Supramolecular [M4L4] tetrahedra based on triangular acylhydrazone catechol ligands

Article abstract of DOI:10.1002/ejoc.201101725

The ligands 1-H₆ and 2-H₆ are prepared by condensation of the triangular triamines 5 and 2,3-dihydroxybenzoic acid hydrazide 7. The ligands form container-type tetrahedral coordination compounds M_x [(1 or 2)₄M′<

Full text of DOI:10.1002/ejoc.201101725

FULL PAPER
DOI: 10.1002/ejoc.201101725
Supramolecular [M4L4] Tetrahedra Based on Triangular Acylhydrazone
Catechol Ligands
Markus Albrecht,*[a] Yuli Shang,[a] Tanja Rhyssen,[a] Jan Stubenrauch,[a]
Henrik D. F. Winkler,[b] and Christoph A. Schalley[b]
Keywords: Cage compounds / Ligand design / Self-assembly / Gallium / Titanium / Hydrazones
The ligands 1-H6 and 2-H6 are prepared by condensation of
the triangular triamines 5 and 2,3-dihydroxybenzoic acid hy-
drazide 7. The ligands form container-type tetrahedral coor-
dination compounds Mx [(1 or 2)4MЈ4] (M = Li, Na, K; MЈ =
Ti, x = 8; MЈ = Ga, x = 12). The complexes are characterized
by NMR spectroscopy and ESI mass spectrometry. Despite
the relatively labile acyl hydrazone unit, the complexes show
high stability in water. Ligand 3-H6 is prepared from the tris-
acyl hydrazide 8 and 2,3-dihydroxybenzaldehyde 9 but does
not form well-defined coordination compounds with galli-
um(III) or titanium(IV) ions.
to encapsulate guests.[4] Thus, ligand D was designed. This
compound forms a very large tetrahedron that accommo-
dates different guest species in its interior. The connecting
imine units are easily formed by condensation of an alde-
hyde with an amine, but their instability in protic solvents
limits the use of ligand D.[5]
Introduction
Container molecules are of immerging importance due
to their ability to form inclusion complexes in which highly
reactive species are stabilized or chemical reactions are cata-
lyzed. Molecular containers are formed either through co-
valent approaches or can be obtained by noncovalent self-
assembly through hydrogen bonding or metal coordination.
The latter approach, especially, results in easily accessible,
stable compounds.[1] Spectacular examples in this field are
the cages described by Fujita[2] or the [M4L6] tetrahedron
described by Raymond, which is formed from six biscate-
chol ligands and four gallium(III) ions.[3]
An efficient approach to [M4L4] metallosupramolecular
tetrahedra is the coordination of four triangular ligands to
four metal centers. The ligands span the faces of the tetra-
hedron while the metals are located on the corners of the
polyhedron (Figure 1). This approach was first exemplified
by use of the ligands A–C (Figure 2). However, the obtained
compounds did not provide an internal cavity with which
Figure 1. Self assembly of [M4L4] supramolecular tetrahedra from
triangular ligands and appropriate metal ions.
Figure 2. Triangular ligands that form [M4L4] supramolecular tet-
rahedra.
[a] Institut für Organische Chemie,
Landoltweg 1, 52074 Aachen, Germany
Different approaches can be envisaged to obtain more
stable ligands.[6] In this study, the imine unit of D has been
substituted and the related acyl hydrazone connected tris-
catechol ligands were prepared.[7] The preparation of the
ligands 1-H6–3-H6 (Figure 3) and their coordination chem-
E-mail: markus.albrecht@oc.rwth-aachen.de
[b] Institut für Chemie und Biochemie, Organische Chemie, Freie
Universität Berlin,
Takustr. 3, 14195 Berlin, Germany
Supporting information for this article is available on the
WWW under http://dx.doi.org/10.1002/ejoc.201101725.
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© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2012, 2422–2427

Supramolecular [M4L4] Tetrahedra
istry with titanium(IV) and gallium(III) ions is described.
The molecular tetrahedra obtained are characterized by
NMR spectroscopy as well as ESI mass spectrometry.
Figure 3. Ligands synthesized in this study. Only one of the
catechol bearing acylhydrazone side arms connected to the C3 sym-
metric central nitrogen (1-H6) or arene (2-H6, 3-H6) unit is shown.
