Synthesis and conformation of a novel fluorescein-Zn-porphyrin dyad and intramolecular energy transfer

Article abstract of DOI:10.1039/c5nj02901e

This study describes the synthesis and characterization of a new zinc porphyrin-fluorescein dyad, the two chromophoric units being covalently linked by a 1,2,3-triazole bridge. The latter was formed by Cu-catalyzed Huisgen 1,3-dipolar cycloaddition. The c

Full text of DOI:10.1039/c5nj02901e

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Synthesis and Conformation of a Novel Fluorescein-Zn-Porphyrin
Dyad and Intramolecular Energy Transfer
Olivier Rezazgui,a Patrick Trouillas,b,c,* Shi-hong Qiu,a Benjamin Siegler,d Johannes Gierschner,e
Received 00th January 20xx,
Accepted 00th January 20xx
Stephanie Leroy-Lheza*
DOI: 10.1039/x0xx00000x
This study describes the synthesis and characterization of a new zinc porphyrin-fluorescein dyad, the two chromophoric
units being covalently linked by a 1,2,3-triazole bridge. The latter was formed by a Cu-catalyzed Huisgen 1,3-dipolar
cycloaddition. The conformational analysis of this dyad (1) was performed by NOESY experiments, suggesting interactions
between moieties; density functional theory (DFT) calculations confirmed clear evidence of a folded conformer, which is
stabilized by electrostatic and CH-π interactions. Photophysical measurements demonstrated solvent-dependent energy
transfer, with efficiency of about 40%.
www.rsc.org/
linking to another unit such as electron donor and/or acceptor,
chromophore or two-photon absorber antenna.15–18 Due to the
current energy context, the majority of the studies on dyads
Introduction
Over the past twenty years, porphyrins have extensively been
studied as an important class of molecules in biology and materials
science. They are naturally involved in various key biological
processes such as photosynthesis in plants1 or oxygen transport in
the blood.2 They have also a broad range of applications. For
example, synthesized porphyrins can be used in analytical
chemistry,3 in organic solar cells as energy transfer systems,4,5 in
oxidation catalysis,6 in health (photodynamic therapy for cancers and
other diseases treatment, antimicrobial activity)7–9 and more
surprisingly in agriculture as potential photoactivable herbicides,10,11
pesticides12 and insecticides.13,14 These two last applications are
based on the ability of porphyrins, after photoactivation, to produce
reactive oxygen species by interaction with surrounding substrate or
oxygen. As biodiversity, environment preservation and health safety
are the main challenges of agronomy, search for new active
herbicides that are plant-specific, non-toxic to wildlife,
biodegradable by microorganisms and non-polluting groundwater is
thus primordial. In that respect porphyrins seem to be good
candidates to meet these multiple expectations.
containing porphyrins focus on energy transfer and conversion.19
Without being exhaustive, two major areas stand out. First, the
synthesis of dyads in which porphyrins play the role of electron donor
(often coupled to molecules like fullerenes) in order to promote
electron transfer for the development of new organic photovoltaic
devices.7,20–25 Second, multichromophoric systems based on
porphyrins are designed as artificial photosynthetic systems.26–31
Although porphyrins are very often studied as dyads, there are only
a handful of publications on labeling with a fluorescent molecule,
without intention to establish interactions between the two
patterns, for environmental and/or health applications. For example,
porphyrin-rhodamine32 and porphyrin-fluorescein33,34 dyads have
already been synthesized, but without intention of using them under
biological conditions. The interest of such association is particularly
relevant as porphyrin itself exhibits very low fluorescence quantum
yields (ca. 0.1),35 whereas this property is crucial for visualization and
tracking in biological media. Moreover, due to similar chemical
structure, porphyrins have similar optical properties than chlorophyll
and thus, this is an additional serious drawback to localize them in
plants without using an appropriate fluorescent tag. To properly
label porphyrins is thus critical agronomic issue to facilitate their use
as photo-herbicide and/or pesticides.
Designing of molecular systems based on association of a porphyrin
unit to a fluorescent tag appears as a novel, suitable solution to
develop new kind of biodegradable herbicides. However, although
the study in plants is the ultimate goal, it is first necessary to use an
optimized molecular design step to obtain the most appropriate
structures and eliminate all phenomena that can interfere. In that
purpose, we describe here the synthesis and characterization of a
new Zn-porphyrin-fluorescein dyad (1), in which both chromophoric
units are linked by a triazole bridge, as well as of spectroscopic
references 2 and 3 (Scheme 1). NOESY studies suggest interactions
between the porphyrin and fluorescein moieties, which are then
supported by density functional theory (DFT) calculations.
In the recent years, numerous studies have been devoted to the
design of new porphyrin derivatives to optimize their physical (e.g.,
redox, optical…) properties according to one of these applications.
An interesting approach consists of modulating them by covalently
a.LCSN EA1069, Univ. Limoges, 123 Avenue Albert Thomas, 87060 Limoges, France.
b.INSERM UMR 850, Univ. Limoges, School of Pharmacy, 2 rue du Docteur
Marcland, 87025 Limoges Cedex, France.
c. Regional Centre of Advanced Technologies and Materials, Department of Physical
Chemistry, Faculty of Science, Palacký University, tř. 17 listopadu 12, 771 46
Olomouc, Czech Republic.
d.PIAM, Université d’Angers, LUNAM Université, Angers, France.
e. Madrid Institute for Advanced Studies - IMDEA Nanoscience, C/ Faraday 9, Ciudad
Universitaria de Cantoblanco, E-28049 Madrid, Spain.
Electronic Supplementary Information (ESI) available: [Materials, instrumentations
and results of theoretical calculations (molecular orbitals analysis and matrix)]. See
DOI: 10.1039/x0xx00000x
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Steady-state and time-resolved fluorescence spectroscopy reaction catalyzed by copper(I)41 between
investigation provided evidence for energy transfer between the metal exhibits high affinity to the porphyrin nucleus, there is a
6 and 10. As this
fluorescein and the porphyrin moiety in the dyad.
risk of copper complexation by the porphyrin moiety, which
may decrease the efficiency of catalysis and hence reaction
yields. Moreover, as described by Figueiredo et al.in 1999,42 the
production of reactive oxygen species (ROS) was dramatically
decreased in copper-porphyrin whereas zinc-porphyrins are
known to be efficient ROS producers.42 Therefore metalation of
Results and discussion
Synthesis
The synthesis of dyad 1 has required preliminary synthesis of both
porphyrin 6 and fluorescein 10 precursors. Compound 6 was
obtained in three step (Scheme 2), the first one being the formation
of the macrocycle according to Little’s method36 by reaction between
1 equiv. of 4-hydroxybenzaldehyde, 3 equiv. of benzaldehyde and 4
equiv. of pyrrole. Compound 4 was then obtained after purification
step to remove other porphyrinic compounds formed, with 7% yield,
in agreement with the literature.37,38 Synthesis of 4 was also carried
out by microwave irradiations under milder conditions but with
equivalent yields (6-8%).39 Little’s method was preferred to those
5
was done by the reaction of 10 equiv. of Zinc(II) acetate in a
mixture of methanol and chloroform (v/v). Compound was
then obtained in quantitative yield (≥ 99%). For the sake of
6
comparison in spectroscopic studies, a porphyrin of reference
was also synthesized, performing a Williamson’s reaction on
(using excess of 1-bromopropane) / metalation sequence (78%
yield for the two steps).
In parallel, the fluorescein precursor 10, required for synthesis
2
4
of
The first step was a simple esterification of the commercial
