Isatin phenylhydrazones: Anion enhanced photochromic behaviour


 Hester Johnston
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1 Electronic Supplementary Material (ESI) for Photochemical & Photobiological Sciences. This journal is The Royal Society of Chemistry and Owner Societies 2015 Electronic Supplementary Information (ESI) Isatin phenylhydrazones: Anion enhanced photochromic behaviour Marek Cigáň a, *, Klaudia Jakusová a, Martin Gáplovský b, Juraj Filo a, Jana Donovalová a, Anton Gáplovský a a Faculty of Natural Sciences, Institute of Chemistry, Comenius University, Mlynská dolina CH2, SK Bratislava, Slovakia; s: (M.C.); (K.J.); (J.D.); (M.H.); (R.S.); (A.G.) b Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Comenius University, Odbojárov 10, SK Bratislava, Slovakia; (M.G.) * 1
2 EXPERIMENTAL SECTION Supporting information Synthesis General Scheme: Synthesis of 1 and 2 Zisomers in EtOH. (E)isatin N 2 phenylhydrazones 1 and 2: (Z)3(phenylhydrazono)indolin2one Z1: Obtained from phenylhydrazine (0.76g) in 78% yield (1.24g), 1 H NMR (300 MHz, DMSOd 6 ), δ: (s, 1H), (s, 1H), 7.56 (d, J = 7.5 Hz, 1H), (m, 4H), 7.25 (td, J = 7.7, 1.2 Hz, 1H), 7.05 (m, 2H), 6.93 (d, J = 7.8 Hz, 1H). 13 C NMR (75 MHz, CDCl 3 ) δ (s), (s), (s), (s), (s), (s), (s), (s), (s), (s), (s), (s). Anal. Calcd. for C 14 H 11 N 3 O (237.26) C, 70.87; H, 4.867; N, Found C, 71.71; H, 4.71; N, (Z)3(phenylhydrazono)1methylindolin2one Z2: Obtained from phenylhydrazine (0.69g) in 83% yield (1.30g), 1 H NMR (300 MHz, (CD 3 ) 2 CO), δ: (s, 1H), 7.63 (dd, J = 7.5, 0.5 Hz, 1H), (m, 5H), 7.13 (ddd, J = 7.6, 0.9 Hz, 1H), (m, 2H), 3.32 (s, 3H). 13 C NMR (75 MHz, DMSO), δ: (s), (s), (s), (s), (s), (s), (s), (s), (s), (s), (s), (s), (s). Anal. Calcd. for C 15 H 13 N 3 O (251.28) C, 71.70; H, 5.21; N, Found C, 71.82; H, 5.18; N,
3 Titration experiments Apparent association constant K ass determinations Equation (1) was rewritten to the following form for nonlinear fit: A = A0 + c1 *(P1 A0 ) * ( c0 + x +1/P2  ( c0 + x +1/P2)^24 * c0 * x ), (2) where: c 0 = , c 1 = 1/2c 0 = , parameter P1 = A lim, parameter P2 = K ass and x = c A. The A 0 value was fixed to the absorbance value A for x = 0. The large difference in constants c 0, c 1 and the x data range led rescaling the nonlinear function (x and fitted parameter 1/P2 by a factor of 10 4 ). Following this modification, the standard nonlinear leastsquares NelderMead minimization method was employed to determine fitting parameters P1 and P2. 60,61 Three different wavelengths were used to K ass determination of Z1 and Z2 (470 nm, 475 nm and 480 nm). 3
4 Light initiated EZ and ZE isomerization Quantum yield determination The ZE isomerization quantum yield ( EZ ) of isatin phenylhydrazone Zisomers Z1 and Z2 in DMF solution was determined by equations (6) and (7) at low ZE conversion (to eliminate the effect of back EZ photoisomerization): 62 φ Z E = c t c 0 dc t I a dt 0 = Δc t I a dt 0 c = A λ ε (6); Z λ (7) where: c is the concentration change in Zisomer, I a is Zisomer absorbed photon flux at the irradiation wavelength using a monochromatic light source, A is the absorbance change at irradiation wavelength using a monochromatic light source, Z is Zisomer molar extinction coefficient at irradiation wavelength using a monochromatic light source and t is irradiation time. Because only Z isomers were isolated from the reaction mixture, the Zisomer extinction coefficient at 405 nm was determined by Eq. (8): ε Z 405 = A 405 c Z. (8) The Zisomer absorbed photon flux I a during ZE isomerization at irradiation wavelength = 405 nm and incident Zisomer concentration c 0 was calculated by Eq. (9): 62 I a,z 405 = I 0[ 1 10 [ε Z 405 (c 0 Δc)] ]. (9) The incident photon flux I 0 was determined by 2nitrobenzaldehyde (2NB) as chemical actinometer, according to Eq. (10): 63 k I 0 = 2.303ε o NB 405 φ o NB 405 l, (10) where: onb405 is the molar extinction coefficient of 2NB at irradiation wavelength 405 nm, onb405 is the quantum yield of 2NB photodegradation at irradiation wavelength, l is the path length and k is the 2 NB firstorder photodegradation slope plotted under lowlightabsorbing conditions: 63 4
