Communication between components in metal-directed assemblies of oriented calix[6]arene-based pseudorotaxanes and rotaxanes

Article abstract of DOI:10.1002/ejoc.201101597

Oriented calix[6]arene-based pseudorotaxanes and rotaxanes where the axial component bears a terpyridine ligand as a stopper positioned at the upper rim of the calixarene have been synthesized. The binding ability of the terpyridine unit present in the ax

Full text of DOI:10.1002/ejoc.201101597

FULL PAPER
DOI: 10.1002/ejoc.201101597
Communication between Components in Metal-Directed Assemblies of
Oriented Calix[6]arene-Based Pseudorotaxanes and Rotaxanes
Arturo Arduini,*[a] Rocco Bussolati,[a] Daniele Masseroni,[a] Guy Royal,*[b] and
Andrea Secchi[a]
Dedicated to Professor Andrea Pochini on the occasion of his retirement
Keywords: Calixarenes / Viologens / Electrochemistry / Rotaxanes / Anions
Oriented calix[6]arene-based pseudorotaxanes and rotax-
anes where the axial component bears a terpyridine ligand
as a stopper positioned at the upper rim of the calixarene
have been synthesized. The binding ability of the terpyridine
unit present in the axle toward zinc salts is affected by the
presence of the wheel, its distance with respect to the ca-
lix[6]arene upper rim, and the nature of the counterion of the
zinc salt employed. Metal coordination at the terpyridine unit
changes the electrochemical behavior of the 4,4Ј-bipyrid-
inium unit of the axle inside the wheel in both the pseudo-
rotaxanes and rotaxanes.
thesis of oriented pseudorotaxanes and rotaxanes charac-
terized by the univocal orientation of the two calixarene
rims toward the two termini of the axles derived from 4,4Ј-
dialkylviologen. With the general aim to exploit the unidi-
rectional threading of asymmetrical axles into 1 for the con-
struction of devices and molecular machines endowed with
new properties,[4] we started a study to verify whether the
orientation of the wheel rims toward one particular stopper
could be employed as further a structural information ele-
ment able to subtly modify their properties and/or working
mode.
Introduction
Pseudorotaxanes and rotaxanes encompass a class of de-
vices that, under the action of external energy inputs, are
able to behave as molecular level machines.[1] Recently, in
view of conferring specific functional tasks, remarkable ex-
amples of rotaxanes and pseudorotaxanes endowed with an
increased level of complexity where cooperative and allo-
steric effects play a crucial role in governing their function-
ing mode have been described.[2] It however appears that
the increase in complexity stored in these systems parallels
the increase in the number of parameters that influence
their response to stimulations. Consequently, prediction of
their working mode is far from trivial. Here we report pre-
liminary data that show how the chemical properties and
the response to electrochemical stimuli of oriented calix[6]-
arene-based pseudorotaxanes and rotaxanes are influenced
by the orientation, distance among molecular components,
and presence of a metal cationic effector.[3]
Results and Discussion
We have shown previously that calix[6]arene wheel 1 can
act as a 3D asymmetric and heteroditopic host for the syn-
[a] Dipartimento di Chimica Organica e Industriale,
Università di Parma,
Parco Area delle Scienze 17/A, 43124 Parma, Italy
Fax: +39-0521-905472
Hence, we synthesized axle T(C6) (Scheme 1), where the
central 4,4Ј-bipyridine (bipy) cationic core is functionalized
with two hexyl chains, one of which bears an OH group
suitable for further functionalization at one terminus and a
2,2Ј:6Ј,2ЈЈ-terpyridine (terpy) at the other. This latter unit
was selected because it is bulky enough to act as stopper
E-mail: arturo.arduini@unipr.it
[b] Département de Chimie Moléculaire, UMR CNRS-5250,
Institut de Chimie Moléculaire de Grenoble, FR CNRS-2607,
Université Joseph Fourier Grenoble I
BP 53, 38041 Grenoble Cedex 9, France
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201101597.
Eur. J. Org. Chem. 2012, 1033–1038
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
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A. Arduini, R. Bussolati, D. Masseroni, G. Royal, A. Secchi
FULL PAPER
and because of its well-known ability to efficiently bind
transition metal cations[5] that, in this axle, could possibly
act as effectors.
Scheme 2. Synthesis of oriented pseudorotaxanes P[1ʛT(C6)] and
P[1ʛT(C12)] and rotaxane R[1ʛT(C6)].
Scheme 1. Reagents and conditions: (i) acetone, NaH, DME, reflux
4 h; (ii) NH4OAc, EtOH abs., reflux 6 h; (iii) KOH, DMF, r.t.,
90 min; (iv) 4,4Ј-bipyridine, CH3CN, reflux, 48 h; (v) CH3CN, re-
flux, 10 d.
