Electronic Supplementary Material (ESI) for Photochemical & Photobiological Sciences. This journal is The Royal Society of Chemistry and Owner Societies 2014 Photoinduced intramolecular charge transfer in trans-2-[4 -(N,Ndimethylamino)styryl]imidazo[4,5-b]pyridine: Effect of introducing C=C double bond Anasuya Mishra, Saugata Sahu, Shreya Tripathi and G. Krishnamoorthy* Department of Chemistry Indian Institute of Technology Guwahati Guwahati 781039, India Electronic supplementary information (ESI) available: Details of material and methods Absorption spectra in different solvents Lippert-Mataga equation Plot of temperature dependence of fluorescence quantum yield Emission spectra at different ph
Materials and methods t-dmasip-b was synthesized by heating an equimolar mixture of 4-N,Ndimethylaminocinnamic acid and 2,3-diaminopyridine in polyphosphoric acid at 240 C as reported for the synthesis of DMAPIP-b. 1 After 5 hours, the mixture was cooled to room temperature and poured into ice cold water. After neutralization, the compound was extracted by dichloromethane. The compound, purified by column chromatography was further purified by preparative thin layer chromatography. 1 H NMR (600 MHz, CD 3 OD, ppm) 8.32 (broad s, 1H); 7.84 (d, J = 8 Hz, 1H); 7.61 (d, J = 16.2 Hz, 1H); 7.44 (d, J = 8.8 Hz, 2H); 7.18 (dd, J 1 = 5.2 Hz, J 2 = 8 Hz, 1H); 6.86 (d, J = 16.2 Hz, 2H); 6.68 (d, J = 8.8 Hz, 1H), 2.94 (s, 6H). 13 C NMR (150 MHz, CD 3 OD) δ ppm = 39.84, 110.58, 112.68, 114.18, 118.77, 123.70, 124.08, 129.45, 139.26, 139.61, 143.80, 152.48, 155.59. HRMS (M + H + ): 265.1479. Except ethanol (ACS grade), dioxane, 1-propanol and glycerol (all AR grade), all other solvents were HPLC grade. All solvents were shown to be free of spurious fluorescence in the region of the fluorescence measurements and were used as received. Spectral measurements were performed at the solute concentration of ~ 5 x 10-6 M. Absorption and fluorescence spectra were recorded with the help of Varian Cary 100 and Edinburgh Instruments FSP 920 instruments respectively. The fluorescence quantum yields were measured at exc = 395 nm with respect to quinine sulfate in 1 N sulfuric acid ( f = 0.55). The absorbance of the solutions at the wavelength of excitation is ~ 0.1. All the theoretical calculations in this work were carried out using Gaussian 03 program. 2 The ground state geometries were obtained by full optimization of structural
parameters by DFT method and using spin restricted shell wavefunctions. 3,4 The geometry optimizations were carried out using Becke s three-parameter hybrid functional B3, 5 with nonlocal correlation of Lee-Yang-Parr, LYP, 6 abbreviated as B3LYP. The minimum energy nature of the stationary points was verified from vibrational frequency analysis. The excitation energies were obtained by vertical excitations of optimized ground states using TDDFT 7,8 calculations by B3LYP method. The excited (S 1 ) state geometries were optimized using ab initio restricted configuration interaction singles (RCIS) approach. 9 The emission energies were computed by TDDFT/B3LYP calculations from the relaxed excited states, i.e. using RCIS optimized excited state geometries as inputs (vertical transitions). 6-31G+** basis set is used for the calculations. Solvent stabilization effects are considered by using integral equation formalismpolarizable continuum (IEF-PCM) model. Reference: 1. N. Dash, F. A. S. Chipem, R. Swaminathan and G. Krishnamoorthy, Hydrogen bond induced twisted intramolecular charge transfer in 2-(4 -N,Ndimethylaminophenyl)imidazo[4,5-b]pyridine. Chem. Phys. Lett. 2008, 460, 119 124. 2. M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, J. A. Montgomery, Jr., T. Vreven; K. N. Kudin, J. C. Burant, J. M. Millam, S. S. Iyengar, J. Tomasi, V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega, G. A. Petersson, H. Nakatsuji, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai,
