Synthesis of a linear bis-porphyrin with a Ru(phen)22+-complexed 2,2′-bipyridine spacer

Article abstract of DOI:10.1039/b202407c

A linear bis-porphyrin bridged by a 5,5′-diphenyl-2,2′-bipyridine rod-like spacer complexing a [Ru(phen)₂]²⁺ fragment has been synthesized in 7.4% yield by one-pot condensation of 3,5-di-tert-butylbenzaldehyde, 4,4′-dimethyl-3,3′-dihexyl-2,2′-methylenedipyrrole and the [Ru(phen)₂]²⁺ complex of 5,5′-bis(p-formylphenyl)-2,2′-bipyridine, followed by chloranil oxidation. The protected dialdehyde (5,5′-bis[(5,5-dimethyl-1,3-dioxan-2-yl)phenyl]-2,2′-bipyridine) was obtained in 80% yield by Suzuki coupling of 2-[4-(5,5-dimethyl-1,3-dioxan-2-yl)phenyl]-4,4,5,5-tetramethyl-1, 3-dioxaborolane and 5,5′-dibromo-2,2′-bipyridine, using [Pd(PPh₃)₄] as catalyst. A new procedure is reported for the preparation of 5,5′-dibromo-2,2′-bipyridine, which is obtained in 80% yield by Stille homocoupling of 2,5-dibromopyridine in the presence of hexamethylditin.

Full text of DOI:10.1039/b202407c

View Article Online / Journal Homepage / Table of Contents for this issue
2؉
Synthesis of a linear bis-porphyrin with a Ru(phen)2 -complexed
2,2Ј-bipyridine spacer
James I. Bruce, Jean-Claude Chambron,*† Philipp Kölle and Jean-Pierre Sauvage*
1
Laboratoire de Chimie Organo-Minérale, Université Louis Pasteur, Institut Le Bel,
4 rue Blaise Pascal, 67000 Strasbourg, France
Received (in Cambridge, UK) 7th March 2002, Accepted 5th April 2002
First published as an Advance Article on the web 23rd April 2002
A linear bis-porphyrin bridged by a 5,5Ј-diphenyl-2,2Ј-bipyridine rod-like spacer complexing a [Ru(phen)2]2ϩ
fragment has been synthesized in 7.4% yield by one-pot condensation of 3,5-di-tert-butylbenzaldehyde, 4,4Ј-
dimethyl-3,3Ј-dihexyl-2,2Ј-methylenedipyrrole and the [Ru(phen)2]2ϩ complex of 5,5Ј-bis(p-formylphenyl)-2,2Ј-
bipyridine, followed by chloranil oxidation. The protected dialdehyde (5,5Ј-bis[(5,5-dimethyl-1,3-dioxan-2-yl)phenyl]-
2,2Ј-bipyridine) was obtained in 80% yield by Suzuki coupling of 2-[4-(5,5-dimethyl-1,3-dioxan-2-yl)phenyl]-4,4,5,5-
tetramethyl-1,3-dioxaborolane and 5,5Ј-dibromo-2,2Ј-bipyridine, using [Pd(PPh3)4] as catalyst. A new procedure is
reported for the preparation of 5,5Ј-dibromo-2,2Ј-bipyridine, which is obtained in 80% yield by Stille homocoupling
of 2,5-dibromopyridine in the presence of hexamethylditin.
In this paper we describe our synthetic efforts to covalently
and rigidly link two porphyrins in a strict linear arrangement
Introduction
Bis-porphyrin conjugates are attracting considerable attention
using the 5,5Ј-diphenylene-2,2Ј-bipyridine chelate as spacer
as many electron transfer proteins involve pairs of porphyrin
(Fig. 1, structure (b)). A few examples of bis-porphyrins
analogues as redox partners. Among those, examples involving
incorporating the 2,2Ј-bipyridine subunit are known,4 and
cytochromes as well as bacteriochlorophylls can be borrowed
several linear bis-porphyrins involving bridging metal complex
from the photosynthetic machinery of purple bacteria such as
fragments such as [M(terpy)2]nϩ (where M = Ru()5a–c or
Rhodopseudomonas viridis.1 We have been interested for several
Ir()5d–f) or [M(phen)2]nϩ (where M = Cu() or Zn())6 have
years in mimicking the oblique arrangements in pairs of
chromophores taken from the special pair/bacteriochlorophyll/
been synthesized in our laboratory and elsewhere. However, the
latter correspond to structure (c) of Fig. 1, in which the metal
bacteriopheophytin triad of the bacterial Reaction Centers. For
has been shown to play both the role of an assembling species,
that purpose we designed and synthesized bis-porphyrins with
linking together the porphyrin modules, and a redox relay
covalent bridges such as the 2,9-diphenyl-1,10-phenanthroline
mediating photoinduced electron transfer between the Zn and
(dpp) ligand, which enforces a 60Њ angle between the porphyrin
the Au porphyrin termini in the case of M(terpy)2nϩ-bridged
planes.2 Precursors to phototriggered donor–acceptor con-
systems.5 An exception is a multiporphyrin-containing [2]-
jugates were obtained by metallation with Zn() and Au().3a–c
rotaxane, in which the bridging phenanthroline chelate is
We observed that the rate of electron transfer from the photo-
connected to the porphyrin stoppers by amide linkages.7 For
excited Zn porphyrin donor to the Au porphyrin acceptor could
practical reasons (see below), the [Ru(phen)2]2ϩ moiety had to
be substantially increased by coordination of a transition metal
be attached to the bipyridine spacer prior to porphyrin con-
to the bridging chelate by means of rotaxane formation (Fig. 1,
struction, thus providing a new [Ru(diimine)3]2ϩ–porphyrin
structure (a)).3d,e
conjugate.8
Results and discussion
5,5Ј-Diphenyl-2,2Ј-bipyridine itself is not a very common
ligand, compared to the 4,4Ј-diphenyl analogue, and only a few
of its complexes with Ru() have been described.9a The free
ligand has been prepared by Raney nickel coupling of 3-
phenylpyridine,9b a method that does not tolerate heat sensitive
functional groups and that suffers from very moderate yields.
