The Electrochemically-Driven Decomplexation/Recomplexation of Inclusion Adducts of Ferrocene Derivatives with an Electron-Accepting Receptor

Article abstract of DOI:10.1021/jo991467z

The tetracationic cyclophane, cyclobis(paraquat-4,4′-biphenylene), binds 1,1′-disubstituted ferrocene-based polyethers as a result of (i) [π...π] stacking between the π-electron-deficient bipyridinium units and the π-electron-rich cyclopentadienyl rings and (ii) [C-H...O] hydrogen bonds between the α-bipyridinium hydrogen atoms and the polyether oxygen atoms. However, even the presence of a bulky tetraarylmethane group-which is too large to thread through the cavity of the cyclophane host-at the end of each of the two polyether substituents of the ferrocene-containing guest does not discourage adduct formation of the inclusion type. Thus, in these adducts, the ferrocene unit of the guest is located inside the cavity of the host with its two polyether chains protruding outward from the same side of the host. The alternative pseudorotaxane geometry is not observed in solutions of these 1:1 adducts. The host-guest adducts display absorption bands in the visible spectral region, characteristic of charge-transfer interactions. In the case of one of these adducts, reversible decomplexation/recomplexation takes place upon electrochemical oxidation/reduction of the ferrocene-based unit or upon reduction/oxidation of the tetracationic cyclophane.

Full text of DOI:10.1021/jo991467z

J . Org. Chem. 2000, 65, 1947-1956
1947
Th e Electr och em ica lly-Dr iven Decom p lexa tion /Recom p lexa tion of
In clu sion Ad d u cts of F er r ocen e Der iva tives w ith a n
Electr on -Accep tin g Recep tor †
Vincenzo Balzani,*,‡ J an Becher,*,§ Alberto Credi,‡ Mogens B. Nielsen,§,|
Franc¸isco M. Raymo,|, J . Fraser Stoddart,*,| Anna Maria Talarico,‡ and
Margherita Venturi*,‡
Dipartimento di Chimica “G. Ciamician”, Universita` di Bologna, via Selmi 2, Bologna, I-40126, Italy,
Department of Chemistry, Odense University, Campusvej 55, Odense M, DK-5230, Denmark, and
Department of Chemistry and Biochemistry, University of California, Los Angeles, 405 Hilgard Avenue,
Los Angeles, California 90095-1569
Received September 15, 1999
The tetracationic cyclophane, cyclobis(paraquat-4,4′-biphenylene), binds 1,1′-disubstituted ferrocene-
based polyethers as a result of (i) [π...π] stacking between the π-electron-deficient bipyridinium
units and the π-electron-rich cyclopentadienyl rings and (ii) [C-H...O] hydrogen bonds between
the R-bipyridinium hydrogen atoms and the polyether oxygen atoms. However, even the presence
of a bulky tetraarylmethane groupswhich is too large to thread through the cavity of the cyclophane
hostsat the end of each of the two polyether substituents of the ferrocene-containing guest does
not discourage adduct formation of the inclusion type. Thus, in these adducts, the ferrocene unit
of the guest is located inside the cavity of the host with its two polyether chains protruding outward
from the same side of the host. The alternative pseudorotaxane geometry is not observed in solutions
of these 1:1 adducts. The host-guest adducts display absorption bands in the visible spectral region,
characteristic of charge-transfer interactions. In the case of one of these adducts, reversible
decomplexation/recomplexation takes place upon electrochemical oxidation/reduction of the fer-
rocene-based unit or upon reduction/oxidation of the tetracationic cyclophane.
In tr od u ction
The tetracationic cyclophane, cyclobis(paraquat-4,4′-
biphenylene) (14+), can be synthesized1 from its acyclic
precursors in a reasonable yield (32%) when a ferrocene-
based polyether is employed as the template. It is
known1,2 that this tetracationic cyclophane binds (Figure
1) ferrocene (2) as a result of [π...π] stacking interactions
between the π-electron-deficient bipyridinium units and
the π-electron-rich cyclopentadienyl rings. Upon the
introduction of one polyether chain onto each of the
cyclopentadienyl rings of ferrocene (2), as in the case of
the derivative 3, the stability of the resulting second
sphere adduct3 increases1 drammatically as a resultsit
is believedsof additional [C-H...O] hydrogen bonds that
* To whom correspondence should be addressed. (J .F.S.) Fax:(310)
206-1843. E-mail: stoddart@chem.ucla.edu.
† “Molecular Meccano”. 58. For part 57, see: Ashton, P. R.; Baldoni,
V.; Balzani, V.; Claessens, C. G.; Credi, A.; Hoffmann, H. D. A.; Raymo,
F. M.; Stoddart, J . F.; Venturi, M.; White, A. J . P.; Williams, D. J .
Eur. J . Org. Chem. 2000, in press.
‡Universita` di Bologna.
§ Odense University.
| University of California, Los Angeles.
Current address: Center for Supramolecular Science, Department
of Chemistry, University of Miami, 1301 Memorial Drive, Coral Gables,
FL 33124-0431.
F igu r e 1. Adduct [1:2]4+ and the two co-conformations (A and
B) for the adduct [1:3]4+
.
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Eur. J . 1997, 3, 1136-1150.
are formed between the R-bipyridinium hydrogen atoms
and some of the polyether oxygen atoms. However, since
the rotation of one cyclopentadienyl ring with respect to
the other is possible in solution, two different 1:1 adducts
(A and B) can, in principle, be formed when a 1,1′-
disubstituted ferrocene derivative, such as 3, is bound
as a guest inside the host 14+. In both these 1:1 adducts,
the ferrocene unit in the guest is located inside the cavity
of the host with, in one case, its two substituents
10.1021/jo991467z CCC: $19.00 © 2000 American Chemical Society
Published on Web 03/10/2000

1948 J . Org. Chem., Vol. 65, No. 7, 2000
Balzani et al.
Sch em e 1. Syn th esis of th e Du m bbell-Sh a p ed
Com p ou n d 9 In cor p or a tin g On e F er r ocen e Un it
protruding outward in hairpin-like fashion from the same
(A) and, in the other case, from opposite (B) sides of the
host. Only in co-conformation4 B would the covalent
attachment of bulky groups to the ends of the polyether
chains of the guest bond together mechanically the cyclic
and the acyclic components, affording a [2]rotaxane. In
light of these considerations, we envisaged the possibility
of designing and constructing ferrocene-based rotaxanes5
with the ultimate goal of generating electrochemically
controllable molecular shuttles.6,7 Here, we report (i) the
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synthesis of four ferrocene-containing acyclic polyethers,
(ii) the complexation of their hairpin-like forms (A)
exclusively by cyclobis(paraquat-4,4′-biphenylene) (14+),
(iii) the absorption characteristics of the adducts, and (iv)
the reversible decomplexation/recomplexation of one of
the adducts, both upon oxidation/reduction of the fer-
rocene-based unit in the guest and upon reduction/
oxidation of the bipyridinium units in the host.
