College of Chemistry and Chemical Engineering, Shenzhen University, Shenzheng, Guangdong, P. R. China. 2

Transcription

1 Electronic Supplementary Material (ESI) for Physical Chemistry Chemical Physics. This journal is the Owner Societies 5 Supplementary Information Remarkable Effects of Solvent and Substitution on Photo-dynamics of osine: A Femtosecond Broadband Time-resolved Fluorescence and Transient Absorption Study Chensheng Ma,* Chopen Chan-Wut Cheng, Chris Tsz-Leung Chan, Ruth Chau-Ting Chan and Wai-Ming Kwok* College of Chemistry and Chemical Engineering, Shenzhen University, Shenzheng, Guangdong, P. R. China. Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong, P. R. China. macs@szu.edu.cn; wm.kwok@polyu.edu.hk Experimental details-materials and femtosecond broadband time-resolved fluorescence (fs-trf and fs-trfa) and transient absorption (fs-ta) measurement and spectral correction. Kinetic analysis Figure S Steady-state absorption and fluorescence spectra of,,, CMP, dcmp, m5 and m5 in ph7 buffered water..4 Figure S Fs-TRF spectra and fluorescence decay profiles of, dcmp and m5 in ph7 buffered water Figure S Fs-TRF spectra and fluorescence decay profiles of,,, m5 and m5 in methanol....6 Figure S4 Fs-TRF anisotropy spectra of,,, CMP, dcmp, m5 and m5 in ph7 buffered water and of,,, m5 and m5 in methanol Table S Spectral and dynamic parameters obtained from fs-trf and fs-trfa measurements for cytosine and its N- and C5-substituted derivatives with 67 nm excitation. 8 Figure S5 Fs-TA spectra of,, CMP, and m5 and, dcmp and m5 in ph7 buffered water Figure S6 Fs-TA spectra of,, and m5 in methanol. Figure S7 Fs-TA time profiles of CMP,, dcmp and m5 in ph7 buffered water... Figure S8 Comparison of fs-ta spectra recorded at ~4 ps after 67 nm excitation of, and in methanol.. Figure S9 Fs-TA spectra of,, and CMP in ph7 buffered water obtained at ~85 ps after 67 nm excitation Table S Dynamic parameters obtained from fs-ta measurements for and its N- and C5- substituted derivatives with 67 nm excitation References

2 Experimental details: osine nucleobase (), nucleosides of including cytidine () and - deoxycytidine (), and nucleotides of including cytidine 5 -monophosphate (CMP) and -deoxycytidine 5 -monophosphate (dcmp) were purchased from Sigma Chemical Company. C5-derivatives of including 5-methylcytidine (m5) and 5-methyl- - deoxycytidine (m5) were purchased from TCI. They were used without further purification. 5 mm ph7 potassium aqueous buffer and spectroscopic grade methanol (CH OH) were used to prepare sample solution. To prepare ph7 buffered water (H O), appropriate amounts of potassium dihydrogen phosphate (KH PO 4 ) and dipotassium hydrogen phosphate (K HPO 4 ) were dissolved in 8. MΩ double deionized (DDI) water produced by a MILLIPORE (Milli-Q Synthesis) system. In the steady state measurements, UV-vis absorption and steady state fluorescence spectra was respectively recorded by using a Hitachi U-9H spectrometer and a Jobin Yvon Fluoromax-4 spectrofluorometer. Time-resolved experimental setups for the broadband fs time-resolved fluorescence (fs- TRF), fs-trf anisotropy (fs-trfa), and fs-transient absorption (fs-ta) measurements have been described in detail elsewhere. [-5] Briefly, the measurement were done based on a commercial ultrafast Ti:Sapphire regenerative amplifier laser system and home-built fs-trf and fs-ta spectrometers. The sample solutions (with concentration of ~-4 mm) were excited by a femtosecond pump laser pulse with wavelength at 67 nm, which was generated by an optical parametric amplifier pumped by part of the 8 nm fundamental ( khz repetition rate, ~5 fs duration) from the regenerative amplifier of Ti:Sapphire laser system. The subsequent excited-state processes were probed by a second pulse to monitor the temporal evolution of the broadband transient fluorescence and the transient absorption spectrum in the measurement of fs-trf and fs-ta, respectively. In the measurements of fs-trf and fs-trfa, the Kerr-gate technique was employed. [-6] With this method, a Kerr-gate device consists of a mm thickness of quartz plate (Kerr medium) equipped between a crossed polarizer pair was driven by an 8 nm gating pulse to function as an ultrafast shutter to sample the transient fluorescence signal at varied selected pump/probe delays. For the measurement of total TRF spectrum, in order to eliminate the effect of rotational diffusion, the polarization direction of the pump laser was set at the magic angle in relative to that of the first polarizer in the Kerr-gate devise. To acquire the spectra of fs-trfa (r(t)), the TRF measurements at a certain time delay were done by setting the polarization direction of the pump laser to be either parallel or perpendicular to that of the first polarizer in the Kerr-gate device to allow measurement of spectrum I para (t) and I perp (t), respectively. The r(t) was then derived according to Equation. [4-6] r(t) = (I para (t) - I perp (t)) / (I para (t) + I perp (t)).. Equation The fs-trfa at around time zero (r(), Figure, Figure S-S, Table S) were obtained based on the above equation using I para (t) and I perp (t) spectra recorded at time interval of ~ fs after the excitation. [4,5] The measurements of I para (t) and I perp (t) and therefore the r(t) derived at all the selected time intervals (Figure, Figure S-S4, Table S) were not affected by the solvents and the cell windows for the experiments were done using spectrophotometric grade solvents and high quality CaF windows that showed negligible fluorescence signal across the spectral range monitored and the temporal regime of the measurements. In the fs-ta measurements, the sample was probed by a white-light-continuum (WLC) pulse created by a CaF plate pumped by an 8 or 4 nm laser pulse to allow spectra to be