Results and Discussion
Preparation of Ligands 1-H6, 2-H6 and 3-H6
In 1-H6 a central amine bearing the three side-chains ter-
minated by catechol units introduces the idealized C3 sym-
metry. In 2-H6 and 3-H6, 1,3,5-substituted arenes act as a
C3-symmetric backbone. Ligands 1-H6 and 2-H6 are based
on acyl hydrazones formed from the hydrazide of 2,3-dihy-
droxybenzoic acid and a central triangular trisaldehyde. In
3-H6 the situation is reversed, with the acyl unit connected
to the central backbone and the hydrazone bound to the
catechol.
Scheme 1. Preparation of ligands 1-H6 and 2-H6.
For the hydrazone condensation to obtain ligands 1-H6
and 2-H6, building blocks 5a, 5b and 7 were required. The
trisaldehydes 5a and 5b were obtained by halogen–metal
exchange of the corresponding bromides 4a and 4b using
tBuLi in diethyl ether at –78 °C. The intermediate organo-
metallic species were quenched with N,N-dimethylform-
amide (DMF) to give the desired derivatives in 46 (5a) or
82% (5b) yield, respectively.[8] Reaction of methyl 2,3-dihy-
droxybenzoate (6) with hydrazine hydrate in methanol re-
sulted in the formation of acylhydrazine 7 in 87% yield.
Due to precipitation of the product, the selection of appro-
priate solvents in the final condensation step was crucial for
success. The amine-based ligand 1-H6 was obtained from
ethanol in 42%, whereas 2-H6 formed in methanol/di-
chloromethane in 64% (Scheme 1).
Scheme 2. Preparation of ligands 3-H6.
Coordination Studies to Obtain Metallosupramolecular
Tetrahedra of 1-H6, 2-H6 and 3-H6 with Titanium(IV) and
Gallium(III) Ions
The obtained compounds were characterized by stan-
dard techniques. For example, 1-H6 gave rise to the ex-
1
pected, characteristic signals in its H NMR spectrum (re-
corded in [D6]DMSO).
Coordination compounds of ligands 1-H6–3-H6 were
The synthesis of ligand 3-H6 is depicted in Scheme 2. prepared either from 1:1:1 mixtures of the ligand, titanoyl
1,3,5-Benzenetricarboxylic acid could be easily transformed bisacetylacetonate [TiO(acac)2] and alkali metal carbonate,
into the ester and subsequently into hydrazide 8,[9] which or from 1:1:1.5 mixtures of ligand, gallium trisacetylaceton-
was condensed with 2,3-dihydroxybenzaldehyde 9 to form ate [Ga(acac)3] and alkali metal carbonate in DMF as sol-
trishydrazone 3-H6 in 65% yield. The reaction was per- vent (Scheme 3). During the reaction, the colour of the
formed in ethanol containing traces of acetic acid. Deriva- solution turned red (Ti) or yellow (Ga), indicating the for-
1
tive 3-H6 gave rise to a characteristic H NMR spectrum.
mation of complexes. With ligands 1-H6 and 2-H6, the de-
Eur. J. Org. Chem. 2012, 2422–2427
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M. Albrecht et al.
FULL PAPER
sired [M4L4] complexes could be isolated, with the excep-
tion of Li12[(1)4Ga4] and Li8[(2)4Ti4]. The latter are proba-
bly minor components within a complex mixture of species.
Complexes Li12[(2)4Ga4] and Na12[(2)4Ga4] could be char-
acterized by spectroscopic techniques, but were not ob-
tained in analytically pure form. It has to be mentioned
that, due to the large cavities, all complexes contained large
amounts of solvents. Rigorous drying resulted in decompo-
sition (probably oligomerization) of the cages and only in-
soluble materials were obtained. The high content of sol-
vent in the crystal was certainly a drawback in obtaining
X-ray crystal structures. Although nice single crystals were
obtained, we were not able to record sufficient numbers of
reflections for the solution of a structure. Ligand 3-H6 did
not afford characterizable derivatives. In this case, probably
polymeric or oligomeric compounds were formed.
1
Figure 4. H NMR spectra of 1-H6 (a) and M8[(1)4Ti4] with M =
Li (b), Na (c) or K (d) in [D6]DMSO.
Scheme 3. Self-assembly of [M4L4] tetrahedra.
1
Figure 4 shows the H NMR spectra of ligand 1 and of
its titanium(IV) complexes in [D6]DMSO. All signals are
significantly shifted upon coordination of titanium(IV),
whereas no remarkable differences are found in the spectra
obtained with different alkali metal counterions. The down-
field shifting of the hydrazone CONH-signal is indicative
for formation of a hydrogen bond to the internal oxygen
atom of the titanium coordinated catechols.
