In situ reaction monitoring reveals a diastereoselective ligand exchange. Supporting Information

Transcription

1 In situ reaction monitoring reveals a diastereoselective ligand exchange reaction between the intrinsically chiral Au 38 (SR) 24 and chiral thiols - Supporting Information Stefan Knoppe, 1 Raymond Azoulay, 1 Amala Dass 2 and Thomas Bürgi 1,* 1: Department of Physical Chemistry, University of Geneva, 30 Quai Ernest-Ansermet, 1211 Geneva 4, Switzerland 2: Department of Chemistry and Biochemistry, University of Mississippi, 352 Coulter Hall, University, MS, United States S-1

2 A. Synthesis of 1,1 -binaphthyl-2,2 -dithiol (BINAS) 1,2 All reactions were performed under inert gas atmosphere. The glassware used was set under vacuum and heated to remove traces of water prior to use. Solvents were degassed. In the following we describe the synthesis of R-BINAS. The synthesis of S-BINAS was performed accordingly, starting from S-BINOL (data not shown here). 1) R-1,1 -Binaphthalene-2,2 -diyl O,O -bis(n,n -dimethylthiocarbamate) R-BINOL (5 g, mmol) was placed in a Schlenk tube (dried and set under nitrogen) and dissolved in 60 ml of degassed DMF. The solution was cooled to 0 C (solution A). In a second Schlenk tube, sodium hydride (0.92 g, 38.3 mmol) was dissolved in 20 ml of degassed DMF and cooled to 0 C (solution B). In a third Schlenk tube, N,N -dimethylthiocarbamoyl chloride (4.73 g, 38.3 mmol) were dissolved in 20 of degassed DMF and cooled to 0 C (solution C). At 0 C, solution B was transferred into solution A with the aid of a canulla. The combined solution was stirred at 0 C for 5 minutes. Solution C was transferred into the combined solutions A and B at 0 C. After this, the reaction mixture was heated to 85 C over the course of one hour. After two hours at 85 C, the reaction was controlled by thin layer chromatography (no BINOL was found) and allowed to cool down to room temperature. 150 ml of a 3 % aqueous potassium hydroxide solution were added and a white precipitate formed. The precipitate was washed with water and filtered. The crude product was dissolved in methylene chloride and dried over magnesium sulfate. The magnesium sulfate was separated by filtration and the organic phase was concentrated to dryness. After this, the product was purified with column chromatography (CHCl 3 ). Yield: 6.5 g (81 % with respect to R-BINOL). S-2

3 2) R-1,1 -Binaphthalene-2,2 -diyl S,S -bis(n,n -dimethylthiocarbamate) major minor The product from step 1 (5.8 g, 12.6 mmol) was placed into a Schlenk tube and set under nitrogen. A heating mantle was heated to 285 C for 30 min and the Schlenk tube was set into the mantle. The neat reactant melted and the temperature was maintained for 20 minutes until the substrate was not found any more in thin layer chromatography control. After cooling down to room temperature, the crude product was purified using column chromatography (silica, chloroform) and recrystallized from methylene chloride and hexane to yield a white solid. Yield: 4.5 g (77.5 %, major, desired) and 0.8 g (minor, yellow solid). If the Schlenk tube is slowly heated to the reaction temperature, the undesired minor product is formed with 50 % yield. 3) R-1,1 -Binaphthyl-2,2 -dithiol Lithium aluminium hydride (0.99 g, mmol) were placed in a Schlenk tube and dissolved in 60 ml degassed THF. The product from step 2 (2 g, 4.34 mmol) was dissolved in 20 ml THF and added. The S-3

4 reaction mixture was refluxed for four hours (reaction control by TLC). The work-up was performed under nitrogen and all compounds were added in a nitrogen stream. All transfers were made using canulas. The reaction mixture was cooled down to -10 C and hydrolyzed with water (ca 35 ml) and a white precipitate formed. The mixture was acidified with concentrated sulfuric acid (ca 2 ml) until the precipitate redissolved. The mixture was extracted with diethyl ether and the phases were separated. The organic phase was dried over magnesium sulfate, filtered and concentrated to dryness in vacuo. The product was recrystallized from methylene chloride and hexane to yield a yellow solid. Yield: 800 mg (58 %). 1 H-NMR (500 MHz, CDCl 3 ): δ = (s, 2H, SH), (d, 2H, CH Ar ), (m, 4H, CH Ar ), (m, 2H, CH Ar ), (d, 2H, CH Ar ), (m, 4H, CH Ar ) ppm. 13 C-NMR (125 MHz, CDCl 3 ): δ = (C Ar ), (C Ar ), (C Ar ), (C Ar ), (C Ar ), (C Ar ), (C Ar ), (C Ar ), (C Ar ), (C Ar ) ppm. S-4

5 Figure S-1. 1 H-NMR spectrum (500 MHz, CDCl 3 ) of R-BINAS. The signal at 1.51 ppm is residual water; the signal at 5.3 ppm is methylene chloride. Figure S C-NMR spectrum (125 MHz, CDCl 3 ) of R-BINAS. The inset shows the region from ppm. S-5

