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Synlett 2008(2): 207-212  
DOI: 10.1055/s-2007-1000865
LETTER
© Georg Thieme Verlag Stuttgart · New York

Chiral Elaboration of Gold Nanoparticle Surfaces by Bis(binaphthyl) Groups

Mohammad Nuruzzamana, Thomas C. Prestona, Silvia Mittlerb, Nathan D. Jones*a
a Department of Chemistry, The University of Western Ontario, London, ON, N6A 5B7, Canada
e-Mail: njones26@uwo.ca; Fax: +1(519)6613022;
b Department of Physics and Astronomy, The University of Western Ontario, London, ON, N6A 5B7, Canada
Further Information

Publication History

Received 3 July 2007
Publication Date:
21 December 2007 (online)

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Abstract

The synthesis of a family of bis(binaphthyl)-based compounds for the chiral modification of gold nanoparticle surfaces is described. In these systems, two (S)-1,1′-bi-2-naphthol groups are linked to one another by a single diethanolamine-derived bridge, the nitrogen atom of which serves as an anchor for the attachment of an alkanethiol tether of 6, 10, or 12 methylene units in length. The terminal thiol group allows the production of surface-elaborated gold nanoparticles of 2.1 ± 0.6 nm diameter by a ‘direct synthesis’ method.

Key words

chirality - binaphthol - nanoparticle - gold - surface

    References and Notes

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    The preparation of 7c was as follows: To a suspension of 60% NaH (1.38 g, 95.79 mmol) in THF (80 mL) and DMF (15 mL) at r.t. was added a solution of 1,12-dodecanediol (12.92 g, 63.86 mmol) in THF (50 mL). The mixture was stirred at r.t. for 30 min, and a solution of p-methoxybenzyl chloride (5.0 g, 31.93 mmol) in THF (20 mL) and TBAB (0.2 g, 0.64 mmol) were added. The mixture was stirred at 60 °C for 4 d and then cooled to r.t., and quenched with sat. NH4Cl. The solvent was removed in vacuo, extracted with EtOAc, washed with H2O and brine, dried over Na2SO4, and concentrated under reduced pressure. The crude material was purified by column chromatography (30% EtOAc-hexanes) to give the pure product 7c (5.59 g) in 54% yield. 1H NMR (CDCl3): δ = 1.26-1.39 (m, 16 H), 1.54-1.70 (m, 4 H), 3.42 (t, J = 6.6 Hz, 2 H), 3.63 (q, J = 6.6 Hz, 2 H), 3.79 (s, 3 H), 4.43 (s, 2 H), 6.86 (d, J = 8.8 Hz, 2 H), 7.26 (d, J = 8.8 Hz, 2 H). 13C{1H} NMR (CDCl3): δ = 25.96, 26.42, 29.65, 29.69, 29.78, 29.99, 33.03, 55.49, 63.28, 70.46, 72.72, 113.96, 129.45, 131.03, 159.30. MS: m/z = 322 [M+], 137, 121. HRMS: m/z calcd for C20H34O3: 322.2508; found: 322.2497.
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25

To a stirred solution of 3 (16.0 g, 37.85 mmol) in acetone (200 mL), 4 (10.0 g, 15.14 mmol) and K2CO3 (31.7 g, 229 mmol) were added. The mixture was heated to reflux for 24 h. After cooling to r.t., H2O was added and the solution was extracted with EtOAc. The organic layer was dried over Na2SO4 and concentrated under reduced pressure. Purification by column chromatography (10-30% EtOAc-hexanes) gave the pure compound 5 (16.32 g) in 93% yield. 1H NMR (CDCl3): δ = 2.42-2.60 (m, 4 H), 3.20-3.45 (m, 4 H), 6.01 (s, 2 H), 6.65-7.34 (m, 40 H), 7.40-7.88 (m, 8 H). 13C{1H} NMR (CDCl3): δ = 14.52, 21.36, 47.23, 60.68, 67.84, 82.46, 114.59, 117.24, 119.96, 126.78, 134.29, 141.68, 149.59. MS: m/z = 1181 [M + Na]+, 1158 [M+], 364, 338, 242. HRMS: m/z calcd for C76H58N2O8SNa: 1181.3864; found: 1181.3897.