A slight excess amount of solid axle T(C6) was added to
a C6D6 solution of 1; after mixing, the resulting deep-red
suspension was filtered to remove the excess amount of un-
dissolved salt and the resulting solution was analyzed by
NMR spectroscopy. As expected,[6] the spectroscopic data
showed that the oriented pseudorotaxane P[1ʛT(C6)] that
bears the stopper at the upper rim of the wheel had formed
(see Supporting Information). In a separate experiment,
the threading process was carried out in toluene followed
by the addition of diphenylacetyl chloride to yield the cor-
responding rotaxane R[1ʛT(C6)] (Scheme 2).
To establish whether the binding ability of the terpy unit
in axle T(C6) toward metal cations was affected by the pres-
ence of the 4,4Ј-bipy cationic core, we used Zn(TsO)2. This
metal was chosen because of its well-documented prefer-
ence to adopt an octahedral coordination geometry and its
Figure 1. 1H NMR (CDCl3/CD3OD = 6:4, 300 MHz) stack plot
(expanded region) of T(C6) with Zn(TsO)2: (a) T(C6), (b) T(C6) +
0.5 equiv. Zn(TsO)2, (c) T(C6) + 2 equiv. Zn(TsO)2.
ability to form either 1:1 or 2:1 complexes with terpy li- dition of an excess amount of solid Zn(TsO)2 to
gands.[7] In agreement with the literature data,[8] the 1H P[1ʛT(C6)], in spite of the extensive broadening of several
NMR spectra taken in CDCl3/CD3OD (6:4) showed that signals, suggests that the species that form, because of the
T(C6) forms either the 1:1 or the 1:2 Zn/T(C6) complex, upfield shifts experienced by the terpy protons, are compati-
depending on the ratio between the analytes used and that ble with a unique 2:1 adduct, where the two terpy units
these complexes are in slow exchange on the NMR time assume an orthogonal orientation around the Zn2+ ion.[8c]
scale (Figure 1).
Further support for this stoichiometry was gained by com-
Because P[1ʛT(C6)] could not be employed in the paring, in C6D6, the diffusion coefficient (D) of P[1ʛT(C6)]
CDCl3/CD3OD mixture because of extensive dethreading (D = 2.68Ϯ0.02ϫ10–10 m2 s–1) with that measured after the
of the axle from the wheel, C6D6 was used as the solvent to addition of an excess amount of solid Zn(TsO)2 (D =
evaluate the binding features of the terpy unit in 2.09Ϯ0.05ϫ10–10 m2 s–1), which confirmed the formation
P[1ʛT(C6)] toward Zn2+. The spectra obtained upon ad- of the 2P[1ʛT(C6)]/1Zn complex.[9]
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Eur. J. Org. Chem. 2012, 1033–1038

Communication in Oriented Calixarene-Based Pseudorotaxanes and Rotaxanes
Quantitative data were obtained through UV/Vis tech-
A consequent question that emerged was whether the
niques by titrating T(C6) with Zn(TsO)2 in CHCl3/CH3OH complexation of the Zn2+ ion at the terpy unit could have
(6:4). Data treatment showed the formation of both the 1:1 an effect on the ability of the whole R[1ʛT(C6)] and
and 2:1 complexes with binding constants logK1:1
=
P[1ʛT(C6)] systems to work as molecular machines. To ad-
6.7Ϯ0.3 and logβ 12.3Ϯ0.3, respectively. When dress this issue, the electroactivity of the bipy group in the
=
R[1ʛT(C6)] was employed as the ligand for Zn(TsO)2, it different systems was examined by cyclic voltammetry
emerged that only one complex formed, with logβ = (CV). Experiments were carried out in CH2Cl2 containing
10.7Ϯ0.3, consistent with a stoichiometry R[1ʛT(C6)]/ TBAP as a supporting electrolyte before and upon pro-
Zn2+ = 2:1. This stoichiometry does not change even in the gressive addition of Zn2+ (0.5 to 3 equiv.) to the solution.
