Synthesis and fluorescence sensing properties of a new naphthalimide derivative of calix[4]arene

Tetrahedron Letters 53 (2012) 2319–2324

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Synthesis and fluorescence sensing properties of a new naphthalimide derivative of calix[4]arene Ozlem Sahin, Mustafa Yilmaz ⇑ Selcuk University, Department of Chemistry, 42031 Konya, Turkey

a r t i c l e

i n f o

Article history: Received 28 November 2011 Revised 13 February 2012 Accepted 23 February 2012 Available online 3 March 2012

a b s t r a c t A new naphthalimide derivative of calix[4]arene was synthesized as a highly selective fluorescent compound for Cu2+ among the selected metal ions. This compound was examined for its fluorescent properties toward different metal ions (Na+, Li+, Mg2+, Ni2+, Ba2+, Ca2+, Cu2+, Pb2+, Zn2+) and anions (F , Cl , Br , H2 PO4 , NO3 , I , HSO4 , CH3COO ) by UV, NMR and fluorescence spectroscopy. Ó 2012 Elsevier Ltd. All rights reserved.

Keywords: Calix[4]arene Naphthalimide Fluorescent Complex

Fluorescent chemosensors are powerful tools for the efficient detection and quantitative determination of target ions or molecules.1 In particular, the development of fluorescent probes for heavy metal ions, which play critical roles in biological metabolism and environmental processes, has received much interest.2 Fluorescence-based detection offers several advantages over other analytical methods which include high sensitivity, specificity, and realtime monitoring with fast response times.3 Successful fluorescent sensors usually include three important parts: the fluorophore, a binding-recognition unit, and a signal conducting mechanism.4 Calixarenes have received a great deal of attention as host molecules in supramolecular chemistry. An important feature of these compounds is their synthetic flexibility. Chemical modification of the lower and upper calixarene rims by introducing groups with different binding abilities enables them to form inclusion complexes with a wide variety of guest species.5–8 The preorganized binding sites, easy derivatization, and flexible three dimensional structures of calixarenes make them perfect construction platforms for molecular design to generate fluorescent receptors.9 Most calix[4]arene-based fluorescent sensors have been designed based on the photophysical changes upon metal ion binding with mechanisms including photoinduced electron transfer (PET),10 photoinduced charge transfer (PCT),11 formation of a monomer/ excimer,12 and energy transfer.13,14 Derivatives of 1,8-naphthalimide are among the most frequently used signaling fragments for the synthesis of fluorescent sensors for metal ions. Their molecular structures allow tuning of ⇑ Corresponding author. Tel.: +90 332 2233873; fax: +90 332 2410520. E-mail address: [email protected] (M. Yilmaz). 0040-4039/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.tetlet.2012.02.104

the photophysical properties of the newly synthesized compound, (especially fluorescence color and intensity).15 In this Letter we describe the synthesis of a new 1,8-naphthalimide based calix[4]arene fluorophore. Reaction of 4-bromo-1,8naphthalic anhydride (1) with ethylamine gave 2,16 which was reacted with 1,2-diaminoethane by adapting a known procedure17 to yield 3.18 Compounds 4, 5, and 619 were prepared according to the published procedures and 25,27-bis(methoxycarbonylmethoxy)-26,28-dihydroxycalix[4]arene (6) was heated at reflux with 3,6-dioxa-1,8-diaminooctane to give the amide derivative of calix[4]arene 720 in 73% yield. This amide was reacted with hexamethylenetetramine-trifluoroacetic acid to afford the dialdehyde 821 in 73% yield. Finally, sensor 922 was obtained by the treatment of calix[4]arene 8 with amine 3 in chloroform/methanol (Scheme 1). The synthesized compounds were characterized by a combination of FTIR, 1H NMR, and elemental analysis. The 1H NMR spectrum of 9 showed one singlet (2H) at d 7.53 ppm, one doublet (4H) at d 6.76 ppm, and one triplet (2H) at d 6.65 ppm for the aromatic protons, one triplet (2H) at d 7.89 ppm for the amide protons, one singlet (2H) at d 8.27 ppm for the imino protons, and four doublets (8H) at d 6.81, 8.12, 8.48, 8.55 ppm and one triplet (2H) at d 7.56 ppm for the naphthalene protons. The formation of the naphthylimide derivative of calix[4]arene 9 was confirmed by the appearance of characteristic amide and imine bands at about 1670 and 1638 cm 1 in the IR spectrum. The cation and anion binding properties of compound 9 were investigated by UV–Vis and fluorescence spectroscopy. The titration experiments were carried out in CH2Cl2/CH3CN (1:1 v/v) by adding aliquots of various cations and anions.

