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: marianny@uis.edu.co

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.

4-Chlorostyrene (9)

Starting from 4-chlorobenzaldehyde. Styrene 9 was obtained as colorless oil. Eluent: ethyl acetate:n-hexane (2:9). Yield: 78%. 1H NMR (CDCl3, 400 MHz, ppm): 5.27 (d, 1H J=10.6 Hz), 5.70 (d, 1H J=17.2 Hz), 6.66 (dd, 1H J=17.2 Hz), 7.25 (d, 2H), 7.31 (d, 2H).

3,4,5-Trimethoxystyrene (10)

Starting from 3,4,5-trimethoxybenzaldehyde. Styrene 10 was obtained as yellowish oil. Eluent: ethyl acetate:n-hexane (1:2). Yield: 88%. 1H NMR (CDCl3, 400 MHz, ppm): 3.81 (s, 3H), 3.89 (s, 6H), 5.19 (dd, 1H J=10.3 Hz), 5.62 (dd, 1H J=16.9 Hz), 6.58 (dd, 1H), 6.60 (s, 2H J=16.9Hz).

Divinylbencene (11)

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

192-194ºC). 1H NMR (acetone-d6, 400 MHz, ppm): 7.29 (s, 2 H), 8.83 (s, 2 H). 13C NMR (acetone-d6, 100 MHz, ppm): 83.15, 123.65, 150.43.

2,5-Diiodo-1,4-bis(2-ethoxyethanoyl)benzene (16)

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

temprature a crystalline brownish solid. Yield: 80%. m.p. 169-170 °C (lit.3 163-165ºC). 1H NMR (DMSO-d6, 400 MHz, ppm): 3.67 (m, 4H), 3.97 (t, 4H), 4.83 (t, 2H), 7.36 (s, 2H). 13C NMR (DMSO-d6, 100 MHz, ppm): 60.55, 72.80, 88.00, 123.99, 153.60. HRMS calculated: 450.0119, found: 450.0123.

Methyl-4-vinylbenzoate (17)

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.

E,E- 2,5-Dimethoxy-1,4-bis[2-(4-chlorostyril)] benzene (PV-Cl)

Starting from 4-chlorostyrene and 1,4-diiodo-2,5-dimethoxybenzene. Reaction time: 32 h. Green brilliant solid recrystallized from methanol. Yield 95%. m.p. 220-223ºC (lit.5 212 ºC). 1H NMR (CDCl3, 400 MHz, ppm): 3,94 (s, 6H), 7,09 (d, 2H, J: 16,4Hz), 7,13 (s, 2H), 7,34 (d,4H), 7.47 (dd, 6H). Molecular Weight: Calculated: 410.084. Found: 410.08 (MALDI-TOF).

E,E-1,4-Bis[2-(4-methoxy nitrostyril)] benzene (PV-NO2 )

Starting from 1,4-diiodo-2,5-dimethoxylbenzene and 4-nitrostyrene. Reaction time: 48 h. Red solid recrystallized from Chloroform-methanol Yield 91%. m.p. 278-280 °C, (lit.5 274-278 °C). 1H NMR (400 MHz, CDCl3, ppm): 3,95(s, 6H), 7,18 (s, 2H), 7,21(d, 2H), 7,67(d, 2H), 7,74 (d, 4H), 8,25(d, 4H).

E,E-1,4-Bis[2-(4-methyl carboxylatestyril)] benzene (PV-COOCH3)

Starting from 1,4-diiodo-2,5-dimethylbenzene and methyl-4-vinylbenzoate. Reaction time: 48 h. Light yellowish-green solid recrystallized from toluene. Yield 91%. m.p. 232-234ºC. 1H NMR (DMSO-d6, 400 MHz, ppm): 2,45 (s, 6H), 4.33 (s, 6H), 7,04 (d, 2H J=16.8 Hz), 7.41 (d, 2H), 7,48 (s, 2H), 7,58 (d, 4H), 8,07 (d,4H). 13C NMR (DMSO-d6, 100 MHz, ppm): 20.13, 61.5, 126.9, 128.06, 128.96, 129.3, 129.89, 130.6, 134.55, 136.11, 142.62, 166.98.

