Oligo p-phenylenevinylene derivatives as electron transfer matrices for UV-MALDI Laura J. Castellanos-García, a Brian Castro Agudelo, b Hernando F. Rosales, a Melisa Cely, b Christian Ochoa-Puentes, b Cristian Blanco-Tirado, a Cesar A. Sierra a and Marianny Y. Combariza *a a. Escuela de Química, Universidad Industrial de Santander, Bucaramanga, Santander, Colombia. b. Departamento de Química, Universidad Nacional de Colombia, Bogotá, Colombia * Corresponding author. Email: [email protected]S1. PV derivatives Synthesis To obtain the PV targets by means of the Mizoroki-Heck coupling reaction, firstly a series of precursors were synthesised. These precursors involved methodologies such as Wittig reaction, S E Ar, basic hydrolysis and esterification. General procedure for the synthesis of styrene derivatives: Under N 2 atmosphere and room temperature, methyl triphenylphosphonium bromide was added very slowly to a solution of potassium tert-butoxyde in THF. The reaction mixture was stirred 15 minutes before the respective p- substituted aldehyde was added. The resulting mixture was stirred at 60°C for a further 18 hours, then cooled to room temperature and filtered leaving a solid that was washed 3 times with n-hexane. The filtrate and the
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Oligo p-phenylenevinylene derivatives as electron transfer matrices for
UV-MALDILaura J. Castellanos-García,a Brian Castro Agudelo,b Hernando F. Rosales,a Melisa Cely,b Christian Ochoa-Puentes,b Cristian Blanco-Tirado,a Cesar A. Sierraa and Marianny Y. Combariza*a
a. Escuela de Química, Universidad Industrial de Santander, Bucaramanga, Santander, Colombia.b. Departamento de Química, Universidad Nacional de Colombia, Bogotá, Colombia* Corresponding author. Email: [email protected]
S1. PV derivatives Synthesis
To obtain the PV targets by means of the Mizoroki-Heck coupling reaction, firstly a series of precursors were synthesised. These precursors involved methodologies such as Wittig reaction, SEAr, basic hydrolysis and esterification.
General procedure for the synthesis of styrene derivatives:
Under N2 atmosphere and room temperature, methyl triphenylphosphonium bromide was added very slowly to a solution of potassium tert-butoxyde in THF. The reaction mixture was stirred 15 minutes before the respective p-substituted aldehyde was added. The resulting mixture was stirred at 60°C for a further 18 hours, then cooled to room temperature and filtered leaving a solid that was washed 3 times with n-hexane. The filtrate and the n-hexane fractions were mix together, and distilled under reduced pressure to obtain a white solid. Finally, column chromatography with the respective eluent, and subsequent concentration gave the correspondent styrene derivative.
Staring from terephthalaldehyde. Styrene 11 was obtained as a white solid with low melting point. Eluent: n-hexane. Yield: 68%. 1H NMR (CDCl3, 400 MHz, ppm): 5.21 (d, 2H), 5.73 (d, 2H J=17.6 Hz), 6.68 (dd, 2H J=17.6 Hz), 7.33 (s, 4H).
4-Nitrostyrene (12)
Staring from 4-nitrobenzaldehyde. Styrene 12 was obtained as a light brown oil. Eluent: n-hexane. Yield: 70%. 1H NMR (400 MHz, CDCl3, ppm): 8,87(d, 2H), 7,55(d,2H), 6,70 (dd, 1H), 5,94(d, 1H), 5,52 (d, 1H)
General procedure for the iodination of aromatic compounds:
In a three-neck rounded flask, a mixture of iodine, sodium periodate and the respective dialkyl or dialkoxy benzene in a solution of glacial acetic acid, water and sulfuric acid (10:1:0.1) was stirred under reflux for 12 hours. The mixture was cooled to room temperature and sodium bisulphite was added. The product was isolated by filtration and washed three times with distilled water. Recrystallization using the appropriate solvent gave the target product.
1,4-Diiodo-2,5-dimethoxybencene (13)
Starting from 1,4-dimethoxybenzene and recrystallization with ethanol-chloroform (1:1) gives 13 as a white cream solid. Yield 75%. m.p. 174-176 °C. (lit.1171-173) 1H NMR (CDCl3, 400 MHz, ppm): 3,81 (s, 6H), 7,10 (s, 2H). 13C NMR (CDCl3, 100 MHz, ppm): 57.13, 86.12, 122.41, 154.23.
1,4-Diiodo-2,5-dimethylbenzene (14)
Starting from 4-dimethylbenzene and recrystallization with cyclohexane gives 14 as a white solid. Yield 78%. m.p. 103-104 °C. (lit.2 102-103) 1H NMR (CDCl3, 400 MHz, ppm): 5,00 (s, 6H), 7,66 (s, 2H). 13C NMR (CDCl3, 100 MHz, ppm): 28.13, 102.52, 138.41, 141.73.