27

To a stirred solution of 5 (15.0 g, 12.94 mmol) in DMF (250 mL) were added K2CO3 (7.15 g, 51.76 mmol) and 4-methylbenzenethiol (3.21 g, 25.88 mmol). Water was added after overnight stirring at r.t. The aqueous layer was extracted several times with EtOAc, and the combined organic fractions were washed with 1 M NaOH and H2O, and dried over Na2SO4. After removal of the solvent, the crude product was purified by column chromatography (40% EtOAc-hexanes) to give 6 (11.47 g) in 91% yield. 1H NMR (CDCl3): δ = 1.98-2.18 (m, 4 H), 3.40-3.59 (m, 4 H), 6.10 (s, 2 H), 6.80-7.38 (m, 36 H), 7.70 (dd, 4 H), 7.90 (dd, 4 H). 13C{1H} NMR (CDCl3): δ = 47.91, 68.97, 82.61, 115.20, 117.35, 120.16, 121.78, 123.77, 124.02, 125.74, 127.42, 134.31, 134.40, 141.93, 142.09, 153.46, 154.44. MS: m/z = 973 [M+], 521, 286. HRMS: m/z calcd for C70H55NO4: 973.4131; found: 973.4105.

29

Compounds 8a-c were made using modifications to reported procedures. Compound 8a is a known compound. See ref. 28a-c. Compound 8b is likewise known. See ref. 28d,e. The preparation of 8c was as follows: To a solution of 7c (5.45 g, 16.90 mmol) in CH2Cl2 (100 mL) at 0 °C, imidazole (2.3 g, 33.80 mmol) and Ph3P (8.86 g, 33.80 mmol) were added under N2 and the mixture was stirred at the same temperature for 10-15 min. Then, I2 (8.58 g, 33.80 mmol) was added (by portion) and the mixture was stirred at 0 °C for an additional 30 min. The resultant mixture was diluted with CH2Cl2, washed with 1 M HCl, H2O and brine, dried over Na2SO4, and concentrated under reduced pressure to give the crude product. Purification by column chromatography (10% EtOAc-hexanes) afforded compound 8c (6.31 g) in 86% yield. 1H NMR (CDCl3): δ = 1.26-1.39 (m, 16 H), 1.57-1.60 (m, 2 H), 1.79-1.83 (m, 2 H), 3.18 (t, J = 7.2 Hz, 2 H), 3.43 (t, J = 6.8 Hz, 2 H), 3.80 (s, 3 H), 4.43 (s, 2 H), 6.86 (d, J = 8.8 Hz, 2 H), 7.26 (d, J = 8.8 Hz, 2 H). 13C{1H} NMR (CDCl3): δ = 7.57, 26.43, 28.76, 29.63, 29.70, 29.76, 29.79, 30.01, 30.74, 33.79, 55.51, 70.46, 72.73, 113.96, 129.43, 131.05, 159.31. MS: m/z = 432 [M+], 228, 121. HRMS: m/z calcd for C20H33IO3: 432.1525; found: 432.1520.