3 recorded over wavelength range of 4-7 nm or 4-4 nm, respectively. The presented fs-ta spectra which cover wavelengths from 4-7 nm were obtained by combining the 8 nm and the corresponding 4 nm pump spectra recorded at selected delay times after the photo-excitation. The instrument response function (IRF) for the measurements is wavelength-dependent, better at longer wavelength. The IRF varies from ~5 to ~ fs for the measurements of fs- TRF and fs-trfa which cover wavelengths from ~ nm to 7 nm. In the measurement of fs-ta, the IRF varies from ~ to 5 fs as wavelength changes from 7 nm to 4 nm. For both the fs-trf(a) and fs-ta, the temporal delay of pump to probe pulse was varied using a computer controlled optical delay line. In each of the measurements, sample solution (with concentration of ~-4 mm) of ~ ml was flowed in a cell with.5 mm path length to avoid photo-degradation. The transient signals produced by the photo-excitation were collected by a monochromator and detected with a liquid nitrogen cooled CCD detector before readout by computer for further analyses. In order to avoid saturation effect and unwanted multi-photon, the energy of the pump laser beam was kept low with a typical laser pulse peak power of ~ GW/cm. All fs time-resolved spectra were obtained from subtraction of the appropriately scaled probe-before-pump time delay signal from the pump-probe time delay signal, and were corrected for the detection system transmission/sensitivity variation with wavelength and the wavelength-dependent time shift due to the group velocity dispersion (GVD). The wavelength sensitivity variation correction curve was obtained by comparing the ps TRF spectrum of trans-stilbene (this covers the spectral range of interest in the present study and shows very little change on the shape of the TRF spectra at difference time delays) with its sensitivity corrected steady-state spectrum from a commercial fluorescence spectrometer. The GVD of the system was corrected by equation δt = Aλ Bλ + C, where δt is time shift (fs), λ is wavelength (nm), and A, B, and C are scaling factors determined by the optics arrangement and solvent used in the measurement. [] The scaling factors were estimated by peak fitting of the TRF spectra of white light continuum created by intense pump pulse and the values of A, B, and C were estimated to be., 4.5, and 54 in the current measurement. The samples were monitored by UV-vis absorption and revealed no degradation after the fs time-resolved experiments. Kinetic analysis: For the analysis of the kinetic decay profiles of the fs-trf and fs-ta intensities, the experimental time profiles (F(t)) were fitted by convolution of the instrument response function (g(t)) with a multiple exponential function (f(t)) as showed in equations -: [-4] F ( t) g( t') f ( t t') dt' Equation with f ( t) a i exp( t / i ) Equation n i Where i is time constant and a i the relative amplitude associated to i. t n i a i Equation 4