in quantitative yield. This
step has allowed blocking the carboxylic function in order to
prevent lactone formation.43 Then compound
was obtained
by alkylation of with an excess of 1,3-dibromopropane (64%
1, was obtained in three steps from fluorescein (Scheme 3).
using dipyrromethanes40 as starting compounds are commercially fluorescein43 affording intermediate
8
available and this synthesis corresponds to a routine one.
9
8
Then, as a second step, propargylation of the hydroxyl group of
yield) and subsequently transformed, into 10 by reaction with
sodium azide based on Singh et al. method (quantitative
yield).44 As for the porphyrin moiety, a fluorescein-based
4
was conducted through a Williamson’s reaction in the
presence of 20 equiv. of propargyl bromide to afford
intermediate with 79% yield. The third step consisted of a zinc
metallation of the porphyrin nucleus. This was of upmost
importance because was obtained by a click-chemistry
5
reference (3) was synthesized by an easy Williamson’s reaction
with an excess of 1-bromopropane (89% yield) performed on
8
.
1
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The porphyrin and fluorescein key-moieties (6 and 10) were For the novel dyad 1, we chose a methoxy-triazole-propyloxy linker
then coupled by an Azide-Alkyne [2+3] Huisgen as this pattern was known to be stable in biological medium and non-
Cycloaddition41,45–47 using Copper(II) acetate/sodium ascorbate toxic, and easy to synthesize.51 Moreover, the linker should be stiff
(2.7/7 equiv.) as catalytic system (acting as precursor of the real enough to restrict the conformational space to a few possible stable
catalytic specie, namely Copper(I), produced in situ) (Scheme 4). geometries. As often observed in such systems bearing two separate
During this coupling step, the solubility of the various reagents chromophores, folding is likely to occur, providing two types of
was problematic. To overcome this issue, salts (Copper (II) conformers.
acetate and sodium ascorbate) were dissolved together in To investigate the presence of folded vs. linear conformations, we
1
distillated water whereas the two precursors (
6
and 10), were conducted temperature dependent H-NMR studies of 1 in CDCl3
dissolved in THF. Afterwards, the two solutions were mixed. between 233K and 333K. Porphyrin hydrogen peaks were seen as
After 24h reaction at room temperature,
91% yield.
1
was obtained with broad signals at high temperature, which sharpened and split as
temperature was lowered, possibly revealing the presence of
In order to reach spectroscopic purity, 1 was purified repeatedly on different conformers undergoing fast exchange at high temperature.
silica gel column (twice) then on preparative plates (three times). NOESY spectra were therefore performed at 253K and 323K in order
Also, before each spectral analysis, a final purification on preparative to see possible spatial proximity between both the porphyrin and the
plates using spectroscopic solvent as eluent was performed. The (UV- fluorescein moieties. The NOESY spectrum obtained at low-
Vis absorption, fluorescence emission and excitation) spectra, temperature showed correlation spots between some protons of
lifetimes and fluorescence quantum yields were reproducible.
xanthen-3-one moiety of fluorescein (at 6.7 ppm) and of porphyrin
(at 7.9 ppm and 8.9 ppm), revealing a folded geometry of the dyad
(Figure 1). Those correlation spots were absent in the high-
temperature spectrum, probably due to fast exchanges between the
conformers (vide infra for thorough discussion).
To support these experimental evidences and to clearly describe
conformers, a DFT-based conformational analysis was conducted.
This was assessed by using both the standard B3LYP (that does not
include dispersion) and the B97XD (that includes both dispersion
Conformational analysis
The conformational features of both porphyrin and fluorescein
moieties have been extensively described, mainly stressing planarity
as being responsible for their photophysical properties.48 Distortion
from planarity has been described for porphyrins depending on the
central metal, substituents and environmental conditions.49,50 In
fluorescein, only the xanthen-3-one moiety is fully planar, whereas
the phenyl ring is almost perpendicular to the former. In the dyad,
both nature and length of the linker are key elements, determining
conformation and thus electronic interactions between both
chromophores, which should have a pronounced effect especially on
energy transfer between the porphyrin and fluorescein moieties
(vide infra).
and
long-range
corrections)
exchange-correlation
(XC)
functionals.52,53 Full geometry optimizations were performed in the
gas phase, as well as in chloroform, DMSO and water by considering
implicit solvent (polarizable continuum model - PCM). A systematic
conformational exploration revealed a few potential conformations
either roughly linear or folded. The most stable conformer is folded
and it was considered throughout this study.
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which the lowest distance between the two moieties is ca. 5.8 Å
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DOI: 10.1039/C5NJ02901E
(Table 1). Solvent nature is expected to influence ratio between
linear and folded form, especially promoting folded form when
polarity increases. Indeed, the calculations assessed with PCM show
that stabilization of the folded structure vs. the linear one is stronger
in water (relative Gibbs energy of 152.7 kJ.mol-1 at the B97XD level,
see ESI) than in chloroform (relative Gibbs energy of 104.7 kJ.mol-1).
Because the explicit description of solvent molecules is missing with
PCM, one can imagine that the absolute values of stabilizing Gibbs
energy between folded and linear forms are overestimated. Indeed
in our methodology of calculation, the entropic contribution is only
partially and indirectly described, and could hardly be accessible at a
reasonable computational cost. This ensures a solid comparative
description i.e., accuracy of the relative Gibbs energies, but it
possibly produces inaccurate absolute energy values. This may
explain why the calculations perfectly agree with the NOESY
experiments at low-temperature, but not high-temperature. When
increasing temperature, the entropic contributions become most
probably crucial, which should rationalize fast exchanges between
conformers suggested from experimental evidences. To stress the
effect of folding on optical properties, a folded and a linear
conformers were considered for the theoretical analysis.
An unfolded geometry, which corresponded to the local minimum
being almost linear (Figure 2), was also considered in this study for
that sake of comparison. This latter geometry avoided, as much as
possible, contacts between both chromophores. All properties of
both geometries were evaluated after full optimization (absence of
any imaginary frequency).
UV-Vis absorption properties
The UV-Vis absorption spectra of
1 and of the two reference
compounds and performed in chloroform at 298K are shown
2
3
in Figure 3, and selected data are collected in Table 2.
The folded-type geometry is stabilized against the linear one even at
the B3LYP level (relative Gibbs energy of 16.4, 75.4, 85.5 and 98.8
kJmol-1 in the gas phase, chloroform, DMSO and water, respectively
in favor of the folded conformers). These results indicate significant
electrostatic contributions in stabilization. At the B97XD level, the
folded forms are additionally stabilized through dispersion
interactions (i.e. relative Gibbs energy of 78.6, 104.7, 136.6 and 152.7
kJmol-1 in the gas phase, chloroform, DMSO and water, respectively).
The folded conformer highlights in particular an attractive
interaction, known as CH-π interaction,54 between the hydrogen of
the benzoate group of fluorescein and the π-system of the phenyl-
substituent of porphyrin, with a distance of ca. 2.4 Å (lowest inter-
fragment distance), as seen in Figure 2. Such interactions are known
to be described by a strong dispersion contribution,55,56 therefore
