Supporting Information. Excited State Relaxation Dynamics of Model GFP Chromophore Analogs: Evidence for cis-trans isomerism

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1 Supporting Information Excited State Relaxation Dynamics of Model GFP Chromophore Analogs: Evidence for cis-trans isomerism Shahnawaz Rafiq, 1 Basanta Kumar Rajbongshi, 1 isanth. air, Pratik Sen,* and Gurunath Ramanathan* Department of Chemistry Indian Institute of Technology Kanpur Kanpur, , UP, India 1-These authors contributed equally for this work. *- to whom correspondence must be addressed FAX ; gurunath@iitk.ac.in; psen@iitk.ac.in; S1

2 General Aspects The melting points were determined in a JSGW melting point apparatus and are uncorrected. Column chromatography was performed with silica gel mesh particle size. TLC analyses were performed with MERK Kieselgel 60 F 254 plates. 1 H MR spectra were recorded in JEL 400 (400 MHz) and JEL 500 (500 MHz) MR spectrometers in solution of CDCl 3 with the solvent as the internal standard. 13 C MR spectra were recorded in JEL 400 (100 MHz) and JEL 500 (125 MHz) MR spectrometers with complete proton decoupling. IR spectra were recorded on a Bruker Vector 22 FT-IR spectrometer. Mass spectral analyses were carried out on a Waters ESI-Q TF instrument. All solvents were purchased from local company - SD Fine Chemicals and were purified by following established procedures. 1 Anhydrous zinc chloride and anhydrous sodium acetate were purchased from SD Fine chemicals and were dried under vacuum before use. Triphenylamine (Sigma- Aldrich) was used as received. It was used in preparation of tripehylamine aldehyde by Vilsmeier-Haack reaction. 2 Acetic anhydride and aniline (SD Fine Chemicals) were distilled prior to use. All other chemicals used in synthesis were purchased from SD Fine Chemicals and used without purification. For spectroscopic studies all the solvents were purchased form Sigma- Aldrich and were used as such. General procedure for preparation of (4Z)-4-arylmethylene-2-phenyl-5(4H)-oxazolones (IIIa-b, Scheme 1). 3,4 A mixture of -benzoylglycine, I (1.0 g, 5.6 mmol, 1 equiv.), paradisubstituted aromatic aldehyde, IIa-b (5.6 mmol, 1 equiv.), anhydrous sodium acetate (0.46 g, 5.6 mmol, 1 equiv.) and acetic anhydride (2.6 ml, 28.0 mmol, 5 equiv.) was refluxed for 2 h. The reaction mixture was cooled to room temperature and 10 ml ethanol added and kept at 0 C for 20 minutes. The deposited solid was filtered under suction and washed with ice-cold ethanol (10 ml 2) and warm water (50 ml). The crude product obtained was dried in vacuum desiccator. The crude product was purified by a short pad silica gel chromatography ( mesh). S2

3 Scheme 1. Synthesis of the GFP chromophore analogs Results: (4Z)-4-(4-,-Dimethylaminobenzylidene)-2-phenyl-5(4H)-oxazolone (IIIa). range powder; Yield 54%; m.p C; IR (KBr) ν max /cm -1 : 1764, 1645, 1606, 1530, 1447, 1374, 1323, 1163, 814; 1 H MR (CDCl 3, 400 MHz): δ3.12 (s, 6H, 2 ), 6.75 (d, J = 8.7 Hz, 2H, ArH), 7.21 (s, 1H, =CHAr), (m, 3H, ArH), (m, 4H, ArH); 13 C MR (CDCl 3, 100 MHz): δ40.1, 111.9, 121.9, 126.5, 127.9, 128.5, 128.9, 132.4, 133.5, 135.0, 152.4, 160.7, 168.6; ESI-MS+ m/z Calcd. for C 18 H [M+H], found S3

