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monoimide diester
Dyes and Pigments 98 (2013) 450e458
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Dyes and Pigments journal homepage: www.elsevier.com/locate/dyepig
Facile synthesis and controllable bromination of asymmetrical intermediates of perylene monoanhydride/monoimide diester Rongzhou Wang, Zhiqiang Shi*, Cuicui Zhang, Andong Zhang, Jiao Chen, Weiwei Guo, Zhaozhen Sun Department of Chemistry, Shandong Normal University, Jinan 250014, PR China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 20 February 2013 Received in revised form 4 April 2013 Accepted 6 April 2013 Available online 15 April 2013
Dibutyl-perylene-3,4-anhydride-9,10-dicarbonylate (1) as an asymmetrical intermediate was synthesized in 80% yield by precipitation of the less soluble target molecule, which was formed through acidic hydrolysis of tetraesters of perylene tetracarboxylic acids at one side in a mixed solvent system. Based on the intermediate, two other asymmetrical intermediates 2 and 3 with monoimide group were also synthesized in high yields. The mono-bromination and di-bromination of 3 typical intermediates could be controlled by using different bromine concentration. The chemical structures of the brominated products and ratios of their isomers were confirmed directly or deduced from their phenol substituted products with MS and NMR spectra. The bromination of the intermediates mainly afforded isomers, but intermediates 1 and 2 could afford unique di-brominated product and mono-brominated product respectively. The bromination of the intermediates led to only slight changes in absorption spectra, but relatively obvious changes in emission spectra. Ó 2013 Elsevier Ltd. All rights reserved.
Keywords: Dye Asymmetrical intermediate Perylene monoanhydride/monoimide diester Bromination Isomers Photophysical property
1. Introduction In recent years, perylene dyes have received much attention due to their electron acceptor ability, high fluorescence quantum yield, semiconducting and photoconducting properties [1e8], and therefore they have been extensively utilized for various applications such as field effect transistors, organic light-emitting diodes, organic solar cells, optical switches, sensors, liquid crystals, and so forth [9e 17]. Among the perylene dyes, perylene tetracarboxylic bisimide (PBI) dyes represent a classical example of an inherently robust and outstandingly versatile family of perylene dyes [18e21]. Compared with PBIs, the tetraesters of perylene tetracarboxylic acids (PTE) were highly soluble in common organic solvents by introduction of four flexible alkyl chains [22]. However, the single site reaction of both PBI and PTE was hard to be controlled because their reactions symmetrically took place in most of the cases and the products usually continued to be with symmetrical structures. Asymmetrical structure sometime is very useful in novel electron or energy donoreacceptor dyads designing, molecular recognition and other
* Corresponding author. Tel.: þ86 531 86182540; fax: þ86 531 82615258. E-mail addresses: [email protected], [email protected] (Z. Shi). 0143-7208/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.dyepig.2013.04.006
special applications. Perylene-monoimide (PMI) has been a useful intermediate for designing of asymmetrical perylene dyes. But due to its low yield, the synthetic chemistry of PMI dyes has developed slowly over the past years [23e25]. Perylene monoanhydride diester is also an asymmetrical intermediate [26]. Compared with PBI and PMI, Perylene monoanhydride diester is better soluble and more versatile. Through the anhydride group, various asymmetrical N-substituted perylene dyes can be readily accessed via formation of the imide. The diester groups enable the dyes good solubility, and also may be facilely transformed to the second anhydride group via acidic hydrolysis [26]. The second anhydride group can either be cut to prepare PMI in refluxed quinoline in presence of Cu2O [27], or be introduced different N-substituted groups to form new asymmetrical PBIs with high yields [5]. Besides introducing substitutes at the imide group [28], another important strategy to modify the perylene dyes was introducing substituents at the carbocyclic scaffold in the so-called bay-area of the perylene core [29e33]. The later strategy was more elaborate. For example, aryloxy-, cyano-, pyrrolidino, alkoxy and/or alkylthiosubstituted PBIs as well as the Suzuki coupling reaction of PBI have been extensively investigated. Usually the readily accessed halogenated PBIs, especially diBr-PBIs were used as starting materials [34]. Therefore, the bromination of the asymmetrical intermediate
R. Wang et al. / Dyes and Pigments 98 (2013) 450e458
will be the crucial step in further modification of the asymmetrical perylene dyes at bay positions in order to development and abundance the asymmetrical perylene dyes. Herrin, 3 asymmetrical intermediates, including one perylene monoanhydride diester and two perylene monoimide diester dyes are synthesized in high yields and their brominations are presented firstly.
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by TLC, the solution was refluxed for 6 h. After being cooled to room temperature, the crude product was collected by filtration. Then the sample was purified by silica gel column chromatography with the eluent CHCl3 to give 1 (0.64 g, 80%) as a dark red solid. 1H NMR (CDCl3, 300 MHz, ppm): d (ppm) ¼ 8.67 (d, 2H, J ¼ 7.9 Hz), 8.55 (m, 4H), 8.16 (d, 2H, J ¼ 7.9 Hz), 4.93 (t, 4H), 1.83e1.76 (m, 4H), 1.54e1.47 (m, 4H), 1.03 (t, 6H). MS (MALDI-TOF): m/z ¼ 522.17 (Mþ).
2. Experimental 2.1. Materials All reagents and solvents were obtained from Sinopharm Chemical Reagent Co. Ltd with reagent grade quality and used as received. The purification and isolation of the products were performed by column chromatography on silica gel 60, mesh size 40e 63 mm or silica gel 100, mesh size 63e200 mm. The potassium salt and tetraesters of 3,4,9,10-perylene tetracarboxylic acid, perylene monoanhydride diester 1 were synthesized according to the literature procedure [22,35]. 2.2. Equipment 1
H NMR and 13C NMR spectra were recorded on Bruker 300 MHz spectrometers in CDCl3 at room temperature. All chemical shifts are quoted relative to TMS (d ¼ 0.0 ppm); d values are given in ppm and J values in Hz. Mass spectra were measured on a Bruker Maxis UHRTOF MS spectrometer. Electronic absorption spectra were measured on a Beijing Purkinje General Instrument Co. Ltd. TU-190 spectrophotometer. The photoluminescence spectra were recorded on a HITACHI FL-4500 spectrofluorometer. 2.3. Synthesis 2.3.1. Synthesis of potassium salt of 3,4,9,10-perylene tetracarboxylic acid (PTCTK) A mixture of 3,4,9,10-perylene tetracarboxylic acid bisanhydride (2 g, 5.1 mmol) in 25 ml aqueous solution of potassium hydroxide (0.9 mol/l) was stirred at reflux temperature for 3 h. The cooled aqueous solution was gradually added to a mixture of i-propanol and acetone (60 ml, 1:1 v/v). The precipitate was collected by filtration, washed with acetone, and dried in vacuum. PTCTK was obtained as a yellow solid and was used in next reaction without further purification. 2.3.2. Synthesis of tetrabutyl-perylene-3,4,9,10-tetracarbonylate (PTE) PTCTK (1.5 g, 2.58 mmol), n-bromobutane (6 ml), potassium carbonate (3.0 g, 21.74 mmol), tetrabutyl ammonium bromide (1.5 g, 4.66 mmol), catalyzed KI and 50 ml deionized water were stirred vigorously at reflux temperature for 15 h. The resulting mixture was cooled and extracted with dichloromethane (10 ml 3). Washed with water, the CH2Cl2 solution was dried with Na2SO4 overnight. Removing the solvent, a golden yellow solid (1.5 g, 89%) was obtained and then was dried in vacuum. 1H NMR (CDCl3, 300 MHz, ppm): d ¼ 8.26 (d, 4H, J ¼ 7.9 Hz), 8.03 (d, 4H, J ¼ 7.9 Hz), 4.35 (t, 8H), 1.79 (m, 8H), 1.51 (m, 8H), 1.01 (m, 12H). 13C NMR (75 MHz, CDCl3, ppm): d ¼ 168.51, 132.94, 130.42, 130.36, 128.92, 128.74, 121.34, 65.32, 30.65, 19.81, 13.80. MS (MALDI-TOF): m/z ¼ 652.30 (Mþ). 2.3.3. Synthesis of dibutyl-perylene-3,4-anhydride-9,10dicarbonylate (1) A 50 ml round-bottomed flask was charged with PTE (1 g, 1.52 mmol), p-toluenesulfonic acid monohydrate (pTsOH$H2O) (0.87 g, 4.56 mmol), 4 ml toluene and 20 ml n-heptane. Monitored
2.3.4. Synthesis of N-cyclohexyl-dibutyl-perylene-3,4dicarboximide-9,10-dicarbonylate (2) In a 25 ml single-necked flask, 1 (200 mg, 0.38 mmol), catalyzed zinc acetate and 10 ml cyclohexylamine were added. The mixture was refluxed for 20 h. The solvent was removed on the rotary evaporator. The crude product was purified by column chromatography on silica gel using CH2Cl2 as the eluent to afford 2 as a dark red solid (222 mg, 96%). 1H NMR (CDCl3, 300 MHz, ppm): d ¼ 8.52 (d, 2H, J ¼ 7.8 Hz), 8.31 (m, 4H), 8.07 (d, 2H, J ¼ 7.8 Hz), 5.10 (m, 1H), 4.39 (t, 4H), 2.65 (m, 2H), 1.95e1.79 (m, 10H), 1.55e1.47 (m, 6H), 1.04 (t, 6H). 13C NMR (75 MHz, CDCl3, ppm): d ¼ 168.23, 163.93, 134.98, 132.11, 131.78, 131.15, 130.25, 129.19, 129.04, 122.69, 122.35, 121.71, 65.53, 53.86, 30.62, 29.12, 26.57, 25.47, 19.25, 13.78. MS (MALDITOF): m/z ¼ 603.26 (Mþ). 2.3.5. Synthesis of dibutyl-perylene-3,4-dicarboximide-9,10dicarbonylate (3) 1 (200 mg, 0.38 mmol), ammonium acetate (146 mg, 1.9 mmol) and 10 ml quinoline were charged to a 25 ml vial. The vial was purged with Argon for 5 min and sealed. After that, it was heated to 120 C for 2 h. The reaction mixture was cooled to room temperature and then washed with water. The bright red solid was collected by centrifugation and dried in vacuum at 75 C overnight. The crude product was purified by column chromatography on silica gel using CH2CH2 as the eluent to afford 3 (158 mg, 85%) as a bright red solid. 1H NMR (CDCl3, 300 MHz, ppm): d ¼ 8.62 (m, 2H), 8.52 (m, 4H), 8.13 (m, 2H), 4.38 (t, 4H), 1.83e1.78 (m, 4H), 1.54e1.47 (m, 4H), 1.03e0.99 (t, 6H). 