Synthesis of quasi-linear and segmented bis- to penta-2,2'-bipyridine polytopic ligands built via a convergent approach

Article abstract of DOI:10.1021/jo000836k

Reliable and practical routes for the preparation of segmented oligomeric 2,2'-bipyridine-based ligands possessing rigid and conjugated spacers are presented. The first series of ligands bears a single alkyne function as a bridge and has been built by Pd(

Full text of DOI:10.1021/jo000836k

7814
J . Org. Chem. 2000, 65, 7814-7824
Syn th esis of Qu a si-Lin ea r a n d Segm en ted Bis- to
P en ta -2,2′-bip yr id in e P olytop ic Liga n d s Bu ilt via a Con ver gen t
Ap p r oa ch
Abderrahim Khatyr and Raymond Ziessel*
Laboratoire de Chimie, d’Electronique et de Photonique Mole´culaires, Associe´ au CNRS ESA-7008,
Ecole de Chimie, Mate´riaux, Polyme`res de Strasbourg (ECPM), 25 rue Becquerel,
67087 Strasbourg Cedex 02, France
ziessel@chimie.u-strasbg.fr
Received May 31, 2000
Reliable and practical routes for the preparation of segmented oligomeric 2,2′-bipyridine-based
ligands possessing rigid and conjugated spacers are presented. The first series of ligands bears a
single alkyne function as a bridge and has been built by Pd(0)-catalyzed cross-coupling reactions
between ethynylated and bromo-substituted derivatives of 2,2′-bipyridine (bipy). These new ligands
provide access to numerous hexameric, octameric, and decameric pyridine-based materials. Optimum
conditions were found with [Pd(PPh3)4] (6 mol %) in benzene containing diisopropylamine at 80
°C. The second series of soluble ligands was synthesized around a 1,4-diethynyl-2,5-didodecyloxy-
benzene bridging unit. The synthesis required a protection/deprotection methodology, as well as a
chemioselective palladium-catalyzed Sonogashira-Hagihara cross-coupling protocol to obtain the
target multitopic ligands. Within this strategy, the pivotal 15b, 17, and 19b intermediates bearing
one or two bipy and phenyl units are required and such entities have been isolated in excellent
yield. The products are highly soluble and photostable. In each case, the final step involves a double
cross-coupling reaction between the appropriate constituents, with the best preparative conditions
involving [Pd(PPh3)4] (6 mol %) in n-propylamine at 70 °C. The main advantage of this methodology
lies in its synthetic versatility and adaptability for creating multitopic metal-binding scaffolds with
a potentially large variety of bridging units and phenyl substituents. Spectroscopic data for the
new oligomers show a steady decrease in optical energy with an increasing degree of oligomerization.
The different results obtained with these ligands highlight the importance of the rigid 1,4-
diethynylphenyl linker in directing the outcome of the nanosized molecules.
In tr od u ction
tural determination of certain photosynthetic light-
harvesting complexes from purple bacteria has suggested
that these arrays effectively delocalize photons over a
large number of spatially isolated but chemically identi-
cal pigment molecules.8 This realization has stimulated
us to design and prepare conjugated ligands bearing
interconnected chelating centers. Furthermore, while a
variety of luminescent scaffolds are available, probes
based on electronically conjugated backbones offer some
significant advantages for a number of applications
where long-lived excited-state lifetimes and visible light
activation are important considerations.9 Within this
family of substances, we and others have found that
luminophoric centers connected via alkyne spacers are
promising synthetic targets with respect to material
The design and characterization of well-defined transi-
tion-metal complexes possessing interesting redox and/
or photochemical properties is a research area that is
attracting considerable interest.1 Most of these complexes
are constructed from aromatic polyimine ligands such as
2,2′-bipyridine (bipy) or 2,2′:6′,2′′-terpyridine (terpy).2,3
Because of their unique structural properties and syn-
thetic versatility, these emergent luminescent molecules
fulfill a pivotal role in the design of new optoelectronic
devices,4,5 as well as in the mimicry of natural photosyn-
thetic processes.6 In natural photosynthetic assemblies,
regular arrays of pigments serve as light-harvesting units
that direct incident photons toward a reaction center
where electron-transfer reactions occur.7 Recent struc-
(6) Gust, D.; Moore, T. A. Science 1989, 244, 35. Maruyama, K.;
Osuka, A. Pure Appl. Chem. 1990, 62, 1511. Wasielewski, M. R. Chem.
Rev. 1992, 92, 435. Steinberg-Yfrach, G.; Liddell, P. A.; Hung, S.-C.;
Moore, A. L.; Gust, D.; Moore, T. A. Nature 1997, 385, 239. Steinberg-
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Moore, T. A. Nature 1998, 392, 479.
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R. J .; Frank, H. A. Biochim. Biophys. Acta 1987, 895, 63. Deming-
Adams, B. Biochim. Biophys. Acta 1990, 1020, 1.
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Prince, S. M.; Freer, A. A.; Hawthornthwaite-Lawless, A. M.; Papiz,
M. Z.; Cogdel, R. J .; Isaacs, N. W. Nature 1995, 374, 517.
(9) Ziessel, R.; Hissler, M.; El-ghayoury, A.; Harriman, A. Coord.
Chem. Rev. 1998, 180, 1251.
(1) Balzani, V.; Scandola, F. Supramolecular Chemistry: Concepts
and Perspectives; Horwood: Chichester, U.K., 1991. Seminario, J . M.;
Tour, J . M. In Molecular ElectronicssScience and Technology; Aviran,
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10.1021/jo000836k CCC: $19.00 © 2000 American Chemical Society
Published on Web 10/14/2000

Synthesis of Polytopic Ligands
J . Org. Chem., Vol. 65, No. 23, 2000 7815
science applications.10,11 Furthermore, alkyne-based mod-
ules have been used extensively in the field of crystal
engineering,12 liquid crystals,13,14 and dendritic macro-
molecules.15,16
separated by a single alkyne bond or by a 1,4-diethy-
nylene-2,5-didocyloxybenzene moiety was attempted, and
full synthetic details are provided here. Solubility prob-
lems associated with the increasing number of polyaro-
matic units can be circumvented by the use of solubilizing
groups attached to the substituted phenylene unit. The
combination of bipy templates with coupling reactions
involving sp carbon centers illustrates the capacity of this
approach.
Our motivation for this work arises, in part, from our
desire to identify suitable luminophoric multimetallic
complexes that are able to display intramolecular photon
shuttling under visible light illumination. This concept,
involving long-lived triplet excited states, is illustrated
in insert I. This study complements an earlier prelimi-
nary report of the synthesis of these ligands.21
Several recent reports have described synthetic pro-
cedures for the step-by-step construction of rationally
designed oligomeric structures bearing appropriate co-
ordination sites. However, synthetic protocols for the
preparation of ditopic ligands bearing an increasing
number of spacer units are more commonplace, and some
of the resultant d8-block metal complexes display out-
standing redox and photophysical properties.17 We re-
cently found a convergent synthetic pathway for the
construction of back-to-back terpyridine ligands bearing
an increasing number of phenylene/ethynylene modules.
This strategy requires an iterative sequence of reactions
that extend the central spacer framework outward from
the 1,4-diethynylene-2,5-didocyloxybenzene core.18
2,2′-Bipyridine is well suited for the construction of
polychelating molecules because it is rigid and quasi-
planar when coordinated to a metallic center and forms
stable complexes with a inordinately wide range of
cations. It has also been shown that bipy itself can
function as a tunable bridge.19 Oligomeric pyridines have
been known for a long time; however, there are few
versatile synthetic routes, and poor solubility of the free
ligands render their proper characterization a difficult
task.20 We might surmise that the synthesis of segmented
ligands in which the chelating centers are bridged by one
ethynylene or a 1,4-diethynylphenylene module might
prove amenable to facile oligomerization. To test this
idea, the preparation of a variety of rigid ligands bearing
an increasing number of metal ion binding sites (1-5)
Resu lts a n d Discu ssion
Preorganized ligands are usually constructed via a
convergent strategy that consists of building suitably
equipped modules before assembling these blocks into an
appropriate array. When alkyne modules are used as
spacers, the different part of the ligand can be intercon-
nected by a palladium(0)-promoted cross-coupling reac-
tion.22,23 This stepwise synthetic approach, although
tedious in operation, permits the engineering of multi-
topic ligands displaying disparate shapes, sizes, sym-
metry axes, and/or coordination sites.24,25 As a first step
toward the preparation of quasi-linear and photostable
polypyridines based upon conjugated frameworks, we
choose to use segmented hexameric, octameric, and
decameric pyridine ligands (Scheme 1). The key to all of
this chemistry is the availability of 5-bromo-2,2′-bipyri-
dine and 5,5′-dibromo-2,2′-bipyridine which have previ-
ously been prepared by direct bromination of 2,2′-
bipyridine hydrobromide salt at 180 °C.23
This method of preparation has many advantages in
terms of brevity and adaptability. The pivotal intermedi-
ate 2 was readily synthesized by the cross-coupling of
5,5′-dibromo-2,2′-bipyridine with 5-ethynyl-2,2′-bipyri-
dine in the presence of catalytic amounts of [Pd0(PPh3)4].
It is notable that during this key step a side product,
assigned as the tritopic ligand 1, is formed in less than
10% isolated yield.23 This compound could be removed
easily from the reaction mixture, owing to its marked
insolubility. Derivative 2 is converted to intermediate 3a
(10) Maulding, D. R.; Roberts, B. G. J . Org. Chem. 1969, 34, 1734.
Tzalis, D.; Tor, Y. Chem. Commun. 1996, 1043. Tzalis, D.; Tor, Y. J .
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A. L.; Tor, Y. Inorg. Chem. 1998, 37, 1121. Ley, K. D.; Li, Y.; J ohson,
J . V.; Powell, D. H.; Schanze, K. S. Chem. Commun. 1999, 1749. J oshi,
H. S.; J amshidi, R.; Tor, Y. Angew. Chem., Int. Ed. Engl. 1999, 38,
2722. Siemeling, U.; Vorfeld, U.; Neumann, B.; Stammler, H.-G.;
Zanello, P.; Fabrizi de Biani, F. Eur. J . Inorg. Chem. 1999, 1.