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O

O

O

O

N

O

H2N

H2N

O

NH2

80%

Br

Br

N

O

NH

H2N 2

1

OH OHOH

3

OH

OHOH

OH

4

OH

5

BrCH2COOCH3 O

O

HN

HN

O

H2N

O

O

OCH3

O

O OH OH

O

O

OHOH

O

H3CO O

O

NH2

65% 6

7

TFA/HMTA

70% O N O O O

O

HN

NH HN

O OHOH

O

HN

O

O

O O

O

HN OHOH

O

H2N

O

60% O

N

O H

N

H HN

NH

8 O

N

O

O N O

9 Scheme 1. Synthesis of novel naphthalimide functionalized calix[4]arene.

The UV–Vis absorption spectra of compound 9 exhibited typical naphthalimide absorption bands at 420 nm (Fig. 1). On the addition of Cu2+ ions (10 equiv) to a solution of 9, the absorption peak at 420 nm disappeared. There was no change in the intensity of this absorption peak upon the addition of other cations and anions to the solution of 9. The perchlorate salts of Ca2+, Cu2+, Li+, Mg2+, Ba2+, Na+, Ni2+, Pb2+, and Zn2+ ions were used to evaluate the metal ion binding properties of 9 in CH2Cl2/CH3CN (1:1, v/v). The emission spectrum of 9, when excited at 380 nm is shown in Figure 2, and shows the main

band at 510 nm. There was a highly selective fluorescence quenching effect in its emission with only Cu2+ among the metal ions examined. The quenching of the 510 nm (naphthalimide) emission can be attributed to the redox active Cu2+ being brought into proximity to the naphthalimide fluorophore where it binds to the Schiff base region of 9 and quenches the excited state by electron/energy transfer.23 The Job plot for the binding between 9 and Cu2+ shows 1:2 stoichiometry (Fig. 3). The fluorescence intensity of 9 in the presence of increasing amounts of Cu2+ is shown in Figure 4. The fluorescence intensity

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Figure 1. UV–Vis. spectra of 9 (1.10

4

M) (a) upon addition of ClO4 salts of cations (10 equiv) (b) tetrabutylammonium salts of anions (100 equiv) in CH2Cl2/CH3CN (1:1, v/v).

Figure 2. Fluorescence spectra of 9 (1.10

6

M) upon addition of ClO4 salts of Ca2+, Cu2+, Li+, Mg2+, Ba2+, Na+, Ni2+, Pb2+ and Zn2+ (10 equiv) in CH2Cl2/CH3CN (1:1, v/v).

Figure 3. Job’s plots of compounds 9, Cu2+and NO3 ions, [9] + [ Cu2+] and [9] + [NO3 ] = 1  10

Figure 4. Fluorescence spectra of 9 (1.10

6

3

M in CH3CN/CH2Cl2 (1:1, v/v).

M) in CH2Cl2/CH3CN (1:1, v/v) upon addition of increasing concentrations of Cu(ClO4)2 (0–10 equiv) with excitation at 380 nm.

