Synthesis, structures, optical properties, and TD-DFT studies of donor-π-conjugated dipicolinic acid/ester/amide ligands

Article abstract of DOI:10.1016/j.tet.2007.10.064

A series of 2,6- and 4-functionalized dipicolinic acid, ester, or amide featuring π-conjugated substituents such as donor-(phenyl or fluorenyl)-acetylene groups have been synthesized. Four crystallographic structures are reported. The influence of the sub

Full text of DOI:10.1016/j.tet.2007.10.064

Available online at www.sciencedirect.com
Tetrahedron 64 (2008) 399e411
www.elsevier.com/locate/tet
Synthesis, structures, optical properties, and TD-DFT studies
of donor-p-conjugated dipicolinic acid/ester/amide ligands
Alexandre Picot a, Christophe Feuvrie b, Cyril Barsu a, Floriane Malvolti a, Boris Le Guennic a,
b
Hubert Le Bozec , Chantal Andraud , Loıc Toupet , Olivier Maury
a
c
a,
*
€
a Universite´ de Lyon, Laboratoire de Chimie, CNRSdENS-Lyon, 46 Alle´e d’Italie, 69364 Lyon, France
b Sciences Chimiques de Rennes, UMR 6226 CNRSdUniversite´ de Rennes 1 Campus de Beaulieu, 35042 Rennes, France
c Groupe de la Matie`re Condense´e et Mate´riaux, UMR 6626 CNRSdUniversite´ de Rennes 1, Campus de Beaulieu, 35042 Rennes, France
Received 18 September 2007; received in revised form 15 October 2007; accepted 19 October 2007
Available online 22 October 2007
Abstract
A series of 2,6- and 4-functionalized dipicolinic acid, ester, or amide featuring p-conjugated substituents such as donor-(phenyl or fluorenyl)-
acetylene groups have been synthesized. Four crystallographic structures are reported. The influence of the substituent position, the nature of the
donor group, and the conjugated backbone as well as the role of the pyridinic side arms on the absorption and emission properties are studied and
discussed on the basis of TD-DFT calculations.
Ó 2007 Elsevier Ltd. All rights reserved.
1. Introduction
design of chromophore-based ligands upon adequate function-
alization by p-conjugated groups. To date, only phenyl,17 phe-
nylacetylene,11,18 and oligo-thiophene19 derivatives were
reported and their photophysical properties studied. Recently,
we thought to use DPAM as acceptor moiety for the design of
new pushepull chromophores. Preliminary results underlined
their interesting luminescence and nonlinear optical properties
(second harmonic generation and two-photon absorption in-
duced luminescence), and made them attracting candidates
for biological imaging applications20 as well as for the sensi-
tization of EuIII luminescence by two-photon antenna effect.21
In this article, we report the detailed synthetic procedures
for the preparation of DPA/DPE/DPAM-based dipolar chro-
mophores. The charge transfer can be induced either by direct
functionalization of the 4-position of the pyridinic ring or by
2,6-substitution of the amido moieties of DPAM (Chart 1).
A particular attention has been devoted to the optimization
and multi-gram scale-up of the synthesis of key intermediates
such as the iodo DPAM or DPE derivatives. Four crystallo-
graphic structures are described and the absorption/emission
properties are studied and discussed on the basis of TD-DFT
calculations.
Dipicolinic acid is a widely used building block in coordina-
tion and supramolecular chemistry. The corresponding bis-acid
(DPA), bis-ester (DPE), and bis-amide (DPAM) derivatives be-
have as tridentate ligands, which efficiently coordinate to tran-
sition metals (ZnII, CuII, PtII, MnII, RuII, CoII/III, FeIII,.) or
lanthanides.1e3 Recently, the use of such ligands was extended
to the formation of complexes featuring interesting lumines-
cence,4 nonlinear optical5 or magnetic properties,6 in solution
as well as in crystalline state7 or solegel matrix.8 In addition,
unsymmetrical acid/amide ligands were recently designed for
heavy metal extraction purpose.9 DPA has also been largely
used as starting building block for the construction of supramo-
lecular architectures like dendrimers,10 cryptans,11 calixar-
enes,12 helicoidal polynuclear complexes,13 even chiral14 or
self-assembled organic simple or double helix.15
Whereas DPA has already been substituted by functional or
solubilizing group,16 it has scarcely been involved for the
* Corresponding author. Tel.: þ33 (0) 4 72 72 83 99.
E-mail address: olivier.maury@ens-lyon.fr (O. Maury).
0040-4020/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.
doi:10.1016/j.tet.2007.10.064

400
A. Picot et al. / Tetrahedron 64 (2008) 399e411
4-position
Introduction of charge transfer
R = OH
R
R
2,6-position
N
dipicolinic acid - DPA
R = OEt
O
O
diethyl-2,6-pyridinedicarboxylate - DPE
R = NEt2
2,6-pyridinedicarboxamide - DPAM
I
H
N
H
N
R
O
R
N
N
O
O
O
R'2N
NR'2
L1. R = Et
L1'. R = Bu
D
D
N
L4. D = OHex
L5. R = NHex2
L2 R = NEt2 D = OHex
.
L2'. R = OMe D = OHex
L2". R = OH D = OHex
L3. R = NEt2 D = NHex2
R
R
N
N
N
O
O
O
O
Chart 1. DPA/DPE/DPAM-based chromophores.
2. Results and discussion
good yield (72%) in the presence of phosphorous acid and
a 57% aqueous solution of hydrogen iodide. In order to avoid
the hydrolysis of the amido moieties by hydrogen iodide, new
reaction conditions were found to optimize the yield of this re-
action (see Section 4).25 Note that 4 and 6, which are the two
2.1. Syntheses
Commercially available chelidamic acid is the starting build-
ing block for the synthesis of this series of tridentate ligands. As
the presence of the pyridinic electron-withdrawing group para
to the OH group significantly enhances the rate of nucleophilic
substitutions, various halogens can be introduced at this posi-
tion. Since the p-system functionalization in 4-position involves
Pd-catalyzed Sonogashira cross-coupling reaction, we envis-
aged to prepare the bromo (2) or the more reactive iodo (4,6) de-
rivatives (Scheme 1). Bromination reactions on chelidamic acid
are generally carried out under harsh conditions, using PBr3,
PBr5, or POBr3.22 We thus decided to revisit and adapt an orig-
inal and milder bromination method for the synthesis of DPA
and DPE derivatives.23 This technique consists in the reaction
of an excess of tetrabutylammonium bromide with 1 in hot tol-
uene for 4 h in the presence of P4O10. After workup, pure 2 was
R2
R1
R1
N
O
O
1
R1 = OMe
OMe
R2 = OH
1)
2)
2
3
4
5
6
7
8
Br
Cl
I
OMe
OMe
NEt2
Cl
I
3)
4)
5)
NEt2
isolated as a white-beige powder in 85% yield. Unfortunately,
NEt2
C
CSiMe3
0
further reactivity of 2 for the synthesis of L2 by Sonogashira
coupling was below our expectations, reaching only 45% of
the desired ligand. The synthesis of the iodo derivative 4 from
3 was adapted and optimized from the literature to avoid decom-
position of the final product 4 (sonication duration was reduced
to 30 min).24 DPAM derivative 6 was obtained from 5 in fairly
NEt2
C CH
Scheme 1. Synthesis of DPA, DPE, and DPAM intermediates: (1) NBu4Br,
P4O10
toluene, sonication, 110 ꢀC, 30 min, 81%; (2) CH3COCl, NaI,
,
CH3CN, sonication, rt, 30 min, 95%; (3) HI, H3PO3, H2O, 80 ꢀC, 210 min,
72%; (4) PdCl2(PPh3)2, CuI, Et3N/THF, rt, 20 h, 92%; (5) K2CO3, CH2Cl2,
MeOH, rt, 90 min, 94%.

A. Picot et al. / Tetrahedron 64 (2008) 399e411
401
remains the direct amidation of the acidic side arms. In the first
step, the acyl chloride derivative of dipicolinic acid was obtained
in situ by the action of thionyl chloride in the presence of cata-
lytic amount of DMF. After removal of the solvents, 2-fold ex-
R2
R1
Hex Hex
cess of either the commercially available amine 19 or 2029 was
9
R1 =
R2 =
Br
Br
Br
Br
Br
H
1)
2)
3)
4)
5)
6)
0
added yielding 89% and 61% of L1 and L1 , respectively
(Scheme 3). The second approach for the synthesis of the ligands
consisted in the functionalization at the 4-position of the pyri-
dinebyaSonogashiracross-couplingreactionusingstandardex-
perimentalconditions(PdCl2(PPh3)2: 10 mol %; CuI:20 mol %;
THF/NEt3; temperature: 40 ꢀC). Six new ligands were synthe-
10
11
12
13
14
15
16
17
18
COCH3
OCOCH3
OH
OHex
OHex
OHex
NO2
CCSiMe3
0
00
sized using this technique (L2, L2 , L2 eL5) and isolated after
column chromatography with moderate to good yields (50e
90%, Scheme 4). Detailed experimental procedures and spectro-
scopic and analytic characterizations are described in Section 4.
CCH
I
I
I
7)
8)
NH2
NHex2
Scheme 2. Synthesis of fluorene p-donor intermediate building blocks: (1)
CH3COCl, AlCl3, CH2Cl2, rt, 20 h, 93%; (2) m-CPBA, CHCl3, rt, 4 days,
82%; (3) KOH, H2O, MeOH, 80 ꢀC, 20 h, 97%; (4) n-HexeBr, K2CO3,
CH3CN, 82 ꢀC, 20 h, 85%; (5) PdCl2(PPh3)2, CuI, Et3N/DMF, 115 ꢀC, 3 days,
84%; (6) K2CO3, CH2Cl2, MeOH, rt, 90 min, 95%; (7) Fe powder, AcOH,
118 ꢀC, 30 min, 69%; (8) n-HexeBr, NaI, Na2CO3, DMF, 95 ꢀC, 20 h, 71%.
2.2. Crystallographic structures
Crystals suitable for X-ray diffraction analysis were obtained
0
in the cases of L1, L2, L2 , and L3 by slow evaporation of di-
chloromethane solutions. Crystal data and refinement parame-
ters are collected in Table 1; ORTEP drawing and selected
bond lengths and angles are described in Figure 1 and Table 2,
respectively. In the case of L1, the crystallographic packing is
ensured by a network of intermolecular hydrogen bonds be-
tween the NHof theamide fragment and thecarbonylofavicinal
molecule with short contact interactions of about 2.156 and
key synthons, could be prepared in a several gram scale (for ex-
ample, 10 g for 4) by using our modified procedures. At this
stage, the classical Sonogashira reaction between 6 and
trimethylsilylacetylene (TMS-acetylene) followed by TMS de-
protection with K2CO3 led to the formation of compounds 7 and
8 in 92% and 94% yields, respectively (Scheme 1).
˚
2.174 A. In addition, the molecular structure indicates the exclu-
The hexyloxyfluorenylacetylene intermediate 15 was ob-
tained in six steps with a good overall yield (50%) by follow-
ing the procedure proposed by Serrano et al. (Scheme 2).26
Commercially available 2-bromofluorene was first C-alkylated
to compound 9, which gave 10 after a FriedeleCrafts acyla-
tion. This compound was easily rearranged to 11 by
a BaeyereVilliger oxidation using m-CPBA and a further de-
protection of the newly formed ester function with KOH led to
12. O-Alkylation of the alcohol function with bromohexane
produced 13, which then led to 14 after a Sonogashira reaction
with TMS-acetylene and finally to 15 after deprotection of the
TMS group. In contrast, the synthesis of the nitrogen donating
fluorene intermediate 18 was more straightforward: in the first
step, commercially available 2-iodo-7-nitrofluorene was
C-alkylated by bromohexane under basic conditions to lead
to 16, then the reduction reaction of the nitro group to the
amino derivative 17 using Fe powder and a final N-alkylation
with bromohexane produced 18.27,28
sive formation of the synesyn conformer due to the presence of
two intramolecular hydrogen bonds between the amide frag-
ment and the nitrogen atom belonging to the central pyridinic
˚
ring with d(NH/Npy) of about 2.36 and 2.28 A, respectively.
The formation of these five member rings is responsible for
the good planarity between the carboxamide side arms and the
central pyridinic ring with twist angles t of 6.22 and 7.76ꢀ. Sim-
ilar structures have already been described in the literature in the
case of phenyl30 or benzyl31 substituted amides.
On the other hand, the absence of any hydrogen bond
0
source in the case of L2, L2 , and L3 results in a completely
different crystal packing. The three dipolar ligands crystallize
in a head-to-tail way in order to minimize the electrostatic re-
pulsion and the crystal cohesion is mainly ensured by p-stack-
ing interactions. The difference observed between the three
structures mainly consists in distortion due the sterical0 crowd-
ing of the alkyl substituents. In consequence, ligand L2 featur-
ing the less bulky methyl ester substituent exhibits the most
planar structure with small twist angles between ester and
pyridinic groups (t¼2.80 and 4.24ꢀ), as well as between
The most straightforward approach in order to induce strong
charge transfer onto the pyridinic moieties of the ligands
Cl
O
H
N
H
N
CH2Cl2
RT, 1h
N
R'2N
NH2
+
2
N
O
O
R'2N
NR'2
O
Yield : 89 %
61 %
L1
L1'
Cl
19. R' = Et
20. R' = Bu
Scheme 3. Synthesis of 2,6- functionalized DPAM derivatives.