In recent preparations of materials incorporating the 5,5Ј-
diaryl-2,2Ј-bipyridine motif, aromatic cross-coupling reactions
involving 5,5Ј-dibromo-2,2Ј-bipyridine as electrophile have
been used with much success. Tilley and coworkers have pre-
Fig.
1
Schematic representation of selected mixed-metal bis-
pared 5,5Ј-bis(4-trimethylsilylphenyl)-2,2Ј-bipyridine in 90%
yield by Stille coupling with Me3SiC6H4SnMe3.10 Suzuki
coupling was used by Klemm and coworkers to prepare
polymers incorporating the 5,5Ј-bis(2,5-dihexylphenyl)-2,2Ј-
bipyridine motif, using 2,5-dihexylbenzene-1,4-diboronic
acid as nucleophile.11a The same reaction has been applied to
(5,5Ј-dibromo-2,2Ј-bipyridine)-bis(2,2Ј-bipyridine)ruthenium-
() bis(hexafluorophosphate), affording a conjugated polymer
porphyrin arrays containing a transition metal complex fragment as
spacer. The thick lines represent bidentate (a and b) or terdentate (c)
chelates. The black disk is a transition metal. Metalloporphyrins are
represented by diamonds (empty = Zn(); full = Au()).
† Present address: LIMSAG (UMR 5633), Université de Bourgogne,
Faculté des Sciences Gabriel, 6, boulevard Gabriel, 21000 Dijon,
France
1226
J. Chem. Soc., Perkin Trans. 1, 2002, 1226–1231
This journal is © The Royal Society of Chemistry 2002
DOI: 10.1039/b202407c

View Article Online
containing an appended ruthenium() bipyridine complex.11b
In the present case, we also found it very convenient to use a
Suzuki coupling12 between 5,5Ј-dibromo-2,2Ј-bipyridine and
the appropriate aromatic boronic ester to prepare the function-
alized precursor of the 5,5Ј-diphenylene-2,2Ј-bipyridine bridge.
Accordingly, the linear bis-porphyrins 82ϩ (free-base) and
112ϩ (Zn complex) were synthesized in several steps from the
key compounds 5,5Ј-dibromo-2,2Ј-bipyridine 2 and 2-[4-(5,5-
dimethyl-1,3-dioxan-2-yl)phenyl]-4,4,5,5-tetramethyl-1,3-dioxa-
borolane 5, as shown in Schemes 1–4. Earlier reports describing
the preparation of 5,5Ј-dibromo-2,2Ј-bipyridine (2) involve
Ullman-type coupling of 2-chloro-5-bromopyridine,13 multi-
step transformations from 5,5Ј-disubstituted-2,2Ј-bipyridines,14
or direct bromination of the 2,2Ј-bipyridine hydrobromide
salt.15 The latter method also produces 5-bromo-2,2Ј-
bipyridine, which has to be separated from its disubstituted
homologue. The yield of isolated 5,5Ј-dibromo-2,2Ј-bipyridine
Scheme 1
Scheme 3
[(trifluoromethyl)sulfonyl]pyridine-5-carboxylate and 2-(tri-
methylstannyl)-5-nitropyridine, we found that simple heating
of commercially available 2,5-dibromopyridine (1) and hexa-
methylditin in the presence of [Pd(PPh3)4] afforded, after 3 days
reaction in refluxing benzene, the desired 5,5Ј-dibromo-2,2Ј-
bipyridine (2) in 80% yield after chromatography. This one-pot
reaction allowed the preparation of 2 in 4–5 g scale amounts.
Separately, as shown in Scheme 2, boronic ester 5 was
obtained in 80% yield by treating p-(5,5-dimethyl-1,3-dioxan-2-
yl)bromobenzene 4 with t-BuLi (2 equiv.) followed by sequen-
tial addition of trimethyl borate and pinacol.17 Subsequent
coupling with 5,5Ј-dibromo-2,2Ј-bipyridine 2 (0.5 equiv.) using
Suzuki conditions ([Pd(PPh3)4], 1 mol dmϪ3 aqueous Na2CO3,
toluene, reflux) afforded the protected dialdehyde 6 in 80% yield
after flash chromatography. The corresponding dialdehyde 7,
which was obtained in 90% yield by hydrolysis with 5% aqueous
HCl in THF at 50 ЊC, turned out to be poorly soluble in com-
mon organic solvents, and in our hands, did not react with the
appropriate reagents (see below) to form the bis-porphyrin.
Therefore, in the next step, the functionalized 5,5Ј-diphenyl-
2,2Ј-bipyridine derivative 6 was directly complexed to Ru(), by
reaction with Ru(phen)2Cl2 in refluxing n-butanol (Scheme 3).
