Substrate Channeling in Compartmentalized Nanoreactors

Thermo- and photoresponsive nanoreactors based on shell cross-linked micelles (SCMs) for the rhodium-catalyzed asymmetric transfer hydrogenation (ATH) of ketones have been developed from poly(2-oxazoline) triblock terpolymers. The nanoreactors incorporate thermoresponsive poly(2-isopropyl-2-oxazoline) as the hydrophilic corona and are covalently cross-linked with a photoswitchable spiropyran molecule. UV irradiation or changes in temperature trigger morphology switching of the polymer-based nanoreactors that alters the hydrophobicity in separate layers of the SCMs, resulting in dynamic substrate selectivity of the ATH in water. Control experiments and kinetic studies show that the thermoresponsive outer layer induces the gated behavior for more hydrophobic substrates, whereas the photoresponsive cross-linking layer induces the gated behavior for less hydrophobic substrates. The nanoreactors mimic the multichannels in Nature, transporting substrates and reagents into the catalytic core which can be controlled through external triggers such as temperature and light wavelengths. Additionally, the nanoreactors can be easily recovered and reused with continued high activity and selectivities.

Mass spectra of samples in methanol were acquired with an Agilent 6224 Accurate-Mass TOF/LC/MS Spectrometer.
Gel-permeation chromatography (GPC) was carried out using a Shimadzu pump coupled to a Shimadzu RI detector controlled by an EZStart program.A set of polymer standards columns (AM GPC gel, 10 μm, precolumn, 500 Å and linear mixed bed) was used with a 0.03 M LiCl solution in N,N-dimethylformamide at a flow rate of 1 mL/min at 60 °C.The system was calibrated with poly(styrene) standards (EasiCal, Agilent Technologies, Santa Clara, CA).The injection volume was 100 μl and the flow rate was 1 mL/min.Mn app and dispersity (Đ) represent the apparent number-average molecular weight and dispersity index respectively.Hydrodynamic diameters of cross-linked and uncross-linked micelles were determined at 25 °C by dynamic light scattering (DLS) using Malvern Zetasizer nano series with a 663 nm module.
Analytical high performance liquid chromatography (HPLC) was performed on an Agilent 1200 series with a diode array detector (samples analyzed at 210 nm and 280 nm).A Chiracel OD column (Chiral Technologies, Inc.) was used for ee determination.
UV-Vis spectra were recorded with a Cary 100 Bio UV-VIS Spectrophotometer (No. EL06023666) coupled to a Cary Temperature Controller (No. EL06023011).The spectra were recorded without stirring at a wavelength of 700 nm from 20-100 °C, at a heating rate of 1 °C min -1 , with a sample concentration of 0.1 mg/mL in a 1400 μL micro cuvette with stopper (Thor labs #CV10Q1400S) Dialysis was performed using a Spectra/Por 6 dialysis membrane with a MWCO of 2000 Da or 1000 Da.
A 365 nm UV lamp (15W UVP Black Ray UV Bench LampXX-15L) was used for the thiol-ene reactions.
Cryo-TEM grids (quantifoil R1.2/1.3 with 300 mesh copper (Cat.#Q350-CR1.3))were plasma treated for 30 seconds using Denton Vacuum Bench Top Turbo before use.Cryo-TEM grids were prepared in a Leica EM GP at 30 °C with the relative humidity set to 70%. 5 μl of sample was pipetted onto a freshly glow-discharged grid.The sample solution was incubated on the TEM grid for 30 seconds, blotted for 4 seconds before being plunged into liquid ethane that was pre-cooled to -183°C by liquid nitrogen.The cryo-TEM grids were then transferred to and stored in liquid nitrogen.The cryo-TEM grids were transferred in liquid nitrogen into a Gatan 626 cryo-specimen holder and then inserted into the microscope.The specimen temperature was maintained at −170 °C during data collection.Cryo-TEM imaging was performed in a Thermo Fisher Talos 120 C TEM operating at 120 kV on a Gatan One View camera (4k×4k).
FT-IR spectra were recorded on a Nicolet iS50 FT-IR spectrometer, equipped with a Smart iTR ATR accessory.