402
A. Picot et al. / Tetrahedron 64 (2008) 399e411
Et2N
Et2N
O
O
O
PdCl2(PPh3)2, CuI
Et3N / THF
I
N
D
N
D
+
40 °C, 3 days
O
Et2N
Et2N
L2
D = OHex
Yield : 89 %
53 %
L3
NHex2
Et2N
Et2N
Hex Hex
Hex Hex
O
O
O
PdCl2(PPh3)2, CuI
Et3N / THF
+
D
N
D
I
N
40 °C, 3 days
O
Et2N
MeO
Et2N
MeO
Yield : 65 %
59 %
L4
L5
D = OHex
NHex2
O
O
PdCl2(PPh3)2, CuI
Et3N / THF
HexO
+
HexO
N
I
N
40 °C, 5 hrs
O
O
MeO
L2' 93 %
MeO
HO
O
1) NaOH 1M
RT, 15hrs
2) HCl
HexO
N
HCl
O
HO
L2'' 99%
Scheme 4. Synthesis of the 4-functionalized ligands.
Table 1
Selected crystallographic data and collection parameters for L1, L2, L2 , and L3
0
0
Compound
L1
L2
L2
L3
Formula
M/g
C35H52N4O2
560.81
C29H39N3O3
477.63
C23H25NO5
395.44
C27H33N5O2
459.58
Crystal size/mm
Color
Crystal system
0.28ꢁ0.24ꢁ0.16
0.45ꢁ0.45ꢁ0.40
White
0.45ꢁ0.33ꢁ0.33
White
0.32ꢁ0.22ꢁ0.22
Green
Yellow
Orthorhombic
Monoclinic
P21/c
Triclinic
Pꢂ1
Monoclinic
P21/a
Space group
˚
Pbcn
15.5771 (6)
a/A
˚
8.8634 (4)
27.728 (1)
11.3235 (5)
90
5.4095 (1)
7.6784 (1)
25.9772 (5)
93.643 (1)
94.868 (1)
105.335 (1)
1032.67 (3)
2
9.7048 (2)
14.5440 (3)
17.7686 (3)
90
b/A
˚
18.5939 (9)
11.5586 (5)
c/A
a/ꢀ
b/ꢀ
G/ꢀ
90
90
100.174 (3)
90
97.7690 (10)
90
90
3347.8 (3)
3
˚
V/A
2739.0 (2)
4
2484.96 (8)
4
Z
4
0.71073
˚
l (Mo Ka)/A
m/cmꢂ1
F(000)
0.71073
0.75
1032
0.71073
0.90
0.71073
0.80
984
0.69
1224
420
120
T/K
120
1.113
120
1.158
130
1.228
Dc/g cmꢂ3
q range/ꢀ
hkl ranges
1.272
3.10e26
0<h<19, 0<k<22, 0<l<14
3.21e27.0
ꢂ10<h<11, ꢂ35<k<35,
ꢂ13<l<14
317
2.80e27.46
0<h<7, ꢂ9<k<9,
ꢂ33<l<32
262
2.54e29.18
0<h<13, 0<k<19,
ꢂ24<l<23
314
Variables
190
3285
Reflections measured
Reflections [I>2s(I )]
R1[I>2s(I )]/R1 (all data)
wR2[I>2s(I )]/wR2 (all data)
Sw
5931
5092
4574
3765
6639
4956
2484
0.0502/0.0709
0.1320/0.1564
0.997
0.0472/0.0563
0.1143/0.1207
1.045
0.0590/0.0710
0.1690/0.1838
1.016
0.0567/0.0806
0.1496/0.1722
1.060
Largest diff
peak/hole/e A
0.287/ꢂ0.213
0.347/ꢂ0.181
0.470/ꢂ0.329
0.435/ꢂ0.263
ꢂ3
˚

A. Picot et al. / Tetrahedron 64 (2008) 399e411
403
0
Figure 1. ORTEP drawings of ligands L1 (a), L2 (b), L2 (d), and L3 (c).
alkoxyphenyl and pyridinic moieties (r¼5.88ꢀ, Table 2).
Replacing the ester by diethylamide fragment (L2) induces
a significant steric hindrance at the acceptor side of the mole-
cule. This modification results in a small distortion of the
p-conjugated backbone (r¼15.81ꢀ), and a strong deformation
of the pyridine-dicarboxamide unit with twist angles t of
30.64 and 65.29ꢀ. Finally, changing the hexyloxy by a dihexyl-
amino donor group (L3) strongly enhances the steric hindrance
at both donor and acceptor sides of the molecule. These ster-
ical crowding dramatically distorts the p-conjugated backbone
as well as the pyridine-dicarboxamide moieties with twist
angles t and r of 55.7 and 48.5ꢀ, respectively. It is worth not-
ing that all these deformations are clearly due to the crystal
packing, the molecule being completely planar in solution as
suggested by theoretical simulations (vide infra).
2.3. Optical properties and TD-DFT calculations
Table 2
Selected distances (A) and angles ( )
ꢀ
Room temperature absorption and emission spectra of
L1eL5 in diluted dichloromethane solution are displayed in
Figures 2, 4, and 6 and the experimental and theoretical data
are reported in Table 3. All chromophores exhibit broad
˚
0
L1
L2
L2
L3
Conformation
ta
synesyn
6.22
7.76
synesyn
30.64
65.29
d
syneanti
2.80
4.24
synesyn
48.52d
Fb
34.43
47.56
d
d
d
45000
40000
35000
30000
25000
20000
15000
10000
5000
rc
15.81
5.88
55.70
1.513(2)d
CpyeC(O)
1.5069(17)
1.5064(18)
1.2375(15)
1.2267(16)
1.3507(18)
1.3394(16)
d
1.5123(19)
1.5147(18)
1.2285(18)
1.2437(16)
1.3486(19)
1.3511(17)
1.202(2)
1.510(2)
1.5149(19)
1.1987(17)
1.2051(18)
d
C]O
1.234(2)d
1.345(2)d
C(O)eN
C^C
1.192(2)
1.4385(19)
1.4379(18)
1.186(4)
1.443(3)
1.437(3)
Cpye(CC)
(CC)eCph
a
d
d
1.4352(18)
1.4363(19)
Twist angle between the central pyridinic ring and the lateral amide or
0
ester arm.
250
300
350
400
450
500
550
600
b
c
d
Twist angle between the diethylaminophenyl and the carboxamide.
Twist angle between the pyridinic and the 4-functionalized phenyl ring.
The two lateral arms of the molecule are symmetric due to the presence of
λ
/ nm
Figure 2. Absorption spectra of L1 (gray), L2 (d), L3 (/), L4 (---), and L5
(-ꢃ-) in dichloromethane.
a C2 symmetric axis in the crystallographic structure.

404
A. Picot et al. / Tetrahedron 64 (2008) 399e411
Table 3
Photophysical data in dichloromethane solution and from TD-DFT
calculations
fa
Composition
calcd
max
labs
/
3/
lem
/
l
/
nm L Molꢂ1 cmꢂ1 nm nm
L1 341 14,100
n
n
0
L1 341 14,100
420
405
0.16 HOMO/LUMOþ1(0.66)
0.26 HOMO-1/LUMOþ1(0.66)
HOMO/LUMO (0.15)
L2 327 29,100
394 333
428 339
461 344
443 370
489 378
554 422
0.99 HOMO/LUMO (0.65)
0.83 HOMO/LUMO (0.66)
0.76 HOMO/LUMO (0.66)
1.00 HOMO/LUMO (0.66)
1.24 HOMO/LUMO (0.66)
1.03 HOMO/LUMO (0.67)
0
L2 336 20,400
00
L2 346 25,700
L3 384 42,000
L4 354 43,800
L5 411 38,400
n: no emission.
a
Calculated oscillator strength.
Figure 3. MO energy diagram of L1a
.
delocalization. On the contrary, in solution (or in the solid
state), the free rotation around the (O)CNHe(PhNMe2) bond
breaks this planarity and reduces the conjugation between
the donor and the acceptor moieties.
intense structureless absorption transitions in the visible part
of the spectra, with lmax between 327 and 411 nm depending
on the nature of the donor and transmitter groups. Two differ-
ent behaviors can be distinguished depending on the 2,6- or
On the other hand, all the 4-functionalized derivatives L2e
L5 are good fluorophores with broad absorption and emission
bands centered in the visible part of the spectra. In all cases,
TD-DFT calculations performed on models featuring simpli-
fied alkyl substituents indicate that the lowest energy transition
can be unambiguously assigned to a CT transition as illus-
trated by a representative example in the case of L4a (Table
3 and Fig. 5). The calculated maximal absorption wavelengths,
lcmaalcxd, match perfectly the experimental ones (Table 3). As ex-
pected, increasing the donor strength or the p-conjugated
length by replacing the alkoxy (L2,L4) by an amino group
(L3,L5) or a phenyl (L2,L3) by a fluorenyl (L4,L5) moiety, re-
spectively, results in a bathochromic shift of both absorption
and emission bands. In consequence, these simple chemical
modifications allow to tune the emission properties on a large
range from the blue (350 nm) to the red (650 nm) as shown in
Figure 4.
4-functionalization of the central pyridinic moieties. For the
0
2,6-functionalized ligands L1,L1 a very broad transition cen-
tered at 341 nm with a shoulder at around 330 nm can be ob-
served. DFT calculations (Fig. 3) performed on a model L1a
featuring dimethylamino donor group show two almost degen-
erated HOMOs (orbitals 106 and 107 in Fig. 3) and two quasi-
degenerated LUMOs (orbitals 108 and 109). Therefore, two
slightly different transitions are predicted theoretically at 420
and 405 nm, respectively (Table 3), and present a marked
charge transfer (CT) character from the amino donor group
to the central acceptor moieties delocalized on the pyridinic
ring and on the carbonyl fragment. It is worth noting that
the experimental transitions are significantly blue shifted com-
pared to the calculated ones (Dlz80 nm). The overestimation
of the calculated results is clearly due to the completely planar
conformation of the dimethylaminophenylamide side arm
obtained by geometry optimization ensuring an optimal
Finally, it is possible to fine tune the photophysical proper-
ties by subtle modifications of the pyridinic side arms. Replac-
ing bis-diethylamide moieties of ligand L2 by di-(methyl
1.0
0.8
0.6
0.4
0.2
0.0
350
400
450
500
550
600
650
700
λ / nm
Figure 4. Luminescence spectra of L2 (d), L3 (/), L4 (---), and L5 (-ꢃ-) in
dichloromethane with lex¼310, 340, 320, and 360 nm, respectively.
Figure 5. MO energy diagram of L4a
.

