cated by rather broad signals for both the Ag+ and Li+
precatenates. A purity of ca. 95% is estimated for the isolated
Table 2 Differential pulse data (vs. Ag/AgCl) in CH Cl containing 0.1 M
NBu PF
4 6
2
2
+
1
complex 7(Cu ) from its relatively simple H NMR spectrum
devoid of cis/trans isomerism). No significant changes in the
proton resonances of the macrocyclic unit were observed for the
E
ox1/V
+
E
ox2/V
+
(
+)
DEox1/V
(TTF· /TTF2+)
DEox2/V
Compound
(TTF· /TTF
2+
2+
isolated product containing Ni , indicating that the Ni -
precatenate had not been formed at all. This zero-yield is
probably a result of the reluctance of a Ni2 complex to adopt
the tetrahedral geometry enforced by the precatenate struc-
ture.
4
4
a
b
0.49
0.53
0.56
0.58
0.54
0.44
0.54
—
—
0.07
0.05
0.01
—
0.75
0.78
0.82
0.85
0.79
0.80
0.83
—
—
0.07
0.07
0.01
—
+
+ a
5a(Cu )
5b(Ag )
5b(Li )
6
+
+
Both MALDI and ESI mass spectrometry are useful tech-
niques for characterising precatenates of this type. Studies on
7
(Cu+)b
0.10
0.03
+
a
Eox(Cu
+/Cu2+) = 0.70 V.
b
Eox(Cu
+/Cu2+) = 0.69 V.
the Cu based precatenates show that an applicable amount of
the complex is transferred to the gas phase without dethreading.
+
+
Thus, the mass spectra of 5a(Cu ) and 7(Cu ) reveal a peak at
m/z 1291 (z = 1) which can be assigned to the singly charged
voltammetry. Thus, it seems that the precatenate is disrupted in
the relatively polar solvent (0.1 M NBu PF in CH Cl ) used for
+
2
4
6
2
2
Cu containing precatenate (without the BF
4
counter ion).
the electrochemical studies. In agreement with this observation,
However, fragmentation peaks corresponding to the dethreaded
+
Sauvage and coworkers found that the Li complex was
+
macrocycle with and without Cu are also seen.
6
+
unstable in the polar solvent DMF. For 7(Cu ) the first TTF
oxidation is significantly shifted, whereas the second is less
influenced.
The redox behaviour of the complexes was studied by cyclic
5
voltammetry and differential pulse voltammetry. The voltam-
+
mograms of the precatenate 5a(Cu ) (Fig. 1(a),(b)) show large
In conclusion, we have investigated the ability of TTF–
phenanthroline macrocycles to form precatenate complexes
with different metal ions. The appearance of large shifts in the
anodic shifts relative to the free macrocycle of both the first and
second TTF redox potentials as a result of the electrostatic
influence exerted by the metal ion (Table 2). In between the two
+
+
two TTF redox potentials for the Cu and Ag complexes
demonstrates the advantage of employing such macrocycles as
possible redox responsive sensors for transition metal ions.
+
2+
2+
TTF oxidations, Cu is oxidised to Cu . The generated Cu is
not expelled but maintained in the complex since the second
TTF oxidation is also affected by the presence of a positively
charged metal center. It is noteworthy that the cyclic voltammo-
+
gram of 5a(Cu ) shows the three redox processes to be
Notes and references
reversible.
