1H NMR [500 MHz, CDCl3]: d (ppm) 9.61 (broad s, 1 H), 8.78 (d,
J = 7.8, 1 H), 8.73 (d, J = 4.7, 1 H), 8.64 (d, J = 7.9, 1 H), 8.38
(d, J = 7.95, 1 H), 8.01 (t, J = 7.8, 1 H), 7.88 (dt, J = 7.8, 1.5, 1
H), 7.73 (br s, 1 H), 7.39 (dd, J = 7.4, 4.8 Hz, 1 H). ESI-MS m/z
215 (M+).
L1 as an off-white solid (0.04 g, 45% yield). 1H NMR [500 MHz,
CDCl3]: d (ppm) 8.67 (dd, J = 4.0, 0.5 Hz, 2 H), 8.54 (d, J =
7.5 Hz, 2 H), 8.43 (d, J = 7.5 Hz, 2 H), 8.18 (d, J = 8.0 Hz, 2 H),
7.89 (t, J = 8.0 Hz, 2 H), 7.84 (dt, J = 7.5, 3.0 Hz, 2 H), 7.54 (d,
J = 8.5 Hz, 2 H), 7.41 (s, 2 H), 7.34 (m, 2 H), 7.33 (m, 2 H), 4.84
(s, 4 H), 4.82 (s, 4 H), 4.18-3.50 (m, 20 H). ESI-MS m/z 953 (M+).
Found C: 62.8, H: 4.9, N: 11.5% C50H48N8O8S2. Requires: C: 63.0,
H: 5.1, N: 11.8%.
Synthesis of tridentate ester 12
A solution of 2,2ꢀ-bipyridine-6-thioamide (11) (0.6 g, 2.79 mmol)
and ethyl 3-bromopyruvate (0.60 g, 3.07 mmol) in ethanol (50 ml)
was refluxed for 6 h. On cooling large brown crystals of 12 slowly
formed which were filtered and washed with ethanol (2 × 2 ml)
and diethyl ether (2 × 2 ml) (0.5 g, 58% yield). 1H NMR [500 MHz,
CDCl3]: d (ppm) 9.19 (d, J = 5.5 Hz, 1 H), 9.12 (d, J = 8.0 Hz,
1 H), 8.85 (d, J = 8.0 Hz, 1 H), 8.56 (d, J = 8.0 Hz, 1 H), 8.54 (m,
1 H), 8.33 (s, 1 H), 8.18 (t, J = 8.0 Hz, 1 H), 7.98 (t, J = 6.5 Hz,
1 H), 4.45 (q, J = 7.0 Hz, 2 H), 1.44 (t, J = 7.0 Hz, 3 H). ESI-MS
m/z 312 (M + H+).
Synthesis of 2,2ꢀ-bipyridine-crown ether 15
Under an atmosphere of nitrogen a two necked round bottom
flask was charged with 3,3-dihydroxy-2,2-bipyridine13 (14) (1.0 g,
5.3 mmol) and sodium hydride (60% dispersion in oil, 0.85 g,
22.2 mmol). To this anhydrous DMF (50 ml) was added and
the reaction heated to 60 ◦C with stirring for 1 h. After this
time penta-(ethylene glycol)-di-p-tosylate (2.9 g, 5.3 mmol) was
added to the reaction mixture and heating continued for a further
24 h. Methanol (5 ml) was then added and the solvents removed
by rotary evaporation. To the resulting brown oil, NaHCO3(aq)
(40 ml) was then added and extracted with DCM (4 × 50 ml).
Evaporation of the combined organic layers gave a brown oil that
was purified via column chromatography (10% MeOH in DCM,
SiO2) giving 15 as a viscous amber oil.8 This solidified on standing
Synthesis of tridentate alcohol 13
The tridentate ester (12) (0.2 g, 0.64 mmol) was added to a dry
100 ml two necked round bottom flask, under an atmosphere of
nitrogen. Anhydrous THF (30 ml) was added to the flask and
the resulting solution stirred in an ice bath at 0 ◦C for 15 min.
To this lithium aluminium hydride, (1.0 M solution in diethyl
ether, 1.28 ml, 1.28 mmol) was slowly added over the course of
20 min. Stirring was continued for 2 h at 0 ◦C before removing
the ice bath and allowing the reaction to gradually warm up
to room temperature. Any remaining lithium aluminium hydride
was quenched by slow addition of THF (2 ml), methanol (2 ml)
and finally water (2 ml). The solvents were removed by rotary
evaporation to leave a viscous yellow emulsion to which distilled
water (20 ml) was added and extracted into DCM (4 × 50 ml).