(11) Harriman, A.; Ziessel, R. Coord. Chem. Rev. 1998, 171, 331.
(12) Venkataraman, D.; Gardner, G. B.; Lee, S.; Moore, J . S. J . Am.
Chem. Soc. 1995, 117, 11600.
(13) Zhang, J .; Moore, J . S. J . Am. Chem. Soc. 1994, 116, 2655.
(14) El-ghayoury, A.; Douce, L.; Ziessel, R.; Seghrouchni, R.; Skoul-
ios, A. Liq. Cryst. 1996, 21, 143.
(15) Constable, E. C.; Eich, O.; Housecroft, C. E. J . Chem. Soc.,
Dalton Trans. 1999, 1363.
(16) Devadoss, C.; Bharathi, P.; Moore, J . S. J . Am. Chem. Soc. 1996,
118, 9635.
(17) Ziessel, R. J . Chem. Educ. 1997, 74, 673. Hissler, M.; El-
ghayoury, A.; Harriman, A.; Ziessel, R. Angew. Chem., Int. Ed. Engl.
1998, 37, 1717. Harriman, A.; Hissler, M.; Trompette, O.; Ziessel, R.
J . Am. Chem. Soc. 1999, 121, 2516.
(18) Khatyr, A.; Ziessel, R. Tetrahedron Lett. 1999, 40, 5515.
(19) Balzani, V.; J uris, A.; Venturi, M.; Campagna, S.; Serroni, S.
Chem. Rev. 1996, 96, 759.
(21) Khatyr, A.; Ziessel, R. Tetrahedron Lett. 2000, 41, 3837.
(22) Ziessel, R.; Suffert, J .; Youinou, M.-T. J . Org. Chem. 1996, 61,
6535.
(23) Grosshenny, V.; Romero, F. M.; Ziessel, R. J . Org. Chem. 1997,
62, 1491.
(20) Burstall, F. H. J . Chem. Soc. 1938, 1662. Krohnke, F. Synthesis
1976, 1 and references therein.
(24) Ziessel, R. Synthesis 1999, 1839.
(25) Baxter, P. N. W. J . Org. Chem. 2000, 65, 1257.

7816 J . Org. Chem., Vol. 65, No. 23, 2000
Khatyr and Ziessel
Sch em e 1a
a
i
i
Key: (i) [Pd(PPh3)4] (6 mol %), benzene, Pr2NH, 80 °C; (ii) TMSCtCH, [Pd(PPh3)2Cl2] (6 mol %), CuI (10 mol %), THF, Pr2NH, rt;
i
(iii) K2CO3, CH3OH, rt; (iv) [Pd(PPh3)4] (6 mol %), benzene, Pr2NH, 80 °C.
by a Sonogashira-Hagihara coupling reaction26,27 using
(trimethylsilyl)acetylene and palladium(0) generated in
situ from palladium(II) and cuprous salts, while depro-
tection, leading to compound 3b, can be realized using
K2CO3 in a protic solvent. Subsequent cross-coupling of
stoichiometric amounts of 2 and 3b afforded the tet-
ratopic ligand 4 in good yield. Furthermore, double cross-
coupling of an excess of 3b with 5,5′-dibromo-2,2′-
bipyridine gives rise to the corresponding pentatopic
ligand 5 in fair yield. During this latter reaction, stepwise
formation of the tritopic ligand bearing a bromo sub-
stituent in the 5′ position (a functionalized analogue of
ligand 1) is clearly observed by thin-layer chromatogra-
phy but has not yet been isolated. As expected in light of
the increasing number of aromatic and alkyne fragments,
the target ligands are poorly soluble in most common
organic solvents. This limits their structural character-
ization by classical spectroscopic tools, but FAB+-MS, FT-
IR, and elemental analysis are in keeping with the
structural assignment. Despite their poor solubility, these
ligands coordinate cationic “Ru(bipy)2” metallofragments,
leading to formation of soluble tri-, tetra-, and penta-
nuclear complexes which have been fully characterized.
This, in turn, adds further confirmation for the assigned
molecular structure of the multisite ligands.28
To access new ligands possessing improved solubility
and to study their spectroscopic and luminescence prop-
erties, we have launched a new synthetic program aimed
at producing extended ligands. The first step has involved
exploring the chemistry of a monosubstituted 1,4-hyd-
roquinone. O-Alkylation of bromohydroquinone with
1-bromododecane under basic conditions affords the
trisubstituted derivative 6 (Scheme 2). A Sonogashira-
Hagihara coupling reaction between 6 and propargylic
alcohol, followed by deprotection under basic conditions,
gives rise to the terminal alkyne derivative 8 in 66%
overall yield, starting from commercially available ma-
terials. Coupling of 8 with either 5-bromo-2,2′-bipyridine
or 5,5′-dibromo-2,2′-bipyridine is straightforward and
yields respectively the mono- or disubstituted single bipy
framework in acceptable yield (Scheme 2). Prior inves-
tigation into the synthesis of alkyne-grafted bipyridine
has shown that conventional triphenylphosphine-ligated
palladium catalysts are not poisoned by the presence of
strongly chelating bipy fragments, and this finding has
been confirmed here.23 Furthermore, the mono- and
disubstituted bipy ligands 9 and 10 are considered to be
important control compounds for additional spectroscopic
(26) Sonogashira, K.; Tohda, Y.; Hagihara, N. Tetrahedron Lett.
1975, 16, 4467. Takahashi, S. N.; Kuroyama, Y.; Sonogashira, K.;
Hagihara, N. Synthesis 1980, 627.
(27) Sonogashira, K. In Comprehensive Organic Synthesis; Trost,
B. M., Fleming, L., Paquette, L. A., Eds.; Pergamon Press: Oxford,
1990; Vol. 3, pp 545-547.
(28) Khatyr, A.; Harriman, A.; Ziessel, R. Manuscript in preparation.
(29) Ley, K. D.; Whittle, C. E.; Bartberger, M. D.; Schanze, K. S. J .
Am. Chem. Soc. 1997, 119, 3423.

Synthesis of Polytopic Ligands
J . Org. Chem., Vol. 65, No. 23, 2000 7817
Sch em e 2a
a
Key: (i) 1-bromododecane, NaOH, DMF, 100 °C; (ii) (CH3)2C(OH)C≡CH, nPrNH2, [Pd0(PPh3)4] (6 mol %), 70 °C; (iii) NaOH (excess),
benzene, 80 °C; (iv) nPrNH2, [Pd0(PPh3)4] (6 mol %), 70 °C.
studies. An analogue of ligand 10 bearing methoxy
groups in place of dodecyloxy substituents has recently
been used as a model compound during the study of
π-conjugated polymeric chromophores.29
module to the dibromo/bipy substrate is observed by thin-
layer chromatography to be a minor pathway, and this
is in keeping with a favorable reactivity of the second
pyridine-Br bond. The grafting of the first module, which
has a pronounced σ-inductive electron-withdrawing ef-
fect,30 might be expected to induce polarization of the
second C-Br bond such that subsequent oxidative ad-
dition to the low-valent palladium(0) metal center is
facilitated during the catalytic process.31 Double substi-
tution of the dibromo/bipy species is likely promoted by
any excess of the alkyne precursor. The good overall yield
(63% for three steps) underlines the efficiency of this
synthetic protocol.
Synthesis of the segmented hexapyridine ligand 16
relies upon the fact that no apparent side reaction is
observed, and this is auspicious for the preparation of
larger multisite ligands. Indeed, preparation of two
additional precursors has been undertaken (Scheme 4).
We selected a convergent synthesis that requires prepa-
ration of key intermediate 17, bearing an additional
bromo group with respect to the ditopic ligand 14. This
intermediate was prepared by monocoupling of interme-
diate 15b with 5,5′-dibromo-2,2′-bipyridine. Compared to
the earlier synthesis of 16, the use of substoichiometric
amounts of the alkyne reactant and the employment of
With these convenient experimental conditions in
hand, it was possible to construct the multitopic ligands
as sketched in Scheme 3. Here, the molecules are syn-
thesized outwardly from the dipropargylic/didodecyl-
oxybenzene derivative 11 (insert II). The pivotal building
blocks, bearing either a monoprotected alkyne function
12 or two terminal alkyne functions 13, have been
prepared previously and exploited for the synthesis of
soluble bisterpyridine ligands displaying an increasing
number of ethynylene/phenylene modules as spacers.18
The ditopic ligand 14 was readily prepared in a one-step
procedure from 5-bromo-2,2′-bipyridine, and derivative
13 was obtained from a double cross-coupling reaction
catalyzed by a palladium(0) precursor in n-propylamine
as the solvent. Synthesis of the analogous tritopic ligand
16 can be isolated from a similar process but requires
three steps: (i) coupling of the bipy frame with the
monoprotected alkyne derivative 12; (ii) deprotection with
excess NaOH; and (iii) double cross-coupling between
derivative 15b and 5,5′-dibromo-2,2′-bipyridine. During
this last step, monografting of one bipy/phenyl/ethynyl

7818 J . Org. Chem., Vol. 65, No. 23, 2000
Khatyr and Ziessel
Sch em e 3a
a
Key: (i) nPrNH2, [Pd0(PPh3)4] (6 mol %), 70 °C; (ii) NaOH (excess), benzene, 80 °C.
dilute solutions is clearly in favor of the monosubstituted
derivative (76% isolated yield). The parasitic double-
coupling reaction, leading to the formation of ligand 16,
appears to be inefficient under these conditions (less than
10% isolated yield). The importance of the careful choice
of the experimental conditions for controlling the iterative
synthesis of similar adducts possessing the potential to
undergo further reactivity has been analyzed previous-
ly.32 The first tetratopic ligand (18) was obtained in good
yield by a double cross-coupling reaction of 2 equiv of 17
with the terminal dialkyne derivative 13 (Scheme 4).