Resu lts a n d Discu ssion
Syn th esis. The 1,1′-disubstituted ferrocene derivative
3 templates1 the formation of 14+ from its acyclic precur-
sors in a yield of 32%. To construct a [2]rotaxane, we
envisaged the possibility of modifying the template 3 by
attaching bulky tetraarylmethane-based stoppers to the
ends of each of the two polyether chains. Alkylation of 4
with 5 afforded (Scheme 1) the ester 6, which was
hydrolyzed to give the acid 7, which was then converted
into the acid chloride 8. Esterification of 3 with 8 afforded
the dumbbell-shaped compound 9, which incorporates a
ferrocene recognition site and two bulky stoppers. When
this reaction was repeated in the presence of the pre-
formed cyclophane 14+, only trace amounts of the ex-
pected [2]rotaxane were obtained.8 Similarly, when 9 was
employed as a template in the macrocyclization of 14+
from its acyclic precursors, extremely small quantities
(<1%) of the expected [2]rotaxane were detected.8 These
unexpected results were ascribed initially to the relative
ease of decomposition of the ferrocene templates 3 and
9. Reduction of the π-electron-rich character of the
(8) A solution of 9 (275 mg, 0.18 mmol), 13‚2PF6 (202 mg, 0.26
mmol), and 14 (89 mg, 0.26 mmol) in MeCN (10 mL) was stirred for
10 d at ambient temperature. The solvent was distilled off under
reduced pressure and the residue washed with CHCl3 (25 mL). The
resulting solid was dissolved in a mixture of Me2CO and H2O (500 mL,
1: 1 v/v), and NH4PF6 was added as
a solid. The solution was
concentrated under reduced pressure, and the resulting precipitate was
filtered off and purified by column chromatography [SiO2: MeOH/2
M NH4Cl/MeNO2 (7:2:1)] to afford traces (<1%) of the [2]rotaxane in
addition to quantities of 1‚4PF6 after counterion exchange. The [2]-
rotaxane could only be characterized by liquid secondary ion mass
spectrometry (LSIMS), which showed peaks at m/z values of 2828,
2679, and 2534 for [M]+, [M - PF6]+, and [M - 2PF6]+, respectively,
corresponding to the molecular ion and to the losses of one and two
hexafluorophosphate counterions, respectively.

Decomplexation of Inclusion Adducts of Ferrocene
J . Org. Chem., Vol. 65, No. 7, 2000 1949
ployed,1 indicating that a reduction of the π-electron-rich
character of the template does not affect significantly the
efficiency of this template-directed synthesis. These
observations suggested the synthesis of the templates 18
and 21, each incorporating one ferrocene recognition site
and two tetraarylmethane-based stoppers. Compound 18
was obtained (Scheme 4) after the alkylation of 4 with
15, followed by tosylation and reaction of the tosylate
with 11. Similarly, compound 21 was prepared (Scheme
5) after the alkylation of 4 with an excess of 19, followed
by tosylation and reaction of the tosylate with 11.
However, when 18 was used to template the macrocy-
clization of 132+ and 14, the expected [2]rotaxane was
not even detected.9 Instead, the free tetracationic cyclo-
phane 1‚4PF6, in 2% yield only, and the unchanged
template 18 were isolated from the reaction mixtures.
Sch em e 2. Syn th esis of th e F er r ocen e-Ba sed
P olyeth er 12
Sch em e 4. Syn th esis of th e Du m bbell-Sh a p ed
Com p ou n d 18 In cor p or a tin g On e F er r ocen e Un it
Sch em e 3. Tem p la te-Dir ected Syn th esis of 1‚4P F 6
These unexpected results can be explained in two
alternative ways. Either (i) the [2]rotaxanes are formed
but the macrocyclic component can dethread because the
stoppers are not large enough or (ii) the complexation of
1,1′-disubstituted ferrocene derivatives by 14+ occurs as
illustrated for co-conformation A in Figure 1. It is known1
that 14+ binds 1,4-dioxybenzene-based guests inside its
cavity and that a reddish-orange color appears im-
mediately when the preformed 14+ cyclophane is mixed
with guests of this kind. Thus, to verify if the tris(4-tert-
butylphenyl)methyl groups are large enough to act as
stoppers toward the cyclophane 14+, the 1,4-dioxyben-
zene-based dumbbell-shaped compound 23 was synthe-
sized (Scheme 6) by reacting 17 with 22. It transpired
that, when 1‚4PF6 and 23 were mixed in MeCN at room
temperature, no color change was observed, indicating
that threading of 23 through the cavity of 14+ does not
occur. By contrast, when either of the ferrocene-based
cyclopentadienyl rings by the insertion of a methylene
group between them and their polyether substituents was
expected to increase the stabilities of the templates.
Indeed, reaction of 10 with 11 afforded (Scheme 2) the
stable compound 12 in a yield of 77%. This compound
was employed (Scheme 3) to template the formation of
(9) The attempted template-directed synthesis of the [2]rotaxane
was carried out by stirring a solution of 13‚2PF6, 14, and 18 (3:3:1) in
DMF at ambient temperature for 10 days. DMF was chosen as the
solvent because 18 is not soluble in MeCN. No evidence was obtained
for the formation of any [2]rotaxane. However, 1‚4PF6 was isolated in
a yield of 2% (based on the molar amounts of 13‚2PF6 and 14). The
template-directed synthesis of the tetracationic cyclophane 1‚4PF6 was
never performed using either 11 or 21 as templates. The former was
not expected to be an efficient template, and the latter was not
available in sufficient quantities.
1
4+ from its precursors 13‚2PF6 and 14. The tetracationic
cyclophane was isolated as its hexafluorophosphate salt
(1‚4PF6) in a yield of 32% after precipitation with an
excess of NH4PF6. Interestingly, this yield is exactly the
same as that obtained when the template 3 was em-

1950 J . Org. Chem., Vol. 65, No. 7, 2000
Balzani et al.
Sch em e 5. Syn th esis of th e Du m bbell-Sh a p ed
Com p ou n d 21 In cor p or a tin g On e F er r ocen e Un it
a n d Tw o Hyd r oqu in on e Rin gs
F igu r e 2. 1H NMR spectra (c ) 0.01 mol L-1, 300 K) of (a) 12
recorded in CDCl3 and of (b) 1‚4PF6 and (c) an equimolar
mixture of them recorded in CD3CN.
1
components. As an example, the H NMR spectra of the
free guest 12 (recorded in CDCl3) and of the free host
1‚4PF6 and an equimolar mixture of guest and host
recorded in CD3CN (0.01 mol L-1) at 300 K are illustrated
in Figure 2. The largest chemical shift change is observed
for the signals associated with the cyclopentadienyl ring
protons, which move by ca. ∆δ -1.5 ppm on complexation
as a result of the shielding effects exerted upon them by
the bipyridinium and biphenylene units. The signals
associated with the â-bipyridinium protons also move
significantly (∆δ ca. -0.2 ppm), and their chemical shift
changes were exploited to determine (Table 1) the as-
compounds, 18 or 21, were mixed with 1‚4PF6 in DMF,
a green color (vide infra), characteristic1 of charge-
transfer interactions between the cyclopentadienyl rings
and the bipyridinium units, appeared immediately in
keeping with the formation of an adduct. Since the tris-
(4-tert-butylphenyl)methyl groups are too large to thread
through the cavity of the cyclophane, the adducts formed
between 14+ and either 18 or 21 must be similar to As
i.e., the two substituents of the guest protrude outside
the cavity of the host from the same side.