presence of a large excess of Zn2+ or by reversing the ad- Representative data are given in Figure 2 and Table 1. As
dition order of one species to the other (see Supporting expected, all the metal-free systems, T(C6), P[1ʛT(C6)],
Information). On the other hand, when Zn(BF4)2 was ti- and R[1ʛT(C6)], showed the same behavior as that of sim-
trated with R[1ʛT(C6)], both the 1R[1ʛT(C6)]/1Zn and ilar previously reported systems (Figure 2a).[11] Namely, the
the 2R[1ʛT(C6)]/1Zn complexes form (logK1:1 = 7.3Ϯ0.3, free T(C6) axle and the R[1ʛT(C6)] rotaxane were both
logβ = 12.7Ϯ0.3, respectively). This particular behavior characterized by two monoelectronic reversible reduction
could be explained by considering that when the more coor- waves at E1/2Ј = –0.68 V vs. Ag+/Ag and E1/2ЈЈ = –1.17 V
dinating tosylate was employed, the perfect match between (axle)[12] and at E1/2Ј = –1.02 V and E1/2ЈЈ = –1.42 V (rotax-
the six tosylate anions and the six ureido binding sites of ane). As expected, when included in the cavity of the wheel,
the two wheels in the 2R[1ʛT(C6)]/1Zn and 2P[1ʛT(C6)]/ the axle becomes more difficult to reduce and large negative
1Zn species drives the formation of these 2:1 complexes shifts (ca. –400 mV) for the reduction waves were thus logi-
(Scheme 3).[10]
cally observed. For the same reason, in the case of the
P[1ʛT(C6)] pseudorotaxane, the first reduction wave was
observed at a lower potential (EpcЈ = –1.02 V). However, in
this latter system the 1 e– reduction of the bipy unit destabi-
lizes the axle–wheel complex, which results in fast dethread-
ing of the axle from 1. For this reason, this first reduction
wave is irreversible and both the second system (E1/2Ј =
–1.13 V) and first oxidation peak (EpaЈ = –0.62 V) observed
Figure 2. Cyclic voltammograms of (a) T(C6), (b) P[1ʛT(C6)], and
(c) R[1ʛT(C6)] in CH2Cl2 + 0.5 m TBAP.[14] Scan rate: 100 mV/s.
Full line: no Zn2+, dashed line: 1 equiv. of Zn2+ added.
Scheme 3. Different behavior of (a) axle T(C6) and (b) R[1ʛT(C6)]
in the presence of an excess amount of Zn(TsO)2.
Eur. J. Org. Chem. 2012, 1033–1038
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A. Arduini, R. Bussolati, D. Masseroni, G. Royal, A. Secchi
Table 1. Electrochemical data of T(C6), P[1ʛT(C6)], R[1ʛT(C6)], and P[1ʛT(C12)] in the presence of Zn(TsO)2 (0–1 equiv.).[a,b]
FULL PAPER
Equiv.
0
T(C6)
P[1ʛT(C6)]
EpcЈ = –1.02
R[1ʛT(C6)]
P[1ʛT(C12)]
EpcЈ = –0.99
E
1/2Ј = –0.68
1/2ЈЈ = –1.17
E1/2Ј = –1.02
1/2ЈЈ = –1.42
E
EpaЈ = –0.62
E
EpaЈ = –0.59
E1/2ЈЈ = –1.13
E1/2ЈЈ = –1.08
1
E
E
1/2Ј = –0.69
1/2ЈЈ = –1.17
EpcЈ = –1.05
E
E
1/2Ј = –0.97
1/2ЈЈ = –1.40
EpcЈ = –0.99
EpaЈ = –0.62
EpaЈ = –0.59
E1/2ЈЈ = –1.13
E1/2ЈЈ = –1.08
[a] Volts vs. Ag+/Ag. Scan rate: 100 mV/s. [b] EЈ and EЈЈ correspond to the first and second electron transfer of the viologen unit,
respectively.
during the reverse scan are close to those observed for the duce a reciprocal exchange of chemical information among
free T(C6) axle (Figure 2b).
the different domains in both P[1ʛT(C6)] and R[1ʛT(C6)].
Upon addition of Zn2+ to the solution (0.5 to 3 equiv. as Studies to rationalize these effects and transfer these acqui-
TsO– salt),[13] no significant modification of the CV curve sitions to the construction of a new generation of metal–
was observed for the T(C6) axle, indicating that the com- organic rotaxane frameworks, in which these cascade effects
plexation of the metal ion has no influence on the redox can be applied to subtly tune properties and functions, are
behavior of the viologen unit. By contrast, in the case of undergoing in our laboratories.
the P[1ʛT(C6)] system, the presence of Zn2+ induced a
negative decay in the first reduction wave (–20 to –30 mV).
This shift could be interpreted by the fact that the dethread-
Experimental Section
ing process of the axle is more difficult to realize when Zn2+
General: Toluene and DMF were dried by using standard pro-
cedures. All other reagents were of reagent-grade quality, obtained
from commercial suppliers, and were used without further purifica-
is bound to the terpy unit. These results, together with the
UV/Vis data, suggest that the bipy core communicates
through the calixarene component with the terpy–Zn do-
main.