Because the iterative synthetic scheme proceeds
smoothly, we attempted the synthesis of a higher homo-
logue of 15b by grafting derivative 12 onto compound 17.
Deprotection under basic conditions leads to 19b. It is of
interest to note that an attempt to prepare compound
19b in a single step by a selective monocoupling reaction
between 17 and 13 failed for reasons inherent to the
reactivity of the terminal alkyne function in derivative
19b. This observation might be a general finding because
15b could not be prepared from the reaction between
intermediate 13 and 5-bromo-2,2′-bipyridine. Finally, the
pentatopic ligand could be prepared in good yield by a
double cross-coupling reaction between a slight excess of
19b and 5,5′-dibromo-2,2′-bipyridine (Scheme 4). Again,
a monosubstituted intermediate (a 5-bromo-substituted
analogue of 16) has been clearly identified. This is a clear
indication for the construction of larger scaffolds.
With the exception of the first set of ligands shown in
Scheme 1, all other ligands and intermediates are soluble
in chlorinated solvents and are isolated as pale-yellow
to deep-yellow powders. All ligands appeared to be
thermally and photochemically stable in air. Character-
ization has been made by NMR, FAB+-MS, UV-vis and
steady-state fluorescence spectroscopy, FT-IR, and el-
emental analysis. All of the spectroscopic data are in
accord with the proposed molecular structures. In par-
(30) Eastmond, R.; J ohnson, T. R.; Walton, D. R. M. J . Organomet.
Chem. 1973, 50, 87.
(31) Heck, R. F. Org. React. 1981, 27, 345. Weijin, T.; Nesbitt, S.;
Heck, R. F. J . Org. Chem. 1990, 55, 63. Cassar, J . J . Organomet. Chem.
1975, 93, 253. Dieck, H. A.; Heck, F. R. J . Organomet. Chem. 1975,
93, 259. Amatore, C.; J utand, A.; Khalil, F.; M’Barki, M. A.; Mottier,
L. Organometallics 1993, 12, 3168. Amatore, C.; J utand, A.; Suarez,
A. J . Am. Chem. Soc. 1993, 115, 9531.
(32) J ones, L., II; Schumm, J . S.; Tour, J . M. J . Org. Chem. 1997,
62, 1388. Huang, S.; Tour, J . M. Tetrahedron Lett. 1999, 40, 3347.
Pearson, D. L.; Tour, J . M. J . Org. Chem. 1997, 62, 1376. Huang, S.;
Tour, J . M. J . Am. Chem. Soc. 1999, 121, 4908.
1
ticular, the H and 13C NMR spectra of the majority of
the compounds presented here were free from overlap-
ping resonances and exhibited the expected number of
patterns. The 13C NMR spectra are useful with respect
to identification of the final structures. The resonances
of the ethynylene sp carbon are readily identified as
singlets in the range of 92.3-83.9 ppm and can be used

Synthesis of Polytopic Ligands
J . Org. Chem., Vol. 65, No. 23, 2000 7819
Sch em e 4a
a
Key: (i) nPrNH2, [Pd0(PPh3)4] (6 mol %), 70 °C; (ii) NaOH (excess), benzene, 80 °C.
to monitor the number of triple bonds. These chemical
shifts are in good agreement with those reported for other
ethynylated compounds.33 Increasing the number of bipy
subunits resulted in the expected increase in the number
of ethynylene carbon signals. There is significant shield-
ing of these peaks with an increase in the size of the
molecule. While the chemical shift of the sp carbon
belonging to the monosubstituted bipy units (located at
the terminal of the molecules) remains almost unchanged
in ligands 16, 18, and 20 and resonates at ca. 92 ppm,
the sp carbon belonging to the disubstituted bipy units
(located at the center of the molecules) shifts progres-
sively from ca. 88 ppm in ligand 16 to 84 ppm in 20. This
upfield shift is in keeping with the inductive electron-
donating influence of the didodecyloxyphenyl moieties.
For each ligand, the stretching vibrational mode of the
ethynylene connecting unit could be resolved at about
2200 cm-1 in the solid-state IR spectrum and lies in the
range expected for such compounds.34
The UV-vis absorption spectra of the mono- to penta-
bipy ligands all display a pair of intense and well-resolved
peaks, one lying at ca. 330 nm and the second in the
(33) Austin, W. B.; Bilow, N.; Kelleghan, W. J .; Lau, K. S. Y. J . Org.
Chem. 1981, 46, 2280.
(34) Grubbs, R. H.; Kratz, D. Chem. Ber. 1993, 126, 149. Schermann,
G.; Gro¨sser, T.; Hampel, F.; Hirsch, A. Chem. Eur. J . 1997, 3, 1105.

7820 J . Org. Chem., Vol. 65, No. 23, 2000
Khatyr and Ziessel
F igu r e 1. UV-vis absorption spectra measured in dichloro-
methane (2 × 10-5 M) at room temperature for various
multitopic ligands.
range of 350-420 nm. Both transitions can be assigned
to π-π* bands originating from the phenyl and pyridyl
rings as well as from the ethynylene fragments (Figure
1). The lowest energy absorption transition is shifted
progressively toward lower energy and appears more
intense as the number of bipy/phenyl/ethynyl units
increases. For instance, ligand 20 with a total of 100
conjugated π electrons exhibits the most red-shifted
absorption maximum. The shift of λ drops from an initial
step of ∆λabs ) 12 ( 2 nm (for ligand 14 f 16) to ∆λabs
)
F igu r e 2. Normalized fluorescence emission spectra mea-
sured in degassed dichloromethane (ca. 1.2 × 10-6 M) at room
temperature: (a) ligands 9, 10, and 14 with excitation wave-
lengths at 350, 360, and 392 nm, respectively; (b) ligands 14,
16, 18, and 20 with excitation wavelength at 392 nm.
7 ( 2 nm (for ligand 16 f 18) and finally to ∆λabs ) 5 (
2 nm (for ligand 18 f 20). This attenuation is in keeping
with limited electronic delocalization along the different
parts of the molecule. Similar trends have recently been
found in metal-capped wirelike polyynediyl chains.35
Furthermore, it is worth pointing out that grafting an
additional ethynyldidocyloxyphenyl group to a single bipy
generates a red shift of ∆λabs ) 17 ( 2 nm for ligand 10
compared to ligand 9, where the number of π electrons
increases from 20 to 28. However, bridging two bipy’s by
a single diethynyldidocyloxyphenyl frame generates a
bigger shift of the absorption band, with ∆λabs ) 25 ( 2
nm for ligand 14 (bearing 34 π electrons) compared to
ligand 9 (with 20 π electrons). The larger shift observed
in the presence of two bipy units was assigned to the
electron-withdrawing influence of the bipy moieties,
which significantly decreases the energy level of the
LUMO orbital of the spacing unit. The fact that neither
the shape nor the position of these relatively narrow
absorption bands changes significantly with increasing
polarity of the solvent excludes the existence of charge-
transfer absorption bands. Hence, this kind of transition
is also present when nonsegmented ethynyldidocylox-
yphenyl frameworks are used as spacers in back-to-back
terpyridine ligands (Figure 2).36
quite high and sensitive to the molecular size (Table 1).
The highest value (φ ≈ 31%) is found for ligand 20 which
has also the highest oscillator strength for the corre-
sponding absorption transition. More importantly, the
fluorescence spectrum shows excellent mirror symmetry
with the lowest energy absorption transition, and in fact,
this is confirmed by an excitation spectra carried out
under similar experimental conditions. On this basis, we
assign the absorption and fluorescence peaks to allowed
π-π* transitions. The apparent Stokes’ shift, with values
ranging from ca. 90 nm for the shorter molecules to 44
nm for the longest one, is rather large. The presence of
a triplet excited state is excluded by the fact that no
change in the steady-state emission was observed when
the emission spectra of ligand 16 were carried out with
an oxygen-degassed solution in dichloromethane at room
temperature.37 Consequently, the lowest energy singlet
state S0 f S1 is responsible for the intense fluorescence
emission band.
Con clu sion
Parallel behavior is seen by steady-state fluorescence
spectrophotometry, where the intense peak of the fluo-
rescence band is shifted progressively toward lower
energy upon increasing the length of the molecule. Again,
the relative shift in the emission maximum tends toward
a plateau for the larger molecules with ∆λem ) 11 ( 2
nm (for ligand 14 f 16), ∆λem ) 4 ( 2 nm (for ligand 16
f 18), and ∆λem ) 3 ( 2 nm (for ligand 18 f 20). It is
also noteworthy that the fluorescence quantum yields are
The present work describes a logical and convenient
synthetic protocol for the construction of quasi-linear
polybipyridine ligands. Each chelating frame is connected
by either a single ethynylene or diethynylenedidocyloxy-
phenyl bridge. Sequential deprotection-coupling steps
have allowed the isolation of a series of soluble and rigid
bipy-based ligands. The key intermediates carry a reac-
(37) Kaiwar, S. P.; Vodacek, A.; Blough, N. V.; Pilato, R. S. J . Am.
Chem. Soc. 1997, 119, 3311. Pilato, R. S.; Van Houten, K. A. In
Multimetallic and Macromolecular Inorganic Photochemistry; Rama-
murthy, V., Schanze, K. S., Eds.; Marcel Dekker: New York, 1999;
Vol. 4, pp 185-214.
(35) Dembinski, R.; Bartik, T.; Bartik, B.; J aeger, M.; Gladysz, J .
A. J . Am. Chem. Soc. 2000, 122, 810.
(36) Khatyr, A.; Ziessel, R. J . Org. Chem. 2000, 65, 3126.

