Metallohost−Guest Complexes via Transmetalation
A R T I C L E S
6H), 4.49-4.52 (m, 8H), 6.77 (s, 2H), 6.83-6.91 (m, 6H), 8.23 (s,
2H), 8.26 (s, 2H), 9.64 (s, 2H), 9.73 (s, 2H). 13C NMR (75 MHz,
CDCl3): δ 56.19 (CH3), 73.02 (CH2), 73.18 (CH2), 113.72 (CH), 116.51
(C), 117.62 (C), 119.42 (CH), 120.63 (CH), 122.36 (CH), 145.69 (C),
147.14 (C), 148.15 (C), 151.13 (CH), 151.82 (CH). Anal. Calcd for
C28H30N4O10: C, 57.73; H, 5.19; N, 9.62. Found: C, 57.41; H, 5.45;
N, 9.49.
The characteristic helical frameworks of the heteronuclear
metal complexes obtained here would be applied to chiral recog-
nition, when a chiral auxiliary is introduced into the ligands. In
addition, the multi-metal cores may provide an effective multi-
binding site for anions and a catalytic site for various organic
reactions as well. If the metals in the complexes are paramag-
netic, novel magnetic properties are expected due to 3d-3d and
3d-4f magnetic exchange. These kinds of synergetic functions
at the molecular level are our next challenging target to achieve
more sophisticated intelligent molecules by using the multi-
salamo metal complexes.
Synthesis of Ligand H4L′. To a solution of monooxime 3b
(R ) H)11c (275.0 mg, 1.40 mmol) in ethanol (20 mL) was gradually
added a solution of 2,3-dihydroxybenzene-1,4-dicarbaldehyde (2) (116.3
mg, 0.70 mmol) in ethanol (20 mL). The mixture was heated for 1 h
at 50-55 °C and cooled to room temperature. The white precipitates
were collected to give H4L′ (243 mg, 66%) as colorless crystals, mp
Experimental Section
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142-143 °C. H NMR (400 MHz, CDCl3): δ 4.48-4.52 (m, 8H),
6.77 (s, 2H), 6.90 (t, J ) 7.6 Hz, 2H), 6.97 (d, J ) 7.6 Hz, 2H), 7.16
(d, J ) 7.6 Hz, 2H), 7.28 (t, J ) 7.6 Hz, 2H), 8.23 (s, 2H), 8.25 (s,
2H), 9.65 (s, 2H), 9.73 (s, 2H). 13C NMR (75 MHz, CDCl3): δ 72.96
(CH2), 73.32 (CH2), 116.16 (C), 116.76 (CH), 117.61 (C), 119.65 (CH),
120.80 (CH), 130.93 (CH), 131.39 (CH), 145.79 (C), 151.37 (CH),
152.35 (CH), 157.42 (C). Anal. Calcd for C26H26N4O8: C, 59.77; H,
5.02; N, 10.72. Found: C, 59.45; H, 5.02; N, 10.80.
General. All experiments were carried out in air unless otherwise
noted. Diethyl ether was distilled from sodium benzophenone ketyl
prior to use. N,N,N′,N′-Tetramethylethylenediamine, N,N-dimethylfor-
mamide, and dichloromethane were distilled from calcium hydride prior
to use. Commercial chloroform and ethanol were used without further
purification. All chemicals were of reagent grade and used as received.
1H and 13C NMR spectra were recorded on a Bruker AC300 (300 and
75 MHz) or ARX400 (400 and 100 MHz) spectrometer. Mass spectra
(ESI-TOF, positive mode) were recorded on an Applied Biosystems
QStar Pulsar i spectrometer.