The deep-orange complex [Ru(phen)26]2ϩ was precipitated in
71% yield as its PF6Ϫ salt. Deprotection was done as above and
afforded the dialdehyde [Ru(phen)27](PF6)2 in 89% yield.
Bis-porphyrin [8](PF6)2 was formed in the one-pot reaction18
of dialdehyde [Ru(phen)27](PF6)2 (1 equiv.), 3,5-di-tert-butyl-
benzaldehyde (9)19 (8 equiv.) and 3,3Ј-dihexyl-4,4Ј-dimethyl-
2,2Ј-methylenedipyrrole (10)20 (10 equiv.) in dichloromethane
containing a few drops of trifluoroacetic acid, first at room
temperature, then at reflux after the addition of tetrachloro-p-
quinone (chloranil) to achieve oxidation of the porphyrinogen
intermediates (Scheme 4). The desired compound was purified
Scheme 2
is <50%. Adapting a procedure developed by Torrado and
Imperiali16 for making non-symmetrical methyl 5Ј-nitro-2,2Ј-
bipyridine-5-carboxylate by Stille coupling of methyl 2-
J. Chem. Soc., Perkin Trans. 1, 2002, 1226–1231
1227

View Article Online
Scheme 4
by repeated column chromatography on silica gel and alumina,
and isolated in 7.4% yield. Subsequent reaction with two equiv-
alents of Zn(OAc)2ؒ2H2O afforded bis-porphyrin [11](PF6)2.
It can be noted that, in the course of the chromatographic
purification of bis-porphyrin [8](PF6)2, the porphyrin–Ru con-
jugate [12](PF6)2, which bears a free aldehyde function, could be
isolated in 2% yield from the reaction mixture.
Schlenk techniques. Benzene and toluene were distilled from
Na, THF was distilled from Na–benzophenone, and CH2Cl2
was distilled from P2O5 prior to use. Common reagents and
materials were purchased from commercial sources. The
following materials were prepared according to literature pro-
cedures: p-(5,5-dimethyl-1,3-dioxan-2-yl)bromobenzene (1),22
[Ru(phen)2Cl2],23 3,3Ј-dihexyl-4,4Ј-dimethyl-2,2Ј-methylenedi-
pyrrole (10),20 and 3,5-di-tert-butylbenzaldehyde (9).19 Thin-
layer chromatography (TLC) was performed on glass plates
coated with silica gel 60 F254 (E. Merck). Column chroma-
tography was carried out on silica gel 60 (E. Merck, 70–230
The bis-porphyrins were characterized by 1H-NMR,
FAB–MS and UV–Vis. The data compiled in the Experimental
section are in agreement with the expected structures (Scheme
5), with signatures of the porphyrins and the Ru complex frag-
ment. For example, the following correlations were found in the
ROESY maps of bis-porphyrin [11](PF6)2: op-CH3d, CH3d-αd,
αd-meso, meso-αp, αp-CH3p, CH3p-m, o-γ, o-α, 4–5, and 6–7,
which, taken together with the COSY correlations could allow
full assignment of the spectrum.
1
mesh). H NMR spectra were obtained on either Bruker WP
200 SY (200 MHz) or AM 400 (400 MHz) spectrometer.
NMR chemical shifts δ are expressed in ppm relative to
TMS. The coupling constants J are measured in Hz. Labels of
the protons of the bis-porphyrins are provided in Scheme 5.
Fast atom bombardment mass spectrometry (FAB MS) data
were recorded in the positive ion mode with a xenon primary
atom beam in conjunction with a 3-nitrobenzyl alcohol matrix
and a ZAB–HF mass spectrometer. Melting points were
determined in open capillary tubes on a Büchi 530 apparatus,
and are uncorrected. Elemental analyses were performed
by the Service de Microanalyse de l’Institut de Chimie de
Strasbourg.
Conclusion
We have described the multistep synthesis of a linear bis-
porphyrin rigidly bridged by a 5,5Ј-diphenylene-2,2Ј-bipyridine
spacer complexing a [Ru(phen)2]2ϩ metal complex fragment. It
is noteworthy that the key starting material, 5,5Ј-dibromo-2,2Ј-
bipyridine, was prepared in good yield using a new route,
i.e. Stille homocoupling of 2,5-dibromopyridine. Formally, the
two porphyrins rings are separated by four p-phenylene-like
groups, which makes our system a higher homologue of the
existing bis-porphyrin compounds connected by up to three
p-phenylene linkers.21
5,5Ј-Dibromo-2,2Ј-bipyridine 2
2,5-Dibromopyridine (8.00 g, 0.0338 mol), hexamethylditin
(5.53 g, 0.0169 mol) and [Pd(PPh3)4] (0.80 g) were refluxed in
benzene (250 cm3) for 65 h under argon. The reaction mixture
was cooled and ether (200 cm3) added. An off-white precipitate
was filtered off and chromatographed on silica gel. Eluting with
CHCl3–CH3OH (99.9 : 0.1) gave 2 as a white solid (4.21 g, 80%),
mp 225.5–226.5 ЊC (lit.13 224–225 ЊC); δH (200 MHz; CDCl3;
Me4Si) 8.71 (2H, d, J1,4 2, α-H), 8.30 (2H, dd, J1,5 0.6, J1,3 8.5, δ-
H), 7.94 (2H, dd, J1,4 2.3, J1,3 8.5, γ-H).