13C NMR (75 MHz, CDCl3, ppm): d ¼ 168.06, 163.12, 135.28, 131.77, 131.36, 130.70, 130.00, 128.74, 125.64, 122.50, 121.51, 121.43, 65.53, 30.64, 19.26, 13.80. MS (MALDI-TOF): m/z ¼ 521.18 (Mþ). 2.3.6. Synthesis of dibutyl-1(7)-Br-perylene-3,4-anhydride-9,10dicarbonylate (4) A mixture of 1 (100 mg, 0.19 mmol), Br2 (2 ml, 39 mmol), K2CO3 (500 mg, 3.62 mmol) and catalyzed I2 in 40 ml CHCl3 was refluxed for 30 h. The excess bromine was removed by adding aqueous Na2SO3. The organic layer was washed with water and then dried with Na2SO4. Removing the solvent, the crude product was purified by silica gel column chromatography with the eluent of 100:1 CH2Cl2/acetone to give an inseparable mixture of 4a and 4b (48 mg, 42%). 1H NMR (CDCl3, 300 MHz, ppm): d ¼ 9.55 (m, 1H), 8.91 (s, 1H 0.6), 8.70 (d, 1H 0.4, J ¼ 8.1 Hz), 8.67 (d, 1H 0.6, J ¼ 8.1 Hz), 8.48 (m, 2H), 8.39 (s, 1H 0.4), 8.18 (m, 2H), 4.39 (m, 4H), 1.86e1.76 (m, 4H), 1.54e1.44 (m, 4H), 1.04e0.99 (m, 6H). 13C NMR (75 MHz, CDCl3, ppm): d ¼ 167.92, 167.84, 159.71, 159.11, 140.61, 136.49, 136.34, 133.04, 132.69, 132.51, 130.89, 130.67, 130.57, 129.96, 129.30, 128.49, 128.43, 127.70, 124.20, 123.40, 123.13, 119.22, 117.89, 117.75, 66.03, 65.75, 30.59, 19.22, 13.74. MS (MALDI-TOF): m/z ¼ 600.08 (Mþ). 2.3.7. Synthesis of dibutyl-1,7-diBr-perylene-3,4-anhydride-9,10dicarbonylate (5) A mixture of 1 (100 mg, 0.19 mmol), Br2 (4 ml, 78 mmol), K2CO3 (500 mg, 3.62 mmol) and catalyzed I2 in 40 ml CHCl3 was refluxed for 18 h. The excess bromine was removed by adding aqueous Na2SO3. The organic layer was washed with water and then dried
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R. Wang et al. / Dyes and Pigments 98 (2013) 450e458
with Na2SO4. Removing the solvent, the crude product was purified by silica gel column chromatography with the eluent of 100:1 CH2Cl2/acetone to give compound 5 (65 mg, 50.5%). 1H NMR (CDCl3, 300 MHz, ppm): d ¼ 9.31 (m, 2H), 8.91 (s, 1H), 8.70 (d, 1H, J ¼ 8.1 Hz), 8.36 (s, 1H), 8.18 (d, 1H, J ¼ 7.9 Hz), 4.39 (m, 4H), 1.83e 1.81 (m, 4H), 1.57e1.47 (4H), 1.04 (m, 6H). 13C NMR (75 MHz, CDCl3, ppm): d ¼ 167.54, 166.67, 159.43, 159.11, 139.65, 136.85, 135.59, 135.10, 132.55, 132.21, 132.01, 130.20, 129.95, 129.13, 129.00, 128.58, 128.27, 126.92, 121.09, 119.25, 117.98, 117.87, 66.10, 65.87, 30.57, 30.54, 19.21, 19.18, 13.73. MS (MALDI-TOF): m/z ¼ 679.99 (Mþ). 2.3.8. Synthesis of N-cyclohexyl-dibutyl-1-Br-perylene-3,4dicarboximide-9,10-dicarbonylate (6) A mixture of 2 (100 mg, 0.17 mmol), Br2 (0.5 ml, 19 mmol), K2CO3 (500 mg, 3.62 mmol) and catalyzed I2 was added in 15 ml CHCl3. The reaction mixture was stirred at room temperature for 20 h. The excess bromine was removed by adding aqueous Na2SO3. The organic layer was washed with water and then dried with Na2SO4. Removing the solvent, the crude product was purified by silica gel column chromatography with the eluent of 5:1 CH2Cl2/petroleum ether to give a reddish orange solid 6 (66 mg, 58%). 1H NMR (CDCl3, 300 MHz, ppm): d ¼ 9.42 (d, 1H, J ¼ 8.2 Hz), 8.61 (s, 1H), 8.60 (d, 2H, J ¼ 8.3 Hz), 8.44 (d, 1H, J ¼ 8.3 Hz), 8.39 (d, 1H, J ¼ 8.2 Hz), 8.15 (m, 2H), 5.07 (m, 1H), 4.38 (m, 4H), 2.63 (m, 2H), 1.95e1.76 (m, 10H), 1.52e1.26 (m, 6H), 1.03e0.86 (m, 6H). 13C NMR (75 MHz, CDCl3, ppm): d ¼ 168.18, 168.06, 163.72, 162.92, 135.41, 134.71, 132.20, 132.01, 131.83, 131.44, 131.19, 130.79, 130.67, 129.94, 129.63, 128.55, 127.99, 127.31, 122.84, 122.46, 65.58, 65.35, 54.07, 42.00, 30.62, 30.14, 29.68, 29.06, 26.52, 25.42, 23.37, 23.06, 22.66, 19.24, 14.05, 13.76, 11.08. MS (MALDI-TOF): m/z ¼ 681.17 (Mþ). 2.3.9. Synthesis of N-cyclohexyl-dibutyl-1,7(6)-diBr-perylene-3,4dicarboximide-9,10-dicarbonylate (7) A mixture of 2 (100 mg, 0.17 mmol), Br2 (1 ml, 39 mmol), K2CO3 (500 mg, 3.62 mmol) and catalyzed I2 in 15 ml CHCl3 was stirred at reflux temperature for 10 h. The excess bromine was removed by adding aqueous Na2SO3. The organic layer was washed with water and then dried with Na2SO4. Removing the solvent, the crude product was purified by silica gel column chromatography with the eluent of 6:1 CH2Cl2/petroleum ether to give an inseparable mixture of 7a and 7b as a reddish orange solid (79 mg, 70%). 1H NMR (CDCl3, 300 MHz, ppm): d ¼ 9.23 (m, 2H), 8.67 (m, 2H), 8.16 (m, 2H), 5.04 (m, 1H), 4.38 (m, 4H), 2.58 (m, 2H), 1.94e1.61 (m, 10H), 1.49e1.26 (m, 6H), 1.03e0.98 (m, 6H). 13C NMR (75 MHz, CDCl3, ppm): d ¼ 168.00, 167.76, 166.97, 163.54, 163.02, 162.69, 134.51, 133.60, 132.19, 131.97, 131.77, 131.34, 131.12, 130.03, 129.15, 128.40, 128.24, 127.72, 122.87, 65.92, 65.69, 54.28, 54.12, 30.59, 29.66, 29.09, 26.51, 25.40, 19.22, 13.73. MS (MALDI-TOF): m/z ¼ 761.08 (Mþ). 2.3.10. Synthesis of N-cyclohexyl-dibutyl-1,7(6)-di-(4-tertbutylphenoxy)-perylene-3,4-dicarboximide-9,10-dicarbonylate (8) A mixture of 7 (42 mg, 0.05 mmol), 4-tert-butylphenol (75 mg, 0.5 mmol), K2CO3 (69 mg, 0.5 mmol) and catalyzed KI was added in 6 ml N-methylpyrrolidone (NMP). The reaction mixture was stirred for 7 h at 60 C under argon atmosphere. Then the cooled reaction mixture was added 50 ml solution of MeOH (10 ml) and 10% HCl. The precipitate was collected by filtration, washed with methanol, and then dried in vacuum. The crude product was purified by silica gel column chromatography with the eluent of 4:1 CH2Cl2/petroleum ether to give an inseparable mixture of 8a and 8b (38.2 mg, 85%). 1H NMR (CDCl3, 300 MHz, ppm): d ¼ 9.38 (m, 2H 0.7), 9.32 (d, 2H 0.3, J ¼ 8.2 Hz), 8.53 (d, 1H 0.7, J ¼ 8.4 Hz), 8.30 (s, 1H 0.7), 8.23 (s, 2H 0.3), 8.08 (d, 2H 0.3, J ¼ 8.3 Hz), 8.05 (d, 1H 0.7, J ¼ 8.3 Hz), 7.77 (s, 1H 0.7), 7.45e 7.41 (m, 4 H), 7.09e7.04 (m, 4H), 5.04 (m, 1H), 4.34e4.23 (m, 4H),
2.58e2.46 (m, 2H), 1.90e1.63 (m, 10H), 1.49e1.26 (m, 24H), 0.98e 0.88 (m, 6H). 13C NMR (75 MHz, CDCl3, ppm): d ¼ 168.45, 168.34, 167.60, 163.99, 163.61, 163.39, 154.99, 154.02, 153.81, 153.17, 153.05, 152.77, 147.63, 147.52, 133.70, 132.46, 132.06, 130.92, 130.80, 130.73, 130.67, 130.09, 129.98, 129.07, 128.16, 127.75, 127.13, 126.34, 125.01, 124.83, 124.74, 124.69, 124.36, 123.69, 123.28, 123.11, 121.68, 121.29, 118.80, 118.67, 114.74, 65.45, 65.34, 65.27, 53.97, 53.86, 34.45, 31.44, 30.63, 30.39, 29.67, 29.10, 26.52, 25.44, 19.22, 13.73, 13.67. MS (MALDI-TOF): m/z ¼ 899.44 (Mþ). 2.3.11. Synthesis of dibutyl-1(7)-Br-perylene-3,4-dicarboximide9,10-dicarbonylate (9) A mixture of 3 (200 mg, 0.38 mmol), Br2 (1 ml, 19 mmol), K2CO3 (500 mg, 3.62 mmol) and catalyzed I2 in 30 ml CHCl3 was refluxed for 30 h. The excess bromine was removed by adding aqueous Na2SO3. The organic layer was washed with water and then dried with Na2SO4. The crude product was purified by silica gel column chromatography with the eluent of 50:1 CH2Cl2/acetone to give an inseparable mixture of 9a and 9b (96 mg, 42%). 1H NMR (CDCl3, 300 MHz, ppm): d ¼ 9.41 (m, 1H), 8.82e8.74 (m, 2H), 8.61 (m, 1H), 8.39e8.36 (m, 2H), 8.12 (m, 2H), 4.37 (m, 4H), 1.81e1.79 (m, 4H), 1.52e1.50 (m, 4H), 1.04e0.99 (m, 6H). 13C NMR (75 MHz, CDCl3, ppm): d ¼ 167.99, 167.71, 167.42, 164.50, 162.40, 138.13, 136.44, 135.17, 132.37, 131.59, 130.89, 130.46, 129.71, 129.02, 128.81, 128.52, 123.92, 122.53, 121.80, 120.17, 71.86, 65.63, 30.61, 30.57, 30.07, 27.83, 19.23, 19.15, 13.75, 13.66. MS (MALDI-TOF): m/z ¼ 599.09 (Mþ). 2.3.12. Synthesis of dibutyl-1,7(6)-diBr-perylene-3,4dicarboximide-9,10-dicarbonylate (10) A mixture of 3 (100 mg, 0.19 mmol), Br2 (2 ml, 39 mmol), K2CO3 (500 mg, 3.62 mmol) and catalyzed I2 in 20 ml CHCl3 was refluxed for 15 h. The excess bromine was removed by adding aqueous Na2SO3. The organic layer was washed with water and then dried with Na2SO4. The crude product was purified by silica gel column chromatography with the eluent of 100:1 CH2Cl2/acetone to give an inseparable mixture of 10a and 10b (84 mg, 65%). 1H NMR (CDCl3, 300 MHz, ppm): d ¼ 9.46e9.36 (m, 1H), 8.83e8.70 (m, 1H), 8.63e 8.58 (m, 1.5H), 8.44e8.36 (m, 2H), 8.14e8.10 (m, 1.5H), 4.39e4.35 (m, 4H), 1.84e1.79 (m, 4H), 1.55e1.50 (m, 4H), 1.04e0.99 (m, 6H). 13 C NMR (75 MHz, CDCl3, ppm): d ¼ 167.96, 167.68, 166.80, 162.90, 162.38, 162.01, 137.69, 136.81, 134.16, 132.33, 131.87,130.66, 129.95, 128.98, 128.28, 127.86, 121.80, 121.26, 120.48, 119.29, 71.77, 65.78, 65.53, 30.56, 29.66, 27.71, 19.22, 19.12, 13.73, 13.67. MS (MALDITOF): m/z ¼ 679.00 (Mþ). 2.3.13. Synthesis of dibutyl-1-(4-tert-butylphenoxy)-perylene-3,4dicarboximide-9,10-dicarbonylate (11) and dibutyl-7-(4-tertbutylphenoxy)-perylene-3,4-dicarboximide-9,10-dicarbonylate (12) 9 (80 mg, 0.13 mmol), 4-tert-butylphenol (97 mg, 0.65 mmol), K2CO3 (90 mg, 0.65 mmol) and catalyzed KI were added in 10 ml NMP. The reaction mixture was stirred for 6 h at 60 C under argon atmosphere. Then MeOH (10 ml) and 10% HCl solution (50 ml) were added into the cooled reaction mixture. Then the precipitate was collected by filtration, washed with methanol, and dried in vacuum. The crude product was further purified by silica gel column chromatography with the eluent CH2Cl2/acetone (100:1 v/v) to give 11 (35 mg, 40%) and 12 (36 mg, 41%). Compound 11 1H NMR (CDCl3, 300 MHz, ppm): d ¼ 9.45 (d, 1H, J ¼ 8.3 Hz), 8.59 (m, 2H), 8.52 (m, 2H), 8.30 (s, 1H), 8.17 (d, 1H, J ¼ 7.7 Hz), 8.09 (d, 1H, J ¼ 8.3 Hz), 7.45 (d, 2H, J ¼ 7.0 Hz), 7.05 (d, 2H, J ¼ 7.0 Hz), 4.35 (m, 4H), 1.82e1.75 (m, 4H), 1.51e1.48 (m, 4H), 1.46e1.98 (m, 15H). 13C NMR (75 MHz, CDCl3, ppm): d ¼ 168.41, 163.23, 162.59, 154.69, 152.78, 147.91, 136.09, 131.90, 131.31, 130.97, 130.79, 129.86, 129.65, 128.67, 128.39, 127.40, 126.81, 125.14, 122.65, 122.51, 122.36, 121.59, 118.73, 65.56, 65.46, 34.51, 31.46, 30.62, 19.27, 13.80. MS (MALDI-TOF):
R. Wang et al. / Dyes and Pigments 98 (2013) 450e458
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Scheme 1. The synthesis of compounds 1e3. Reagents and conditions: (a) KOH, H2O, reflux, 100%; (b) n-bromobutane, potassium carbonate, TBAB, KI, H2O, reflux, 89%; (c) pTsOH$H2O, n-heptane/toluene (5:1), reflux, 80%; (d) zinc acetate, cyclohexylamine, reflux, 96%; (e) ammonium acetate, quinoline, 120 C, 85%.