Figure 5. ESI MS of Li8[(1)4Ti4].
ESI MS is a powerful tool to reveal the composition of
charged supramolecular aggregates.[10] A representative ex-
ample the spectrum of Li8[(1)4Ti4] in methanol is shown in
Figure 5. The dominating peaks at m/z = 822.7 and 1097.2
are assigned to {H4[(1)4Ti4]}4– and {H5[(1)4Ti4]}3–, respec-
tively. The sodium Na8[(1)4Ti4] and the potassium salt
K8[(1)4Ti4] also show characteristic signals in their ESI MS
spectra.
Figure 6. 1H NMR spectra of 1-H6 (a) and Na12[(1)4Ga4] (b) in
[D6]DMSO.
Negative ESI MS sprayed from methanol reveals charac-
Similar results to those obtained for titanium(IV) were teristic signals for the tetrahedral tetranuclear metal com-
obtained with gallium(III). As a representative example, the plexes, for example, at m/z = 1134.7 {H8Na[(1)4Ga4]}3– and
1H NMR spectrum of Na12[(1)4Ga4] and the free ligand are 1127.2 {H9[(1)4Ga4]}3–. In addition, peaks are detected that
compared in Figure 6. Again, a characteristic shift of the indicate that methanol is strongly attached to the container
NH resonance to higher ppm values is observed due to the (e.g., m/z = 1152.7 {H7Na2[(1)4Ga4]MeOH}3–). The solvent
intramolecular hydrogen bond. The corresponding potas- molecules are probably encapsulated in the interior of the
sium salt K12[(1)4Ga4] leads to a very similar spectrum.
cavity.
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© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2012, 2422–2427

Supramolecular [M4L4] Tetrahedra
The coordination studies with ligand 2-H6 resulted in the 2-H6 are good candidates for the self-assembly of metallo-
formation of related titanium(IV) or gallium(III) metallosu- supramoecular tetrahedra. According to our design, ligands
pramolecular tetrahedra that were characterized by 1H 1-H6 and 2-H6 form the corresponding complexes Mx[(1/2)4-
NMR and ESI MS analyses. As a representative example, (Ti/Ga)4], which can be characterized by NMR and ESI
1
the H NMR spectrum of Na8[(2)4Ti4] is compared to the MS analyses . MS as well as elemental analyses show that
corresponding ligand spectrum in Figure 7 (due to different the containers are able to uptake solvent molecules. Unfor-
solubility of the compounds the spectra were recorded in tunately, so far it was not been possible to observe the in-
different solvents). Again, a downfield shift of the NH pro- clusion of added guest species, but the described results
ton is observed due to intramolecular hydrogen-bonding.
indicate that the containers are filled with solvent molecules
and probably with counter cations. The compounds show
high stability in water. Use of ligand 3-H6 does not result
in tetrahedral coordination compounds. In this case, as a
working hypothesis, we assume that repulsion between the
lone pair of the hydrazone nitrogen atom and of the coordi-
nated catechol oxygen atom prevents formation of the de-
sired complexes.
The introduction of hydrazone linkages in this chemistry
paves the way to ligands that are easily generated and that
lead to complexes with high stability even in water.
Experimental Section
General: NMR spectra were recorded with a Varian Mercury 300
spectrometer. FTIR spectra were recorded with a Bruker IFS spec-
trometer. Mass spectra were recorded with a Thermo Deca XP
mass spectrometer. Elemental analyses were obtained with a
Heraeus CHN-O-Rapid analyser. Compounds 4a, 4b,[8] and 8[9]
were prepared following literature procedures.
Figure 7. 1H NMR spectra of 2-H6 in [D6]DMSO (a) and
Na8[(2)4Ti4] in CD3OD (b).
The composition of the complexes is again revealed by
ESI MS studies (methanol); for example, characteristic
peaks are observed at m/z = 905.63 {Na4[(2)4Ti4]}4–, 917.5
{H6Li2[(2)4Ga4](MeOH)4}4–, or 941.55 {H3Na5[(2)4Ga4]-
(MeOH)}4–.
The water stability of the tetrahedral complexes of ligand
1 and 2 with titanium(IV) or gallium(III) was tested. To
this end, the complexes were dissolved in D2O and 1H
NMR spectra were measured. Well-resolved resonances of
the container molecules were obtained (Figure 8 shows as
representative example the spectra of K8[(2)4Ga4]). The
measurement of the sample was frequently repeated over
the time period of one week and no change in the spectra
was observed. This experiment demonstrates the long-term
stability of the complexes in water at ambient temperature.