A. Picot et al. / Tetrahedron 64 (2008) 399e411
405
1.0
0.8
0.6
0.4
0.2
0.0
acceptor fragment. Absorption and emission properties are
tuned in all the visible range by modification of (i) the position
of the substituents (2,6- or 4-), (ii) the nature of the donor end
group (amino or alkoxy), (iii) the nature of the p-conjugated
backbone (phenyl, phenylacetylene, fluorenylacetylene), and
(iv) the nature of the pyridinic side arms (acid, ester, amide).
Preliminary experiments have underlined the interesting non-
linear optical properties (two-photon absorption and second
harmonic generation) of some of these compounds and further
studies are currently in progress to adapt these chromophores
for biological imaging purpose.20 Finally, all these chromo-
phores are also ligands that are able to coordinate a large va-
riety of transition metals or lanthanides. The systematic study
of the nonlinear optical properties of the related complexes is
under investigation.
350
400
450
λ / nm
500
550
600
0
00
Figure 6. Luminescence spectra of L2 (d), L2 (---), and L2 (/) in dichloro-
methane with lex¼310 nm.
4. Experimental section
0
00
ester) L2 or di-acid L2 results in a 10 nm red shift in absorp-
tion for each modification (Table 3). This bathochromic shift is
much more significant in emission (Fig. 6): a large red shift
4.1. General procedure
NMR spectra (1H, 13C) were recorded at room temperature
on a BRUKER AC 200 operating at 200.13 and 50.32 MHz for
1H and 13C, respectively. Data are listed in parts per million
(ppm) and are reported relative to tetramethylsilane (1H,
13C); residual solvent peaks of the deuterated solvents were
used as internal standard. UVevis absorption measurements
were recorded on a JASCO V550 spectrometer. The lumines-
cence spectra were measured using a HoribaeJobin Yvon
Fluorolog-3Ò spectrofluorimeter, equipped with a red-sensitive
Hamamatsu R928 photomuliplier tube. Spectra were reference
corrected for both the excitation source light intensity varia-
tion (lamp and grating) and the emission spectral response
(detector and grating). Infra-red spectra were recorded on a
Mattson 3000 spectrometer using KBR pellets. High-resolu-
tion mass spectrometric measurements and elemental analysis
were performed at the Service Central d’Analyse du CNRS
(Vernaison, France).
(Dlem¼65 nm) is observed from L2 to the di-acidic derivative
00
L2 . This effect can be rationalized on the basis of the theoret-
ical calculations. Whereas, the three compounds present sim-
ilar HOMOs, essentially located on the donor alkoxyphenyl
part of the molecule, their LUMOs depicted in Figure 7 exhibit
slight differences. In the case of L2a, the LUMO is delocalized
on the pyridinic ring and on the triple bond without any signif-
icant participat0ion of the amide fragment. On the contrary, the
00
LUMOs of L2 a and L2 a show a strong participation of the
carbonyl moieties, enforcing the acceptor character of the pyr-
idinic ring. These last considerations could allow to conclude
by the following order for the strength of the acceptor groups
DPA>DPE>DPAM.
Crystal structure analyses were performed on an Oxford
Diffraction Xcalibur Saphir 3 diffractometer with graphite
monochromatized Mo Ka radiation. Cell parameters were ob-
tained with Denzo and Scalepack with 10 frames (psi rotation:
1ꢀ/frame). The structure was solved with SIR-97,32 which re-
veals the nonhydrogen atoms of structure. After anisotropic
refinement, many hydrogen atoms may be found with a Fourier
Difference. The whole structure was refined with SHELXL9733
by the full-matrix least-square techniques (use of F magnitude;
x, y, z, aij for C, N, and O atoms, x, y, z in riding mode for H
atoms). ORTEP views were made with PLATON 98.34 All cal-
culations were performed on a Silicon Graphics Indy computer.
Crystallographic data for the structural analysis have been
deposited with the Cambridge Crystallographic Data Centre,
CCDC 233716, CCDC 282663, CCDC 278081, and CCDC
238186.
00
Figure 7. Comparison of HOMO and LUMO of L2a and L2 a
.
3. Conclusion
In summary, a series of 2,6- and 4-functionalized chromo-
phore-based dipicolinic acid, ester, or amide molecules were
prepared and four of them were characterized by X-ray dif-
fraction. The photophysical studies and TD-DFT calculations
clearly indicate that all compounds exhibit intense charge
transfer from the donor end group to the central pyridinic
Computational details. DFT geometric optimizations and
TD-DFT excitation energy calculations on simplified ligands
featuring a methyl substituent were carried out with the Gauss-
ian 03 (Revision B.04) package35 employing the three-

406
A. Picot et al. / Tetrahedron 64 (2008) 399e411
parameter hybrid functional of Becke based on the correlation
functional of Lee, Yang, and Parr (B3LYP).36 The 6e31G*
basis sets were used for all atoms.
aqueous Na2CO3 (150 mL) are added. The organic phase is
washed with saturated aqueous Na2S2O3 (150 mL), water
(150 mL), brine (150 mL), and dried over Na2SO4. After evap-
oration of the solvents and recrystallization from methanol, the
product is obtained as a white powder (13 g, 93%). Mp
175 ꢀC. dH (200 MHz, CDCl3, Me4Si) 8.67 (2H, s, Ph), 4.03
(6H, s, 2ꢁCOOCH3).
4.2. Synthesis
4-Hydroxy-2,6-pyridinedicarboxylic acid dimethyl ester 1,37
4-chloro-2,6-pyridinedicarboxylic acid dimethyl ester 3,38
2-bromo-9,9-dihexylfluorene 9,39 4-ethynyl-N,N-dihexylani-
line,40 2-iodo-7-nitro-fluorene 16,41 and N,N-dibutyl-1,4-
benzenediamine 2029 were prepared by following the published
procedure. Chelidamic acid, N,N-diethyl-1,4-benzenediamine,
and 4-(hexyloxy)phenylacetylenewere commercially available,
and purchased from Aldrich, Acros, and Maybridge, respec-
tively. All the solvents used for the synthesis were of analytical
grade. For the spectroscopy, spectroscopic grade solvents were
used.
4.2.4. 4-Chloro-2,6-bis(diethylcarbamoyl)pyridine (5)
DMF (0.5 mL, 6.5 mmol) is added to a solution of chelidamic
acid monohydrate (5.63 g, 28.0 mmol) in thionyl chloride
(20 mL, 280 mmol). After stirring the mixture overnight at
76 ꢀC, the excess of thionyl chloride is evaporated by trap-to-
trap vacuum distillation technique. The remaining white residue
is dissolved in dichloromethane (15 mL) and dry diethylamine
(29 mL) is slowly added at 0 ꢀC. The solution is heated to
55 ꢀC for 2 h. Water (20 mL) is then added and the mixture is
acidified to pH¼1. After separation, the aqueous phase is ex-
tracted twice with dichloromethane (2ꢁ20 mL). The organic
phases are combined, washed with water, saturated aqueous
NaHCO3, and dried over Na2SO4. After filtration and evapora-
tion of the solvent, a white solid is obtained (8.07 g, 93%).
(Found: C, 57.7; H, 7.2; N, 13.4. C15H22ClN3O2 requires: C,
57.8; H, 7.1; N, 13.5%.) Mp 116 ꢀC. dH (200 MHz, CDCl3,
Me4Si) 7.61 (2H, s, Ph), 3.52 (4H, q, J 7.1, 2ꢁNCH2CH3),
3.30 (4H, q, J 7.1, 2ꢁNCH2CH3), 1.22 (6H, t, J 7.1, 2ꢁ
NCH2CH3), 1.13 (6H, t, J 7.1, 2ꢁNCH2CH3). dC (50.3 MHz,
CDCl3, Me4Si) 166.8, 154.8, 146.1, 124.1, 43.2, 40.3, 14.2, 12.7.
4.2.1. General procedure A for Sonogashira cross-coupling
To a degassed solution of the halogenated substrate in THF
(DMF) and Et3N under argon are added the acetylene derivative,
copper iodide, and Pd(PPh3)2Cl2. The dark brown mixture is
heated in the dark while stirring. After cooling to room temper-
ature, the black precipitate is filtered and triturated with CH2Cl2
(2ꢁ20 mL). The remaining organic phase is washed with satu-
rated aqueous ammonium chloride solution (3ꢁ50 mL) and
brine (50 mL). The organic layer is dried (Na2SO4) and evapo-
rated under vacuum. The crude residue is purified by flash chro-
matography on silica.
4.2.5. 4-Iodo-2,6-bis(diethylcarbamoyl)pyridine (6)
4.2.2. 4-Bromo-2,6-pyridinedicarboxylic acid dimethyl
ester (2)
To a mixture of 4-chloro-2,6-bis(diethylcarbamoyl)pyridine
(3.0 g, 9.6 mmol, 2 equiv) and phosphorous acid (395 mg,
4.8 mmol, 1 equiv) is added drop by drop a 57% aqueous so-
lution of hydrogen iodide (11.7 mL, 85.6 mmol, 18 equiv) at
0 ꢀC. The reaction mixture is heated to 80 ꢀC for 3.5 h. After
cooling to room temperature, the mixture is neutralized by the
slow addition of a saturated aqueous solution of NaHCO3. The
aqueous phase is extracted with diethyl ether (3ꢁ50 mL), and
the organic phases are combined and dried over Na2SO4. The
solvent is evaporated and the pure product is obtained as a light
yellow solid (2.8 g, 72%). (Found: C, 44.9; H, 5.6; N, 10.3.
C15H22IN3O2 requires: C, 44.7; H, 5.5; N, 10.4%.) Mp
108 ꢀC. dH (200 MHz, CDCl3, Me4Si) 7.98 (2H, s, Ph), 3.52
Tetrabutylammonium bromide of 38.2 g (118.9 mmol,
5.0 equiv), 42.4 g of P4O10 (147.2 mmol, 6.0 equiv), and
150 mL of dry toluene are introduced in a 500 mL flask. The
mixture is heated to 80 ꢀC for an hour. 4-Hydroxy-2,6-pyridine-
dicarboxylic acid dimethyl ester of 5 g (23.7 mmol, 1 equiv) is
dissolved in 150 mL of dry toluene and slowly added to the re-
action. The resulting mixture is heated to 110 ꢀC for 4 h. After
cooling to room temperature, the supernatant is taken aside
while remaining oily residue is triturated with 200 mL of hot tol-
uene for an hour. The organic phases are combined, poured into
250 mL of water, and the mixture is stirred for additional 2 h.
The organic phase is then dried over Na2SO4 and evaporated.
The product is obtained as a white-beige powder (5.5 g, 85%).
Mp 176 ꢀC. dH (200 MHz, CDCl3, Me4Si) 8.47 (2H, s, Ph),
4.04 (6H, s, 2ꢁCOOCH3).
(4H, q,
J
7.1, 2ꢁNCH2CH3), 3.30 (4H, q,
J 7.1,
2ꢁNCH2CH3), 1.23 (6H, t, J 7.1, 2ꢁNCH2CH3), 1.13 (6H,
t, J 7.1, 2ꢁNCH2CH3). dC (50.3 MHz, CDCl3, Me4Si)
166.5, 153.7, 132.9, 106.8, 43.3, 40.2, 14.2, 12.7.
4.2.3. 4-Iodo-2,6-pyridinedicarboxylic acid dimethyl
ester (4)
4.2.6. 4-(Trimethylsilylethynyl)-2,6-bis(diethylcarbamoyl)-
pyridine (7)
Sodium iodide of 65.2 g (435 mmol, 10 equiv) is added to
a solution of 4-chloro-2,6-pyridinedicarboxylic acid dimethyl
ester (10 g, 43.5 mmol, 1 equiv) in acetonitrile (300 mL).
The mixture is sonicated for 20 min at room temperature. Ace-
tyl chloride of 10.25 g (130.5 mmol, 3 equiv) is slowly added
to the solution and the mixture is sonicated for an additional
30 min at room temperature. CH2Cl2 (300 mL) and saturated
Prepared according to general procedure A with 4-iodo-
2,6-bis(diethylcarbamoyl)pyridine: 2.0 g, 4.96 mmol, 1 equiv;
THF: 80 mL; Et3N: 80 mL; trimethylsilylacetylene: 1.05 mL,
7.44 mmol, 1.5 equiv; copper iodide: 151 mg, 0.79 mmol,
0.16 equiv; Pd(PPh3)2Cl2: 278 mg, 0.40 mmol, 0.08 equiv; tem-
perature: 25 ꢀC; time: 96 h; chromatography: ethyl acetate;
product: light brown solid (1.71 g, 92%). (Found: C, 64.5; H,