Experimental
General methods
Oxygen or water-sensitive reactions were conducted under
a positive pressure of argon in oven-dried glassware, using
1228
J. Chem. Soc., Perkin Trans. 1, 2002, 1226–1231

View Article Online
Scheme 5 Structural formulae of compounds [8](PF6)2, [11](PF6)2, and [12](PF6)2, with atom labelling used in the 1H-NMR assignments. Double
ended arrows show main ROESY correlations.
2-[4-(5,5-Dimethyl-1,3-dioxan-2-yl)phenyl]-4,4,5,5-tetramethyl-
1,3-dioxaborolane 5
ethanol and dried to give 6 as a white solid (1.25 g, 80%), mp
>250 ЊC (Found: C, 71.26; H, 6.64; N, 4.81. C34H36N2O4ؒ2H2O
requires C, 71.31; H, 7.04; N, 4.89%); δH (200 MHz; CDCl3;
Me4Si): 8.93 (2H, d, J1,4 2.3, α-H), 8.51 (2H, d, J1,3 8.2, δ-H),
8.04 (2H, dd, J1,3 8.3, J1,4 2.3, γ-H), 7.67 (8H, s, Ar–H), 5.48
(2H, s, CH), 3.76 (8H, dd, JAB 11.0, CH2), 1.33 (6H, s, CH3),
0.84 (6H, s, CH3).
To a cold solution of p-(5,5-dimethyl-1,3-dioxan-2-yl)bromo-
benzene 4 (1.00 g, 3.68 mmol) in THF (40 cm3) at Ϫ75 ЊC under
argon, a solution of t-BuLi (1.4 mol dmϪ3 in pentane, 5.52 cm3,
7.74 mmol) was slowly added, keeping the temperature below
Ϫ70 ЊC. This was followed 20 min later by trimethyl borate
(0.451 cm3, 4.05 mmol). The temperature was allowed to
rise slowly up to room temperature over 2.5 h. Pinacol (0.982 g,
8.31 mmol) was added and 10 min later the reaction was
quenched with acetic acid (0.215 cm3, 3.77 mmol). The reaction
mixture was filtered through Celite, the filter washed with
diethyl ether and the solvents removed from the filtrate under
reduced pressure. The yellow residue was dissolved in CHCl3–
H2O (50 : 50, 40 cm3). The organic phase was separated and
washed with water (3 × 10 cm3). It was dried over Na2SO4,
filtered and the chloroform removed under reduced pressure
to leave a residue which was recrystallized from cyclohexane.
Compound 5 was obtained as a white crystalline solid (0.98 g,
80%), mp 170.5–172 ЊC (Found: C, 67.75; H, 8.64. C18H27BO4
requires C, 67.94; H, 8.55%); δH (200 MHz; CDCl3; Me4Si) 7.82
(2H, d, J1,3 8.2, Ar–H), 7.51 (2H, d, J1,3 7.9, Ar–H), 5.41 (1H, s,
CH), 3.72 (4H, q, JAB 11.0, CH2), 1.35 (12H, s, CH3), 1.30 (3H,
s, CH3), 0.81 (3H, s, CH3).
5,5Ј-Bis[p-formylphenyl]-2,2Ј-bipyridine 7
Diacetal 6 (0.200 g, 0.37 mmol) was suspended in THF (70 cm3)
and 5% aq. HCl was added. The suspension was heated to 50 ЊC
and the resulting clear solution stirred for 15 h. The reaction
mixture was neutralized with 10% aq. Na2CO3 (24 cm3). The
precipitate was filtered off and dried under vacuum (0.132 g,
95%); δH (200 MHz; CF3CO2D; Me4Si) δH 9.47 (2H, d, J1,4 2.7,
α-H), 8.75 (2H, s, CHO), 8.35 (2H, d, J1,3 8.4, δ-H), 8.15 (2H,
dd, J1,3 8.1, J1,4 2.5, γ-H), 7.67 (4H, br d, J1,3 5.7, o-H or m-H),
7.33 (4H, br d, J1,3 5.7, m-H or o-H).
{5,5Ј-Bis[4-(5,5-dimethyl-1,3-dioxan-2-yl)phenyl]-2,2Ј-bi-
pyridine}bis(1,10-phenanthroline)ruthenium(II) hexafluoro-
phosphate [Ru(phen)26](PF6)2
A mixture of cis-dichloro bis(1,10-phenanthroline)ruthenium
(0.408 g, 0.766 mmol) and 6 (0.450 g, 0.84 mmol) was refluxed
in n-butanol (200 cm3) for 8 h under argon. The reaction mix-
ture was filtered to remove unreacted material and a saturated
aqueous solution of KPF6 (40 cm3) added to the orange filtrate.
