A 1,10-phenanthroline-containing ring connected to a porphyrin by a rigid aromatic spacer and its copper-complexed pseudorotaxane

Article abstract of DOI:10.1002/ejic.200700177

A condensation reaction involving a free base tetraarylporphyrin-2,3-dione, a macrocyclic compound containing a 1,10-phenanthroline-5,6-dione and a 1,2,4,5-tetraminobenzene as a linker affords the corresponding conjugate in good yield. The porphyrin ring and the phenanthroline fragment of the other ring are connected in such a way that mutual rotation between these two groups is prohibited. Metallation of the porphyrinic site affords the corresponding zinc complex. By reacting this zinc porphyrin with copper(I), followed by the addition of the bidentate chelate 2,9-bis(p-anisyl)-1,10-phenanthroline, the threading reaction leading to the corresponding pseudorotaxane takes place quantitatively. Wiley-VCH Verlag GmbH & Co. KGaA, 2007.

Full text of DOI:10.1002/ejic.200700177

FULL PAPER
DOI: 10.1002/ejic.200700177
A 1,10-Phenanthroline-Containing Ring Connected to a Porphyrin by a Rigid
Aromatic Spacer and Its Copper-Complexed Pseudorotaxane
Julien Frey,[a] William Dobbs,[a] Valérie Heitz,*[a] and Jean-Pierre Sauvage*[a]
Keywords: Ligand design / Porphyrinoids / Macrocycles / Template synthesis / Rotaxane
A condensation reaction involving a free base tetraarylpor-
phyrin-2,3-dione, a macrocyclic compound containing a 1,10-
phenanthroline-5,6-dione and a 1,2,4,5-tetraminobenzene as
a linker affords the corresponding conjugate in good yield.
The porphyrin ring and the phenanthroline fragment of the
other ring are connected in such a way that mutual rotation
between these two groups is prohibited. Metallation of the
porphyrinic site affords the corresponding zinc complex. By
reacting this zinc porphyrin with copper(I), followed by the
addition of the bidentate chelate 2,9-bis(p-anisyl)-1,10-phen-
anthroline, the threading reaction leading to the correspond-
ing pseudorotaxane takes place quantitatively.
(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim,
Germany, 2007)
Porphyrins have been incorporated in rotaxanes and cat-
The synthetic strategy relies on porphyrin α-dione 1 sim-
enanes as electro- and photoactive components, mostly in ilar to that used by Crossley and coworkers for making di-
relation to models of the photosynthetic reaction centre, to and multiporphyrins as well as electrodeficient porphyrins
host–guest chemistry or to dynamic systems able to un- with quinoxaline groups at their periphery.[4] The other im-
dergo large amplitude motions.[1] Our group has been par- portant fragment, namely the macrocycle containing phen-
ticularly interested in energy and electron transfer studies anthroline dione 2, was prepared in our group in the frame
within such rotaxanes or catenanes.[2] The porphyrin nu- of another project dealing with multirotaxanes.[5] Phenan-
cleus can be used as a stopper (for rotaxanes), either at- throline–porphyrin conjugates with back-to-back connec-
tached to or part of the ring.[3] Till now, limited geometrical tion were described recently by other groups but in these
control could be achieved as the mutual orientation be- examples, the 1,10-phenanthroline part was not contained
tween the porphyrin and the ring was not controlled, espe- within the macrocycle.[6]
cially when the porphyrin fragment was appended to the
Starting diones 1 and 2, as well as the condensation reac-
cyclic component(s) of the rotaxane or the catenane. To tion leading to porphyrin conjugates 4 and 5, are repre-
have strict geometrical control over the system, it is neces- sented in Figure 1.