A. Picot et al. / Tetrahedron 64 (2008) 399e411
407
8.5; N, 11.3. C20H31N3O2Si requires: C, 64.3; H, 8.4; N, 11.3%.)
dH (200 MHz, CDCl3, Me4Si) 7.58 (2H, s, Ph), 3.51 (4H, q, J 7.1,
2ꢁNCH2CH3), 3.28 (4H, q, J 7.1, 2ꢁNCH2CH3), 1.21 (6H, t, J
7.1, 2ꢁNCH2CH3), 1.10 (6H, t, J 7.1, 2ꢁNCH2CH3), 0.22 (9H,
s, Si(CH3)3). dC (50.3 MHz, CDCl3, Me4Si) 167.5, 153.7, 133.5,
125.7, 101.9, 101.1, 43.2, 40.1, 14.2, 12.7, ꢂ0.45.
over Na2SO4. After evaporation of the solvents and purification
by flash chromatography (pentane/CH2Cl2, 1:2) the product is
obtained as a light orange solid (6.35 g, 82%). (Found: C,
66.76; H, 7.30. C27H35BrO2$1/4CH2Cl2 requires: C, 66.43; H,
7.26%.) Mp 42 ꢀC. dH (200 MHz, CDCl3, Me4Si) 7.63 (1H, d,
J 8.9, Ph), 7.56e7.34 (3H, m, Ph), 7.10e7.02 (2H, m, Ph),
2.31 (3H, s, COCH3), 1.96e1.82 (4H, m, 2ꢁCCH2), 1.20e
0.96 (12H, m, 2ꢁCH2CH2CH2CH3), 0.76 (6H, t, J 6.6, 2ꢁCH2-
CH3), 0.70e0.56 (4H, m, 2ꢁCCH2CH2). dC (50.3 MHz, CDCl3,
Me4Si) 169.4, 153.1, 151.9, 150.5, 139.4, 137.7, 130.1, 126.2,
121.03, 120.99, 120.4, 120.3 116.4, 55.6, 40.3, 31.5, 29.7,
23.7, 22.6, 21.2, 14.0.
4.2.7. 4-Ethynyl-2,6-bis(diethylcarbamoyl)pyridine (8)
K2CO3 of 370 mg (2.68 mmol, 2 equiv) is added to a solution
of 4-(trimethylsilylethynyl)-2,6-bis(diethylcarbamoyl)pyridine
(500 mg, 1.34 mmol, 1 equiv) in CH2Cl2/methanol (30 mL,
1:2). The mixture is stirred at room temperature for 1.5 h and
30 mL of water is added. The aqueous phase is extracted with
CH2Cl2 (2ꢁ40 mL), and the organic phases are combined,
washed with water (50 mL), brine (50 mL), and dried over
Na2SO4. CH2Cl2 is evaporated under vacuum and the crude light
brown solid is purified by flash chromatography with ethyl ace-
tate to give our product as a light yellow solid (380 mg, 94%).
(Found: C, 67.51; H, 7.76; N, 13.77. C17H23N3O2 requires: C,
67.75; H, 7.69; N, 13.94%.) Mp 116 ꢀC. dH (200 MHz, CDCl3,
Me4Si) 7.63 (2H, s, Ph), 3.52 (4H, q, J 7.1, 2ꢁNCH2CH3),
3.35 (1H, s, CCH ), 3.29 (4H, q, J 7.1, 2ꢁNCH2CH3), 1.22
(6H, t, J 7.1, 2ꢁNCH2CH3), 1.12 (6H, t, J 7.1, 2ꢁNCH2CH3).
dC (50.3 MHz, CDCl3, Me4Si) 167.3, 153.8, 132.6, 126.0,
83.4, 80.1, 43.2, 40.2, 14.2, 12.7.
4.2.10. 7-Bromo-9,9-di-n-hexylfluoren-2-ol (12)
KOH of 4.2 g (75 mmol, 10 equiv) is added to a solution of
3.54 gof7-bromo-9,9-di-n-hexylfluoren-2-ylacetate(7.5 mmol,
1 equiv) in water/ethanol (40 mL, 1:1). The mixture is stirred at
80 ꢀC for 20 h. After cooling to room temperature, the reaction
mixture is neutralized by the addition of a solution of concd
HCl and extracted twice with diethyl ether (2ꢁ50 mL). The or-
ganic phases are combined, washed with water (50 mL), brine
(50 mL), and dried over Na2SO4. After evaporation of the sol-
vents, theyellow oil obtainedis purified byflash chromatography
(pentane/CH2Cl2, 1:4) to give the product as a white solid
(3.22 g, 97%). (Found: C, 68.71; H, 7.63. C25H33BrO$1/2H2O
requires: C, 68.49; H, 7.82%.) Mp 106 ꢀC. dH (200 MHz,
CDCl3, Me4Si) 7.56e7.42 (2H, m, Ph), 7.42e7.34 (2H, m,
Ph), 6.84e6.72 (2H, m, Ph), 1.92e1.80 (4H, m, 2ꢁCCH2),
1.22e0.94 (12H, m, 2ꢁCH2CH2CH2CH3), 0.75 (6H, t, J 6.9,
2ꢁCH2CH3), 0.74e0.54 (4H, m, 2ꢁCCH2CH2). dC (50.3 MHz,
CDCl3, Me4Si) 155.6, 152.8, 152.4, 140.0, 133.3, 129.9, 126.0,
120.8, 120.2, 119.8, 114.2, 110.1, 55.3, 40.5, 31.5, 29.7, 23.7,
22.6, 14.0.
4.2.8. 2-Acetyl-7-bromo-9,9-di-n-hexylfluorene (10)
Acetyl chloride of 1.8 mL (25.4 mmol, 1.05 equiv) is slowly
added at 0 ꢀC to a suspension of anhydrous AlCl3 (3.87 g,
29.0 mmol, 1.2 equiv) in dry CH2Cl2 (50 mL). A solution of
2-bromo-9,9-di-n-hexylfluorene (10.0 g, 24.2 mmol, 1 equiv)
in dry CH2Cl2 (30 mL) is added drop by drop and the mixture
is stirred at room temperature for 20 h. The mixture is poured
onto 40 g of ice and a solution of concd HCl is added until the
precipitate of Al(OH)3 dissolves. The organic layer is separated
and the aqueous phase is extracted twice with CH2Cl2. (2ꢁ
50 mL). The organic phases are combined, washed with water
(50 mL), 2% NaOH solution (50 mL), water (50 mL), brine
(50 mL), and dried over Na2SO4. After evaporation of the sol-
vents, theyellow oilobtainedispurified byflash chromatography
(pentane/CH2Cl2, 2:1) to give the product as a colorless oil
(10.25 g, 93%). (Found: C, 71.10; H, 7.87. C27H35BrO requires:
C, 71.20; H, 7.74%.) dH (300 MHz, CDCl3, Me4Si) 7.90e7.96
(2H, m, Ph), 7.69 (1H, d, J 8.3, Ph), 7.58 (1H, d, J 7.8, Ph),
7.48 (1H, s, Ph), 7.46(2H, d, J 7.8, Ph), 2.63 (3H, s, COCH3),
2.02e1.90 (4H, m, 2ꢁCCH2), 1.12e0.99 (12H, m, 2ꢁCH2CH2-
CH2CH3), 0.73 (6H, t, J 6.7, 2ꢁCH2CH3), 0.61e0.48 (4H, m,
2ꢁCCH2CH2). dC (50.3 MHz, CDCl3, Me4Si) 197.4, 153.7,
150.2, 144.4, 138.3, 135.7, 129.8, 127.8, 125.9, 122.2, 121.9,
121.5, 119.1, 55.2, 39.6, 30.9, 29.0, 26.3, 23.2, 22.0, 13.5.
4.2.11. 2-n-Hexyloxy-7-bromo-9,9-di-n-hexylfluorene (13)
To a solution of 7-bromo-9,9-di-n-hexylfluoren-2-ol (1.25 g,
2.92 mmol, 1 equiv) and 1-bromohexane (0.45 mL, 3.21 mmol,
1.1 equiv) in acetonitrile (20 mL) is added K2CO3 (805 mg,
5.82 mmol, 2 equiv). The mixture is stirred at 82 ꢀC for 20 h. Af-
ter cooling to room temperature, the mixture is added to distilled
water (40 mL) and extracted with diethyl ether (3ꢁ40 mL). The
organic phases are combined, washed with water (50 mL), brine
(50 mL), and dried over Na2SO4. After evaporation of the sol-
vents and purification by flash chromatography (pentane/
CH2Cl2, 1:4), the product is obtained as a white solid (1.27 g,
85%). (Found: C, 72.69; H, 8.77. C31H45BrO requires: C,
72.50; H, 8.83%.) Mp 39 ꢀC. dH (200 MHz, CDCl3, Me4Si)
7.56e7.35 (4H, m, Ph), 6.90e6.76 (2H, m, Ph), 3.99 (2H, m,
OCH2), 1.93e1.70 (6H, m, OCH2CH2þ2ꢁCCH2), 1.58e1.26
(6H, m, OCH2CH2CH2CH2CH2CH3), 1.20e0.95 (12H, m, 2ꢁ
CH2CH2CH2CH3), 0.89 (3H, t, J 6.9, OCH2CH2CH2CH2-
CH2CH3), 0.71 (6H, t, J 6.9, 2ꢁCH2CH3), 0.68e0.50 (4H, m,
2ꢁCCH2CH2). dC (50.3 MHz, CDCl3, Me4Si) 159.5, 152.5,
152.3, 140.3, 133.0, 129.8, 126.0, 120.5, 120.2, 119.7, 113.0,
109.5, 68.4, 55.4, 40.5, 31.7, 31.5, 29.7, 29.4, 25.9, 23.7, 22.7,
22.6, 14.1, 14.0.
4.2.9. 7-Bromo-9,9-di-n-hexylfluoren-2-yl acetate (11)
m-CPBA of 6 g (77%, 26.8 mmol, 1.6 equiv) is slowly added
to a solution of 2-acetyl-7-bromo-9,9-di-n-hexylfluorene (7.5 g,
16.5 mmol, 1 equiv) in CHCl3 (150 mL). The mixture is stirred
in the dark at room temperature for 4 days, washed with
NaHCO3 (100 mL), water (100 mL), brine (100 mL), and dried