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Figure 5. Fluorescence quenching ratio [(Io I/Io)  100] of 9 (1  10 6 M) towards Cu2+ ions (10 equiv) in the presence of other metal ions (100.0 equiv, Ca2+, Pb2+, Li+, Mg2+, Ba2+, Na+, Ni2+ and Zn2+ in CH2Cl2/CH3CN (1:1, v/v)).

of the monomer and excimer emissions at 380 nm gradually decreased with increasing Cu2+ concentrations (0–10 equiv).

To confirm 9 as an ion-selective fluorescence chemosensor for Cu2+ the effect of competing metal ions was determined. Sensor 9 (1.10 6 M) was treated with 10 equiv of Cu2+ in the presence of other metal ions (100 equiv). As shown in Figure 5, no interference in the detection of Cu2+ was observed in the presence of Ca2+, Pb2+, Li+, Mg2+, Ba2+, Na+, Ni2+, and Zn2+. The fluorescence emission changes of 9 upon the addition of F , Cl , Br , H2 PO4 , NO3 , I , and HSO4 (100 equiv, as tetrabutylammonium salts) in CH2Cl2/CH3CN (1:1, v/v) are illustrated in Figure 6. There was no selective fluorescence quenching effect in the emission spectra with these anions. The fluorescence intensity of 9 in the presence of increasing amounts of NO3 is shown in Figure 7. The fluorescence intensities of the monomer and excimer emissions of 9 at 380 nm gradually decreased with increasing NO3 concentrations (0–100 equiv). The Job plot for the binding between 9 and NO3 shows 1:1 stoichiometry (Fig. 3). Figure 8 shows the Stern Volmer analyses24 for the complexation of Cu2+ and NO3 by 9: linear behavior was observed. The quenching constants (Ksv) are given in Table 1.

Figure 6. Fluorescence spectra of 9 (1.10

6

M) upon addition of tetrabutylammonium salts of F , Cl , Br , H2 PO4 , NO3 , I and HSO4 (100 equiv) in CH2Cl2/CH3CN (1:1, v/v).

Figure 7. Fluorescence spectra of 9 (1.10 with excitation at 380 nm.

6

M) in CH2Cl2/CH3CN (1:1, v/v) upon addition of increasing concentrations of the tetrabutylammonium salt of NO3 (0–100 equiv)

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Figure 8. Stern–Volmer plots for the fluorescence quenching of Cu2+ and NO3 by 9, in CH3CN/CH2Cl2 (1:1, v/v).

Figure 9. Plot of Io/(Io I) versus [Cu2+] with Cu2+ in CH3CN/CH2Cl2 (1:1 v/v).

1

for the spectrofluorimetric titration of 9

Table 1 Quenching constants for the complexation of Cu2+ and NO3 by 9, in CH3CN/CH2Cl2 (1:1 v/v) obtained from Figure 8 Ligand 9

Quenching constant (Ksv) 2+

Cu NO3

5

2.38  10 ± 0.04 1.64  105 ± 0.02

R2 0.9669 0.9745

The complex stability constant (b) was calculated using Valeur’s method.25 Accordingly, the quantity I0/(I0 I) is plotted versus [metal ion] 1 with the stability constant given by the ratio of intercept/ slope26,27(Fig. 9). The stability constants for complexation of Cu2+ with 9 were determined by fluorimetric titration. The titrations were performed by adding solutions of various concentrations of metal perchlorate in CH3CN/CH2Cl2 to solutions of the ionized ligand in the same solvent. The ligand concentration was held constant at 1  10 6 M. From the fluorescence titrations, the stability constant of 9 with Cu2+ was calculated to be 4.58 ± 0.10. We were unable to probe further the binding event between 9 and Cu2+ by NMR spectroscopy due to the paramagnetic nature of Cu2+. To understand clearly the above binding and fluorescence behavior between 9 and NO3 ions, we carried out 1H NMR experiments on 9 in the absence or presence of NO3 . The results obtained are illustrated in Figure 10 [free 9 in CDCl3/CD3CN (1:1.5, v/v) and 9 + 1 equiv NO3 in CDCl3/CD3CN (1:1.5, v/v)]. For the host 9 in CDCl3/CD3CN, upon addition of 1 equiv of NO3 , the proton signal of the amide NH at 7.89 ppm, disappeared. Accordingly, the mechanism of complex formation is between 9 and NO3 is as postulated in Scheme 2. In conclusion, a new naphthalimide derivative of calix[4]arene 9 was synthesized and was shown to be a highly selective fluorescence chemosensor for Cu2+, among the other metal ions examined.