5 (11) ln( [o NB] ) t = kt [o NB] 0. Quantum yield of the Aform transformation (Ф A ) induced by light (465 nm LED sources) was determined by Eqs. (12)(14): (13) φ A = c t c 0 dc A t I a dt 0 = Δc A t I a dt 0 (12); c A = A λ ε A λ where: c is the concentration change in Aform (Eisomer of azo Aform), I a is Aform absorbed photon flux at the irradiation wavelength using a monochromatic light source, A is the absorbance change at irradiation wavelength using a monochromatic light source, Z is Aform molar extinction coefficient at irradiation wavelength using a monochromatic light source and t is irradiation time. Because the amount of transformed Zisomer to Aform after the strongly basic anion addition is known, the Aform concentration change was determined by Eq. (13) at low A to Bform conversion (to eliminate the effect of back BA thermal transformation that is approximately 10times slower compared to AB photochemical transformation). The Aform extinction coefficient at 465 nm was calculated as: A465 = A 465 /c A465 ; where: c A = c Z(without F  )  c, c = A 375 / Z375 and Z375 = A 375 /c Z(without F  ). The Aform absorbed photon flux I a at irradiation wavelength = 465 nm and incident Aform concentration c A0 was calculated by Eq. (14): I a,a 465 = I 0[ 1 10 [ε A 465 (c A0 Δc)] ]. (14) The incident photon flux I 0 at 465 nm was determined by ferrioxalate (FE) actinometry, according to Eq. (15): 64 ( da FE 390 ) 1 I a, FE 465 dt φ FE 465. ε FE 390. l I 0 = = 1 10 A FE A FE 465 (15), where: a, FE465 is ferrioxalate actinometer absorbed photon flux, A FE is ferrioxalate absorbance at corresponding wavelength using a monochromatic light source, FE390 is ferrioxalate molar extinction coefficient at 390 nm, FE465 is quantum yield of ferrioxalate photochemical conversion and l is the path 5
6 length. Ferrioxalate absorbance at 465 nm (A FE was measured by Ocean Optics SD2000 spectrophotometer. 6
7 Photochemical A/B conversion Because the Aform extinction coefficients at 465 nm for both phenylhydrazones 1 and 2 are known, the amount of photochemically transformed azo Aform to form B was calculated by Eq. (16): c A A 465 A 465 = ~ = ε B 465 ε A 465 1/4ε A 465 ε A 465 (16) A 465 1/3ε A 465 ε A 465 = A 46 3/4ε where the molar extinction coefficients of corresponding Bforms ( B465 ) were extrapolated from the A / B ratio of longwavelength transitions in calculated UVVis spectra of A and Bforms (M062x 631+g(dp) level). The longwavelength transitions relates to a chargetransfer transition in Aform and nπ* transition in Bform, respectively. Initial concentrations of Aform in solution (c A ) were calculated according to the following equation: c A = c Z (without F ) c, (17) where Δc = ΔA 375 / Z375 and Z375 = A 375 /c  Z(without F ). The photoisomerization extent therefore increases from 2030% conversion to 84% and 77% after F  anion addition to Z1 and Z2 solution, respectively. If ε B 465 = 1/5ε A 465 is assumed, then photoisomerization extents are 79% and 71%. 7
8 SUPPORTING SCHEMES AND FIGURES Fig. S1. 1 H NMR spectrum of Z2 in DMSOd 6 before and after irradiation with light of 405 nm wavelength (T = K). Scheme S1. Assumed structure of Z1 dimer at higher concentrations. 8
9 Fig. S2. Calculated relative Gibbs free energies of E1 and Z1 isomers (keto forms) and their enol E1 enol and Z1enol conformers at the M062x 631+g(dp) level in vacuum (T = K; TS transition state). 9
10 E1 Z1 Scheme S2. Calculated geometries of E1 and Z1 isomer ketoforms at the M062x 631+g(dp) level in vacuum (T = K). Quantumchemical calculations failed to detect direct TS from E1 Eisomer. 10
11 E1enol Z1enol E1enolZ1enolTS Scheme S3. Calculated geometries of E1 and Z1 isomer enolforms (E1enol and Z1enol) and corresponding transition state (TS) for their mutual EZ (ZE) thermal isomerization in vacuum at the at the M062x 631+g(dp) level (T = K). 11
12 Fig. S3. The timedependent absorbance changes of isatin phenylhydrazone Z1 at 450nm and 400 nm ( M) after addition of M TBA + F  in DMF (c Z1 = M; c F  = M; T = K; t 1/2 is the reaction halflife calculated from monoexponential fit of absorbance change at 450 nm). Fig. S4. The Z1anion interaction pseudo firstoder rate constant (k) dependence on the F  anion concentration (c Z1 = M; T = K). 12
13 Fig. S5. Timedependet UVVis spectrum changes of isatin phenylhydrazone Z1 solution after the TBA + OH  addition in DMF (c Z1 = M; c OH  = M; T = K). Fig. S6. Timedependet UVVis spectrum changes of isatin phenylhydrazone Z1 solution after the TBA + CH 3 COO  addition in DMF (c Z1 = M; c CH3COO  = M; T = K). 13
