Supplementary Figure 1. Synthesis of 5-bromo-1,3,3-trimethyl-6 -nitroindolinospirobenzopyran

Transcription

1 Supplementary Figure 1. Synthesis of 5-bromo-1,3,3-trimethyl-6 -nitroindolinospirobenzopyran 1.

2 Supplementary Figure 2. 1 H NMR spectrum of 5.

3 Supplementary Figure 3. 1 H NMR spectrum of 6.

4 Supplementary Figure C NMR spectrum of 6.

5 Supplementary Figure 5. 1 H NMR spectrum of 7.

6 Supplementary Figure C NMR spectrum of 8.

7 Supplementary Figure 7. 1 H NMR spectrum of 1.

8 Supplementary Figure C NMR spectrum of 1.

9 Supplementary Figure 9. Synthesis of bis-spiropyran 2.

10 Supplementary Figure H NMR spectrum of 8.

11 Supplementary Figure C NMR spectrum of 8.

12 Supplementary Figure H NMR spectrum of 9.

13 Supplementary Figure C NMR spectrum of 9.

14 Supplementary Figure H NMR spectrum of 10.

15 Supplementary Figure C NMR spectrum of 10.

16 Supplementary Figure H NMR spectrum of 11.

17 Supplementary Figure C NMR spectrum of 11.

18 Supplementary Figure H NMR spectrum of 12.

19 Supplementary Figure C NMR spectrum of 12.

20 Supplementary Figure H NMR spectrum of 2.

21 Supplementary Figure C NMR spectrum of 2.

22 Supplementary Figure 22. Synthesis of building blocks 3 and 4.

23 Supplementary Figure H NMR spectrum of 3.

24 Supplementary Figure C NMR spectrum of 3.

25 Supplementary Figure C NMR spectrum of 4.

26 Supplementary Figure 26. Control reaction between 1 and phenylboronic acid.

27 Supplementary Figure H NMR spectrum of 1',3',3'-trimethyl-6-nitro-5'- phenylspiro[chromene-2,2'-indoline].

28 Supplementary Figure C NMR spectrum of 1',3',3'-trimethyl-6-nitro-5'- phenylspiro[chromene-2,2'-indoline].

29 Supplementary Figure 29. Infrared spectroscopy analysis of PhotoPAFs, PhotoPAN, and the starting materials. a) Full-range IR spectra of PhotoPAFs, PhotoPAN, and the precursors 1-4. b) Partial IR spectra of several PhotoPAFs. Highlighting the intensity of the ~1340 cm 1 band as a function of the spiropyran content (χ SP, determined by elemental analysis).

30 Supplementary Figure 30. Solid-state NMR studies. a) Solid-state 1 H and 13 C NMR spectra of PhotoPAF-3.6%. b) Solid-state 1 H and 13 C NMR spectra of PhotoPAN. c) Solidstate 1 H and 13 C NMR spectra of precursor 2. d) Solid-state 1 H and 13 C NMR spectra of PhotoPAF-0% (PAF prepared from an equimolar mixture of 3 and 4).

31 Supplementary Figure 31. Thermal gravimetric analysis-differential scanning calorimetry studies. Representative thermal gravimetric analysis and differential scanning calorimetry curves for the heating of a, b) two PhotoPAFs and c) PhotoPAN to 800 C at a heating rate of 20 C min 1.

32 Supplementary Figure 32. Additional TEM images. a) Representative TEM images of PhotoPAFs containing various amounts of spiropyran (χ SP = 2.4%, 3.0%, 3.6%, 8.8%, 11.6%, 13.4%) at different magnifications. b) TEM images of PhotoPAN taken at different magnifications. c) High-resolution TEM image of PhotoPAF-3.6%. The entities comprising the contour of the nanopore (arrows on the left) can be attributed to electron densities of individual phenylene groups. The dimensions of the yellow cartoons on the right correspond to the crystallographic size of the benzene molecule.

33 Supplementary Figure 33. Additional SEM images. Representative SEM images of PhotoPAFs containing various amounts of spiropyran (χ SP = 2.2% (a, b), 2.4% (c, d), 3.0% (e), 11.6% (f, g), 13.4% (h, i)) at different magnifications.

