the type I and type II structures is present. The assignment of
the coupling pattern was done by a COSY NMR experiment
Synthesis of the ligand
in dmso-d . The protons of the heterocyclic part of the quin-
oline lead to three sets of signals at d \ 8.87, 8.52, 7.70
1-(2,3-Dimethoxyphenyl)-2-(8-methoxyquinolin-7-yl)-
6
acetylene (3). 1-(2,3-Dimethoxyphenyl)acetylene5 (1, 200 mg,
1.25 mmol) in 5 ml of piperidine is added to a solution of
7-bromo-8-methoxyquinoline6 (2, 600 mg, 2.52 mmol), CuI
(2.4 mg, 0.01 mmol), and (Ph P) PdCl (265 mg, 0.38 mmol) in
(H2ÈH4 of the Ðrst ligand 7, K in Fig. 3) and 8.68, 8.29, 7.44
(H2ÈH4 of the second ligand 7, )) and 8.41, 7.65, 7.37 (H2ÈH4
of the third ligand 7, L) in a ratio 1 : 1 : 1. Consequently,
three sets of signals are detected for the phenolic protons of 7
at d \ 7.61, 7.09 (H5 and H6, Ðrst ligand 7, =) and 7.49, 7.09
(H5 and H6, second ligand 7, +) and 7.44, 6.89 (H5 and H6,
third ligand 7, …). However, for the catechol moieties only
three signals are observed at d \ 6.25È6.22, 6.11È6.08, 6.05È
6.00 (m, triple intensity each). The appearance of three sets of
signals in the 1H NMR spectrum shows that only the
unsymmetric type II complex is formed in the metal directed
self-assembly process, leading to three inequivalent ligands in
a ratio of 1 : 1 : 1. No signals are observed which correspond
to a type I structure.
3
2
2
50 ml of piperidine. The mixture is heated to 70 ¡C and after 2,
4, and 20 h additional alkyne 1 (200 mg per 1.25 mmol in 5 ml
piperidine each) is added. After 24 h the solvent is removed in
vacuum and the residue is puriÐed by column chromatog-
raphy (silica gel, hexane/ethyl acetate 2 : 1). Yield: 785 mg
(98%) of 3 as a yellow oil. 1H NMR (500 MHz, CDCl ):
3
d \ 8.94 (dd, J \ 1.1, 4.1 Hz, 1 H), 8.07 (dd, J \ 1.1, 8.3 Hz, 1
H), 7.57 (d, J \ 8.5 Hz, 1 H), 7.46 (d, J \ 8.5 Hz, 1 H), 7.37
(dd, J \ 4.1, 8.3 Hz, 1 H), 7.14 (d, J \ 8.0 Hz, 1 H), 7.02 (t,
J \ 8.0 Hz, 1 H), 6.89 (d, J \ 8.0 Hz, 1 H), 4.36 (s, 3 H), 4.04
(s, 3 H), 3.85 (s, 3 H). 13C NMR (126 MHz, CDCl ): d \ 157.8
3
Due to the C -symmetry of K [Ga (7) ] all protons of the
(C), 152.7 (C), 150.3 (C), 150.2 (CH), 142.5 (C), 135.9 (CH),
1
3
2
3
three spacers are not equivalent and lead to twelve resonances
which can be divided into three independent sets of four
signals each. Again the COSY NMR experiment shows the
presence of three sets of signals at d \ 3.22/2.98/2.48 (hidden
under solvent peak)/2.36, 3.13/2.69/2.32/2.20 and 2.94/2.63/
2.26/2.13. Similar 1H NMR spectroscopic results are obtained
for the corresponding sodium salt Na [Ga (7) ].
130.1 (CH), 129.6 (C), 124.8 (CH), 123.9 (CH), 122.5 (CH),
121.7 (CH), 117.8 (C), 115.2 (C), 113.0 (CH), 91.8 (C), 90.0 (C),
62.2 (CH ), 61.1 (CH ), 55.9 (CH ). MS (EI, 70 eV): m/z
3
3
3
(%) \ 319 (100, [M]`). HRMS calcd. for C
H
NO :
20 21
3
319.1208, found: 319.1226. IR (KBr, drift): v \ 3432, 2934,
2210, 1573, 1473, 1425, 1361, 1266, 1097, 1078 cm~1.
3
2
3
In the 13C NMR spectrum the C -symmetry of
1-(2,3-Dimethoxyphenyl)-2-(8-methoxyquinolin-7-yl)ethane
(4). A mixture of the alkyne 3 (650 mg, 2.04 mmol) and 200
mg of Pd/C in 40 ml of methanol is stirred under an atmo-
sphere of hydrogen for 65 min. The solvent is removed in
vacuum and the resulting mixture is separated by column
chromatography (silica gel, hexane/ethyl acetate 5 : 1). Yield:
60 mg (9%) of 4 as a white solid. Mp: 65 ¡C. 1H NMR (500
1
K [Ga (7) ] leads to the expected 51 nonequivalent carbon
atoms. Forty three signals of aromatic carbon atoms (two
3
2
3
with double intensity) and Ðve resonances of CH groups (one
2
with double intensity) are detected (see Experimental section).
Our attempts to prepare a heterodinuclear Ti(IV)/Ga(III)
complex failed,4 due to the insolubility of the obtained
material.