2,5-Diiodo-1,4-dihydroquinone (15)
Boron tribromide was added drop wise to a -78°C solution of halogenated 14 in dry dichloromethane, followed by stirring at this temperature for 5 h. The mixture was allowed to reach room temperature, filtered to give a white solid product after recrystallization from ethanol-dicloromethane (1:1). Yield 92%. m.p. 195-197°C (lit.3
To a mixture of quinone 15 and potassium carbonate in dry DMF under argon atmosphere was added 2-chloroethanol and the temperature was set to 80°C. 48 h later the reaction was cooled to room temperature, filtered and the residue washed with DMF. Then, the filtrate was concentrated by evaporation to obtain a black solid. This solid was refluxed with activated charcoal in acetone during 30 min, to give after filtration at room
A mixture of 4-vinylbenzoic acid and sulfuric acid (1% mol) in methanol was refluxed for 12 h. After cooling, the resulting mixture was extracted with dichloromethane and the organic phase extracted with sodium bicarbonate (10%, 3 x 10mL). Then, the organic phase was dried with anhydrous sodium sulfate, and the solvent removed by vacuum to give 17 as white solid powder. m.p. 29-30°C (lit.4 29-30ºC). 1H NMR (CDCl3, 400 MHz, ppm): 3.91 (s, 3H), 5.40 (dd, 2H), 5.86 (dd, 2H), 6.74 (dd, 1H), 7.46–7.44 (m, H), 8.03–7.98 (m, H). 13C NMR (CDCl3, 100 MHz, ppm): 52.2, 116.6, 126.2, 129.4, 130.0, 136.1, 142.0, 167.0.
Cross-coupling Mizoroki-Heck reaction
General procedure:
To a mixture of Pd(dba)2, triphenilphosphite and triethylamine (1, 10 and 500% mol, respectively) in dry DMF under N2 were added the appropriate styrene and the iodoaromatic derivative. The mixture was stirred at 120°C until the precursors disappear according to thin layer chromatography analysis. Then, the reaction mixture was poured into 5% HCl to give a precipitate, that was collected and washed, dried and solubilized again in a proper solvent. This solution was filtered over celite and recrystallized (solvent described bellow) to obtain the respective oPV compound.
The above obtained oPV esters were submitted to basic hydrolysis as described below to get the carboxylic acids targets.
General procedure:
To a solution of the respective oPV ester in THF:H2O:MeOH (1:1:1) was added 3 eq. of KOH. The resulting mixture was stirred and refluxed overnight, and then neutralized with HCl (10% vol). The precipitate was collected and purified by recristalization in toluene.
S3. Isotopic pattern comparison of experimental and calculated m/z ratios and abundances of PV matrices.
S4. DCTB Mass Spectrum
S4. DCTB MS spectrum at 1.09 µJ per pulse. m/z 250 [M]+., m/z 501 [2M+H]+, m/z 751 [3M+H]+, m/z 1001 [4M+H]+, and m/z 1251 [5M+H]+.
S5. Signal to noise ratios (S/N) and resolution for PV derivatives and DCTB molecular ions (M+.) as a function of laser pulse energy.
Figure S5 shows signal to noise (S/N) ratio and resolution evolution for PV derivatives molecular ions as a
function of laser pulse energy. As expected S/N ratios increase steeply and reach a maximum at about two-three
times above the PVs detection threshold; as laser pulse energy increases S/N decrease abruptly due probably to
excessive matrix ablation and fragmentation that increase spectral noise. PV derivatives exhibit maximal S/N
ratios at 0.59 µJ (S/N: 55,600) for PV-OCH3, 0.89 µJ (S/N: 25,900) for PV-OH, 0.80 µJ (S/N: 38,000) for PV-
Cl, 0,89 µJ (S/N: 20,600) for PV-NO2, 0.89 µJ (S/N: 26,900) for PV-COOH-CH3, 1.61 µJ (S/N: 25,781) for
PV-COOH, 0.89 µJ (S/N: 5,421) for PV-COOH-OCH3 and 0.72 µJ (S/N: 5,218) for PV-CN. For DCTB a
maximum S/N: 74,5 was observed at 1.09 µJ (see Supporting information, S6). Likewise, high laser power
promotes a decrease in the resolution of the signals due to an increased width in temporal, spatial and kinetic
energy distributions. When compared with the PV derivatives DCTB signal to noise (S/N) ratio and resolution
plots do not seem to vary due to their low values, however the plot structure follows the same trend as the PVs.