Quite unexpectedly, in the case of the 2R[1ʛT(C6)]/1Zn
rotaxane, a positive shift (up to +50 mV) of the two revers-
ible waves was observed. Again, the redox potential of the
bipy unit is affected, although in the opposite direction, by
the presence of the metal ion bound at the terpy unit. This
behavior could be tentatively explained by invoking a pos-
tion. 1H and 13C NMR spectra were recorded at 300 or 400 and
75 or 100 MHz, respectively. Chemical shifts are expressed in ppm
using the residual solvent signals as an internal reference. MS and
HRMS analyses were determined in the ESI mode with a Micro-
mass ZMD and a LTQ ORBITRAP XL Thermo, respectively.
Compounds 2,[16] 3,[17] 4,[18] 7,[6] and 8[19] were synthesized accord-
ing to literature procedures.
General Procedure for the Synthesis of 5 and 9: In a 250-mL, two-
sible steric effect exerted by the diphenylacetyl stopper that necked, round-bottomed flask, compound 3 (1.0 g, 4 mmol) and
KOH (0.7 g, 12 mmol) were dissolved in dry DMF (50 mL). The
resulting solution was stirred at room temperature for 20 min, and
then the appropriate ditosylate 4 or 8 (25.2 mmol) dissolved in dry
DMF (30 mL) was added. After stirring for 90 min at room tem-
perature, the reaction was quenched by the addition of water. The
white precipitate formed was recovered by suction filtration and
dissolved in ethyl acetate (30 mL). The organic phase was extracted
with 10% HCl (2ϫ20 mL). The combined aqueous extract was
adjusted to pH 8, and the white precipitate formed was extracted
with ethyl acetate (3ϫ15 mL). The organic phase was dried with
imposes a closer proximity of the wheel upper rim to the
terpy–Zn2+ stopper.[15] It could be hypothesized that, con-
trary to 2P[1ʛT(C6)]/1Zn where the Brownian motion of
the wheel could take place along both arms of the axle, the
conformational situation in 2R[1ʛT(C6)]/1Zn could result
in the protrusion of the bipy unit from the lower rim of the
calixarene that could thus be more easily reduced.
To verify whether these reduction potential variations of
the axle were the consequence of the proximity of the upper
rim of the wheel with the terpy unit, the T(C12) axle, where anhydrous Na2SO4, and the solvent was evaporated to dryness
under reduced pressure. The desired terpyridine was obtained pure
the span between the terpy unit and the 4,4Ј-bipy is 12 car-
bon atoms, was synthesized and then submitted to thread-
ing with 1 to yield P[1ʛT(C12)]. The CV behavior of
P[1ʛT(C12)] was similar to that observed for P[1ʛT(C6)],
however, no significant change in the CV curve was ob-
served for P[1ʛT(C12)] upon addition of Zn ions. This re-
sult clearly indicates that, in this system, the upper rim of
the wheel and the terpy–Zn unit no longer “communicate”
because of the increased distance.
after recrystallization from CH3CN as a white solid. Data for 5:
1
3
Yield: 1.0 g (50%). H NMR (300 MHz, CDCl3): δ = 8.69 (dd, J
4
= 4.5 Hz, J = 0.6 Hz, 2 H), 8.62 (d, J = 8.1 Hz, 2 H), 8.00 (s, 2
H), 7.9–7.7 (m, 4 H), 7.33 (m, 4 H), 4.18 (t, J = 6.3 Hz, 2 H), 4.05
(t, J = 6.3 Hz, 2 H), 2.43 (s, 3 H), 1.8–1.7 (m, 4 H), 1.5–1.4 (m, 4
H) ppm. 13C NMR (100 MHz, CDCl3): δ = 21.5, 25.0, 25.3, 28.7,
29.0, 67.8, 70.4, 107.3, 121.3, 123.7, 129.8, 136.7, 138.0, 144.3,
149.0, 156.2, 157.1, 167.2 ppm. MS (ESI): m/z (%) = 526 (100) [M
+ Na]+. M.p. 134–135 °C. Data for 9: 1.2 g (55%). 1H NMR
(300 MHz, CDCl3): δ = 8.70 (d, J = 4.5 Hz, 2 H), 8.62 (d, J =
7.8 Hz, 2 H), 8.05 (s, 2 H), 7.85 (t, J = 6.5 Hz, 2 H), 7.79 (d, J =
8.4 Hz, 2 H), 7.33 (m, 4 H), 4.23 (t, J = 6.3 Hz, 2 H), 4.02 (t, J =
6.3 Hz, 2 H), 2.44 (s, 3 H), 1.9–1.8 (m, 2 H), 1.8 (br. s, 2 H), 1.7–
1.6 (m, 2 H), 1.4–1.2 (m, 12 H) ppm. 13C NMR (100 MHz, CDCl3):
Conclusions
Taken all together, these data suggest that metal coordi-
nation, distance between binding sites, and orientation in- δ = 21.1, 24.9, 25.5, 28.4, 28.6, 28.9, 29.0, 29.1, 67.8, 70.4, 106.8,
1036 Eur. J. Org. Chem. 2012, 1033–1038
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Communication in Oriented Calixarene-Based Pseudorotaxanes and Rotaxanes
120.8, 123.6, 129.5, 136.7, 138.0, 144.3, 148.6, 155.5, 156.6, 25.8, 25.6, 25.5, 25.0, 19.9 ppm. MS (ESI): m/z (%) = 337 (100)
166.9 ppm. MS (ESI): m/z (%) = 610 (50) [M + Na]+. M.p. 99.5– [M – 2TsO]2+. M.p. 103.5–105.5 °C.