requiring correct description of such interaction, as obtained with
the dispersion-corrected B97XD functional but not with B3LYP for
The UV-Vis spectrum of the porphyrin 2 is characteristic of
metallated porphyrins, i.e., with an intense Soret band (424 nm) and
the Q-band at lower energy with vibrational structure (two peaks
observed at 552 and 595 nm). This is well described by Gouterman's
'four orbital model',48,57 which bases the analysis on transitions
between HOMO (highest occupied molecular orbital, H) and H-1 to
LUMO (lowest unoccupied molecular orbital, L) and L+1 (Figure 4).
Similar molecular orbital (MO) schemes were obtained with both
functionals (Figures 4 and 5 for B3LYP and B97XD, respectively),
confirming the classical 'four orbital model'. As extensively described
in literature, the Q-band of the metallated porphyrins corresponds
to a degenerated excited state (ES); i.e. singlet transitions to S1, S2.58
As expected, the presence of the propyloxy group slightly breaks the
MO symmetry but not sufficiently to significantly break degeneracy
(Figures 4 and 5).
Table 1: Distances between the two different patterns (porphyrin and fluorescein) into
dyad 1.
B3LYP
ωB97XD
Lowest
Lowest
inter-
Center to
inter-
Center to
fragment
distance (Å)
center (Å)*
fragment
distance (Å)
center (Å)*
Linear
form
Folded
form
9.5
5.8
21.13
10.2
10.8
2.4
21.15
8.4
*Distance between the center of the metal of porphyrin moiety and the center of
the xanthen-3-one moiety.
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(linear vs. folded) and on the inclusion of long range interactions in
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the DFT functional (i.e. B3LYP vs. B97XD); in fact, although the
standard functional B3LYP is widely used to evaluate optical and
electronic properties of derivatives of porphyrins,60–62 it is known to
poorly described CT ES.63 For the most stable, folded geometry of
dyad 1, B3LYP suggests a CT state of very low oscillator strength
(0.01) to be the lowest ES (S0→S1), being somewhat below (14 nm)
the Q-band formed by S2, S3, and essentially described by a H→L
excitation (see Figure 4 and ESI). The reason for the low lying CT state
is readily seen in the MO correlation diagram, see Figure 4. The
energy of L is 0.53 eV below that of 2, so that after formation of 1
(where the frontier MOs of fluorescein become destabilized) L is still
formed by the fluorescein moiety. Conversely H is entirely located on
the porphyrin moiety. The S0 → S4 transition again exhibits
(complex) CT character (Figure 4). In the linear conformation the
low-lying CT state is absent due to the large spatial separation
between the moieties. In order to decide whether CT contributions
are present in the folded dyad, we performed B97XD and CAM-
The fluorescein derivative 3 exhibits the typical absorption features
of fluorescein. The absorption peaks at 439, 463 and 492 nm were B3LYP calculations since those long-range separated XC functionals
assigned to apparent vibronic sub-bands of the first ES59 which is
are known to better behave at describing CT states; only the B97XD
mainly described by the H→L electronic transition, as seen with both
functionals. Both H and L are fully delocalized over the entire
xanthen-3-one moiety. Thus, almost no modification were observed
compare to fluorescein, the chemical modifications being not
involved in the π-conjugated system, hence not affecting π→π*
electronic transitions. The experimental UV-Vis absorption spectrum
of 1 matches the profile obtained by the superimposition of both
spectra of 2 and 3 (Figure 3), indicating the absence of any significant
interaction in the ground state. Anyway, the theoretical analysis is
somewhat complex arising from the question of possible charge-
transfer (CT) contributions within the ES manifold. The time
dependent (TD)-DFT analysis will depend on the dyad conformation
results are shown here (Figure 5), as CAM-B3LYP provides similar
results (see ESI). Different to B3LYP, no intramolecular ICT character
was observed in any ES. The first two, nearly degenerated transitions
to S1, S2 were assigned to the Q-bands of the porphyrin moiety, as
described by the Gouterman's 'four orbital model'. The absence of
the low lying CT state is due to the small energy difference between
L of 3 and L of 2 of only 0.19 eV, which leads to greater mixing of MOs
of both fragments.
Table 2: Selected photophysical data for dyad 1 and reference compounds 2 and 3 in chloroform and DMSO (298K).
Absorption
Emission
Chloroform (4.81) a
DMSO (46.7) a
Chloroform (4.81) a
DMSO (46.7) a
f
f
b
b
abs
abs
abs
abs
em
(nm)
em
(nm)
c,d
c,e
f
f
(nm)
(L.mol-1.cm-1)
(nm)
(L.mol-1.cm-1)
obs
=
obs
=
obs
=
obs =
520 nm
650 nm
520 nm 650 nm
427
463
492
556
598
310 000
19 000
14 000
12 000
4 500
429
460
491
562
601
402 000
17 600
11 700
12 500
6 300
530
564
604
648
2 ns
532
564
608
662
(93%)e
450 ps
(7%)e
e
1
0.04
1.7ns
0.07
-
1,8 ns
424
552
595
439
463
492
325 000
12 000
3 000
14 000
17 700
11 500
602
654
2
3
Poorly soluble
0.05
0.17
1.6ns
Poorly soluble
435
460
490
21 000
25 000
16 300
531
564
532
562
- e
2.8ns
0.18
a Dielectric constant.
b Values represent the mean ± 8% obtained from 3 to 5 independent experiments.
c Using tetraphenylporphyrin (f = 0.11 in toluene), exc = 555nm,48 or fluoresceine (f = 0.92 in NaOH 0.1M), exc = 490 nm as standard.49,50
d Values represent the mean ± 0.01 obtained from 3 independent experiments.
e Contribution percentage in the lifetime of each exponential decay.
f Not determined
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So that after formation of 1 the L (LUMO) is that of porphyrin (Figure The steady-state fluorescence spectra of 1, 2 and 3 were measured
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5), conversely to what was observed with B3LYP. The different in chloroform; see Figure 6 and selected data in Table 2. After
behavior observed with both functionals most probably reflects the excitation at 555 nm where only the porphyrin moiety absorbs,
trend of B3LYP to overestimate π-delocalization, therefore over- compound 1 exhibits the same emission spectrum than the reference
stabilizing MO energy levels (e.g. here fluorescein), which may compound 2 (Figure 6A) as well as the same fluorescence quantum
artificially generate CT states. This is also the main reason that CT yield (Table 2). Excitation of 1 at ex = 490 nm, i.e. in a region where
contributions are negligible in the higher ES, being essentially mainly the fluorescein moiety absorbs, emissions of both fluorescein
described by mixtures of fluorescein- and porphyrin-based electronic and porphyrin are seen (Figure 6A).
transitions. In the linear arrangement, the occurrence of CT states Conversely, preparing equimolar mixture of
becomes even more unlikely due to the spatial separation between emission is negligible against that of fluorescein (see Figure 6B).
the moieties, which is in fact reproduced by the B97XD calculations, The dual emission of contains two contributions, i.e. the
2 and 3, porphyrin
1
see Figure 5 and ESI.
prompt emission of the fluorescein and porphyrin moieties due
To tackle the question of CT contributions in the Q-band of
1
to the absorbance (E) at ex as well as (Förster-type) energy
from the experimental side, a solvatochromic study (THF, DMF transfer (ET) as enabled by the spectral overlap between the
and DMSO) was conducted with as well as with the two donor (D; fluorescein) emission and the acceptor (A; porphyrin)
reference compounds and , for comparison (only results in absorption.
DMSO shown, Table 2); however, the solvent polarity range was To calculate the efficiency of ET (ET), equation (1a) can be used in
limited by the solubility of and even more for
which is poorly the absence of acceptor absorbance:64
soluble even in DMSO. In fact, only slight bathochromic shifts
were observed from chloroform to DMSO for , very similar to
those for and . Moreover, no significant broadening of the
UV-Vis spectrum was observed compared to the excitation
1
2
3
1
2
1
I
1

