Supporting Information Copyright Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, 2012 Femtogram Detection of Explosive Nitroaromatics: Fluoranthene-Based Fluorescent Chemosensors N. Venkatramaiah, Shiv Kumar, and Satish Patil*[a] chem_201201764_sm_miscellaneous_information.pdf Table of Contents: 1. Synthesis of precursor materials 3 2. Single crystal X-ray analysis 11 3. Fluorescence quenching with different nitroaromatics in ethanol 14 4. NMR and electronic absorption titration experiment 15 5. Stern-Volmer plots 17 6. Selectivity 19 7. Fluorescence quenching of S 3 thin films on quartz plates exposed to saturated vapors of various nitroaromatics 20 8. Fluorescence quenching of S 3 on thin layer silica chromatographic 21 plates with picric acid 9. Computational study 22 1. Synthesis of precursor materials Scheme S1: Synthetic scheme of 1,2-bis(4-(hexyloxy)phenyl)ethyne. Synthesis of 1-(Hexyloxy)-4-iodobenzene (P1).A mixture of 4-Iodophenol (5.0 g, 22.7 mmol) and anhydrous potassium carbonate (6.28 g, 45.5 mmol) was taken in N,N-dimethylforamide (20 mL). To the above reaction mixture 1-bromohexane (5.63 g, 34.1 mmol) was added. Reaction mixture was reflux for 16hours. Reaction mixture was poured into water (150 mL) and extracted with dichloromethane. The organic layer was washed with distilled water. The organic layer was dried over anhydrous sodium sulphate, filtered and subjected to rotary evaporation. Product was further purified using column chromatography with 2% ethylacetate/hexane as eluent. Colourless liquid was obtained (90% yield). 1H NMR (400 MHz, CDCl3, 25oC, TMS): d = 7.52 (d, 3J(H,H) = 8.8 Hz, 2H), 6.66 (d,3J(H,H) = 9.2 Hz, 2H), 3.90 (t, 3J(H,H) = 6.4 Hz, 2 H), 1.79-1.75 (m, 2H), 1.47-1.43 (m, 2H), 1.35-1.31 (m, 4H), 0.90 ppm (t, 3J(H,H) = 4.32 Hz, 3 H);13C NMR (100 MHz, CDCl3, 25oC, TMS): d = 159.01, 138.12, 116.93, 82.36, 77.32, 77.00, 76.68, 68.11, 31.53, 29.09, 25.65, 22.56, 13.99 ppm Synthesis of ((4-(hexyloxy)phenyl)ethynyl)trimethylsilane (P2). A reaction mixture of compound P1 (2.0 g, 6.5 mmol), trimethylsilyacetylene (0.7 g, 7.0 mmol), bis(triphenylphosphine)palladium (II) dichloride (4% mol) and copper (I) iodide (10% mol) was taken in triethylamine (20 mL). In above reaction mixture was stirred at room temperature for 15 min and then refluxed for 4hours under argon atmosphere. Reaction mixture was cooled to room temperature and subjected to solvent evaporation under reduced pressure. Residue was directly adsorbed over silica gel and purified using column chromatography with 2% ethylacetate/hexane as eluent. Colourless liquid was obtained. 1H NMR (400 MHz, CDCl3, 25oC, TMS): d= 7.38 (d, 3 J(H,H)= 8.8 Hz, 2 H), 6.79 (d, 3J(H,H) = 8.8 Hz, 2 H), 3.93 (t, 3J(H,H) = 6.8 Hz, 2 H), 1.78- 1.72 (m, 2H), 1.46-1.42 (m, 2H), 1.34-1.31 (m, 4H), 0.90 (t, 3J(H,H) = 4.32 Hz, 3 H), 0.23 ppm (s, 9H). 13C NMR (100 MHz, CDCl3, 25oC, TMS): d = 159.36, 133.42, 115.01, 114.34, 105.34, 92.24, 77.32, 77.00, 76.68, 68.04, 31.56, 29.14, 25.67, 22.57, 13.99, 0.06 ppm Synthesis of 1-ethynyl-4-(hexyloxy)benzene (P3). Compound P2 (1.7 g, 6.2 mmol) was treated with anhydrous potassium carbonate (85 mg, 0.6 mmol) in methanol (20 mL) at room temperature for 3 hours under argon atmosphere. Solvent was evaporated and residue was extracted with dichloromethane/water mixture. Organic layer dried over anhydrous sodium sulphate, filtered and subjected to rotary evaporation. Product was further purified using column chromatography with 2% ethylacetate/hexane as eluent. Colourless liquid was obtained (95% yield). 1H NMR (400 MHz, CDCl3, 25oC, TMS): d= 7.4 (d, 3J(H,H) = 8.8 Hz, 2 H), 6.82 (d, 3 J(H,H) = 8.8 Hz, 2 H), 3.94 (t, 3J(H,H) = 6.8 Hz, 2 H), 2.98 (s, 1H), 1.80-1.73 (m, 2H), 1.53- 1.43 (m, 2H), 1.35-1.31 (m, 4H), 0.91 ppm (t, 3J(H,H) = 4.32 Hz, 3 H); 13C NMR (100 MHz, CDCl3, 25oC, TMS): d = 159.56, 133.55, 114.47, 113.89, 83.78, 77.32, 77.00, 76.68, 75.61, 68.08, 31.55, 29.12, 25.67, 22.57, 13.99 ppm Synthesis of 1,2-bis(4-(hexyloxy)phenyl)ethyne (P4). A mixture of compound P1 (1.9 g, 6.2 mmol), 3 (1.2 g, 5.9 mmol), bis(triphenylphosphinepalladium(II))dichloride (4% mol) and copper iodide (10% mol) was taken in triethylamine (10 mL). In above reaction mixture was stirred at room temperature for 15 min, and then refluxed for 4 hours under argon atmosphere. Reaction mixture was cooled to room temperature and solvent was evaporated and residue directly adsorbed over silica gel and purified using column chromatography with 2% ethylacetate/hexane as eluent. Crystalline white flakes were obtained (87% yield). 