Ta ble 1. Associa tion Con sta n tsa a n d Der ived F r ee
En er gies of Associa tion for th e 1:1 Ad d u cts F or m ed
betw een 14+ a n d 2, 3, 11, 12, 18, or 21 in Solu tion a t 300 K
Sch em e 6. Syn th esis of th e Du m bbell-Sh a p ed
Com p ou n d 23 In cor p or a tin g On e Hyd r oqu in on e
Rin g
guest
Ka (L mol-1
)
-∆G° (kcal mol-1
)
solvent
CD3CN
CD3CN
CD3CN
2
3
11
12
80b
1600b
160
3900
290
2.6
4.3
3.0
4.9
3.4
3.2
3.2
CD3CN
(CD3)2NCDO
(CD3)2NCDO
(CD3)2NCDO
18
21
230
230
a
Determined by 1H NMR spectroscopy using the dilution
b
method. See ref 1.
sociation constants (Ka) for 1:1 adducts formed between
1‚4PF6 and the ferrocene derivatives 11 and 12 using the
dilution method.10 As observed previously1 for ferrocene
(2), the Ka value measured for 11 in CD3CN is relatively
low. However, introduction of polyether chainssas in the
ferrocene derivatives 3 and 12sreinforces1 the intra-
adduct noncovalent bonding interactions (presumably in
the form of [C-H‚‚‚O] hydrogen bonds between the
1
1H NMR Sp ectr oscop y. The H NMR spectroscopic
analyses of the adducts revealed significant chemical
shift changes relative to the separate host and guest
(10) Connors, K. A. Binding Constants; Wiley: New York, NY, 1987.

Decomplexation of Inclusion Adducts of Ferrocene
J . Org. Chem., Vol. 65, No. 7, 2000 1951
Ta ble 2. 1H NMR Ch em ica l Sh ift Ch a n ges (∆δ)
Exp er ien ced by P r oton s in 14+ u p on Ad d u ct F or m a tion a
w ith th e F er r ocen e Der iva tives 12, 18, a n d 21 in
(CD3)2NCDO a t 300 K
protons. However, specific assignments to these protons
could not be made. At 224 K, the exchange between host
and guest on the H NMR time scale (400 MHz) was still
1
fast, indicating the formation of a rather “loose” 1:1
adduct in which the ferrocene nucleus of 21 is bound
within the cavity of 14+ in an A-type co-conformation that
still permits the hydroquinone rings in the guest to
interact with the outside surfaces of the bipyridinium
rings of the host in a donor-acceptor fashion. The fact
that the hydroquinone ring protons are shifted even
further upfield to δ 6.43 and 6.57 in the 224 K spectrum
would not be in conflict with this hypothesis. In sum-
∆δ
b
b
b
b
b
1:1 adduct
HR
Hâ
Hγ
Hδ
Hꢀ
[1:12]4+
[1:18]4+
-0.10
-0.08
-0.10
-0.21
-0.15
-0.18
+0.02
+0.01
+0.02
+0.06
+0.04
+0.05
-0.04
-0.04
-0.04
[1:21]4+
[1‚4PF6] ) [ferrocene derivative] ) 0.01 mol L-1
.
See Figure
a
b
2.
1
mary, all the H NMR spectroscopic evidence indicates
that all the ferrocene derivatives we have investigated
so far in solution form 1:1 adducts with the tetracationic
cyclophane 14+ using co-conformations of the type As
and never of the type B.
Absor p tion a n d Lu m in escen ce P r op er ties. We
have investigated the absorption and luminescence prop-
erties of the cyclophane 14+, the ferrocene derivative 12,
and their [1:12]4+ adduct in MeCN at room temperature.
The absorption spectrum of 14+ in MeCN shows (Figure
4) a very intense band with λmax ) 260 nm (ꢀ ) 83 000 L
mol-1 cm-1), expected on the basis of the chromophoric
units contained in the cyclophane, namely, biphenyl11 and
4,4′-bipyridinium12 groups, and a weak band with λmax
) 340 nm (ꢀ ) 3000 L mol-1 cm-1) that may arise from
a charge-transfer interaction between the biphenyl and
bipyridinium units.13 The absorption spectrum of 12
(Figure 4) displays the two well-known bands of the
ferrocene nucleus (λmax ) 323 and 435 nm, ꢀ ) 100 and
115 L mol-1 cm-1, respectively).14 These bands have the
same λmax as those of unsubstituted ferrocene, but are
about 20% more intense, as observed for alkyl-disubsti-
tuted ferrocenes.14
F igu r e 3. 1H NMR chemical shift changes (∆δ) of the
â-bipyridinium protons of 14+ upon 1:1 adduct formation with
the ferrocene derivatives 12, 18, and 21 in (CD3)2NCDO at
300 K as a function of concentration.
R-bipyridinium hydrogen atoms and the polyether oxygen
atoms) with the tetracationic cyclophane 14+ and the Ka
values increase accordingly. The Ka value‚also obtained
by the dilution method10 using the same probe protonssfor
the 1:1 adduct formed between 1‚4PF6 and 12 drops by
approximately 1 order of magnitude (Table 1) in (CD3)2-
NCDO, the solvent that has to be used in the case of the
ferrocene derivatives 18 and 21 containing substituted
tetraarylmethane groups because of their low solubilities
in CD3CN. Clearly, the high polarity of (CD3)2NCDO
means that it more efficiently solvates the ferrocene
derivatives, making them less susceptible to forming
inclusion adducts with the tetracationic cyclophane 14+
.
The chemical shift changes, experienced by the protons
in 14+ upon adduct formation with 1 equiv of the
ferrocene derivatives 12, 18, and 21 in (CD3)2NCDO (0.01
mol L-1), are listed in Table 2. Figure 3 presents
graphically the chemical shift changes for the â-bipyri-
dinium protons of 14+ upon adduct formation (1:1 mix-
tures) with the ferrocene derivatives 12, 18, and 21 in
(CD3)2NCDO at 300 K at various concentrations below
0.01 mol L-1. They are quite similar, and so no significant
differences were observed in the Ka values (Table 1) of
the 1:1 adducts formed between 1‚4PF6 and 12, 18, and
21, suggesting that the bulky stoppers do not affect
appreciably the molecular recognition event; i.e., in
common with the ferrocene derivatives 18 and 21, which
can only exist in co-conformation A on 1:1 adduct
formation with the tetracationic cyclophane 14+, com-
pound 12, which could exist in co-conformation B with
F igu r e 4. Absorption spectra in MeCN at 298 K of the
tetracationic cyclophane 14+ and the ferrocene derivative 12.
As for the unsubstituted ferrocene,15 its derivative 12
does not show any luminescence. The biphenyl units
incorporated in 14+ are potentially fluorescent,11 but their
emission is quenched in the cyclophane because of the
presence of low energy charge-transfer levels.
(11) Berlman, I. B. Handbook of Fluorescence Spectra of Aromatic
Compounds, Academic Press: London, 1965.
(12) Anelli, P.-L.; Ashton, P. R.; Ballardini, R.; Balzani, V.; Delgado,
M.; Gandolfi, M. T.; Goodnow, T. T.; Kaifer, A. E.; Philp, D.; Pietrasz-
kiewicz, M.; Prodi, L.; Reddington, M. V.; Slawin, A. M. Z.; Spencer,
N.; Stoddart, J . F.; Vicent, C.; Williams, D. J . J . Am. Chem. Soc. 1992,
114, 198-213.
(13) Ashton, P. R.; Baldoni, V.; Balzani, V.; Claessens, C. G.; Credi,
A.; Hoffmann, H. D. A.; Raymo, F. M.; Stoddart, J . F.; Venturi, M.;
White, A. J . P.; Williams, D. J . Eur. J . Org. Chem. 2000, in press.