408
A. Picot et al. / Tetrahedron 64 (2008) 399e411
4.2.12. 2-(7-Hexyloxy-9,90-dihexylfluorenyl)trimethyl-
silylacetylene (14)
Me4Si) 8.24 (1H, dd, J 8.3 and 2.1, Ph), 8.16 (1H, d, J 1.9,
Ph), 7.77e7.69 (3H, m, Ph) 7.50 (1H, d, J 8.3, Ph), 2.03e1.92
(4H, m, 2ꢁCCH2), 1.11e1.03 (12H, m, 2ꢁCH2CH2CH2CH3),
0.75 (6H, t, J 6.2, 2ꢁCH2CH3), 0.58e0.51 (4H, m, 2ꢁCCH2-
CH2). dC (50.3 MHz, CDCl3, Me4Si) 154.5, 151.4, 147.5,
146.5, 138.3, 136.6, 132.5, 123.4, 122.7, 120.0, 118.2, 95.5,
55.9, 39.9, 31.4, 29.45, 23.7, 22.5, 13.9.
Prepared according to general procedure Awith 2-hexyloxy-
7-bromo-9,9-di-n-hexylfluorene: 606 mg, 1.18 mmol, 1 equiv;
DMF: 14 mL; Et3N: 1.64 mL, 11.8 mmol, 10 equiv; trimethyl-
silylacetylene: 1.67 mL, 11.8 mmol, 10 equiv; copper iodide:
44.8 mg, 0.236 mmol, 0.2 equiv; Pd(PPh3)2Cl2: 82.8 mg,
0.118 mmol, 0.1 equiv; temperature: 115 ꢀC; time: 3 days; chro-
matography: pentane; product: yellow oil (520 mg, 84%).
(Found: C, 81.11; H, 10.01. C36H54OSi requires: C, 81.44; H,
10.25%.) dH (200 MHz, CDCl3, Me4Si) 7.59e7.38 (4H, m,
Ph), 6.90e6.82 (2H, m, Ph), 3.99 (2H, m, OCH2), 1.95e1.72
(6H, m, OCH2CH2þ2ꢁCCH2), 1.58e1.26 (6H, m, OCH2CH2-
CH2CH2CH2CH3), 1.20e0.95 (12H, m, 2ꢁCH2CH2CH2CH3),
0.90 (3H, t, J 6.9, OCH2CH2CH2CH2CH2CH3), 0.75 (6H, t, J
7.0, 2ꢁCH2CH3), 0.68e0.50 (4H, m, 2ꢁCCH2CH2), 0.27
(9H, s, Si(CH3)3). dC (50.3 MHz, CDCl3, Me4Si) 159.5, 153.1,
150.1, 141.8, 133.3, 131.2, 126.1, 120.8, 119.9, 118.6, 113.0,
109.4, 106.6, 93.3, 77.2, 68.4, 55.1, 40.6, 31.7, 31.6, 29.7,
29.4, 25.8, 23.6, 22.6, 14.1, 14.0, ꢂ0.1.
4.2.15. 2-Amino-7-iodo-9,9-di-n-hexylfluorene (17)
A mixture of 2-nitro-7-iodo-9,9-di-n-hexylfluorene (5.55 g,
11.0 mmol, 1 equiv) and iron powder (Aldrich-325 mesh,
3.07 g, 54.9 mmol, 5 equiv) in glacial acetic acid (130 mL) is
heated to boiling. The heat is stopped and, once the boiling stops,
more iron powder (Aldrich-325 mesh, 1.23 g, 21.96 mmol,
2 equiv) is added. The mixture is first stirred at 118 ꢀC for
30 min, then cooled down to room temperature, and added to
10 mL distilled water. The mixture is sonicated for 10 min and
filtered. The brown solid obtained is washed with water and
dissolved in CH2Cl2. This solution is then washed with water,
saturated aqueous NaHCO3, brine, dried over Na2SO4, and
evaporated under vacuum. The crude yellow solid is purified
by chromatography (pentane/ethyl acetate, 4:1) to give the prod-
uct as a light brown solid (3.60 mg, 69%.) (Found: C, 63.07; H,
7.35; N, 2.75. C25H34IN requires: C, 63.15; H, 7.21; N, 2.95%.)
Mp 39 ꢀC. dH (200 MHz, CDCl3, Me4Si) 7.58e7.55 (2H, m,
Ph), 7.41 (1H, d, J 8.6, Ph), 7.27 (1H, d, J 8.4, Ph), 6.64e6.60
(2H, m, Ph), 3.76 (2H, s, NH2), 1.86 (4H, t, J 8.2, 2ꢁCCH2),
1.25e1.06 (12H, m, 2ꢁCH2CH2CH2CH3), 0.78 (6H, t, J
6.2, 2ꢁCH2CH3), 0.65e0.53 (4H, m, 2ꢁCCH2CH2). dC
(50.3 MHz, CDCl3, Me4Si) 152.3, 152.16, 146.56, 141.3,
135.6, 131.7, 131.3, 120.7, 120.1, 114.0, 109.5, 90.2, 55.0,
40.5, 31.5, 29.7, 23.7, 22.6, 14.1.
4.2.13. 2-(7-Hexyloxy-9,90-dihexylfluorenyl)acetylene (15)
K2CO3 of 285 mg (2.05 mmol, 2.6 equiv) is added to a solu-
tion of 2-(7-hexyloxy-9,90-dihexylfluorenyl)trimethylsilylace-
tylene (420 mg, 0.8 mmol, 1 equiv) in THF/methanol (20 mL,
1:1). The mixture is stirred at room temperature for 3 h and
30 mL of pentane is added. The remaining K2CO3 is filtered,
and after evaporation of the solvents and purification by flash
chromatography (pentane/CH2Cl2, 1:9), the product is ob-
tained as a yellow oil (0.355 g, 95%). (Found: C, 86.22; H,
9.88. C33H46O requires: C, 86.40; H, 10.11%.) dH
(200 MHz, CDCl3, Me4Si) 7.65e7.35 (4H, m, Ph), 6.90e
6.81 (2H, m, Ph), 3.99 (2H, m, OCH2), 3.08 (1H, s, CCH ),
1.98e1.76 (6H, m, OCH2CH2þ2ꢁCCH2), 1.58e1.26 (6H,
m, OCH2CH2CH2CH2CH2CH3), 1.20e0.95 (12H, m, 2ꢁCH2-
CH2CH2CH3), 0.89 (3H, t, J 6.9, OCH2CH2CH2CH2CH2CH3),
0.74 (6H, t, J 7.0, 2ꢁCH2CH3), 0.68e0.51 (4H, m, 2ꢁCCH2-
CH2). dC (50.3 MHz, CDCl3, Me4Si) 159.6, 153.1, 150.2,
142.1, 133.2, 131.2, 126.3, 120.8, 118.8, 118.7, 113.1,
109.4, 85.0, 77.2, 76.5, 68.4, 55.1, 40.5, 31.7, 31.5, 29.7,
29.4, 25.8, 23.6, 22.6, 14.1, 14.
4.2.16. N,N-Dihexyl-2-amino-7-iodo-9,9-
di-n-hexylfluorene (18)
To a solution of 2-amino-7-iodo-9,9-di-n-hexylfluorene
(1.66 g, 3.49 mmol, 1 equiv), 1-bromohexane (1.97 mL,
13.97 mmol, 4 equiv), and sodium iodide (2.09 g, 13.97 mmol,
4 equiv) in dry DMF (18 mL) is added Na2CO3 (666 mg,
6.28 mmol, 1.8 equiv). The mixture is stirred at 95 ꢀC for
20 h. After cooling to room temperature, the mixture is added
to distilled water (40 mL) and extracted with diethyl ether
(3ꢁ40 mL). The organic layers are combined, washed with
water (50 mL), brine (50 mL), and dried over Na2SO4. After
evaporation of the solvents, the brown oil obtained is purified
by flash chromatography (pentane/CH2Cl2, 9:1) to give the
product as a light yellow oil (1.6 g, 71%). (Found: C, 68.78;
H, 9.32; N, 2.27. C37H58IN requires: C, 69.03; H, 9.08; N,
2.18%.) dH (200 MHz, CDCl3, Me4Si) 7.55e7.51 (2H, m, Ph),
7.44 (1H, d, J 8.4, Ph), 7.24 (1H, d, J 7.3, Ph), 6.58 (1H, d, J
8.4, Ph), 6.53 (1H, m, Ph), 3.30 (4H, t, J 7.5, 2ꢁNCH2), 1.88e
1.80 (4H, m, 2ꢁNCH2CH2), 1.60e1.51 (4H, m, 2ꢁCCH2),
1.39e1.23 (12H, m, 2ꢁNCH2CH2CH2CH2CH2CH3), 1.12e
0.99 (12H, m, 2ꢁCCH2CH2CH2CH2CH2CH3), 0.88 (6H, t,
J 6.8, 2ꢁNCH2CH2CH2CH2CH2CH3), 0.78 (6H, t, J 6.2, 2ꢁ
CCH2CH2CH2CH2CH2CH3),0.72e0.60(4H,m,2ꢁCCH2CH2).
dC (50.3 MHz, CDCl3, Me4Si) 152.4, 151.8, 148.5, 141.7,
4.2.14. 2-Iodo-7-nitro-9,9-di-n-hexylfluorene (16)
A 50% aqueous solution of NaOH (3.8 mL, 72.4 mmol,
7 equiv) is added under argon to a solution of 2-iodo-7-nitro-
fluorene (3.5 g, 10.4 mmol, 1 equiv) and triethylbenzylammo-
nium chloride (130 mg, 0.57 mmol, 0.055 equiv) in DMSO
(35 mL). Once the mixture becomes dark green, 4.39 mL of 1-
bromohexane (31.2 mmol, 3 equiv) is added drop by drop and
the mixture is stirred at room temperature for 20 h. An excess
of ethyl acetate is added (50 mL) and the organiclayeris filtered,
washed with 10 M HCl (50 mL), water (50 mL), brine (50 mL),
and dried over Na2SO4. After evaporation of the solvents, the
crude red oil is purified by chromatography (pentane/CH2Cl2,
6:1) to give product as a light yellow solid (4.77 g, 91%).
(Found: C, 59.44; H, 6.43; N, 2.80. C25H32INO2 requires: C,
59.41; H, 6.18; N, 2.77%.) Mp 65 ꢀC. dH (200 MHz, CDCl3,