sary to connect the porphyrin and the ring by a rigid spacer,
The synthesis of porphyrin α-dione 1 proceeds from the
for which free rotation is not allowed. In the present report, copper(II) complex of meso-tetra(3Ј,5Ј-di-tert-butylphenyl)-
we would like to describe the synthesis of such a conjugate porphyrin, which was first reacted with LiNO3 in AcOH/
consisting of a 30-membered ring built from 2,9-diaryl- Ac2O to afford the corresponding β-nitro copper(II) por-
1,10-phenanthroline and a free-base porphyrin or a zinc- phyrin in high yield (90%) as described by Callot.[7] Then,
complexed porphyrin. The spacer between these two com- adapted from Burn’s methodology,[8] this porphyrin was de-
ponents is a rigid aromatic nucleus. In addition, to demon- metallated with H2SO4 and the NO2 function was reduced
strate that the rigidly held porphyrin-macrocycle conjugates to an NH2 group by SnCl2 and HCl in CH2Cl2. The subse-
prepared can be used as components of interlocking struc- quent oxidation reaction leading to 1 was carried out by
ture, we have assembled a pseudorotaxane using the cop- using Dess–Martin periodinane. The analytical and spectro-
per(I)-based strategy already applied in other related reac- scopic properties of the compound obtained are similar to
tions.[2,3] The threaded species obtained by mixing the Zn- those of the literature.[8] Compound 1 was obtained from
containing porphyrin-ring conjugate, copper(I) and a coor- the starting copper(II) porphyrin in four steps (nitration,
dinating fragment of the 1,10-phenanthroline family, is in- demetallation, reduction and oxidation) with an overall
deed obtained in quantitative yield.
yield of approximately 40%.
The coupling reaction between 1 and 2[5] was performed
by
a stepwise condensation using 1,2,4,5-benzenetet-
[a] Laboratoire de Chimie Organo-Minérale, LC 3 UMR 7177 du
CNRS, Institut de Chimie, Université Louis Pasteur,
4 rue Blaise Pascal, 67070 Strasbourg Cedex, France
E-mail: heitz@chimie.u-strasbg.fr
ramine.[6] Porphyrin α-dione 1 and benzenetetramine tetra-
hydrochloride 3 (1.2 equiv.) were dissolved in freshly dis-
tilled pyridine, and the reaction mixture was kept in the
sauvage@chimie.u-strasbg.fr
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Cyclic Porphyrin-Containing ligand and Its Copper-Complexed Pseudorotaxane
FULL PAPER
Figure 1. Stepwise condensation of the two diones with the bridging spacer.
dark. After gentle stirring at room temperature under an
atmosphere of argon for 3 d, macrocycle 2 (1.5 equiv.) was
added, and the reaction was prolonged under the same re-
action conditions for an additional week. After workup and
chromatographic purification (silica gel, CH2Cl2 with in-
creasing amounts of CH3OH – up to 0.3% – as eluent), 4
was obtained as a violet solid in 75% yield. It was fully
1
characterised by H NMR spectroscopy and high resolu-
tion (HR) ESMS.
Metallation of the porphyrinic site of 4 was selectively
carried out by the addition of Zn(OAc)2 (5 equiv., dissolved
in CH3OH) to a solution of 4 in CH2Cl2 heated at reflux.[6]
Further treatment with an EDTA solution to remove ZnII
from the phenanthroline chelate allowed 5 to be obtained
quantitatively from 4.
1
The H NMR spectra are in accordance with the struc-
tures of the compounds (Figure 2). As expected from the
formation of the bridge at the back of the phenanthroline,
protons 1 and 4,7 are strongly shifted upfield. Owing to
1
the C2v symmetry of the molecule, protons tBu1 differ from
protons tBu2, which gives rise to two sets of signals. For
the same reason, proton py3 is assigned to a characteristic
singlet at δ = 8.76 ppm.
Figure 2. H NMR spectra (aromatic region) of compounds 5 and
7·PF6 in CD2Cl2.
Compounds 4 and 5 are well adapted to the synthesis of
more elaborate catenanes and rotaxanes. As an example,
pseudorotaxane 7·PF6 was prepared quantitatively from the
various corresponding organic fragments, 5 and 6, in the
presence of copper(I), acting as a gathering and threading
centre. As represented in Figure 3, 6 is a 2,9-disubstituted
1,10-phenanthroline that is able to form very stable four-
coordinate complexes with copper(I) once associated to an-
other bidentate chelate of the 1,10-phenanthroline family.