100.8 °C.
General Procedure for the Synthesis of P[1ʛT(C6)] and
General Procedure for the Synthesis of 6 and 10: In a 100-mL, two-
necked, round-bottomed flask, the appropriate terpyridine deriva-
tive 5 or 9 (1.4 mmol) and 4,4Ј-bipyridine (0.65 g, 4.2 mmol) were
dissolved in CH3CN (50 mL). The resulting solution was heated at
reflux for 2 d, then the solvent was evaporated under reduce pres-
sure. The sticky residue was triturated with ethyl acetate
(3ϫ20 mL) until the tosylate salt precipitated from the trituration
solvent. The solid was recovered by suction filtration and recrys-
P[1ʛT(C12)]: In a 50-mL, two-necked, round-bottomed flask,
calix[6]arene wheel 1 (0.15 g, 0.10 mmol) was dissolved in toluene
(20 mL) and compound T(C6) (0.10 g, 0.11 mmol) or T(C12)
(0.12 g, 0.11 mmol) was added. The solution assumed gradually a
deep-red color and it was stirred at room temperature for 30 min.
The solution was filtered, and the solvent was evaporated under
reduce pressure. The pseudorotaxane P[1ʛT(C6)] or P[1ʛT(C12)]
was obtained as a red solid. Data for P[1ʛT(C6)]: Yield: 0.23 g
1
tallized from CH3CN to afford product 6 or 10 as a white solid.
(95%). H NMR (300 MHz, C6D6): δ = 9.5 (br. s, 6 H), 8.93 (d, J
1
Data for 6: 0.8 g (85%). H NMR (300 MHz, CD3OD): δ = 9.11 = 7.8 Hz, 2 H), 8.73 (s, 2 H), 8.69 (d, J = 4.5 Hz, 2 H), 8.28 (d, J
(d, J = 5.1 Hz, 2 H), 8.76 (d, J = 3.3 Hz, 2 H), 8.65 (d, J = 3.3 Hz,
2 H), 8.59 (d, J = 6.0 Hz, 2 H), 8.45 (d, J = 4.8, 2 H), 7.98 (d, J =
6.9, 2 H), 7.89 (s, 2 H), 7.70 (d, J = 6.3 Hz, 2 H), 7.5–7.4 (m, 2 H),
= 7.5 Hz, 4 H), 8.1–8.0 (m, 10 H), 7.7–7.6 (m, 12 H), 7.46 (d, J =
7.8 Hz, 2 H), 7.2–7.1 (m, 6 H), 7.00 (d, J = 8.1 Hz, 4 H), 6.9–6.8
(m, 9 H), 4.66 (d, J = 14.7 Hz, 6 H), 4.03 (s, 9 H), 3.9–3.8 (m, 10
7.21 (d, J = 6.0 Hz, 2 H), 4.71 (t, J = 5.7 Hz, 2 H), 4.25 (t, J = H), 3.8–3.6 (m, 10 H), 3.5–3.4 (m, 12 H), 2.35 (br. s, 2 H), 2.06 (s,
4.5 Hz, 2 H), 2.34 (s, 3 H), 2.2–2.0 (m, 4 H), 1.7–1.5 (m, 4 H) ppm. 6 H), 1.9–1.6 (m, 32 H), 1.5–1.3 (m, 11 H), 1.1–0.9 (m, 4 H) ppm.
