Supporting Information: Visible Light Initiated Thiol-Michael Addition Polymerizations with Coumarin-based Photo-base Generators, Another Photoclick Reaction Strategy Xinpeng Zhang, Weixian Xi, Chen Wang, Maciej Podgórski,,a and Christopher N.Bowman*, Department of Chemical and Biological Engineering, University of Colorado, UCB 596, Boulder, Colorado 80309, United States Contents Experimental Section Materials Coumarin-TMG and coumarin-hexylamine synthesis Characterization Techniques S2 S2-S6 S6-S7 Supporting Data Figure S1. Absorption of coumarin-tmg and lamp emission spectra S7 Figure S2. Photolysis process of coumarin-tmg in acetonitrile S7 Figure S3. Photo decomposition process monitored by 1 H-NMR S8-9 Figure S4. FT-IR monitoring coumarin-tmg photo decomposition Figure S5. Coumarin-TMG quantum yield calculation S9 S10 Figure S6. Model Reaction (Table 1) 1 H-NMR and FT-IR S11-13 Figure S7. Coumarin-TMG catalyzed thiol-michael polymerization S14 Figure S8. Absorption spectra of coumarin-hexylamine S14 S1
Figure S9. Coumarin-TMG catalyzed thiol-epoxy kinetic S15 References Experimental Section Materials: Pentaerythritol tetrakis(3-mercaptopropionate) (PETMP) was donated by Bruno Bock. Divinyl sulfone (DVS) was purchased from Oakwood Chemicals. Phenol red, butyl thioglycolate, butyl 3-mercaptopropionate, furan-2-ylmethanethiol, 1-hexanethiol, mercaptoethaol, 7-dimethylamino-4-methylcoumarin, selenium dioxide, sodium borohydride, carbonyldiimidazole, 1,1,3,3-Tetramethylguanidine were purchased from Sigma-Aldrich. All chemicals were used as received. Coumarin-TMG and Coumarin-hexylamine synthesis Coumarin-OH: A solution of 7-dimethylamino-4-methylcoumarin (2.0 g, 8.65 mmol) and selenium dioxide (1.09 g, 10.0 mmol) in xylene (200 ml) was stirred at reflux for 48 h. Then the solution was cooled to ambient temperature, filtered, and the solvent was evaporated. Methanol (200 ml) and sodium borohydride (320 mg, 8.65 mmol) were added. The mixture was stirred at ambient temperature for 4 h. After that, the solution was neutralized with 1 N HCl, the solution was extracted by DCM, dried over Na 2 SO 4 and purified by flash chromatography (Hexane/Ethyl Acetate=1/1) affording 820 mg (38% yield) of Coumarin-OH as an orange solid. 1 H NMR (400 MHz, Chloroform-d) δ 7.31 (d, J = 9.0 Hz, 1H), 6.55 (dd, J = 9.0, 2.6 Hz, 1H), 6.46 (d, J = 2.6 Hz, 1H), 6.26 (t, J = 1.3 Hz, 1H), 4.81 (d, J = 1.4 Hz, 2H), 3.38 (q, J = 7.1 Hz, 4H), 1.18 (t, J = 7.0 Hz, 6H). 13 C NMR (101 MHz, CDCl3) δ 162.95, 156.25, 155.17, 150.65, 124.53, 108.75, 106.49, 105.49, 97.85, 61.03, 44.83, 12.57. HRMS (ESI) m/z: [M + H]+ calcd for C 14 H 18 NO 3, 248.1278; found, 248.1290. Coumarin-TMG: Coumarin-OH (806 mg, 3.26 mmol) and carbonyldiimidazole (634mg, 3.92mmol) was dissolved in 60ml DCM and stirred at reflux qin the dark for 4h. Then a DCM solution of DMAP (198 mg, 1.63 mmol) and 1,1,3,3-Tetramethylguanidine (408 ul, 3.26 mmol) was added and the mixture was stirred in the dark overnight. The mixture was washed Brine, extracted by DCM and dried over Na 2 SO 4 and purified by flash chromatography (DCM/MeOH =10/1) affording 430 mg (34% yield) of Coumarin-TMG as product. 1 H NMR (400 MHz, S2
1.0 1.0 1.0 0.98 0.01 2.03 4.09 6.02 7.317 7.294 7.260CDCl3 7.259 6.560 6.53 6.537 6.531 6.46 6.459 6.263 6.260 6.256 4.816 4.813 3.41 3.393 3.375 3.358 2.830 2.161 2.160 2.03 1.782HDO 1.248 1.23 1.201 1.184 1.16 Chloroform-d) δ 7.37 (d, J = 8.9 Hz, 1H), 6.54 (dd, J = 9.0, 2.6 Hz, 1H), 6.48 (d, J = 2.6 Hz, 1H), 6.26 6.16 (m, 1H), 5.23 (d, J = 1.4 Hz, 2H), 3.39 (q, J = 7.1 Hz, 4H), 2.89 (s, 12H), 1.18 (t, J = 7.1 Hz, 6H). 