General Procedure for the Preparation of Aldehydes 5a and 5b: A
solution of tBuLi (1.5 M in pentane, 12.5 mL, 6 equiv.) was added
dropwise to a solution of bromide 4a or 4b (3 mmol, 1 equiv.) in
anhydrous solvent (a: diethyl ether; b: THF; 30 mL) precooled to
–78 °C under N2. The reaction mixture was stirred at this tempera-
ture for 1 h followed by dropwise addition of anhydrous DMF
(1.4 mL, 6 equiv.). The reaction suspension was allowed to reach
room temperature and stirred for 2 h. The reaction was quenched
by the slow addition of saturated NH4Cl. After evaporation of or-
ganic solvent, the aqueous phase was exacted with dichlorometh-
ane (3ϫ20 mL). The combined organic extracts were dried
(Na2SO4), evaporated to dryness and purified by silica column
chromatography (5a: hexane/ethyl acetate, 1:1; 5b: dichlorometh-
ane/ethyl acetate, 10:1) to obtain 5a (46%) or 5b (82%) as white
solids.
Compound 5a: 1H NMR (300 MHz, [D6]DMSO): δ = 9.94 (s, 3 H),
7.91 (AAЈBBЈ, J = 8.7 Hz, 6 H), 7.28 (AAЈBBЈ, J = 8.7 Hz, 6
H) ppm. MS (EI, 70 eV): m/z (%) = 329.1 (100) [M]+.[8]
Compound 5b: 1H NMR (300 MHz, CDCl3): δ = 10.04 (s, 3 H),
7.96 (AAЈBBЈ, J = 8.4 Hz, 6 H), 7.84 (s, 3 H), 7.81 (AAЈBBЈ, J =
8.4 Hz, 6 H) ppm.[8]
1
Synthesis of 7: Ester 6 (345 mg, 2 mmol) was dissolved in methanol
(30 mL), and 98% hydrazine solution (0.4 mL, 8 mmol) was added
to the reaction mixture, which was heated to reflux overnight. The
mixture was concentrated and EtOAc was added. After storage in
a refrigerator for 3 d, a white precipitate was obtained that was
filtered and dried under vacuum; yield 269 mg (1.6 mmol, 78%).
1H NMR (300 MHz, CD3OD): δ = 7.18 (dd, J = 7.9, 1.5 Hz, 1 H),
6.91 (dd, J = 7.9, 1.5 Hz, 1 H), 6.70 (t, J = 7.9 Hz, 1 H) ppm. MS
Figure 8. H NMR spectrum of K8[(2)4Ga4] in D2O.
Conclusions
In this study, the preparation of triangular triscatechol
ligands based on acylhydrazone linkages was described. The
ligands are readily available, however, only ligands 1-H6 and (EI, 70 eV): m/z (%) = 168.1 (25.7) [M]+.
Eur. J. Org. Chem. 2012, 2422–2427
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2425

M. Albrecht et al.
FULL PAPER
Synthesis of 1-H6: Compounds 7 (164 mg, 0.99 mmol) and 5a
(80 mg, 0.24 mmol) were dissolved in ethanol (90 mL) and heated
to reflux for 7 d. The solvent was evaporated and the residue was
heated to reflux in methanol for 1 h. The product 1-H6 was col-
lected by filtration; yield 76.8 mg (0.10 mmol, 42%); m.p. 245 °C.
1H NMR (300 MHz, [D6]DMSO): δ = 11.93 (s, 3 H), 11.84 (s, 3
H), 9.34 (s, 3 H), 8.45 (s, 3 H), 7.73 (d, J = 8.4 Hz, 6 H), 7.37 (d,
J = 7.5 Hz, 3 H), 7.17 (d, J = 8.4 Hz, 6 H), 6.97 (d, J = 7.5 Hz, 3
H), 6.78 (t, J = 7.5 Hz, 3 H) ppm. MS (ESI–): m/z = 778.13 [M –
C
168H108N28O36Ti4Na8·12DMF·16H2O: C 52.86, H 4.87, N 12.09;
found C 52.94, H 5.36, N 12.05.