Synthesis of Polytopic Ligands
J . Org. Chem., Vol. 65, No. 23, 2000 7821
Ta ble 1. Sp ectr oscop ic Da ta for th e P olytop ic Liga n d s
ligands
13C δCtC (ppm)a
λabs (nm)b
λem (nm)c
φ (nm)d
9
10
14
16
18
20
90.2; 90.5
90.3; 90.7
92.2; 92.1
92.2; 90.5; 90.2; 88.2
92.3; 92.2; 92.1; 90.5; 90.2; 89.8
92.2; 92.1; 90.6; 90.5; 87.4; 87.3; 83.9
316 (13 600); 347 (10 700)
324 (13 500); 364 (16 300)
331 (13 000); 389 (13 700)
331 (13 300); 401 (22 000)
335 (19 800); 408 (36 900)
334 (23 900); 413 (39 900)
436
446
439
450
454
457
6.5
10.1
7.5
19.4
29.2
31.2
a
b
Measured in CDCl3. Argon-degassed CH2Cl2 at room temperature; same results obtained in air. c In CH2Cl2, excitation wavelength
at 350 nm for 9, 360 nm for 10, and 392 nm for 14-20; concentration range 3.5-1.9 ×10-6 M. In CH2Cl2, at 350 nm for 9, 360 nm for
d
10, and 392 nm for 14-20.
of Φ ) 0.016.40,41 Fast atom bombardment (FAB, positive mode)
tive bromo function, while all of the phenyl intermediates
are constructed with one or two terminal alkynes. This
option is essential for the tailoring of the larger archi-
tectures. Inversion of these reactive functions on the
mass spectra were obtained using m-nitrobenzyl alcohol (m-
NBA) as the matrix; data are given as m/z, and the nature of
the peak and relative intensity are given in parentheses.
Elemental analyses were obtained from the microanalytical
laboratory of the Institut Charles Sadron and the Institut
building blocks does not provide the target compounds.
The high yields obtained for the synthesis of these
extended ligands underline the versatility of the synthetic
protocol. It is anticipated that this procedure will be
useful for synthesis of larger systems, because no major
decrease of isolated yields has been detected among the
various compounds obtained so far.
Universitaire de Technologie in Strasbourg.
Ma ter ia ls. n-Propylamine, 1-bromododecane, and bromo-
hydroquinone were purchased from ACROS; CuI from Fluka;
and (trimethylsilyl)acetylene from Lancaster. 5-Bromo-2,2′-
bipyridine,42,43 5-ethynyl-2,2′-bipyridine,23 5,5′-dibromo-2,2′-
bipyridine,42,43 1,4-di(2-methyl-3-butyn-2-ol)-2,5-didodecyloxy-
benzene (11),36 1-(2-methyl-3-butyn-2-ol)-4-ethynyl-2,5-didodecyl-
oxybenzene (12),36 1,4-diethynyl-2,5-didodecyloxybenzene (13),36
and [Pd0(PPh3)4]44 were prepared and purified according to
literature procedures. Diisopropylamine and tetrahydrofuran
were dried over suitable reagents and freshly distilled under
argon before use. All reactions were carried out under dry
argon by using Schlenk tube techniques. Compound 1 obtained
here as a side product has identical spectroscopic data as the
sample previously prepared.23
Gen er a l P r oced u r es for th e P r ep a r a tion of th e Ar yl-
acetylen e, Bipyr idin e Der ivatives, an d P olytopic Ligan ds.
Con d ition 1. A Schlenk flask equipped with a septum, a
Teflon-coated magnetic stirring bar, and an argon inlet was
charged with the ethynyl and bromo-2,2′-bipyridine derivatives
in argon degassed benzene, and then [Pd0(PPh3)4] (6 mol %)
was added as a solid, followed by argon-degassed diisopropy-
lamine. The solution was heated at 80 °C. After complete
consumption of the starting material (determined by TLC), the
solvent was evaporated, and the crude product was washed
successively by centrifugation with water, methanol, and
finally dichloromethane.
The ligands bearing one to five chelating centers are
of nanometric dimensions and lie within the range of 21-
72 Å, taking into account the edge-to-edge distance
between the two external pyridine rings. Spectrophoto-
metric studies have revealed that, by increasing the
number of π electrons from 20 to 100, a significant
bathochromic shift occurs for absorption and emission
maxima. This effect is attenuated upon increasing the
number of chelating sites. All ligands fluoresce strongly
in solution at room temperature when excited in the less-
energetic absorption band, with the fluorescence quan-
tum yield increasing with increased molecular length.
The chemical stability and photostability of these rigid-
rod platforms makes them attractive for the engineering
of luminophoric d8-transition-metal centers, where each
metallic dot might act as a relay station in photon-
shuttling processes. The whole array might be expected
to operate as an artificial photon-harvesting system.38,39
The didodecyl fragments ability to markedly increase
solubility is an additional tool for micromanipulation,
such as supramolecular organization into mesophases,
grafting of supplementary complexation sites in order to
build 2D complexes, and modulation of the bridge ener-
getics by incorporating donor/acceptor templates.
Con d ition 2. A Schlenk flask was charged with bromo-2,2′-
bipyridine derivatives in argon-degassed tetrahydrofuran, and
(trimethylsilyl)acetylene, [Pd(PPh3)2Cl2] (6 mol %), CuI (10 mol
%), and finally argon-degassed diisopropylamine were succes-
sively added. The solution was stirred at room temperature.
After complete consumption of the starting material, the
solvent was evaporated under vacuum, and the product was
purified by chromatography on alumina using hexane with a
gradient of dichloromethane.
Exp er im en ta l Section
Con d ition 3. A Schlenk flask was charged with the bromo-
2,2′-bipyridine and ethynylbenzene derivatives in argon-de-
gassed n-propylamine, and [Pd0(PPh3)4] (6 mol %) was added
as a solid. After heating at 70 °C and complete consumption
of the starting material, the solvent was removed under
vacuum, and the residue was purified by chromatography on
alumina, using dichloromethane with a gradient of methanol.
Con d ition 4a . To a stirred solution of the trimethylsilyl-
protected compound in methanol was added as a solid K2CO3
(2 equiv). After complete consumption of the starting material,
the reaction was quenched with water. The solution was
concentrated by rotary evaporation, and the organic product
was extracted with dichloromethane. The organic layers were
evaporated to dryness under vacuum, and the residue was
Gen er a l Meth od s. The 200.1 MHz 1H and 50.3 MHz 13C
NMR spectra were recorded at room temperature, unless
otherwise specified, using perdeuterated solvent as an internal
standard: δ (H) in ppm relative to residual protiated solvent
in CDCl3 (7.26); δ (C) in ppm relative to the solvent in CDCl3
(77.0); all carbon signals were detected as singlets. Melting
points were obtained on a Bu¨chi 535 capillary melting point
apparatus in open-ended capillaries and are uncorrected. FT-
IR spectra were measured in KBr pellets. UV-vis spectra were
measured in CH2Cl2 at room temperature. Luminescence
experiments were performed in dilute (ca. 2 × 10-6 M)
degassed dichloromethane solutions at room temperature.
Luminescence maxima reported are uncorrected for photo-
multiplier reponse. Luminescence quantum yields were mea-
sured following the opical dilution method, with [Ru(bipy)3]2+
in degassed acetonitrile as the standard with a quantum yield
(40) Demas, J . N.; Crosby, G. A. J . Phys. Chem. 1971, 75, 991.
(41) Nakamaru, K. Bull. Chem. Soc. J pn. 1982, 55, 2697.
(42) Morgan, G.; Burstall, F. H. J . Chem. Soc. 1937, 1649.
(43) Romero, F. M.; Ziessel, R. Tetrahedron Lett. 1995, 36, 6471.
(44) Coulson, D. R. Inorg. Synth. 1972, 13, 121.
(38) Weber, S. E. Chem. Rev. 1990, 90, 1469.
(39) Fox, M. A. Acc. Chem. Res. 1992, 25, 569.

7822 J . Org. Chem., Vol. 65, No. 23, 2000
Khatyr and Ziessel
purified by chromatography on alumina, using dichloromethane
with a gradient of methanol.
3.20 mL (13.22 mmol) of 1-bromododecane was added to a
suspension of bromohydroquinone (1.250 g, 6.61 mmol) and
NaOH (0.661 g, 16.53 mmol) in DMF (10 mL). After we heated
the solution at 100 °C for 16 h, it was cooled to room
temperature, and then 50 mL of water was added and the
product was extracted with dichloromethane (3 × 50 mL). The
solvent was evaporated under vacuum, and the residue was
washed with ethanol, affording 3.050 g of 6 (88%): mp 43-4
°C; 1H NMR (CDCl3) δ 0.90 (t, J ) 6.1 Hz, CH3, 6H), 1.28 (m,
CH2, 36H), 1.77 (m, CH2, 4H), 3.88 (t, J ) 6.6 Hz, OCH2, 2H),
3.95 (t, J ) 6.9 Hz, OCH2, 2H), 6.76 (m, Ph, 2H), 7.11 (d, J )
2.2 Hz, Ph, 1H); 13C{1H} NMR (CDCl3) δ 14.2, 22.8, 26.1, 29.4,
29.5, 29.7, 32.1, 68.9, 70.3, 112.9, 114.4, 114.7, 119.6, 149.9,
153.7; FT-IR (KBr, cm-1) 2922 (s), 2848 (s), 1500 (s), 1466 (s),
1396 (s), 1271 (s), 1219 (s), 1132 (w), 1046 (s), 1002 (m), 888
(m); UV-vis (CH2Cl2) λ, nm (ꢀ, M-1 cm-1) 296 (3400); FAB+
527 ([M + H]+, 100), 525 ([M + H]+, 96), 445 ([M - Br]+, 15).
Anal. Calcd for C30H53O2Br: C, 68.55; H, 10.16. Found: C,
68.17; H, 9.89.
Con d ition 4b. To a stirred solution of the propargylic-pro-
tected compounds in benzene was added an excess of NaOH,
and the mixture was heated at 80 °C. After consumption of
the starting material, the reaction was quenched with an aque-
ous NH4Cl-saturated solution. The organic products were
extracted with dichloromethane, and the organic layers were
dried with MgSO4. The solvent was then removed under vacu-
um, and the compound was purified by chromatography on
alumina, using dichloromethane with a gradient of methanol.
