S1 SUPPORTING INFORMATION Chiroptical Activity of BINAP ...
SUPPORTING INFORMATION Chiroptical Activity of BINAP-Stabilized Undecagold Clusters Yasushi Yanagimoto,† Yuichi Negishi† Hisashi Fujihara‡ and Tatsuya Tsukuda*,†, § Research Center for Molecular-Scale Nanoscience, Institute for Molecular Science, Myodaiji, Okazaki 4448585, Japan. ‡Department of Applied Chemistry and Molecular Engineering Institute, Kinki University, Kowakae, Higashi-Osaka 577-8502, Japan. §CREST, Japan Science and Technology Agency, Kawaguchi, Saitama 3320012, Japan. †
Chemicals All commercially available chemicals were used without further purification.
Sodium
tetrachloroaurate(III) dihydrate (NaAuCl42H2O), chloro(triphenylphoshine) gold(I) (AuCl(TPP)), 2,2’-thiodiethanol (S(C2H4OH)2) and sodium tetrahydroborate (NaBH4) were obtained from Wako Pure Chemical Industries. Potassium tetrabromoaurate(III) hydrate (KAuBr4H2O) and bromo(triphenylphoshine) gold(I) (AuBr(TPP)) were obtained from Avocado Research Chemicals Ltd. and Alfa Aesar, respectively. (R)- and (S)-BINAP were purchased from Aldrich. Synthesis of Au2Br2(R-/S-BINAP) (3R/3S) To an aqueous solution of KAuBr4 (90 mM, 30 ml) at 0 ºC was added 2,2'-thiodiethano (110 mg, 0.90 mmol) over 5 min. After stirring for 1 h, (R)-/(S)-BINAP (280 mg, 0.45 mmol) in chloroform (3.6 mL) was injected at 0 ºC under nitrogen atmosphere. After vigorous stirring for 3 h, the resulting mixture was extracted with chloroform and organic layer was concentrated by rotary evaporation. The residue was reprecipitated from a chloroform solution by hexane. Finally, the precipitated was purified with silica gel chromatography with chloroform as eluent to obtain 3R/3S as a white crystalline powder in 54 % yield. Characterization. The Au:BINAP (4 and 5) and Au:TPP (6 and 7) clusters thus synthesized were characterized as follows. UV-vis absorption and CD spectra were recorded in chloroform at ambient temperature by using a double-beam spectrophotometer (U-2010, HITACHI) and a spectropolarimeter (720w, JASCO), respectively. Transmission electron microscopy (TEM) images were acquired with an electron microscope operated at 100 kV (H-7500, HITACHI). The TEM specimens were prepared by dropcasting one or two drops of the chloroform solutions onto a carbon–coated collodion film supported on a copper grid. Typical magnification of the images was 100,000. The chemical compositions were investigated by using an electrospray ionization (ESI) mass spectrometer (JMS-T1000LC, JEOL). The ESI spectra of methanol solutions of the Au clusters were recorded in the positive-ion mode. The ESI mass spectra obtained were calibrated with reference to that of NanIn+1+ cluster cations recorded under the same conditions.
S1
ESI mass spectrum of 4 ESI mass spectrum of 4 is shown in Figure S1. 2+
[Au11(BINAP)4Cl]
2+
+
and [Au11(BINAP)4Cl2] .
The spectrum exhibits peaks assignable to
Three peaks due to Br impurities are additionally observed:
+
[Au11(BINAP)4Br] , [Au11(BINAP)4ClBr] , and [Au11(BINAP)4Br2]+.
Figure S1. Positive-ion ESI mass spectrum of 4R. The bottom panels show the comparisons between the experimental and simulated isotopic patterns of the main peaks.
S2
CD spectra of 4R/4S Figure S2 shows the CD spectra of 4R and 4S. The spectra of 4R/5R and 4S/5S exhibit close similarity.
(a)
(b)
Figure S2. (a) Ellipticity and (b) anisotropy factor of 4.
CD spectra of 3R/3S Figure S3 shows the CD spectra of 3R and 3S. The CD spectra show Cotton effects and a mirror-image relationship in the range 250-350 nm, although their anisotropy factors are only at a ppm level.
Figure S3. (a) Ellipticity and (b) anisotropy factor of 3.
S3
Stability of 5R and 6 in methanol Figure S4(a) shows UV-vis spectra of 6 in chloroform (bleu) and in methanol (green). Cluster 6 once dissolved in methanol shows a spectrum in chloroform (red) significantly different from the original one (blue), suggesting irreversible degradation in methanol. In contrast, the Au:BINAP cluster (5R) is highly stable against methanol as shown in Figure S4(b).