30

The preparation of 9a is given as a typical procedure: To a solution of 6 (1.0 g, 1.03 mmol) in acetone (40 mL), K2CO3 (1.14 g, 8.24 mmol) was added and the mixture was brought to reflux for 30 min. After cooling to r.t., a solution of iodide 8a (896 mg, 2.57 mmol) in acetone (10 mL) was added slowly and the mixture was again heated to reflux for 3 d. After cooling to r.t., H2O was added and the solution was extracted with EtOAc. The organic layer was dried over Na2SO4 and concentrated under reduced pressure. Purification by column chromatography (10-30% EtOAc-hexanes) gave the pure compound 9a (1.17 g) in 95% yield. 1H NMR (CDCl3): δ = 0.71-0.75 (m, 4 H), 1.03-1.07 (m, 2 H), 1.43-1.49 (m, 2 H), 1.61-1.67 (m, 2 H), 2.15 (br s, 4 H), 3.38 (t, J = 6.4 Hz, 2 H), 3.48-3.57 (m, 4 H), 3.81 (s, 3 H), 4.45 (s, 2 H), 6.08 (s, 2 H), 6.89-7.36 (m, 40 H), 7.73 (dd, J = 9.2, 8.4 Hz, 4 H), 7.94 (dd, J = 8.0, 9.2 Hz, 4 H). 13C{1H} NMR (CDCl3): δ = 26.06, 26.73, 27.42, 29.24, 29.74, 31.68, 52.37, 54.99, 55.23, 68.01, 70.20, 72.49, 82.18, 113.74, 116.97, 123.64, 125.58, 125.63, 128.03, 134.13, 153.16, 154.54, 159.08. MS: m/z = 1194 [M + H]+, 546, 409. HRMS: m/z calcd for C84H75NO6: 1194.5678; found: 1194.5680.
Compound 9b: 79% yield. 1H NMR (CDCl3): δ = 0.71-0.79 (m, 4 H), 0.97-1.42 (m, 10 H), 1.65-1.78 (m, 4 H), 2.19 (br s, 4 H), 3.45-3.65 (m, 6 H), 3.80 (s, 3 H), 4.48 (s, 2 H), 6.12 (s, 2 H), 6.90-7.38 (m, 40 H), 7.73 (dd, J = 8.8, 7.6 Hz, 4 H), 7.94 (t, J = 8.8 Hz, 4 H). 13C{1H} NMR (CDCl3): δ = 26.58, 27.26, 27.85, 29.89, 29.92, 30.14, 52.77, 55.55, 68.35, 70.56, 72.83, 82.54, 114.05, 115.14, 117.33, 119.94, 125.92, 128.07, 134.45, 142.05, 142.21, 153.50, 154.88, 159.39. MS: m/z = 1250 [M+]. HRMS: m/z calcd for C88H83NO6: 1250.6299; found: 1250.6293.
Compound 9c: 81% yield. 1H NMR (CDCl3): δ = 0.71-0.79 (m, 4 H), 1.19-1.45 (m, 14 H), 1.65-1.78 (m, 4 H), 2.19 (br s, 4 H), 3.45-3.65 (m, 6 H), 3.80 (s, 3 H), 4.48 (s, 2 H), 6.12 (s, 2 H), 6.90-7.38 (m, 40 H), 7.73 (dd, J = 8.8, 7.6 Hz, 4 H), 7.94 (t, J = 8.8 Hz, 4 H). 13C{1H} NMR (CDCl3): δ = 26.56, 27.28, 27.86, 29.99, 52.75, 55.44, 68.33, 70.54, 72.81, 82.53, 114.04, 115.11, 117.32, 119.92, 121.97, 123.64, 125.00-131.10 (m), 134.45, 142.20, 153.49, 154.87, 159.38. MS: m/z = 1278 [M+], 549, 509. HRMS: m/z calcd for C90H87NO6: 1278.6645; found: 1278.6631.

31

The preparation of 10a is given as a typical procedure: To a solution of 9a (1.0 g, 0.84 mmol) in EtOAc-MeOH (1:1, 40 mL), 10% Pd/C (300 mg) was carefully added. After stirring at r.t. for 4 d under H2 atmosphere, the catalyst was filtered off and the filtrate was reduced to dryness in vacuo. The crude material was purified by column chromatography (60% EtOAc-hexanes) to afford the product 10a (587 mg) in 81% yield. 1H NMR (CDCl3): δ = 0.78-1.15 (m, 6 H), 1.32-1.41 (m, 2 H), 1.88-2.15 (m, 2 H), 2.19-2.30 (m, 2 H), 2.31-2.42 (m, 2 H), 3.30 (t, J = 8.8 Hz, 2 H), 3.58-3.78 (m, 7 H), 4.45 (s, 2 H), 6.87-7.38 (m, 22 H), 7.80-7.95 (m, 8 H). 13C{1H} NMR (CDCl3): δ = 26.16, 26.75, 27.42, 29.74, 32.57, 51.56, 54.42, 62.96, 66.42, 114.99, 116.97, 123.64, 125.58, 125.63, 128.03, 134.13, 153.16, 154.54. MS: m/z = 862 [M+], 550, 242. HRMS: m/z calcd for C58H55NO6: 862.4081; found: 862.4073.
Compound 10b: 63% yield. 1H NMR (CDCl3): δ = 0.82-1.42 (m, 14 H), 1.59-1.72 (m, 2 H), 1.96-2.18 (m, 2 H), 2.25-2.35 (m, 2 H), 2.44-2.58 (m, 2 H), 3.45 (t, J = 8.8 Hz, 2 H), 3.60-3.78 (m, 7 H), 4.35 (s, 2 H), 6.87-7.38 (m, 22 H), 7.80-7.94 (m, 8 H). 13C{1H} NMR (CDCl3): δ = 26.19, 26.27, 29.41, 29.44, 29.51, 29.76, 51.55, 54.23, 55.23, 66.37, 54.23, 55.23, 66.37, 70.21, 72.48, 113.72, 114.64, 116.87, 116.92, 118.94, 123.20, 124.02, 125.05, 125.16, 127.94, 133.91, 151.61, 154.43, 159.06. MS: m/z = 918 [M+], 749, 509, 219. HRMS: m/z calcd for C62H63NO6: 918.4734; found: 918.4724.
Compound 10c: 50% yield. 1H NMR (CDCl3): δ = 0.81-1.38 (m, 18 H), 1.48-1.62 (m, 2 H), 1.93-2.42 (m, 2 H), 2.23-2.35 (m, 2 H), 2.46-2.57 (m, 2 H), 3.43 (t, J = 8.8 Hz, 2 H), 3.68-3.84 (m, 7 H), 4.45 (s, 2 H), 6.86-7.37 (m, 22 H), 7.80-7.94 (m, 8 H). 13C {1H} NMR: δ = 26.46, 27.40, 27.86, 29.82, 51.75, 55.49, 70.47, 72.73, 113.96, 114.88, 117.17, 119.22, 123.48, 129.65, 130.62, 134.22, 151.86, 154.81. MS: m/z = 946 [M+]. HRMS: m/z calcd for C64H67NO6: 946.5022; found: 946.5020.