Syn th esis of th e Bu ild in g Block s. 5-(2,2′-Bip yr id in -5-
yleth yn yl)-5′-br om o-2,2′-bip yr id in e (2). The compound was
prepared according to experimental condition 1, from 0.107 g
(0.59 mmol) of 5-ethynyl-2,2′-bipyridine, 10 mL of benzene,
0.280 g (0.89 mmol) of 5,5′-dibromo-2,2′-bipyridine, 0.041 g
(0.035 mmol) of [Pd0(PPh3)4], and 3 mL of diisopropylamine.
The reaction mixture was heated for 27 h at 80 °C. Purification
was performed by chromatography on alumina with hexane/
CH2Cl2 (0-50%) as eluant and afforded 0.180 g of 2 (74%):
1-(2-Meth yl-3-bu tyn -2-ol)-2,5-d id od ecyloxyben zen e (7).
The compound was prepared according to experimental condi-
tion 3, from 1.000 g (1.90 mmol) of 6, 35 mL of n-propylamine,
0.184 mL (1.90 mmol) of 2-methyl-3-butyn-2-ol, and 0.132 g
(0.15 mmol) of [Pd(PPh3)4]. The reaction mixture was heated
for 22 h at 70 °C. Purification was performed by flash
chromatography on silica gel with CH2Cl2/CH3OH (0-2%) as
1
mp 237-8 °C; H NMR (CDCl3) δ 7.34 (dd, J ) 4.8 Hz, J )
1.2 Hz, 1H), 7.84 (td, J ) 7.8 Hz, J ) 1.6 Hz, 1H), 7.97 (m,
3H), 8.40 (m, 4H), 8.70 (dd, J ) 4.7 Hz, J ) 0.9 Hz, 1H), 8.74
(d, J ) 2.4 Hz, 1H), 8.82 (dd, J ) 4.0 Hz, J ) 0.6 Hz, 1H), 8.85
(d, J ) 4.0 Hz, 1H); 13C NMR (CDCl3) δ 90.4 (CtC), 90.8 (Ct
C), 119.7, 120.1, 120.4, 120.5, 121.5, 121.6, 122.8, 124.2, 128.5,
128.7, 132.1, 132.3, 133.8, 137.1, 139.6, 149.4, 150.4, 151.8,
154.2, 155.4; FT-IR (KBr, cm-1) 3421 (s), 2926 (s), 2191 (w,
1
the eluant and afforded 0.894 g of 7 (89%): mp 55-6 °C; H
NMR (CDCl3) δ 0.88 (t, J ) 6.2 Hz, CH3, 6H), 1.27 (m, CH2,
36H), 1.62 (s, CH3, 6H), 1.76 (m, CH2, 4H), 2.50 (s, OH, 1H),
3.87 (t, J ) 6.7 Hz, OCH2, 2H), 3.94 (t, J ) 6.6 Hz, OCH2,
2H), 6.78 (m, Ph, 2H), 6.91 (d, J ) 1.9 Hz, Ph, 1H); 13C{1H}
NMR (CDCl3) δ 14.2, 22.8, 26.1, 29.4, 29.5, 29.6, 29.7, 31.6,
32.0, 65.7, 68.7, 69.7, 78.7 (CtC), 97.8 (CtC), 113.1, 114.0,
116.5, 118.5, 152.8, 154.1; FT-IR (KBr, cm-1) 3516 (s), 3396
(s), 2919 (s), 2851 (s), 2015 (w, νCtC), 1602 (w), 1504 (s), 1469
(s), 1393 (m), 1274 (s), 1224 (s), 1159 (m), 1041 (s); UV-vis
(CH2Cl2) λ, nm (ꢀ, M-1 cm-1) 315 (6400); FAB+ 529 ([M + H]+,
100), 469 ([M - C(CH3)2OH]+, 10). Anal. Calcd for C35H60O3:
C, 79.49; H, 11.44. Found: C, 79.22; H, 11.27.
ν
CtC), 1654 (m), 1437 (m), 1388 (m), 1261 (s), 1091 (s), 1047
(s), 880 (m); UV-vis (CH2Cl2) λ, nm (ꢀ, M-1 cm-1) 273 (1600),
337 (7400), 356 (5800); FAB+ 415 ([M + H]+, 100), 413 ([M +
H]+, 90). Anal. Calcd for C22H13N4Br: C, 63.94; H, 3.17; N,
13.56. Found: C, 63.89; H, 3.12; N, 13.54.
5-(2,2′-Bipyr idin -5-yleth yn yl)-5′-(tr im eth ylsilyleth yn yl)-
2,2′-bip yr id in e (3a ). The compound was prepared according
to experimental condition 2, from 0.280 g (0.68 mmol) of 2, 20
mL of THF, 0.116 mL (0.81 mmol) of (trimethylsilyl)acetylene,
0.028 g (0.04 mmol) of [Pd(PPh3)2Cl2], 0.002 g (0.07 mmol) of
CuI, and 5 mL of diisopropylamine. The reaction mixture was
stirred at room temperature for 4 days. Purification was
performed by chromatography on alumina with hexane/CH2-
Cl2 (50-100%) as the eluant and afforded 0.175 g of 3a (60%):
1-Eth yn yl-2,5-d id od ecyloxyben zen e (8). The compound
was prepared according to experimental condition 4b, from
0.600 g (1.13 mmol) of 7, 1.000 g (25 mmol) of NaOH (excess),
and 30 mL of benzene. The reaction mixture was heated for
20 h at 80 °C. Purification was performed by flash chroma-
tography on silica gel with hexane/CH2Cl2 (60-100%) as the
eluant and afforded 0.450 g of 8 (84%): mp 41-2 °C; 1H NMR
(CDCl3) δ 0.89 (t, J ) 6.1 Hz, CH3, 6H), 1.28 (m, CH2, 36H),
1.80 (m, CH2, 4H), 3.24 (s, CtCH, 1H), 3.88 (t, J ) 6.5 Hz,
OCH2, 2H), 3.97 (t, J ) 6.6 Hz, OCH2, 2H), 6.82 (m, Ph, 2H),
6.99 (d, J ) 2.4 Hz, Ph, 1H); 13C{1H} NMR (CDCl3) δ 14.2,
22.8, 26.1, 29.3, 29.4, 29.5, 29.7, 29.8, 32.1, 68.7, 69.8, 80.3
(CtC), 80.9 (CtC), 112.5, 114.0, 117.0, 119.4, 152.8, 154.7;
FT-IR (KBr, cm-1) 3296 (m), 2921 (s), 2850 (s), 2064 (w, νCtC),
1502 (s), 1470 (s), 1396 (m), 1302 (m), 1272 (s), 1229 (s), 1163
(w), 1033 (s), 1004 (w), 801 (s); UV-vis (CH2Cl2) λ, nm (ꢀ, M-1
cm-1) 316 (5200); FAB+ 471 ([M + H]+, 100), 289 ([M -
OC12H25]+, 10). Anal. Calcd for C32H54O2: C, 81.64; H, 11.56.
Found: C, 81.43; H, 11.21.
1-(2-Meth yl-3-bu tyn -2-ol)-4-(2,2′-bipyr idin -5-yleth yn yl)-
2,5-d id od ecyloxyben zen e (15a ). The compound was pre-
pared according to experimental condition 3, from 0.026 g (0.09
mmol) of 5-bromo-2,2′-bipyridine, 16 mL of n-propylamine,
0.050 g (0.09 mmol) of 12, and 0.006 g (0,005 mmol) of [Pd-
(PPh3)4]. The reaction mixture was heated for 2 days at 70
°C. Purification was performed by chromatography on alumina
with CH2Cl2/CH3OH (0-1%) as the eluant and afforded 0.058
g of 15a (91%): mp 81-2 °C; 1H NMR (CDCl3) δ 0.85 (m, CH3,
6H), 1.25 (m, CH2, 36H), 1.56 (s, CH3, 6H), 1.80 (m, CH2, 4H),
2.38 (s, OH, 1H), 3.98 (m, OCH2, 4H), 6.91 (s, Ph, 1H), 6.97 (s,
Ph, 1H), 7.32 (t, J ) 6.2 Hz, 1H), 7.82 (td, J ) 7.8 Hz, J ) 1.6
Hz, 1H), 7.89 (dd, J ) 8.3 Hz, J ) 1.9 Hz, 1H), 8.42 (d, J ) 8.1
Hz, 2H), 8.68 (d, J ) 4.6 Hz, 1H), 8.81 (s, 1H); 13C NMR
(CDCl3) δ 14.2, 22.8, 26.1, 29.4, 29.7, 31.5, 32.0, 65.8, 69.6,
69.7, 78.5 (CtC), 90.2 (CtC), 91.6 (CtC), 99.7 (CtC), 113.2,
114.1, 116.8, 117.1, 120.4, 120.6, 121.4, 124.0, 137.0, 139.3,
1
mp 212-3 °C; H NMR (CDCl3) δ 0.28 (s, CH3, 9H), 7.32 (dd,
J ) 4.8 Hz, J ) 1.1 Hz, 1H), 7.84 (m, 2H), 7.94 (t, J ) 1.9 Hz,
1H), 7.98 (t, J ) 1.9 Hz, 1H), 8.41 (m, 4H), 8.70 (d, J ) 4.8
Hz, 1H), 8.73 (d, J ) 1.4 Hz, 1H), 8.84 (m, 2H); 13C NMR
(CDCl3) δ -0.1 (TMS), 90.5 (CtC), 90.8 (CtC), 99.7 (CtC),
101.8 (CtC), 119.7, 119.9, 120.5, 120.6, 120.8, 121.5, 124.1,
137.1, 139.6, 139.9, 149.4, 151.8, 152.2, 154.2, 154.6, 155.4;
FT-IR (KBr, cm-1) 3416 (s), 2962 (m), 2158 (m, νCtC), 1586
(m), 1456 (s), 1366 (m), 1250 (s), 1122 (s), 842 (s); UV-vis (CH2-
Cl2) λ, nm (ꢀ, M-1 cm-1) 275 (2000), 345 (8500), 364 (8000);
FAB+ 431 ([M + H]+, 100), 416 ([M - CH3 + H]+, 30), 415 ([M
- CH3]+, 90). Anal. Calcd for C27H22N4Si: C, 75.32; H, 5.15;
N, 13.01. Found: C, 75.27; H, 5.08; N, 12.96.