Figure 10. 1H NMR spectra of receptor 9 (20 mM) and that after addition of NO3 ions (1.0 equiv) in CDCl3/CD3CN (1:1.5, v/v) solution.

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O O

O

HN

HN

O OH OH

HN

NO3-

O O

O

O

HN

O

NO3-

O

OHOH

O

N

O

N

N

N

NH NH

O O

N

O

NH

NH

O

N

N

O

O

N

O

O

Scheme 2. Possible structures of free 9 and 9 + NO3 .

Acknowledgements We thank the Scientific Research Projects Foundation of Selcuk University (SUBAP-Grant Number 2009-09101019) and The Scientific and Technological Research Council of Turkey (TUBITAK-Grant Number 110T482) for financial support of this work produced from a part of O. Sahin’s Ph.D. Thesis. References and notes 1. Han, D. Y.; Kim, J. M.; Kim, J.; Jung, H. S.; Lee, Y. H.; Zhang, J. F.; Kim, J. S. Tetrahedron Lett. 2010, 51, 1947–1951. 2. Foster, R. J.; Kelly, J. P. J. Electroanal. Chem. 2001, 498, 127–136. 3. Lee, Y. H.; Liu, H.; Lee, J. Y.; Kim, S. H.; Kim, S. K.; Sessler, J. L.; Kim, Y.; Kim, J. S. Chem. Eur. J. 2010, 16, 5895–5901. 4. Yang, Y.; Gou, X.; Blecha, J.; Cao, H. Tetrahedron Lett. 2010, 51, 3422–3425. 5. Galic´a, N.; ü Buric´a, N.; ü Tomasa, R.; ü Frkanecb, L.; Tomisic´a, V. Supramol Chem. 2011, 23, 389–397. 6. Sayin, S.; Yilmaz, M.; Tavasli, M. Tetrahedron 2011, 67, 3743–3753. 7. (a) Akceylan, E.; Yilmaz, M. Tetrahedron 2011, 67, 6240–6245; (b) Kocabas, E.; Karakucuk, A.; Sirit, A.; Yilmaz, M. Tetrahedron: Asymmetry 2006, 17, 1514– 1520; (c) Yilmaz, A.; Tabakci, B.; Akceylan, E.; Yilmaz, M. Tetrahedron 2007, 63, 5000–5005. 8. Bayrakci, M.; Ertul, S.; Yilmaz, M. Tetrahedron 2009, 65, 7963–7968. 9. Sahin, O.; Yilmaz, M. Tetrahedron 2011, 67, 3501–3508. 10. (a) Aoki, I.; Sakaki, T.; Shinkai, S. J. Chem. Soc. Chem. Commun. 1992, 730–732; (b) Bu, J. H.; Zheng, Q. Y.; Chen, C. F.; Huang, Z. T. Org. Lett. 2004, 6, 3301–3303. 