A

D 

ET  1
2
3
(1a)


D IA


spectrum, which would have been the case if CT state was where D and A are the fluorescence quantum yields of D and A,
underneath (see ESI). Thus, no evidence of the occurrence of an respectively; and ID/IA is the relative fluorescence intensity of D and
ICT band was found. This confirms the lack of CT contributions A in the dyad.
as suggested by the

B97XD functional. In summary, both
In the case of acceptor absorbance, by taking the prompt
experimental and theoretical results revealed negligible CT fluorescence IP,A of the acceptor into account, ET is calculated by
contributions in the ES manifold even in the folded conformer. equation (1b):
This agrees with the rather large center-to-center distances
between the moieties of about 8-10 Å, as well as the non-
parallel arrangements between the π-conjugated
chromophores observed in the folded conformer; in the linear
conformer, the distance is as large as 21 Å (Table 1).

1
A
ID


ET  1



(1b)
D IA  IP,A


where
A AA
D AD
IP,A  ID 

(2)
With A=1-10-E.
Fluorescence properties
A
B
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This leads to:
Experimental
Materials
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
1
A
1
(1c)


ET  1




All organic materials were purchased from commercial suppliers
(Acros Organics, Alfa Aesar, Sigma-Aldrich or TCI) and used as
received. Solvents used in the UV-Vis and fluorescence
measurements were of spectroscopic quality and they were stored
in a dark place. Analytical thin layer chromatography (TLC) was
performed on Merck 60F254 silica gel. Merck precoated plates (silica
gel 60, 2 mm) were used for preparative thin layer chromatography.
Column chromatography was carried out with silica gel (60 ACC, 15-
40 µm, Merck).
D IA / ID 