34 Supplementary Figure 34. Normal photochromism in suspensions of PhotoPAN. a) Upon solvation, the MC-rich solid PhotoPAN spontaneously isomerises into an SP-rich PhotoPAN. This solvated PhotoPAN (here, in acetonitrile) displays normal photochromism, analogously to PhotoPAFs and small-molecule spiropyrans that is, the suspensions are colourless and UV-vis spectra do not show any indication of the MC isomer (see gray spectrum below); upon UV irradiation the suspensions turn purple and exhibit red fluorescence. PhotoPAN could also be reversibly protonated to give a suspension of the yellow-coloured MCH + -rich network. b) UV-vis spectra of a suspension of PhotoPAN before (grey) and after (purple) UV irradiation, and after the addition of an acid (yellow). Noteworthy is the low intensity of the MC peak at ~570 nm, indicative of a low yield of the SP MC conversion (compare with, e.g., Fig. 3e). This low yield can be attributed to a peculiar behavior of smallmolecule 2, which does not readily undergo a ring-opening reaction; these findings will be described in depth in a separate report.

35 Supplementary Figure 35. Solid-state photoswitching. a) Effect of high-intensity UV light on small-molecule 1. b) Effect of low-intensity UV light on PhotoPAF-3.6%.

36 Supplementary Figure 36. Copper capture and release: additional experiments. a) UV-Vis spectra of PhotoPAN suspension in acetonitrile before (red) and after (green) sonication with one equivalent of CuCl 2. The band centered at ~420 nm can be attributed to Cu 2+ complexed by MC moieties (e.g. Supplementary Ref. 1). b) Cu 2+ shows no affinity to spiropyran-free PAF ( PhotoPAF-0% ). In this experiment, 0.4 mg CuCl 2 2H 2 O was sonicated with 5 mg of spiropyran-free PAF for 17 min. PAF was removed by centrifugation. We see negligible increase of Cu 2+ in the supernatant. c) Gradual degradation of CuCl 2 2H 2 O dissolved in acetonitrile (0.1 mg / ml) upon exposure to visible light (fluorescent bulb, I ~ 1 mw cm 2 ) under the same conditions as those used in the copper release experiment. In the dark, the same solution doesn t show any signs of decomposition.

37 Supplementary Figure 37: Calculation of the degree of PhotoPAF substitution with spiropyran from elemental analysis data. Structural formulae used for the calculation (see Methods in the main text).