4 (4Z)-4-(4-,-Diphenylaminobenzylidene)-2-phenyl-5(4H)-oxazolone (IIIb). Red powder; Yield 69%; m.p C; IR (KBr) ν max /cm -1 : 1706, 1635, 1584, 1491, 1426, 1285, H MR (CDCl 3, 400 MHz): δ7.05 (d, J = 9.7 Hz, 2H, ArH), (m, 7H, =CHAr+ArH), (m, 4H, ArH), (m, 2H, ArH), (m, 1H, ArH), 8.07 (d, 2H, J = 8.7 Hz, ArH), 8.13 (d, 2H, J = 8.8 Hz, ArH); 13 C MR (CDCl 3, 100 MHz): δ120.5, 124.9, 126.1, 126.2, 126.4, 128.2, 128.9, 129.7, 130.6, 132.0, 132.9, 134.1, 146.5, 150.8, 162.0, 168.2; ESI-MS+ m/z Calcd. for C 28 H [M+H], found General procedure for preparation of (4Z)-4-arylmethylene-1-methyl-2-phenyl-1,4- dihydro-5h-imidazolin-5-one (1-2, Scheme 1). 3,5-7 A mixture of oxazolone (0.34 mmol), methylamine in 40% aqueous solution (0.04 ml, 1.16 mmol) and anhydrous zinc chloride (0.018 g, 0.14 mmol, 40 mol%) was heated at 170 C for 2h. The reaction mixture was cooled to room temperature and quenched with water. The organic matter was extracted with ethyl acetate (20 ml 3) and washed with saturated sodium bicarbonate solution. The extract was dried over anhydrous sodium sulphate and concentrated to get brown colored crude product. It was further purified by silica gel ( mesh) column chromatography. S4

5 Results: (4Z)-4-(4-,-Dimethylaminobenzylidene)-1-methyl-2-phenyl-1,4-dihydro-5H-imidazolin-5- one (DMPI). range product. Yield 69%; m.p C; IR (KBr) ν max /cm -1 : 1695, 1634, 1587, 1523, 1433, 1367, 1197; 1 H MR (CDCl 3, 400 MHz): δ3.06 (s, 6H, 2 ), 3.36 (s, 3H, ), 6.71 (d, J = 9.2 Hz, 2H, ArH), (m, =CHAr+CHCl 3 ), 7.53 (m, 3H, ArH), 7.84 (m, 2H, ArH), 8.17 (d, J = 8.8 Hz, 2H, ArH); 13 C MR (CDCl 3, 125 MHz) δ29.1, 40.3, 112.0, 128.7, 128.8, 129.5, 129.8, 129.9, 130.6, 131.0, 134.8, 151.6, 159.2, 171.6; ESI-MS+ m/z Calcd. for C 19 H [M+H], found (4Z)-4-(4-,-Diphenylaminobenzylidene)-1-methyl-2-phenyl-1,4-dihydro-5H-imidazolin-5- one (DPMPI). Red product. Yield 60%; m.p C; IR (KBr) ν maz /cm -1 : 1708, 1634, 1584, 1491, 1447, 1382, 1286; 1 H MR (CDCl 3, 400 MHz): δ 3.35 (s, 3H, ), 7.00 (d, J = 8.8 Hz, 2H, ArH), (m, 6H, ArH), 7.19 (s, 1H, =CHAr), (m, 4H, ArH), (m, 3H), (m, 2H, ArH), 8.08 (d, J = 8.5 Hz, 2H, ArH); 13 C(CDCl 3, 125 MHz): δ29.2, 121.1, 124.4, 125.8, 127.5, 128.7, 128.9, 129.1, 129.6, 129.7, 131.3, 134.0, 137.1, 146.8, 150.0, 160.7, ESI-MS+ m/z Calcd for C 29 H 24 3 : [M+H], found S5

6 References 1. Perrin, D. D.; Armarego, W.L.F. Purification of Laboratory Chemicals, 4 th ed.; Butterworth- Heinemann, Lai, G.; Bu, X. R.; Santos, J.; Mintz, E. A. Synlett 1997, Badr, M. Z.; El-Sherief, H. A. H.; Tadros, M. E. Bull. Chem. Soc. Jpn. 1982, 55, Hoshina, H.; Tsuru, H.; Kubo, K.; Igarashi, T.; Sakurai, T. Heterocycles 2000, 53, Rajbongshi, B. K.; Ramanathan, G. J. Chem. Sci. 2009, 121, Bhattacharjya, G.; Agasti, S. S.; Ramanathan, G. ARKIVC 2006, 10, Mukerjee, A. K.; Kumar, P. Heterocycles 1981, 16, 1995 Spectral reproduction of oxazolones (IIIa-b) and imidazolin-5-ones (1-2) S6