A / D



AA / AD


Inserting the values in chloroform from Table 2, a ET value of
0.42 ± 0.08 (average from two measurements) is calculated.
The transfer efficiency is also accessible from time-resolved
measurements (3):
ET 1D,A /D
(3)
where D and D,A are the fluorescence lifetimes of the donor
molecule and of dyad 1 upon excitation of the donor moiety (520
nm), respectively. Using the values of Table 2, the ET equals 0.33,
being relatively close to the steady state value. It should be
mentioned that the fluorescence decay of the dyad is somewhat non-
exponential (Table 2), which might reflect the complex excited state
relaxation in the dyad, as observed for other flexible systems.65 On
the other hand, the direct excitation of the acceptor unit (porphyrin
i.e. 650 nm) provided, as expected a very similar value (A,D = 1.9 ns)
as compared to that of the free porphyrin 2 (A = 1.7 ns), see Table 2.
In order to investigate the effect of solvent polarity on energy
transfer efficiency, the same study was conducted in DMSO (Figure 2
in ESI). No shift of the emission maxima was observed (Table 2).
Interestingly, ET, is dramatically increased from chloroform to
DMSO, where it equals 0.75 using equation (1b). We tentatively
assigned the increase of ET in DMSO to the formation of non-
Instrumentation
1H and 13C nuclear magnetic resonance (1H-NMR and 13C-NMR)
spectra were recorded in CDCl3, on Bruker DPX 400 and 500
1
spectrometers. H and NOESY spectra at variable temperature were
recorded in CDCl3, on a Bruker DRX 500 spectrometer with a BVT3000
variable temperature unit. Chemical shifts are reported as δ (parts
per million), downfield from internal TMS. IR spectra were
performed with a Perkin Elmer Spectrum 1000 photometer, with
samples conditioned on KBr pellets. Melting points (Mp) were
uncorrected.
Mass spectra were performed with a 4800 MALDI TOF/TOF™
Analyzer from AB SCIEX for all porphyrins derivatives and dyad 1. For
fluorescein derivatives, high resolution electrospray ionization mass
covalent dimers or n-mers due to decreased solubility in the polar spectra (HR ESI-MS) were performed on a Bruker maXis mass
solvent. This might indeed bring the donor and acceptor moieties in
closer contact by intermolecular interaction (mainly π-π stacking
between fluorescein and porphyrin) and thus enhance ET.
spectrometer by the ICOA/CBM (FR2708) platform.
Ultraviolet-visible spectra (UV-Vis) and fluorescence spectra were
recorded using 10 mm quartz cells. UV-Vis were recorded on a
SPECORD® 210 double beam spectrophotometer using 10 mm quartz
cells.
Conclusions
In this article, a novel fluorescein-Zn-porphyrin dyad built with a
triazole linkage was studied both experimentally and theoretically.
According to NOESY analysis, a folding conformer is likely to exist,
which has been confirmed by conformational analysis of the dyad.
Non-covalent interactions including electrostatic and CH-π
interaction strongly stabilized folded with respect to unfolded
geometries. Fluorescence spectroscopy has revealed an
intramolecular energy transfer between the two patterns
(fluorescein and porphyrin), which has appeared more efficient in
DMSO than in chloroform as expected. Further investigations such as
Steady-state photoluminescence spectra were recorded using a
FLS980 spectrometer (Edinburgh Instruments, UK equipped with a
450 W xenon lamp. Detection was made in the 300–800 nm range
using a cooled R928P Hamamatsu photomultiplier (dark count 50
cps). Quantum yields were measured using tetraphenylporphyrin
(H2TPP)66 in toluene and commercial fluorescein (spectroscopic
quality)67,68 in aqueous NaOH 0.1M as standards.
Time-resolved spectroscopy measurements were performed on the
fast time-resolved spectroscopy should provide further insight into same apparatus, using time correlated single photon counting
the interaction between the porphyrin and fluorescein moieties.
Likewise, synthesis and study of fluorescein tagged porphyrins with
linkers more or less flexible are currently in progress in our
laboratory. This study has paved the way towards an optimal use of
tagged-porphyrins in plant cells to understand mechanisms of the
herbicide action. In this context, water solubilization has been
envisaged through vectorization.
(TCSPC) and a picosecond diode laser at 509.2 nm as excitation
source (temporal width of 150 ps). The instrument response function
was measured using a diffusive reference sample (LUDOX ® from
Sigma-Aldrich).
Synthesis
5-(4-hydroxyphenyl)-10,15,20-triphenylporphyrin (4). 4-hydroxy-
benzaldehyde (1 equiv., 1.22 g, 10 mmol) and benzaldehyde (3
equiv., 3.1 mL, 30 mmol) were dissolved in 200 mL of propionic acid.
The solution was heated at 120°C under reflux with vigorous stirring
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for 1h, then freshly distilled pyrrole (4 equiv., 2.8 mL, 40 mmol) were mmol) and K2CO3 (10 equiv., 124.4 mg, 0.9 mmol) were dissolved in
View Article Online
DOI: 10.1039/C5NJ02901E
added. After 1 h, the mixture was cooled and the solvent was dry DMF (10 mL). The reaction was activated twice by micro-waves