m/z ¼ 699.27 (Mþ). Compound 12 1H NMR (CDCl3, 300 MHz, ppm): d ¼ 9.29 (m, 1H), 8.74 (d, 1H, J ¼ 10.4 Hz), 8.49e8.32 (m, 4H), 8.06 (d, 1H, J ¼ 6.9 Hz), 7.70 (s, 1H), 7.49 (d, 2H, J ¼ 8.6 Hz), 7.11 (d, 2H, J ¼ 8.6 Hz), 4.38 (t, 2H), 4.30 (t, 2H), 1.84e1.68 (m, 4H), 1.56e1.48 (m, 4H), 1.46e0.9 (m, 15H). 13C NMR (75 MHz, CDCl3, ppm): d ¼ 168.28, 167.38, 163.47, 163.21, 155.23, 152.27, 148.17, 136.23, 135.23, 133.13, 131.93, 131.88, 131.84, 131.16, 130.67, 130.28, 128.83, 127.35, 127.29, 127.10, 125.29, 124.04, 123.58, 121.63, 121.33, 121.04, 120.38, 119.20, 65.61, 65.58, 53.41, 34.53, 31.45, 30.63, 30.38, 29.70, 19.25, 19.10, 13.78, 13.70. MS (MALDI-TOF): m/z ¼ 699.27 (Mþ). 2.3.14. Synthesis of 1,7(6)-di-(4-tert-butylphenoxy)-perylene-3,4dicarboximide-9,10-dicarbonylate (13) 10 (150 mg, 0.22 mmol), 4-tert-butylphenol (330 mg, 2.2 mmol), K2CO3 (304 mg, 2.2 mmol) and catalyzed KI were added in 10 ml NMP. The reaction mixture was stirred for 6 h at 60 C under argon atmosphere. Then MeOH (10 ml) and 10% HCl solution (50 ml) were added into the cooled reaction mixture. The precipitate was collected by filtration, washed with methanol, and then dried in vacuum. The crude product was further purified by silica gel column chromatography with the eluent CH2Cl2/acetone (100:0.5 v/v) to give an inseparable mixture of 13a and 13b (142 mg, 79%). 1H NMR (CDCl3, 300 MHz, ppm): d ¼ 9.37e9.33 (m, 2H 0.5), 9.32 (d, 2H 0.5, J ¼ 8.3 Hz), 8.57 (d, 1H 0.5, J ¼ 8.3 Hz), 8.32 (s, 1H 0.5), 8.27 (s, 2H 0.5), 8.08 (d, 2H 0.5, J ¼ 8.3 Hz), 8.03 (d, 1H 0.5, J ¼ 8.3 Hz), 7.75 (s, 1H 0.5), 7.44e7.38 (m, 4H), 7.06e7.00 (m, 4H), 6.59 (s, 1H), 4.33 (m, 4H), 1.75e1.64 (m, 4H), 1.50e1.40 (m, 4H), 1.27e0.84 (m, 24H). 13C NMR (13, 75 MHz, CDCl3, ppm): d ¼ 168.27, 167.52, 163.20, 162.82, 154.17, 153.80, 153.17, 152.63, 147.84, 147.64, 134.70, 132.83, 131.98, 131.00, 130.57, 129.99, 129.01, 128.55, 127.64, 127.29, 127.19, 124.40, 123.48, 122.33, 120.76, 118.94, 118.56, 65.50, 65.41, 34.45, 31.43, 30.62, 30.37, 29.67, 19.22, 19.09, 13.73, 13.67. MS (MALDI-TOF): m/z ¼ 817.36 (Mþ).
3. Results and discussions 3.1. Synthesis The chemical structures of asymmetrical intermediates 1, 2 and 3 and their synthetic routes are shown in Scheme 1. The synthesis started from the hydrolysis of perylene bisanhydride in aqueous solution of KOH to afford tetrapotassium salt of 3,4,9,10-perylene tetracarboxylic acid (PTCTK). The salt was treated with n-bromobutane
Scheme 2. The synthesis of compounds 4 and 5. (f) Br2, I2, CHCl3, reflux, 42%; (g) Br2, I2, CHCl3, reflux, 50.5%.
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in presence of K2CO3 to obtain tetrabutyl perylene tetracarbonate (PTE). In mixed solvents of n-heptane and toluene, PTE was hydrolyzed by p-toluenesulfonic acid at one side to yield compound 1 as precipitate. Compounds 2 and 3 were synthesized by the imidization of 1 using cyclohexylamine and ammonium acetate respectively [35]. The brominations of 1, 2 and 3 are summarized in Schemes 2e4 respectively. PTCTK was obtained via hydrolysis of perylene bisanhydride in aqueous solution of potassium hydroxide. The resulting solution was dropwise added into a mixture of i-propanol and acetone (1:1 v/v) to yield PTCTK as precipitate in a high yield. With moderate reactivity, n-bromobutane was chosen to react with PTCTK to synthesis the ester in presence of K2CO3, which was used as base instead of usually used KOH [22]. Because KOH could also react with n-bromobutane in reaction to give hard removable butanol. The synthesis of compound 1 was a key step to achieve asymmetrical perylene intermediates. PTE is very sensitive to acid and can be converted to poorly soluble perylene monoanhydride and then to insoluble perylene dianhydride. However, if the less soluble intermediate 1 with one anhydride group can be precipitated from
the reaction solution, the formation of the second anhydride group will be prevented. n-Heptane is a straight-chain alkane with boiling point of 98 C, which is an appropriate temperature for the acidic hydrolysis of PTE [35]. Owing to its poor solubility, heptane needs to be mixed portion of good solvent to support enough solubility in reaction. Thus the mixed solvents of n-heptane and toluene (5:1 v/v) were used in the reaction. Besides proper the solvent system, the alkyl groups of the PTE also play important role in turning the solubility of the intermediate 1. In past works, long carbon chain such as decyl and lauryl groups were used in PTE for good solubility [35,36]. Long chain would enable the perylene monoanhydride diester partially resolved and result in the second acidic hydrolysis to form insoluble perylene dianhydride at last. Through comparison, butyl group was used herein to synthesize compound 1 in a satisfactory isolated yield (80%). This route is a very important and the most efficient method at present to synthesize the asymmetrical perylene derivatives. With an anhydride group, compound 1 can facilely react with various primary amines or ammonium salts to synthesize perylene monoimide diester dyes. Here cyclohexylamine and ammonium
Scheme 3. The synthesis of compounds 6e8. (h) Br2, I2, CHCl3, room temperature, 58%; (i) Br2, I2, CHCl3, room temperature, 70%; (j) 4-tert-Butylphenol, K2CO3, KI, NMP, 60 C, 85%.
R. Wang et al. / Dyes and Pigments 98 (2013) 450e458
Scheme 4. The synthesis of compounds 9e13. (k) Br2, I2, CHCl3, reflux, 42%; (l) Br2, I2, CHCl3, reflux, 65%; (m) 4-tert-butylphenol, K2CO3, KI, NMP, 60 C, 11 (40%), 12 (41%); (n) 4-tert-butylphenol, K2CO3, KI, NMP, 60 C, 79%.
acetate were used in reactions respectively to give intermediates 2 and 3. Similar with 1, various N-substituted perylene monoimide diester dyes could be prepared from intermediate 3 by its reactions with alkyl halides. Thus 3 typical asymmetrical intermediates of perylene monoimide diester were synthesized and their brominations were then investigated. The mono-bromination and dibromination of intermediates 1, 2 and 3 could be controlled by using different concentration of bromine. Chloroform was used as solvent in the reactions, instead of dichloromethane usually used in bromination of perylene derivatives, due to its better solubility and higher boiling point. Using a low concentration of bromine, 1 was brominated to mainly yield the mono-brominated product after purification with column chromatography, which was confirmed by MS spectrum. However, the 1H NMR and 13C NMR spectra of the sample showed two sets of signals in a definite ratio in the aromatic region, indicating that the sample was a couple of isomers. The chemical structures of the isomers were confirmed as 1-Br-1(4a) and 7-Br-1
455
(4b) [34,35,37]. According to the integration areas of the singlets at 8.91 ppm and 8.39 ppm in the 1H NMR spectrum, the isomers 4a and 4b were presented in a ratio about 1:0.6. 1 was fully brominated to yield di-brominated product 5 in higher concentration of bromine. 5 was confirmed with a unique structure of dibutyl-1,7-diBr-perylene-3,4-anhydride-9,10-dicarbonylate. The 1 H NMR spectrum of 5 showed characteristic signals of 1-Br- and 7Br-substituted 1 at 8.91 ppm and 8.36 ppm respectively, which was very similar with the mono-brominated isomers 4a and 4b. Carbon signals of two ester C]O and two imide C]O appeared at 167.54 ppm, 166.67 ppm and 159.43 ppm, 159.11 ppm respectively (Table 1) in 13C NMR spectrum, indicating the structure hadn’t any axis or center of symmetry. Compared with the mono-bromination of 1, the di-bromination was more facile to be controlled and was in higher yield. The di-bromination of 1 should be divided into two steps. The first step afforded isomer 4a and 4b in a ratio of 1:0.6. Then the second step of bromination took place only at opposite position of the first bromine atom at bay-area of the perylene core. The result was neither similar with the di-bromination of PBI, which resulted in isomers of 1,7- and 1,6-di-brominated PBI [38]; nor similar with the bromination of perylene bisanhydride, which resulted in a mixture of brominated compounds in different levels as well as the isomers of 1,7- and 1,6-diBr-perylene bisanhydride [39]. Therefore, the intermediate 1 was very useful in designing and synthesizing of disubstituted asymmetrical perylene dyes for its unique structure and high yield. The bromination degree of 2 was also controllable. Monobrominated product 6 was predominant when reaction was carried out in a low concentration of bromine. The interesting result was that the bromination took place only at 1-position of the intermediate 2. The signal of the doublet at 9.41 ppm and the singlet at 8.61 ppm were typical characteristic of 1-Br-perylene-3,4dicarboximide dyes. In 13C NMR spectrum, carbons of two ester C]O appeared at 168.18 ppm and 168.06 ppm respectively, while carbons of two imide C]O appeared at 163.72 ppm and 162.96 ppm respectively (Table 1). The larger difference of two imide C]O implied that the bromination took place near the imide group. Correspondingly the substituted bromine atom had less influence on two ester C]O at farer side. Therefore, 2 was an important intermediate to design and synthesize mono-substituted asymmetrical perylene dyes for its unique structure of monobrominated product. 7 was obtained as main product in the bromination of 2 in higher concentration of bromine. According to the MS data, the product was di-brominated 2. But the exact chemical structure could not be determined by the 1H NMR and 13C NMR spectra (Fig. 1). Therefore, a further reaction with 4-tert-butylphenol was performed. The reaction of phenol with brominated perylene derivative has been proven to be effective, and to be not selective toward brominated isomers. Generally the substitution of bromine atom by phenol took place at original position. The phenol disubstituted 2 was purified with column chromatography on silica gel. The presence of 3 singlets at 7.77 ppm, 8.23 ppm and 8.30 ppm in aromatic region of 1H NMR spectrum indicated that the phenol
Table 1 The chemical shifts of carbons in carbonyl groups for compounds 4e6, 8 and 11e13. Compound 4
d (ppm) (ester C]O) d (ppm) (imide C]O)
5
6
8
167.92, 167.54, 168.18, 168.45, 167.84 166.67 168.06 168.34, 167.60 159.71, 159.43, 163.72, 163.99, 159.11 159.11 162.92 163.61, 163.39
11
12
13
168.41, 168.28, 168.27, 168.28 167.38 167.52 163.23, 163.47, 163.20, 162.59 163.21 162.82
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Fig. 1. Low-field section of the 1H NMR spectra of 7 (a) and 8 (b).