1H NMR (400 MHz, CDCl3, 25oC, TMS): d = 7.42 (d, 3J(H,H) = 8.8 Hz, 4 H), 6.82 (d, 3J(H,H) = 8.8 Hz,4 H), 3.95 (t, 3J(H,H) = 6.8 Hz, 4 H), 1.80-1.73 (m, 4H), 1.53-1.43 (m, 4H), 1.35-1.31 (m, 8H), 0.91 ppm (t, 3J(H,H) = 4.32 Hz, 6 H);13C NMR (100 MHz, CDCl3, 25oC, TMS): d = 138.17, 132.85, 115.55, 114.54, 87.98, 68.10, 31.60, 29.71, 29.20, 25.72, 22.61 ppm; elemental analysis calcd for C26H34O2: C 82.49, H 9.05, O 8.45. found: C 82.31, H 8.91. Figure A1. 1H NMR spectra of compoudP1. Figure A2. 13C NMR spectra of compoudP1. 1 0 5 5DZ ' DW D 69 + 1 0 5 0 + ] &' &O i - +] + G - +] + W - +] + ± P + ± P + ± P + W - + & &+ 2 6L &+ &+ I SSP 1 Figure A3. H NMR spectra of compoudP2. + ] + V+ Figure A4. 13C NMR spectra of compoudP2. Figure A5. 1H NMR spectra of compoudP3. Figure A6. 13C NMR spectra of compoudP3. Figure A7. 1H NMR spectra of compoudP4. Figure A8. 13C NMR spectra of compoudP4. ' HVNW RS 6 - + 1 0 5 0 + ] &' &O i - +] + G + ] + GG - + ] + ± P + V+ W - +] + W - +] + G +] + - +] + G + & &+ 2 2 %U %U ' HVNW RS 6 I SSP I SSP - +] + G - +] + G - +] + W Figure A9. 1H NMR spectra of compoudS3. Figure A10. 13C NMR spectra of compoudS3. 2. Single crystal X-ray analysis Single crystal X-ray diffraction data was collected at 120 K on an Oxford Xcalibur (Mova) diffractometer equipped with a EOS CCD detector using MoKa radiation (λ= 0.71073Å).1 The crystal was maintained at the desired temperature during data collection using the Oxford instruments Cryojet-HT controller. The structure was solved by direct methods using SHELXS97 and refined against F2 using SHELXL-97.2 H-atoms were fixed geometrically and refined isotropically. The WinGX package was used for refinement and production of data tables, and ORTEP-3 for structure visualization and making molecular representations showing the ellipsoids at 30% probability level.3 Figure A11. The Unit cell packing diagram of S3. Table S1. Crystal data and structure refinement parameters for S3. Compound S3 Formula C 52H48Br2O2 Formula weight 864.70 Crystal system Monoclinic Space group P21/c a (Å) 12.9766(25) b (Å) 22.9702(20) c (Å) 14.7832(18) a (°) 90 ß (°) 105.208(15) ? (°) 90 Volume (Å3) 4252.19(180) Z 4 Density (gcm-3) 1.35 µ (mm-1) 1.947 F (000) 1783.8 h min, max -15, 14 k min, max -27, 23 l min, max -17, 16 No. of measured reflections No. of unique reflections No. of reflections used R_ all, R_obs 15231 0.242, 0.083 wR2_ all, wR2_obs 0.134, 0.098 7422 2762 ∆ρmin,max (e Å-3) -0.507, 0.563 GOOF 0.869 3. Fluorescence quenching with different nitroaromatics in ethanol Figure A12. The spectrofluorometric addition of different concentrations of various nitroaromatics to S3 (5x10 -6, M) in ethanol at 25°C. The circles indicate the formation of new emission peak upon addition of DDQ and PAQ to S3. NT: 4-nitro toluene, DNT: 2,4dinitrotoluene, TNT:2,4,6 trinitrotoluene, DNP: 2,4 dinitrophenol. 4. NMR and electronic absorption titration experiment (a) (b) Figure A13. The 1H NMR spectra S3 treated with different mole ratio of picric acid (a) complete region (b) aromatic region. The formation of donor-acceptor complex was studied by 1H NMR spectroscopic analysis. In a typical 1H NMR titration experiment, a pale yellow solution of picric acid was mixed with fluorophore S3 in different mole ratios and is shown in the figure. Upon addition of PA to S3, at 1:0.25 mole ratio, we have observed a significant up field shift of the proton resonance at 7.75 ppm (doublet) corresponding to S3. The subsequent increase in the mole ratio of S3 and PA, the progressive up field shift from 7.75 ppm to 7.72 ppm was observed up to 1:1 mole ratio and reaches to equilibrium. Further increase in the concentration of PA, we have not observed any significant change in the spectral pattern. This indicates that the gradual up field