4 Bi-exponential function (n = ) was used for f(t) in the fitting of the decay profiles of fs-trf. For the analysis of the time profiles in fs-ta, tri-exponential (n = ) and biexponential (n = ) function with a minute long-lived offset represented by an additional component with fixed time constant of ns was used, respectively, for the case of and its N derivatives and the case of the C5 derivatives. Extinction Coefficient (x M - cm - ) Wavenumber (cm - ) CMP dcmp m5 m Normalized Fluorescence Intensity Figure S. Steady state absorption (left) and normalized fluorescence spectra (right) of, its nucleosides ( and ) and nucleotides (CMP and dcmp) and its C5-substituted derivatives (m5 and m5) in ph7 buffered H O. The fluorescence spectra were recorded with excitation at 67 nm wavelength. Spectrum from reference 7 4

5 Relative Intensity (a.u.). ps..... ps ps. 4 ps 4 5.ps ps 4 5. Anisotropy, r Anisotropy, r Anisotropy, r.ps ps.. 4 Normalized Intensity (a.u.) dcmp 4 m5 (d) nm 7 nm 45 nm (e) nm 7 nm 45 nm (f) nm 7 nm 45 nm Time Delay (ps) Figure S. (a-c) Fs-TRF spectra and (d-f) fluorescence decay profiles at selected wavelengths obtained for (a, c), (b, d) dcmp and (c, f) m5 in ph7 buffered H O. The spectra were recorded at time intervals of -.5- ps (.5,.5,.,.5,.,.4,.5,.7,,.4,,, 5 and ps) and.- ps (.,.5,.5,.85,.5,.75,.5,.5, 5, 7,, 5, 5 and ps) after 67 nm photo-excitation. The insets show around teim zero TRF anisotropy spectra and intensity normalized TRF spectra at (a, b).5,.5 and ps and., and 5 ps after the photo-excitation. The arrows indicate directions of spectral evolutions. Raman line of water. 5

6 Relative Intensity (a.u.) Relative Intensity (a.u.). ps. ps ps.. ps.. ps 4 ps 4 5.ps ps.ps ps ps ps.. 4 (g)..ps ps.. 4 (h) Anisotropy, r Anisotropy, r Anisotropy, r Anisotropy, r Anisotropy, r Normalized Intensity (a.u.) Normalized Intensity (a.u.) 4 Time Delay (ps) m5 m5 (d) nm 7 nm 45 nm (e) nm 7 nm 45 nm (f) nm 7 nm 45 nm (i) nm 7 nm 45 nm (j) nm 7 nm 5 nm Time Delay (ps) Figure S. (a-c) and (g-h) Fs-TRF spectra and (d-f) and (i-j) fluorescence decay profiles at selected wavelengths obtained for (a, d), (b, e), (c, f), (g, i) m5 and (h, j) m5 in methanol. The spectra were recorded at time intervals of (a-c).5- ps (.5,.5,.,.5,.,.4,.5,.7,,.4,,, 5 and ps) and (g-h).- ps (.,.,.4,.6,.85,.5,.75,.5,.5, 5, 8.5, 5, 5 and ps) after 67 nm photo-excitation. The insets show around time zero TRF anisotropy spectra and intensity normalized TRF spectra at (a-c).5,.5 and ps and (g-h)., and 5 ps after the photo-excitation. The arrows indicate directions of spectral evolutions. 6

7 Anisotropy, r... ps. ps H O ps. ps CH OH (d)... Anisotropy, r... ps. ps H O ps. ps C Anisotropy, r... ps. ps H O ps. ps CH OH (e)... Anisotropy, r r... ps. ps H O ps. ps C Anisotropy, r Anisotropy, r Anisotropy, r Anisotropy, r ps. ps ps. ps m5 H O ps. ps ps ps. ps ps H O CMP H O m5 H O (g) (i) (j) m5 CH OH Figure S4. Fs-TRF anisotropy (fs-trfa) spectra recorded at the denoted time intervals after 67 nm excitation of and its N and C5 derivatives in water and methanol. ps. ps ps. ps (f) ps. ps ps ps. ps ps CH OH dcmp H O m5 CH OH (h) (k) (l) Anisotropy, r r Anisotropy, Anisotropy, r r Anisotropy, Anisotropy, r r Anisotropy, Anisotropy, r r ps. ps ps. ps ps. ps ps ps. ps ps H O CMP H O m5 H O (g) m5 H O (i) (j) ps. ps 5 Wave ps. ps 5 Wave ps. ps ps ps. ps ps C C m C 5 Wave 7