Fig. 2. Low-field section of the 1H NMR spectra of 10 (a) and 13 (b).
di-substituted 2 was isomers. According to the ratio of the integration areas, the signals could be clearly divided into two sets. Two singlets at 7.77 ppm and 8.30 ppm were attributed to 1.7-di-4-tertbutylphenol substituted perylene derivative 8a. The last singlet 8.23 ppm should correspond to a symmetric structure. Combing the 13 C NMR spectrum, the isomer was with a 1.6-di-4-tert-butylphenol substituted structure of 8b. As shown in Fig. 1, the ratio of 8a and 8b for the phenol di-substituted isomers was determined as 1:0.45 according to integration areas of corresponding signals. Therefore, the ratio of 1,7-dibrominated isomer 7a and 1,6-dibrominated isomer 7b was supposed to be approximate 1:0.45. 3 could be mono-brominated and di-brominated in reactions by using different concentrations of bromine. The predominant product 9 was obtained in low concentration of bromine. While the predominant product 10 was obtained in high concentration of bromine. 9 and 10 were confirmed as mono-brominated and dibrominated products respectively by MS data. But the exact chemical structures of both samples couldn’t be confirmed by the 1 H NMR and 13C NMR spectra. Thus 9 and 10 were further reacted with 4-tert-butylphenol respectively. The main reaction products of 9 were separated by column chromatography on silica gel to afford 11 in 40% yield and 12 in 41% yield. According to some characteristic NMR data of 11, such as signet at 8.30 ppm in 1H NMR spectrum, carbons of two ester C]O at 168.41 ppm and 168.28 ppm and carbons of two imide C]O at 163.23 ppm and 162.59 ppm in the 13 C NMR spectrum, the substituted position should be near the imide group (Table 1). Thus the chemical structure of 11 was confirmed as dibutyl-1-(4-tert-butylphenoxy)-perylene-3,4dicarboximide-9,10-dicarbonylate. The characteristic NMR data of 12, such as signet at 7.70 ppm in 1H NMR spectrum, carbons of two ester C]O at 168.28 ppm and 167.38 ppm and carbons of the two imide C]O at 163.47 ppm and 163.21 ppm in the 13C NMR spectrum, indicated the substituted position closed to the ester groups. Namely the chemical structure of 12 was confirmed as dibutyl-7(4-tert-butylphenoxy)-perylene-3,4-dicarboximide-9,10dicarbonylate. Accordingly the mono-brominated product 9 should be a couple of isomers, including 1-Br-3 (9a) and 7-Br-3 (9b) with a deduced ratio about 1:1. The main product 13 was separated with column chromatography on silica gel from the reaction of 10 with 4-tert-butylphenol. 13 was proven to be a mixture of isomer 13a and isomer 13b with 1 H NMR (Fig. 2) and 13C NMR data (Table 1). The signals could be divided into two sets in aromatic region of 1H NMR spectrum of 13.
Three characteristic singlets were observed at 7.75 ppm, 8.27 ppm and 8.32 ppm respectively in the aromatic region. Among that, two singlets at 7.75 ppm and 8.32 ppm in ratio of 1:1 were attributed to 1,7-disubstituted 13a. The last one at 8.27 ppm was attributed to a symmetric structure of 1,6-disubstituted 13b. The integration areas of 3 singlets revealed that 13a and 13b were presented in a ratio about 1:1. Thus combining the former NMR data, the di-brominated 3 was presumed including 1,7-di-brominated isomer 10a and 1,6di-brominated isomer 10b with a deduced ratio about 1:1. The brominations of the 3 intermediates are summarized in Table 2. The mono-bromination and di-bromination of 3 typical intermediates could be controlled by using different concentration of bromine. Compound 1, with an anhydride group, was monobrominated to give inseparable 1-Br-1 (4a) and 7-Br-1 (4b) in ca. 1:0.6 ratio with a total yield of 42%. The di-brominated product was unique 1,7-diBr-1 (5). Incorporated with cyclohexyl group at imide group, the N-substituted compound 2 was mono-brominated to yield unique 1-Br-2 (6) in a yield of 58%. The di-brominated products were inseparable 1,7-diBr-2 (7a) and 1,6-diBr-2 (7b) in ratio of 1:0.45. The bromination of 3 was the most complicated case. Both the mono-bromination and the di-bromination afforded inseparable isomers. The isomers of mono-brominated 1(7)-Br-3 and di-brominated 1,7(6)-diBr-3 were finally presumed with a similar ratio of 1:1. In general, compound 1 is an ideal intermediate for synthesis of di-substituted asymmetrical perylene dyes, and compound 2 is a useful intermediate to synthesize mono-substituted asymmetrical perylene dyes. 3.2. Absorption and emission properties of dyes The UVevis absorption and emission spectra of corresponding compounds were measured in chloroform at room temperature. The data are summarized in Table 3. In order to compare the
Table 2 Summary of the bromination of 1e3. Compound
1 2 3
monoBr-
Ratio
1-Br-
7-Br-
4a 6 9a
4b e 9b
1:0.6 e 1:1
diBr-
Ratio
1,7-diBr-
1,6-diBr-
5 7a 10a
e 7b 10b
e 1:0.45 1:1
R. Wang et al. / Dyes and Pigments 98 (2013) 450e458
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Table 3 Absorption and emission data for PTE and 1e13 in chloroform (105 M). Compound
PTE
1
2
3
4
5
6
7
8
9
10
11
12
13
lmax (nm) lem (nm)
472 488
506 527
505 525
506 531
505 537
506 542
503 528
503 535
517 557
505 536
505 541
514 542
506 560
526 562
Fig. 3. UVevis absorption and emission spectra of PTE, compounds 1e5 in chloroform (105 M). Fig. 5. UVevis absorption and emission spectra of compounds 3 and 9e13 in chloroform (105 M).
location of peaks and shape, all absorption spectra were normalized. As shown in Fig. 3, PTE exhibits strong perylene core absorption band at 472 nm. Perylene monoanhydride diester 1 has a larger p-system than PTE, and shows a remarkable red-shift about 34 nm in absorption spectrum. After formation of imide structure whether introducing substitutes at the N atom (2) or not (3), however, the absorption change vary slight. The results indicate that the formation of imide group and incorporating other group at the N atom hardly change the electronic structure of perylene monoanhydride diester (1). The mono-brominated 1 (compound 4) and di-brominated 1 (compound 5) show the maximal absorption band at 505 nm and 506 nm respectively that are very similar with 1 (506 nm). Thereby the brominations of 1 lead to almost negligible change in absorption. Compared with the absorption spectra, the
emission spectra show relatively obvious change. The formation of imide group result in a 2 nm blue shift for 2 and a 2 nm red-shift for 3, and result in remarkable increase of intensity that maybe owing to the decrease of the pep stacking. The mono-bromination and dibromination of 1 lead to 10 nm and 15 nm red-shift respectively in emission spectra. Similar with compound 1, the bromination of 2 and 3 leads to slight changes in absorption and relatively obvious changes in emission (Figs. 4 and 5, Table 3). But the introduction of phenoxy groups results in obvious changes both in absorption and emission. Compared with 7, red-shifts about 14 and 22 nm in the absorption and emission for 8 are observed. The phenol di-substituted 13 results in a same 21 nm red-shift both in absorption and emission spectra compared with 10. The interesting result is that the separated isomers 11 and 12 exhibit quite different shapes and location of peaks both in absorption and emission spectra. The 1-phenolsubstituted 11 shows 9 nm red-shift in absorption spectra and 18 nm blue shift in emission spectra compared with the 7-phenolsubstituted 12. Therefore, the position of substituted group plays an important role in turning the absorption and emission of perylene monoimide diester. 4. Conclusions
Fig. 4. UVevis absorption and emission spectra of compounds 2 and 6e8 in chloroform (105 M).
In conclusion, a facile and effective synthesis of the asymmetrical intermediate of dibutyl-perylene-3,4-anhydride-9,10-di-carbonylate was developed using readily available tetraesters of perylene tetracarboxylic acids as starting materials. By choosing properly long carbon chain in ester group and proper solubility of a mixed solvent system, the less soluble perylene monoanhydride diester (1) formed in first step of acidic hydrolysis could be isolated from the reaction solution as precipitate to prevent the second acidic hydrolysis. Based on the intermediate, two other asymmetrical perylene intermediates 2 and 3 were designed and
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synthesized. The mono-bromination and di-bromination of 3 typical intermediates could be controlled by using different bromine concentration. The chemical structures of the brominated products were confirmed directly or deduced from the further phenol substituted products with MS and NMR spectra. Intermediate 1 was mono-brominated to give inseparable 1-Br-1 (4a) and 7-Br-1 (4b) in ca. 1:0.6 ratio with a total yield of 42%. Its dibrominated product was unique 1,7-diBr-1 (5) with a yield of 50.5%. Intermediate 2 was mono-brominated to yield unique 1-Br-2 (6) in a yield of 58%. The di-brominated 2 was inseparable isomers with indeterminable structures. The isomers were further reacted with 4-tert-butylphenol. Despite the phenol di-substituted isomers were still inseparable, their chemical structures and their ratio could be determined. Thus the structures of di-brominated 2 were confirmed as 1,7-diBr-2 (7a) and 1,6-diBr-2 (7b) in a deduced ratio of 1:0.45. Both the mono-brominated and di-brominated 3 were inseparable isomers of 9 and 10 with indeterminable structures. They were further reacted with 4-tert-butylphenol respectively. The main reaction products of 9 were separable 11 and 12 and the main products of 10 were inseparable isomer 13a and isomer 13b. Thus the mono-brominated and di-brominated 3 were confirmed as 1(7)-Br-3 (9a and 9b) and 1,7(6)-diBr-3 (10a and 10b) respectively with a same deduced ratio of 1:1. The intermediate 1 is useful for the synthesis of di-substituted asymmetrical dyes based on perylene, and intermediate 2 is useful for the synthesis of monosubstituted asymmetrical dyes base on perylene. Formation of imide group and bromination of the intermediates led to only slight changes in absorption spectra, but resulted in relatively obvious changes in emission spectra. Acknowledgment This work was supported by the Provincial Natural Science Foundation of Shandong (ZR2012BM012). Appendix A. Supplementary data Supplementary data related to this article can be found at http:// dx.doi.org/10.1016/j.dyepig.2013.04.006. References [1] Pasaogullari N, Icil H, Demuth M. Symmetrical and unsymmetrical perylene diimides: their synthesis, photophysical and electrochemical properties. Dyes Pigm 2006;69:118e27. [2] Tian H, Liu PH, Zhu WH, Gao EQ, Wu DJ, Cai SM. Synthesis of novel multichromophoric soluble perylene derivatives and their photosensitizing properties with wide spectral response for SnO2 nanoporous electrode. J Mater Chem 2000;10:2708e15. [3] He XR, Liu HB, Li YL, Wang S, Li YJ, Wang N, et al. Gold nanoparticle-based fluorometric and colorimetric sensing of copper (II) ions. Adv Mater 2005;17:2811e5. [4] Tan WJ, Li X, Zhang JJ, Tian H. A photochromic diarylethene dyad based on perylene diimide. Dyes Pigm 2011;89:260e5. [5] Yilmaz MD, Bozdemir OA, Akkaya EU. Light harvesting and efficient energy transfer in a boron-dipyrrin (BODIPY) functionalized perylenediimide derivative. Org Lett 2006;8:2871e3. [6] Zhao CT, Zhang YX, Li RJ, Li XY, Jiang JZ. Di(alkoxy)- and di(alkylthio)substituted perylene-3,4;9,10-tetracarboxy diimides with tunable electrochemical and photophysical properties. J Org Chem 2007;72:2402e10. [7] Zagranyarski Y, Chen L, Zhao Y, Wonneberger H, Li C, Müllen K. Facile transformation of perylene tetracarboxylic acid dianhydride into strong donore acceptor chromophores. Org Lett 2012;14:5444e7. [8] Li Y, Tan L, Wang ZH, Qian H, Shi Y, Hu WP. Air-stable n-type semiconductor: core-perfluoroalkylated perylene bisimides. Org Lett 2008;10:529e32. [9] Huang C, Barlow S, Marder SR. Perylene-3,4:9,10-tetracarboxylic acid diimides: synthesis, physical properties, and use in organic electronics. J Org Chem 2011;76:2386e407.