14 Fig. S7. The timedependent absorbance changes of isatin phenylhydrazone Z1 at 450nm and 405 nm ( M) after addition of M TBA + CH 3 COO  in DMF (c Z1 = M; c CH3COO  = M; T = K). Fig. S8. The timedependent absorbance changes of isatin phenylhydrazone Z1 at 450nm and 405 nm ( M) after addition of M TBA + CH 3 COO  in DMF (c Z1 = M; c CH3COO  = M; T = K). 14
15 Fig. S9. 1 H NMR spectrum of Z2 in DMSOd 6 before and after TBA + F  addition (T = K). Fig. S10. Absorbance change of Z1 + TBA + F  solution at 400nm ( ) and 450 nm ( ) in DMF due to 390 s photochemical initialization ( ) and 400 s back thermal relaxation ( ) (c Z1 = M; c F  = M; T = K). Halflife of photochemical transformation (t 1/2 = 43 s) increases due to the Z1 concentration increase (t 1/2 was calculated from monoexponential fit of absorbance change at 450 nm). 15
16 Fig. S11. Reversible cycles of Z2 + TBA + F  solution absorbance at 450 nm in DMF due to photochemical initialization and back thermal relaxation (26 cycles). Fig. S12. Reversible cycles of Z1 + TBA + OH  solution absorbance at 400 and 450 nm in DMF due to photochemical initialization and back thermal relaxation at two different Z1 concentration (Figures A and B). 16
17 Fig. S13. Dependence of the photochemical A to B transformation rate constant k (s 1 ) on the light intensity in DMF (λ irr = 465 nm; c Z1 = M; c F  = M; T = K). Fig. S14. Dependence of the photochemically induced A to B form transformation conversion (absorbance difference at 450 nm in the initial and photostationary state) on the light intensity in DMF (λ irr = 465 nm; c Z1 = M; c F  = M; T = K). 17
18 MeOH addition The addition of MeOH to 1:TBA + F (or 2:TBA + F) solution mixture in DMF results in the Aform destruction (Fig. S15). The absorption band at 450 nm gradually vanishes after MeOH addition and a new hypsochromic band at approximately 385 nm appears. In the next reaction phase, the new band shifts bathochromically to 395 nm (Figs. S15 and S16). Fig. S15. The UVVis spectral changes of 1:TBA + F solution mixture after the addition of different MeOH concentration (solvent: DMF; c Z1 = M; c F  = M; T = K). Fig. S16. Timedependence of the 1:TBA + F solution mixture absorbance at 470 nm at different MeOH concentration (solvent: DMF; c Z1 = M; c F  = M; T = K). 18
19 Based on the observed spectral changes, we assigned the product structure in the initial reaction phase to enol Dform (Scheme S3). Scheme S3. Gradual Aform transformation to initial Zisomers in the presence of MeOH. Because MeOH is stronger acid compared to Aform, the thermodynamically more stable tetrabutylammonium methanolate (CH 3 O  TBA + ) is formed. The absorption band appearance with A at 385 nm in the initial reaction phase is therefore the result of azo Dform formation (Fig. S15). The Dform formation is relatively fast reaction. In the next reaction phase (at high MeOH concentration over M), the relatively slow Dform transformation back to the initial isatine phenylhydrazones Z1 and Z2 occurs and this results in the A bathochromic shift to 395 nm. The final UVVis and 1 H NMR spectra are almost identical with initial UVVis and 1 H NMR spectra spectra of 1 and 2 in MeOH (Figs. S15 and S17). The small A shift results from the increase in solution ionic strength due to the TBA + F  presence. 19
20 Fig. S17. 1 H NMR spectrum of Z1 in DMSOd 6 before and after TBA + F  addition followed by MeOH addition (T = K). 20
21 ADDITIONAL REFERENCES [60] W.H. Press, S. Teukolsky, W. Vetterling, B. Flannery, Numerical Recipes: The Art of Scientific Computing, Cambridge University Press, New York, [61] Wolfram Research, Inc., Mathematica, Version 9.0, Champaign, IL, [62] P. Klán, J. Wirz, Spectrophotometric Determination of the Reaction Progress, in: J. Coxon, P. Bailey, L. Field, J.A. Gladysz, P. Parsons, P. Stang (Eds.), Photochemistry of Organic Compounds: From Concepts To Practice, John Wiley & Sons Ltd, 2009, Chichester, pp [63] E.S. Galbavy, K. Ram, C. Anastasio, 2Nitrobenzaldehyde as a chemical actinometer for solution and ice photochemistry, J. Photochem. Photobiol. A Chem., 2010, 209, , [64] T. Lehóczki, É. Józsa, K. Ösz, Ferrioxalate actinometry with online spectrophotometric detection, J. Photochem. Photobiol. A Chem., 2013, 251, 6368, 21