†
4
2
Selected data for 6: d
H, H ), 8.35 (d, J 8.5 Hz, 2H, H4/7), 8.14 (d, J 8.5 Hz, 2H, H3/8), 7.82 (s,
H, H5/6), 7.22 (d, J 8.9 Hz, 4H, H ), 4.34 (t, J 4.9 Hz, 4H, OCH ), 3.85 (t,
), 3.79 (t, J 6.4 Hz, 4H, SCH ), 3.08 (t, J 6.4 Hz, 4H,
), 2.24 (s, 6H, SCH ); MS(PD): m/z 865 (M ). Calc. for
C40H36N O S : C, 55.53; H, 4.19; N, 3.24. Found: C, 55.33; H, 4.11; N,
H 3 3
(250 MHz, CDCl –CD CN 1+1): 8.46 (d, J 8.9 Hz,
+
For 5b(Ag ) the two TTF oxidations are also shifted to higher
potentials, which indicates that the Ag ion is also complexed
after the first TTF oxidation. However, even though the H
+
o
m
2
1
J 4.9 Hz, 4H, OCH
SCH
2
2
NMR spectrum in CDCl
for the formation of the 5b(Li ) precatenate, the TTF redox
3
–CD
3
CN (1+1) showed clear evidence
+
2
3
+
2
4 8
+
2
potentials were almost unaltered according to differential pulse
3.16%. For 7(Cu )BF
J 8.4 Hz, H4’/H7’), 8.53 (d, 2H, J 8.4 Hz, H
s, 2H, H /H ), 7.88 (d, 2H, J 8.6 Hz, H3’/H8’), 7.85 (d, 2H, J 8.6 Hz, H
.41 (d, 4H, J 8.6 Hz, Ho’), 7.26 (d, 4H, J 8.6 Hz, H ), 6.86 (s, 2H, OH), 5.98
d, 4H, J 8.6 Hz, Hm’), 5.97 (d, 4H, J 8.6 Hz, H ), 3.74 (t, 4H, J 6.2 Hz,
OCH ), 3.53 (2 3 t, 8H, J 5.0 Hz, OCH ), 3.26 (t, 4H, J 6.2 Hz, SCH ), 2.41
s, 6H, SCH ); MS(ES): m/z 1291 (M2BF
4
: d
H
(250 MHz, CDCl
3
–CD
), 8.24 (s, 2H, H5’/H6’), 8.05
/H ),
3
CN 1+1): d 8.63 (d, 2H,
4
/H
7
(
7
(
5
6
3
8
o
m
2
2
2
+
(
3
4
) .
1
T. Jørgensen, T. K. Hansen and J. Becher, Chem. Soc. Rev., 1994, 23, 41;
M. B. Nielsen and J. Becher, Liebigs Ann., 1997, 2177; R. Dieing, V.
Morrison, A. J. Moore, L. M. Goldenberg, M. R. Bryce, J.-M. Raoul,
M. C. Petty, J. Garín, M. Savirón, I. K. Lednev, R. E. Hester and J. N.
Moore, J. Chem. Soc., Perkin Trans. 2, 1996, 1587; F. Le Derf, M. Sallé,
N. Mercier, J. Becher, P. Richomme, A. Gorgues, J. Orduna and J. Garin,
Eur. J. Org. Chem., 1998, 1861; F. Le Derf, M. Mazari, N. Mercier, E.
Levillain, P. Richomme, J. Becher, J. Garín, J. Orduna, A. Gorgues and
M. Sallé, Chem. Commun., 1999, 1417; H. Liu, S. Liu and L. Echegoyen,
Chem. Commun., 1999, 1493.
2
C. O. Dietrich-Buchecker, P.A. Marnot and J.-P. Sauvage, Tetrahedron
Lett., 1982, 23, 5291; C. O. Dietrich-Buchecker and J.-P. Sauvage, Chem.
Rev., 1987, 87, 795.
3
4
5
T. Jørgensen, J. Becher, J.-C. Chambron and J.-P. Sauvage, Tetrahedron
Lett., 1994, 35, 4339.
Compound 3 was prepared according to a general procedure: M. B.
Nielsen, Z.-T. Li and J. Becher, J. Mater. Chem., 1997, 7, 1175.
For comparison to polymetallorotaxanes based on a bipyridine thiophene
backbone, see: S. S. Zhu and T. M. Swager, J. Am. Chem. Soc., 1997, 119,
1
2568.
6
C. Dietrich-Buchecker, J.-P. Sauvage and J.-M. Kern, J. Am. Chem. Soc.,
1989, 111, 7791.
Fig. 1 (a) Cyclic voltammogram (scan rate 100 mV s2 ) and (b) differential
1
+
2
pulse voltammogram of 4a (—) and 5a(Cu )BF
containing 0.1 M NBu PF
4
2 2
(····) in CH Cl
4
6
.
Communication a909320f
216
Chem. Commun., 2000, 215–216