(a)
(b)
Figure S4. UV-vis spectra of Au:TPP (6) and Au:BINAP (5R). Blue, red, and green curves show the spectra in chloroform, methanol, and chloroform after once dissolved in methanol, respectively.
S4
Chemicals All commercially available chemicals were used without further purification.
Sodium
tetrachloroaurate(III) dihydrate (NaAuCl42H2O), chloro(triphenylphoshine) gold(I) (AuCl(TPP)), 2,2’-thiodiethanol (S(C2H4OH)2) and sodium tetrahydroborate (NaBH4) were obtained from Wako Pure Chemical Industries. Potassium tetrabromoaurate(III) hydrate (KAuBr4H2O) and bromo(triphenylphoshine) gold(I) (AuBr(TPP)) were obtained from Avocado Research Chemicals Ltd. and Alfa Aesar, respectively. (R)- and (S)-BINAP were purchased from Aldrich. Synthesis of Au2Br2(R-/S-BINAP) (3R/3S) To an aqueous solution of KAuBr4 (90 mM, 30 ml) at 0 ºC was added 2,2'-thiodiethano (110 mg, 0.90 mmol) over 5 min. After stirring for 1 h, (R)-/(S)-BINAP (280 mg, 0.45 mmol) in chloroform (3.6 mL) was injected at 0 ºC under nitrogen atmosphere. After vigorous stirring for 3 h, the resulting mixture was extracted with chloroform and organic layer was concentrated by rotary evaporation. The residue was reprecipitated from a chloroform solution by hexane. Finally, the precipitated was purified with silica gel chromatography with chloroform as eluent to obtain 3R/3S as a white crystalline powder in 54 % yield. Characterization. The Au:BINAP (4 and 5) and Au:TPP (6 and 7) clusters thus synthesized were characterized as follows. UV-vis absorption and CD spectra were recorded in chloroform at ambient temperature by using a double-beam spectrophotometer (U-2010, HITACHI) and a spectropolarimeter (720w, JASCO), respectively. Transmission electron microscopy (TEM) images were acquired with an electron microscope operated at 100 kV (H-7500, HITACHI). The TEM specimens were prepared by dropcasting one or two drops of the chloroform solutions onto a carbon–coated collodion film supported on a copper grid. Typical magnification of the images was 100,000. The chemical compositions were investigated by using an electrospray ionization (ESI) mass spectrometer (JMS-T1000LC, JEOL). The ESI spectra of methanol solutions of the Au clusters were recorded in the positive-ion mode. The ESI mass spectra obtained were calibrated with reference to that of NanIn+1+ cluster cations recorded under the same conditions.
S1
ESI mass spectrum of 4 ESI mass spectrum of 4 is shown in Figure S1. 2+
[Au11(BINAP)4Cl]
2+
+
and [Au11(BINAP)4Cl2] .
The spectrum exhibits peaks assignable to
Three peaks due to Br impurities are additionally observed:
+
[Au11(BINAP)4Br] , [Au11(BINAP)4ClBr] , and [Au11(BINAP)4Br2]+.
Figure S1. Positive-ion ESI mass spectrum of 4R. The bottom panels show the comparisons between the experimental and simulated isotopic patterns of the main peaks.
S2
CD spectra of 4R/4S Figure S2 shows the CD spectra of 4R and 4S. The spectra of 4R/5R and 4S/5S exhibit close similarity.
(a)
(b)
Figure S2. (a) Ellipticity and (b) anisotropy factor of 4.
CD spectra of 3R/3S Figure S3 shows the CD spectra of 3R and 3S. The CD spectra show Cotton effects and a mirror-image relationship in the range 250-350 nm, although their anisotropy factors are only at a ppm level.
Figure S3. (a) Ellipticity and (b) anisotropy factor of 3.
S3
Stability of 5R and 6 in methanol Figure S4(a) shows UV-vis spectra of 6 in chloroform (bleu) and in methanol (green). Cluster 6 once dissolved in methanol shows a spectrum in chloroform (red) significantly different from the original one (blue), suggesting irreversible degradation in methanol. In contrast, the Au:BINAP cluster (5R) is highly stable against methanol as shown in Figure S4(b).
(a)
(b)
Figure S4. UV-vis spectra of Au:TPP (6) and Au:BINAP (5R). Blue, red, and green curves show the spectra in chloroform, methanol, and chloroform after once dissolved in methanol, respectively.
S4