13C NMR (100 MHz, CD3OD): δ = 19.1, 25.1, 25.2, 28.2, 30.8, 13C NMR (100 MHz, C6D6): δ = 169.7, 157.6, 156.5, 152.9, 149.1,
61.2, 67.8, 106.9, 114.0, 121.5, 122.0, 124.1, 125.5, 125.6, 128.4, 138.9, 136.3, 133.8, 126.5, 123.5, 121.3, 121.0, 118.1, 116.7, 107.8,
137.3, 140.2, 142.0, 145.1, 148.6, 150.3, 153.0, 155.6, 156.8, 72.2, 69.9, 67.6, 66.5, 66.3, 59.7, 44.6, 39.2, 31.6, 31.3, 29.8, 29.2,
167.2 ppm. MS (ESI): m/z (%) = 488 (100) [M – TsO]+. M.p. 117– 26.9, 22.8, 20.8, 20.2, 15.1, 13.9 ppm. MS (ESI): m/z (%) = 1027
120 °C. Data for 10: Yield: 0.9 g (80%). 1H NMR (300 MHz,
(45) [M – 2TsO]2+. C141H165N11O20S2 (2398.04): calcd. C 70.62, H
CD3OD): δ = 9.08 (d, J = 7 Hz, 2 H), 8.80 (d, J = 5.0 Hz, 2 H), 6.94, N 6.43, S 2.67; found C 70.40, H 7.15, N 6.34, S 2.85. M.p.
8.65 (d, J = 3.3 Hz, 2 H), 8.59 (d, J = 7.8 Hz, 2 H), 8.47 (d, J = 152.7–154.1 °C. Data for P[1ʛT(C12)]: Yield: 0.25 g (95%). 1H
7 Hz, 2 H), 8.0–7.9 (m, 4 H), 7.93 (s, 2 H), 7.70 (d, J = 6.0 Hz, 2
H), 7.47 (t, J = 6.9 Hz, 2 H), 7.21 (d, J = 6.0 Hz, 2 H), 4.64 (t, J
= 5.7 Hz, 2 H), 4.23 (t, J = 4.5 Hz, 2 H), 2.35 (s, 3 H), 2.1–2.0 (m,
NMR (400 MHz, C6D6): δ = 9.5 (br. s, 6 H), 8.93 (d, J = 7.8 Hz,
2 H), 8.73 (m, 4 H), 8.28 (d, J = 7.5 Hz, 4 H), 8.1–7.9 (m, 10 H),
7.8–7.6 (m, 12 H), 7.5–7.4 (m, 2 H), 7.2–7.1 (m, 6 H), 7.00 (d, J =
4 H), 1.9–1.8 (m, 2 H), 1.6–1.5 (m, 2 H), 1.4–1.3 (m, 14 H) ppm. 8.1 Hz, 4 H), 6.95 (br. s, 2 H), 6.90–6.7 (m, 7 H), 4.66 (d, J =
13C NMR (100 MHz, CD3OD): δ = 19.9, 25.6, 25.8, 28.6, 28.7, 14.7 Hz, 6 H), 4.03 (s, 9 H), 4.0–3.9 (m, 10 H), 3.8–3.6 (m, 10 H),
28.9, 29.0, 29.1, 29.2, 31.2, 61.4, 68.1, 107.3, 121.6, 122.1, 124.1,
125.5, 125.7, 128.4, 137.3, 140.2, 142.2, 145.1, 148.6, 150.4, 153.6,
155.8, 156.9, 167.4 ppm. MS (ESI): m/z (%) = 573 (100) [M –
TsO]+. M.p. 91.5–93.5 °C.
3.5–3.4 (m, 12 H), 2.2 (br. s, 2 H), 2.1 (s, 6 H), 1.9–1.6 (m, 33 H),
1.5–1.3 (m, 25 H), 1.1–1.0 (m, 4 H) ppm. 13C NMR (100 MHz,
C6D6): δ = 167.6, 157.3, 156.5, 152.8, 149.0, 148.0, 144.2, 143.1,
136.2, 133.8, 132.2, 129.3, 128.7, 126.5, 124.8, 123.4, 121.1, 118.1,
116.7, 116.1, 107.8, 72.2, 69.9, 67.9, 66.3, 62.2, 61.0, 60.7, 34.6,
33.5, 31.5, 29.7, 29.6, 29.4, 29.2, 28.9, 26.1, 25.9, 20.8, 15.1 ppm.
HRMS: calcd. for [M – TsO]+ 2310.25249; found 2310.24756 (100).
M.p. 143.9–146.2 °C.
