593(1) 525(2)
607(2) 514(1)
376.7
381.6
386
380
381.4
369.5
471(1)
466(1)
492(1)
531(1)
506(1)
511(1)
DIO
637(3)
611(2)
ACT
ACN
637(3)
639(3)
588(2)
579(2)
DMF
DMSO

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Table 4. Dipole moment from Lippert plots.
Dipole moment
difference (D)
Ground state dipole
moment (D)
Excited state dipole
moment (D)
R2
Dye
Slope
M8-1 [14]
M8-2 [14]
M8-3
24162.04
21356.95
18757.27
18374.84
16095.54
22573.83
3.69
3.47
3.25
3.22
3.01
3.57
11.47
14.24
14.28
14.33
14.32
14.34
7.778
----
10.767
11.030
11.114
11.312
10.768
----
0.791
0.787
0.738
0.829
M8-4
M8-5
M8-6

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Table 5. Dyes quantum yield in different solvents.
Solvent
Polarity
index
DCM
3.1
THF
4.0
ETA
4.4
DIO
4.8
ACT
5.1
ACN
5.8
DMF
6.4
DMSO
7.2
Viscosity
0.40
0.51
0.41
1.15
0.31
0.37
0.77
2.13
Dye
M8-1[14]
M8-2[14]
M8-3
M8-4
M8-5
M8-6
Average
20.5
18.4
62.4
7.2
0.5
4.7
32.7
47.1
35.5
69.4
40.5
45.8
45.2
61.4
34.2
58.4
18.5
80.1
44.3
49.5
98.8
62.5
86.2
58.6
96.9
81.3
80.7
10.9
26.3
48.6
39.7
22.3
25.1
28.8
8.2
25.5
22.9
0.9
2.5
10.5
56.1
60.2
89.4
77.7
65.1
63.8
68.7
17.6
31.7
61.1
47.5
62.2
32.2
42.1
19.0
11.8

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Table 6. Average quantum yield in polar and non-polar solvents.
Non-polar
solvents
average
53.4
Polar
solvents
average
23.2
General
average
Dye
M8-1 [14]
M8-2[14]
M8-3
38.3
38.2
58.1
39.9
46.3
38.5
40.6
60.6
38.4
54.5
35.9
55.5
41.5
38.0
M8-4
M8-5
M8-6
44.0
32.9

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Table 7. Angles grouped according non-polar and polar solvents.
Average non-polar
solvents
Ar-CO
45.5
Average polar solvents
General average
Dye / Angle
M8-1
Al-CO
122.7
170.0
171.7
169.6
169.2
172.3
Ar-CO
44.1
19.7
18.4
21.2
22.1
20.2
Al-CO
124.8
171.5
172.5
170.0
169.0
172.4
Ar-CO
44.8
20.5
18.9
21.4
22.1
20.2
Al-CO
123.7
170.8
172.2
169.8
169.1
172.4
M8-2
21.3
M8-3
19.3
M8-4
21.5
M8-5
22.1
M8-6
20.3

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R = Me [2], Et [2], Pr (M8-3), Bu (M8-3), Pen (M8-3), Hex (M8-3).
R = Me [2], Et [2].
Figure 1.

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3x106
2x106
(a)
DCM
THF
ETA
DIO
1x106
0
400
500
600
700
800
λ (nm)
Figure 2a.

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4x106
3x106
2x106
ACT
(b)
ACN
DMF
DMSO
1x106
0
400
500
600
700
800
λ
(nm)
Figure 2b.

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DCM
THF
ETA
DIO
1.8x106
1.2x106
(c)
6.0x105
0.0
400
500
600
700
λ
(nm)
Figure 2c

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ACT
(d)
2.0x106
1.5x106
1.0x106
ACN
DMF
DMSO
5.0x105
0.0
400
500
600
700
λ
(nm)
Figure 2d

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7000
6000
5000
4000
3000
2000
1000
0
(a)
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35
Dipolar Factor (u.a.)
Figure 3a

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7000
6000
5000
4000
3000
2000
1000
0
(b)
0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35
Dipolar Factor (u.a.)
Figure 3b