MHz, CDCl ): d \ 8.92 (dd, J \ 1.7, 4.2 Hz, 1 H), 8.11 (dd,
3
J \ 1.7, 8.3 Hz, 1 H), 7.50 (d, J \ 8.4 Hz, 1 H), 7.40 (d, J \ 8.4
Hz, 1 H), 7.35 (dd, J \ 4.2, 8.3 Hz, 1 H), 6.98 (t, J \ 7.9 Hz, 1
H), 6.83È6.78 (m, 2 H), 4.13 (s, 3 H), 3.87 (s, 3 H), 3.86 (s, 3 H),
3.17È3.13 (m, 2 H), 3.02È2.99 (m, 2 H). 13C NMR (126 MHz,
Conclusions
In this manuscript we have presented the synthesis of the
CDCl ): d \ 153.6 (C), 152.8 (C), 149.4 (CH), 147.3 (C), 143.0
ethylene-bridged catechol/8-hydroxyquinoline derivative 7-H
3
(C), 136.1 (CH), 135.8 (C), 134.6 (C), 129.1 (CH), 128.5 (C),
3
which is an interesting sequential ligand for the self-assembly
123.8 (CH), 122.9 (CH), 122.1 (CH), 120.5 (CH), 110.4 (CH),
62.4 (CH ), 60.7 (CH ), 55.7 (CH ), 31.7 (CH ), 31.4 (CH ). MS
of triple-stranded dinuclear helicates. Although one of the
three reaction steps of the preparation of 7-H proceeds in
3
3
3
2
2
(EI, 70 eV): m/z (%) \ 323 (51, [M]`), 172 (100, [M
3
only 9% yield we were able to obtain enough material to
[ C H O ]`). HRMS calcd. for C
H
NO : 323.1521,
investigate the formation of the dinuclear gallium(III) complex
K [Ga (7) ]. NMR spectroscopic results show that the
9
11
2
20 21
3
found: 323.1511. Elemental analysis calcd. for C
H
NO :
20 21
3
C: 74.28, H: 6.55, N: 4.33; found: C: 73.96, H: 6.68, N:
4.08%. IR (KBr, drift): v \ 3405, 2960, 2933, 1473, 1363, 1221,
1093, 1077, 1009, 836 cm~1.
3
2
3
unsymmetric type II complex is formed selectively. The type I
structure is not observed. The results which are discussed in
this article show that the formation of supramolecular and
metallo-supramolecular aggregates is inÑuenced by an inter-
action of steric and electronic factors. In the presented case
the high selectivity of the self-assembly process is most prob-
ably due to the tendency of similar metal ions to have a coor-
dination sphere as similar as possible. The understanding of
the inÑuences which control the self-assembly of super-
molecules should help in the design of new molecular
building-blocks for the formation of more sophisticated supra-
molecular structures.
Longer reaction times do not lead to an improved yield of
4. After 15 h of reaction time 1-(2,3-dimethoxyphenyl)-2-(8-
methoxy-1,2,3,4-tetrahydroquinolin-7-yl)ethane (6) is isolated
in quantitative yield as a colorless oil. 1H NMR (500 MHz,
CDCl ): d \ 7.01 (t, J \ 7.9 Hz, 1 H), 6.88 (dd, J \ 1.1, 7.9
3
Hz, 1 H), 6.81 (dd, J \ 1.1, 7.9 Hz, 1 H), 6.73 (d, J \ 7.7 Hz, 1
H), 6.53 (d, J \ 7.7 Hz, 1 H), 4.29 (br s, 1 H), 3.89 (s, 3 H), 3.87
(s, 3 H), 3.77 (s, 3 H), 3.34 (t, J \ 5.4 Hz, 2 H), 2.93 (m, 2 H),
2.87 (m, 2 H), 2.78 (t, J \ 6.4 Hz, 2 H), 1.96 (q, J \ 5.4, 6.4 Hz,
2 H). 13C NMR (126 MHz, CDCl ): d \ 152.8 (C), 147.2 (C),
3
144.2 (C), 138.2 (C), 136.4 (C), 132.2 (C), 124.8 (CH), 123.9
(CH), 121.9 (CH), 120.4 (C), 116.9 (CH), 110.2 (CH), 60.7
(CH ), 59.6 (CH ), 55.7 (CH ), 41.6 (CH ), 31.5 (CH ), 31.0
Experimental
3
3
3
2
2
1H NMR and 13C NMR spectra were recorded on a Bruker
AVANCE DRX 500 NMR spectrometer using DEPT tech-
niques for the assignment of the multiplicity of carbon atoms.
FT-IR spectra were recorded by di†use reÑection (KBr) on a
Bruker IFS spectrometer. Mass spectra (EI, 70 eV, positive
FAB in 3-NBA) were measured on a Finnigan MAT 90 mass
spectrometer. Elemental analyses were obtained with
Heraeus CHN-O-Rapid analyzer. Solvents were puriÐed by
standard methods. Melting points: Buchi 535 (uncorrected).
(CH ), 26.6 (CH ), 22.1 (CH ). MS (EI, 70 eV): m/z (%) \ 327
2
2
2
(100, [M]`). HRMS calcd. for C
H
NO : 327.1834, found:
20 25
3
327.1846. IR (KBr, Ðlm): v \ 3403, 2932, 2834, 1584, 1481,
1446, 1430, 1328, 1309, 1274, 1223, 1082, 1012 cm~1.
1-(2,3-Dihydroxyphenyl)-2-(8-hydroxyquinolin-7-yl)ethane
a
(7-H ). 1-(2,3-Dimethoxyphenyl)-2-(8-methoxyquinolin-7-yl)
3
ethane (4, 60 mg, 0.19 mmol) in 5 ml of 48% HBr is heated to
reÑux (2 h). Solvent is removed in vacuum and the residue is
New J. Chem., 2000, 24, 619È622
621