A. Picot et al. / Tetrahedron 64 (2008) 399e411
409
135.5, 131.5, 138.0, 120.5, 119.7, 110.8, 106.1, 89.1, 55.0, 51.5,
40.5, 31.8, 31.5, 29.7, 27.2, 26.9, 23.7, 22.65, 22.60, 14.03,
14.01.
(6H, t, J 7.1, 2ꢁNCH2CH3), 1.08 (6H, t, J 7.1, 2ꢁNCH2CH3),
0.89 (3H, J 7.1, OCH2CH2CH2CH2CH2CH3). dC (50.3 MHz,
CDCl3, Me4Si) 166.8, 159.9, 154.2, 133.13, 133.15, 123.2,
114.4, 112.7, 95.0, 84.4, 67.6, 42.4, 39.0, 30.8, 28.3, 24.8,
21.8, 13.1, 12.8, 11.6. m/z 500.2894 (MNaþ. C29H39NaN3O3
requires 500.2889).
4.2.17. N,N-Bis(4-(diethylamino)phenyl)pyridine-2,6-
dicarboxamide (L1)
0
The procedure for the synthesis of L1 was used. p-N,N-
diethylaminoaniline: 5.01 g, 30.5 mmol, 5 equiv; pyridine-
2,6-dicarbonyl dichloride: 1.25 g, 6.1 mmol, 1 equiv; product:
light green crystals (2.4 g, 90%). lmax (CH2Cl2)/nm 360
(3/dm3 molꢂ1 cmꢂ1 13,900). nmax/cmꢂ1 1670 (CO). dH
(200 MHz, CDCl3, Me4Si) 9.62 (2H, s, 2ꢁNH ), 8.40 (2H,
d, J 7.6, Ph), 8.06 (1H, t, J 7.6, Ph), 7.55 (4H, d, J 8.8, Ph),
6.64 (4H, d, J 8.8, Ph), 3.36 (8H, q, J 7.0, 4ꢁNCH2), 1.18
(12H, t, J 7.0, 4ꢁCH3). dC (50.3 MHz, CDCl3, Me4Si)
161.5, 149.7, 145.8, 139.4, 126.2, 125.1, 123.0, 112.2,
44.8, 12.8. m/z 498.2248 (MKþ. C27H33KN5O2 requires
498.2271).
4.2.20. Dimethyl 4-((4-hexyloxyphenyl)ethynyl)pyridine-2,6-
0
dicarboxylate (L2 )
Prepared according to general procedure A with, experi-
ment 1: dimethyl 4-bromopyridine-2,6-dicarboxylate: 1.0 g,
3.65 mmol, 1 equiv; THF: 20 mL; Et3N: 5 mL; 4-(hexyloxy)-
phenylacetylene: 738 mg, 3.65 mmol, 1 equiv; copper iodide:
69.5 mg, 0.365 mmol, 0.1 equiv; Pd(PPh3)2Cl2: 128.1 mg,
0.183 mmol, 0.05 equiv; temperature: 66 ꢀC; time: 20 h; chro-
matography: pure CH2Cl2 followed by CH2Cl2/ethyl acetate
from 4:1; product: white solid (600 mg, 45%). Experiment 2: di-
methyl 4-iodopyridine-2,6-dicarboxylate: 1.17 g, 3.65 mmol,
1 equiv; THF: 20 mL; Et3N: 5 mL; 4-(hexyloxy)phenylacety-
lene: 738 mg, 3.65 mmol, 1 equiv; copper iodide: 69.5 mg,
0.365 mmol, 0.1 equiv; Pd(PPh3)2Cl2: 128.1 mg, 0.183 mmol,
0.05 equiv; temperature: 40 ꢀC; time: 5 h; product recrystal-
lized from methanol: white solid (1.24 g, 93%). (Found:
C, 69.90; H, 6.41; N, 3.28. C23H25NO5 requires: C, 69.86;
H, 6.37; N, 3.54%.) Mp 117 ꢀC. lmax (CH2Cl2)/nm 336
(3/dm3 molꢂ1 cmꢂ1 20,400). nmax/cmꢂ1 2216 (CC), 1720
(CO). dH (200 MHz, CDCl3, Me4Si) 8.35 (2H, s, Ph), 7.52
(2H, d, J 8.9, Ph), 6.92 (2H, d, J 8.9, Ph), 4.06 (6H, s, COOCH3),
4.01 (2H, t, J 6.5, OCH2), 1.90e1.70 (2H, m, OCH2CH2), 1.55e
1.30 (6H, m, OCH2CH2CH2CH2CH2), 0.95 (3H, t, J 6.6,
OCH2CH2CH2CH2CH2CH3). dC (50.3 MHz, CDCl3, Me4Si)
165.2, 160.9, 148.7, 135.4, 134.3, 129.8, 115.1, 113.4, 98.1,
85.0, 68.6, 53.7, 32.0, 29.5, 26.1, 23.0, 14.1.
4.2.18. N,N-Bis(4-(dibutylamino)phenyl)pyridine-2,6-
0
dicarboxamide (L1 )
p-N,N-Dibutylaminoaniline of 6.0 g (27.2 mmol, 5 equiv) is
added to a 10 mL CH2Cl2 solution of pyridine-2,6-dicarbonyl di-
chloride prepared in situ (1.11 g, 5.45 mmol, 1 equiv, see prepa-
ration of 5). After stirring at 40 ꢀC for 2 h, the acidic mixture is
quenched to neutral pH by the addition of a saturated aqueous
solution of K2CO3. After extraction, the organic phase is dried
(Na2SO4) and evaporated. The crude product is recrystallized
twice from heptane to give 1.9 g (61%) of light green crystals.
(Found: C, 60.08; H, 7.61; N, 8.85. C35H49N5O2$2CH2Cl2
requires: C, 59.92; H, 7.20; N, 9.44%.) lmax (CH2Cl2)/nm
360 (3/dm3 molꢂ1 cmꢂ1 13,900). nmax/cmꢂ1 1671 (CO). dH
(200 MHz, CDCl3, Me4Si) 9.40 (2H, s, 2ꢁNH ), 8.46 (2H, d, J
7.7, Ph), 8.10 (1H, t, J 7.7, Ph), 7.58 (4H, d, J 8.9, Ph), 6.68
(4H, d, J 8.9, Ph), 3.29 (8H, t, J 7.1, 4ꢁNCH2), 1.67e1.56
(16H, m, 4ꢁNCH2CH2CH2), 0.98 (12H, t, J 7.1, 4ꢁCH3). dC
(50.3 MHz, CDCl3, Me4Si) 160.9, 149.4, 145.9, 139.1, 125.6,
124.2, 122.3, 111.7, 52.8, 29.4, 20.3 13.8. m/z 610.3526
(MKþ. C35H49KN5O2 requires 610.3523).
4.2.21. 4-((4-Hexyloxyphenyl)ethynyl)pyridine-2,6-
00
dicarboxylic acid (L2 )
Dimethyl 4-((4-hexyloxyphenyl)ethynyl)pyridine-2,6-di-
carboxylate of 500 mg (1.26 mmol, 1 equiv) is added to a solu-
tion of sodium hydroxide (151 mg, 3.78 mmol, 3 equiv) in
water/methanol (15 mL, 19:1). After stirring at 100 ꢀC for
15 h, the solution is cooled down to room temperature and is
acidified to pH¼2 by the addition of a 1 mol Lꢂ1 HCl solution.
The precipitate obtained is filtered, washed with water, tritu-
rated with pentane, and dried under vacuum to give 510 mg
(99%) of a white solid. (Found: C, 60.65; H, 5,72; N, 3.11.
C21H21NO5$H2O$HCl requires: C, 59.79; H, 5.54; N,
3.32%.) lmax (CH2Cl2)/nm 346 (3/dm3 molꢂ1 cmꢂ1 25,700).
nmax/cmꢂ1 2231 (CC), 1743 (CO). dH (200 MHz, CDCl3,
Me4Si) 8.14 (2H, s, Ph), 7.61 (2H, d, J 8.7, Ph), 7.02 (2H,
d, J 8.7, Ph), 4.03 (2H, t, J 6.4, OCH2), 1.80e1.60 (2H, m,
OCH2CH2), 1.50e1.20 (6H, m, OCH2CH2CH2CH2CH2),
4.2.19. 4-(4-(Hexyloxyphenyl)acetylene)-2,6-
di(diethylcarbamoyl)pyridine (L2)
Prepared according to general procedure A with 4-iodo-2,6-
di(diethylcarbamoyl)pyridine: 1.5 g, 3.7 mmol, 1 equiv; THF:
20 mL; Et3N: 20 mL; 4-(hexyloxy)phenylacetylene: 830 mg,
4.1 mmol, 1.1 equiv; copper iodide: 140 mg, 0.74 mmol,
0.2 equiv; Pd(PPh3)2Cl2: 260 mg, 0.37 mmol, 0.1 equiv; tem-
perature: 40 ꢀC; time: 72 h; chromatography: gradient pen-
tane/ethyl acetate from 9:1 to 1:1; product: pale yellow solid
(1.576 g, 89%). (Found: C, 72.93; H, 8.29; N, 8.27.
C29H39N3O3 requires: C, 72.92; H, 8.23; N, 8.80%.) Mp
84 ꢀC. lmax (CH2Cl2)/nm 320 (3/dm3 molꢂ1 cmꢂ1 28,600).
nmax/cmꢂ1 2202 (CC), 1624 (CO). dH (200 MHz, CDCl3,
Me4Si) 7.59 (2H, s, Ph), 7.51 (2H, d, J 8.9, Ph), 6.94 (2H, t,
J 8.9, Ph), 4.00 (2H, t, J 6.5, OCH2), 3.48 (4H, q, J 7.1,
2ꢁNCH2), 3.25 (4H, q, J 7.1, 2ꢁNCH2), 1.74 (2H, m,
OCH2CH2), 1.35 (6H, m, OCH2CH2CH2CH2CH2), 1.18
0.88 (3H, t,
J
5.8, OCH2CH2CH2CH2CH2CH3). dC
(50.3 MHz, CDCl3, Me4Si) 165.8, 160.4, 151.1, 134.3,
133.5, 127.6, 115.5, 113.3, 96.5, 85.7, 68.2, 31.4, 29.0, 25.6,
22.5, 14.4.