General Procedure for the Synthesis of T(C6) and T(C12): In a 100-
mL, two-necked, round-bottomed flask, compound 6 (0.85 g,
1.3 mmol) or 10 (0.96 g, 1.3 mmol) and compound 7 (0.35 g,
1.3 mmol) were dissolved in CH3CN (50mL), and the solution was
heated at refluxed for 10 d. Then the solvent was evaporated under
reduce pressure, and the residue obtained was triturated with
Synthesis of R[1ʛT(C6)]: In a 50-mL, two-necked, round-bottomed
flask P[1ʛT(C6)] (0.10 g, 0.04 mmol) was dissolved in toluene
EtOAc (3ϫ20 mL) until T(C6) and T(C12) precipitated from the (20 mL) and diphenylacetyl chloride (0.011 g, 0.05 mmol) and
trituration solvent. The solid was recovered by suction filtration
and purified by recrystallization from CH3CN to afford product
T(C6) or T(C12) as a white solid. Data for T(C6): Yield: 0.5 g
NEt3 (6.0 mg, 0.06 mmol) were added. The solution was stirred at
room temperature for 12 h. The solvent was then removed under
reduce pressure, and the crude solid was purified by flash
chromatography (CH2Cl2/CH3OH, 95: 5). Product R[1ʛT(C6)]
1
(41%). H NMR (300 MHz, CD3OD): δ = 9.30 (d, J = 5.1 Hz, 4
H), 9.20 (d, J = 8.2 Hz, 2 H), 8.70–8.61 (m, 8 H), 8.03 (d, J = was obtained as a red solid (0.05 g, 50%). 1H NMR (300 MHz,
9.3 Hz, 2 H), 7.89 (s, 2 H), 7.97 (s, 2 H), 7.70 (d, J = 8.1 Hz, 4 H), C6D6): δ = 9.5 (br. s, 6 H), 8.90 (d, J = 7.8 Hz, 2 H), 8.70 (s, 2 H),
7.52 (m, 2 H), 7.22 (d, J = 7.8 Hz, 4 H), 4.8–4.6 (m, 4 H), 4.30 (t, 8.67 (d, J = 4.2 Hz, 2 H), 8.25 (d, J = 7.5 Hz, 4 H), 8.1–7.9 (m, 10
J = 4.5 Hz, 2 H), 3.57 (t, J = 6.0 Hz, 2 H), 2.34 (s, 6 H), 2.2–2.1 H), 7.8–7.6 (m, 6 H), 7.50 (d, J = 7.2 Hz, 2 H), 7.5–7.4 (m, 2 H),
(m, 4 H), 2.0–1.9 (m, 4 H), 1.7–1.6 (m, 10 H) ppm. 13C NMR
(100 MHz, D2O): δ = 166.4, 155.5, 153.4, 148.5, 145.3, 145.0, 142.2,
139.5, 138.4, 129.3, 126.4, 126.2, 125.3, 125.0, 121.0, 107.4, 62.0,
61.9, 61.4, 30.9, 30.5, 30.3, 27.4, 25.0, 24.4, 20.4 ppm. MS (ESI):
7.2–7.1 (m, 12 H), 7.00 (d, J = 7.8 Hz, 4 H), 6.9–6.7 (m, 9 H), 5.20
(s, 1 H), 4.66 (d, J = 14.7 Hz, 6 H), 4.4–4.3 (m, 2 H), 3.99 (s, 9 H),
3.9–3.85 (m, 8 H), 3.8–3.6 (m, 10 H), 3.5–3.4 (m, 12 H), 2.1 (br. s,
2 H), 2.05 (s, 6 H), 1.88 (s, 2 H), 1.80 (s, 24 H), 1.7–1.5 (m, 6 H),
m/z (%) = 589 (45) [M – 2TsO – H]+, 294 (100) [M – 2TsO]2+. M.p. 1.2–1.1 (m, 11 H), 1.1–0.9 (m, 4 H) ppm. 13C NMR (100 MHz,
1
127–129 °C. Data for T(C12): 0.72 g (55%). H NMR (400 MHz,
CD3OD): δ = 9.14 (d, J = 4.1 Hz, 4 H), 8.6–8.4 (m, 8 H), 7.9–7.8
(m, 4 H), 7.67 (d, J = 8 Hz, 4 H), 7.4–7.3 (m, 2 H), 7.11 (d, J =
8 Hz, 4 H), 4.7–4.5 (m, 4 H), 4.2–4.1 (m, 2 H), 3.5–3.4 (m, 2 H),
C6D6): δ = 167.5, 157.5, 156.4, 153.0, 149.0, 148.0, 143.1, 142.9,
141.0, 139.5, 139.0, 137.5, 136.1, 133.7, 132.0, 126.4, 125.5, 123.4,
122.0, 121.0, 118.0, 116.7, 114.0, 107.7, 72.5, 69.9, 67.5, 67.0, 66.3,
61.0, 60.9, 59.0, 57.2, 50.0, 38.2, 34.5, 33.3, 32.6, 31.9, 31.5, 31.3,
2.26 (s, 6 H), 2.1–2.0 (m, 4 H), 1.9–1.8 (m, 2 H), 1.5–1.2 (m, 22 H) 29.8, 29.7, 29.4, 29.0, 28.9, 28.7, 28.6, 28.5, 28.0, 26.8, 22.7, 20.8,
ppm. 13C NMR (100 MHz, CD3OD): δ = 167.4, 156.9, 155.8,
149.6, 145.6, 142.2, 140.3, 137.3, 128.4, 126.9, 125.5, 124.1, 121.6,
20.2, 15.2, 14.0 ppm. MS (ES): m/z (%) = 1125 [M – 2TsO]2+
C155H175N11O21S2 (2592.27): calcd. C 71.82, H 6.80, N 5.94, S 2.47;
.