CROP of triblock copolymer 1
In glove box, a solution of iPrOx (276 µl, 2.32 mmol) in acetonitrile (1.0 mL) was added in an oven-dried 25 mL Schlenk flask.To initiate the polymerization, methyl triflate (MeOTf) (2.53 µl, 0.0232 mmol) was introduced out of the glove box under argon, and slowly lowered into an oil bath preheated at 140 °C.The reaction was stirred for two hours, and the conversion monitored by 1 H-NMR spectroscopy via the disappearance of the monomer signals at 0.8 and 1.7 ppm as well as the appearance of the polymer side-chain signals.After full conversion was confirmed, ButynOx (85.7 mg, 0.696 mmol) was added in glove box and the reaction was stirred for one hour until all monomers was consumed.A solution of TridecanylOx (29.3 mg, 0.116 mmol) in glove box was added to the reaction mixture.The reaction was stirred overnight until full conversion.20 μl of allyl amine were added to terminate the polymerization and the reaction was stirred for an additional hour at 140 °C.The reaction mixture was dialyzed against methanol and lyophilized from H2O.

Self-assembly protocol
The amphiphilic triblock copolymer with a concentration of 1 mg/mL was stirred overnight and self-assembled into nanostructure in different solvent e.g.water and methanol.The hydrodynamic diameter (Dh) was measured via DLS.The z-average Dh was 65 nm and 5 nm, in water (Figure S5, left) and methanol (Figure S5, right), respectively.Wavenumbers (cm-1)

Figure S5
. DLS traces of polymer 1 micelle solution in water (left) and methanol (right) at 1.0 mg/mL filtered with a 0.45 µm syringe filter.

Synthesis of SCM 2 through CuAAC
Polymer 1 (100 mg) was self-assembled into a micelle in water overnight with a concentration of 1 mg/mL.It was then transferred to an oven-dried 500 mL Schlenk flask and sodium ascorbate (39.6 mg, 2 equiv.with respect to Cu catalyst), N, N, N', N'-tetramethylethylenediamine (TMEDA) (18 μl, 1.2 eq. with respect to Cu catalyst), an acetone solution (5 mL) of cross-linker N3-SP-N3 (43.2 mg, 15 equiv.with respect to polymer) were added.The reaction was degassed via three freeze-pump-thaw cycles, filled with N2 and an aqueous solution (3.5 mL) of CuSO4•5H2O (25 mg, 0.5 equiv.with respect to N3 group) was added into reaction mixture under N2 protection.The reaction mixture was stirred at room temperature for five days.The complexation and precipitation of Cu by sodium diethyldithiocarbamate was performed to remove all Cu.Excess amount of sodium diethyldithiocarbamate (DDC) (300 mg) was added into the reaction mixture.After stirring for thirty minutes, the reaction mixture was diluted ten-fold.The formed precipitate was carefully filtered off using 0.45 μm syringe filters and the filtrate was concentrated under reduced pressure.The mixture was dialyzed against methanol and DI water and lyophilized from water to afford a yellow power.A high density of covalent crossing-linking of SCM 2 was confirmed by the disappearance of the characteristic alkyne signals at 1.98 ppm in the 1 H NMR spectrum, at 84.7 and 71.0 ppm in the 13 C NMR spectrum, and the stretch at 3235.6 cm -1 in the IR spectrum (Figure S6, S7, S8).The Dh of the nanostructures change (from 5 nm to 63 nm) in methanol also indicated successful covalent cross-linking of the micelles (Figure S10).The photo-responsiveness of SCM 2 was investigated via DLS in a recycling fashion.SCM 2 was dispersed in water at 1 mg/mL for DLS analysis.The micelle solution was exposed to visible light (l = 550 nm) for 15 minutes and then switched to UV irradiation (l = 350 nm) for 15 minutes.The solution color changes from yellow to purple (Figure S10 inset).Five consecutive UV-Vis switching cycles were performed.The hydrodynamic diameter (Dh) distribution was measured in water via DLS.The micelle solution was filtered with a 0.45 µm syringe filter before DLS measurement.In water, the Dh of SCM 2 under visible light was measured to be between 78 nm and 80 nm.Upon irradiation with UV light, the Dh changed to 68 nm and 70 nm (Figure S9).