E,E-2,5-Dimethyl-1,4-bis[2-(4-methyl carboxylatestyril)] benzene (PV-COOCH3-CH3)

Starting from divinylbenzene and methyl-4-iodobenzoate. Reaction time: 46 hours. Blue solid recrystallized from toluene to yield 88%. m.p. 243-245ºC. 1H NMR (DMSO-d6, 400 MHz, ppm): 4,39 (s, 6H), 7,18 (d, 2H

J=16.2 Hz) 7,23 (d, 2H), 7.53 (s, 4H), 7.61 (d, 4H), 8.04 (d, 4H). 13C NMR (DMSO-d6, 100 MHz, ppm): 60.83, 125.93, 127.32, 127.93, 129.40, 130.18, 130.68, 136.55, 141.89, 167.86.

E,E-2,5-Dimethoxy-1,4-bis(3,4,5-trimethoxystyryl) benzene (PV-OCH3)

Starting from 3,4,5-trimethoxybencene and 1,4-diiodo-2,5-dimethoxybenzene. Reaction time: 48 h. Yellow solid recrystallized from chloroform to yield: 98%. m.p. 257-259°C (lit.3 256-257ºC) 1H NMR (CDCl3, 400 MHz, ppm): 3,90 (s, 6H), 3,96 (s, 12H), 3,98 (s, 6H), 6,80 (s, 4H), 7,08 (d, 2H 16), 7,15 (s, 2H), 7,39 (d, 2H). Molecular Weight: Calculated: 522.22, found: 522.28 (MALDI-TOF).

E,E-2,5-Bis(2-hydroxyethoxy)-1,4-bis(3,4,5-trimethoxystyryl)benzene (PV-OH)

Starting from 3,4,5-trimethoxybenzene and 2,5-diiodo-1,4-bis(2-ethoxyethanoyl)benzene. Reaction time: 48 h. Yellow solid recrystallized from chloroform to yield: 95%. m.p. 246-248°C (lit.3 246-248ºC). 1H NMR (DMSO-d6, 400 MHz, ppm): 3,67 (s, 6 H), 3.82 (m, 16 H), 4,08 (t, 4H), 6,89 (s, 4H), 7,3 (d, 2H), 7,45 (d, 2H), 7,34 (s, 2H). Molecular Weight: Calculated: 528.246, found: 528.25 (MALDI-TOF).

E,E-1,4-Bis(4-cyanostyril) benzene (PV-CN)

Starting from 4-bromobenzonitrile and divinylbenzene. Reaction time: 24 h. Green solid recrystallized from methanol. Yield 60%. m.p. 280-282ºC (lit.5 212 ºC). 1H NMR (DMSO-d6, 400 MHz, ppm): 2,43 (s, 6H), 7,18 (dd, 2H, J: 16,3Hz), 7,41 (dd, 2H, J: 16,4Hz), 7,58 (d, 4H), 7.47 (dd, 10H, J: 10,4Hz). Molecular Weight: Calculated: 332.132. Found: 332.145 (MALDI-TOF).

E,E-2,5-Dimethoxy-1,4-bis[2-(4-methyl carboxylatestyril)] benzene (PV-COOCH3-OCH3)

Starting from ethyl-4-vinylbenzoate and 1,4-diiodo-2,5-dimethoxybenzene. Reaction time: 48 hours. Yellow solid recrystallized from toluene to yield 92%. m.p. 194-196ºC (lit.5 212 ºC). 1H NMR (CDCl3, 400 MHz, ppm): 1.41 (t, 6H, J= 7.1 Hz), 3.95 (s, 6H), 4.39 (q, 4H, J= 7.1 Hz), 7.15 (s, 2H), 7.17 (d, 2H, J= 16.4 Hz), 7.59 (m, 6H), 8.03 (d, 4H, J = 8.2 Hz). RMN-13C (100 MHz, ppm): 14.5, 56.4, 61.1, 109.2, 125.6, 126.5, 126.6, 128.2, 129.2, 130.1 142.2, 151.6, 166.6. MS m/z (rel. int.): 487.1 (M+H)+.

PVs Hydrolysis

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.