5 -(2,2′-Bip yr id in -5 -yleth yn yl) -5′-eth yn yl -2,2′-bip yr i-
d in e (3b). The compound was prepared according to experi-
mental condition 4a, from 0.108 g (0.25 mmol) of 3a , 0.069 g
(0.50 mmol) of K2CO3, and 20 mL of methanol. The solution
was stirred at room temperature for 14 h. Purification was
performed by chromatography on alumina with CH2Cl2/CH3-
OH (0-2%) as the eluant and afforded 0.080 g of 3b (89%):
mp >250 °C; 1H NMR (CDCl3) δ 3.32 (s, CtCH, 1H), 7.34 (dd,
J ) 4.8 Hz, J ) 1.2 Hz, 1H), 7.90 (m, 4H), 8.44 (m, 5H), 8.71
(m, 1H), 8.78 (m, 1H), 8.85 (m, 2H); 13C NMR (CDCl3) δ 80.7
(CtC), 81.8 (CtC), 90.4 (CtC), 90.9 (CtC), 119.5, 119.6,
120.1, 120.5, 120.7, 120.8, 121.5, 124.2, 137.1, 139.9, 140.1,
149.4, 151.7, 151.8, 152.4, 154.5, 154.6, 155.4; FT-IR (KBr,
cm-1) 3460 (s), 2923 (m), 2195 (w, νCtC), 1601 (m), 1460 (s),
1313 (m), 1243 (m), 1109 (s), 841 (s); UV-vis (CH2Cl2) λ, nm
(ꢀ, M-1 cm-1) 269 (1600), 341 (11 200), 361 (9200); FAB+ 359
([M + H]+, 100). Anal. Calcd for C24H14N4: C, 80.43; H, 3.94;
N, 15.63. Found: C, 80.24; H, 3.81; N, 15.56.
1-Br om o-2,5-d id od ecyloxyben zen e (6). In a 50 mL flask
equipped with a reflux condenser and a magnetic stirring bar,

Synthesis of Polytopic Ligands
J . Org. Chem., Vol. 65, No. 23, 2000 7823
149.4, 151.7, 153.7, 153.8, 154.8, 155.6; FT-IR (KBr, cm-1) 3437
(w), 2921 (s), 2851 (s), 2211 (w, νCtC), 1541 (w), 1503 (s), 1463
(s), 1413 (m), 1386 (m), 1276 (m), 1218 (s), 1156 (m), 1025 (w),
985 (w), 860 (m); UV-vis (CH2Cl2) λ, nm (ꢀ, M-1 cm-1) 261
(6300), 305 (12 500), 316 (13 300), 325 (15 100), 367 (14 700);
FAB+ 707 ([M + H]+, 100), 521 ([M - OC12H25]+, 10). Anal.
Calcd for C47H66N2O3: C, 79.84; H, 9.41; N, 3.96. Found: C,
79.65; H, 9.19; N, 3.84.
151.6, 153.7, 153.9, 155.7; FT-IR (KBr, cm-1) 3401 (w), 3284
(w), 3058 (w), 2922 (s), 2854 (s), 2211 (w, νCtC), 1502 (m), 1463
(s), 1420 (m), 1376 (m), 1276 (m), 1217 (s), 1158 (m), 1126 (s),
1060 (m), 1030 (m), 854 (m); UV-vis (CH2Cl2) λ, nm (ꢀ, M-1
cm-1) 261 (4400), 276 (6400), 295 (7700), 336 (12 200), 397
(20 600); FAB+ 1353 ([M + H]+, 100), 1167 ([M - OC12H25]+,
30), 1108 ([M - OC12H25 - C(CH3)2OH]+, 10). Anal. Calcd for
C
91H124N4O5: C, 80.72; H, 9.23; N, 4.14. Found: C, 80.59; H,
1-(2,2′-Bip yr id in -5-yleth yn yl)-4-eth yn yl-2,5-d id od ecyl-
oxyben zen e (15b). The compound was prepared according
to experimental condition 4b, from 0.045 g (0.063 mmol) of 15a ,
0.100 g (2.50 mmol) of NaOH (excess), and 20 mL of benzene.
The reaction mixture was heated for 14 h at 80 °C. Purification
was performed by chromatography on alumina with hexane/
CH2Cl2 (50-100%) as the eluant and afforded 0.036 g of 15b
8.91; N, 3.99.
1-[1-(2,2′-Bip yr id in -5-yleth yn yl)-4-(2,2′-bip yr id in -5,5′-
yld ieth yn yl)-2,5-d id od ecyloxyben zen e]-4-eth yn yl-2,5-d i-
d od ecyloxyben zen e (19b). The compound was prepared
according to experimental condition 4b, from 0.030 g (0.022
mmol) of 19a , 0.080 g (2.00 mmol) of NaOH (excess), and 20
mL of benzene. The reaction mixture was heated for 2 days at
80 °C. Purification was performed by chromatography on
alumina with CH2Cl2 as the eluant and afforded 0.024 g of
1
(87%): mp 59-60 °C; H NMR (CDCl3) δ 0.87 (m, CH3, 6H),
1.26 (m, CH2, 36H), 1.83 (m, CH2, 4H), 3.36 (s, CtCH, 1H),
4.00 (m, OCH2, 4H), 6.99 (s, Ph, 1H), 7.01 (s, Ph, 1H), 7.32 (t,
J ) 6.2 Hz, 1H), 7.82 (td, J ) 7.8 Hz, J ) 1.6 Hz, 1H), 7.90
(dd, J ) 8.3 Hz, J ) 1.9 Hz, 1H), 8.42 (d, J ) 8.1 Hz, 2H), 8.68
(d, J ) 4.6 Hz, 1H), 8.81 (s, 1H); 13C NMR (CDCl3) δ 14.2,
22.8, 26.0, 26.1, 29.2, 29.3, 29.4, 29.7, 32.0, 69.8, 80.0 (CtC),
82.7 (CtC), 90.0 (CtC), 91.9 (CtC), 113.4, 113.9, 117.0, 117.8,
120.4, 120.5, 121.4, 124.0, 137.0, 139.3, 149.4, 151.7, 153.7,
154.2, 154.9, 155.6; FT-IR (KBr, cm-1) 3417 (m), 3289 (m), 2914
(s), 2850 (s), 2361 (w), 2336 (w), 2208 (w, νCtC), 1616 (w), 1503
(s), 1469 (s), 1411 (w), 1391 (s), 1277 (m), 1218 (s), 1029 (s),
860 (w); UV-vis (CH2Cl2) λ, nm (ꢀ, M-1 cm-1) 307 (16 700),
316 (18 100), 325 (20 000), 365 (17 700); FAB+ 649 ([M + H]+,
100), 463 ([M - OC12H25]+, 10). Anal. Calcd for C44H60N2O2:
C, 81.43; H, 9.32; N, 4.32. Found: C, 81.35; H, 9.22; N, 4.20.
1-(2,2′-Bipyr idin -5-yleth yn yl)-4-(2,2′-bipyr idin -5-yleth y-
n yl-5′-br om o)-2,5-d id od ecyloxyben zen e (17). The com-
pound was prepared according to experimental condition 3,
from 0.050 g (0.077 mmol) of 15b, 60 mL of n-propylamine,
0.048 g (0.154 mmol) of 5,5′-dibromo-2,2′-bipyridine, and 0.005
g (0.004 mmol) of [Pd(PPh3)4]. The reaction mixture was heated
for 2 days at 70 °C. Purification was performed by chroma-
tography on alumina with CH2Cl2/CH3OH (0-3%) as the
eluant and afforded 0.052 g of 17 (76%): mp 124-5 °C; 1H
NMR (CDCl3) δ 0.85 (m, CH3, 6H), 1.23 (m, CH2, 36H), 1.87
(m, CH2, 4H), 4.06 (t, J ) 6.3 Hz, OCH2, 4H), 7.06 (s, Ph, 2H),
7.31 (td, J ) 7.5 Hz, J ) 5.9 Hz, J ) 1.1 Hz, 1H), 7.82 (td, J
) 7.8 Hz, J ) 1.9 Hz, 1H), 7.89-7.96 (m, 3H), 8.31-8.44 (m,
4H), 8.70 (m, 2H), 8.81 (m, 2H); 13C NMR (CDCl3) δ 14.2, 22.8,
26.2, 29.4, 29.5, 29.7, 29.9, 32.0, 69.7, 90.1 (CtC), 90.5 (Ct
C), 92.0 (CtC), 92.2 (CtC), 113.8, 114.0, 116.9, 120.3, 120.4,
120.5, 120.9, 121.4, 122.6, 124.0, 137.0, 139.3, 139.6, 149.4,
150.4, 151.7, 153.9, 154.1, 154.9, 155.6; FT-IR (KBr, cm-1) 3441
(m), 2922 (s), 2853 (s), 2360 (m), 2209 (w, νCtC), 1501 (m), 1458
(s), 1413 (m), 1420 (m), 1379 (m), 1277 (m), 1217 (s), 1089 (w),
1034 (m), 844 (w); UV-vis (CH2Cl2) λ, nm (ꢀ, M-1 cm-1) 262
(5700), 333 (13 500), 391 (14 300); FAB+ 881 ([M + H]+, 85),
883 ([M + H]+, 100), 801 ([M - Br]+, 30). Anal. Calcd for
1
19b (84%): mp 133-4 °C; H NMR (CDCl3) δ 0.86 (m, CH3,
12H), 1.25 (m, CH2, 72H), 1.85 (m, CH2, 8H), 3.37 (s, CtCH,
1H), 4.03 (m, OCH2, 8H), 7.00 (s, Ph, 1H), 7.02 (s, Ph, 1H),
7.06 (s, Ph, 2H), 7.33 (t, J ) 7.4 Hz, 1H), 7.96-7.80 (m, 4H),
8.44 (m, 4H), 8.70 (d, J ) 5.4 Hz, 1H), 8.82 (s, 3H); 13C NMR
(CDCl3) δ 14.2, 22.8, 23.0, 26.0, 26.2, 29.5, 29.8, 32.0, 69.7,
80.0 (CtC), 90.2 (CtC), 90.3 (CtC), 90.5 (CtC), 90.6 (CtC),
92.1 (CtC), 92.2 (CtC), 92.3 (CtC), 113.4, 113.9, 116.9, 117.8,
120.7, 121.4, 124.1, 127.1, 128.8, 128.9, 131.0, 137.1, 139.3,
151.8, 153.7, 153.9, 154.2; FT-IR (KBr, cm-1) 3418 (m), 3290
(m), 2916 (s), 2852 (s), 2363 (w), 2209 (m, νCtC), 1618 (m), 1505
(s), 1470 (s), 1393 (s), 1280 (m), 1220 (s), 1031 (s), 860 (m);
UV-vis (CH2Cl2) λ, nm (ꢀ, M-1 cm-1) 274 (13 400), 306
(15 200), 335 (20 300), 396 (29 600); FAB+ 1296 ([M + H]+,
100), 1109 ([M - OC12H25]+, 10). Anal. Calcd for C88H118N4O4:
C, 81.56; H, 9.18; N, 4.32. Found: C, 81.38; H, 9.02; N, 4.19.