The mixture was stirred overnight and the orange precipitate
filtered off, washed with water, diethyl ether and dried to give
[Ru(phen)26](PF6)2 as an orange solid (0.63 g, 71%) (Found:
C, 53.46; H, 3.94; N, 5.89. C58H52F12N6O4P2RuؒH2O requires:
C, 53.33; H, 4.17; N, 6.43%); δH (200 MHz; CD3CN; Me4Si):
8.67 (2H, dd, J1,4 1.2, J1,3 8.3, 4-H or 7-H), 8.63 (2H, d, J1,3 9.4,
δ-H), 8.58 (2H, dd, J1,4 1, J1,3 8.3, 7-H or 4-H), 8.37 (2H, dd,
J1,4 1.2, J1,3 5.3, 2-H or 9-H), 8.30 (2H, dd, J1,4 2.1, J1,3 8.4, γ-H),
8.25 (4H, dd, JAB 9.0, 5-H and 6-H), 7.98 (2H, dd, J1,4 1.2, J1,3
5.3, 9-H or 2-H), 7.83 (2H, dd, J1,3 5.4, J1,3 8.4, 3-H or 8-H),
5,5Ј-Bis[4-(5,5-dimethyl-1,3-dioxan-2-yl)phenyl]-2,2Ј-bipyridine
6
A mixture of 2 (1.00 g, 3.18 mmol), 5 (2.23 g, 7 mmol) and
[Pd(PPh3)4] (0.868 g) was set under vacuum for 4 h, and stored
under argon. Argon was bubbled through separate aliquots of
toluene (260 cm3) and 1 mol dmϪ3 aqueous Na2CO3 (260 cm3),
and the degassed solvents were added to the mixture via
cannula. The reaction was vigorously stirred and refluxed under
argon for 24 h. It was cooled to room temperature and a grey
precipitate filtered off. The solid was dissolved in CHCl3,
filtered and passed through a short column of silica gel, eluting
with CHCl3. The resulting pale-yellow solid was washed with
J. Chem. Soc., Perkin Trans. 1, 2002, 1226–1231
1229

View Article Online
7.79 (2H, d, J1,4 2.3, α-H), 7.61 (2H, dd, J1,3 5.2, J1,3 8.2, 8-H or
3-H), 7.46 (4H, d, J1,3 8.3, m-H), 7.27 (4H, d, J1,3 8.4, o-H), 5.40
(2H, s, CH), 3.67 (8H, dd, JAB 11, CH2), 1.21 (6H, s, CH3), 0.78
(6H, s, CH3).
[11](PF6)2. [8](PF6)2 (7.37 mg, 0.0026 mmol) was dissolved in
chloroform (4 cm3) under argon. A solution of Zn(OAc)2ؒ2H2O
(1 cm3, 7.94 × 10Ϫ6 mol) in methanol was added. The reaction
mixture was refluxed for 1.5 h. The resulting solution was
diluted with water (10 cm3) and shaken with a saturated
aqueous solution of NaHCO3 (10 cm3). The organic layer was
washed twice with water, concentrated to 10 cm3 and treated
with a 5% aqueous solution of KPF6 (10 cm3) for 4 h. The
organic layer was separated, washed 3 times with water, and the
solvent removed under reduced pressure leaving [11](PF6)2 as a
red solid (6.10 mg, 79%); λmax(CH2Cl2)/nm 265 (ε/dm3 molϪ1
cmϪ1 58000), 414 (521000), 540 (28400), 574 (14200); δH (400
MHz; CD2Cl2; Me4Si): 10.202 (4H, s, meso-H), 8.80 (2H, br d,
J1,3 8, δ-H), 8.793 (2H, dd, J1,3 8.28, J1,4 1.12, 7-H), 8.680 (2H,
dd, J1,3 5.26, J1,4 1.19, 9-H), 8.67 (2H, br dd, J1,3 8, γ-H), 8.553
(2H, dd, J1,3 8.35, J1,4 1.06, 4-H), 8.343 (2H, d, J1,3 8.97, 6-H),
8.234 (2H, d, J1,3 8.98, 5-H), 8.225 (2H, dd, J1,3 5.25, J1,4 1.19,
2-H), 8.162 (2H, s, α-H), 8.150 (2H, d, J1,3 8.27, J1,3 5.33, 8-H),
8.111 (4H, d, J1,3 7.99, m-H), 7.929 (4H, d, J1,4 1.83, op-H),
7.869 (2H, t, J1,4 1.83, pp-H), 7.801 (2H, dd, J1,3 8.28, J1,3 5.33,
3-H), 7.634 (4H, d, J1,3 8.13, o-H), 3.981 (16H, quint, αp-H and
αd-H), 2.468 (12H, s, CH3d), 2.375 (12H, s, CH3p), 2.195 (16H,
sept, βp-H and βd-H), 1.777 (16H, quint, γp-H and γd-H), 1.526
(36H, s, CH3), 1.526 (16H, m, δp-H and δd-H), 1.402 (16H,
m, εp-H and εd-H), 0.943 (12H, t, J1,3 7.29, ξp-H or ξd-H),
0.931 (12H, t, J1,3 7.29, ξd-H or ξp-H); m/z (FAB) 2818.7
([M2ϩ ϩ PF6Ϫ]ϩ, 6.0%), 2675.0 ([M2ϩ ϩ eϪ]ϩ, 5.4), 1409.8
[5,5Ј-Bis(4-formylphenyl)-2,2Ј-bipyridine]bis(1,10-phenanthro-
line)ruthenium(II) hexafluorophosphate [Ru(phen)27](PF6)2
[Ru(phen)26](PF6)2 was dissolved in THF (230 cm3) and 5%
aqueous HCl (58 cm3), and the reaction mixture stirred at 50 ЊC
for 24 h. A saturated aqueous solution of KPF6 (16 cm3) was
added, followed by water (77 cm3). The THF was removed
under reduced pressure. The orange precipitate was filtered off,
washed with water, ethanol and diethyl ether, and dried to give
[Ru(phen)27](PF6)2 as a dark orange solid (0.411 g, 89%), mp
>260 ЊC (dec.) (Found: C, 51.98; H, 2.83; N, 7.16. C48H32F12-
N6O2P2Ru requires C, 51.67; H, 2.89; N, 7.53%); δH (200 MHz;
CD3CN; Me4Si): 10.0 (2H, s, CHO), 8.69 (2H, d, J1,3 8.6,
δ-H), 8.68 (2H, dd, J1,4 1.2, J1,3 8.1, 4-H or 7-H), 8.57 (2H, dd,
J1,4 1.2, J1,3 8.4, 7-H or 4-H), 8.38 (2H, dd, J1,4 1.2, J1,3 5.2, 2-H
or 9-H), 8.37 (2H, dd, J1,4 2, J1,3 8.5, γ-H), 8.25 (4H, dd, JAB 8.7,
5-H and 6-H), 7.95 (2H, dd, J1,4 1.2, J1,3 4.8, 9-H or 2-H),
7.88 (2H, d, J1,4 4.4, α-H), 7.88 (4H, d, J1,3 8.4, m-H), 7.84 (2H,
dd, J1,3 5.3, J1,3 8.2, 3-H or 8-H), 7.60 (2H, dd, J1,3 5.3, J1,3 8.2,
8-H or 3-H), 7.48 (4H, d, J1,3 8.1, o-H); m/z (FAB) 971.2
([M Ϫ PF6Ϫ]ϩ).