107.1, 68.1, 61.9, 61.2, 31.8, 31.1, 31.0, 29.2, 29.1, 29.0, 28.7, 28.6, found C 72.10, H 6.75, N 6.02, S 2.65. M.p. 157.7–159.3 °C.
Eur. J. Org. Chem. 2012, 1033–1038
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
1037

A. Arduini, R. Bussolati, D. Masseroni, G. Royal, A. Secchi
FULL PAPER
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aliquots of a solution (c = 2ϫ10–4 m in CH3Cl/CH3OH, 6:4) of
the titrant {T(C6) or R[1ʛT(C6)]} were added to a solution (c =
1ϫ10–5 m in CH3Cl/CH3OH, 6:4) of the Zn2+ salt contained in a
quartz cuvette (and vice versa, path length = 1 cm) and maintained
at 300 K through an external thermostat. The binding constants
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binding models[20] and sampling the spectroscopic data collected in
the 280–350 nm wavelength range.
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NMR Diffusion Experiments: DOSY experiments were carried out
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of at least six resonances present in the NMR spectrum of the
specie as a function of gradient strength applied to the sample.
The fitting of the attenuation profiles was carried out using the
equation:
[5]
[6]
–Dγ2g2δ2[Δ–(δ/3)–(τ/2)]
I = I0e
where I is the intensity of the observed resonance (attenuated), I0
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fusion coefficient, γ the gyromagnetic ratio, g the gradient strength,
δ the gradient pulse length, Δ the diffusion time, and τ the dephas-
ing and rephasing correction time. For each sample, 16 experiments
were carried out, in which the gradient strength g was varied from
5 to 95% of the maximum gradient intensity (5.35 G/mm).
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The symmetric shape of the first reduction wave is ascribed
to some adsorption phenomena of the axle onto the electrode
material.
Electrochemical Measurements: Electrochemical experiments were
conducted in a conventional three-electrode cell under an argon
atmosphere at 293 K by using a CH Instrument (CHI660B). Mea-
surements were done with solutions of the compounds (ca. 0.5 mm)
in CH2Cl2 containing tetra-n-butylammonium perchlorate (TBAP,
0.1 m) as supporting electrolyte. The reference electrode was Ag/
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1 μm diamond paste before each record and the counter electrode
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Supporting Information (see footnote on the first page of this arti-
cle): Full NMR characterization of new compounds T(C6),
T(C12), P[1ʛT(C6)], R[1ʛT(C6)], and P[1ʛT(C12)]; collection of
UV/Vis spectra for the titrations of zinc salts with T(C6) and
R[1ʛT(C6)]; cyclic voltammogram of P[1ʛT(C12)].
[13] In the presence of zinc, between 0.5 to 3 equiv. of Zn2+ added,
the respective shifts in the CV waves were not significantly de-
pendent from the terpy–metal stoichiometry.
[14] It should be noted that the electrochemical experiments were
carried out in the presence of a large amount of tetrabutylam-
monium perchlorate (TBAP) used as supporting electrolyte,
which minimizes the role of the TsO– anion in the binding pro-
cess and no significant changes in the voltammograms could
be observed when Zn(TsO)2 was replaced by the corresponding
Acknowledgments
–
This work was supported by the Italian Ministero dellЈUniversità
e della Ricerca (MIUR) (PRIN 2008HZJW2L). We thank CIM
(Centro Interdipartimentale di Misure) “G. Casnati” of the Univer-
sity of Parma for NMR spectroscopic measurements. We appreci-
ate Dr. P. Carrieri for technical support.
BF4 salt.
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Received: November 3, 2011
Published Online: December 9, 2011
1038
www.eurjoc.org
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2012, 1033–1038