(14) Lever, A. B. P. Inorganic Electronic Spectroscopy, Elsevier:
Amsterdam, 1984.
1
4+, also exists only in co-conformation A. Finally, addi-
tion of 1‚4PF6 (10.8 equiv) to a very dilute solution (7.7
× 10-4 mol L-1) of 21 in CD3CN resulted in significant
upfield shifts of the hydroquinone ring protons at 300 K.
They “move” from δ 6.80 and 6.81 to δ 6.63 and 6.70 in
the experiment just described. Chemical shift changes
are also evident for the cyclopentadienyl and polyether
(15) Balzani, V.; Carassiti, V. Photochemistry of Coordination
Compounds; Academic Press: London, 1970.

1952 J . Org. Chem., Vol. 65, No. 7, 2000
Balzani et al.
F igu r e 5. Absorption spectra in MeCN at 298 K. (a) Sum of
the spectra of the separated components 14+ (3.2 × 10-4 mol
L-1) and 12 (3.2 × 10-3 mol L-1); (b) spectrum of the mixture
of the two components [concentrations as in (a)]; (c) enlarged
view (× 5) of the difference between curves (b) and (a).
F igu r e 6. Cyclic voltammetric patterns at 298 K of MeCN
solutions containing 3.0 × 10-4 mol L-1 of 14+ (full line), and
3.0 × 10-4 mol L-1 of 14+ with 3.0 × 10-3 mol L-1 of 12 (dashed
line). Scan rate: 50 mV s-1. The reference wave of the
[Ru(bpy)3]2+/+ process (E1/2 ) -1.32 V vs SCE) is also shown.
Upon titration of a 3.2 × 10-4 mol L-1 MeCN solution
of 14+ with 12, we observed the appearance of an
absorption tail at λ > 550 nm, where none of the free
components absorbs. After subtraction of the spectrum
of 12 from the absorption spectrum of the mixture, a
broad band with λmax ) 570 nm was obtained (Figure 5);
such a band can be assigned to a donor/acceptor interac-
tion between the π-electron-deficient bipyridinium units
of 14+ and the π-electron-rich cyclopentadienyl rings of
12. The titration curve obtained by monitoring the
absorbance of the donor/acceptor band can be fitted
according to the formation of a 1:1 adduct between 14+
and 12, with an absorption coefficient at 570 nm of 170
( 30 L mol-1 cm-1 and an association constant consistent
with that observed by NMR spectroscopy.
form. The adduct [1:12]4+ shows a reversible monoelec-
tronic oxidation process at +0.46 V vs SCE (Figure 7),
that can be assigned to the ferrocene unit of its acyclic
component. This process occurs (i) at a potential value
50 mV more positive than that of uncomplexed 12 and
(ii) with a current intensity which is about 20% smaller.
These results are consistent with the formation of an
inclusion adduct between 14+ and 12 and can be ac-
counted for by (i) the presence of a donor/acceptor
interaction between the π-electron-deficient bipyridinium
units of 14+ and the π-electron-rich cyclopentadienyl rings
of 12 and (ii) the decrease of the diffusion coefficient of
12 when it is surrounded by the 14+ cyclophane.18
The 1:1 adduct formation between 14+ and both fer-
rocene derivatives 18 and 21 was also evident from their
absorption spectra. Thus, in the mixed solvent, MeCN-
DMF (4:1), both 18 and 21 (each at concentrations of 1.6
× 10-3 mol L-1) gave rise to an absorption coefficient at
570 nm of 90 L mol-1 cm-1 when they were mixed
together with an equimolar amount of 14+
.
Electr och em ica l P r op er ties. We have investigated
the electrochemical behavior of the cyclophane 14+, the
ferrocene derivative 12, and their [1:12]4+ adduct by (i)
cyclic voltammetry, (ii) differential pulse voltammetry,
and (iii) bulk electrolysis in MeCN at room temperature.
Cyclophane 14+ shows two reversible two-electron
reduction processes at -0.31 V and -0.72 V vs SCE
(Figure 6) that can be ascribed to the simultaneous one-
electron reduction of the two equivalent bipyridinium
units.16 No oxidation process is observed. As expected,
compound 12 exhibits (Figure 7) the reversible one-
electron oxidation process characteristic of ferrocene17
and no reduction processes. It is interesting to note that
the ferrocene unit of 12 is oxidized at a potential value
(+0.41 V vs SCE) very similar to that of unsubstituted
ferrocene, indicating that the presence of the polyether
chains does not influence the electrochemical properties
of the redox-active unit.
F igu r e 7. Cyclic voltammetry (top; scan rate: 50 mV s-1) and
differential pulse voltammetry (bottom; scan rate: 20 mV s-1
;
pulse height: 75 mV) at 298 K of MeCN solutions containing:
(a) 3.0 × 10-4 mol L-1 of 12 (full line); (b) 3.0 × 10-4 mol L-1
of 12 and 3.0 × 10-3 mol L-1 of 14+ (dashed line); (c) same
solution as in (b), after exhaustive electrolysis at +0.50 V vs
SCE (dashed-dotted line). Subsequent exhaustive electrolysis
at 0.0 V gives a voltammetric pattern identical to that observed
for solution (b) (dashed line). The feature with E1/2 ) +1.29 V
vs SCE corresponds to the [Ru(bpy)3]3+/2+ reference process.
The electrochemical behavior of the adduct [1:12]4+ on
oxidation and reduction was studied in the presence of
an excess of 14+ and 12, to obtain more than 90% of the
electroactive unit under investigation in the complexed
(16) Amabilino, D.; Ashton, P. R.; Balzani, V.; Boyd, S. E.; Credi,
A.; Lee, J . Y.; Menzer, S.; Stoddart, J . F.; Venturi, M.; Williams, D. J .
J . Am. Chem. Soc. 1998, 120, 4295-4307.
(17) Mann, C. K.; Barnes, K. K. Electrochemical Reactions in Non
Aqueous Systems; Dekker: New York, NY, 1970.
Since the [1:12]4+ adduct is stabilized by donor/acceptor
interactions, it may be expected that oxidation of the

Decomplexation of Inclusion Adducts of Ferrocene
J . Org. Chem., Vol. 65, No. 7, 2000 1953
F igu r e 8. Schematic representation of the electrochemically induced decomplexation/recomplexation processes of the [1:12]4+
complex.
electrolysis at +0.50 V vs SCE to oxidize the ferrocene
unit of [1:12]4+. After exhaustive electrolysis, the system
showed again a reversible monoelectronic oxidation
process at +0.46 V, but its current intensity was the same
as that observed (Figure 7) for uncomplexed 12. Such a
current increase indicates that the electroactive species
that is diffusing to the electrode is now the free 12+
cation, while the fact that the process maintains revers-
ibility and occurs at the potential characteristic of the
adduct suggests that the complexation/decomplexation
equilibrium is fast on the time scale of the electrochemi-
cal scan. Subsequent exhaustive electrolysis at 0.0 V
gives back adduct [1:12]4+, as demonstrated (Figure 7)
by the voltammetric patterns.22
On the reduction side, the two reversible two-electron
processes of 14+ are maintained in the [1:12]4+ adduct
(Figure 5). The first process is slightly shifted (30 mV)
toward more negative potential values, while the second
one occurs practically at the same potential as that
observed for the free cyclophane. The negative shift of
F igu r e 9. Two possible co-conformations (A and B) for a 1:1
adduct formed between cyclobis(paraquat-4,4′-biphenylene)
the potential corresponding to the first reduction process
can be explained on the basis of the donor/acceptor
interaction taking place in the [1:12]4+ adduct. The
occurrence of the second reduction process at the same
potential observed for the free cyclophane suggests that,
and a 1,1′-disubstituted ferrocene derivative and the covalent
attachment of stoppers at the ends of the two substituents of
the guest.