K8[(1)4Ti4]: Yield quant. 1H NMR (300 MHz, [D6]DMSO): δ =
13.14 (s, 12 H), 8.00 (s, 12 H), 7.20 (d, J = 7.2 Hz, 24 H), 7.13 (d,
J = 7.8 Hz, 12 H), 6.87 (d, J = 7.2 Hz, 24 H), 6.49 (t, J = 7.8 Hz,
12 H), 6.32 (d, J = 7.8 Hz, 12 H) ppm. MS (ESI–): m/z = 886.5
{K [(1) Ti ](MeOH)(H O) }4–. IR (KBr): ν = 3396, 2975, 2881,
˜
4
4
4
2
4
1650, 1592, 1548, 1500, 1464, 1438, 1383, 1322, 1281, 1245, 1213,
1177, 1148, 1076, 1054, 1007, 955, 933, 885, 852, 814, 742,
670 cm–1. C168H108N28O36Ti4K8·9DMF·27H2O: C 49.38, H 4.78,
N 10.93; found C 49.39, H 4.73, N 10.97.
H]–. IR (KBr): ν = 3234, 3068, 1639, 1591, 1501, 1456, 1318, 1263,
˜
1169, 1078, 987, 962, 939, 836, 800, 737 cm–1. C42H33N7O9·3H2O:
C 60.50, H 4.71, N 11.76; found C 60.77, H 4.50, N 11.76.
Na8[(2)4Ti4]: Yield quant. 1H NMR (300 MHz, CD3OD): δ = 13.48
(s, 12 H), 7.91 (s, 12 H), 7.71 (s, 12 H), 7.62 (d, J = 7.9 Hz, 24 H),
7.55 (d, J = 7.9 Hz, 24 H), 7.36 (m, 12 H), 6.62 (m, 24 H) ppm. 1H
NMR (300 MHz, D2O): δ = 7.99 (s, 12 H), 7.91 (s, 12 H), 7.65 (m,
48 H), 7.44 (d, J = 8.1 Hz, 12 H), 6.89 (t, J = 8.1 Hz, 12 H), 6.79
(d, J = 8.1 Hz, 12 H) ppm. MS (ESI–): m/z = 905.63 {Na4-
Synthesis of 2-H6: To a solution of hydrazide 7 (90 mg, 0.53 mmol)
in methanol (20 mL) was added a solution of aldehyde 5b (52 mg,
0.13 mmol). The mixture was heated to reflux for 2 d and then
cooled to room temperature. From the resulting suspension, a white
precipitate formed slowly during the next two weeks that was fil-
tered and dried under vacuum; yield 71 mg (0.08 mmol, 64%); m.p.
226. 1H NMR (300 MHz, [D6]DMSO): δ = 11.94 (s, 3 H), 11.82 (s,
3 H), 9.39 (s, 3 H), 8.56 (s, 3 H), 8.08 (m, 9 H), 7.91 (m, 6 H), 7.38
(d, J = 7.8 Hz, 3 H), 6.99 (d, J = 7.8 Hz, 3 H), 6.78 (t, J = 7.8 Hz,
[(2) Ti ]}4–, 909.63 {Na K[(2) Ti ]}4–. IR (KBr): ν = 3473, 2928,
˜
4
4
3
4
4
2879, 2325, 2111, 1652, 1602, 1542, 1507, 1464, 1439, 1385, 1353,
1287, 1245, 1213, 1145, 1080, 1055, 1009, 934, 887, 853, 826, 801,
742, 668 cm–1. C192H120N24O36Ti4Na8·11DMF·10H2O: C 57.51, H
4.65, N 10.43; found C 57.66, H 4.29, N 10.35.
3 H) ppm. MS (ESI–): m/z = 839.1 [M – H]+. IR (KBr): ν = 3426,
˜
3261, 3033, 2322, 2106, 1640, 1597, 1545, 1456, 1369, 1317, 1229,
1159, 1075, 1018, 983, 940, 880, 822, 798, 735 cm–1.
C48H36N6O9·2H2O: C 65.75, H 4.60, N 9.58; found C 65.82, H
4.47, N 9.51.
General Procedure for the Preparation of Gallium(III) Complexes:
A mixture of ligand (1 equiv.), [Ga(acac)3] (1 equiv.) and M2CO3
(M = Na, K; 1 equiv.) in DMF (50 mL) were stirred overnight at
room temperature. The solvent was removed and the complex was
obtained as a red solid.
Synthesis of 3-H6: 1,3,5-Benzenetricarbohydrazide
8 (504 mg,
2.0 mmol) and 2,3-dihydroxybenzaldehyde 9 (912 mg, 6.6 mmol)
were dissolved in ethanol (150 mL). After addition of acetic acid
(ca. 1 mL) the mixture was heated at reflux for 24 h. The white
precipitate was filtered, washed with ethanol and dried in vacuo.