Syn th esis of P olytop ic Liga n d s. Liga n d 4. This ligand
was prepared according to experimental condition 1, from
0.058 g (0.14 mmol) of 2, 25 mL of benzene, 0.050 g (0.14 mmol)
of 3b, 0.010 g (0.008 mmol) of [Pd0(PPh3)4], and 3 mL of
diisopropylamine. The reaction mixture was heated for 4 days
at 80 °C. The crude precipitate was filtered and washed
successively by centrifugation with H2O (3 × 10 mL), CH3OH
(3 × 10 mL), and CH2Cl2 (3 × 10 mL) and afforded 0.082 g of
4 (84%): mp >250 °C; FT-IR (KBr, cm-1) 3049 (m), 2977 (m),
2200 (w, νCtC), 1589 (m), 1569 (m), 1542 (m), 1465 (s), 1434
(m), 1368 (m), 1022 (m), 840 (s), 796 (s), 738 (s); FAB+ 691
([M + H]+, 100). Anal. Calcd for C46H26N8: C, 79.98; H, 3.79;
N, 16.22. Found: C, 79.61; H, 3.72; N, 15.86.
Liga n d 5. This ligand was prepared according to experi-
mental condition 1, from 0.050 g (0.14 mmol) of 3b, 20 mL of
benzene, 0.022 g (0.07 mmol) of 5,5′-dibromo-2,2′-bipyridine,
0.010 g (0.008 mmol) of [Pd0(PPh3)4], and 2.5 mL of diisopro-
pylamine. The reaction mixture was heated for 4 days at 80
°C. The crude precipitate was filtered and washed successively
by centrifugaion with H2O (3 × 10 mL), CH3OH (3 × 10 mL),
and CH2Cl2 (3 × 10 mL) and afforded 0.045 g of 5 (74%): mp
>250 °C; FT-IR (KBr, cm-1) 3050 (m), 2979 (m), 2216 (w, νCt
C), 1590 (m), 1467 (s), 1439 (m), 1375 (m), 1032 (m), 799 (s),
C
54H65N4O2Br: C, 73.53; H, 7.43; N, 6.35. Found: C, 73.29;
H, 7.20; N, 6.17.
1-[1-(2,2′-Bip yr id in -5-yleth yn yl)-4-(2,2′-bip yr id in -5,5′-
yld ieth yn yl)-2,5-d id od ecyloxyben zen e]-4-(2-m eth yl-3-bu -
t yn -2-ol)-2,5-d id od ecyloxyben zen e (19a ). The compound
was prepared according to experimental condition 3, from
0.020 g (0.022 mmol) of 17, 10 mL of n-propylamine, 0.013 g
(0.022 mmol) of 12, and 0.002 g (0,001 mmol) of [Pd(PPh3)4].
The reaction mixture was heated for 2 days at 70 °C. Purifica-
tion was performed by chromatography on alumina with CH2-
Cl2/CH3OH (0-3%) as the eluant and afforded 0.026 g of 19a
(85%): mp 136-7 °C; 1H NMR (CDCl3) δ 0.85 (m, CH3, 12H),
1.25 (m, CH2, 72H), 1.64 (s, CH3, 6H), 1.85 (m, CH2, 8H), 2.33
(s, OH, 1H), 4.07 (m, OCH2, 8H), 6.93 (s, Ph, 1H), 7.00 (s, Ph,
1H), 7.07 (s, Ph, 2H), 7.32 (td, J ) 7.4 Hz, J ) 5.8 Hz, J ) 1.1
Hz, 1H), 7.78-7.96 (m, 4H), 8.42 (m, 4H), 8.69 (d, J ) 4.8 Hz,
1H), 8.82 (s, 3H); 13C NMR (CDCl3) δ 14.2, 22.8, 26.2, 29.4,
29.7, 31.5, 32.0, 65.8, 69.5, 69.7, 78.7 (CtC), 90.2 (CtC), 90.5
(CtC), 91.2 (CtC), 91.6 (CtC), 92.6 (CtC), 92.7 (CtC), 99.7
(CtC), 113.1, 116.9, 117.1, 120.1, 120.4, 120.6, 120.7, 120.8,
128.6, 128.7, 131.9, 132.0, 132.1, 132.3, 133.7, 139.3, 149.4,
742 (s); FAB+ 869 ([M + H]+, 100). Anal. Calcd for C58H32N10
:
C, 80.17; H, 3.71; N, 16.12. Found: C, 79.80; H, 3.49; N, 15.89.
Liga n d 9. This ligand was prepared according to experi-
mental condition 3, from 0.062 g (0.265 mmol) of 5-bromo-2,2′-
bipyridine, 15 mL of n-propylamine, 0.125 g (0.265 mmol) of
8, and 0.018 g (0.016 mmol) of [Pd(PPh3)4]. The reaction
mixture was heated for 2 days at 70 °C. Purification was
performed by flash chromatography on silica gel with CH2Cl2/
CH3OH (0-1%) as the eluant and afforded 0.130 g of 9 (78%):
1
mp 45-6 °C; H NMR (CDCl3) δ 0.88 (m, CH3, 6H), 1.26 (m,
CH2, 36H), 1.79 (m, CH2, 4H), 3.91 (t, J ) 6.3 Hz, OCH2, 2H),
4.00 (t, J ) 6.3 Hz, OCH2, 2H), 6.84 (m, Ph, 2H), 7.05 (d, J )
2.4 Hz, Ph, 1H), 7.29 (m, 1H), 7.80 (td, J ) 7.8 Hz, J ) 1.9
Hz, 1H), 7.93 (dd, J ) 8.1 Hz, J ) 2.2 Hz, 1H), 8.40 (d, J ) 8.3
Hz, 2H), 8.68 (m, 1H), 8.82 (d, J ) 2.2 Hz, 1H); 13C NMR
(CDCl3) δ 14.2, 22.8, 26.1, 26.2, 29.5, 29.8, 32.0, 68.8, 69.8,
90.2 (CtC), 90.5 (CtC), 113.0, 114.0, 117.3, 118.4, 120.4,
120.9, 121.4, 123.9, 137.0, 139.2, 149.3, 151.7, 152.9, 153.9,
154.4, 154.7, 155.7; FT-IR (KBr, cm-1) 3447 (m), 3050 (w), 2919

7824 J . Org. Chem., Vol. 65, No. 23, 2000
Khatyr and Ziessel
(s), 2849 (s), 2210 (w, νCtC), 1588 (m), 1542 (m), 1502 (s), 1468
(s), 1420 (m), 1394 (m), 1279 (s), 1222 (s), 1154 (m), 1032 (s),
854 (m), 792 (s); UV-vis (CH2Cl2) λ, nm (ꢀ, M-1 cm-1) 316
(13 600), 347 (10 700); FAB+ 625 ([M + H]+, 100), 439 ([M -
OC12H25]+, 30). Anal. Calcd for C42H60N2O2: C, 80.72; H, 9.68;
N, 4.48. Found: C, 80.53; H, 9.47; N, 4.38.
ν
CtC), 1640 (m), 1618 (m), 1507 (w), 1460 (m), 1437 (s), 1261
(w), 1222 (w), 1191 (s), 1118 (s), 1068 (m), 1026 (m), 799 (m),
721 (s); UV-vis (CH2Cl2) λ, nm (ꢀ, M-1 cm-1) 261 (8400), 331
(13 300), 401 (22 000); FAB+ 1450 ([M + H]+, 100), 1264 ([M
- OC12H25]+, 15), 1094 ([M - OC12H25 - C12H25]+, 5). Anal.
Calcd for C98H124N6O4: C, 81.17; H, 8.62; N, 5.80. Found: C,
80.83; H, 8.45; N, 5.57.
Liga n d 10. This ligand was prepared according to experi-
mental condition 3, from 0.042 g (0.133 mmol) of 5,5′-dibromo-
2,2′-bipyridine, 15 mL of n-propylamine, 0.125 g (0.265 mmol)
of 8, and 0.018 g (0.016 mmol) of [Pd(PPh3)4]. The reaction
mixture was heated for 2 days at 70 °C. Purification was
performed by flash chromatography on silica gel with CH2Cl2
as the eluant and afforded 0.090 g of 10 (62%): mp 50-1 °C;
1H NMR (CDCl3) δ 0.88 (m, CH3, 12H), 1.27 (m, CH2, 72H),
1.81 (m, CH2, 8H), 3.92 (t, J ) 6.6 Hz, OCH2, 4H), 4.01 (t, J )
6.3 Hz, OCH2, 4H), 6.85 (m, Ph, 4H), 7.05 (d, J ) 2.2 Hz, Ph,
2H), 7.92 (m, 2H), 8.35 (t, J ) 8.2 Hz, 1H), 8.45 (d, J ) 8.3
Hz, 1H), 8.79 (m, 2H); 13C NMR (CDCl3) δ 14.2, 22.8, 26.1,
26.2, 29.4, 29.5, 29.8, 32.0, 68.8, 69.8, 90.3 (CtC), 90.7 (Ct
C), 112.9, 114.0, 117.4, 118.4, 120.3, 139.2, 150.4, 151.8, 152.9,
154.1, 155.4; FT-IR (KBr, cm-1) 2919 (s), 2850 (s), 2360 (m),
2209 (w, νCtC), 1531 (w), 1500 (s), 1468 (s), 1423 (m), 1392
(m), 1279 (m), 1222 (s), 1154 (m), 1029 (s), 839 (m), 785 (m);
UV-vis (CH2Cl2) λ, nm (ꢀ, M-1 cm-1) 324 (13 500), 364
(16 300); FAB+ 1093 ([M + H]+, 100), 907 ([M - OC12H25]+,
10). Anal. Calcd for C74H112N2O4: C, 81.27; H, 10.32; N, 2.56.
