ions to promote monodeprotonation and formation of the O–
H–O links. The nature of the diamine used in formation of
the macrocycle is less important, provided it can supply two
donors in cis geometry at each metal ion. In the present case the
pendant alcohol groups play no part in defining the geometry
of the complexes (although they are involved in intermolecular
hydrogen bonding). It should therefore be possible to vary the
nature of the diamine without altering the core structure of the
complex; hence it may be possible to build specific properties
into the sides of the guest-binding cleft in order to promote
reactivity at the dinuclear site. The dependence of the structure
on the oxidation state of the coordinated metal ion also suggests
that the 2,2ꢀ-methylenediphenol unit could be used as the basis
of a two-way conformational switch. Formation or opening of
the cleft could be driven by redox changes at the metal ion or by
pH changes.
Emerald green crystals of the solvate [Cu2(H4L)Cl]Cl·
1.6Et2O·EtOH (1a) were obtained by diethyl ether diffusion into
the filtrate.
[Zn2(H4L)Cl]Cl·H2O (2). Found: C 58.76, H 6.52, N 5.26.
Calc. for C52H68Cl2N4O7Zn2 (2): C 58.76, H 6.45, N 5.27%. IR
(KBr, cm−1): 3422 (s, br); 2963 (s); 1638 (s, m N); 1553 (w, mC O);
=
C
–
1
1479 (m); 1364 (m); 1220 (m). H NMR (CDCl3, 400 MHz)
=
ppm: 8.10 [s, 4H, N CH], 7.37 [d, 4H, ArH], 7.05 [d, 4H, ArH],
4.75 [d, 2H, Ar–CH2–Ar], 4.51 [d, 4H, NCH2], 4.25 [s (br), 2H,
CHOH], 3.75 [dd, 4H, NCH2], 3.55 [d, 2H, NCH2], 1.28 [s, 36H,
13
=
C(CH3)3]. C NMR (CDCl3, 400 MHz) ppm: 171.4 [C N],
157.1 [Ar–OH], 141.6 [Ar–tBu], 132.3 [C(Ar)H], 132.1 [Ar–
=
C N], 129.7 [C(Ar)H], 119.2 [Ar–CH2–Ar], 68.2 [NCH2], 67.9
[CH(OH)], 33.9 [Ar–CH2–Ar], 31.3 [C(CH3)3], 31.0 [C(CH3)3].
The complex was crystallised from ethanol solution by slow
diffusion of diethyl ether, yielding pale yellow crystals of
[Zn2(H4L)Cl]Cl·Et2O·0.5EtOH·0.55H2O (2a) after a few days.
Finally, it should be pointed out that strong hydrogen bonding
is not the only way of enforcing the hyperbolic paraboloid
conformation. We have previously reported that it is possible
to replace the pair of protons in the methylenediphenol groups
with a copper(II) ion coordinated to all four phenolate donors,
again with little change to the overall structure of the complex.15
[Ni2(H4L)Cl]Cl·4H2O (3). Found: C 56.57, H 6.50, N 4.70.
Calc. for C52H74Cl2N4O10Ni2 (3): C 56.60, H 6.76, N 5.08%. IR
(KBr, cm−1): 3383 (s, br); 2956 (s); 1634 (s, m N); 1551 (w, mC O);
=
C
–
1476 (m); 1364 (m); 1223 (m).
[Co2(H4L)(H2O)3](ClO4)2·2H2O (4). Found: C 50.01, H
5.63, N 4.29. Calc. for C52H76Cl2Co2N4O19 (4): C 49.96,
H 6.13, N 4.48%. IR (KBr, cm−1): 3423 (s, br); 2958 (s);
Conclusions
1630 (s, m N); 1560 (w, mC O); 1476 (m); 1436 (m); 1365
=
The conformations of dinuclear complexes of H6L are controlled
by the protonation level of the methylenediphenol units. The
protonation level depends on the oxidation state of the metal
ions and, in di-M(II) complexes strong O–H–O interactions hold
the macrocycle in a saddle-shaped conformation incorporating
a site for exogenous ligands to bridge the two metal ions.
Formally this sequence is akin to a cascade process;30,31 the
ligand binds two M(II) ions, this causes monodeprotonation
of the methylenediphenol groups and consequent assembly of a
cleft incorporating a binding site for anions or neutral molecules.
C
–
(m); 1223 (m); 1134 (s, m3(ClO4−)); 1117 (s, m3(ClO4−));
1088 (s, m3(ClO4−)); 626 (m, m4(ClO4−)). Yellow crystals of
[Co2(H4L)(H2O)(EtOH)2](ClO4)2·4EtOH (4a) were isolated by
slow evaporation of an ethanol solution of the compound.
[Ni2(H4L)(H2O)](ClO4)2·3H2O (5). Found: C 51.09, H 6.39,
N 4.26. Calc. for C52H72Cl2N4Ni2O17 (5): C 50.71, H 6.06,
N 4.55%. IR (KBr, cm−1): 3421 (s, br); 2959 (s); 1635 (s,
m
N); 1561 (w, mC O); 1476 (m); 1439 (m); 1365 (m); 1226
=
C
–
(m); 1107 (s, m3(ClO4−)); 624 (m, m4(ClO4−)). Pale green crystals
of [Ni2(H4L)(H2O)(EtOH)2](ClO4)2·4EtOH (5a) were obtained
directly from the reaction solution.