13 C NMR (101 MHz, CDCl3) δ 166.82, 162.31, 159.47, 156.28, 151.87, 150.53, 124.74, 108.61, 106.58, 106.12, 100.09, 62.03, 44.83, 40.06, 12.56). HRMS (ESI) m/z: [M + H]+ calcd for C 20 H 28 N 4 O 4, 388.2189; found, 388.2198. Coumarin-hexylamine: Coumarin-OH (516 mg, 2.09 mmol) and carbonyldiimidazole (406 mg, 2.51 mmol) was dissolved in 40 ml DCM and stirred at reflux in dark for 4h. Then a DCM solution of DMAP (637 mg, 1.04 mmol) and hexylamine (223 mg, 2.20 mmol) was added and the mixture was stirred in the dark overnight. The mixture was washed Brine, extracted by DCM and dried over Na 2 SO 4 and purified by flash chromatography (Hexanes/Ethyl Acetate = 2/1) affording 502 mg (61 % yield) of Coumarin-TMG as product. 1 H NMR (400 MHz, Chloroform-d) δ 7.30 (d, J = 14.5 Hz, 1H), 6.59 (dd, J = 9.0, 2.6 Hz, 1H), 6.52 (d, J = 2.6 Hz, 1H), 5.23 (d, J = 1.4 Hz, 2H), 4.99 (t, J = 6.0 Hz, 1H), 3.42 (q, J = 7.1 Hz, 4H), 3.24 (td, J = 7.2, 5.9 Hz, 2H), 1.60 1.48 (m, 2H), 1.41 1.27 (m, 6H), 1.22 (t, J = 7.1 Hz, 6H), 0.95 0.86 (m, 3H). 13 C NMR (101 MHz, CDCl3) δ 162.01, 156.20, 155.50, 150.55, 150.46, 124.40, 108.64, 106.10, 97.82, 77.36, 77.04, 76.72, 61.63, 44.77, 41.29, 31.44, 29.85, 26.40, 22.55, 14.02, 12.43.). HRMS (ESI) m/z: [M + H]+ calcd for C 20 H 30 N 2 O 4, 357.22; found, 357.22. 8.0 7.5 7.0 6.5 6.0 5.5 5.0 4.5 4.0 3.5 3.0 f1(pm) 1 H NMR of Coumarin-OH 2.5 2.0 1.5 1.0 0.5 0.0 S3
13 C NMR of Coumarin-OH 1 H NMR of Coumarin-TMG S4
13 C NMR of Coumarin-TMG 1 H NMR of Coumarin-hexylamine S5
13 C NMR of Coumarin-hexylamine Characterization Techniques Light source: Most photo reactions were initiated by an Acticure 4000 mercury lamp with a 400-500 nm bandpass filter. The emission spectrum of lamp with this filter is shown in the Figure S1. The light intensity was determined with a visible light detector. Ultraviolet-Visible Spectroscopy (UV-Vis): UV-Vis tests were conducted on UV-Vis spectrophotometer (Thermo-Fischer Scientific). All sample solutions were examined in PMMA cuvettes with 1 cm light path lengths. Absorbance data was collected in absorbance mode with a bandwidth of 2 nm and a scan speed of 240 nm/min. Fourier Transform Infrared Spectroscopy (FT-IR): Real time IR experiments were performed on FT-IR, Nicolet 670. Samples were injected into the space between two glass slides with 0.050 mm thickness spacers (Model reactions and dark cure test). By measuring IR peak area decreasing at 3100 cm -1, 2560 cm -1, real-time functional group conversion of vinyl sulfone, thiol can be calculated by the ratio of peak area to the peak area prior to the reaction. Dynamic Mechanical Analysis (DMA): mechanical property tests were conducted using TA Instruments Q800 dynamic mechanical analyzer. DMA resins (PETMP/DVS, PETMP/dipeoxy, PETMP/diacrylate networks) were prepared by injecting between two glass sides with 0.45 mm thickness spacers irradiating with Acticure 4000 light source with 400-500 nm bandpass filter. After one hour irradiation with certain light S6
intensity, all samples were post-cured at 60 C for one hour to ensure the maximum reaction conversion attainable. The temperature was ramped at 3 C/min with a frequency of 1 Hz. The glass transition temperature (Tg) was determined by the temperature at the peak of the tan δ curve. Supporting Data Figure S1. Emission spectra of Acticure 4000 mercury lamp with a 400-500 nm bandpass filter. In comparison, 0.5 mm Coumarin-TMG in methanol was also shown. In the plot, the minor emission peak around 405nm of visible irradiation mainly works to trigger the photolysis of coumarin-tmg, which means it will achieve even faster reaction if irradiated with visible light LED source with same light intensity. Figure S2. Photo-behavior of coumarin-tmg in acetonitrile upon visible light irradiation (50 mw/cm 2 at 400-500nm). By comparing the photo-behavior in methanol and acetonitrile, it worth noticing that the bleaching process degree and photolysis speed are different. In acetonitrile, there s no NuH as shown in Scheme 1 so the photolysis mechanism of coumarin-tmg is different and the corresponding photo generated coumarin residue structure is different, which resulted in the difference in the photo-behavior. S7
Coumarin-TMG photo degradation test in CDCl 3 Coumarin-TMG photo degradation test in CD 3 OD S8