Synthesis of Zinc(II) Complex [LZn3(OAc)2]. A solution of zinc-
(II) acetate dihydrate (26.3 mg, 0.12 mmol) in ethanol (10 mL) was
added to a solution of ligand H4L (23.3 mg, 0.040 mmol) in chloroform/
ethanol (1:4, 10 mL). After the resulting solution was allowed to stand
at room temperature, the precipitates were collected to afford the
complex (30.9 mg, 82%) as yellow crystals. 1H NMR (400 MHz,
CDCl3): δ 2.09 (s, 6H), 3.61 (s, 6H), 3.93 (dd, J ) 13.9, 1.8 Hz, 2H),
4.11 (dd, J ) 15.2, 4.2 Hz), 4.32 (t, J ) 12.1 Hz, 2H), 5.43 (t, J )
13.0 Hz, 2H), 6.44 (s, 2H), 6.48 (t, J ) 7.8 Hz, 2H), 6.67 (dd, J ) 7.8,
1.5 Hz, 2H), 6.75 (dd, J ) 7.8, 1.5 Hz, 2H), 8.20 (s, 2H), 8.35 (s, 2H).
Anal. Calcd for C32H32N4O14Zn3‚3H2O: C, 40.59; H, 4.05; N, 5.92.
Found: C, 40.66; H, 3.95; N, 5.86.
Caution: Metal perchlorates are potentially explosiVe. Only a small
amount of material should be prepared, and it should be handled with
great care.
Synthesis of 2,3-Dimethoxybenzene-1,4-dicarbaldehyde (1). To
a solution of o-dimethoxybenzene (2.76 g, 20 mmol) and N,N,N′,N′-
tetramethylethylenediamine (15 mL, 100 mmol) in diethyl ether (70
mL) was added n-butyllithium (2.6 M solution in hexane, 39 mL, 100
mmol) at 0 °C under argon atmosphere. The mixture was heated to
reflux for 20 h. After the mixture was cooled to room temperature,
N,N-dimethylformamide (8.6 mL, 110 mmol) was added to the mixture,
which was stirred overnight at room temperature. After addition of water
(50 mL), the mixture was extracted with chloroform. The organic layer
was dried over anhydrous magnesium sulfate, filtered, and concentrated
to give a reddish brown oil. The residue was then chromatographed on
silica gel (chloroform) to give a pale yellow solid, which was further
purified by recrystallization from dichloromethane/hexane to afford 2,3-
dimethoxybenzene-1,4-dicarbaldehyde (1) (1.55 g, 40%) as pale yellow
Synthesis of Zinc(II) Complex [L′Zn3(OAc)2]. A solution of zinc-
(II) acetate dihydrate (9.9 mg, 0.045 mmol) in ethanol (5 mL) was
added to a solution of ligand H4L′ (7.8 mg, 0.015 mmol) in chloroform/
ethanol (1:4, 5 mL). The resulting solution was concentrated to dryness,
and the residue was recrystallized from acetone/hexane to afford the
complex (7.3 mg, 52%) as yellow crystals. 1H NMR (400 MHz,
CDCl3): δ 2.15 (s, 6H), 4.21 (dd, J ) 12.5, 2.4 Hz, 2H), 4.22 (dd, J
) 15.2, 4.5 Hz, 2H), 4.46 (td, J ) 12.5, 4.5 Hz, 2H), 5.57 (ddd, J )
15.2, 12.5, 2.4 Hz, 2H), 6.51 (s, 2H), 6.62 (t, J ) 7.4 Hz, 2H), 6.83 (d,
J ) 8.4 Hz, 2H), 7.04 (dd, J ) 7.4, 1.7 Hz, 2H), 7.20 (ddd, J ) 8.4,
7.4, 1.7 Hz, 2H), 8.19 (s, 2H), 8.52 (s, 2H). Anal. Calcd for
C30H28N4O12Zn3‚3H2O‚Me2CO: C, 41.95; H, 4.27; N, 5.93. Found: C,
42.18; H, 3.81; N, 5.82.