38 Supplementary Methods Synthesis of 4-bromophenylhydrazine (5): the compound was prepared according to a literature procedure (Supplementary Ref. 2). 4-Bromoaniline (10.0 g; 58 mmol) was added to a conical flask containing concentrated hydrochloric acid (100 ml) and the mixture was stirred for 30 min at 0 C. An aqueous solution of NaNO 2 (5.4 g; 78 mmol in 50 ml H 2 O) was added dropwise at 0 C and stirring was continued for 1 h. To the resulting solution of diazonium was added SnCl 2 2H 2 O (34 g; 150 mmol) in concentrated hydrochloric acid (34 ml) at 0 C, and the mixture was stirred vigorously for 1 h at room temperature. The resulting precipitate was collected by filtration, placed on an ice bath and treated with an aqueous NaOH solution (w/w = 5%). The product was extracted with chloroform; the organic extract was washed with a dilute NaOH solution, dried over MgSO 4 and the solvent was evaporated to afford 5 as a pale yellow solid (8.5 g, 78%). 1 H NMR (300 MHz, CDCl 3 ) δ 7.31 (d, J = 8.9 Hz, 2H), 6.71 (d, J = 8.9 Hz, 2H), 5.20 (s, 1H), 3.56 (s, 2H). Synthesis of 5-bromo-2,3,3-trimethyl-3H-indole (6): The compound was prepared according to a literature procedure (Supplementary Ref. 2). A solution of 5 (7.9 g; 42.2 mmol) and 3-methyl-2- butananone (5.5 ml; 51 mmol) in ethanol (45 ml) was refluxed for 3 h. A solution of concentrated (98%) aqueous sulfuric acid (5 ml) in ethanol (40 ml) was then added dropwise and the reaction mixture was refluxed for an additional 3 h. After cooling to room temperature, the reaction mixture was diluted with water (300 ml) and the crude product was extracted with chloroform. Combined organic extracts were dried over MgSO 4, the solvent was evaporated under reduced pressure and crude product was purified by column chromatography on silica using CHCl 3 -MeOH (98:2) as the eluent to afford the pure 6 (8.2 g, 82%) as a yellow oil. 1 H NMR (300 MHz, CDCl 3 ) δ (m, 3H), 2.26 (s, 3H), 1.29 (s, 6H); 13 C NMR (75 MHz, CDCl 3 ) δ 187.8, 152.2, 147.4, 130.1, 124.3, 120.8, 118.3, 53.6, 22.4 (2C), Synthesis of 5-bromo-1,3,3-trimethyl-2-methyleneindoline (7): The compound was prepared according to a literature procedure (Supplementary Ref. 2). A solution of 6 (8.2 g; 34.4 mmol) and methyl iodide (12.2 g, 86 mmol) in acetonitrile (75 ml) was refluxed for 18 h under an argon atmosphere. The solvent was removed under reduced pressure and the residue was triturated with ether (80 ml) to give a powder. The solid was collected by filtration, washed with ether (2 100 ml) and dried under high vacuum. The resulting solid was added to a solution of KOH (22 g) in water (225 ml) and stirred for 30 min. The product was extracted with ether and the combined organic extracts were washed with brine, dried over MgSO 4 and evaporated under reduced pressure to afford the desired product, 7 (7.5 g, 86%), as a yellow oil (which gradually turned pink). 1 H NMR (300 MHz, CDCl 3 ) δ 7.21 (dd, J = 8.1, 1.8 Hz, 1H), 7.15 (d, J = 1.8 Hz, 1H), 6.39 (d, J = 8.1 Hz, 1H), 3.86 (s, 2H), 3.01 (s, 3H), 1.33 (s, 6H); 13 C NMR (75 MHz, CDCl 3 ) δ 161.8, 145.3, 139.7, 130.0, 124.9, 110.2, 106.1, 74.1, 44.0, 29.7 (2C), Synthesis of 5-bromo-1,3,3-trimethyl-6 -nitro-indolinospirobenzopyran (1): 7 (2.6 g; 10.3 mmol) was dissolved in ethanol (160 ml) and refluxed with 2-hydroxy-5-nitrobenzaldehyde (2.24 g; 13.4 mmol) under a nitrogen atmosphere for 15 h. The reaction mixture was then cooled to room temperature and the solvent was removed under reduced pressure. The residue was purified by column chromatography on silica using EtOAc-hexane (5:95) as the eluent to afford the pure product, 1 (3.3 g, 80%), as a crystalline solid. 1 H NMR (300 MHz, CDCl 3 ) δ (m, 2H), 7.29 (dd, J = 8.2, 2 Hz, 1H), 7.16 (d, J = 2 Hz, 1H), 6.94 (d, J = 10.4 Hz, 1H), 6.77 (d, J = 8.6 Hz, 1H), 6.43 (d, J = 8.2 Hz, 1H), 5.83 (d, J = 10.4 Hz, 1H), 2.71 (s, 3H), 1.27 (s, 3H), 1.18 (s, 3H); 13 C NMR (75 MHz, CDCl 3 ) δ 159.3, 146.7, 140.9,