Ϫ
([M2ϩ ϩ PF6 ϩ Hϩ]2ϩ/2, 1.9), 1337.8 ([M2ϩ]/2, 4.5), 462.1
[8](PF6)2. [Ru(phen)27](PF6)2 (94.5 mg, 0.0846 mmol),
3,5-di-tert-butylbenzaldehyde 9 (174.7 mg, 0.689 mmol) and
3,3Ј-dihexyl-4,4Ј-dimethyl-2,2Ј-methylenedipyrrole 10 (343 mg,
1 mmol) were dissolved in dichloromethane under argon.
Trifluoroacetic acid (3 drops) was added and the reaction mix-
ture stirred at room temperature overnight. Tetrachloro-p-
benzoquinone (0.656 g, 2.67 mmol) was added and the reaction
mixture refluxed for 2 h. After cooling to room temperature, it
was neutralized with 10% aqueous Na2CO3. The organic phase
was separated, washed with water (2 × 200 cm3), and stirred
with a 5% aqueous solution of KPF6 (100 cm3) overnight. After
separation, it was washed with water (2 × 200 cm3) and the
solvent removed under reduced pressure. The crude product
was chromatographed on alumina. Elution with CH2Cl2–
CH3OH (1.3–1.5%) afforded 0.0322 g of impure [8](PF6)2;
elution with CH2Cl2– CH3OH (2.5–5%) afforded 0.0402 g
of impure [12](PF6)2. These fractions were further purified by
repeated column chromatography on alumina, eluting with
CH2Cl2–CH3OH. Porphyrin [12](PF6)2 (see below) was isolated
as an orange material after preparative TLC (alumina, CH2Cl2–
CH3OH (0.5–1.5%)) (3.20 mg, 2%). Bis-porphyrin [8](PF6)2 was
obtained as a dark orange solid (17.74 mg, 7.4%); λmax(CH2Cl2)/
nm 265 (ε/dm3 molϪ1cmϪ1 59000), 412 (419000), 508 (25600),
540 (14600), 574 (13000) and 627 (1900); δH (400 MHz; CD2Cl2;
Me4Si): 10.273 (4H, s, meso-H), 8.762 (2H, dd, J1,3 8.34,
J1,4 1.20, 7-H), 8.693 (2H, d, J1,3 8.43, δ-H), 8.649 (2H, dd, J1,3
5.23, J1,4 1.20, 9-H), 8.602 (2H, dd, J1,3 8.35, J1,4 1.93, γ-H),
8.522 (2H, dd, J1,3 8.34, J1,4 1.01, 4-H), 8.288 (2H, d, J1,3 8.80,
6-H), 8.199 (2H, dd, J1,3 5.31, J1,4 1.28, 2-H), 8.179 (2H, d, J1,3
9.72, 5-H), 8.152 (br s, 2H, α-H), 8.135 (2H, dd, J1,3 8.25, J1,3
5.32, 8-H), 8.116 (4H, d, J1,3 8.25, m-H), 7.932 (4H, d, J1,4 1.83,
op-H), 7.870 (2H, t, J1,4 1.83, pp-H), 7.785 (2H, dd, J1,3 8.25, J1,3
5.32, 3-H), 7.634 (4H, d, J1,3 8.25, o-H), 4.010 (16H, br m, αp-H
and αd-H), 2.503 (12H, s, CH3d), 2.427 (12H, s, CH3p), 2.221
(16H, sext, βp-H and βd-H), 1.782 (16H, quintet, γp-H and γd-
H), 1.522 (36H, s, CH3), 1.522 (16H, m, δp-H and δd-H), 1.405
(16H, quartet, εp-H and εd-H), 0.937 (12H, t, J1,3 7.33, ξp-H or
ξd-H), 0.929 (12H, t, J1,3 7.33, ξd-H or ξp-H), Ϫ2.445 (4H, br s,
NH); m/z (FAB) 2839.6 ([M2ϩ ϩ 2PF6Ϫ ϩ Hϩ]ϩ, 0.8%), 2693.6
([Ru(phen)22ϩ ϩ eϪ]ϩ, 100).