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[31] Kohl C, Weil T, Qu J, Müllen K. Towards highly fluorescent and water-soluble perylene dyes. Chem Eur J 2004;10:5297e310. [32] Avlasevich Y, Li C, Müllen K. Synthesis and applications of core-enlarged perylene dyes. J Mater Chem 2010;20:3814e26. [33] Li Y, Wang C, Li C, Motta SD, Negri F, Wang Z. Synthesis and properties of ethylene-annulated di(perylene diimides). Org Lett 2012;14:5278e81. [34] Dinçalp H, Kızılok S¸, Içli S. Fluorescent macromolecular perylene diimides containing pyrene or indole units in bay positions. Dyes Pigm 2010;86:32e41. [35] Xue C, Sun R, Annab R, Abadi D, Jin S. Perylene monoanhydride diester: a versatile intermediate for the synthesis of unsymmetrically substituted perylene tetracarboxylic derivatives. Tetrahedron Lett 2009;50:853e6. [36] Wicklein A, Muth MA, Thelakkat M. Room temperature liquid crystalline perylene diester benzimidazoles with extended absorption. J Mater Chem 2010;20:8646e52. [37] Yuan ZY, Li J, Xiao Y, Li Z, Qian XH. Core-perfluoroalkylated perylene diimides and naphthalene diimides: versatile synthesis, solubility, electrochemistry, and optical properties. J Org Chem 2010;75:3007e16. [38] Handa NV, Mendoza KD, Shirtcliff LD. Syntheses and properties of 1,6 and 1,7 perylene diimides and tetracarboxylic dianhydrides. Org Lett 2011;13:4724e7. [39] Fan LQ, Xu YP, Tian H. 1,6-Disubstituted perylene bisimides: concise synthesis characterization as near-infrared fluorescent dyes. Tetrahedron Lett 2005;46: 4443e7.
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Dyes and Pigments journal homepage: www.elsevier.com/locate/dyepig
Facile synthesis and controllable bromination of asymmetrical intermediates of perylene monoanhydride/monoimide diester Rongzhou Wang, Zhiqiang Shi*, Cuicui Zhang, Andong Zhang, Jiao Chen, Weiwei Guo, Zhaozhen Sun Department of Chemistry, Shandong Normal University, Jinan 250014, PR China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 20 February 2013 Received in revised form 4 April 2013 Accepted 6 April 2013 Available online 15 April 2013
Dibutyl-perylene-3,4-anhydride-9,10-dicarbonylate (1) as an asymmetrical intermediate was synthesized in 80% yield by precipitation of the less soluble target molecule, which was formed through acidic hydrolysis of tetraesters of perylene tetracarboxylic acids at one side in a mixed solvent system. Based on the intermediate, two other asymmetrical intermediates 2 and 3 with monoimide group were also synthesized in high yields. The mono-bromination and di-bromination of 3 typical intermediates could be controlled by using different bromine concentration. The chemical structures of the brominated products and ratios of their isomers were confirmed directly or deduced from their phenol substituted products with MS and NMR spectra. The bromination of the intermediates mainly afforded isomers, but intermediates 1 and 2 could afford unique di-brominated product and mono-brominated product respectively. The bromination of the intermediates led to only slight changes in absorption spectra, but relatively obvious changes in emission spectra. Ó 2013 Elsevier Ltd. All rights reserved.
Keywords: Dye Asymmetrical intermediate Perylene monoanhydride/monoimide diester Bromination Isomers Photophysical property
1. Introduction In recent years, perylene dyes have received much attention due to their electron acceptor ability, high fluorescence quantum yield, semiconducting and photoconducting properties [1e8], and therefore they have been extensively utilized for various applications such as field effect transistors, organic light-emitting diodes, organic solar cells, optical switches, sensors, liquid crystals, and so forth [9e 17]. Among the perylene dyes, perylene tetracarboxylic bisimide (PBI) dyes represent a classical example of an inherently robust and outstandingly versatile family of perylene dyes [18e21]. Compared with PBIs, the tetraesters of perylene tetracarboxylic acids (PTE) were highly soluble in common organic solvents by introduction of four flexible alkyl chains [22]. However, the single site reaction of both PBI and PTE was hard to be controlled because their reactions symmetrically took place in most of the cases and the products usually continued to be with symmetrical structures. Asymmetrical structure sometime is very useful in novel electron or energy donoreacceptor dyads designing, molecular recognition and other
* Corresponding author. Tel.: þ86 531 86182540; fax: þ86 531 82615258. E-mail addresses: [email protected], [email protected] (Z. Shi). 0143-7208/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.dyepig.2013.04.006
special applications. Perylene-monoimide (PMI) has been a useful intermediate for designing of asymmetrical perylene dyes. But due to its low yield, the synthetic chemistry of PMI dyes has developed slowly over the past years [23e25]. Perylene monoanhydride diester is also an asymmetrical intermediate [26]. Compared with PBI and PMI, Perylene monoanhydride diester is better soluble and more versatile. Through the anhydride group, various asymmetrical N-substituted perylene dyes can be readily accessed via formation of the imide. The diester groups enable the dyes good solubility, and also may be facilely transformed to the second anhydride group via acidic hydrolysis [26]. The second anhydride group can either be cut to prepare PMI in refluxed quinoline in presence of Cu2O [27], or be introduced different N-substituted groups to form new asymmetrical PBIs with high yields [5]. Besides introducing substitutes at the imide group [28], another important strategy to modify the perylene dyes was introducing substituents at the carbocyclic scaffold in the so-called bay-area of the perylene core [29e33]. The later strategy was more elaborate. For example, aryloxy-, cyano-, pyrrolidino, alkoxy and/or alkylthiosubstituted PBIs as well as the Suzuki coupling reaction of PBI have been extensively investigated. Usually the readily accessed halogenated PBIs, especially diBr-PBIs were used as starting materials [34]. Therefore, the bromination of the asymmetrical intermediate
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will be the crucial step in further modification of the asymmetrical perylene dyes at bay positions in order to development and abundance the asymmetrical perylene dyes. Herrin, 3 asymmetrical intermediates, including one perylene monoanhydride diester and two perylene monoimide diester dyes are synthesized in high yields and their brominations are presented firstly.
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by TLC, the solution was refluxed for 6 h. After being cooled to room temperature, the crude product was collected by filtration. Then the sample was purified by silica gel column chromatography with the eluent CHCl3 to give 1 (0.64 g, 80%) as a dark red solid. 1H NMR (CDCl3, 300 MHz, ppm): d (ppm) ¼ 8.67 (d, 2H, J ¼ 7.9 Hz), 8.55 (m, 4H), 8.16 (d, 2H, J ¼ 7.9 Hz), 4.93 (t, 4H), 1.83e1.76 (m, 4H), 1.54e1.47 (m, 4H), 1.03 (t, 6H). MS (MALDI-TOF): m/z ¼ 522.17 (Mþ).
2. Experimental 2.1. Materials All reagents and solvents were obtained from Sinopharm Chemical Reagent Co. Ltd with reagent grade quality and used as received. The purification and isolation of the products were performed by column chromatography on silica gel 60, mesh size 40e 63 mm or silica gel 100, mesh size 63e200 mm. The potassium salt and tetraesters of 3,4,9,10-perylene tetracarboxylic acid, perylene monoanhydride diester 1 were synthesized according to the literature procedure [22,35]. 2.2. Equipment 1
H NMR and 13C NMR spectra were recorded on Bruker 300 MHz spectrometers in CDCl3 at room temperature. All chemical shifts are quoted relative to TMS (d ¼ 0.0 ppm); d values are given in ppm and J values in Hz. Mass spectra were measured on a Bruker Maxis UHRTOF MS spectrometer. Electronic absorption spectra were measured on a Beijing Purkinje General Instrument Co. Ltd. TU-190 spectrophotometer. The photoluminescence spectra were recorded on a HITACHI FL-4500 spectrofluorometer. 2.3. Synthesis 2.3.1. Synthesis of potassium salt of 3,4,9,10-perylene tetracarboxylic acid (PTCTK) A mixture of 3,4,9,10-perylene tetracarboxylic acid bisanhydride (2 g, 5.1 mmol) in 25 ml aqueous solution of potassium hydroxide (0.9 mol/l) was stirred at reflux temperature for 3 h. The cooled aqueous solution was gradually added to a mixture of i-propanol and acetone (60 ml, 1:1 v/v). The precipitate was collected by filtration, washed with acetone, and dried in vacuum. PTCTK was obtained as a yellow solid and was used in next reaction without further purification. 2.3.2. Synthesis of tetrabutyl-perylene-3,4,9,10-tetracarbonylate (PTE) PTCTK (1.5 g, 2.58 mmol), n-bromobutane (6 ml), potassium carbonate (3.0 g, 21.74 mmol), tetrabutyl ammonium bromide (1.5 g, 4.66 mmol), catalyzed KI and 50 ml deionized water were stirred vigorously at reflux temperature for 15 h. The resulting mixture was cooled and extracted with dichloromethane (10 ml 3). Washed with water, the CH2Cl2 solution was dried with Na2SO4 overnight. Removing the solvent, a golden yellow solid (1.5 g, 89%) was obtained and then was dried in vacuum. 1H NMR (CDCl3, 300 MHz, ppm): d ¼ 8.26 (d, 4H, J ¼ 7.9 Hz), 8.03 (d, 4H, J ¼ 7.9 Hz), 4.35 (t, 8H), 1.79 (m, 8H), 1.51 (m, 8H), 1.01 (m, 12H). 13C NMR (75 MHz, CDCl3, ppm): d ¼ 168.51, 132.94, 130.42, 130.36, 128.92, 128.74, 121.34, 65.32, 30.65, 19.81, 13.80. MS (MALDI-TOF): m/z ¼ 652.30 (Mþ). 2.3.3. Synthesis of dibutyl-perylene-3,4-anhydride-9,10dicarbonylate (1) A 50 ml round-bottomed flask was charged with PTE (1 g, 1.52 mmol), p-toluenesulfonic acid monohydrate (pTsOH$H2O) (0.87 g, 4.56 mmol), 4 ml toluene and 20 ml n-heptane. Monitored