410
A. Picot et al. / Tetrahedron 64 (2008) 399e411
4.2.22. 4-(N,N-Dihexyl-4-ethynylaniline)-2,6-
chromatography: pentane/ethyl acetate (2:1); product: yellow oil
(430 mg, 59%). (Found: C, 76.49; H, 9.72; N, 6.26.
C54H80N4O2$2H2O requires: C, 76.01; H, 9.92; N, 6.57%.) Mp
di(diethylcarbamoyl)pyridine (L3)
Prepared according to general procedure A with 4-iodo-2,6-
di(diethylcarbamoyl)pyridine: 1.298 g, 3.2 mmol, 1 equiv;
THF: 20 mL; Et3N: 20 mL; N,N-dihexyl-4-ethynylaniline:
1.029 g, 3.5 mmol, 1.1 equiv; copper iodide: 136 mg,
0.7 mmol, 0.2 equiv; Pd(PPh3)2Cl2: 251 mg, 0.3 mmol,
0.09 equiv; temperature: 40 ꢀC; time: 72 h; chromatography:
gradient pentane/ethyl acetate from 4:1 to 2:1; product: orange
solid (982 mg, 53%). (Found: C, 75.04; H, 9.38; N, 9.78.
C35H52N4O2 requires: C, 74.96; H, 9.35; N, 9.99%.) Mp
101 ꢀC. lmax (CH2Cl2)/nm 379 (3/dm3 molꢂ1 cmꢂ1 40,800).
nmax/cmꢂ1 2203 (CC), 1625 (CO). dH (200 MHz, CDCl3,
Me4Si) 7.47 (2H, s, Ph), 7.35 (2H, d, J 9.0, Ph), 6.64 (2H, d, J
9.0, Ph), 3.48 (4H, q, J 7.2, 2ꢁCONCH2), 3.60e3.30 (8H, m,
2ꢁCONCH2þ2ꢁNCH2), 1.70e1.45 (4H, m, 2ꢁNCH2CH2),
145e1.20 (12H, m, 2ꢁNCH2CH2CH2CH2CH2), 1.18 (6H, t, J
7.2, 2ꢁNCH2CH3), 1.08 (6H, t, J 7.2, 2ꢁNCH2CH3), 0.88
(3H, t, J 6.4, 2ꢁNCH2CH2CH2CH2CH2CH3). dC (50.3 MHz,
CDCl3, Me4Si) 166.9, 154.2, 148.6, 133.8, 132.9, 122.2,
110.9, 105.7, 97.4, 84.0, 49.9, 42.4, 39.0, 30.9, 26.3, 25.8,
21.9, 13.1, 12.8, 11.6.
84 ꢀC. lmax (CH2Cl2)/nm 402 (3/dm3 molꢂ1 cmꢂ1 37,300). nmax
/
cmꢂ1 2203 (CC), 1640 (CO). dH (200 MHz, CDCl3, Me4Si) 7.56
(2H, s, Ph), 7.55e7.45 (4H, m, Ph), 6.67e6.59 (2H, m, Ph), 3.49
(4H, q, J 7.1, 2ꢁNCH2), 3,32 (4H, q, J 7.3, 2ꢁNCH2), 3.27 (4H,
q, J 7.1, 2ꢁNCH2), 1.58 (4H, m, 2ꢁCCH2), 1.40e1.90 (40H, m,
4ꢁNCH2CH3þ14ꢁCH2), 0.88 (6H, t, J 6.8, NCH2CH2CH2-
CH2CH2CH3), 0.74 (6H, t, J 6.9, 2ꢁCCH2CH2CH2CH2-
CH2CH3), 0.55 (4H, m, 2ꢁCH2). dC (50.3 MHz, CDCl3, Me4Si)
167.7, 153.8, 153.1, 149.9, 148.7, 143.8, 134.3, 131.2, 128.0,
126.0, 125.1, 121.1, 117.9, 116.8, 110.9, 106.0, 98.0, 85.7, 54.8,
51.5, 43.3, 40.6, 40.1, 31.8, 31.5, 29.7, 27.2, 26.9, 23.7, 22.6
22.5, 14.3, 14.1, 14.0, 12.8.
Acknowledgements
Authors acknowledge the Agence Nationale pour la Re-
cherche (LnOnL, ANR-NT05-3_42676) for financial support.
B.L.G. thanks IDRIS for computing facilities.
4.2.23. 4-(2-(7-Hexyloxy-9,90-dihexylfluorenyl)ethynyl)-2,6-
di(diethylcarbamoyl)pyridine (L4)
References and notes
Prepared according to general procedure A with 4-iodo-2,6-
di(diethylcarbamoyl)pyridine: 271 mg, 0.672 mmol, 1 equiv;
THF: 20 mL; Et3N: 10 mL; 2-(7-hexyloxy-9,90-dihexylfluore-
nyl)acetylene: 308 mg, 0.672 mmol, 1 equiv; copper iodide:
25.5 mg, 0.134 mmol, 0.2 equiv; Pd(PPh3)2Cl2: 47.2 mg,
0.0672 mmol, 0.1 equiv; temperature: 50 ꢀC; time: 20 h; chro-
matography: pentane/ethyl acetate (2:1); product: pale yellow
solid (320 mg, 65%). (Found: C, 78.49; H, 9.25; N, 5.54.
C48H67N3O3 requires: C, 78.54; H, 9.20; N, 5.72%.) Mp
130 ꢀC. lmax (CH2Cl2)/nm 349 (3/dm3 molꢂ1 cmꢂ1 43,000).
nmax/cmꢂ1 2212 (CC), 1633 (CO). dH (200 MHz, CDCl3,
Me4Si) 7.67 (2H, s, Ph), 7.65e7.54 (2H, m, Ph), 7.48e7.42
(2H, m, Ph), 6.90e6.82 (2H, m, Ph), 4.00 (2H, t, J 6.6,
OCH2), 3.54 (4H, q, J 7.1, 2ꢁNCH2), 3.32 (4H, q, J 7.1,
2ꢁNCH2), 1.88 (6H, m, OCH2CH2þ2ꢁCCH2), 1.44 (2H, m,
CH2), 1.34 (4H, m, 2ꢁCH2), 1.24 (6H, t, J 7.1, 2ꢁNCH2CH3),
1.14 (6H, t, J 7.1, 2ꢁNCH2CH3), 1.03 (12H, m, 6ꢁCH2), 0.90
(6H, t, J 6.8, OCH2CH2CH2CH2CH2CH3), 0.74 (6H, t, J 7.1,
2ꢁCCH2CH2CH2CH2CH2CH3), 0.59 (4H, m, 2ꢁCH2). dC
(50.3 MHz, CDCl3, Me4Si) 167.7, 159.8, 153.8, 153.3, 150.4,
142.9, 134.1, 133.0, 131.2, 126.2, 125.2, 121.1, 118.9, 118.5,
113.2, 109.4, 97.4, 86.0, 68.3, 55.2, 43.3, 40.5, 40.2, 31.7,
31.5, 29.7, 29.3, 25.8, 23.7, 22.61 22.60, 14.3, 14.1, 14.0, 12.8.
1. For DPA coordination complexes, see: (a) Albertsson, J. Acta Chem.
Scand. 1970, 24, 1213e1229; (b) Ouali, N.; Bocquet, B.; Rigault, S.; Mor-
gantini, P.-Y.; Weber, J.; Piguet, C. Inorg. Chem. 2002, 41, 1436e1445;
(c) Devereux, M.; McCann, M.; Leon, V.; McKee, V.; Ball, R. J. Polyhe-
dron 2002, 21, 1063e1071; (d) Jackson, A.; Davis, J.; Pither, R. J.;
Rodger, A.; Hannon, M. J. Inorg. Chem. 2001, 40, 3964e3973; (e) Tse,
M. K.; Bhor, S.; Klawonn, M.; Anilkumar, G.; Jiao, H.; Dobler, C.; Span-
¨
¨
nenberg, A.; Magerlein, W.; Hugl, H.; Beller, M. Chem.dEur. J. 2006,
12, 1855e1874; (f) Yang, L.; Crans, D. C.; Miller, S. M.; La Cour, A.;
Anderson, O. P.; Kaszynski, P. M.; Godzala, M. E., III; Austin,
L. T. D.; Willsky, G. R. Inorg. Chem. 2002, 41, 4859e4871; (g) Kirillova,
M. V.; Guedes da Silva, M. F. C.; Kirillov, A. M.; Frausto da Silva, J. J. R.;
Pombeiro, A. J. L. Inorg. Chim. Acta 2007, 360, 506e512.
2. For DPE coordination complexes, see: Renaud, F.; Piguet, C.; Bernardi-
nelli, G.; Bunzli, J.-C. G.; Hopfengartner, G. Chem.dEur. J. 1997, 3,
¨
1660e1666.
3. For DPAM coordination complexes, see : (a) Renaud, F.; Piguet, C.;
Bernardinelli, G.; Bunzli, J.-C. G.; Hopfgartner, G. Chem.dEur. J.
¨
1997, 3, 1646e1659; (b) Kapoor, R.; Kataria, A.; Pathak, A.; Venugopa-
lan, P.; Hundal, G.; Kapoor, P. Polyhedron 2005, 24, 1221e1231.
4. (a) Chauvin, A.-S.; Gumy, F.; Imbert, D.; Bunzli, J.-C. G. Spectrosc. Lett.
¨
2004, 37, 517e532; (b) Jones, G., II; Vulley, V. I. Photochem. Photobiol.
Sci. 2002, 1, 925e933; (c) Werts, M. H. V.; Jukes, R. T. F.; Verhoeven,
J. W. Phys. Chem. Chem. Phys. 2002, 4, 1542e1548.
5. (a) Tancrez, N.; Feuvrie, C.; Ledoux, I.; Zyss, J.; Toupet, L.; Le Bozec,
H.; Maury, O. J. Am. Chem. Soc. 2005, 127, 13474e13475; (b)
´
D’Aleo, A.; Pompidor, G.; Elena, B.; Vicat, J.; Baldeck, P. L.; Toupet,
L.; Kahn, R.; Andraud, C.; Maury, O. ChemPhysChem 2007, 8, 2125e
2132.
4.2.24. 4-(20-(N,N-Dihexyl-70-amino-90,90-dihexylfluorene)-
ethynyl)-2,6-bis(diethylcarbamoyl)pyridine (L5)
6. Sugita, M.; Ishikawa, N.; Ishikawa, T.; Koshihara, S.-Y.; Kaizu, Y. Inorg.
Chem. 2006, 45, 1299e1304.
Prepared according to general procedure Awith N,N-dihexyl-
2-amino-7-iodo-9,9-di-n-hexylfluorene: 641 mg, 0.995 mmol,
1 equiv; THF: 30 mL; Et3N: 30 mL; 4-ethynyl-2,6-bis(diethyl-
carbamoyl)pyridine: 300 mg, 0.995 mmol, 1 equiv; copper
iodide: 30 mg, 0.16 mmol, 0.16 equiv; Pd(PPh3)2Cl2: 56 mg,
0.08 mmol, 0.08 equiv; temperature: 40 ꢀC; time: 43 h;
7. (a) Hopkins, T. A.; Bolender, J. P.; Metcalf, D. H.; Richardson, F. S. Inorg.
Chem. 1996, 35, 5347e5355 and 5356e5362; (b) Zhao, B.; Chen, X.-Y.;
Cheng, P.; Zheng, D. Z.; Liao, S.-P.; Yan, S.-P.; Jiang, Z.-H. J. Am. Chem.
´
Soc. 2004, 126, 15394e15395; (c) D’Aleo, A.; Toupet, L.; Rigaut, S.;
Andraud, C.; Maury, O. Opt. Mater. 2007, in press.
8. (a) Driesen, K.; Van Deun, R.; Gorler-Walrand, C.; Biennemans, K. Chem.
¨
Mater. 2004, 16, 1531e1535; (b) Minoofar, P. N.; Dunn, B. S.; Zink, J. I.