11. (a) Leray, I.; Lefevre, J. P.; Delouis, J. F.; Delaire, J.; Valeur, B. Chem. Eur. J. 2001, 7, 4590–4598; (b) Kim, S. K.; Bok, J. H.; Bartsch, R. A.; Lee, J. Y.; Kim, J. S. Org. Lett. 2005, 7, 4839–4842; (c) Choi, J. K.; Kim, S. H.; Yoon, J.; Lee, K. H.; Bartsch, R. A.; Kim, J. S. J. Org. Chem. 2006, 71, 8011–8015. 12. (a) Jin, T.; Ichikawa, K.; Koyana, T. J. Chem. Soc., Chem. Commun. 1992, 499–501; (b) Kim, S. K.; Lee, S. H.; Lee, J. Y.; Lee, J. Y.; Bartsch, R. A.; Kim, J. S. J. Am. Chem. Soc. 2004, 126, 16499–16506; (c) Schazmann, B.; Alhashimy, N.; Diamond, D. J. Am. Chem. Soc. 2006, 128, 8607–8614. 13. (a) Jin, T. Chem. Commun. 1999, 2491–2492; (b) Castellano, R. K.; Craig, S. L.; Nuckolls, C.; Rebek, J., Jr. J. Am. Chem. Soc. 2000, 122, 7876–7882. 14. Chang, K. C.; Su, I. H.; Senthilvelan, A.; Chung, W. S. Org. Lett. 2007, 9, 17. 15. Staneva, D.; McKena, M.; Bosch, P.; Grabchev, I. Spectrochim. Acta Part A 2010, 76, 150–154. 16. Gunnlaugsson, T.; Kruger, P. E.; Jensen, P.; Tierney, J.; Ali, H. D. P.; Hussey, G. M. J. Org. Chem. 2005, 70, 10875–10878. 17. Singh, N.; Kaur, N.; Dunn, J.; Behan, R.; Mulrooney, R. C.; Callan, J. F. Eur. Polym. J. 2009, 45, 272–277. 18. Synthesis of compound 3. Compound 2 (2.0 g, 6.57 mmol) was dissolved in an excess of 1,2-diaminoethane (10 mL) and heated at 80 °C for 18 h. The mixture was poured slowly into H2O and the resulting precipitate collected by filtration and dried in vacuo to yield the product as a yellow solid (80% yield). Mp 173– 175 °C. 1H NMR (CDCl3, 400 MHz) d (ppm): 1.31 (t, 3H, J = 7.0 Hz, CH3), 1.38– 1.50 (br s, 2H, NH2), 3.17 (m, 2H, NCH2), 3.41 (q, 2H, J = 5.6 Hz, NCH2), 4.22 (q, 2H, J = 7.0 Hz, NCH2CH3), 6.15 (s, 1H, NH), 6.69 (d, 1H, J = 8.4 Hz, Ar-H), 7.61 (t, 1H, J = 8.4 Hz, Ar-H), 8.16 (d, 1H, J = 8.0 Hz, Ar-H), 8.45 (d, 1H, J = 8.0 Hz, Ar-H), 8.58 (1H, d, J = 8.5 Hz, Ar-H). Anal. Calcd for C16H17N3O2: C 67.83; H 6.05; N 14.83. Found: C 67.90; H 6.15; N 14.93.