2.3.4. Synthesis of N-cyclohexyl-dibutyl-perylene-3,4dicarboximide-9,10-dicarbonylate (2) In a 25 ml single-necked flask, 1 (200 mg, 0.38 mmol), catalyzed zinc acetate and 10 ml cyclohexylamine were added. The mixture was refluxed for 20 h. The solvent was removed on the rotary evaporator. The crude product was purified by column chromatography on silica gel using CH2Cl2 as the eluent to afford 2 as a dark red solid (222 mg, 96%). 1H NMR (CDCl3, 300 MHz, ppm): d ¼ 8.52 (d, 2H, J ¼ 7.8 Hz), 8.31 (m, 4H), 8.07 (d, 2H, J ¼ 7.8 Hz), 5.10 (m, 1H), 4.39 (t, 4H), 2.65 (m, 2H), 1.95e1.79 (m, 10H), 1.55e1.47 (m, 6H), 1.04 (t, 6H). 13C NMR (75 MHz, CDCl3, ppm): d ¼ 168.23, 163.93, 134.98, 132.11, 131.78, 131.15, 130.25, 129.19, 129.04, 122.69, 122.35, 121.71, 65.53, 53.86, 30.62, 29.12, 26.57, 25.47, 19.25, 13.78. MS (MALDITOF): m/z ¼ 603.26 (Mþ). 2.3.5. Synthesis of dibutyl-perylene-3,4-dicarboximide-9,10dicarbonylate (3) 1 (200 mg, 0.38 mmol), ammonium acetate (146 mg, 1.9 mmol) and 10 ml quinoline were charged to a 25 ml vial. The vial was purged with Argon for 5 min and sealed. After that, it was heated to 120 C for 2 h. The reaction mixture was cooled to room temperature and then washed with water. The bright red solid was collected by centrifugation and dried in vacuum at 75 C overnight. The crude product was purified by column chromatography on silica gel using CH2CH2 as the eluent to afford 3 (158 mg, 85%) as a bright red solid. 1H NMR (CDCl3, 300 MHz, ppm): d ¼ 8.62 (m, 2H), 8.52 (m, 4H), 8.13 (m, 2H), 4.38 (t, 4H), 1.83e1.78 (m, 4H), 1.54e1.47 (m, 4H), 1.03e0.99 (t, 6H). 13C NMR (75 MHz, CDCl3, ppm): d ¼ 168.06, 163.12, 135.28, 131.77, 131.36, 130.70, 130.00, 128.74, 125.64, 122.50, 121.51, 121.43, 65.53, 30.64, 19.26, 13.80. MS (MALDI-TOF): m/z ¼ 521.18 (Mþ). 2.3.6. Synthesis of dibutyl-1(7)-Br-perylene-3,4-anhydride-9,10dicarbonylate (4) A mixture of 1 (100 mg, 0.19 mmol), Br2 (2 ml, 39 mmol), K2CO3 (500 mg, 3.62 mmol) and catalyzed I2 in 40 ml CHCl3 was refluxed for 30 h. The excess bromine was removed by adding aqueous Na2SO3. The organic layer was washed with water and then dried with Na2SO4. Removing the solvent, the crude product was purified by silica gel column chromatography with the eluent of 100:1 CH2Cl2/acetone to give an inseparable mixture of 4a and 4b (48 mg, 42%). 1H NMR (CDCl3, 300 MHz, ppm): d ¼ 9.55 (m, 1H), 8.91 (s, 1H 0.6), 8.70 (d, 1H 0.4, J ¼ 8.1 Hz), 8.67 (d, 1H 0.6, J ¼ 8.1 Hz), 8.48 (m, 2H), 8.39 (s, 1H 0.4), 8.18 (m, 2H), 4.39 (m, 4H), 1.86e1.76 (m, 4H), 1.54e1.44 (m, 4H), 1.04e0.99 (m, 6H). 13C NMR (75 MHz, CDCl3, ppm): d ¼ 167.92, 167.84, 159.71, 159.11, 140.61, 136.49, 136.34, 133.04, 132.69, 132.51, 130.89, 130.67, 130.57, 129.96, 129.30, 128.49, 128.43, 127.70, 124.20, 123.40, 123.13, 119.22, 117.89, 117.75, 66.03, 65.75, 30.59, 19.22, 13.74. MS (MALDI-TOF): m/z ¼ 600.08 (Mþ). 2.3.7. Synthesis of dibutyl-1,7-diBr-perylene-3,4-anhydride-9,10dicarbonylate (5) A mixture of 1 (100 mg, 0.19 mmol), Br2 (4 ml, 78 mmol), K2CO3 (500 mg, 3.62 mmol) and catalyzed I2 in 40 ml CHCl3 was refluxed for 18 h. The excess bromine was removed by adding aqueous Na2SO3. The organic layer was washed with water and then dried
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with Na2SO4. Removing the solvent, the crude product was purified by silica gel column chromatography with the eluent of 100:1 CH2Cl2/acetone to give compound 5 (65 mg, 50.5%). 1H NMR (CDCl3, 300 MHz, ppm): d ¼ 9.31 (m, 2H), 8.91 (s, 1H), 8.70 (d, 1H, J ¼ 8.1 Hz), 8.36 (s, 1H), 8.18 (d, 1H, J ¼ 7.9 Hz), 4.39 (m, 4H), 1.83e 1.81 (m, 4H), 1.57e1.47 (4H), 1.04 (m, 6H). 13C NMR (75 MHz, CDCl3, ppm): d ¼ 167.54, 166.67, 159.43, 159.11, 139.65, 136.85, 135.59, 135.10, 132.55, 132.21, 132.01, 130.20, 129.95, 129.13, 129.00, 128.58, 128.27, 126.92, 121.09, 119.25, 117.98, 117.87, 66.10, 65.87, 30.57, 30.54, 19.21, 19.18, 13.73. MS (MALDI-TOF): m/z ¼ 679.99 (Mþ). 2.3.8. Synthesis of N-cyclohexyl-dibutyl-1-Br-perylene-3,4dicarboximide-9,10-dicarbonylate (6) A mixture of 2 (100 mg, 0.17 mmol), Br2 (0.5 ml, 19 mmol), K2CO3 (500 mg, 3.62 mmol) and catalyzed I2 was added in 15 ml CHCl3. The reaction mixture was stirred at room temperature for 20 h. The excess bromine was removed by adding aqueous Na2SO3. The organic layer was washed with water and then dried with Na2SO4. Removing the solvent, the crude product was purified by silica gel column chromatography with the eluent of 5:1 CH2Cl2/petroleum ether to give a reddish orange solid 6 (66 mg, 58%). 1H NMR (CDCl3, 300 MHz, ppm): d ¼ 9.42 (d, 1H, J ¼ 8.2 Hz), 8.61 (s, 1H), 8.60 (d, 2H, J ¼ 8.3 Hz), 8.44 (d, 1H, J ¼ 8.3 Hz), 8.39 (d, 1H, J ¼ 8.2 Hz), 8.15 (m, 2H), 5.07 (m, 1H), 4.38 (m, 4H), 2.63 (m, 2H), 1.95e1.76 (m, 10H), 1.52e1.26 (m, 6H), 1.03e0.86 (m, 6H). 13C NMR (75 MHz, CDCl3, ppm): d ¼ 168.18, 168.06, 163.72, 162.92, 135.41, 134.71, 132.20, 132.01, 131.83, 131.44, 131.19, 130.79, 130.67, 129.94, 129.63, 128.55, 127.99, 127.31, 122.84, 122.46, 65.58, 65.35, 54.07, 42.00, 30.62, 30.14, 29.68, 29.06, 26.52, 25.42, 23.37, 23.06, 22.66, 19.24, 14.05, 13.76, 11.08. MS (MALDI-TOF): m/z ¼ 681.17 (Mþ). 2.3.9. Synthesis of N-cyclohexyl-dibutyl-1,7(6)-diBr-perylene-3,4dicarboximide-9,10-dicarbonylate (7) A mixture of 2 (100 mg, 0.17 mmol), Br2 (1 ml, 39 mmol), K2CO3 (500 mg, 3.62 mmol) and catalyzed I2 in 15 ml CHCl3 was stirred at reflux temperature for 10 h. The excess bromine was removed by adding aqueous Na2SO3. The organic layer was washed with water and then dried with Na2SO4. Removing the solvent, the crude product was purified by silica gel column chromatography with the eluent of 6:1 CH2Cl2/petroleum ether to give an inseparable mixture of 7a and 7b as a reddish orange solid (79 mg, 70%). 1H NMR (CDCl3, 300 MHz, ppm): d ¼ 9.23 (m, 2H), 8.67 (m, 2H), 8.16 (m, 2H), 5.04 (m, 1H), 4.38 (m, 4H), 2.58 (m, 2H), 1.94e1.61 (m, 10H), 1.49e1.26 (m, 6H), 1.03e0.98 (m, 6H). 13C NMR (75 MHz, CDCl3, ppm): d ¼ 168.00, 167.76, 166.97, 163.54, 163.02, 162.69, 134.51, 133.60, 132.19, 131.97, 131.77, 131.34, 131.12, 130.03, 129.15, 128.40, 128.24, 127.72, 122.87, 65.92, 65.69, 54.28, 54.12, 30.59, 29.66, 29.09, 26.51, 25.40, 19.22, 13.73. MS (MALDI-TOF): m/z ¼ 761.08 (Mþ). 2.3.10. Synthesis of N-cyclohexyl-dibutyl-1,7(6)-di-(4-tertbutylphenoxy)-perylene-3,4-dicarboximide-9,10-dicarbonylate (8) A mixture of 7 (42 mg, 0.05 mmol), 4-tert-butylphenol (75 mg, 0.5 mmol), K2CO3 (69 mg, 0.5 mmol) and catalyzed KI was added in 6 ml N-methylpyrrolidone (NMP). The reaction mixture was stirred for 7 h at 60 C under argon atmosphere. Then the cooled reaction mixture was added 50 ml solution of MeOH (10 ml) and 10% HCl. The precipitate was collected by filtration, washed with methanol, and then dried in vacuum. The crude product was purified by silica gel column chromatography with the eluent of 4:1 CH2Cl2/petroleum ether to give an inseparable mixture of 8a and 8b (38.2 mg, 85%). 1H NMR (CDCl3, 300 MHz, ppm): d ¼ 9.38 (m, 2H 0.7), 9.32 (d, 2H 0.3, J ¼ 8.2 Hz), 8.53 (d, 1H 0.7, J ¼ 8.4 Hz), 8.30 (s, 1H 0.7), 8.23 (s, 2H 0.3), 8.08 (d, 2H 0.3, J ¼ 8.3 Hz), 8.05 (d, 1H 0.7, J ¼ 8.3 Hz), 7.77 (s, 1H 0.7), 7.45e 7.41 (m, 4 H), 7.09e7.04 (m, 4H), 5.04 (m, 1H), 4.34e4.23 (m, 4H),
2.58e2.46 (m, 2H), 1.90e1.63 (m, 10H), 1.49e1.26 (m, 24H), 0.98e 0.88 (m, 6H). 13C NMR (75 MHz, CDCl3, ppm): d ¼ 168.45, 168.34, 167.60, 163.99, 163.61, 163.39, 154.99, 154.02, 153.81, 153.17, 153.05, 152.77, 147.63, 147.52, 133.70, 132.46, 132.06, 130.92, 130.80, 130.73, 130.67, 130.09, 129.98, 129.07, 128.16, 127.75, 127.13, 126.34, 125.01, 124.83, 124.74, 124.69, 124.36, 123.69, 123.28, 123.11, 121.68, 121.29, 118.80, 118.67, 114.74, 65.45, 65.34, 65.27, 53.97, 53.86, 34.45, 31.44, 30.63, 30.39, 29.67, 29.10, 26.52, 25.44, 19.22, 13.73, 13.67. MS (MALDI-TOF): m/z ¼ 899.44 (Mþ). 2.3.11. Synthesis of dibutyl-1(7)-Br-perylene-3,4-dicarboximide9,10-dicarbonylate (9) A mixture of 3 (200 mg, 0.38 mmol), Br2 (1 ml, 19 mmol), K2CO3 (500 mg, 3.62 mmol) and catalyzed I2 in 30 ml CHCl3 was refluxed for 30 h. The excess bromine was removed by adding aqueous Na2SO3. The organic layer was washed with water and then dried with Na2SO4. The crude product was purified by silica gel column chromatography with the eluent of 50:1 CH2Cl2/acetone to give an inseparable mixture of 9a and 9b (96 mg, 42%). 1H NMR (CDCl3, 300 MHz, ppm): d ¼ 9.41 (m, 1H), 8.82e8.74 (m, 2H), 8.61 (m, 1H), 8.39e8.36 (m, 2H), 8.12 (m, 2H), 4.37 (m, 4H), 1.81e1.79 (m, 4H), 1.52e1.50 (m, 4H), 1.04e0.99 (m, 6H). 13C NMR (75 MHz, CDCl3, ppm): d ¼ 167.99, 167.71, 167.42, 164.50, 162.40, 138.13, 136.44, 135.17, 132.37, 131.59, 130.89, 130.46, 129.71, 129.02, 128.81, 128.52, 123.92, 122.53, 121.80, 120.17, 71.86, 65.63, 30.61, 30.57, 30.07, 27.83, 19.23, 19.15, 13.75, 13.66. MS (MALDI-TOF): m/z ¼ 599.09 (Mþ). 2.3.12. Synthesis of dibutyl-1,7(6)-diBr-perylene-3,4dicarboximide-9,10-dicarbonylate (10) A mixture of 3 (100 mg, 0.19 mmol), Br2 (2 ml, 39 mmol), K2CO3 (500 mg, 3.62 mmol) and catalyzed I2 in 20 ml CHCl3 was refluxed for 15 h. The excess bromine was removed by adding aqueous Na2SO3. The organic layer was washed with water and then dried with Na2SO4. The crude product was purified by silica gel column chromatography with the eluent of 100:1 CH2Cl2/acetone to give an inseparable mixture of 10a and 10b (84 mg, 65%). 1H NMR (CDCl3, 300 MHz, ppm): d ¼ 9.46e9.36 (m, 1H), 8.83e8.70 (m, 1H), 8.63e 8.58 (m, 1.5H), 8.44e8.36 (m, 2H), 8.14e8.10 (m, 1.5H), 4.39e4.35 (m, 4H), 1.84e1.79 (m, 4H), 1.55e1.50 (m, 4H), 1.04e0.99 (m, 6H). 13 C NMR (75 MHz, CDCl3, ppm): d ¼ 167.96, 167.68, 166.80, 162.90, 162.38, 162.01, 137.69, 136.81, 134.16, 132.33, 131.87,130.66, 129.95, 128.98, 128.28, 127.86, 121.80, 121.26, 120.48, 119.29, 71.77, 65.78, 65.53, 30.56, 29.66, 27.71, 19.22, 19.12, 13.73, 13.67. MS (MALDITOF): m/z ¼ 679.00 (Mþ). 2.3.13. Synthesis of dibutyl-1-(4-tert-butylphenoxy)-perylene-3,4dicarboximide-9,10-dicarbonylate (11) and dibutyl-7-(4-tertbutylphenoxy)-perylene-3,4-dicarboximide-9,10-dicarbonylate (12) 9 (80 mg, 0.13 mmol), 4-tert-butylphenol (97 mg, 0.65 mmol), K2CO3 (90 mg, 0.65 mmol) and catalyzed KI were added in 10 ml NMP. The reaction mixture was stirred for 6 h at 60 C under argon atmosphere. Then MeOH (10 ml) and 10% HCl solution (50 ml) were added into the cooled reaction mixture. Then the precipitate was collected by filtration, washed with methanol, and dried in vacuum. The crude product was further purified by silica gel column chromatography with the eluent CH2Cl2/acetone (100:1 v/v) to give 11 (35 mg, 40%) and 12 (36 mg, 41%). Compound 11 1H NMR (CDCl3, 300 MHz, ppm): d ¼ 9.45 (d, 1H, J ¼ 8.3 Hz), 8.59 (m, 2H), 8.52 (m, 2H), 8.30 (s, 1H), 8.17 (d, 1H, J ¼ 7.7 Hz), 8.09 (d, 1H, J ¼ 8.3 Hz), 7.45 (d, 2H, J ¼ 7.0 Hz), 7.05 (d, 2H, J ¼ 7.0 Hz), 4.35 (m, 4H), 1.82e1.75 (m, 4H), 1.51e1.48 (m, 4H), 1.46e1.98 (m, 15H). 13C NMR (75 MHz, CDCl3, ppm): d ¼ 168.41, 163.23, 162.59, 154.69, 152.78, 147.91, 136.09, 131.90, 131.31, 130.97, 130.79, 129.86, 129.65, 128.67, 128.39, 127.40, 126.81, 125.14, 122.65, 122.51, 122.36, 121.59, 118.73, 65.56, 65.46, 34.51, 31.46, 30.62, 19.27, 13.80. MS (MALDI-TOF):
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Scheme 1. The synthesis of compounds 1e3. Reagents and conditions: (a) KOH, H2O, reflux, 100%; (b) n-bromobutane, potassium carbonate, TBAB, KI, H2O, reflux, 89%; (c) pTsOH$H2O, n-heptane/toluene (5:1), reflux, 80%; (d) zinc acetate, cyclohexylamine, reflux, 96%; (e) ammonium acetate, quinoline, 120 C, 85%.