S6. S/N and Resolution graphs for DCTB
S6. Signal to noise ratio and resolution plots for DCTB [M]+. signal.
S7. NP MALDI using a 1:100 analyte:matrix molar ratio
S7. NP MS spectra using 25 pmol of NP. a) LDI. NP MALDI analysis using matrix with 1:100 Analyte:Matrix molar ratio: b) DCTB c) PV-CN and d) PV-COOH-CH3.
S8. S/N of naphthopyrene Ionization using different matrices
S8. Naphthopyrene ionization using different MALDI matrices.
S9. Cobalt Porphyrin (Co-Po) mass spectra using different PV Matrices
S9. Cobalt Porphyrin (Co-Po) mass spectra using different PV Matrices: a) PV-CN, b) PV-Cl, and c) PV-COOH-CH3. Each spot contains 5 pmol of cobalt porphyrin with 1:500 analyte:matriz molar ratio. For this analyte, no signal is obtained in LDI or in MALDI with PV-COOH-OCH3 and DCTB matrices at the laser fluence used (0.88 µJ). Inserts show a zoom of the 791 Cobalt Porphyrin [Co-Po]+. ion.
S10. Phthalocyanine (Ph) mass spectra using different PV Matrices
S10. Phthalocyanine (Ph) mass spectra using different PV Matrices: a) PV-CN, b) PV-Cl, c) PV-COOH-CH3
and d) PV-COOH-OCH3. Each spot contains 5 pmol of pthalocyanine with 1:500 analyte:matriz molar ratio. For this analyte, no signal is obtained in LDI or in MALDI with DCTB matrix at the laser fluence used (0.88 µJ). Inserts show a zoom of the 514 phthalocyanine [Ph]+. ion.
S11. Zinc Phthalocyanine (Zn-Ph) mass spectra
S11. Zinc Phthalocyanine (Zn-Ph) mass spectra using a) LDI and different PV Matrices: b) PV-CN, c) PV-Cl, d) PV-COOH-CH3 and e) PV-COOH-OCH3. Each spot contains 5 pmol of Zn-Ph. In the MALDI experiments the analyte:matriz molar ratio is 1:500. For Zn-Ph, no signal is obtained in MALDI with DCTB at the laser fluence used (0.88 µJ). Inserts show a zoom of the 576 Zinc Phthalocyanine [Zn-Ph]+. ion.
S12. Rubrene (Rb) mass spectra using different PV Matrices
S12. Rubrene (Rb) mass spectra using different PV Matrices: a) PV-CN, b) PV-Cl, c) PV-COOH-CH3 and d) PV-COOH-OCH3. Each spot contains 5 pmol of rubrene with 1:500 analyte:matriz molar ratio. For this analyte, no signal is obtained in LDI or in MALDI with DCTB matrix at the laser fluence used (0.88 µJ). Inserts show a zoom of the 532 rubrene [Rb]+. ion.
S13. Coronene (CR) mass spectra
S13. Coronene (CR) mass spectra using a) LDI and different PV Matrices: b) PV-CN, c) PV-Cl, d) PV-COOH-CH3 and e) PV-COOH-OCH3. Each spot contains 5 pmol of CR. In the MALDI experiments the analyte:matriz molar ratio is 1:500. For CR, no signal is obtained in MALDI with DCTB at the laser fluence used (0.88 µJ). Inserts show a zoom of the 300 coronene [CR]+. ion.
S14. DCTB LOD
S14. NP MALDI MS spectra at 250 fmol on target. Analyte:Matrix ratio 1:10000 using: a) DCTB, b)PV-CN and c)PV-COOH-CH3 as matrices.
S15. Ion appearance and S/N curves for molecular radical cation formation
S15. Ion appearance and S/N curves for molecular radical cation formation of a) rubrene (m/z 532.219) b) cobalt porphyrin (m/z 791.206), c) zinc phthalocyanine (m/z 576.079) and d) coronene (m/z 300.094) using PV derivatives as matrices.
References
1. Alzate, D.; Hinestroza, J.; Sierra, C. Synth. Comm. 2013, 43, 2280 – 2285.2. Nathaniel, I.; Benin, V.; Morgan, A.. Synth. Comm. 2013, 43, 1831 – 18363. Sierra, Cesar.; Lahti, P. J. Phys. Chem. A. 2006, 110, 44, 12081–12088
Tomsho, J.; McGuire, J.; Coward, J. Organic and Biomolecular Chemistry. 2005, 3, 3388 – 33984. Saiyed, A.; Patel, K..; Kamath, B.; Bedekar, V. Tetrahedron Lett. 2012 , 53, 4692 – 46965. Nakaya, T.; Imoto, M. Bull. Chem. Soc. Jap. 1966, 39, 1547 – 1551