As expected, the reaction proceeded very cleanly: stoichio-
metric amounts of 5 and [Cu(CH3CN)4](PF6) were first
mixed in dichloromethane to afford the desired copper(I)
complex. Subsequently, a stoichiometric quantity of 6 was
added, which led to desired pseudorotaxane 7 quantitatively
after workup. Compound 7·PF6 is a deep purple solid,
which was characterised by 1H NMR (COSY-ROESY) and
electronic spectroscopy and HRESMS.
Figure 3. The threading reaction affording pseudorotaxane 7.
To estimate the electronic coupling between the various sorption and emission measurements were performed. The
aromatic fragments of 5 and 7 (the 1,10-phenanthroline absorption and emission spectra of the two compounds are
chelate and the zinc-containing porphyrin), electronic ab- represented in Figure 4.
Eur. J. Inorg. Chem. 2007, 2416–2419
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J. Frey, W. Dobbs, V. Heitz, J.-P. Sauvage
FULL PAPER
Experimental Section
General: Nuclear Magnetic Resonance (NMR) spectra were ac-
quired with Bruker AM300 spectrometer operating at
a
300.17 MHz. The spectra were referenced internally to residual
proton-solvent reference. High resolution electrospray mass spectra
(HRESMS) were recorded with a VG BOIQ triple quadrupole
spectrometer by the Service de Spectrométrie de Masse (ISIS, Stras-
bourg). All anhydrous solvents were prepared by distillation under
an atmosphere of argon with the use of the appropriate drying
agents. All commercial chemicals were at the best commercially
available grade and used without further purification. Thin layer
chromatography was carried out with precoated polymeric sheets
of silica gel (Macheray-Nagel, POLYGRAM, SIL G/UV254) and
preparative column chromatography was carried out by using silica
gel (Merck Kiesegel, silica gel 60, 0.063–0.200 mm).
Figure 4. Normalised absorption and emission spectra (inset) of an
optically matched solution of 5 (thin) and 7·PF6 (bold) (excitation
at 438 nm) at 298 K in dichloromethane.
Compound 4: Avoiding light exposure, porphyrin tetraone 1 (50 mg,
4.58ϫ10–5 mol) and benzene tetramine tetrahydrochloride
3
(15.7 mg, 5.53ϫ10–5 mol, 1.2 equiv.) were dissolved in freshly dis-
Interestingly, the Soret band for the two porphyrin-con-
taining compounds is bathochromically shifted relative to tilled pyridine (25 mL), and the mixture was stirred at room tem-
that of the classical tetraaryl porphyrins.[9] Whereas a nor-
perature under an atmosphere of argon. After 2 d, macrocyclic di-
one 2 (41 mg, 6.87ϫ10–5 mol, 1.5 equiv.) was added under a stream
of argon, and the solution was reacted for another week under
the same conditions. After removal of the solvent, the product was
extracted with CH2Cl2 (50 mL) and water (50 mL). The organic
mal Soret band is typically observed around 420 nm for Zn
porphyrins of this series, the present compounds show a
Soret band in the range 435–440 nm. In addition, signifi-
cant broadening is observed, which is a clear indication that
layers were separated, washed with water (2ϫ50 mL) and the sol-
the aromatic system is perturbed by the presence of the tet-
vents evaporated to dryness. The crude product (154 mg) was sub-
raazaanthracene nucleus at the periphery of the porphyrin,
jected to column chromatography (110 g of silica, prepared in
as already observed by Flamigni and coworkers.[10] The ob-
served broadening is likely to be due to the loss of sym-
CH2Cl2, gradient elution from CH2Cl2/MeOH 0 to 0.3%) to give
1
compound 4 as a purple solid (60 mg, 75%). H NMR (300 MHz,
3
metry of the porphyrin aromatic system by introducing CD2Cl2, COSY-ROESY, 25 °C): δ = 9.75 (d, JH,H = 8.4 Hz, 2 H,
3
3
H
4,7), 9.10 (d, JH,H = 4.9 Hz, 2 H, Hpy1), 9.03 (d, JH,H = 4.9 Hz,
a tetraazaanthracene fragment at its rim. A contribution
of a hypothetical 1,10-phenanthroline-porphyrin electronic
coupling cannot be excluded.