[12](PF6)2. For isolation, see preparation of bis-porphyrin
[8](PF6)2; δH (400 MHz; CD2Cl2; Me4Si): 10.250 (2H, s, meso-
H), 10.013 (1H, s, CHO), 8.710 (1H, d, hidden, J1,3 8.25, δЈ-H),
8.708 (1H, dd, J1,3 8.43, J1,4 1.29, 7-H or 7Ј-H), 8.684 (1H, dd,
J1,3 8.43, J1,4 1.28, 7Ј-H or 7-H), 8.653 (1H, d, J1,3 8.62, δ-H),
8.608 (1H, dd, J1,3 8.44, J1,4 2.02, γЈ-H), 8.546 (1H, dd, J1,3 5.04,
J1,4 1.19, 9-H), 8.533 (1H, dd, J1,3 5.04, J1,4 1.19, 9Ј-H), 8.517
(1H, dd, J1,3 8.07, J1,4 1.47, 4-H or 4Ј-H), 8.513 (1H, dd, J1,3
8.35, J1,4 1.38, 4Ј-H or 4-H), 8.315 (1H, dd, J1,3 8.07, J1,4 1.84,
γ-H), 8.289 (2H, d, J1,3 8.81, 6-H or 6Ј-H), 8.237 (1H, d, J1,3
8.99, 6Ј-H or 6-H), 8.192 (1H, d, J1,3 8.99, 5-H or 5Ј-H), 8.173
(1H, d, J1,3 8.98, 5Ј-H or 5-H), 8.134 (1H, dd, J1,3 5.32, J1,4 1.29,
2-H), 8.100 (1H, dd, J1,3 6.61, J1,4 1.29, 2Ј-H), 8.084 (1H, br s,
αЈ-H), 8.087 (2H, d, J1,3 7.70, mЈ-H), 8.059 (1H, dd, J1,3 8.72, J1,3
5.60, 8-H or 8Ј-H), 8.051 (1H, dd, J1,3 5.32, J1,3 8.44, 8Ј-H or
8-H), 7.913 (2H, d, J1,4 1.84, op-H), 7.900 (1H, s, α-H), 7.895
(2H, m, J1,3 8.44, m-H), 7.859 (1H, t, J1,4 1.83, pp-H), 7.752 (1H,
dd, J1,3 8.53, J1,3 5.23, 3-H or 3Ј-H), 7.744 (1H, dd, J1,3 8.35, J1,3
5.04, 3Ј-H or 3-H), 7.593 (2H, d, J1,3 8.44, oЈ-H), 7.491 (2H, d,
J1,3 8.07, o-H), 3.989 (8H, quartet, αp-H and αd-H), 2.486 (6H, s,
CH3d), 2.389 (6H, s, CH3p), 2.190 (8H, sext, βp-H and βd-H),
1.762 (8H, sext, γp-H and γd-H), 1.518 (18H, s, CH3), 1.518 (8H,
m, δp-H and δd-H), 1.386 (8H, quartet, εp-H and εd-H), 0.916
(6H, t, J1,3 7.25, ξp-H or ξd-H), 0.913 (6H, t, J1,3 7.25, ξd-H or ξp-
H), Ϫ2.477 (2H, br s, NH); m/z (FAB) 1832.5 ([M2ϩ ϩ PF6Ϫ]ϩ,
12%), 1687.2 ([M2ϩ ϩ eϪ]ϩ, 17), 843.8 ([M2ϩ]/2, 11), 462.1
([Ru(phen)22ϩ ϩ eϪ]ϩ, 100).
Acknowledgements
We thank Raymond Hueber for the FAB mass spectra, and
Jean-Daniel Sauer and Michelle Martigneaux for the high-field
NMR spectra. J. I. B. and P. K. thank the European Com-
munity for postdoctoral fellowship (TMR contract nЊ FMRX-
CT96–0031) and Erasmus studentship, respectively.
References
([M2ϩ ϩ PF6Ϫ]ϩ, 5), 2547.7 ([M2ϩ ϩ eϪ]ϩ, 4.6), 1346.3 ([M2ϩ
ϩ
1 (a) J. Deisenhofer and H. Michel, Angew. Chem., Int. Ed. Engl.,
1989, 28, 829–847; (b) R. Huber, Angew. Chem., Int. Ed. Engl., 1989,
28, 848–869.
Ϫ
2ϩ
PF6 ϩ Hϩ]2ϩ/2, 2.3), 1273.8 ([M2ϩ]/2, 4), 462 ([Ru(phen)2
ϩ
eϪ]ϩ, 100).
1230
J. Chem. Soc., Perkin Trans. 1, 2002, 1226–1231

View Article Online
2 (a) S. Chardon-Noblat and J.-P. Sauvage, Tetrahedron, 1991,
47, 5123–5132; (b) C. Pascard, J. Guilhem, S. Chardon-Noblat and
J.-P. Sauvage, New J. Chem., 1993, 17, 331–335.
9 (a) R. J. Donohoe, C. D. Tait, M. K. DeArmond and D. W. Wertz,
J. Phys. Chem., 1986, 90, 3923–3926; (b) R. J. Donohoe, C. D. Tait,
M. K. DeArmond and D. W. Wertz, Spectrochim. Acta, 1986, 42A,
233–240.
3 (a) V. Heitz, S. Chardon-Noblat and J.-P. Sauvage, Tetrahedron
Lett., 1991, 32, 197–198; (b) A. M. Brun, A. Harriman, V. Heitz and
J.-P. Sauvage, J. Am. Chem. Soc., 1991, 113, 8657–8663; (c) A. M.
Brun, S. J. Atherton, A. Harriman, V. Heitz and J.-P. Sauvage, J. Am.