8 Table S. Spectral and dynamic parameters obtained from fs-trf and fs-trfa measurements for cytosine and its N- and C5-substituted derivatives with 67 nm excitation Solvent a Probe/nm b τ /ps (a ) b τ /ps (a ) c r() (.89±.) (.±.) H O (ph 7) 7.7±. (.85±.).46±. (.5±.).7±. 45 (.9±.) (.±.) (.9±.) (.±.) CH OH 7.6±. (.8±.).5±. (.7±.).5±. 45 (.86±.) (.4±.) (.88±.) (.±.) H O (ph 7) 7.4±. (.79±.).79±. (.±.).±. 45 (.84±.) (.6±.) (.86±.) (.4±.) CH OH 7.5±. (.77±.).9±. (.±.).±. 45 (.8±.) (.9±.) (.88±.) (.±.) H O (ph 7) 7.±. (.8±.).±. (.7±.).±. 45 (.87±.) (.±.) (.88±.) (.±.) CH OH 7.±. (.8±.).84±. (.9±.).±. 45 (.8±.) (.8±.) (.8±.) (.8±.) CMP H O (ph 7) 7.7±. (.75±.).84±. (.5±.).±. 45 (.8±.) (.7±.) (.85±.) (.5±.) dcmp H O (ph 7) 7.4±. (.78±.).9±. (.±.).4±. 45 (.85±.) (.5±.) (.69±.) (.±.) m5 H O (ph 7) 7.7±.5 (.±.) 7.6±. (.67±.).4±. 45 (.9±.) (.6±.) (.6±.) (.8±.) m5 CH OH 7.78±.5 (.8±.) 5.±. (.6±.).±. 45 (.4±.) (.57±.) (.6±.) (.8±.) m5 H O (ph 7) 7.56±.5 (.7±.) 5.4±. (.6±.).5±. 45 (.4±.) (.59±.) (.58±.) (.4±.) m5 CH OH 7.6±.5 (.5±.) 4.4±. (.65±.).±. 45 (.6±.) (.6±.) a Wavelength for fluorescence examined in the kinetic analysis. b Time constant (τ i, i =, ) and corresponding pre-exponential factor (a i, i =, ) obtained from kinetic analysis of the TRF decay. c Values of fluorescence anisotropy at around time zero after photo-excitation. 8

9 OD ( - ) CMP. 4 5 m (e) (g) ps 4 5 ps ps CMP 4 5 (d) (f) (h) OD ( - ) - Figure S5.Temporal evolutions of fs-ta spectra recoded at early (left) and late (right) time intervals after 67 nm excitation of (a, b), (c, d), (c, f) CMP and (g, h) m5 in ph7 buffered water. The arrows indicate directions of spectral evolutions. The inset in compares the spectra at ~4 ps after the excitation for, and CMP in water. Due to the pulse of excitation laser. 9

10 OD ( - ) dcmp m5 (e) ps 4 5 ps 4 5 (d) (f) OD ( - ) ps Figure S5. Fs-TA spectra recorded with 67 nm excitation of (a, b), (c, d) dcmp and (e, f) m5 in ph7 buffered H O. The spectra were recorded at time intervals of.5-4 ps (.5,.,.5,.,.5,.4,.5,.7,,.5 and 4 ps) and 4- ps (4, 7, 8.5,,, 4, 6 and ps);.5-4 ps (.5,.,.5,.,.5,.4,.7,,.5 and 4 ps) and (d) 4- ps (4, 5, 7,,,, 6 and ps); (e) ps (.5,.,.5,.,.5,.4,.5,.6,.7 and.85 ps) and (f).85- ps (.85,.5,.75,.5,, 4, 6, 8.5,, 5, and ps) after the photo-excitation. Due to the laser for photo-excitation. The arrows indicate directions of the spectral evolutions.

11 ..6ps.6ps (d) OD ( - )..6ps OD ( - ).6ps (e) 7ps (f)..6ps OD ( - ) ps m5. ps (g) 7ps 4 5 ps ps 4 5 (h) 4 - OD ( - ) Figure S6. Fs-TA spectra recorded with 67 nm excitation of (a, b), (c, d), (e, f) and (g, h) m5 in CH OH. The spectra were recorded at time intervals of.5-.6 ps (.5,.,.5,.,.5,.4,.5 and.6 ps) and.6-5 ps (.6,.85,.5,,, 4, 6, 5, 5,, 6 and 5 ps);.5-.6 ps (.5,.,.5,.,.5,.4,.5 and.6 ps) and (d).6-7 ps (.6,.85,.5,.75,.5,.5, 5, 8.5, 5, 5, 5 and 7 ps); (e).5-.6 ps (.5,.,.5,.,.5,.4,.5 and.6 ps) and (f).6-7 ps (.6,.5,.75,.5,.5, 6,, 6, 5, 5, 5 and 7 ps); (g).5- ps (.5,.,.5,.,.5,.4,.5,.6,.85 and ps) and (f) - ps (,.75,, 5, 7,, 5,, 5 and ps) after the photoexcitation. The arrows indicate directions of the spectral evolutions.