M. Klene, X. Li, J. E. Knox, H. P. Hratchian, J. B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R. E. Stratmann, O. Yazyev, A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski, P. Y. Ayala, K. Morokuma, G. A. Voth, P. Salvador, J. J. Dannenberg, V. G. Zakrzewski, S. Dapprich, A. D. Daniels, M. C. Strain, O. Farkas, D. K. Malick, A. D. Rabuck, K. Raghavachari, J. B. Foresman, J. V. Ortiz, Q. Cui, A. G. Baboul, S. Clifford, J. Cioslowski, B. B. Stefanov, G. Liu, A. Liashenko, P. Piskorz, I. Komaromi, R. L. Martin, D. J. Fox, T. Keith, M. A. Al- Laham, C. Y. Peng, A. Nanayakkara, M. Challacombe, P. M. W. Gill, B. Johnson, W. Chen, M. W. Wong, C. Gonzalez, J. A. Pople, Gaussian 03, Revision E.01, Gaussian, Inc., Wallingford CT, 2004. 3. P. Hohenberg and W. Kohn, In homogeneous electron gas, Phys. Rev. B, 1964, 136, 864 871. 4. W. Kohn and L. J. Sham, Self-consistent equations including exchange and correlation effects, Phys. Rev. A, 1965, 140, 1133 1138. 5. A. D. Becke, Density-functional thermochemistry. III. The role of exact exchange, J. Chem. Phys., 1993, 98, 5648 5652. 6. C. Lee, W. Yang and R. G. Parr, Development of the colle-salvetti correlationenergy formula into a functional of the electron density, Phys. Rev. B, 1988, 37, 785 789.
7. M. E. Casida, Time-dependent density-functional response theory for molecules, in recent advances in density functional methods, Part I; Chong, D. P., Ed.; World Scientific: Singapore, 1995, p 155. 8. E. Gross, J. Dobson and M. Petersilka, Density functional theory of timedependent phenomena, Top. Curr. Chem., 1996, 181, 81 172. 9. J. B. Foresman, M. Head-Gordon, J. A. Pople and M. J. Frisch, Toward a systematic molecular orbital theory for excited states, J. Phys. Chem., 1992, 96, 135 149. (a)(b) (c) (d) (e) 0.9 Absorbance 0.6 0.3 0 300 340 380 420 460 Wavelength (nm) Fig. S1 Normalized absorption spectra of t-dmasip-b in (a) cyclohexane, (b) dioxane, (c) acetonitrile, (d) methanol, and (e) glycerol.
Lippert-Mataga equation The Lippert-Mataga plot was constructed (Fig. 3) by using the relation SS = [2( e - g ) 2 /hca 3 ] f + SS (1) where SS is the Stokes shift, the superscript º indicates the absence of solvent, g and e are dipole moments in the ground state and the excited state, respectively, a is Onsager cavity radius. The orientation polarizability f is defined as f = [( - 1) / (2 + 1)] [(n 2 1) / (2n 2 + 1)] (2) where and n are solvent dielectric constant and refractive index respectively. 0.153 Dioxane Glycerol MeOH Acetonitrile 0.103 f 0.053 0.003 0.00275 0.00315 0.00355 1/T (K -1 ) Fig. S2 Temperature dependence of fluorescence quantum yield ( f ) of t-dmasip-b in different solvents.
2.0E+05 1.5E+05 7.4 ph Intensity (a. u.) 1.0E+05 5.0E+04 4.0 7.4 7.0 6.4 6.0 4.5 4.3 4.2 4.2 4.1 4.0 0.0E+00 432 502 572 642 712 Wavelength (nm) Fig. S3 Emission spectra ( exc = 428 nm) of t-dmasip-b in aqueous medium at ph range 9.0 to 4.0.