Coumarin-TMG photo degradation test in CD 3 CN Figure S3. 1 H-NMR monitors photo-degradation process of coumarin-tmg in different deuterated solvent systems (CDCl 3, CD 3 OD, CD 3 CN). NMR results also showed the photo degradation process when irradiated with 50mW/cm 2 400-500nm light. For all systems, there s a peak at 2.7-3.0 ppm decreasing with irradiation time, which is corresponding to the protected tetramethylguanidine. For another peak at 5.4 ppm from CH 2 linkerage, though not as obviously as the last one, we still can detect the decreasing with time by integration. Photo-decomposition can be conformed in deferent solvent system. However, different type of solvent, depending on its polarity and proticity, greatly affects photo reaction rates as shown in the plots. Figure S4. FT-IR monitoring coumarin-tmg photodecomposition. Relative high concentration coumarin-tmg was made (4M in methanol) compared to the concentration used in UV-Vis test (0.05 mm in methanol). By monitoring carbamate bond cleavage, the photodecarboxylation was studied. Upon visible light irradiation S9
ln C (50 mw/cm 2 at 400-500nm), coumarin-tmg was consumed quantitatively in about 6 min, which indicated a high photolysis rate of coumarin-tmg in high concentration condition. -0.26 0.00 5.00 10.00 15.00 20.00 25.00 30.00-0.44-0.62-0.8-0.98-1.16-1.34-1.52-1.7 Time (min) y = -0.0361x - 0.3668 R² = 0.99195 Figure S5. By monitoring the carbamate bond cleavage, the quantum yield can be calculated as well. Under the assumption that one cleaved carbamate bond releases one base, the quantum yield calculated by this method is 0.044 (±0.004). By dissolving coumarin-tmg in the PETMP, the sample was irradiated with 405 nm 0.8 mw/cm 2 LED light to study the quantum yield. This ln C vs. time plot shows the photodecomposition is first order reaction and by using equation: - d[i] dt 2.303e f [I]I 0l d ln[ I] 2.303 fi 0 = NAVhc dt NAVhc f is the efficiency (quantum yield) of coumarin-tmg is calculated based on standard values (e, molar absorptivity for 405 nm light; [I], initiator concentration; I 0, light intensity; λ, wavelength; N AV, Avogadro s number; h, Planck s constant; c, speed of light). 1 S10
S11
S12
Figure S6. 1 H-NMR and FT-IR results for small molecule thiol-michael test. Experiment procedure: divinyl sulfone, mono-functional thiols and coumarin-tmg were well mixed. After injecting the mixture between two glass slides, the sample was irradiated with 400-500nm, 50 mw/cm 2 light. Thiol conversion was monitored by FT-IR as shown above and right after the photo reactions, the mixture was taken to do 1 H-NMR. By integrating the peak ratio, the amount of divinyl sulfone residue can be determined (around 6.2-6.7 ppm). Combing these two methods, the yields of the photo thiol-michael reactions are able to be achieved, as shown in Table 1. S13
Figure S7. Thiol and vinyl group conversion versus time of stoichiometric mixtures of thiol PETMP/DVS monomers catalyzed by 2 wt% coumarin-tmg using 50 mw/cm 2 light at 400-500 nm. It reveals Coumarin-TMG can catalyze thiol-michael addition polymerization with stoichiometric vinyl and thiol group conversion (final conversion difference is within 5%). Figure S8. Absorption spectra of 0.02 mm coumarin-hexylamine in methanol. The extinction coefficient of Coumarin-hexylamine is 4.8 10 4 M -1 cm -1, which is quite similar to coumarin-tmg. S14
Figure S9. Thiol conversion versus time of stoichiometric mixtures of thiol epoxy polymerization monomers catalyzed by 2 wt% coumarin-tmg using 50 mw/cm 2 light at 400-500 nm at 40. PETMP and diepoxy, bisphenol a diglycidyl ether (diepoxy), were chosen as substrates. The thiol-epoxy polymerization was conducted at relative high temperature to improve the mobility of the monomers and accelerate solubility of coumarin-tmg in the system. References: 1. Cramer, N. B.; Reddy, S. K.; O'Brien, A. K.; Bowman, C. N., Macromolecules 2003, 36, 7964-7969. S15