Ligand 3-H6 (787 mg, 1.3 mmol, 65%) was obtained as a white
powder. 1H NMR (300 MHz, [D6]DMSO): δ = 12.42 (s, 3 H), 10.97
(s, 3 H), 9.27 (s, 3 H), 8.71 (s, 3 H), 8.64 (s, 3 H), 7.00 (dd, J = 7.7,
1.2 Hz, 3 H), 6.86 (dd, J = 7.7, 1.2 Hz, 3 H), 6.74 (t, J = 7.7 Hz, 3
H) ppm. 13C NMR (300 MHz, [D6]DMSO): δ = 162.0 (C), 149.5
(CH), 146.1 (C), 145.7 (C), 133.7 (C), 130.1 (CH), 119.9 (CH),
119.3 (CH), 118.9 (C), 117.6 (CH) ppm. MS (ESI–): m/z = 610.99
[M – H]–.
Na12[(1)4Ga4]: Yield 97%. 1H NMR (300 MHz, [D6]DMSO): δ =
14.94 (s, 12 H), 7.94 (s, 12 H), 7.19 (m, 24 H), 6.80 (m, 36 H), 6.30
(m, 12 H), 6.16 (m, 12 H) ppm. MS (ESI–): m/z = 1127.70
{H9[(1)4Ga4]}3–, 1134.70 {H8Na[(1)4Ga4]}3–, 1137.70 {H9[(1)4Ga4]-
(MeOH)}3–, 1145.03 {H8Na[(1)4Ga4](MeOH)}3–, 1147.69 {H9[(1)4-
Ga4](MeOH)2}3–, 1152.69 {H7Na2[(1)4Ga4](MeOH)}3–. IR (KBr):
ν = 3377, 3058, 2928, 2885, 1652, 1590, 1545, 1499, 1468, 1439,
˜
1384, 1356, 1322, 1281, 1210, 1176, 1144, 1061, 1004,
954,
168H108N28O36Ga4Na12·14DMF·22H2O: C 49.76, H 4.97,
11.60; found 49.73, H 5.34, N 11.25.
933,
886,
852,
831,
811,
735,
662 cm–1.
C
N
General Procedure for the Preparation of Titanium(IV) Complexes:
Ligand (1 equiv.), [TiO(acac)2] (1 equiv.) and M2CO3 (M = Na, K,
Li; 1 equiv.) were dissolved in DMF (50 mL) and stirred overnight.
After evaporation of the solvent a red solid was obtained.
K12[(1)4Ga4]: Yield quant. 1H NMR (300 MHz, [D6]DMSO): δ =
14.90 (s, 12 H), 7.94 (s, 12 H), 7.18 (m, 24 H), 7.02 (m, 12 H), 6.82
(m, 24 H), 6.50 (m, 12 H), 6.28 (m, 12 H) ppm. MS (ESI–): m/z =
1127.35 {H9[(1)4Ga4]}3–, 1137.67 {H9[(1)4Ga4](MeOH)}3–, 1147.34
Li8[(1)4Ti4]: Yield quant. 1H NMR (300 MHz, [D6]DMSO): δ =
13.16 (s, 12 H), 8.00 (s, 12 H), 7.22 (d, J = 7.0 Hz, 24 H), 7.14 (d,
J = 7.7 Hz, 12 H), 6.87 (d, J = 7.0 Hz, 24 H), 6.54 (t, J = 7.7 Hz,
12 H), 6.34 (d, J = 7.7 Hz, 12 H) ppm. MS (ESI–): m/z = 822.67
{KNaH [(1) Ga ]}3–. IR (KBr): ν = 3376, 3058, 2931, 2883, 1655,
˜
7
4
4
1591, 1545, 1499, 1467, 1441, 1383, 1356, 1321, 1282, 1210, 1176,
1144, 1060, 1003, 954, 932, 885, 852, 831, 809, 736, 662 cm–1.
C168H108N28O36Ga4K12·14DMF·12H2O: C 49.63, H 4.56, N 11.57;
found C 49.98, H 5.04, N 11.38.