shift is attributed to bound charge transfer complex. The formation of charge transfer complex was further confirmed by electronic absorption spectra. Figure A14. The spectrophotometric titration of S3 (5x10-6) with different concentrations of picric acid. The spectrophometric titration of S3 (5x10-6 M) with different concentrations of picric acid (PA) in ethanol is shown in the figure. Upon gradual addition of PA to S3, slight increase in the absorption maxima at 303 nm with formation new broad absorption peak at 424 nm. The intensity of the new absorption peak gradually increases with increase in the concentration of PA. This indicates the formation of donor-acceptor complex between the p-electron rich S3 fluorophore and picric acid. Similar results were observed upon treated S3 with other electron deficient nitroaromatics. 5. Stern-Volmer plots The quenching behavior was studied by Stern-Volmer equation Io/I=1+Ksv[Q], where Io, I are the fluorescence intensity before and after addition of the quencher, Ksv is the Stern-Volmer quenching rate constant and [Q] is the concentration of the quencher. Linear SV response was observed for common analytes indicating static quenching behaviour. However, the highly electron deficient compounds like DDQ, PAQ chloronil and ANQ shows non-linear behaviour at high concentration suggesting that the fluorescence quenching of S1 follows both static as well as dynamic quenching pathways through the ground state complex formation. 1.12 Io/I 1.08 2.4 DCB DBB 4-BBA 4-Apy 4-Hpy 2ClBN 2 I o /I 1.16 1.6 BQ AQ 1-ClAQ DDQ ANQ chloronil 1.04 1.2 1 0.96 0.E+00 2.E-04 4.E-04 6.E-04 Conc.of Quencher, M 0.8 0.E+00 2.E-04 4.E-04 6.E-04 Conc. of Quenchers, M Figure A15. The Stern-Volmer plots for different concentrations of various analytes. The curves for DDQ, 1-ClAQ, Chloronil and 1-ClAQ shows presence of both static and dyanmic quenching when treated with S3. 6. Selectivity Figure A16. The change in the fluorescent intensity of S3 upon addition of 10 µL of various analytes before and after exposure to the UV light at 365 nm. DCB (1,4-dichloro benzene), BBA(4-bromo benzoic acid), APy (4-amino Pyridine), HPy(4-hydroxy Pyridine), BP(benzophenone), AQ(anthraquinone), DDQ (1,2 dichloro 4,5-dicyano benzoquinone), PA(picric acid),TNT(2,4,6-trinitrotoulene), DNP(2,4,6-trinitro phenol), dinitrotoulene), NT (4-nitro toluene), NP(4-nitro phenol) and NB (nitro benzene). DNT (2,4,- 7. Fluorescence quenching of S3 thin film on quartz plated exposed to saturated vapors of various nitroaromatics Saturated vapors of different nitroaromatics were generated by keeping the compounds in a sealed tube for three days to ensure that the equilibrated vapor pressure is reached. The solid state fluorescence quenching study was carried out by keeping the quartz plate in sealed tubes for specific time. The fluorescence spectra of the exposed films were recorded immediately after taking out from the sealed tube without any delay. Figure A17. The time dependent emission spectra of S3 thin film upon exposure to saturated vapors of various nitroaromatics at 60 sec interval of time. 8. Fluorescence quenching of S3 on thin layer silica chromatographic plates with picric acid The high concentration of S3 (1x10 -3 M) solution was prepared in chloroform. Thin layer silica chromatographic plates (200µm. Sigma Aldrich) were kept into the solution and allow to move in solvent front on the chromatographic plate. The explosive solutions of various concentrations were spotted on to the thinlayer silica chromatographic plate and allowed to dry completely in vacuum. After evaporation the test pieces of the plates were exposed to UV light 0f 365 nm was imaged to digital camera. Also a fluorescence spectrum wasrecorded to study the quantitative quenching efficiency. Figure A18. Fluorescence quenching of S3 on thin layer silica chromatographic plate with picric acid 9. Computational study Figure A19. Electron density profiles for different types of S 3-TNT complexes -1 LUMO -1.79 -2.97 -3 HOMO -2.91 -3.48 Energy (eV) -3.89 -5 -5.41 -7 -8.22 -8.11 -7.95 -8.43 -9 S3 PA TNT DNT NT Figure A20. The energy level diagram of S3with other nitroaromatics.