39 138.4, 130.3, 128.5, 125.8, 124.7, 122.6, 120.9, 118.4, 115.3, 111.3, 108.5, 106.1, 52.1, 28.8, 25.6, HRMS (m/z): [M+Na] + calcd. for C 19 H 17 N 2 O 3 79 BrNa, ; found, Synthesis of 4,4'-dibromo-2,2'-dinitro-1,1'-biphenyl (8): The compound was prepared according to a literature procedure (Supplementary Ref. 3). A mixture of 1,4-dibromo-2-nitrobenzene (25 g; 89 mmol) and activated copper powder (14 g; 220 mmol) in 90 ml of DMF were stirred for 3 h at 120 C under a nitrogen atmosphere. After cooling to room temperature, 120 ml of toluene was added to the reaction mixture and the solution was stirred for several minutes. The resulting brown residue was filtered off and the organic layer was washed with water and brine, dried over MgSO 4, and the solvent was evaporated under reduced pressure. Recrystallisation from ethanol yielded 8 (14.4 g; 35.8 mmol; 80%) as a light brown solid. 1 H NMR (300 MHz, CDCl 3 ): δ 8.38 (d, J = 2.0 Hz, 2H), 7.83 (dd, J = 8.2, 2.0 Hz, 2H), 7.16 (d, J = 8.2 Hz, 2H); 13 C NMR (75 MHz, CDCl 3 ): δ (2C), (2C), (2C), (2C), (2C), (2C). Synthesis of 4,4'-dibromo-[1,1'-biphenyl]-2,2'-diamine (9): The compound was prepared according to a literature procedure (Supplementary Ref. 3). Solid SnCl 2 (48 g; 253 mmol) was added to a stirred mixture containing 8 (12.0 g; 29.9 mmol), concentrated HCl (60 ml) and ethanol (100 ml). The reaction mixture was heated to reflux and refluxed for 12 h. It was then poured into 300 ml of cold water, and an aqueous NaOH solution (c = 2 mol L 1 ) was added until ph = 8 was reached. The product was extracted several times with diethyl ether, organic fractions were combined, washed with water, dried over MgSO 4, and the solvent was evaporated under reduced pressure. Recrystallisation from ethanol gave 9 (8.5 g; 24.9 mmol; 83%) as a light yellow solid. 1 H NMR (300 MHz, CDCl 3 ): δ 6.93 (s, 6H), 3.75 (br, 4H); 13 C NMR (75 MHz, CDCl 3 ) δ (2C), (2C), (2C), (2C), (2C), (2C). Synthesis of (4,4'-dibromo-[1,1'-biphenyl]-2,2'-diyl)bis(hydrazine) (10): 9 (7.6 g; 22.2 mmol) was added to a conical flask containing concentrated hydrochloric acid (75 ml) at 0 C, and the reaction mixture was stirred for 30 min. An aqueous solution (18 ml) of NaNO 2 (4.0 g; 58 mmol) was then added dropwise and the resulting mixture was stirred for 1 h at 0 C. Urea (180 mg; 3.0 mmol) was added and the solution was stirred for 10 min, after which SnCl 2 (23.0 g; mmol) in concentrated hydrochloric acid (27 ml) pre-cooled to 0 C was added dropwise over 30 min. After 4 h stirring at 0 C the solution was slowly warmed to room temperature over a period of 30 min. The solids that precipitated were collected by filtration and they were treated with a cold (0 C) aqueous solution of NaOH until ph = 10. The mixture was extracted several times with dichloromethane, the organic extracts were washed with dilute NaOH, dried over MgSO 4, and the solvent was evaporated to afford 10 (6.2 g; 16.7 mmol; 75%), which was used for the next step without purification. 1 H NMR (300 MHz, CDCl 3 ): δ 7.34 (d, J = 1.8 Hz, 2H), 6.96 (dd, J = 8.0, 1.8 Hz, 2H), 6.85 (d, J = 8.0 Hz, 2H), 5.14 (br, 2H), 3.47 (br, 4H); 13 C NMR (75 MHz, CDCl 3 ): δ (2C), (2C), (2C), (2C), (2C), (2C). MS (ESI) (m/z): (M+Na, 32%), (36), (100), (26). Synthesis of 4,4'-dibromo-2,2',3,3,3',3'-hexamethyl-3H,3'H-7,7'-biindole (11): A solution of 10 (2.00 g; 5.4 mmol) and 3-methyl-2-butananone (1.50 ml; 1.20 g; 13.9 mmol) in ethanol (10 ml) was refluxed for 3 h. After cooling to room temperature, a solution of concentrated sulfuric acid (1.60 ml) in ethanol (8 ml) was added dropwise, and the reaction mixture was refluxed for an additional 3 h. The reaction mixture was cooled to room temperature and the solvent was removed under reduced pressure. Water was added and the crude product was extracted three times with dichloromethane. Combined organic extracts were washed with brine, dried over MgSO 4, and the