Evaporation of the organic solvent gave a yellow solid that was
purified via column chromatography (1% MeOH in DCM, Al2O3)
giving the tridentate alcohol (13) as a pale yellow solid (0.1 g, 58%
yield). 1H NMR [500 MHz, CDCl3]: d (ppm) 8.71 (d, J = 5.0 Hz,
1 H), 8.57 (d, J = 8.0 Hz, 1 H), 8.48 (d, J = 8.0 Hz, 1 H), 8.19 (d,
J = 7.0 Hz, 1 H), 7.95 (t, J = 8.0 Hz, 1 H), 7.9 (dt, J = 7.5, 1.5 Hz,
1 H), 7.37 (ddd, J = 7.5, 5.0, 1.0 Hz, 1 H), 7.34 (s, 1 H), 4.89 (s,
2 H), 2.45 (br s, 1 H, –OH). ESI-MS m/z 292 (M + Na+).
1
to give a pale brown waxy solid (1.3 g, 63% yield). H NMR
[400 MHz, CDCl3]: d (ppm) 8.35 (d, J = 4.2 Hz, 2 H), 7.35 (m,
2 H), 7.30 (m, 2 H), 4.20-3.40 (m, 20 H). ESI-MS m/z 391 (M +
H+).
Synthesis of bis-N,Nꢀ-oxide 16
A solution of 2,2ꢀ-bipyridine-crown ether (15) (1.0 g, 2.56 mmol)
and mCPBA (77%, 1.26 g, 5.63 mmol) in DCM (40 ml) was stirred
at room temperature for 6 h. The reaction was followed by TLC
and upon completion the solvent was reduced to half its volume by
rotary evaporation. Purification of the crude product via column
chromatography (1% MeOH in DCM, Al2O3) gave the bis-N,Nꢀ-
oxide (16) as a white solid (0.9 g, 83% yield). 1H NMR [400 MHz,
CDCl3]: d (ppm) 8.05 (d, J = 6.5, 2 H), 7.25 (m, 2 H), 7.0 (d, J =
8.6 Hz, 2 H), 4.30-3.45 (m, 20 H). ESI-MS m/z 422 (M +).
Synthesis of 2,2ꢀ-bipyridine-crown ether 6,6ꢀ-dicarbonitrile 17
A solution of bis-N,Nꢀ-oxide (16) (0.8 g, 1.9 mmol) and benzoyl
chloride (0.59 g, 4.16 mmol) in DCM (50 ml) was refluxed, and
trimethylsilyl cyanide (0.41 g, 4.17 mmol) added slowly over a
period of 30 min. Upon completion the solution was cooled
and washed with NaHCO3(aq) (50 ml). Removal of the solvent
by rotary evaporation give the crude product as a brown oil,
purification via column chromatography (1% MeOH in DCM,
Al2O3) afforded the 6,6ꢀ-dicarbonitrile derivative (17) as a white
solid (0.6 g, 72% yield). 1H NMR [400 MHz, CDCl3]: d (ppm) 7.75
(d, J = 8.7, 2 H), 7.45 (d, J = 8.6 Hz, 2 H), 4.35–3.55 (m, 20 H).
ESI-MS m/z 441 (M + H+).
Synthesis of L1
To a dry 100 ml two necked round bottom flask the tridentate unit
(13) (0.050 g, 0.19 mmol), sodium hydride (60% dispersion in oil,
0.029 g, 0.74 mmol) and tetra-n-butylammonium bromide (5 mg,
0.015 mmol) was added. The flask was immediately fitted with a
dry reflux condenser and placed under an atmosphere of nitrogen.
To this anhydrous THF (40 ml) was added and the mixture
heated under reflux for 1 h. After this time the 2,2ꢀ-bipyridine-
6,6ꢀ-dimethyl chloride derivative (8) (0.045 g, 0.093 mmol) was
added and the reaction was heated under reflux for a further
36 h, monitoring the progress by TLC. Upon completion methanol
(5 ml) was added and the solvent removed by rotary evaporation.
To the residual yellow oil distilled water (10 ml) was added and
extracted with DCM (3 × 50 ml). Evaporation of the combined
organic layers gave a crude product that was purified via column
chromatography (1% MeOH in DCM, Al2O3) giving the ligand
Synthesis of 2,2ꢀ-bipyridine-crown ether 6,6ꢀ-dithioamide 18
To a solution of 6,6ꢀ-dicarbonitrile derivative (17) (0.7 g,
1.59 mmol) in ethanol (20 ml), triethylamine (1.0 g, 9.9 mmol)
was added and H2S was slowly bubbled through the solution for
1584 | Dalton Trans., 2007, 1577–1587
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The Royal Society of Chemistry 2007
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