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crystals, mp 100-101 °C. H NMR (400 MHz, CDCl3): δ 4.06 (s,
6H), 7.64 (s, 2H), 10.45 (s, 2H). 13C NMR (100 MHz, CDCl3): δ 62.41
(CH3), 122.76 (CH), 134.17 (C), 156.61 (C), 189.16 (CHO). Anal. Calcd
for C10H10O4: C, 61.85; H, 5.19. Found: C, 61.89; H, 5.53.
Synthesis of 2,3-Dihydroxybenzene-1,4-dicarbaldehyde (2). To
a solution of 2,3-dimethoxybenzene-1,4-dicarbaldehyde (1) (1.59 g, 8.19
mmol) in dichloromethane (70 mL) was added boron tribromide (3.1
mL, 32.8 mmol) under nitrogen atmosphere. After the mixture was
stirred for 4 h at room temperature, water (70 mL) was added to the
mixture, which was further stirred overnight. The mixture was extracted
with chloroform, and the organic layer was dried over anhydrous
magnesium sulfate, filtered, and concentrated to dryness. The residue
was recrystallized from chloroform/hexane to give dialdehyde 2 (1.29
Preparation of [LZn2Ln(OAc)3]. A solution of zinc(II) acetate
dihydrate (4.4 mg, 0.020 mmol) in methanol (1 mL) and a solution of
Ln(OAc)3‚nH2O (Ln ) lanthanide; 0.010 mmol) in water/methanol (1:
4, 1 mL) were added to a solution of H4L (5.8 mg, 0.010 mmol) in
chloroform (1 mL), and the resulting solution was concentrated to
dryness. Vapor-phase diffusion of diethyl ether into a chloroform/
methanol solution of the residue gave yellow crystals of [LZn2Ln-
(OAc)3].
1
g, 95%) as yellow crystals, mp 140-143 °C. H NMR (300 MHz,
[LZn2La(OAc)3]. Yield 77%. Anal. Calcd for C34H35LaN4O16Zn2‚
CHCl3: C, 36.72; H, 3.17; N, 4.89. Found: C, 37.13; H, 3.41; N, 4.87.
CDCl3): δ 7.28 (s, 2H), 10.03 (s, 2H), 10.91 (s, 2H). 13C NMR (100
MHz, CDCl3): δ 122.15 (CH), 123.24 (C), 150.77 (C), 196.18 (CHO).
Anal. Calcd for C8H6O4: C, 57.84; H, 3.64. Found: C, 57.35; H,
3.74.
[LZn2Ce(OAc)3]. Yield 78%. Anal. Calcd for C34H35CeN4O16Zn2‚
3MeOH‚0.75CHCl3: C, 37.40; H, 3.97; N, 4.62. Found: C, 37.43; H,
3.82; N, 4.53.
Synthesis of Ligand H4L. To a solution of monooxime 3a
(R ) OMe)11c (271.7 mg, 1.20 mmol) in ethanol (20 mL) was gradually
added a solution of 2,3-dihydroxybenzene-1,4-dicarbaldehyde (2) (99.7
mg, 0.60 mmol) in ethanol (20 mL). The mixture was heated for 40
min at 50-55 °C and cooled to room temperature. The white
precipitates were collected to give H4L (307.1 mg, 88%) as colorless
[LZn2Pr(OAc)3]. Yield 73%. Anal. Calcd for C34H35N4O16PrZn2‚
3MeOH‚CHCl3: C, 36.72; H, 3.89; N, 4.51. Found: C, 37.03; H, 3.72;
N, 4.53.
[LZn2Nd(OAc)3]. Yield 92%. Anal. Calcd for C34H35N4NdO16Zn2‚
3MeOH‚CHCl3: C, 36.62; H, 3.88; N, 4.50. Found: C, 36.64; H, 3.61;
N, 4.53.
1
crystals, mp 147-148 °C. H NMR (300 MHz, CDCl3): δ 3.91 (s,
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J. AM. CHEM. SOC. VOL. 128, NO. 49, 2006 15773