{H [(1) Ti ]}4–, 1097.24 {H [(1) Ti ]}3–. IR (KBr): ν = 3284, 3062,
˜
4
4
4
5
4
4
2972, 2934, 1653, 1591, 1546, 1500, 1465, 1439, 1382, 1321, 1280,
1215, 1176, 1150, 1077, 1055, 1009, 955, 935, 885, 851, 815, 742,
672 cm–1. C168H108N28O36Ti4Na8·14DMF·17H2O: C 53.99, H 5.18,
N 12.59; found C 54.15, H 5.51, N 12.24.
K12[(2)4Ga4]: Yield quant. 1H NMR (300 MHz, CD3OD): δ = 7.87
(s, 12 H), 7.71 (s, 12 H), 7.62 (m, 24 H), 7.54 (m, 24 H), 7.18 (d, J
= 8.1 Hz, 12 H), 6.72 (d, J = 7.5 Hz, 12 H), 6.40 (d, J = 7.5 Hz,
12 H) ppm. 1H NMR (300 MHz, D2O): δ = 7.96 (s, 12 H), 7.76 (s,
12 H), 7.61 (m, 48 H), 7.24 (d, J = 7.8 Hz, 12 H), 6.85 (d, J =
7.8 Hz, 12 H), 6.64 (t, J = 7.8 Hz, 12 H) ppm. MS (ESI–): m/z =
Na8[(1)4Ti4]: Yield quant. 1H NMR (300 MHz, [D6]DMSO): δ =
13.14 (s, 12 H), 7.95 (s, 12 H), 7.21 (d, J = 7.5 Hz, 24 H), 7.14 (d,
J = 7.9 Hz, 12 H), 6.86 (d, J = 7.5 Hz, 24 H), 6.50 (t, J = 7.9 Hz,
12 H), 6.33 (d, J = 7.9 Hz, 12 H) ppm. MS (ESI–): m/z = 1097.24
{H5[(1)4Ti4]}3–, 1104.16 {H4Na[(1)4Ti4]}3–, 1130.55 {H2Na3[(1)4-
Ti4](H2O)2}3–, 1135.87 {H2Na2K[(1)4Ti4](H2O)2}3–, 1746.84
{H3Na3[(1)4Ti4](MeOH)2(H2O)4}2–, 1754.83 {H3Na2K[(1)4Ti4]-
1261.18 {K H [(2) Ga ](MeOH) (H O)}3–. IR (KBr): ν = 3417,
˜
2
7
4
4
2
2
2925, 2884, 2322, 2114, 1653, 1541, 1507, 1467, 1440, 1386, 1352,
1290, 1259, 1209, 1143, 1061, 1004, 934, 887, 855, 825, 799, 738,
661 cm–1. C192H120N24O36Ga4K12·12DMF·15H2O:
C 52.31, H
4.51, N 9.63; found C 52.32, H 4.75, N 9.58.
(MeOH) (H O) }2–. IR (KBr): ν = 3290, 2932, 1652, 1592, 1547,
˜
2
2
4
1501, 1464, 1439, 1384, 1323, 1281, 1247, 1215, 1177, 1146, 1078,
Supporting Information (see footnote on the first page of this arti-
cle): H NMR spectra of ligands and complexes.
1054, 1008, 955, 933, 886, 852, 815, 743, 671 cm–1.
1
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© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Eur. J. Org. Chem. 2012, 2422–2427

Supramolecular [M4L4] Tetrahedra
6916; g) M. D. Pluth, R. G. Bergman, K. N. Raymond, J. Am.
Chem. Soc. 2008, 130, 6362; h) C. J. Brown, R. G. Bergman,
K. N. Raymond, J. Am. Chem. Soc. 2009, 131, 17530; i) J. S.
Mugridge, R. G. Bergman, K. N. Raymond, J. Am. Chem. Soc.
2010, 132, 1182.
Acknowledgments
Support by the Deutsche Forschungsgemeinschaft (DFG) (inter-
national training school Seleca) and the Fonds der Chemischen In-
dustrie are gratefully acknowledged.
[4] a) A. J. Amoroso, J. C. Jefferey, P. L. Jones, J. A. McCleverty,
P. Thornton, M. D. Ward, Angew. Chem. 1995, 107, 1577; b)
R. L. Paul, A. J. Amoroso, P. L. Jones, S. M. Couchman, Z. R.
Reeves, L. H. Rees, J. C. Jefferey, J. A. McCleverty, M. D.