electron-donor component leads to disruption of the
adduct.7i,k-m,19-21 This possibility was investigated by bulk

1954 J . Org. Chem., Vol. 65, No. 7, 2000
Balzani et al.
after monoelectronic reduction of both the bipyridinium
units of 14+, the adduct is disrupted and the successive
reduction takes place on the free cyclophane. These
results are in agreement with previous studies,7i,19-21
which show that the donor/acceptor interaction between
bipyridinium-containing macrocycles and π-electron-rich
guests is destroyed upon reduction of the bipyridinium
units. This behavior is confirmed by voltammetric studies
carried out on 12 in a solution containing an excess of
a 1,1′-disubstituted ferrocene nucleus, extremely small
quantities (<1%) of the expected [2]rotaxane are detected.
The association constant for the 1:1 adduct [1:12]4+ is
affected dramatically by the nature of the solvent.
Changing from CD3CN to (CD3)2NCDO reduces the
association constant from 3900 to 290 L mol-1. This
adduct has been investigated by absorption and emission
electronic spectroscopy and electochemistry. It shows a
charge-transfer absorption band in the visible spectral
region and no luminescence. An electrochemical study
has demonstrated that oxidation of the ferrocene-based
unit of the guest and first reduction of the bipyridinium
moieties of the host occur at more positive and, respec-
tively, more negative potentials than in the free compo-
nents. Detailed analysis of the electrochemical results
shows that such oxidation and reduction processes cause
disruption of the adduct and that recomplexation takes
place upon back reduction and oxidation of the oxidized
ferrocene and reduced bipyridinium units, respectively.
The complexation/decomplexation process is reversible
and fast on the time scale of the electrochemical scan.
1
4+ upon electrolysis of the cyclophane at -0.40 V vs SCE,
which leads to quantitative one-electron reduction of the
bipyridinium units.
Interestingly, the presence of 12 does not cause a
decrease in the current intensity corresponding to the
reduction processes of 14+. This observation is not in
conflict with the formation of the [1:12]4+ adduct since it
may be expected that the diffusion coefficient of 14+ is
not significantly altered by the inclusion of 12.
In summarysas schematized in Figure 8sthe electro-
chemical results show that the [1:12]4+ adduct undergoes
reversible decomplexation/recomplexation processes on
a time scale faster than that of the electrochemical
experiments.
Exp er im en ta l Section
Gen er a l Meth od s. Solvents were dried according to lit-
erature procedures.23 The compounds 3,1 4,24 13‚2PF6,25 14,25
and 1912 were prepared as described previously in the litera-
ture. Thin-layer chromatography (TLC) was carried out on
aluminum sheets coated with silica gel 60. Column chroma-
tography was performed on silica gel 60 (230-400 mesh).
Melting points are uncorrected. Liquid secondary ion mass
spectrometry (LSIMS) and fast-atom bombardment mass
spectrometry (FABMS) were performed using a 3-nitrobenzyl
alcohol or 2-nitrophenyloctyl ether matrix. 1H NMR spectra
were recorded either at 300 or 400 MHz, while 13C NMR
spectra were recorded at 75 MHz.
Associa tion Con sta n ts. Equimolar CD3CN or (CD3)2-
NCDO solutions of 1‚4PF6 and 11, 12, 18, or 21 were diluted
from ca. 10-2 to ca. 10-4 mol L-1 in 10-15 consecutive steps.
The resulting solutions were analyzed by 1H NMR spectroscopy
at 300 K. By nonlinear curve-fitting of the plot of the chemical
shift change associated with the resonances of the â-bipyri-
dinium protons against the concentration, the association
constants (Ka) of the adducts were determined10 employing the
following relationship
Con clu sion s
1,1′-Disubstituted ferrocene derivatives template the
formation of cyclobis(paraquat-4,4′-biphenylene) as a
result of second-sphere coordination.3 The yields observed
in this template-directed synthesis rise up to 32% (cf. 2%
in the absence of a template) when polyether chains are
attached to the ferrocene nucleus. We believe that some
of the polyether oxygen atoms of the template sustain
[C-H...O] hydrogen-bonding interactions with the R-bi-
pyridinium hydrogen atoms of the tetracationic cyclo-
phane. These hydrogen bonds supplement the [π...π]
stacking interactions between the cyclopentadienyl rings
and the bipyridinium units. In the second-sphere adducts
formed between cyclobis(paraquat-4,4′-biphenylene) and
1,1′-disubstituted ferrocene derivatives, the two substit-
uents of the guest protrude outward (A in Figure 9) from
the cavity of the host in the same direction. Pseudoro-
taxane-like adducts (B in Figure 9), in which the two
substituents of the guest protrude outward from opposite
sides of the host, are not formed. Thus, complexation,
followed by the covalent attachment of bulky groups to
the termini of these substituents, cannot link mechani-
cally the guest to the host; i.e., no rotaxanes can be
formed. Similarly, when the acyclic precursors of cyclobis-
(paraquat-4,4′-biphenylene) are reacted in the presence
of a preformed dumbbell-shaped compound incorporating
-∆δâ ) (-∆δsat/c)[2Kac + 1 - [(2Kac + 1)2 -
2
4Ka c2]0.5]/2Ka
where ∆δ denotes the chemical shift difference of the â-bipy-
ridinium protons upon complexation at a concentration c of
each of the two components, 14+ and the ferrocene derivative,
and ∆δsat is the chemical shift difference at saturation.
Absor p tion a n d Lu m in escen ce Mea su r em en ts. Elec-
tronic absorption and luminescence spectra were recorded in
MeCN solutions at room temperature.
Electr och em ica l Mea su r em en ts. Electrochemical experi-
ments were carried out in argon-purged MeCN solutions at
room temperature with a multipurpose instrument interfaced
to a personal computer. In the experiments where cyclic
(18) The decrease in current intensity associated with the oxidation
of 12 in the adduct with respect to the free compound is that expected
according to the Stokes-Einstein expression of the diffusion coefficient
(D M-1/3).
(19) Ashton, P. R.; Ballardini, R.; Balzani, V.; Boyd, S. E.; Credi,
A.; Gandolfi, M. T.; Go´mez-Lo´pez, M.; Iqbal, S.; Philp, D.; Preece, J .
A.; Prodi, L.; Ricketts, H. G.; Stoddart, J . F.; Tolley, M. S.; Venturi,
M.; White, A. J . P.; Williams, D. J . Chem. Eur. J . 1997, 3, 152-170.
(20) Asakawa, M.; Ashton, P. R.; Balzani, V.; Credi, A.; Mattersteig,
G.; Matthews, O. A.; Montalti, M.; Spencer, N.; Stoddart, J . F.; Venturi,
M. Chem. Eur. J . 1997, 3, 1992-1996.
(21) Ashton, P. R.; Balzani, V.; Becher, J .; Credi, A.; Fyfe, M. C. T.;
Mattersteig, G.; Menzer, S.; Nielsen, M. B.; Raymo, F. M.; Stoddart,
J . F.; Venturi, M.; Williams, D. J . J . Am. Chem. Soc. 1999, 121, 3951-
3957.