7 2 Figure S1. 1 H MR (400 MHz, CDCl 3 ) and 13 C MR (100 MHz, CDCl 3 ) of oxazolone IIIa S7

8 Figure S2. 1 H MR (400 MHz, CDCl 3 ) and 13 C MR (100 MHz, CDCl 3 ) of oxazolone, IIIb S8

9 2 2 V ArH ArH+CHCl 3 ArH 2 Figure S3. 1 H MR (CDCl 3, 400 MHz) and 13 C MR (CDCl 3, 125 MHz) of (4Z)-4-(4-,-dimethylaminobenzylidene)-1-methyl-2-phenyl-1,4-dihydro-5H-imidazolin-5-one (1, DMPI). S9

10 CH 3 CH 3 =CHAr X Figure S4. 1 H MR (CDCl 3, 400 MHz) and 13 C MR (CDCl 3, 125 MHz) of (4Z)-4-(4-,diphenylaminobenzylidene)-1-methyl-2-phenyl-1,4-dihydro-5H-imidazolin-5-one (DPMPI) S10

11 Figure S5a: Logarithmic plots of the femtosecond fluorescence transients of DMPI and DPMPI in different glycerol-methanol mixtures. Figure S5b: Logarithmic plots of the femtosecond fluorescence transients of DMPI and DPMPI in solvents of different polarity, but with almost similar viscosities. S11

12 Figure S6. Logrithmic plots of (a) DMPI and (b) DPMPI depicting the variation of two time constants, τ 1 and τ 2 with the microviscosity of the glycerol-methanol mixtures. S12

13 Figure S7. Calculated potential energy surfaces of ground state (S 0 ) and first excited singlet state (S 1 ) of DMPI (a) as a function of dihedral angle γ(c4-c7-c8-c13) or rotation about the single bond (C7-C8), keeping β fixed at 0 and (b) as a function of dihedral angle β(3-c4-c7-c8) or rotation about the double bond (C4-C7), keeping γ fixed at 98. While internal conversion (IC) is very difficult in (a) because of large S 0 -S 1 energy gap, IC is difficult in (b) because of high activation barrier of twisting (30 kcal/mol). S13

14 Figure S8. Potential energy profiles of the S0 and S1 states as a function of β (rotation about C4- C7 double bond), keeping γ fixed at -2, computed using TDDFT with and without PCM (acetonitrile) S14

15 Spectral reproduction before irradiation of DMPI 2 Z Figure S9. 1 H MR (400 MHz, CDCl 3 ) of (4Z)-4-(4-,-dimethylaminobenzylidene)-1-methyl-2-phenyl- 1,4-dihydro-5H-imidazolin-5-one (1, DMPI). 13 C MR is shown in Figure S3 S15

16 Spectral reproduction after irradiation of DMPI ( 1 H MR) 2 2 Z + E Figure S10. 1 H MR (400 MHz, CDCl 3 ) of (4Z)-4-(4-,-dimethylaminobenzylidene)-1-methyl-2- phenyl-1,4-dihydro-5h-imidazolin-5-one (1, DMPI) and (4E)-4-(4-,dimethylaminobenzylidene)-1-methyl-2-phenyl-1,4-dihydro-5H-imidazolin-5-one (E-DMPI) formed after irradiation of Z-DMPI. S16

17 Spectral reproduction after irradiation of DMPI ( 13 C MR) 2 2 Z + E Figure S C MR (125 MHz, CDCl 3 ) of (4Z)-4-(4-,-dimethylaminobenzylidene)-1- methyl-2-phenyl-1,4-dihydro-5h-imidazolin-5-one (1, DMPI) and (4E)-4-(4-,dimethylaminobenzylidene)-1-methyl-2-phenyl-1,4-dihydro-5H-imidazolin-5-one (E-DMPI) formed after irradiation of Z-DMPI. S17