Chem. Soc., 1992, 114, 4632–4639; (d ) A. M. Brun, S. J. Atherton,
A. Harriman, V. Heitz and J.-P. Sauvage, J. Am. Chem. Soc., 1993,
115, 6109–6114; (e) J.-C. Chambron, A. Harriman, V. Heitz and
J.-P. Sauvage, J. Am. Chem. Soc., 1993, 115, 6109–6114.
10 J. R. Nitschke, S. Zürcher and T. D. Tilley, J. Am. Chem. Soc., 2000,
122, 10345–10352.
11 (a) W. Frank, M. Wasgindt, T. Pautzsch and E. Klemm, Macromol.
Chem. Phys., 2001, 202, 980–984; (b) W. Frank, T. Pautzsch and
E. Klemm, Macromol. Chem. Phys., 2001, 202, 2535–2537.
12 N. Miyaura and A. Suzuki, Chem. Rev., 1995, 95, 2457–2483 and
references therein.
4 (a) G. Hungerford, M. Van der Auweraer, J.-C. Chambron, V. Heitz,
J.-P. Sauvage, J.-L. Pierre and D. Zurita, Chem. Eur. J., 1999,
5, 2089–2100; (b) J. L. Allwood, A. K. Burrell, D. L. Officer,
S. M. Scott, K. Y. Wild and K. C. Gordon, Chem. Commun., 2000,
747–748; (c) F. Odobel, F. Suzenet, E. Blart and J.-P. Quintard, Org.
Letters, 2000, 2, 131–133.
5 (a) J.-P. Collin, V. Heitz and J.-P. Sauvage, Tetrahedron Lett., 1991,
32, 5977–5980; (b) J.-P. Collin, A. Harriman, V. Heitz, F. Odobel
and J.-P. Sauvage, J. Am. Chem. Soc., 1994, 116, 5679–5690;
(c) A. Harriman, F. Odobel and J.-P. Sauvage, J. Am. Chem. Soc.,
1995, 117, 9461–9472; (d ) L. Flamigni, F. Barigelletti, N. Armaroli,
J.-P. Collin, J.-P. Sauvage and J. A. G. Williams, Chem. Eur. J., 1998,
4, 1744–1754; (e) I. M. Dixon, J.-P. Collin, J.-P. Sauvage,
F. Barigelletti and L. Flamigni, Angew. Chem. Int. Ed., 2000, 39,
1292–1295; ( f ) I. M. Dixon, J.-P. Collin, J.-P. Sauvage and
L. Flamigni, Inorg. Chem., 2001, 40, 5507–5517.
13 F. H. Case, J. Am. Chem. Soc., 1946, 68, 2574–2576.
14 C. P. Whittle, J. Heterocycl. Chem., 1977, 14, 191–194.
15 (a) G. Morgan and F. H. Burstall, J. Chem. Soc., 1937, 1649–1672;
(b) F. M. Romero and R. Ziessel, Tetrahedron Lett., 1995, 36,
6471–6474.
16 A. Torrado and B. Imperiali, J. Org. Chem., 1996, 61,
8940–8948.
17 C. Coudret, Synth. Commun., 1996, 26, 3540–3542.
18 (a) J. S. Lindsey, H. C. Hsu and I. C. Schreiman, Tetrahedron Lett.,
1986, 27, 4969–4970; (b) J. S. Lindsey, I. C. Schreiman, H. C. Hsu,
P. C. Kearney and A. M. Marguerettaz, J. Org. Chem., 1987, 52,
827–836; (c) J. S. Lindsey and R. W. Wagner, J. Org. Chem., 1989, 54,
828–836.
19 S. Chardon-Noblat and J.-P. Sauvage, Tetrahedron, 1991, 47,
5123–5132.
20 M. Andersson, M. Linke, J.-C. Chambron, J. Davidsson, V. Heitz,
L. Hammarström and J.-P. Sauvage, J. Am. Chem. Soc., 2002, 124,
4347–4362.
21 (a) A. Osuka, K. Maruyama, N. Mataga, T. Asahi, I. Yamasaki and
N. Tamai, J. Am. Chem. Soc., 1990, 112, 4958–4959; (b) A. Helms,
D. Heiler and G. McLendon, J. Am. Chem. Soc., 1992, 114,
6227–6238.
6 (a) M. J. Crossley, P. L. Burn, S. J. Langford and J. K. Prashar,
J. Chem. Soc., Chem. Commun., 1995, 1921–1923; (b) T. A. Vannelli
and T. B. Karpishin, Inorg. Chem., 1999, 38, 2246–2247; (c) T. A.
Vannelli and T. B. Karpishin, Inorg. Chem., 2000, 39, 340–347.
7 M.-J. Blanco, J.-C. Chambron, V. Heitz and J.-P. Sauvage, Org. Lett.,
2000, 2, 3051–3054.
8 (a) A. D. Hamilton, H.-D. Rubin and A. B. Bocarsly, J. Am. Chem.
Soc., 1984, 106, 7255–7257; (b) D. LeGourriérec, M. Andersson,
J. Davidsson, E. Mukhtar, L. Sun and L. Hammarström, J. Phys.
Chem. (A), 1999, 103, 557–559.
22 N. Solladié, J.-C. Chambron and J.-P. Sauvage, J. Am. Chem. Soc.,
1999, 121, 3684–3692.
23 B. P. Sullivan, D. J. Salmon and T. J. Meyer, Inorg. Chem., 1978, 17,
3334–3341.
J. Chem. Soc., Perkin Trans. 1, 2002, 1226–1231
1231