(22) The one-electron oxidized form of ferrocene, either produced by
electrolysis or chemical oxidation using Fe(ClO4)3, undergoes some
degradation in MeCN solution on the time scale of minutes. The same
behavior is exhibited by compound 12.
(23) Furniss, B. S.; Hannaford, A. J .; Smith, P. W. G.; Tatchell, A.
R. Practical Organic Chemistry; Longman: New York, NY, 1989.
(24) Ashton, P. R.; Ballardini, R.; Balzani, V.; Belohradsky, M.;
Gandolfi, M. T.; Philp, D.; Prodi, L.; Raymo, F. M.; Reddington, M. V.;
Spencer, N.; Stoddart, J . F.; Venturi, M.; Williams, D. J . J . Am. Chem.
Soc. 1996, 118, 4931-4951.
(25) Amabilino, D. B.; Ashton, P. R.; Brown, C. L.; Co´rdova, E.;
God´ınez, L. A.; Goodnow, T. T.; Kaifer, A. E.; Newton, S. P.; Pietrasz-
kiewicz, M.; Philp, D.; Raymo, F. M.; Reder, A. S.; T. Rutland, M.;
Slawin, A. M. Z.; Spencer, N.; Stoddart, J . F.; Williams, D. J . J . Am.
Chem. Soc. 1995, 117, 1271-1293.

Decomplexation of Inclusion Adducts of Ferrocene
J . Org. Chem., Vol. 65, No. 7, 2000 1955
voltammetry (CV) and differential pulse voltammetry (DPV)
techniques were employed, the working electrode was a glassy
carbon electrode (0.08 cm2, Amel); its surface was routinely
polished with a 0.05 µm alumina-water slurry on a felt surface
immediately prior to use. The electrolyses were carried out
using a Pt grid as a working electrode. In all cases, the counter
electrode was a Pt wire and the reference electrode was a
saturated calomel electrode (SCE) separated with a fine glass
frit. The concentration of the examined compounds was 3.0 ×
10-4 mol L-1; 0.05 M tetraethylammonium hexafluorophos-
phate was added as the supporting electrolyte. Cyclic volta-
mmograms were obtained at sweep rates of 20, 50, 200, 500,
and 1000 mV s-1; DPV experiments were performed with a
scan rate of 20 mV s-1, a pulse height of 75 mV, and a duration
of 40 ms. All processes observed were reversible, according to
the criteria of (i) separation of 60 mV between cathodic and
anodic peaks, (ii) close-to-unity ratio of the intensities of the
cathodic and anodic currents, and (iii) constancy of the peak
potential on changing sweep rate in the cyclic voltammograms.
The same halfwave potential values have been obtained from
the DPV peaks and from an average of the cathodic and anodic
cyclic voltammetric peak. Both CV and DPV techniques have
been used to estimate the current intensity associated with
each redox process. [Ru(bpy)3]2+ was employed26 as an internal
standard for both potential values and current intensities. The
experimental error on the potential values was estimated to
be (10 mV.
solution of 7 (1.90 g, 3.38 mmol), (COCl)2 (1.5 mL, 17.19 mmol),
and DMF (5 drops) in dry CH2Cl2 (100 mL) was heated for 17
h under reflux in an atmosphere of N2. After being cooled to
ambient temperature, the solvent was distilled off under
reduced pressure to give a yellowish solid. A solution of the
solid residue, 3 (423 mg, 0.88 mmol), and 2,6-dimethylpyridine
(245 µL, 2.1 mmol) in dry CH2Cl2 (100 mL) was heated for 4
h under reflux in an atmosphere of N2. After being cooled to
room temperature, the solution was diluted with CH2Cl2,
washed with H2O, and dried (MgSO4) before the solvent was
distilled off under reduced pressure. The resulting solid was
purified by column chromatography (SiO2: CHCl3) to give 9
(740 mg, 54%) as a yellow solid: mp 84 °C; LSIMS m/z 1571
1
[M]+; H NMR (CDCl3) δ 7.22 (12H, d, J ) 9 Hz), 7.12-7.03
(16H, m), 6.75 (4H, d, J ) 9 Hz), 4.61 (4H, s), 4.40-4.33 (4H,
m), 4.15-4.04 (4H, m), 3.94-3.91 (4H, m), 3.88-3.80 (4H, m),
3.76-3.69 (8H, m), 3.68-3.61 (8H, m), 1.30 (54H, s); 13C NMR
[(CD3)2CO] δ 169.3, 156.9, 149.1, 145.1, 140.9, 132.7, 131.4,
125.0, 114.1, 71.3, 71.2, 70.7, 70.6, 69.5, 65.6, 64.7, 63.8, 63.0,
56.6, 34.7, 31.6. Anal. Calcd for C100H122FeO12: C, 76.41; H,
7.82. Found: C, 76.21; H 7.90.
1,1′-B is [[2-(2-m e t h o x y e t h o x y )e t h o x y ]m e t h y le n e ]-
fer r ocen e (12). A solution of 10 (1.60 g, 5.80 mmol) in dry
THF (50 mL) was added to a mixture of 11 (0.15 g, 0.59 mmol)
and NaH (95% dry, 0.035 g, 1.39 mmol) in dry THF (50 mL).
The mixture was heated for 12 h under reflux in an atmo-
sphere of Ar. Another portion of NaH (95% dry, 0.035 g, 1.39
mmol) was added to the mixture, and heating under reflux
was mantained for a further 10 h. After being cooled to room
temperature, H2O was added, and the mixture was extracted
with CH2Cl2. The combined organic phases were washed with
H2O, dried (MgSO4), and concentrated under reduced pressure.
Purification of the residue by column chromatography [SiO2:
CH2Cl2/Me2CO (3:2)] afforded 12 (0.205 g, 77%) as an orange
oil: FABMS m/z 450 [M]+; 1H NMR (CDCl3) δ 4.28 (4H, br s),
4.19 (4H, br s), 4.11 (4H, br s), 3.63-3.52 (16H, m), 3.37 (6H,
s); 13C NMR (CDCl3) δ 71.9, 70.6, 70.5, 70.0, 69.2, 69.0, 59.0.
Cyclobis(p a r a qu a t-4,4′-bip h en ylen e)1 (1•4P F 6). A solu-
tion of 12 (0.1436 g, 0.32 mmol), 13‚2PF6 (0.1333 g, 0.17 mmol),
and 14 (0.0581 g, 0.17 mmol) in dry MeCN (20 mL) was stirred
for 14 d at ambient temperature. The solvent was distilled off
under reduced pressure, washed with CHCl3, and purified by
column chromatography [SiO2: MeOH/2 M NH4Cl/MeNO2 (7:
2:1)]. The resulting solid was dissolved in H2O, and after the
addition of NH4PF6, 1‚4PF6 (0.0673 g, 32%) precipitated out
as white solid: mp >250 °C; FABMS m/z 963 [M + H - 2PF6]+,
818 [M - 3PF6]+; 1H NMR (CD3CN) δ 8.92 (8H, d, J ) 7 Hz),
8.24 (8H, d, J ) 7 Hz), 7.65 (8H, d, J ) 7 Hz), 7.53 (8H, d, J
) 7 Hz), 5.80 (8H, s).
Anal. Calcd for
Found: C, 57.98; H, 7.51.
C22H34FeO6‚0.25H2O: C, 58.09; H, 7.64.