Found: C, 81.04; H, 10.18; N, 2.38.
Liga n d 18. This ligand was prepared according to experi-
mental condition 3, from 0.020 g (0.022 mmol) of 17, 10 mL of
n-propylamine, 0.006 g (0.011 mmol) of 13, and 0.002 g (0,001
mmol) of [Pd(PPh3)4]. The reaction mixture was heated for 4
days at 70 °C. Purification was performed by chromatography
on alumina with CH2Cl2/CH3OH (0-5%) as the eluant and
afforded 0.018 g of 18 (76%): mp 162-3 °C; 1H NMR (CDCl3)
δ 0.87 (m, CH3, 18H), 1.24 (m, CH2, 108H), 1.89 (m, CH2, 12H),
4.07 (t, J ) 6.2 Hz, OCH2, 12H), 7.07 (s, Ph, 6H), 7.33 (td, J )
7.5 Hz, J ) 1.9 Hz, 2H), 7.84 (td, J ) 7.5 Hz, J ) 1.6 Hz, 2H),
7.94 (dd, J ) 8.4 Hz, J ) 1.9 Hz, 6H), 8.44 (m, 8H), 8.69 (d, J
) 4.8 Hz, 2H), 8.83 (s, 6H); 13C NMR (CDCl3) δ 14.2, 22.8,
26.2, 29.4, 29.5, 29.8, 32.0, 69.7, 89.8 (CtC), 90.2 (CtC), 90.5
(CtC), 92.1 (CtC), 92.2 (CtC), 92.3 (CtC), 113.8, 113.9,
114.0, 116.7, 120.4, 120.5, 120.7, 121.4, 137.0, 139.3, 149.4,
151.8, 153.9, 154.2, 154.9, 155.6; FT-IR (KBr, cm-1) 3056 (w),
2921 (s), 2852 (s), 2360 (m), 2342 (m), 2203 (w, νCtC), 1504
(m), 1458 (m), 1437 (s), 1384 (w), 1262 (m), 1217 (m), 1193 (s),
1120 (s), 1024 (m), 801 (m), 721 (s); UV-vis (CH2Cl2) λ, nm (ꢀ,
M-1 cm-1) 259 (12 900), 335 (19 800), 408 (36 900); FAB+ 2096
([M + H]+, 100), 1910 ([M - OC12H25]+, 30), 1741 ([M -
OC12H25 - C12H25]+, 20). Anal. Calcd for C142H182N8O6: C,
81.33; H, 8.75; N, 5.34. Found: C, 81.23; H, 8.71; N, 5.19.
Liga n d 14. This ligand was prepared according to experi-
mental condition 3, from 0.029 g (0.122 mmol) of 5-bromo-2,2′-
bipyridine, 10 mL of n-propylamine, 0.030 g (0.061 mmol) of
13, and 0.008 g (0.007 mmol) of [Pd(PPh3)4]. The reaction mix-
ture was heated for 20 h at 70 °C. Purification was performed
by chromatography on alumina with CH2Cl2 as the eluant and
afforded 0.041 g of 14 (84%): mp 105-6 °C; 1H NMR (CDCl3)
δ 0.86 (m, CH3, 6H), 1.25 (m, CH2, 36H), 1.88 (m, CH2, 4H),
4.06 (t, J ) 6.3 Hz, OCH2, 4H), 7.06 (s, Ph, 2H), 7.32 (t, J )
5.9 Hz, 2H), 7.83 (t, J ) 7.8 Hz, 2H), 7.93 (d, J ) 8.1 Hz, 2H),
8.42 (d, J ) 8.1 Hz, 4H), 8.69 (d, J ) 4.6 Hz, 2H), 8.83 (s, 2H);
13C NMR (CDCl3) δ 14.2, 22.8, 26.2, 29.5, 29.8, 32.0, 69.7, 90.2
(CtC), 92.1 (CtC), 113.9, 116.9, 120.4, 120.6, 121.4, 124.0,
137.0, 139.3, 149.4, 151.7, 153.9, 154.9, 155.6; FT-IR (KBr,
cm-1) 3447 (m), 3055 (w), 2921 (s), 2851 (s), 2356 (w), 2208
(w, νCtC), 1730 (m), 1587 (m), 1544 (m), 1502 (s), 1461 (s), 1415
(s), 1388 (m), 1276 (m), 1216 (s), 1128 (w), 1071 (s), 1026 (m),
Liga n d 20. This ligand was prepared according to experi-
mental condition 3, from 0.024 g (0.018 mmol) of 19b, 10 mL
of n-propylamine, 0.003 g (0.009 mmol) of 5,5′-dibromo-2,2′-
bipyridine, and 0.002 g (0,001 mmol) of [Pd(PPh3)4]. The
reaction mixture was heated for 4 days at 70 °C. Purification
was performed by chromatography on alumina with CH2Cl2/
CH3OH (0-10%) as the eluant and afforded 0.018 g of 20
(71%): mp 179-180 °C; 1H NMR (CDCl3) δ 0.86 (m, CH3, 24H),
1.24 (m, CH2, 144H), 1.89 (m, CH2, 16H), 4.07 (t, J ) 6.3 Hz,
OCH2, 16H), 7.07 (s, Ph, 8H), 7.34 (m, 2H), 7.78-7.97 (m, 10H),
8.32-8.47 (m, 10H), 8.70 (m, 3H), 8.84 (s, 7H); 13C NMR
(CDCl3) δ 14.2, 22.8, 26.2, 29.5, 29.7, 29.8, 32.0, 69.7, 83.9 (Ct
C), 87.3 (CtC), 87.4 (CtC), 90.5 (CtC), 90.6 (CtC), 92.1 (Ct
C), 92.2 (CtC), 113.9, 116.8, 120.7, 130.2, 131.5, 133.6, 139.3,
151.8, 153.9; FT-IR (KBr, cm-1) 3443 (w), 3303 (m), 3051 (m),
2923 (s), 2856 (s), 2361 (w), 2203 (w, νCtC), 1662 (m), 1593
(m), 1443 (s), 1379 (m), 1269 (m), 1184 (s), 1116 (s), 1030 (m),
886 (w), 714 (s); UV-vis (CH2Cl2) λ, nm (ꢀ, M-1 cm-1) 261
(14 400), 334 (23 900), 413 (39 900); FAB+ 2743 ([M + H]+,
996 (m), 862 (m), 745 (s); UV-vis (CH2Cl2) λ, nm (ꢀ, M-1 cm-1
)
260 (5900), 331 (13 000), 389 (13 700); FAB+ 803 ([M + H]+,
100), 617 ([M - OC12H25]+, 20). Anal. Calcd for C54H66N4O2:
C, 80.76; H, 8.28; N, 6.98. Found: C, 80.63; H, 8.13; N, 6.85.
Liga n d 16. This ligand was prepared according to experi-
mental condition 3, from 0.028 g (0.043 mmol) of 15b, 15 mL
of n-propylamine, 0.007 g (0.021 mmol) of 5,5′-dibromo-2,2′-
bipyridine, and 0.003 g (0,003 mmol) of [Pd(PPh3)4]. The
reaction mixture was heated for 3 days at 70 °C. Purification
was performed by chromatography on alumina with CH2Cl2
as the eluant and afforded 0.025 g of 16 (80%): mp 139-140
°C; 1H NMR (CDCl3) δ 0.86 (m, CH3, 12H), 1.23 (m, CH2, 72H),
1.88 (m, CH2, 8H), 4.07 (t, J ) 5.9 Hz, OCH2, 8H), 7.06 (s, Ph,
2H), 7.07 (s, Ph, 2H), 7.33 (m, 2H), 7.79-7.96 (m, 6H), 8.44
(m, 6H), 8.69 (d, J ) 4.8 Hz, 2H), 8.83 (s, 4H); 13C NMR (CDCl3)
δ 14.2, 22.8, 26.2, 29.3, 29.4, 29.5, 29.7, 32.0, 69.8, 88.2 (Ct
C), 90.2 (CtC), 90.5 (CtC), 92.2 (CtC), 113.9, 114.0, 116.9,
120.4, 120.5, 120.6, 120.7, 121.4, 124.0, 124.1, 137.1, 137.9,
139.3, 149.4, 151.7, 152.4, 153.9, 154.2, 155.6; FT-IR (KBr,
cm-1) 3415 (s), 3054 (w), 2922 (s), 2852 (s), 2364 (w), 2202 (w,
100), 2371 ([M - 2OC12H25]+, 30), 2244 ([M - 2OC12H25
-
C9H19]+, 10). Anal. Calcd for C186H240N10O8: C, 81.42; H, 8.82;
N, 5.10. Found: C, 81.19; H, 8.69; N, 4.75.
Ack n ow led gm en t. We warmly thank Professor
Anthony Harriman for a critical reading of the manu-
script and Dr. Lo¨ıc Charbonnie`re for his suggestion
concerning the effect of molecular oxygen on a potential
triplet state and for helpful discussions. The present
work was supported by the Centre National de la
Recherche Scientifique and by the Engineering School
of Chemistry in Strasbourg (ECPM).
J O000836K