m/z ¼ 699.27 (Mþ). Compound 12 1H NMR (CDCl3, 300 MHz, ppm): d ¼ 9.29 (m, 1H), 8.74 (d, 1H, J ¼ 10.4 Hz), 8.49e8.32 (m, 4H), 8.06 (d, 1H, J ¼ 6.9 Hz), 7.70 (s, 1H), 7.49 (d, 2H, J ¼ 8.6 Hz), 7.11 (d, 2H, J ¼ 8.6 Hz), 4.38 (t, 2H), 4.30 (t, 2H), 1.84e1.68 (m, 4H), 1.56e1.48 (m, 4H), 1.46e0.9 (m, 15H). 13C NMR (75 MHz, CDCl3, ppm): d ¼ 168.28, 167.38, 163.47, 163.21, 155.23, 152.27, 148.17, 136.23, 135.23, 133.13, 131.93, 131.88, 131.84, 131.16, 130.67, 130.28, 128.83, 127.35, 127.29, 127.10, 125.29, 124.04, 123.58, 121.63, 121.33, 121.04, 120.38, 119.20, 65.61, 65.58, 53.41, 34.53, 31.45, 30.63, 30.38, 29.70, 19.25, 19.10, 13.78, 13.70. MS (MALDI-TOF): m/z ¼ 699.27 (Mþ). 2.3.14. Synthesis of 1,7(6)-di-(4-tert-butylphenoxy)-perylene-3,4dicarboximide-9,10-dicarbonylate (13) 10 (150 mg, 0.22 mmol), 4-tert-butylphenol (330 mg, 2.2 mmol), K2CO3 (304 mg, 2.2 mmol) and catalyzed KI were added in 10 ml NMP. The reaction mixture was stirred for 6 h at 60 C under argon atmosphere. Then MeOH (10 ml) and 10% HCl solution (50 ml) were added into the cooled reaction mixture. The precipitate was collected by filtration, washed with methanol, and then dried in vacuum. The crude product was further purified by silica gel column chromatography with the eluent CH2Cl2/acetone (100:0.5 v/v) to give an inseparable mixture of 13a and 13b (142 mg, 79%). 1H NMR (CDCl3, 300 MHz, ppm): d ¼ 9.37e9.33 (m, 2H 0.5), 9.32 (d, 2H 0.5, J ¼ 8.3 Hz), 8.57 (d, 1H 0.5, J ¼ 8.3 Hz), 8.32 (s, 1H 0.5), 8.27 (s, 2H 0.5), 8.08 (d, 2H 0.5, J ¼ 8.3 Hz), 8.03 (d, 1H 0.5, J ¼ 8.3 Hz), 7.75 (s, 1H 0.5), 7.44e7.38 (m, 4H), 7.06e7.00 (m, 4H), 6.59 (s, 1H), 4.33 (m, 4H), 1.75e1.64 (m, 4H), 1.50e1.40 (m, 4H), 1.27e0.84 (m, 24H). 13C NMR (13, 75 MHz, CDCl3, ppm): d ¼ 168.27, 167.52, 163.20, 162.82, 154.17, 153.80, 153.17, 152.63, 147.84, 147.64, 134.70, 132.83, 131.98, 131.00, 130.57, 129.99, 129.01, 128.55, 127.64, 127.29, 127.19, 124.40, 123.48, 122.33, 120.76, 118.94, 118.56, 65.50, 65.41, 34.45, 31.43, 30.62, 30.37, 29.67, 19.22, 19.09, 13.73, 13.67. MS (MALDI-TOF): m/z ¼ 817.36 (Mþ).
3. Results and discussions 3.1. Synthesis The chemical structures of asymmetrical intermediates 1, 2 and 3 and their synthetic routes are shown in Scheme 1. The synthesis started from the hydrolysis of perylene bisanhydride in aqueous solution of KOH to afford tetrapotassium salt of 3,4,9,10-perylene tetracarboxylic acid (PTCTK). The salt was treated with n-bromobutane
Scheme 2. The synthesis of compounds 4 and 5. (f) Br2, I2, CHCl3, reflux, 42%; (g) Br2, I2, CHCl3, reflux, 50.5%.
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in presence of K2CO3 to obtain tetrabutyl perylene tetracarbonate (PTE). In mixed solvents of n-heptane and toluene, PTE was hydrolyzed by p-toluenesulfonic acid at one side to yield compound 1 as precipitate. Compounds 2 and 3 were synthesized by the imidization of 1 using cyclohexylamine and ammonium acetate respectively [35]. The brominations of 1, 2 and 3 are summarized in Schemes 2e4 respectively. PTCTK was obtained via hydrolysis of perylene bisanhydride in aqueous solution of potassium hydroxide. The resulting solution was dropwise added into a mixture of i-propanol and acetone (1:1 v/v) to yield PTCTK as precipitate in a high yield. With moderate reactivity, n-bromobutane was chosen to react with PTCTK to synthesis the ester in presence of K2CO3, which was used as base instead of usually used KOH [22]. Because KOH could also react with n-bromobutane in reaction to give hard removable butanol. The synthesis of compound 1 was a key step to achieve asymmetrical perylene intermediates. PTE is very sensitive to acid and can be converted to poorly soluble perylene monoanhydride and then to insoluble perylene dianhydride. However, if the less soluble intermediate 1 with one anhydride group can be precipitated from
the reaction solution, the formation of the second anhydride group will be prevented. n-Heptane is a straight-chain alkane with boiling point of 98 C, which is an appropriate temperature for the acidic hydrolysis of PTE [35]. Owing to its poor solubility, heptane needs to be mixed portion of good solvent to support enough solubility in reaction. Thus the mixed solvents of n-heptane and toluene (5:1 v/v) were used in the reaction. Besides proper the solvent system, the alkyl groups of the PTE also play important role in turning the solubility of the intermediate 1. In past works, long carbon chain such as decyl and lauryl groups were used in PTE for good solubility [35,36]. Long chain would enable the perylene monoanhydride diester partially resolved and result in the second acidic hydrolysis to form insoluble perylene dianhydride at last. Through comparison, butyl group was used herein to synthesize compound 1 in a satisfactory isolated yield (80%). This route is a very important and the most efficient method at present to synthesize the asymmetrical perylene derivatives. With an anhydride group, compound 1 can facilely react with various primary amines or ammonium salts to synthesize perylene monoimide diester dyes. Here cyclohexylamine and ammonium
Scheme 3. The synthesis of compounds 6e8. (h) Br2, I2, CHCl3, room temperature, 58%; (i) Br2, I2, CHCl3, room temperature, 70%; (j) 4-tert-Butylphenol, K2CO3, KI, NMP, 60 C, 85%.
R. Wang et al. / Dyes and Pigments 98 (2013) 450e458
Scheme 4. The synthesis of compounds 9e13. (k) Br2, I2, CHCl3, reflux, 42%; (l) Br2, I2, CHCl3, reflux, 65%; (m) 4-tert-butylphenol, K2CO3, KI, NMP, 60 C, 11 (40%), 12 (41%); (n) 4-tert-butylphenol, K2CO3, KI, NMP, 60 C, 79%.
acetate were used in reactions respectively to give intermediates 2 and 3. Similar with 1, various N-substituted perylene monoimide diester dyes could be prepared from intermediate 3 by its reactions with alkyl halides. Thus 3 typical asymmetrical intermediates of perylene monoimide diester were synthesized and their brominations were then investigated. The mono-bromination and dibromination of intermediates 1, 2 and 3 could be controlled by using different concentration of bromine. Chloroform was used as solvent in the reactions, instead of dichloromethane usually used in bromination of perylene derivatives, due to its better solubility and higher boiling point. Using a low concentration of bromine, 1 was brominated to mainly yield the mono-brominated product after purification with column chromatography, which was confirmed by MS spectrum. However, the 1H NMR and 13C NMR spectra of the sample showed two sets of signals in a definite ratio in the aromatic region, indicating that the sample was a couple of isomers. The chemical structures of the isomers were confirmed as 1-Br-1(4a) and 7-Br-1
455
(4b) [34,35,37]. According to the integration areas of the singlets at 8.91 ppm and 8.39 ppm in the 1H NMR spectrum, the isomers 4a and 4b were presented in a ratio about 1:0.6. 1 was fully brominated to yield di-brominated product 5 in higher concentration of bromine. 5 was confirmed with a unique structure of dibutyl-1,7-diBr-perylene-3,4-anhydride-9,10-dicarbonylate. The 1 H NMR spectrum of 5 showed characteristic signals of 1-Br- and 7Br-substituted 1 at 8.91 ppm and 8.36 ppm respectively, which was very similar with the mono-brominated isomers 4a and 4b. Carbon signals of two ester C]O and two imide C]O appeared at 167.54 ppm, 166.67 ppm and 159.43 ppm, 159.11 ppm respectively (Table 1) in 13C NMR spectrum, indicating the structure hadn’t any axis or center of symmetry. Compared with the mono-bromination of 1, the di-bromination was more facile to be controlled and was in higher yield. The di-bromination of 1 should be divided into two steps. The first step afforded isomer 4a and 4b in a ratio of 1:0.6. Then the second step of bromination took place only at opposite position of the first bromine atom at bay-area of the perylene core. The result was neither similar with the di-bromination of PBI, which resulted in isomers of 1,7- and 1,6-di-brominated PBI [38]; nor similar with the bromination of perylene bisanhydride, which resulted in a mixture of brominated compounds in different levels as well as the isomers of 1,7- and 1,6-diBr-perylene bisanhydride [39]. Therefore, the intermediate 1 was very useful in designing and synthesizing of disubstituted asymmetrical perylene dyes for its unique structure and high yield. The bromination degree of 2 was also controllable. Monobrominated product 6 was predominant when reaction was carried out in a low concentration of bromine. The interesting result was that the bromination took place only at 1-position of the intermediate 2. The signal of the doublet at 9.41 ppm and the singlet at 8.61 ppm were typical characteristic of 1-Br-perylene-3,4dicarboximide dyes. In 13C NMR spectrum, carbons of two ester C]O appeared at 168.18 ppm and 168.06 ppm respectively, while carbons of two imide C]O appeared at 163.72 ppm and 162.96 ppm respectively (Table 1). The larger difference of two imide C]O implied that the bromination took place near the imide group. Correspondingly the substituted bromine atom had less influence on two ester C]O at farer side. Therefore, 2 was an important intermediate to design and synthesize mono-substituted asymmetrical perylene dyes for its unique structure of monobrominated product. 7 was obtained as main product in the bromination of 2 in higher concentration of bromine. According to the MS data, the product was di-brominated 2. But the exact chemical structure could not be determined by the 1H NMR and 13C NMR spectra (Fig. 1). Therefore, a further reaction with 4-tert-butylphenol was performed. The reaction of phenol with brominated perylene derivative has been proven to be effective, and to be not selective toward brominated isomers. Generally the substitution of bromine atom by phenol took place at original position. The phenol disubstituted 2 was purified with column chromatography on silica gel. The presence of 3 singlets at 7.77 ppm, 8.23 ppm and 8.30 ppm in aromatic region of 1H NMR spectrum indicated that the phenol
Table 1 The chemical shifts of carbons in carbonyl groups for compounds 4e6, 8 and 11e13. Compound 4
d (ppm) (ester C]O) d (ppm) (imide C]O)
5
6
8
167.92, 167.54, 168.18, 168.45, 167.84 166.67 168.06 168.34, 167.60 159.71, 159.43, 163.72, 163.99, 159.11 159.11 162.92 163.61, 163.39
11
12
13
168.41, 168.28, 168.27, 168.28 167.38 167.52 163.23, 163.47, 163.20, 162.59 163.21 162.82
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Fig. 1. Low-field section of the 1H NMR spectra of 7 (a) and 8 (b).