Eth yl 2-[4-[Tr is(4-ter t-bu tylp h en yl)m eth yl]p h en oxy]-
a ceta te (6). A mixture of 4 (8.61 g, 0.02 mol) and K2CO3 (55.07
g, 0.40 mol) in dry MeCN (1.6 L) was heated under reflux and
an atmosphere of N2, and then 5 (6.0 mL, 0.05 mol) was added.
Heating under reflux was mantained for a further 20 h, and
after being cooled to room temperature, the mixture was
filtered and the solvent was distilled off under reduced
pressure. The residue was dissolved in CH2Cl2, washed with
H2O, and dried (MgSO4) before the solvent was distilled off
under reduced pressure to afford 6 (10.03 g, 100%) as a white
solid: mp 223 °C; LSIMS m/z 590 [M]+; 1H NMR (CDCl3) δ
7.23 (6H, d, J ) 9 Hz), 7.13-7.04 (8H, m), 6.77 (2H, d, J ) 9
Hz), 4.59 (2H, s), 4.27 (2H, q, J ) 7 Hz), 1.32-1.28 (30H, m);
13C NMR (CDCl3) δ 169.1, 155.8, 148.4, 144.0, 140.7, 132.3,
130.7, 124.1, 111.3, 65.5, 63.1, 61.3, 34.3, 31.4, 14.2. Anal.
Calcd for C41H50O3: C, 83.35; H, 8.53. Found: C, 83.40; H,
8.45.
2-[4-[Tr is(4-ter t-b u t ylp h en yl)m et h yl]p h en oxy]a cet ic
Acid (7). A mixture of 6 (10.03 g, 0.02 mol) and 0.6 M aqueous
NaOH (1 L) in EtOH (1.5 L) was heated under reflux for 5 h.
After being cooled to room temperature, the mixture was
concentrated under reduced pressure, diluted with 1.6 M
aqueous HCl, and stirred for 15 min at ambient temperature.
Filtration of the mixture afforded a white solid that was
washed with H2O and dried to give 7 (9.41 g, 98%): mp 270
°C dec; LSIMS m/z 563 [M + H]+; 1H NMR (CDCl3) δ 7.22 (6H,
d, J ) 9 Hz), 7.13-7.02 (8H, m), 6.76 (2H, d, J ) 9 Hz), 4.62
(2H, s), 1.29 (27H, s); 13C NMR (CDCl3) δ 173.1, 155.2, 148.4,
143.9, 141.3, 132.5, 130.7, 124.1, 113.3, 65.3, 63.1, 34.3, 31.4.
Anal. Calcd for C39H46O3: C, 83.24; H, 8.24. Found: C, 83.20;
H, 8.29.
2-[2-[2-[2-[4-[Tr is(4-ter t-bu tylp h en yl)m eth yl]p h en oxy]-
eth oxy]eth oxy]eth oxy]eth a n ol (16). A mixture of 4 (4.75
g, 8.8 mmol), 15 (6.10 g, 17.5 mmol), and K2CO3 (1.21 g, 8.8
mmol) in dry MeCN (150 mL) was heated for 12 h under reflux
in an atmosphere of Ar. After being cooled to ambient tem-
perature, the solvent was distilled off under reduced pressure.
The residue was dissolved in CHCl3, washed with H2O, and
dried (MgSO4) before the solvent was removed under reduced
pressure. The residue was purified by column chromatography
[SiO2: (i) CH2Cl2/MeCO2Et (1:1), (ii) gradual increase of
MeCO2Et in the eluant] to give 16 (3.94 g, 66%) as a white
solid: mp 175-176.5 °C; FABMS m/z ) 680 [M] +; HRFABMS
+
m/z calcd for [M]
(C45H60O5) ) 680.4441, m/z found )
680.4451; 1H NMR (CDCl3) δ 7.23 (6H, d, J ) 9 Hz), 7.08 (8H,
d, J ) 9 Hz), 6.78 (2H, d, J ) 9 Hz), 4.11 (2H, t, J ) 5 Hz),
3.84 (2H, t, J ) 5 Hz), 3.75-3.66 (10H, m), 3.60 (2H, t, J ) 5
Hz), 2.29 (1H, s), 1.30 (27H, s). 13C NMR (CDCl3): δ 156.5,
148.3, 144.1, 139.8, 132.2, 130.7, 124.0, 113.0, 72.5, 70.7, 70.6,
70.6, 70.3, 69.8, 67.2, 63.0, 61.7, 34.3, 31.4. Anal. calcd for
C
45H60O5‚0.25H2O: C, 78.85;, H, 8.90. Found: C, 78.71; H,
8.82.
2-[2-[2-[2-[4-[Tr is(4-ter t-bu tylp h en yl)m eth yl]p h en oxy]-
et h oxy]et h oxy]et h oxy]et h yl 4-Met h ylp h en ylsu lfon a t e
(17). A solution of tosyl chloride (2.70 g, 14.2 mmol) in CH2-
Cl2 (20 mL) was added to an ice-cooled solution of 16 (3.797 g,
5.58 mmol), DMAP (0.020 g, 0.16 mmol), and Et3N (4 mL) in
CH2Cl2 over a period of 30 min. The mixture was stirred for
12 h at ambient temperature, poured into 5 M aqueous HCl,
and then diluted with H2O. The organic phase was washed
with 1 M aqueous HCl and H2O before it was dried (MgSO4).
The solvent was distilled off under reduced pressure, and the
residue was purified by column chromatography [SiO2: (i) CH2-
Cl2, (ii) MeCO2Et/CH2Cl2 with a gradual increase of MeCO2-
Et in the eluant] to afford 17 (3.755 g, 81%) as a white solid:
mp 168-168.5 °C; FABMS m/z 835 [M + H]+; 1H NMR (CDCl3)
δ 7.79 (2H, d, J ) 8 Hz), 7.32 (2H, d, J ) 8 Hz), 7.23 (6H, d,
1,1′-Bis[2-[2-[2-[2-[4-[t r is(4-ter t-b u t ylp h en yl)m et h yl]-
p h en oxy]a cetoxy]eth oxy]eth oxy]eth oxy]fer r ocen e (9). A
(26) J uris, A.; Balzani, V.; Barigelletti, F.; Campagna, S.; Belser,
P.; von Zelewsky, A. Coord. Chem. Rev. 1988, 84, 85-277.

1956 J . Org. Chem., Vol. 65, No. 7, 2000
Balzani et al.
J ) 9 Hz), 7.07 (8H, d, J ) 9 Hz), 6.76 (2H, d, J ) 9 Hz), 4.15
(2H, t, J ) 5 Hz), 4.09 (2H, t, J ) 5 Hz), 3.83 (2H, t, J ) 5
Hz), 3.71-3.62 (6H, m), 3.59 (4H, s), 2.42 (3H, s), 1.30 (27H,
s); 13C NMR (CDCl3) δ 156.5, 148.3, 144.7, 144.1, 139.7, 133.0,
132.2, 130.7, 129.8, 128.0, 124.0, 113.0, 70.8, 70.7, 70.6, 69.8,
69.2, 68.7, 67.2, 63.0, 34.3, 31.4, 21.6. Anal. Calcd for
C52H66O7S: C, 74.79; H, 7.97. Found: C, 74.54; H, 7.91.