3
2 H, Hpy2), 8.95 (s, 2 H, Hpy3), 8.76 (s, 2 H, H1), 8.56 (m, JH,H
=
8.8 Hz, 4 H, Ho), 8.31 (d, 3JH,H = 8.5 Hz, 2 H, H3,8), 8.12–8.05 (m,
4
10 H, Hop1, Hop2, Hpp2), 7.86 (t, JH,H = 1.8 Hz, 2 H, Hpp1), 7.28
(m, JH,H = 8.9 Hz, 4 H, Hm), 4.39 (t, JH,H = 5.9 Hz, 4 H, Hα),
3.88 (t, JH,H = 5.9 Hz, 4 H, Hβ), 3.76–3.64 (m, 12 H, Hγ, Hδ, Hε),
Whereas the absorption spectra of 5 and 7 are signifi-
cantly different from that of a normal zinc(II) tetraarylpor-
phyrin, their emission spectra have emission maxima at sim-
ilar values (5 and 7; λ = 606, 655 nm). The tetraazaanthra-
cene phenanthroline aromatic fragment at the back of the
porphyrin has therefore little influence on the energy level
of the lowest excited state of the porphyrin ring. This is
quite surprising considering that in related tetraazaanthra-
cene-substituted porphyrins studied by Flamigni and co-
workers,[10] the excited state was stabilised by 0.2 eV. Never-
theless, in 5 and 7, the emission intensity decreases dramati-
cally and the quantum yield of the emission relative to that
of zinc(II) 5,10,15,20-tetrakis(3,5-di-tert-butylphenyl)por-
phyrin is only 0.3%. Further photophysical studies will be
performed to understand these results.
3
3
3
1.57 (s, 36 H, HtBu2), 1.54 (s, 36 H, HtBu1), –2.35 (br. s, 2 H, HNH
)
ppm. UV/Vis (CH2Cl2): λ (logε) = 434 (5.54) nm. HRESMS: calcd.
for C166H127N10O6 and for 1/2[C166H127N10O6]2 [4 + H]+ and [4 +
2+
H]2 1756.9967; found 1757.0025.
Compound 5: A solution of Zn(OAc)2 (34 mg, 1.55ϫ10–4 mol, ca.
5 equiv.) in MeOH (7 mL) was added to a boiling solution of com-
pound 4 (50 mg, 2.85ϫ10–5 mol) in CH2Cl2 (25 mL), and the mix-
ture was heated at reflux for 6 h. After removal of the solvents, the
product was extracted with CH2Cl2 (50 mL) and water (2ϫ50 mL).
The organic layers were separated, and the volume of the solution
was reduced to approximately 30 mL. A solution of [EDTA]Na4
(0.1 , pH ca. 4–5, 10 mL) was added, and the mixture was stirred
for 24 h. The organic layers were then extracted with CH2Cl2
In conclusion, a new conjugate consisting of a porphyrin (80 mL), separated, washed with saturated Na2CO3 (50 mL), brine
(50 mL) and water (100 mL) and the solvents evaporated to dryness
and a coordinating ring was prepared in a few steps from
sophisticated organic fragments, with a relatively good
overall yield. The zinc-complexed porphyrinic system was
further utilised to prepare a novel pseudorotaxane by tak-
ing advantage of the template effect of copper(I). The con-
jugate itself, either containing a free base or a zinc porphy-
rin, is rigid, which allows strict control over the geometry
of the system and over that of the pseudorotaxane pre-
pared. The same will hold true for future, more complex
rotaxanes and catenanes containing 4 and 5.