Fig. 2. Low-field section of the 1H NMR spectra of 10 (a) and 13 (b).
di-substituted 2 was isomers. According to the ratio of the integration areas, the signals could be clearly divided into two sets. Two singlets at 7.77 ppm and 8.30 ppm were attributed to 1.7-di-4-tertbutylphenol substituted perylene derivative 8a. The last singlet 8.23 ppm should correspond to a symmetric structure. Combing the 13 C NMR spectrum, the isomer was with a 1.6-di-4-tert-butylphenol substituted structure of 8b. As shown in Fig. 1, the ratio of 8a and 8b for the phenol di-substituted isomers was determined as 1:0.45 according to integration areas of corresponding signals. Therefore, the ratio of 1,7-dibrominated isomer 7a and 1,6-dibrominated isomer 7b was supposed to be approximate 1:0.45. 3 could be mono-brominated and di-brominated in reactions by using different concentrations of bromine. The predominant product 9 was obtained in low concentration of bromine. While the predominant product 10 was obtained in high concentration of bromine. 9 and 10 were confirmed as mono-brominated and dibrominated products respectively by MS data. But the exact chemical structures of both samples couldn’t be confirmed by the 1 H NMR and 13C NMR spectra. Thus 9 and 10 were further reacted with 4-tert-butylphenol respectively. The main reaction products of 9 were separated by column chromatography on silica gel to afford 11 in 40% yield and 12 in 41% yield. According to some characteristic NMR data of 11, such as signet at 8.30 ppm in 1H NMR spectrum, carbons of two ester C]O at 168.41 ppm and 168.28 ppm and carbons of two imide C]O at 163.23 ppm and 162.59 ppm in the 13 C NMR spectrum, the substituted position should be near the imide group (Table 1). Thus the chemical structure of 11 was confirmed as dibutyl-1-(4-tert-butylphenoxy)-perylene-3,4dicarboximide-9,10-dicarbonylate. The characteristic NMR data of 12, such as signet at 7.70 ppm in 1H NMR spectrum, carbons of two ester C]O at 168.28 ppm and 167.38 ppm and carbons of the two imide C]O at 163.47 ppm and 163.21 ppm in the 13C NMR spectrum, indicated the substituted position closed to the ester groups. Namely the chemical structure of 12 was confirmed as dibutyl-7(4-tert-butylphenoxy)-perylene-3,4-dicarboximide-9,10dicarbonylate. Accordingly the mono-brominated product 9 should be a couple of isomers, including 1-Br-3 (9a) and 7-Br-3 (9b) with a deduced ratio about 1:1. The main product 13 was separated with column chromatography on silica gel from the reaction of 10 with 4-tert-butylphenol. 13 was proven to be a mixture of isomer 13a and isomer 13b with 1 H NMR (Fig. 2) and 13C NMR data (Table 1). The signals could be divided into two sets in aromatic region of 1H NMR spectrum of 13.
Three characteristic singlets were observed at 7.75 ppm, 8.27 ppm and 8.32 ppm respectively in the aromatic region. Among that, two singlets at 7.75 ppm and 8.32 ppm in ratio of 1:1 were attributed to 1,7-disubstituted 13a. The last one at 8.27 ppm was attributed to a symmetric structure of 1,6-disubstituted 13b. The integration areas of 3 singlets revealed that 13a and 13b were presented in a ratio about 1:1. Thus combining the former NMR data, the di-brominated 3 was presumed including 1,7-di-brominated isomer 10a and 1,6di-brominated isomer 10b with a deduced ratio about 1:1. The brominations of the 3 intermediates are summarized in Table 2. The mono-bromination and di-bromination of 3 typical intermediates could be controlled by using different concentration of bromine. Compound 1, with an anhydride group, was monobrominated to give inseparable 1-Br-1 (4a) and 7-Br-1 (4b) in ca. 1:0.6 ratio with a total yield of 42%. The di-brominated product was unique 1,7-diBr-1 (5). Incorporated with cyclohexyl group at imide group, the N-substituted compound 2 was mono-brominated to yield unique 1-Br-2 (6) in a yield of 58%. The di-brominated products were inseparable 1,7-diBr-2 (7a) and 1,6-diBr-2 (7b) in ratio of 1:0.45. The bromination of 3 was the most complicated case. Both the mono-bromination and the di-bromination afforded inseparable isomers. The isomers of mono-brominated 1(7)-Br-3 and di-brominated 1,7(6)-diBr-3 were finally presumed with a similar ratio of 1:1. In general, compound 1 is an ideal intermediate for synthesis of di-substituted asymmetrical perylene dyes, and compound 2 is a useful intermediate to synthesize mono-substituted asymmetrical perylene dyes. 3.2. Absorption and emission properties of dyes The UVevis absorption and emission spectra of corresponding compounds were measured in chloroform at room temperature. The data are summarized in Table 3. In order to compare the
Table 2 Summary of the bromination of 1e3. Compound
1 2 3
monoBr-
Ratio
1-Br-
7-Br-
4a 6 9a
4b e 9b
1:0.6 e 1:1
diBr-
Ratio
1,7-diBr-
1,6-diBr-
5 7a 10a
e 7b 10b
e 1:0.45 1:1
R. Wang et al. / Dyes and Pigments 98 (2013) 450e458
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Table 3 Absorption and emission data for PTE and 1e13 in chloroform (105 M). Compound
PTE
1
2
3
4
5
6
7
8
9
10
11
12
13
lmax (nm) lem (nm)
472 488
506 527
505 525
506 531
505 537
506 542
503 528
503 535
517 557
505 536
505 541
514 542
506 560
526 562
Fig. 3. UVevis absorption and emission spectra of PTE, compounds 1e5 in chloroform (105 M). Fig. 5. UVevis absorption and emission spectra of compounds 3 and 9e13 in chloroform (105 M).
location of peaks and shape, all absorption spectra were normalized. As shown in Fig. 3, PTE exhibits strong perylene core absorption band at 472 nm. Perylene monoanhydride diester 1 has a larger p-system than PTE, and shows a remarkable red-shift about 34 nm in absorption spectrum. After formation of imide structure whether introducing substitutes at the N atom (2) or not (3), however, the absorption change vary slight. The results indicate that the formation of imide group and incorporating other group at the N atom hardly change the electronic structure of perylene monoanhydride diester (1). The mono-brominated 1 (compound 4) and di-brominated 1 (compound 5) show the maximal absorption band at 505 nm and 506 nm respectively that are very similar with 1 (506 nm). Thereby the brominations of 1 lead to almost negligible change in absorption. Compared with the absorption spectra, the
emission spectra show relatively obvious change. The formation of imide group result in a 2 nm blue shift for 2 and a 2 nm red-shift for 3, and result in remarkable increase of intensity that maybe owing to the decrease of the pep stacking. The mono-bromination and dibromination of 1 lead to 10 nm and 15 nm red-shift respectively in emission spectra. Similar with compound 1, the bromination of 2 and 3 leads to slight changes in absorption and relatively obvious changes in emission (Figs. 4 and 5, Table 3). But the introduction of phenoxy groups results in obvious changes both in absorption and emission. Compared with 7, red-shifts about 14 and 22 nm in the absorption and emission for 8 are observed. The phenol di-substituted 13 results in a same 21 nm red-shift both in absorption and emission spectra compared with 10. The interesting result is that the separated isomers 11 and 12 exhibit quite different shapes and location of peaks both in absorption and emission spectra. The 1-phenolsubstituted 11 shows 9 nm red-shift in absorption spectra and 18 nm blue shift in emission spectra compared with the 7-phenolsubstituted 12. Therefore, the position of substituted group plays an important role in turning the absorption and emission of perylene monoimide diester. 4. Conclusions
Fig. 4. UVevis absorption and emission spectra of compounds 2 and 6e8 in chloroform (105 M).
In conclusion, a facile and effective synthesis of the asymmetrical intermediate of dibutyl-perylene-3,4-anhydride-9,10-di-carbonylate was developed using readily available tetraesters of perylene tetracarboxylic acids as starting materials. By choosing properly long carbon chain in ester group and proper solubility of a mixed solvent system, the less soluble perylene monoanhydride diester (1) formed in first step of acidic hydrolysis could be isolated from the reaction solution as precipitate to prevent the second acidic hydrolysis. Based on the intermediate, two other asymmetrical perylene intermediates 2 and 3 were designed and
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synthesized. The mono-bromination and di-bromination of 3 typical intermediates could be controlled by using different bromine concentration. The chemical structures of the brominated products were confirmed directly or deduced from the further phenol substituted products with MS and NMR spectra. Intermediate 1 was mono-brominated to give inseparable 1-Br-1 (4a) and 7-Br-1 (4b) in ca. 1:0.6 ratio with a total yield of 42%. Its dibrominated product was unique 1,7-diBr-1 (5) with a yield of 50.5%. Intermediate 2 was mono-brominated to yield unique 1-Br-2 (6) in a yield of 58%. The di-brominated 2 was inseparable isomers with indeterminable structures. The isomers were further reacted with 4-tert-butylphenol. Despite the phenol di-substituted isomers were still inseparable, their chemical structures and their ratio could be determined. Thus the structures of di-brominated 2 were confirmed as 1,7-diBr-2 (7a) and 1,6-diBr-2 (7b) in a deduced ratio of 1:0.45. Both the mono-brominated and di-brominated 3 were inseparable isomers of 9 and 10 with indeterminable structures. They were further reacted with 4-tert-butylphenol respectively. The main reaction products of 9 were separable 11 and 12 and the main products of 10 were inseparable isomer 13a and isomer 13b. Thus the mono-brominated and di-brominated 3 were confirmed as 1(7)-Br-3 (9a and 9b) and 1,7(6)-diBr-3 (10a and 10b) respectively with a same deduced ratio of 1:1. The intermediate 1 is useful for the synthesis of di-substituted asymmetrical dyes based on perylene, and intermediate 2 is useful for the synthesis of monosubstituted asymmetrical dyes base on perylene. Formation of imide group and bromination of the intermediates led to only slight changes in absorption spectra, but resulted in relatively obvious changes in emission spectra. Acknowledgment This work was supported by the Provincial Natural Science Foundation of Shandong (ZR2012BM012). Appendix A. Supplementary data Supplementary data related to this article can be found at http:// dx.doi.org/10.1016/j.dyepig.2013.04.006. References [1] Pasaogullari N, Icil H, Demuth M. Symmetrical and unsymmetrical perylene diimides: their synthesis, photophysical and electrochemical properties. Dyes Pigm 2006;69:118e27. [2] Tian H, Liu PH, Zhu WH, Gao EQ, Wu DJ, Cai SM. Synthesis of novel multichromophoric soluble perylene derivatives and their photosensitizing properties with wide spectral response for SnO2 nanoporous electrode. J Mater Chem 2000;10:2708e15. [3] He XR, Liu HB, Li YL, Wang S, Li YJ, Wang N, et al. Gold nanoparticle-based fluorometric and colorimetric sensing of copper (II) ions. Adv Mater 2005;17:2811e5. [4] Tan WJ, Li X, Zhang JJ, Tian H. A photochromic diarylethene dyad based on perylene diimide. Dyes Pigm 2011;89:260e5. [5] Yilmaz MD, Bozdemir OA, Akkaya EU. Light harvesting and efficient energy transfer in a boron-dipyrrin (BODIPY) functionalized perylenediimide derivative. Org Lett 2006;8:2871e3. [6] Zhao CT, Zhang YX, Li RJ, Li XY, Jiang JZ. Di(alkoxy)- and di(alkylthio)substituted perylene-3,4;9,10-tetracarboxy diimides with tunable electrochemical and photophysical properties. J Org Chem 2007;72:2402e10. [7] Zagranyarski Y, Chen L, Zhao Y, Wonneberger H, Li C, Müllen K. Facile transformation of perylene tetracarboxylic acid dianhydride into strong donore acceptor chromophores. Org Lett 2012;14:5444e7. [8] Li Y, Tan L, Wang ZH, Qian H, Shi Y, Hu WP. Air-stable n-type semiconductor: core-perfluoroalkylated perylene bisimides. Org Lett 2008;10:529e32. [9] Huang C, Barlow S, Marder SR. Perylene-3,4:9,10-tetracarboxylic acid diimides: synthesis, physical properties, and use in organic electronics. J Org Chem 2011;76:2386e407.
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