1,1′-Bis[[2-[2-[2-[2-[4-[tr is(4-ter t-bu tylp h en yl)m eth yl]-
p h e n oxy]e t h oxy]e t h oxy]e t h oxy]e t h oxy]m e t h yle n e ]-
fer r ocen e (18). A mixture of 11 (0.191 g, 0.78 mmol), 17
(3.569 g, 4.27 mmol), and NaH (95% dry, 0.046 g, 1.82 mmol)
in dry THF (50 mL) was heated for 12 h under reflux in an
atmosphere of Ar. Another portion of NaH (95% dry, 0.046 g,
1.82 mmol) was added, and the mixture was heated under
reflux for a further 10 h. After the mixture was cooled to
ambient temperature, H2O was added, and the mixture was
washed with CH2Cl2. The combined organic phases were
washed with H2O and dried (MgSO4). The solvent was distilled
off under reduced pressure, and the residue was purified by
column chromatography [SiO2: CH2Cl2/Me2CO (7:1)] to afford
18 (0.730 g, 60%) as a yellow solid: mp 164-166 °C; FABMS
1,1′-Bis[[2-[2-[2-[2-[4-[2-[2-[2-[2-[4-[tr is(4-ter t-bu tylp h e-
n yl)m e t h yl]p h e n oxy]e t h oxy]e t h oxy]e t h oxy]e t h oxy]-
p h e n oxy]e t h oxy]e t h oxy]e t h oxy]e t h oxy]m e t h yle n e ]-
fer r ocen e (21). A mixture of 11 (0.025 g, 0.10 mmol), 20
(0.575 g, 0.52 mmol), and NaH (95% dry, 0.009 g, 0.36 mmol)
in dry THF (15 mL) was heated for 12 h under reflux in an
atmosphere of Ar. Another portion of NaH (95% dry, 0.006 g,
0.24 mmol) was added, and the mixture was heated for a
further 10 h. After being cooled to ambient temperature, the
mixture was diluted with H2O and washed with CH2Cl2. The
combined organic phases were washed with H2O and dried
(MgSO4). The solvent was distilled off under reduced pressure,
and the residue was purified by column chromatography [SiO2:
CH2Cl2/Me2CO (10:1)] to afford 21 (0.079 g, 37%) as a yellow
1
solid: mp 139.5-140.5 °C; FABMS m/z 2108 [M]+; H NMR
(CDCl3) δ 7.23 (12H, d, J ) 9 Hz), 7.07 (16H, d, J ) 9 Hz),
6.82 (8H, s), 6.77 (4H, d, J ) 9 Hz), 4.29 (4H, br s), 4.17 (4H,
br s), 4.11-4.08 (8H, m), 4.06 (8H, t, J ) 5 Hz), 3.85-3.47
(52H, m), 1.30 (54H, s). Anal. Calcd for C130H170FeO20
74.05; H, 8.13. Found: C, 73.98; H, 8.19.
: C,
1,4-Bis[2-[2-[2-[2-[4-[2-[2-[2-[2-[4-[tr is(4-ter t-bu tylp h e-
n yl)m e t h yl]p h e n oxy]e t h oxy]e t h oxy]e t h oxy]e t h oxy]-
ben zen e (23). A solution of 17 (1.30 g, 1.56 mmol), 22 (0.045
g, 0.41 mmol), and K2CO3 (0.18 g, 1.30 mmol) in dry MeCN
(50 mL) was heated for 2 d under reflux in an atmosphere of
Ar. After the solution was cooled to ambient temperature, the
residue was dissolved in CH2Cl2, washed with H2O, and dried
(MgSO4). The solvent was removed under reduced pressure,
and the residue was purified by column chromatography [SiO2:
CH2Cl2/MeCO2Et (5:1)] to afford 23 (0.406 g, 69%) as a white
solid: mp 166-167 °C; FABMS m/z 1436 [M + 2H]+; 1H NMR
(CDCl3) δ 7.22 (12H, d, J ) 9 Hz), 7.07 (16H, d, J ) 9 Hz),
6.81 (4H, s), 6.77 (4H, d, J ) 9 Hz), 4.09 (4H, t, J ) 5 Hz),
4.05 (4H, t, J ) 5 Hz), 3.84-3.67 (24H, m), 1.29 (54H, s); 13C
NMR (CDCl3) δ 156.6, 153.1, 148.3, 144.1, 139.7, 132.2, 130.7,
124.0, 115.5, 113.1, 70.8, 70.7, 69.8, 69.8, 68.0, 67.2, 63.0, 34.3,
31.4. Anal. Calcd for C96H122O10: C, 80.30; H, 8.56. Found: C,
80.01; H, 8.41.
1
m/z 1571 [M + H]+; H NMR (CDCl3) δ 7.23 (12H, d, J ) 9
Hz), 7.08 (16H, d, J ) 9 Hz), 6.77 (4H, d, J ) 9 Hz), 4.27-4.11
(12H, br m), 4.09 (4H, t, J ) 5 Hz), 3.83 (4H, t, J ) 5 Hz),
3.72-3.55 (24H, m), 1.30 (54H, s). Anal. Calcd for C102H130
FeO10: C, 77.93; H, 8.34. Found: C, 77.87; H, 8.30.
-
2-[2-[2-[2-[4-[2-[2-[2-[2-[4-[Tr is(4-ter t-bu tylp h en yl)m e-
t h yl]p h en oxy]et h oxy]et h oxy]et h oxy]et h oxy]p h en oxy]-
et h oxy]et h oxy]et h oxy]et h yl 4-Met h ylp h en ylsu lfon a t e
(20). A solution of 4 (0.495 g, 0.91 mmol), 19 (2.810 g, 3.65
mmol), and K2CO3 (0.13 g, 0.94 mmol) in dry MeCN (100 mL)
was heated for 12 h under reflux in an atmosphere of Ar. After
the solution was cooled to ambient temperature, the solvent
was distilled off under reduced pressure. The solid residue was
dissolved in CH2Cl2 and the solution was washed with H2O
and dried (MgSO4). The solvent was distilled off under reduced
pressure, and the residue was purified by column chromatog-
raphy [SiO2: CH2Cl2/MeCO2Et (5:1)] to afford 20 (0.615 g, 61%)
as a colorless oil: FABMS m/z 1103 [M + H]+; 1H NMR (CDCl3)
δ 7.79 (2H, d, J ) 8 Hz), 7.33 (2H, d, J ) 8 Hz), 7.22 (6H, d,
J ) 9 Hz), 7.07 (8H, d, J ) 9 Hz), 6.82 (4H, s), 6.77 (2H, d, J
) 9 Hz), 4.15-4.06 (8H, m), 3.85-3.59 (24H, m), 2.43 (3H, s),
1.30 (27H, s); 13C NMR (CDCl3): δ 156.5, 153.0, 153.0, 148.2,
144.7, 144.1, 139.7, 133.0, 132.2, 130.7, 129.8, 127.9, 124.0,
115.5, 113.0, 70.8, 70.7, 70.7, 70.6, 70.5, 69.8, 69.7, 69.2, 68.8,
68.6, 68.0, 67.2, 63.0, 34.2, 31.3, 21.6. Anal. calcd for
Ack n ow led gm en t. Financial support from the Ital-
ian MURST (Supramolecular Devices Project), Univer-
sity of Bologna (Funds for Selected Topics), EU (TMR
grant FMRX-CT96-0076), and Odense University (Ph.D.
scholarship for M.B.N.) is gratefully acknowledged.
C
66H86O12S: C, 71.84; H, 7.86. Found: C, 71.80; H, 7.95.
J O991467Z