12 Normalized OD Normalized OD Normalized OD Normalized OD - - CMP 77 nm 46 nm 57 nm dcmp m Time Delay (ps) 77 nm 46 nm 57 nm 46 nm 57 nm (d) 45 nm 57 nm Figure S7. Fs-TA time profiles obtained for CMP,, dcmp, and (d) m5 with 67 nm excitation in H O. OD (a.u.) 4 5 Figure S8. Comparison of fs-ta spectra recorded at ~4 ps after 67 nm excitation of, and in CH OH. The spectra were intensity normalized at ~4 nm.

13 Normalized OD CMP Figure S9. Fs-TA spectra of,,, and CMP in ph7 buffered H O obtained at ~85 ps after excitation at 67 nm. Table S. Dynamic parameters obtained from fs-ta measurements for and its N- and C5-derivaitves with excitation at 67 nm wavelength Molecule Solvent a Probe/nm 58 b τ /ps (a ) b τ /ps (a ).9±. (-.75±.) b τ /ps (a ) (-.5±.4) b,c τ 4 /ps (a 4 ) H O 4.7±. (.58±.) (.±.) 7.74±.6 (.±.6) (.±.8).46±. 57 (.7±.) (.9±.) CH OH 4.6±. (.67±.).5±. (.±.) 5.85± (.8±.5) (.±.5) 77.±. (-.49±.4) (-.49±.4) (-.±.7) H O 46.4±. (.5±.4) (.±.4) 5.± (.5±.4) (.±.6).79±. 57 (.76±.) (.4±.) CH OH 46.5±. (.6±.5).9±. (.±.) 44.±6 (.±.) (.5±.6) 77.7±. (-.66±.) (-.±.5) (-.±.5) 9.67± H O 46.±. (.58±.4) (.7±.4) (.4±.) (.±.7).±. 57 (.8±.) (.9±.5) CH OH 46.±. (.67±.).84±. (.±.5) 86.±6 (.9±.4) (.±.7) 77.4±. (-.6±.) (-.9±.5) (-.±.6) CMP H O 46.7±. (.5±.5) (.4±.).5± (.±.4) (.±.4).84±. 57 (.76±.) (.4±.) 4 (.5±.4) (.4±.) (.±.5) (.5±.7) dcmp H O.4±..9±..± 57 (.8±.) (.±.) m5 79 (-.99±.) (-.±.4) H O 45.7±.5 (.55±.) 7.6±. (.4±.4) (.5±.6) 57 (.5±.) (.65±.) CH OH 57.78±.5 (.6±.) 5.±. (.69±.) (.5±.5) 45 (.5±.4) (.46±.) (.±.6) m5 H O.56±.5 5.4±. 57 (.44±.) (.56±.) a Wavelength for the fs-ta time profile examined in the kinetic analysis; b Time constants ( i, i = 4) and corresponding pre-exponential factors (a i, i = 4) derived from the kinetic analysis of the TA time profiles; c Time-independent offsets.

14 References () C. Ma, W.-M. Kwok, W. S. Chan, P. Zuo, J. T. W. Kan, P. H. Toy, D. L. Phillips, J. Am. Chem. Soc. 5, 7, C. Ma, W.-M. Kwok, W. S. Chan, Y. Du, J. T. W. Kan, P. H. Toy, D. L. Phillips, J. Am. Chem. Soc. 6, 8, () W.-M. Kwok, C. Ma, D. L. Phillips, J. Am. Chem. Soc. 6, 8, W.-M. Kwok, C. Ma, D. L. Phillips, J. Am. Chem. Soc. 8,, () W.-M. Kwok, C. Ma, D. L. Phillips, J. Phys. Chem. B 9,, (4) C. T. L. Chan, C. C. W. Cheng, K. Y. F. Ho, W.-M. Kwok, Phys. Chem. Chem. Phys,,, (5) C. C. W. Cheng, C. Ma, C. T. L. Chan, K. Y. F. Ho, W.-M. Kwok, Photochem. Photobiol. Sci.,, (6) D. Onidas, D. Markovitsi, S. Marguet, A. Sharonov, T. Gustavsson, J. Phys. Chem. B, 6, (7) L. Blancafort, B. Cohen, P. M. Hare, B. Kohler, M. A. Robb, J. Phys. Chem. A 5, 9,