A. Picot et al. / Tetrahedron 64 (2008) 399e411
411
J. Am. Chem. Soc. 2005, 127, 2656e2665; (c) Sokolnicki, J.; Lendzie-
wicz, J.; Muller, G.; Riehl, J. P. Opt. Mater. 2005, 27, 1529e1536.
26. Millaruelo, M.; Oriol, L.; Pinol, M.; Saez, P. L.; Serrano, J. L. J. Photo-
chem. Photobiol. A: Chem. 2003, 155, 29e36.
9. Chauvin, A.-S.; Bunzli, J.-C. G.; Bochud, F.; Scopelliti, R.; Froidevaux, P.
¨
Chem.dEur. J. 2006, 12, 6852e6864.
27. Kauffman, J. M.; Moyna, G. J. Org. Chem. 2003, 68, 839e853.
28. Mitzel, F.; Boudon, C.; Gisselbrecht, J.-P.; Seiler, P.; Gross, M.; Diederich,
F. Helv. Chim. Acta 2004, 87, 1130e1157.
10. Hunag, B.; Prantil, M. A.; Gustafson, T. L.; Paquette, J. R. J. Am. Chem.
Soc. 2003, 125, 14518e14530.
´
29. Maury, O.; Viau, L.; Senechal, K.; Corre, B.; Guegan, J.-P.; Renouard, T.;
11. Storm, O.; Luning, U. Eur. J. Org. Chem. 2003, 3109e3116.
Ledoux, I.; Zyss, J.; Le Bozec, H. Chem.dEur. J. 2004, 10, 4454e4466.
30. Malone, J. F.; Murray, C. M.; Dolan, G. M.; Docherty, R.; Lavery, A. J.
Chem. Mater. 1997, 9, 2983e2989.
¨
12. (a) Froidevaux, P.; Harrofield, J. M.; Sobolev, A. N. Inorg. Chem. 2000,
39, 4678e4687; (b) Haino, T.; Matsumoto, Y.; Fukazawa, Y. J. Am.
Chem. Soc. 2005, 127, 8936e8937.
´
31. Le Borgne, T.; Benech, J.-M.; Floquet, S.; Bernardinelli, G.; Aliprandini,
13. For selected examples, see: (a) Vandevyver, C. D. B.; Chauvin, A.-S.;
Comby, S.; Bunzli, J.-C. G. Chem. Commun. 2007, 1716e1718; (b) Zeckert,
C.; Bettens, P.; Piguet, C. Dalton Trans. 2003, 3856e3868.
32. Altomare, A.; Burla, M. C.; Camalli, M.; Carscarano, G.; Giacovazzo, C.;
Guagliardi, A.; Moliterni, A. G. G.; Polidori, G.; Spagna, R. J. Appl.
Crystallogr. 1998, 31, 74e77.
¨
K.; Hamacek, J.; Senegas, J.-M.; Dalla-Favera, N.; Floquet, S.; Bernardi-
nelli, G.; Piguet, C. Angew. Chem., Int. Ed. 2005, 44, 7954e7958; (c)
Floquet, S.; Ouali, N.; Bocquet, B.; Bernardinelli, G.; Imbert, D.; Bunzli,
¨
33. Sheldrick, G. M. SHELX93: Program for the Refinement of Crystal Struc-
tures; University of Gottigen: Gottigen, Germany, 1993.
¨ ¨
34. Spek, A. L. PLATON, A Multipurpose Crystallographic Tool; Utrecht
University: Utrecht, The Netherlands, 1998.
J.-C. G.; Hopfengartner, G.; Piguet, C. Chem.dEur. J. 2003, 9, 1860e1875.
14. (a) Lessmann, J. J.; Horrocks, W. DeW., Jr. Inorg. Chem. 2000, 39, 3114e
3124; (b) Cantuel, M.; Bernardinelli, G.; Muller, G.; Riehl, J. P.; Piguet, C.
Inorg. Chem. 2004, 43, 1840e1849.
35. Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb,
M. A.; Cheeseman, J. R.; Montgomery, Jr.; Vreven, J. A. T.; Kudin,
K. N.; Burant, J. C.; Millam, J. M.; Iyengar, S. S.; Tomasi, J.; Barone,
V.; Mennucci, B.; Cossi, M.; Scalmani, G.; Rega, N.; Petersson, G. A.;
Nakatsuji, H.; Hada, M.; Ehara, M.; Toyota, K.; Fukuda, R.; Hasegawa,
J.; Ishida, M.; Nakajima, T.; Honda, Y.; Kitao, O.; Nakai, H.; Klene,
M.; Li, X.; Knox, J. E.; Hratchian, H. P.; Cross, J. B.; Adamo, C.;
Jaramillo, J.; Gomperts, R.; Stratmann, R. E.; Yazyev, O.; Austin, A. J.;
Cammi, R.; Pomelli, C.; Ochterski, J. W.; Ayala, P. Y.; Morokuma, K.;
Voth, G. A.; Salvador, P.; Dannenberg, J. J.; Zakrzewski, V. G.; Dapprich,
S.; Daniels, A. D.; Strain, M. C.; Farkas, O.; Malick, D. K.; Rabuck,
A. D.; Raghavachari, K.; Foresman, J. B.; Ortiz, J. V.; Cui, Q.; Baboul,
A. G.; Clifford, S.; Cioslowski, J.; Stefanov, B. B.; Liu, G.; Liashenko,
A.; Piskorz, P.; Komaromi, I.; Martin, R. L.; Fox, D. J.; Keith, T.;
Al-Laham, M. A.; Peng, C. Y.; Nanayakkara, A.; Challacombe, M.;
Gill, P. M. W.; Johnson, B.; Chen, W.; Wong, M. W.; Gonzalez, C.; Pople,
J. A. Gaussian 03, Revision B.04; Gaussian: Pittsburgh, PA, 2003.
36. (a) Lee, C. T.; Yang, W. T.; Parr, R. G. Phys. Rev. B 1988, 37, 785e789;
(b) Becke, A. D. J. Chem. Phys. 1993, 98, 5648e5652.
´
15. (a) Haldar, D.; Jiang, H.; Leger, J.-M.; Huc, I. Angew. Chem., Int. Ed.
2006, 45, 5483e5486; (b) Zhan, C.; Leger, J.-M.; Huc, I. Angew.
Chem., Int. Ed. 2006, 45, 4625e4628 and references therein.
16. (a) Muller, G.; Schmidt, B.; Jiricek, J.; Hopfengadner, G.; Riehl, J. P.;
Bunzli, J.-C. G.; Piguet, C. J. Chem. Soc., Dalton Trans. 2001, 2655e
¨
2662; (b) Chauvin, A.-S.; Gras, S.; Bunzli, J.-C. G. Org. Biomol. Chem.
¨
2003, 1, 737e740.
17. Werts, M. H. V.; Nerambourg, N.; Pelegry, D.; Le Grand, Y.; Blanchard-
Desce, M. Photochem. Photobiol. Sci. 2005, 4, 531e538.
18. (a) Takkalo, H.; Hanninen, E.; Kankare, J. Helv. Chim. Acta 1993, 73,
¨
877e883; (b) Lamture, J. B.; Iverson, B.; Hogan, M. E. Tetrahedron
Lett. 1996, 37, 6483e6486.
19. De Bettencourt-Dias, A.; Poloukhine, A. J. Phys. Chem. B 2006, 110,
25638e25645.
20. Barsu, C.; Fortrie, R.; Nowika, K.; Baldeck, P.; Vial, J.-C.; Barsella, A.;
`
Fort, A.; Hissler, M.; Bretonniere, Y.; Maury, O.; Andraud, C. Chem.
Commun. 2006, 4744e4746.
21. Picot, A.; Malvolti, F.; Le Guennic, B.; Baldeck, P. L.; Williams, J. A. G.;
Andraud, C.; Maury, O. Inorg. Chem. 2007, 46, 2659e2665.
22. (a) See Ref. 16a; (b) Cornejo, A.; Fraile, J. M.; Garcia, J. I.; Garcia-
Verdugo, E.; Gil, M. J.; Legarreta, G.; Luis, S. V.; Martinez-Merino, V.;
Mayoral, J. A. Org. Lett. 2002, 4, 3927e3930.
37. Nakatsuji, Y.; Bradshaw, J. S.; Tse, P. K.; Arena, G.; Wilson, B. E.; Dalley,
N. K.; Izatt, R. M. J. Chem. Soc., Chem. Commun. 1985, 749e751.
38. Markees, D. G.; Kidder, G. W. J. Am. Chem. Soc. 1956, 78, 4130e4132.
39. Koizumi, Y.; Seki, S.; Acharya, A.; Saeki, A.; Tagawa, S. Chem. Lett.
2004, 33, 1290e1291.
23. Kato, Y.; Okada, S.; Tomimoto, K.; Mase, T. Tetrahedron Lett. 2001, 42,
4849e4851.
`
40. (a) Mongin, O.; Porres, L.; Moreaux, L.; Mertz, J.; Blanchard-Desce, M.
24. Chessa, G.; Canovese, L.; Visentin, F.; Santo, C.; Seraglia, R. Tetrahedron
2005, 61, 1755e1763.
Org. Lett. 2002, 4, 719e722; (b) See Ref. 28.
41. Marhevka, V. C.; Ebner, N. A.; Sehon, R. D.; Hanna, P. E. J. Med. Chem.
1985, 28, 18e24.
25. Storm, O.; Luning, U. Eur. J. Org. Chem. 2002, 67, 3680e3685.
¨