32

The preparation of 11a is given as a typical procedure: To an ice-cold mixture of 10a (400 mg, 0.46 mmol) in CH2Cl2/H2O (10:1, 11 mL) was added 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ, 211 mg, 0.92 mmol) in one portion. The mixture was stirred at 0 °C for 1.5 h, and diluted with sat. NaHCO3. The organic layer was removed, and the aqueous layer was extracted with CH2Cl2. The combined organic fractions were dried over Na2SO4 and concentrated. Purification by column chromatography (70% EtOAc-hexanes) gave 11a (264 mg) in 77% yield. 1H NMR (CDCl3): δ = 0.78-1.15 (m, 6 H), 1.32-1.41 (m, 2 H), 1.88-2.15 (m, 2 H), 2.19-2.30 (m, 2 H), 2.31-2.42 (m, 2 H), 3.42 (t, J = 6.8 Hz, 2 H), 3.61-3.78 (m, 4 H), 4.45 (s, 2 H), 6.87-7.38 (m, 18 H), 7.78-7.95 (m, 8 H). 13C{1H} NMR (CDCl3): δ = 25.49, 26.17, 26.75, 29.93, 32.56, 51.55, 54.42, 62.96, 66.42, 114.98, 119.04, 123.46, 124.37, 125.22, 125.40, 126.53, 127.29, 128.27, 129.65, 130.62, 134.20, 151.87, 154.58. MS: m/z = 842 [M+], 639, 430, 242. HRMS: m/z calcd for C50H47NO5: 742.3532; found: 742.3535.
Compound 11b: 60% yield. 1H NMR (CDCl3): δ = 0.82-1.52 (m, 14 H), 1.72-1.74 (m, 2 H), 1.76-2.02 (m, 2 H), 2.22-2.45 (m, 4 H), 3.43 (t, J = 6.8 Hz, 2 H), 3.50-3.78 (m, 4 H), 6.87-7.42 (m, 18 H), 7.58-7.94 (m, 8 H). 13C{1H} NMR (CDCl3): δ = 25.86, 26.14, 27.11, 29.46, 32.89, 51.53, 54.73, 63.17, 66.21, 114.93, 116.89, 117.36, 119.15, 123.47, 124.37, 125.22, 125.41, 126.54, 127.26, 128.20, 129.66, 134.19, 151.93, 154.54. MS: m/z = 798 [M+], 549. HRMS: m/z calcd for C54H55NO5: 798.4181; found: 798.4185.
Compound 11c: 45% yield. 1H NMR (CDCl3): δ = 0.77-1.31 (m, 18 H), 1.45-1.49 (m, 2 H), 1.86-2.20 (m, 2 H), 2.23-2.35 (m, 2 H), 2.46-2.57 (m, 2 H), 3.54 (t, J = 6.8 Hz, 2 H), 3.64-3.73 (m, 4 H), 6.87-7.29 (m, 18 H), 7.73-7.86 (m, 8 H). 13C{1H} NMR (CDCl3): δ = 25.96, 26.50, 27.39, 29.67, 32.96, 51.77, 54.54, 63.22, 66.57, 114.93, 117.13, 117.37, 118.24, 119.26, 123.45, 124.29, 125.31, 125.46, 125.62, 127.45, 128.27, 128.54, 129.62, 129.76, 134.23, 151.96, 154.68. MS: m/z = 826 [M+], 549. HRMS: m/z calcd for C56H59NO5: 826.4431; found: 826.4441.