Experimental
[Ni2(H4L)(NO3)(H2O)2]NO3·H2O (6). Found: C 55.10, H
Synthesis
6.20, N 7.12. Calc. for C52H76N6Ni2O15 (6): C 54.86, H 6.37,
N 7.38. IR (KBr, cm−1): 3418 (ms); 2958 (s); 1634 (s, m N); 1560
2,2ꢀ-Dihydroxy-5,5ꢀ-di-tert-butyl-3,3ꢀ-methanediyl dibenzalde-
hyde (dhtmb). The precursor 2,2ꢀ-dihydroxy-5,5ꢀ-di-tert-butyl-
3,3ꢀ-methanediyldibenzyl alcohol was prepared from 4-tert-
butylphenol as a white crystalline solid following the litera-
ture procedure19 with some minor modifications. The alcohol
groups were oxidized to aldehyde by MnO2 oxidation after the
phenol groups had been protected using allyl bromide. The
allyl groups were then removed using 10% Pd on charcoal to
yield 2,2ꢀ-dihydroxy-5,5ꢀ-di-tert-butyl-3,3ꢀ-methanediyl diben-
zaldehyde (dhtmb) in 40% yield for the three step process.14,20
Found: C 74.51, H 7.86. Calc. for C23H28O4): C 74.97, H 7.66%.
=
C
(w, mC O); 1475 (m); 1384 (s, m3(NO3−); 1223 (m). Green crystals
–
of [Ni2(H4L)(NO3)(dmf)2]NO3·2dmf·H2O (6a) were obtained by
slow evaporation of a dmf solution of Ni2(H4L)(NO3)2(H2O)3:
dmf molecules replaced the coordinated water molecules.
[Zn2(H4L)(NO3)(H2O)2]NO3·3H2O (7). Found: C 54.01, H
6.19, N 7.87. Calc. for C52H72N6Zn2O15 (7): C 54.21, H 6.30, N
7.29%. IR (KBr, cm−1): 3426 (ms); 2957 (s); 1637 (s, m N); 1559
=
C
(w, mC O); 1475 (m); 1384 (s, m3(NO3−); 1221 (m). Pale yellow
–
crystals of [Zn2(H4L)(NO3)(EtOH)]NO3 (7a) suitable for X-ray
crystallography were obtained after a week.
IR (KBr, cm−1): 1658 (m O), 1270 (s, mAr OH), 1216 (s). 1H NMR
=
C
–
[Mn2(H2L)(Cl)2(EtOH)2]·6H2O (8). Found: C 54.99, H
(CDCl3, 400 MHz) ppm: 11.19 [s, 2H, Ar–OH], 9.86 [s, 2H,
CHO], 7.64 [d, 2H, ArH], 7.87 [d, 2H, ArH], 4.03 [s, 2H, Ar–
CH2–Ar], 1.29 [s, 18H, C(CH3)3].
7.39, N 4.94. Calc. for C56H88Cl2Mn2N4O14 (8): C 55.03, H 7.26,
N 4.59%. IR (KBr, cm−1): 3422 (s, br); 2958 (m); 1618 (s, m N);
=
C
1550 (m, mC O); 1439 (m); 1363 (w); 1309 (w); 1267 (m). Dark
–
The complexes were all prepared by template synthesis
in ethanol. In a typical preparation one equivalent of the
appropriate metal salt was dissolved in hot, dry ethanol along
with one equivalent of dhtmb and the solution brought to reflux.
One equivalent of 1,2-diaminopropan-2-ol in ethanol was added
and refluxing continued for 2 h. The products were generally
obtained on cooling the solution and reducing the volume.
Details for each of the complexes are available in the electronic
supplementary data.
brown crystals of [Mn2(H2L)(Cl)2(dmf)(dmso)]·1.5dmf·0.3Et2O
(8a) were obtained by slow diffusion of diethyl ether into a
solution of 8 in dmf–dmso.
X-Ray crystallography
Each data set was collected using a Bruker Smart 1000 CCD
diffractometer. The structures were solved using direct methods
and refined on F2 using all the data.32 Data collection and
refinement parameters are summarised in Table 3. Except as
specified below, all non-hydrogen atoms were refined with
anisotropic atomic displacement parameters. Hydrogen atoms
bonded to carbon were inserted at calculated positions using a
riding model and other hydrogen atoms were treated as described
[Cu2(H4L)Cl]Cl·2MeOH (1). Found: C 58.43, H 6.56, N
5.08. Calc. for C54H74Cl2Cu2N4O8 (1): C 58.68, H 6.75, N 5.07%.
IR (KBr, cm−1): 3421 (s, br); 2954 (s); 1626 (s, m N); 1560 (w,
=
C
mC O); 1474 (m); 1363 (m); 1221 (m).
–
D a l t o n T r a n s . , 2 0 0 5 , 9 2 3 – 9 2 9
9 2 7