6 B. Ligand Exchange between rac-au 38 (SCH 2 CH 2 Ph) 24 and R-BINAS Synthesis and Size-Selection. Synthesis and size-selection of monodisperse rac-au 38 (2-PET) 24 clusters were performed as reported earlier. 3-6 The isolated clusters were characterized by UV-Vis (not shown), MALDI mass spectrometry 7 (not shown) and HPLC. 8 Ligand Exchange Reactions. rac-au 38 (2-PET) 24 (15 mg) was dissolved in toluene at a concentration of 1 mg/ml. A 100-fold molar excess (with respect to Au 38 ) of enantiopure R-BINAS was added. 1.5 ml of this solution was transferred to a sample vial for in situ HPLC monitoring. Reactions on the enantiopure clusters were performed without determination of concentrations and the amount of BINAS was not weighed since very small amounts of material were used. Separation of the enantiomers was performed as described earlier. 8,9 HPLC. HPLC was performed on a JASCO 20XX HPLC system equipped with a Phenomenex Lux Cellulose-1 column (5 µm, 250 x 4.6 mm). Hexane : isopropanol (8:2) was used as mobile phase. For in situ reaction monitoring, ligand exchange was performed in a sample vial (1.5 ml) and injected (9 µl) to the HPLC system every 1.5 h over the course of 79 h. The UV-detector wavelength was set to 630 nm. The clusters were eluted at 1.8 ml/min and the column was kept at 28 C with a Thermasphere TS-430 HPLC column chiller/heater. S-6

7 C. Program Code of the MATLAB routine The rate law for the consecutive reaction is: d [( 38,24,0) ] dt = - k 1 * [( 38,24,0) ] This assumption is justified since ln[(c-38, 24, 0)] vs t gives a linear correlation (not shown). File 1: kinfittb.m % Fits data to kinetics defined in kinet using least squares in myfun % Thomas Bürgi , Department of Chemistry, University of Geneva, % Switzerland clear all type kinet type myfun global xdata global ydata global y0 % initial concentrations y0 = zeros(2,1); y0(1,1) = 1.0; y0(2,1) = 0.0; [( 38,22,1) ] % import data from file "data.txt" % e.g % % % % % % % % first row is time, following are concentrations of species mydata = importdata ('data.txt') xdata=mydata(:,1); ydata(:,1)=mydata(:,2); ydata(:,2)=mydata(:,3); % Time span of the simulation tspan = [0 500]; % estimation of kinetic constants k0 = zeros(2,1); k0(1,1) = 0.02; k0(2,1) = 0.001; d dt [( 38,24,0) ] [( 38,22,1) ] = k 1 * k 2 % solve problem [k,resnorm,residual,exitflag,output,lambda,jacobian] = lsqcurvefit(@myfun,k0,xdata,ydata); S-7

8 ci = nlparci(k,residual,'jacobian',jacobian); % generate kinetic curves with fitted parameters ode kinet(t,y,k); [t,y] = ode45(ode, tspan, y0); % plot data plot(xdata,ydata(:,1),'ro',xdata,ydata(:,2),'bo',t,y(:,1),'r',t,y(:,2),'b') xlabel('time') ylabel('concentrations') % prepare for output writing kerr = [k,ci] reswrite = [t,y] inpwrite = [xdata,ydata] % write to excel file % sheet one: fitted kinetics % sheet two: input data % sheet three: kinetic constants and 95% confidence intervals xlswrite('results.xls', reswrite, 1, 'A1') xlswrite('results.xls', inpwrite, 2, 'A1') xlswrite('results.xls', kerr, 3, 'A1') File 2: kinet.m function dydt = kinet(t,y,k) dydt(1,1) = [-k(1,1)*y(1,1)]; dydt(2,1) = [k(1,1)*y(1,1)] - [k(2,1)*y(2,1)]; File 3: myfun.m function F = myfun(k,xdata) global ydata global y0 tspan = [xdata]; ode kinet(t,y,k); [t,y] = ode45(ode, tspan, y0); F=y; Instructions: 1) copy all files into one directory 2) create a file data.txt containing the concentrations a. Column A: time (x-axis) b. Column B: input concentrations 1 c. Column C: input concentrations 2 S-8

9 d. Separate the columns with a tab-stop 3) open kinfittb.m with MATLAB and run the program 4) the program creates a.xls file containing three sheets a. Sheet 1: data gained from the fit i. Column A: time (x-axis) ii. Column B: concentration of parameter 1 (fit data, y-axis) iii. Column C: concentration of parameter 2 (fit data, y-axis) b. Sheet 2: input data (as in data.txt ) i. Column A: time (x-axis) ii. Column B: concentration of parameter 1 (y-axis) iii. Column C: concentration of parameter 2 (y-axis) c. Sheet 3: rate constants i. Column A: rate constants 1. row 1: rate constant k 1 ii. Column B: 2. row 2: rate constant k 2 1. row 1: lower 95 % confidence interval for k 1 iii. Column C: 2. row 2: lower 95 % confidence interval for k 2 1. row 1: upper 95 % confidence interval for k 1 2. row 2: upper 95 % confidence interval for k 2 S-9

10 References (1) Fabbri, D.; Delogu, G.; De Lucchi, O. The Journal of Organic Chemistry 1993, 58, (2) He, H.; Chen, L.-Y.; Wong, W.-Y.; Chan, W.-H.; Lee, A. W. M. European Journal of Organic Chemistry 2010, 2010, (3) Knoppe, S.; Dharmaratne, A. C.; Schreiner, E.; Dass, A.; Burgi, T. J Am Chem Soc 2010, 132, (4) Knoppe, S.; Boudon, J.; Dolamic, I.; Dass, A.; Burgi, T. Anal Chem 2011, 83, (5) Qian, H.; Zhu, M.; Andersen, U. N.; Jin, R. The Journal of Physical Chemistry A 2009, 113, (6) Qian, H., Zhu, Y., Jin, R. ACS Nano 2009, 3, 3795 (7) Dass, A.; Stevenson, A.; Dubay, G. R.; Tracy, J. B.; Murray, R. W. J Am Chem Soc 2008, 130, (8) Dolamic, I.; Knoppe, S.; Dass, A.; Bürgi, T. Nature Communications 2012, 3, 798. (9) Knoppe, S.; Dolamic, I.; Burgi, T. J Am Chem Soc 2012, 134, S-10