E,E-1,4-Bis[2-(4-carboxystyril)] benzene (PV-COOH)

Starting from PV-COOCH3, after 14 h give a light blue solid recrystallized from toluene. Yield: 97%. m.p. 271-273. 1H NMR (DMSO-d6, 400 MHz, ppm): 7.38 (d, 2H), 7,45 (d, 4H), 7,69 (S, 4H), 7,74 (d, 4H), 7,95 (d, 4H). 13C NMR (DMSO-d6, 100 MHz, ppm): 125.98, 127.47, 128.01, 129.85, 130.05, 130.84, 137.06, 141.54,

167.48. IR (KBr, cm-1): 3253 (O-H), 3073 (C-H arom.), 2919 (C-H alkyl), 1673 (C=O), 1035 (C-O), 952 (C=C trans). Molecular Weight: Calculated: 370.121, found: 370.156 (MALDI-TOF).

E,E-2,5-Dimethyl-1,4-bis[2-(4-carboxystyril)] benzene (PV-COOH-CH3)

Starting from PV-COOCH3-CH3, after 16 h give a light green solid recrystallized from toluene. Yield: 98%. m.p. 258-260. 1H NMR (DMSO-d6, 400 MHz, ppm): 2,45 (s, 6H), 7,25 (d, 2H), 7.61 (d, 2H), 7,64 (s, 2H), 7,79 (d, 2H), 7,98 (d,4H). 13C NMR (DMSO-d6, 100 MHz, ppm): 19.01, 126.48, 126.94, 127.91, 129.53, 133.51, 167.09. IR (KBr, cm-1): 3233 (O-H), 3018 (C-H arom.), 2943 (C-H alkyl), 1678 (C=O), 1072 (C-O), 953 (C=C trans). Molecular Weight: Calculated: 398.152, found: 398.114 (MALDI-TOF).

E,E-2,5-Dimethoxy-1,4-bis[2-(4-carboxylatestyril)] benzene (PV-COOH-OCH3)

Starting from PV-COOCH3-OCH3, after 3 h give a light yellow solid recrystallized from CH3CN. Yield: 94%. m.p. 233-234ºC (lit.5 212 ºC). RMN-1H (400 MHz, DMSO-d6, ppm): 3.92 (s, 6H), 7.39 (s, 2H), 7.45 (d, 2H, J= 16.4 Hz), 7.57 (d, 2H, J= 16.5 Hz), 7.69 (d, 4H, J= 8.2 Hz), 7.95 (d, 4H, J= 8.2 Hz). RMN-13C (100 MHz, DMSO-d6, ppm): 56.3, 109.6, 125.0, 125.9, 126.4, 128.3, 129.4, 129.9, 141.8, 151.3, 167.1. IR (KBr, cm -1): 3039 (m), 2962 (m), 2862 (m), 2792 (m), 1705 (f), 1604 (m), 1581 (d), 1481 (d), 1435 (f), 1365 (m), 1319 (d), 1203 (f), 1172 (f), 1111 (f), 1018 (m), 995 (d), 871 (m), 840 (m), 786 (m), 717 (f), 686 (f), 617 (m), 532 (m), 478 (f). MS m/z (rel. int.): 431.1 (M+H)+.

S2. PV derivatives molar absorptivity

S2. PVs molar absorptivities at 355 nm.

S3. Isotopic pattern comparison of PV matrix signals

Matrixm/z Abundance

Experimental Calculated Experimental Calculated

PV-CN332.156 332.131 100.00 100.00333.162 333.134 26.56 26.88334.158 334.138 8.26 3.47

PV-COOH370.122 370.120 100.00 100.00371.133 371.123 24.03 26.32372.135 372.127 2.02 4.14

PV-COOH-CH3

398.163 398.151 100.00 100.00399.175 399.154 24.03 26.32400.184 400.158 2.02 4.14

PV-COOH-OCH3

430.148 430.141 100.00 100.00431.151 431.144 24.63 28.60432.145 432.148 3.33 5.17

PV-Cl

410.091 410,083 100.00 100.00411.108 411,087 26.58 26.19412.106 412,081 66.76 67.62413.115 413,084 18.04 17.11414.114 414,078 12.87 12.59415.120 415,081 2.40 2.91

PV-NO2

432.136 432.132 100.00 100.00433.155 433.135 25.88 27.16434.158 434.138 3.23 4.78

PV-OH582.236 582.246 100.00 100.00583.241 583.249 32.58 35.43584.251 584.253 7.90 8.14

PV-OCH3

522.255 522.225 100.00 100.00523.257 523.228 31.37 33.14524.265 524.232 6.96 6.96

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

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