to give quantitatively compound 5 (51 mg). 1H NMR (300 MHz,
3
CD2Cl2, COSY-ROESY, 25 °C): δ = 9.69 (d, JH,H = 8.4 Hz, 2 H,
H4,7), 8.98 (s, 2 H, Hpy3), 8.97–8.94 (2d, 3JH,H = 4.8 Hz, 4 H, Hpy1
Hpy2), 8.85 (s, 2 H, H1), 8.48 (m, JH,H = 8.8 Hz, 4 H, Ho), 8.24
,
3
3
(d, JH,H = 8.5 Hz, 2 H, H3,8), 8.11–8.04 (m, 10 H, Hop1, Hop2
,
4
3
Hpp2), 7.85 (t, JH,H = 1.8 Hz, 2 H, Hpp1), 7.18 (m, JH,H = 8.8 Hz,
4 H, Hm), 4.26 (t, 3JH,H = 5.9 Hz, 4 H, Hα), 3.73 (t, 3JH,H = 5.9 Hz,
4 H, Hβ), 3.62–3.51 (m, 12 H, Hγ, Hδ, Hε), 1.57 (s, 36 H, HtBu2),
1.55 (s, 36 H, HtBu1) ppm. UV/Vis (CH2Cl2): λ (logε) = 437 (5.47),
515 (4.66) nm. HRESMS: calcd. for C116H124N10O6Zn [5 – e]+
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© 2007 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Inorg. Chem. 2007, 2416–2419

Cyclic Porphyrin-Containing ligand and Its Copper-Complexed Pseudorotaxane
FULL PAPER
Li, D. M. Guldi, J. Ramey, Org. Lett. 2004, 6, 1919–1922; h)
M. J. Gunter, T. P. Jeynes, P. Turner, Eur. J. Org. Chem. 2004,
193–208 and references cited therein.
1818.9017; found 1818.8987 and calcd. for C116H125N10O6Zn [5 +
H]+ 1819.9095; found 1819.9013.
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Compound 7·PF6:
A solution of [Cu(MeCN)4](PF6) (3.6 mg,
9.34ϫ10–6 mol) in MeCN (5 mL) was added by cannula to a de-
gassed solution of 4 (17.0 mg, 9.34ϫ10–6 mol) in CH2Cl2 (5 mL),
and the mixture was stirred under an atmosphere of argon for
30 min. A degassed solution of dianisyl phenanthroline 6 (3.67 mg,
9.34ϫ10–6 mol) in CH2Cl2 (5 mL) was then also added by cannula.
After stirring for 2 h, the solution was extracted with CH2Cl2
(50 mL) and water (50 mL); the organic layers were separated,
dried with MgSO4 and evaporated to give pure rotaxane 7 as its
PF6 salt (22 mg, 97%). 1H NMR (300 MHz, CD2Cl2, COSY-
3
ROESY, 25 °C): δ = 9.88 (d, JH,H = 8.4 Hz, 2 H, H4,7), 9.16 (s, 2
3
H, Hpy3), 8.97–8.98 (2d, JH,H = 4.6 Hz, 4 H, Hpy1, Hpy2), 8.86 (s,
3
2 H, H1), 8.68 (d, JH,H = 8.4 Hz, 2 H, H4Ј,7Ј), 8.22 (s, 2 H, H5Ј,6Ј),
4
4
8.13 (t, JH,H = 1.8 Hz, 2 H, Hpp2), 8.13 (t, JH,H = 1.7 Hz, 2 H,
3
Hpp1), 8.06 (m, 10 H, H3,8, Hop1, Hop2), 7.94 (d, JH,H = 8.4 Hz, 2
4
3
H, H3Ј,8Ј), 7.87 (t, JH,H = 1.7 Hz, 2 H, Hpp1), 7.57 (m, JH,H
=
8.6 Hz, 4 H, HoЈ), 7.35 (m, 3JH,H = 8.6 Hz, 4 H, Ho), 6.27 (m, 3JH,H
3
= 8.6 Hz, 4 H, HmЈ), 6.04 (m, JH,H = 8.6 Hz, 4 H, Hm), 3.85 (s, 4
H, Hε), 3.79–3.55 (3m, 16 H, Hδ, Hγ, Hβ, Hα), 3.26 (s, 6 H, HOMe),
1.60 (s, 36 H, HtBu2), 1.55 (s, 36 H, HtBu1) ppm. UV/Vis (CH2Cl2):
λ (logε) = 440 (5.55), 532 (4.55) nm. HRESMS: calcd. for
C142H144N12O8CuZn 2274.9843; found 2274.9647.
Acknowledgments
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We thank the Ministry of Education for a fellowship to J. F. We
are also grateful to Professor H. Callot for helpful discussions.
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Received: February 6, 2007
Published Online: April 16, 2007
Eur. J. Inorg. Chem. 2007, 2416–2419
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