evaporated to dryness and the crude product was purified by column irradiations (5’/ 200 W/ 120°C). After solvent evaporation, the crude
(silica gel, petroleum ether with CHCl3 gradient ranging from 70 to product was dissolved in DCM, washed with distillated water (2x25
100%). Compound 4 was obtained as a purple solid (435 mg, 7%).
mL) then dried over MgSO4. The residue was purified on column
1H NMR (CDCl3, 400 MHz) δppm: 8.87 (d, 2H, J=4.8Hz); 8.83 (sel, 6H); (silica gel, CHCl3) to give compound 7 as a purple solid (47.3 mg, 78%).
8.21 (d, 6H, J=7.6 Hz); 8.04 (d, 2H, J=8.3 Hz); 7.75 (d, 9H, 7.4 Hz); 7.16 1H NMR (CDCl3, 400 MHz) δppm: 8.87 (d, 2H, J=4.8Hz); 8.83 (sel, 6H);
(d, 2H, J=8.2 Hz); -2.74 (s, 2H).
8.21 (d, 6H, J=7.6 Hz); 8.04 (d, 2H, J=8.3 Hz); 7.75 (d, 9H, 7.4 Hz); 7.16
13C NMR (CDCl3, 400 MHz) δppm: 155.4; 142.2; 135.7; 134.8; 134.6; (d, 2H, J=8.2 Hz); 4.32 (t, 2H, J=6.8 Hz); 1.84 (m, 2H); 1.04 (t, 3H, J=7.3
133.9; 132.3: 131.9; 131.2; 131.0; 130.9; 129.0; 128.6; 128.5; 128.3; Hz); -2.74 (s, 2H).
128.0; 127.8; 126.7; 120.1; 120.0; 119.7; 113.7.
MS (MALDI-TOF): m/z = 631.52 [M+H] +.
13C NMR (CDCl3, 400 MHz) δppm: 157.5; 139.3; 137.3; 135.6; 135.5;
134.5;133.9; 133.8; 132.3; 132.1; 131.0; 129.3; 128.7; 127.4; 120.1;
UV-Vis (CHCl3) λmax nm (ε, 10-3 L.mol-1.cm-1): 419 (563), 518 (11), 556 119.4; 113.7; 69.1; 23.8; 12.5.
(9), 598 (3), 647 (1).
MS (MALDI-TOF): m/z = 673.32 [M+H] +.
UV-Vis (CHCl3) λmax nm (ε, 10-3 L.mol-1.cm-1): 418 (342), 518 (16), 552
5-(4-propargyloxyphenyl)-10,15,20-triphenylporphyrin (5). 5-(4- (12), 595 (3), 648 (1).
hydroxyphenyl)-10,15,20-triphénylporphyrine 4 (1 equiv., 140 mg,
0.22 mmol), propargyl bromide (20 equiv., 0.93 mL, 4.4 mmol), K2CO3 Zinc(II) 5-(4-propoxyphenyl)-10,15,20-triphenylporphyrin (2). Com-
(20 equiv., 605 mg, 4.4 mmol) were dissolved in dry DMF (30 mL). pound 7 (1 equiv., 26.1 mg, 0.04 mmol) and zinc (II) acetate (10
The solution was stirred in the dark for 24h under argon and at room equiv., 85.6 mg, 0.4 mmol) were dissolved in a solution of
temperature. After solvent removing, the crude product was CHCl3/MeOH (1/1, v/v). The mixture was stirred during one night at
dissolved in DCM, washed with distillated water (2x25 mL) and dried room temperature. After solvent evaporation, the product was
over MgSO4. The residue was purified by column (silica gel, CHCl3) to dissolved in DCM and washed with distillated water (2x15 mL), then
give compound 5 as a purple solid (116 mg, 79%).
dried over MgSO4 to give compound 2 as a purple solid (26.7 mg,
1H NMR (CDCl3, 400 MHz) δppm: 8.87 (d, 2H, J=4.8Hz); 8.83 (sel, 6H); >99%).
8.21 (d, 6H, J=7.6 Hz); 8.04 (d, 2H, J=8.3 Hz); 7.75 (d, 9H, 7.4 Hz); 7.16 1H NMR (CDCl3, 400 MHz) δppm: 8.87 (d, 2H, J=4.8Hz); 8.83 (sel, 6H);
(d, 2H, J=8.2 Hz); 4.98 (d, 2H, J=2.3 Hz); 2.69 (t, 1H, J=2.3 Hz); -2.74 8.21 (d, 6H, J=7.6 Hz); 8.04 (d, 2H, J=8.3 Hz); 7.75 (d, 9H, 7.4 Hz); 7.16
(s, 2H).
(d, 2H, J=8.2 Hz); 4.32 (t, 2H, J=6.8 Hz); 1.84 (m, 2H); 1.04 (t, 3H, J=7.3
13C NMR (CDCl3, 400 MHz) δppm: 157.4; 139.3; 137.3; 135.6; 135.5; Hz).
134.5; 133.8; 132.1; 131.0; 129.3; 128.7; 127.4; 120.1; 119.4; 113.1; 13C NMR (CDCl3, 400 MHz) δppm: 157.5; 139.3; 137.3; 135.6; 135.5;
78.7; 76.8; 56.2.
134.5;133.9; 133.8; 132.3; 132.1; 131.0; 129.3; 128.7; 127.4; 120.1;
119.4; 113.7; 69.1; 23.8; 12.5.
MS (MALDI-TOF): m/z = 669.23 [M+H] +.
UV-Vis (CHCl3) λmax nm (ε, 10-3 L.mol-1.cm-1): 419 (337), 518 (13), 556 MS (MALDI-TOF): m/z = 735.24 [M+H] +.
(6), 598 (3), 647 (1).
IR υ (cm-1), KBr: 2118 (CC) ; 3282 (C-H).
UV-Vis (CHCl3) λmax nm (ε, 10-3 L.mol-1.cm-1): 424 (290), 552 (12), 595
(3).
Zinc(II) 5-(4-propargyloxyphenyl)-10,15,20-triphénylporphyrin (6). Methyl 2-(6-hydroxy-3-oxo-3H-xanthen-9-yl)benzoate (8). Fluo-
5-(4-propargyloxyphényl)-10,15,20-triphénylporphyrine 5 (1 equiv., rescein (1 equiv., 2.76g, 8.3 mmol) was dissolved in freshly distillated
115.8 mg, 0.17 mmol) and zinc (II) acetate (10 equiv., 311 mg, 1.7 MeOH (200 mL). Fuming sufuric acid (1 mL) was added dropwise,
mmol) were dissolved in a solution of CHCl3/MeOH (1/1, v/v). The then the mixture was stirring in the dark for 18h. The reaction was
mixture was stirred during one night at room temperature. After stopped by addition of cooled water, then the solution was filtered
solvent evaporation, the product was dissolved in DCM and washed to give compound 8 as an orange solid (2.8 g, 98 %).
with distillated water (2x25 mL), then dried over MgSO4 to give Tf : 228°C.
3
4
compound 6 (123.5 mg, >99%).
1H NMR (CDCl3, 400 MHz) δppm: 8.88 (d, 2H, J=4.7Hz); 8.84 (sel, 6H); 7.74 (dt, 1H, 3J=7.5 Hz, 4J=1.4 Hz); 7.66 (dt, 1H, 3J=7.6 Hz, 4J=1.4 Hz);
1H NMR (CDCl3, 400 MHz) δppm: 8.25 (dd, 1H, J=7.8 Hz, J=1.2 Hz);
3
4
8.21 (d, 6H, J=7.4 Hz); 8.14 (d, 2H, J=8.4 Hz); 7.75 (d, 9H, 7.4 Hz); 7.36 7.30 (dd, 1H, J=7.5 Hz, J=1 Hz); 6.96 (d, 1H, J=2.4 Hz); 6.89 (d, 1H,
3
4
(d, 2H, J=8.5 Hz); 4.99 (d, 2H, J=2.4 Hz); 2.69 (t, 1H, J=2.3 Hz).
J=8.8 Hz); 6.85 (d, 1H, J=9.7 Hz); 6.74 (dd, 1H, J=8.9 Hz, J=2.4 Hz);