Ward, J. Chem. Soc., Dalton Trans. 1999, 1563; c) C. Brückner,
R. E. Powers, K. N. Raymond, Angew. Chem. 1998, 110, 1937;
d) D. Caulder, C. Brückner, R. E. Powers, S. König, T. N. Pa-
rac, J. A. Leary, K. N. Raymond, J. Am. Chem. Soc. 2001, 123,
8923; e) R. W. Saalfrank, H. Glaser, B. Demleitner, F. Hampel,
M. M. Chowdhry, V. Schünemann, A. X. Trautwein, G. B. M.
Vaughan, R. Yeh, A. V. Davis, K. N. Raymond, Chem. Eur. J.
2001, 8, 493.
[1] For selected examples, see: a) D. J. Cram, J. M. Cram, Con-
tainer molecules and their guests, RSC, Cambridge, 1994; b) A.
Scarso, J. Rebek Jr, Top. Curr. Chem. 2006, 265, 1; c) A. Jasat,
J. C. Sherman, Chem. Rev. 1999, 99, 931; d) R. W. Saalfrank,
I. Bernt, Curr. Opin. Colloid Interface Sci. 1998, 3, 407; e) R. W.
Saalfrank, H. Maid, A. Scheurer, Angew. Chem. 2008, 120,
8924; f) A. Lützen, Angew. Chem. 2005, 117, 1022; g) Special
issue on nanocontainers: M. Albrecht, F. E. Hahn (Eds.),
Chemistry of Nanocontainers, Top. Curr. Chem., vol. 319, 2012
(in press).
[5] a) M. Albrecht, I. Janser, R. Fröhlich, Chem. Commun. 2005,
157; b) M. Albrecht, I. Janser, J. Runsink, G. Raabe, P. Weis,
R. Fröhlich, Angew. Chem. 2004, 116, 6832; c) M. Albrecht, S.
Burk, P. Weis, C. A. Schalley, M. Kogej, Synthesis 2007, 3736.
[2] a) M. Fujita, Chem. Soc. Rev. 1998, 27, 417; b) M. Fujita, K.
Umemoto, M. Yoshizawa, N. Fujita, T. Kusukawa, K. Biradha,
Chem. Commun. 2001, 509; c) M. Yoshizawa, T. Kusukawa, M.
Fujita, K. Yamaguchi, J. Am. Chem. Soc. 2000, 122, 6311; d) [6] For an example, see: M. Albrecht, S. Burk, P. Weis, Synthesis
H. Ito, T. Kusukawa, M. Fujita, Chem. Lett. 2000, 598; e) M.
Yoshizawa, Y. Takeyama, T. Okano, M. Fujita, J. Am. Chem.
Soc. 2003, 125, 3243; f) M. Yoshizawa, J. K. Klosterman, M.
Fujita, Angew. Chem. 2009, 121, 3470.
2008, 2963.
[7] For acylhydrazones in metallosupramolecular chemistry see,
for example: M. Albrecht, Y. Liu, S. S. Zhu, C. A. Schalley, R.
Fröhlich, Chem. Commun. 2009, 1195.
[3] a) J. L. Brumaghim, M. Michels, D. Pagliero, K. N. Raymond,
Eur. J. Org. Chem. 2004, 5115; b) D. Caulder, C. Brückner,
R. E. Powers, S. König, T. N. Parac, J. A. Leary, K. N. Ray-
[8] a) R. Bernard, D. Cornu, J.-P. Scharff, R. Chiriac, P. Miele,
Inorg. Chem. 2006, 45, 8743; b) T.-C. Lin, W.-L. Lin, C.-M.
Wang, C.-W. Fu, Eur. J. Org. Chem. 2011, 912.
mond, J. Am. Chem. Soc. 2001, 123, 8923; c) M. Ziegler, J. L. [9] M. C. Davis, Synth. Commun. 2007, 37, 1457.
Brumaghim, K. N. Raymond, Angew. Chem. 2000, 112, 4285;
d) J. L. Brumaghim, M. Michels, K. N. Raymond, Eur. J. Org.
Chem. 2004, 4552; e) D. H. Leung, D. Fiedler, R. G. Bergman,
K. N. Raymond, Angew. Chem. 2004, 116, 981; f) D. Fiedler,
R. G. Bergman, K. N. Raymond, Angew. Chem. 2004, 116,
[10] For reviews, see: a) C. A. Schalley, Int. J. Mass Spectrom. 2000,
194, 11–39; b) C. A. Schalley, Mass Spectrom. Rev. 2001, 20,
253–309.
Received: November 30, 2011
Published Online: March 7, 2012
Eur. J. Org. Chem. 2012, 2422–2427
© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
www.eurjoc.org
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