34

The preparation of 2a is given as a typical procedure: To a solution of 11a (200 mg, 0.27 mmol) in CH2Cl2 (10 mL), imidazole (55 mg, 0.81 mmol) and Ph3P (212 mg, 0.87 mmol) were added and the mixture was stirred at r.t. for about 10-15 min. The mixture was cooled to 0 °C and I2 (137 mg, 0.54 mmol) was added. After 1 h, 1 M HCl was added. The mixture was diluted with CH2Cl2, washed with H2O and brine, dried over Na2SO4, and concentrated under reduced pressure to give the crude iodide. To a stirred solution of the iodide in THF (5 mL), a mixture of TBAF (92 mg, 0.35 mmol) and hexamethyldisilathiane (85 µL, 0.41 mmol) in THF (5 mL) were added and the mixture was stirred at 0 °C for 30 min before being allowed to warm to r.t. After 12 h, 1 M HCl was added. The mixture was diluted with CH2Cl2, washed with sat. NH4Cl solution, H2O and brine, dried over Na2SO4, and concentrated under reduced pressure. Purification by column chromatography (70% EtOAc-hexanes) gave pure 2a in 45% yield over both steps. 1H NMR (CDCl3): δ = 0.65-1.15 (m, 6 H), 1.32-1.58 (m, 2 H), 1.88-1.98 (m, 2 H), 2.19-2.42 (m, 4 H), 3.42 (t, J = 6.8 Hz, 2 H), 3.61-3.82 (m, 4 H), 6.87-7.38 (m, 18 H), 7.78-7.95 (m, 8 H). 13C{1H} NMR (CDCl3): δ = 24.82, 25.95, 26.67, 27.25, 32.48, 51.45, 54.30, 62.50, 65.35, 113.96, 118.85, 123.45, 124.30, 125.18, 125.36, 126.48, 127.10, 128.25, 129.59, 130.45, 151.78, 154.48. MS: m/z = 760 [M+]. HRMS: m/z calcd for C50H47NO4S: 760.3477; found: 760.3461.
Compound 2b: 40% yield. 1H NMR (CDCl3): δ = 0.65-1.18 (m, 14 H), 1.62-1.78 (m, 2 H), 1.80-2.02 (m, 2 H), 2.18-2.45 (m, 4 H), 3.15 (t, J = 6.8 Hz, 2 H), 3.50-3.78 (m, 4 H), 6.87-7.42 (m, 18 H), 7.58-7.94 (m, 8 H). 13C{1H} NMR (CDCl3): δ = 24.95, 26.10, 26.98, 29.30, 31.90, 51.49, 54.60, 63.28, 65.15, 114.85, 116.64, 116.38, 119.05, 123.35, 124.26, 125.18, 125.37, 126.50, 127.21, 128.18, 129.50, 130.67, 134.50, 151.85, 154.49. MS: m/z = 816 [M+]. HRMS: m/z calcd for C54H55NO4S: 816.3744; found: 816.3750.
Compound 2c: 30% yield. 1H NMR (CDCl3): δ = 0.68-1.28 (m, 18 H), 1.38-1.52 (m, 2 H), 1.90-2.18 (m, 2 H), 2.20-2.31 (m, 2 H), 2.38-2.50 (m, 2 H), 3.20 (t, J = 6.8 Hz, 2 H), 3.58-3.67 (m, 4 H), 6.88-7.31 (m, 18 H), 7.73-7.86 (m, 8 H). 13C{1H} NMR (CDCl3): δ = 25.20, 26.25, 27.14, 29.30, 31.89, 32.56, 51.62, 54.59, 63.30, 66.18, 114.89, 116.70, 116.89, 119.36, 123.38, 124.20, 125.19, 125.37, 126.50, 127.20, 128.28, 129.54, 130.87, 134.26, 151.89, 154.60. MS: m/z = 841 [M+]. HRMS: m/z calcd for C55H59NO4S: 841.4165; found: 841.4170.

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To a stirred solution of tetraoctylammonium bromide (36 mg, 0.66 mmol) in CHCl3 (3 mL), HAuCl4 (5 mg, 0.015 mmol) in H2O (2 mL) was added. The mixture was stirred vigorously for approximately 10 min, and separation between the orange-red organic phase and colorless aqueous phase resulted. The organic layer was collected and compound 2b (6 mg, 0.007 mmol) in CHCl3 (2 mL) was added to the organic phase. After an additional 10 min of stirring, a solution of NaBH4 (5.60 mg, 0.147 mmol) in H2O (2 mL) was slowly added. The orange-red color turned to black-brown, and the reaction mixture was vigorously stirred for 3 d. The organic layer was collected, and reduced to 2 mL. Ethanol (100 mL) was then added, and the mixture was kept at 0 °C for 12 h. The precipitated nanocrystals were isolated by centrifugation and washed with EtOH and acetone.