13C NMR (CDCl3, 400 MHz) δppm: 157.4; 139.3; 137.3; 135.6; 135.5; 6.55 (dd, 1H, 3J=9.7 Hz, 4J=1.7 Hz); 6.47 (d, 1H, J=1.6 Hz); 3.64 (s, 3H).
134.5; 133.8; 132.1; 131.0; 129.3; 128.7; 127.4; 120.1; 119.4; 113.1; 13C NMR (CDCl3, 400 MHz) δppm: 185.7; 165.6; 159.0; 154.4 (2C);
78.7; 76.8; 56.2.
149.2; 134.7 (2C); 132.7; 130.4 (2C); 130.2; 129.6 (2C); 128.8; 117.5;
105.7 (2C); 100.8 (2C); 52.4 (O-CH3).
MS (MALDI-TOF): m/z = 731.15 [M+H] +.
UV-Vis (CHCl3) λmax nm (ε, 10-3 L.mol-1.cm-1): 426 (301), 556 (12), 598 HRMS (ESI-Q3): m/z = 347.09 [M+H] +.
(3.7).
UV-Vis (CHCl3) λmax nm (ε, 10-3 L.mol-1.cm-1) : 438 (12), 462 (15), 491
(10).
IR υ (cm-1), KBr: 2118 (CC); 3282 (C-H).
5-(4-propoxyphenyl)-10,15,20-triphenylporphyrin (7). Compound 4 Methyl 2-(6-(3-bromopropoxy)-3-oxo-3H-xanthen-9-yl)benzoate
(1 equiv., 59 mg, 0.09 mmol), 1-bromopropane (5 equiv., 41 µL, 0.45 (9). Methyl 2-(6-hydroxy-3-oxo-3H-xanthen-9-yl)benzoate (1
8
10 | J. Name., 2012, 00, 1-3
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equiv., 330 mg, 0.95 mmol), 1,3-dibromopropane (3 equiv., 290 µL, 6.54 (dd, 1H, 3J=9.7 Hz, 4J=1.8 Hz); 6.45 (d, 1H, J=1.8 Hz); 4.02 (t, 2H,
View Article Online
DOI: 10.1039/C5NJ02901E
2.85 mmol) and K2CO3 (10 equiv., 1.3 g, 9.5 mmol) were dissolved in J=6.5 Hz); 3.63 (s, 3H); 1.86 (m, 2H); 1.06 (t, 3H, J=7.4 Hz).
dry DMF (25 mL). The solution was stirring at room temperature, in 13C NMR (CDCl3, 400 MHz) δppm: 185.8; 165.6; 163.7; 159.0; 154.3;
the dark and under argon for 20h. After solvent evaporation, the 150.1; 134.7; 132.6; 131.1; 130.6; 130.4; 130.2; 129.9; 129.6; 128.8;
residue was dissolved in CHCl3 and washed with distillated water 117.5; 114.7; 113.8; 105.8; 100.8; 70.4; 52.4; 22.3; 10.4.
(3x25 mL). Then the crude product was purified by column (silica gel, HRMS (ESI-Q3): m/z = 389.13 [M+H] +.
CHCl3) to give compound 5 as an orange oil (285.7 mg, 64%).
UV-Vis (CHCl3) λmax nm (ε, 10-3 L.mol-1.cm-1) : 439 (14), 463 (17), 492
3
4
1H NMR (CDCl3, 400 MHz) δppm: 8.25 (dd, 1H, J=7.8 Hz, J=1.2 Hz); (11).
7.74 (dt, 1H, 3J=7.5 Hz, 4J=1.4 Hz); 7.66 (dt, 1H, 3J=7.6 Hz, 4J=1.4 Hz);
3
4
7.30 (dd, 1H, J=7.5 Hz, J=1 Hz); 6.96 (d, 1H, J=2.4 Hz); 6.89 (d, 1H, Dyad (1). Compound 6 (1 equiv., 276.7 mg, 0.38 mmol) and
3
4
J=8.8 Hz); 6.85 (d, 1H, J=9.7 Hz); 6.74 (dd, 1H, J=8.9 Hz, J=2.4 Hz); compound 10 (1.5 equiv., 250.8 mg, 0.57 mmol) were dissolved in
6.55 (dd, 1H, 3J=9.7 Hz, 4J=1.7 Hz); 6.47 (d, 1H, J=1.6 Hz); 4.24 (t, 2H, THF (45 mL). Copper (II) acetate (2.7 equiv., 187 mg, 1.03 mmol) and
J=5.8 Hz); 3.64 (s, 3H); 3.60 (t, 2H, J=6.3 Hz); 2.37 (quint, 2H, J=6.06 sodium ascorbate (7 equiv., 527 mg, 2.66 mmol) preliminary
Hz).
dissolved in distillated water (4 mL) were added. The mixture was
13C NMR (CDCl3, 400 MHz) δppm: 185.8; 165.6; 163.7; 159.0; 154.3; stirring for 24h, in the dark and at room temperature. After solvent
150.1; 134.7; 132.6; 131.1; 130.6; 130.4; 130.2; 129.9; 129.6; 128.8; evaporation, the crude product was dissolved in DCM and washed
117.5; 114.7; 113.8; 105.8; 100.8; 70.4; 52.4; 33.9; 27.3.
HRMS (ESI-Q3): m/z = 467.09 [M+H] +.
with distillated water (2x25 mL), then dried over MgSO4. Finally
residue was purified on column (silica gel, DCM with EtOH gradient
UV-Vis (CHCl3) λmax nm (ε, 10-3 L.mol-1.cm-1) : 438 (12), 461 (16), 491 ranging from 0 to 10%) to give compound 1 as a red-orange solid
(10).
(403.5 mg, 91%).
1H NMR (CDCl3, 500 MHz)
Methyl
(10).
2-(6-(3-azidopropoxy)-3-oxo-3H-xanthen-9-yl)benzoate Porphyrin moiety: δppm: 8.86 (d, 8H, J=4.7Hz); 8.18 (d, 6H, J=7.7 Hz);
Methyl
2-(6-(3-bromopropoxy)-3-oxo-3H-xanthen-9-yl) 7.98 (d, 2H, J=8.3 Hz); 7.69 (m, 9H); 7.56 (d, 2H, J=8.5 Hz); 5.66 (d, 2H,
benzoate 9 (1 equiv., 286 mg, 0.61 mmol) and sodium azide (4 equiv., J=2.4 Hz).
158.6 mg, 2.44 mmol) were dissolved in dry DMF (15 mL). The Fluorescein moiety : δppm: 8.24 (dd, 1H, 3J=7.5 Hz, 4J=1.2 Hz); 7.72 (dt,
solution was stirring in the dark for 24h, at room temperature and 1H, 3J=7.5 Hz, 4J=1.3 Hz); 7.61 (dt, 1H, 3J=7.6 Hz, 4J=1.4 Hz); 7.28 (dd,
under argon. After solvent evaporation, the crude product was 1H, 3J=7.5 Hz, 4J=1 Hz); 6.95 (d, 1H, J=2.4 Hz); 6.85 (d, 1H, J=8.9 Hz);
dissolved in DCM and washed twice with distillated water (2x25 mL), 6.79 (d, 1H, J=8.9 Hz); 6.71 (dd, 1H, 3J=8.9 Hz, 4J=2.4 Hz); 6.61 (dd, 1H,
then dried over MgSO4 to give compound 10 as an orange oil (261.8 3J=8.8 Hz, 4J=2.1 Hz); 6.49 (d, 1H, J=1.6 Hz); 3.91 (t, 2H, J=5.9 Hz); 3.60
mg, >99%).
(s, 3H); 3.50 (sel., 2H); 2.01 (m, 2H).
3
4
1H NMR (CDCl3, 400 MHz) δppm: 8.24 (dd, 1H, J=7.6 Hz, J=1.2 Hz); Triazole moiety: δppm: 8.14 (s,1H).
7.74 (dt, 1H, 3J=7.5 Hz, 4J=1.3 Hz); 7.67 (dt, 1H, 3J=7.6 Hz, 4J=1.4 Hz); 13C NMR (CDCl3, 500 MHz)
7.30 (dd, 1H, J=7.5 Hz, J=1 Hz); 6.96 (d, 1H, J=2.4 Hz); 6.90 (d, 1H, Porphyrin moiety : δppm: 157.4; 136.4; 135.9; 135.8; 134.8; 134.4;
J=8.9 Hz); 6.85 (d, 1H, J=9.7 Hz); 6.74 (dd, 1H, J=8.9 Hz, J=2.4 Hz); 133.8; 132.6; 131.0; 129.6; 128.9; 127.3; 120.1; 113.5; 76.6.
6.55 (dd, 1H, 3J=9.7 Hz, 4J=1.5 Hz); 6.47 (d, 1H, J=1.6 Hz); 4.17 (t, 2H, Fluorescein moiety: δppm: 184.6; 165.6; 162.6; 158.3; 154.0; 150.1;