Synthesis of SCM 3 through thiol-ene chemistry
A solution of SCM 2 (40 mg) in water (40 mL) was prepared and stirred overnight prior to addition to a 100 mL Schlenk flask.Pentaerythritol tetra(3-mercaptopropionate) (4SH) (1 equiv.with respect to alkene groups, 1.22 mg) was added, followed by 2,2-dimethoxy-2-phenylacetophenone (DMPA) (0.2 equiv., 0.128 mg).The reaction was degassed via three freeze-pump-thaw cycles and subjected to 365 nm UV light while stirring for 24 hours at 4 °C.After dialysis against methanol for two days, the methanol was removed via reduced vacuum and the particles were dispersed in 40 mL water and added to a 100 mL Schlenk flask.Olefin functionalized Rh-TsDPEN (3 equiv.with respect to alkene groups) was added, followed by DMPA (0.2 equiv., 0.128 mg).
The reaction was degassed via three freeze-pump-thaw cycles and subjected to 365 nm UV light while stirring for 24 hours at 4 °C.After dialysis against methanol and then water for two days, SCMs were dried by lyophilization from water.The Rh content was determined by ICP-MS to be 1.1 %, which corresponds to a degree of functionalization of, on average, 1.70 rhodium complexes per polymer chain.The hydrodynamic diameter (Dh) distribution was measured in water via DLS with a concentration of 1 mg/mL filtered with a 0.45 µm syringe filter.Exposure to UV light lasted for 15 minutes, and the irradiation with Vis was for 15 minutes.In H2O, the z-average of Dh under visible light exposure fluctuated between 137 nm and 145 nm, while the z-average of the Dh under UV exposure was between 104 nm and 109 nm.The thermoresponsiveness of SCM 3 was confirmed via thermal UV-Vis spectra, DLS and Cryo-TEM.The SCM 3 was dispersed in water at 0.1 mg/mL for thermal UV-Vis and at 1 mg/mL for DLS and Cryo-TEM.The micelle structure of SCM 3 was investigated at room temperature and at 60 °C.The micelle size became stable after heating for 15 hours.
We also explored the UV-Vis spectra of cross-linker N3-SP-N3 under various conditions (Figure S13).When under visible light, the traces are almost same at 40 °C and at 60 °C.S-14

General procedures and kinetic data for micelle-supported asymmetric transfer hydrogenation (ATH)
SCM 3 (1.9 mg, containing 0.2 μmol Rh-TsDPEN) was weighed into a 4 mL vial.0.6 mL DI water was added, and the mixture was stirred overnight at room temperature until a uniform micelle suspension was obtained.Acetophenone (acp) (0.5 mg, 4 μmol, 1.0 equiv.)and HCOONa (10 eq.2.7 mg) were added to the micelle solution.The mixture was stirred at 40 °C or 60 °C under visible light or UV irradiation.Aliquots (0.1 mL) were taken at certain time intervals to monitor the reaction progress.The aliquots were extracted with 0.2 mL EtOAc twice.After removing volatiles, the crude product was dissolved in CDCl3 and filtered through a pipet silica column.With mesitylene (1 equiv.)as an internal standard added, the crude product was subjected to 1 H-NMR analysis to determine conversions.Three sets of parallel experiments were conducted, and the conversion results were averaged.After use, the nanoreactors can be recycled via dialysis against methanol and water for two days and then lyophilized.
The conversion was determined by comparison of the methine proton of the ketone at 2.59 ppm (1H) with the methine proton of the secondary alcohol at 1.59 ppm in the 1 H-NMR spectrum.
The ATH of other ketones with SCM 3 was carried out using the same procedure as for acp and the products were analyzed by comparing their chiral HPLC and 1 H-NMR data with the literature. 4- S-15

Figure
Figure S6.H-NMR spectra of SCM 2 in solution of CDCl3 and the comparison of polymer 1.The alkyne signals at 1.98 ppm disappeared.Inset: enlargement of 1 H-NMR spectrum of SCM 2 from 4 ppm to ppm shows the presence of the aromatic SP signals.

Figure
Figure S7.C-NMR spectra of SCM 2 in solution of CDCl3 and the comparison of polymer 1.

Figure S8 .
Figure S8.FT-IR spectra of SCM 2 and the comparison with polymer 1.

Figure S9 .
Figure S9.DLS traces of SCM 2 (Red) and comparison with polymer 1 (black) in methanol.Inset: color change of SCM 2 water solution under visible light (yellow) and under UV light exposure for 15 minutes (purple).

Figure S10. SCM 2
Figure S10.SCM 2 size investigation.Left: DLS traces of SCM 2 water solution under UV light exposure (Red) and under visible light exposure (Black).Right: Dh of five consecutive UV-Vis cycles.Black dots represent Dh under visible light exposure and red dots under UV light.

Figure S12 .
Figure S12.Cryo-TEM images of SCM 3 assemble in aqueous media at room temperature at 1 mg/mL.Scale bars: 100 nm

Table S1 .
PDI of each point in Figure1B