40 solvent was evaporated under reduced pressure. The residue was purified by column chromatography on silica using CHCl 3 -MeOH (99:1) as the eluent to afford pure 11 (2.00 g; 4.22 mmol; 78%) as a pale yellow solid. 1 H NMR (300 MHz, CDCl 3 ): δ 7.55 (d, J = 8.3 Hz, 2H), 7.38 (d, J = 8.3 Hz, 2H), 2.25 (s, 6H), 1.47 (s, 12H); 13 C NMR (75 MHz, CDCl 3 ) δ (2C), (2C), (2C), (2C), (2C), (2C), (2C), (2C), (4C), (2C). HRMS (m/z): M+H] + calcd. for C 22 H 23 N 2 79 Br 81 Br, ; found, Synthesis of 4,4'-dibromo-1,1',3,3,3',3'-hexamethyl-2,2'-dimethylene-7,7'-biindoline (12): A solution of 11 (1.80 g; 3.8 mmol) and methyl iodide (1.2 ml; 2.74 g; 19.3 mmol) in acetonitrile (15 ml) was refluxed for 18 h under nitrogen atmosphere. The solvent was removed under reduced pressure and the residue was triturated with diethyl ether. The solid was collected by filtration, washed with diethyl ether and dried under high vacuum. The resulting solid was added to an aqueous solution of KOH and stirred with THF (60 ml) for 1 h until it completely dissolved. Crude product was extracted with ethyl acetate (three times). Combined organic extracts were dried over MgSO 4 and the solvent was evaporated under reduced pressure. The residue was purified by column chromatography on silica using pure CHCl 3 to afford the desired product 12 (1.45 g; 2.89 mmol; 76%). 1 H NMR (300 MHz, CDCl 3 ): δ 6.89 (d, J = 8.2 Hz, 2H), 6.83 (d, J = 8.2 Hz, 2H), 3.88 (d, J = 2.1 Hz, 2H), 3.83 (d, J = 2.1 Hz, 2H), 2.64 (s, 6H), 1.55 (s, 6H), 1.51 (s, 6H); 13 C NMR (75 MHz, CDCl 3 ): δ (2C), (2C), (2C), (2C), (2C), (2C), (2C), (2C), (2C), (2C), (2C), (2C). HRMS (m/z): [M+H] + calcd. for C 24 H 27 N 2 79 Br 81 Br, ; found, Synthesis of 2: A solution of 12 (1.00 g, 2.0 mmol) and 2-hydroxy-5-nitrobenzaldehyde (0.87 g; 5.2 mmol) in ethanol (70 ml) was refluxed under a nitrogen atmosphere for 15 h. The reaction mixture was then cooled to room temperature and the solvent was removed under reduced pressure. The solid residue was dissolved in 150 ml of dichloromethane and washed three times with an aqueous NaOH solution (100 ml; three times). The organic phase was dried over MgSO 4 and the solvent was evaporated under reduced pressure. The residue was dissolved in a minimum amount of dichloromethane and the product was precipitated using hexane. Repeated precipitation with hexane from chloroform afforded 2 (1.25 g; 1.56 mmol; 78%) as a white amorphous solid. 1 H NMR (300 MHz, CD 2 Cl 2 ): δ 7.97 (d, J = 2.7 Hz, 2H), 7.51 (dd, J = 9, 2.7 Hz, 2H), 6.98 (d, J = 10.4 Hz, 2H), 6.93 (d, J = 8.2 Hz, 2H), 6.83 (d, J = 8.2 Hz, 2H), 6.18 (d, J = 9 Hz, 2H), 5.79 (d, J = 10.4 Hz, 2H), 2.50 (s, 6H), 1.42 (s, 6H), 1.28 (s, 6H); 13 C NMR (75 MHz, CD 2 Cl 2 ): δ (2C), (2C), (2C), (2C), (2C) (2C), (2C), (2C), (2C), (2C), (2C), (2C), (2C), (2C), (2C), (2C), (2C), (2C), (2C). HRMS (m/z): [M+Na] + calcd. for C 38 H 32 N 4 O 6 79 Br 81 Br, ; found, Synthesis of tetrakis(4-bromophenyl)silane (3): The compound was prepared according to a literature procedure 18. A solution of n-buli (c = 2.5 M in hexane) (9.2 ml; 23 mmol) was added dropwise at room temperature to a stirred solution of 1-bromo-4-iodobenzene (6.5 g; 23 mmol) in pentane (65 ml) and stirred for an hour. The resulting suspension was centrifuged (5 min at 2400 rpm), and the supernatant was removed with a syringe. Fresh pentane (70 ml) was added to the residue. After stirring the suspension for 5 min, the mixture was centrifuged and supernatant was removed. Finally, 50 ml of dry pentane were added to yield a suspension of 1-bromo-4-lithiobenzene (~23 mmol). A solution of SiCl 4 in pentane (c = 0.2 M) (25 ml: 5 mmol) was then added dropwise to the above suspension and stirring was continued for 4 h at room temperature. The reaction mixture was quenched with methanol (5 ml) and the solvent was evaporated. The resulting residue was dissolved in dichloromethane (100 ml); water (20 ml), and a saturated aqueous