J=5.7 Hz); 3.63 (s, 3H); 3.53 (t, 2H, J=6.5 Hz); 2.10 (quint, 2H, J=6.4 134.8; 132.7; 131.1; 130.6; 130.4; 130.2; 129.8; 129.6; 128.9; 117.3;
3
4
3
4
Hz).
115.0; 112.8; 105.0; 100.9; 65.4; 52.4; 47.9; 22.6.
13C NMR (CDCl3, 400 MHz) δppm: 185.8; 165.6; 163.7; 159.0; 154.3; Triazole moiety: δppm: 143.3; 129.1.
150.1; 134.7; 132.6; 131.1; 130.6; 130.4; 130.2; 129.9; 129.6; 128.8; MS (MALDI-TOF): m/z = 1160.34 [M+H] +.
117.5; 114.7; 113.8; 105.8; 100.8; 68.8; 52.4; 42.7; 30.4.
UV-Vis (CHCl3) λmax nm (ε, 10-3 L.mol-1.cm-1): 439 (11), 463 (15), 492 (13), 556 (12), 598 (4.5).
UV-Vis (CHCl3) λmax nm (ε, 10-3 L.mol-1.cm-1): 427 (310), 463 (20), 492
(9).
IR υ (cm-1), KBr: 2102 (C-N).
IR υ (cm-1), KBr: 2099 (N3).
Theoretical calculations
Methyl 2-(3-oxo-6-propoxy-3H-xanthen-9-yl)benzoate (3). Com-
pound 8 (1 equiv., 173.2 mg, 0.5 mmol), 1-bromopropane (3 equiv.,
136.4 µL, 1.5 mmol) and K2CO3 (20 equiv., 1.38 g, 10 mmol) were
dissolved in dry DMF (20 mL). The solution was stirring for 18h in the
dark, at room temperature and under argon. After solvent
evaporation, the residue was dissolved in DCM and washed twice
with distillated water (2x25 mL), then dried over MgSO4. To finish,
the product was purified on column (silica gel, DCM) to give
compound 3 as an orange solid (172.8 mg, 89%).
Quantum chemistry calculations based on DFT were performed to
investigate the conformational space of compounds 1, 2 and 3.
Because of the structure of 1, non-covalent interactions between the
porphyrin and fluorescein moieties were expected. In particular, a
proper description of dispersive forces appeared mandatory. The use
of the ωB97XD XC functional has been described to properly describe
non-covalent interactions.52,53 The robustness of ωB97XD at
describing non-covalent interactions was confirmed to better
describe non-covalent interactions (π-π stacking and H-bonding). The
conformational analysis was assessed by a systematic exploration of
the potential energy surface of the triazole linkage. The most stable
conformers were confirmed by the absence of any imaginary
3
4
1H NMR (CDCl3, 400 MHz) δppm: 8.24 (dd, 1H, J=7.2 Hz, J=1.2 Hz);
7.73 (dt, 1H, 3J=7.4 Hz, 4J=0.9 Hz); 7.66 (dt, 1H, 3J=7.6 Hz, 4J=0.9 Hz);
3
4
7.31 (dd, 1H, J=7.2 Hz, J=1 Hz); 6.94 (d, 1H, J=2.3 Hz); 6.87 (d, 1H,
3
4
J=8.9 Hz); 6.84 (d, 1H, J=9.7 Hz); 6.73 (dd, 1H, J=8.9 Hz, J=2.3 Hz);
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frequency. The Pople-type double-ζ basis set 6-31+G(d,p) was used
as being an adapted compromise between accuracy and time
consumption. Adding diffuse function (+) is mandatory to better
evaluate electron distribution on these highly π-conjugated systems.
When necessary, the extensively recommend LANL2DZ basis set,
using core pseudo potentials, was used for the transition metal Zn.69
Solvent effects were taken into account implicitly using the IEFPCM
(Integral Equation Formalism Polarizable Continuum Model). In PCM
models, the substrate is embedded into a shape-adapted cavity
surrounded by a dielectric continuum characterized by its dielectric
constant (ε = 78.35 and 4.71 in water and CHCl3, respectively).
Optical properties (i.e., UV-Vis absorption and ES description) were
predicted by using TD(Time Dependent)-DFT calculations. Three
different functionals were used, namely B3LYP as classically used for
porphyrins and dyads and the long-range separated functionals,
namely ωB97XD and CAM-B3LYP, due to their capacity to properly
describe CT in ES. Only the ωB97XD results are provided here as
CAM-B3LYP similar results. All calculations were performed with
Gaussian09.70
Notes and references
View Article Online
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Photophysical properties
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Acknowledgements
P. Trouillas and S. Leroy-Lhez thank the French National Research
Agency (ANR Porphy-Plant) for financial support. The authors thank
the “Conseil Régional du Limousin” for financial support and CALI
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was supported by the Spanish Ministerio de Economía
y
Competitividad (MINECO; project MultiCrom, grant no. CTQ2014-
58801). The authors also thank Dr Yves Champavier for all NMR
analysis, Mr Cyril Colas from ICOA for all mass spectra and to finish
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P. Trouillas thanks the Czech Science Foundation (P208/12/G016),
the Ministry of Education, Youth and Sports of the Czech Republic
(project LO1305) and the Operational Program Education for
Competitiveness-European
CZ.1.07/2.3.00/20.0058 of the Ministry of Education, Youth and
Sports of the Czech Republic) is also gratefully acknowledged.
Social
Fund
(project
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New Journal of Chemistry
Page 14 of 14
View Article Online
DOI: 10.1039/C5NJ02901E
Modulations of optical properties of a new porphyrin-fluorescein dyad were elucidated by
experimental and theoretical techniques, conformational rearrangements being studied.