41 NH 4 Cl aqueous solution (2 ml) were added. The product was extracted from the aqueous phase with dichloromethane (2 50 ml), and combined organic extracts were washed with brine, dried over MgSO 4 and filtered. The filtrate was concentrated to dryness. The residue was dissolved in chloroform (20 ml) and addition of this solution to ethanol (100 ml) resulted in the precipitation of 3 as a white crystalline solid (2.6 g; 80%). 1 H NMR (300 MHz, CDCl 3 ) δ 7.54 (d, J = 8.2 Hz, 8H), 7.34 (d, J = 8.3 Hz, 8H); 13 C NMR (75 MHz, CDCl 3 ) δ (2C), (2C), 131.4, Synthesis of (silanetetrayltetra-4,1-phenylene)tetrakisboronic acid (4): The compound was prepared according to a literature procedure 19. A stirred solution of 3 (1.3 g; 1.99 mmol) in THF (125 ml) at 78 C was treated with a solution of n-buli (c = 2.5 M in hexane) (6.4 ml; 16 mmol) under a nitrogen atmosphere. The resulting reaction mixture was stirred at 78 C for 30 min and then triisopropyl borate (5.5 ml; 23.8 mmol) was added dropwise. The mixture was stirred at 78 C for 20 min and then at 25 C for 1 h. The reaction mixture was acidified with an aqueous solution of HCl (c = 1 M) (25 ml) and it was concentrated by partial evaporation of the volatiles under reduced pressure. The concentrate was treated with aqueous solution of NaOH (c = 1 M) and filtered. The filtrate was acidified with an aqueous solution of HCl (c = 1 M) to yield a white solid precipitate, which was collected by filtration and dried in air to afford 4 (0.84 g; 82%). 1 H NMR (300 MHz, DMSO-d 6 ) δ 8.14 (s, 8H), 7.81 (d, J = 8.0 Hz, 8H), 7.43 (d, J = 8.0 Hz, 8H); 13 C NMR (75 MHz, DMSO-d 6 ) δ 135.9, 135.4, (2C), (2C). Suzuki cross-coupling reaction between 1 and phenylboronic acid: We performed this control reaction to verify that the aryl bromide 1 undergoes the Suzuki cross-coupling reaction under the reaction conditions employed for the synthesis of PhotoPAFs. A 10 ml flask was charged with 1 (100.3 mg, 0.25 mmol), phenylboronic acid (34.1 mg; 0.28 mmol), Pd(PPh 3 ) 4 (28.9 mg; mmol) and potassium carbonate (172.7 mg; 1.25 mmol). To the stirred solid mixture under a nitrogen atmosphere was added H 2 O (1.2 ml) followed by THF (1.2 ml) and the reaction mixture was refluxed for 2 days at 75 C. Solvent was removed under reduced pressure and the residue was extracted three times with CH 2 Cl 2 and water. Combined organic extracts were dried over MgSO 4, the solvent was evaporated under reduced pressure and the residue was purified by column chromatography on silica using hexane-ether (95:15) as the eluent to afford pure product. 1 H NMR (300 MHz, CDCl 3 ) δ (m, 2H), (m, 2H), (m, 3H), (m, 2H), 6.94 (d, J = 10.4 Hz, 1H), 6.80 (d, J = 10.1 Hz, 1H), 6.63 (d, J = 8.1 Hz, 1H), 5.88 (d, J = 10.4 Hz, 1H), 2.78 (s, 3H), 1.35 (s, 3H), 1.24 (s, 3H); 13 C NMR (75 MHz, CDCl 3 ) δ 159.7, 147.2, 141.6, 141.0, 136.8, 133.2, (2C), 128.3, 126.8, (2C), 126.3, 125.9, 122.7, 121.5, 120.6, 118.6, 115.5, 107.2, 106.5, 52.3, 28.9, 26.0, 20.0.

42 Supplementary References 1 Fries, K. H.; Driskell, J. D.; Samanta, S.; Locklin, J. Spectroscopic Analysis of Metal Ion Binding in Spiropyran Containing Copolymer Thin Films. Anal. Chem. 82, (2010). 2 Niu, C., Song, Y. & Yang, L. Synthesis of 5'-functionalized indolinospiropyrans with vinylene unit as linker. Chin. J. Chem. 27, (2009). 3 Liu, R.-S. et al. Novel red light-emitting polymers based on 2,7-carbazole and thiophene derivatives. Chin. J. Polym. Sci. 26, (2008).