19. Gutsche, C. D.; Iqbal, M.; Steward, D. J. Org. Chem. 1986, 51, 742–745. 20. Synthesis of compound 7. A solution of 6 (2.50 g, 4.2 mmol) and 1,8-diamino3,6-dioxaoctane (0.62 g, 4.2 mmol) in MeOH/toluene (400 mL) was refluxed with continuous stirring for 24 h. The mixture was cooled to room temperature, the solvent removed under reduced pressure and the white crystalline product 7 was obtained by column chromatography using acetone/ n-hexane (9:1) as eluent (65% yield). Mp. 276–278 °C. 1H NMR (CDCl3, 400 MHz) d (ppm): 3.25 (d, 4H, J = 13.0 Hz, ArCH2Ar), 3.43 (s, 4H, OCH2CH2O), 3.46 (m, 4H, NHCH2CH2O), 3.55 (t, 4H, J = 5.47 Hz, NHCH2CH2O) 4.01 (d, 4H, J = 13.0 Hz, ArCH2Ar), 4.33 (s, 4H, OCH2CO), 6.48–6.61 (m, 8H, ArH), 6.73 (s, 2H, ArOH), 6.93 (d, 4H, J = 7.6 Hz, ArH), 8.08 (t, J = 5.4 Hz, 2H, NH). 13C NMR (CDCl3, 400 MHz) : 31.39; 30.62; 70.04; 70.49; 75.29; 120.12; 128.81; 129.23; 129.51; 132.35; 133.03; 152.63; 168.76. Anal. Calcd for C38H40N2O8: C 69.92; H 6.18; N 4.29. Found: C 69.98; H 6.25; N 4.34. 21. Synthesis of compound 8. A mixture of 7 (1.0 g, 1.53 mmol) and HMTA(hexamethylenetetraamine) (8.58 g, 61.2 mmol) in TFA (10 ml) was refluxed for 24 h. The mixture was poured into 60 ml of acid (HCl)/H2O and extracted with CHCl3 (3  40 mL). The chloroform solution was washed with H2O (3  50 mL) and dried over Na2SO4. Concentration of the solution followed by dilution with hexane gave a precipitate which was recrystallized from CHCl3/hexane as a light yellow solid (Yield 70%). Mp. 164–167 °C. 1H NMR (CDCl3, 400 MHz) d (ppm): 3.54–3.58 (m, 8H, ArCH2Ar, OCH2CH2O), 3.67–3.73 (m, 8H, NHCH2CH2O, NHCH2CH2O), 4.27 (d, 4H, J = 13.0 Hz, ArCH2Ar), 4.55 (s, 4H, OCH2C@O), 6.71–6.75 (m, 2H, ArH), 6.80 (d, 4H, J = 7.6 Hz, ArH), 7.47 (s, 2H, ArOH), 7.69 (s, 4H, ArH), 7.89 (t, 2H, J = 5.2 Hz, NH) 9.86 (s, 2H, CHO). 13C NMR (CDCl3, 400 MHz) d (ppm): 20.91; 31.27; 39.64; 69.75; 70.40; 75.32; 126.42; 128.84; 129.52; 130.01; 131.31; 131.59; 152.39; 158.49; 168.16; 191.00. Anal. Calcd for C40H40N2O10: C 68.78; H 5.69; N 3.95. Found: C 68.85; H 5.74; N 3.99. 22. Synthesis of compound 9. To a stirred solution of 8 (0.5 g, 0.70 mmol) in MeOH (10 ml) was added a solution of 3 (2.0 g, 3.5 mmol) in THF (10 ml) and the mixture refluxed for 6 h to give a light yellow precipitate. The precipitate was filtered and washed with MeOH and Et2O. The residue was recrystallized from CHCl3/n-hexane to furnish compound 9. Yield (60%). Mp. 198–201 °C. IR (cm 1): 1638, 1670 (C@O). 1H NMR (CDCl3, 400 MHz) d (ppm): 1.30 (t, 6H, J = 7.0 Hz, CH3), 3.45 (d, 4H, J = 13.0 Hz, ArCH2Ar), 3.57 (s, 4H, OCH2CH2O), 3.64–3.67 (m, 4H, NHCH2CH2O), 3.70–3.75 (m, 4H, ArHNHCH2), 3.99 (t, 4H, J = 5.6 Hz, NCH2), 4.18–4.26 (m, 12H, ArCH2Ar, NHCH2CH2O, NCH2CH3), 4.53 (s, 4H, OCH2CO), 5.90 (t, 2H, J = 5.2 Hz, ArHnaphthNH), 6.65 (t, 2H, J = 7.6 Hz, ArH), 6.76 (d, 4H, J = 7.6 Hz, ArH), 6.81 (d, 2H, J = 8.6 Hz, ArHnaphth), 7.53 (s, 4H, ArH), 7.56 (t, 2H, J = 7.4 Hz, ArHnaphth), 7.89 (t, J = 5.4 Hz, 2H, CONH), 8.12 (d, 2H, J = 8.6 Hz, ArHnaphth), 8.27 (s, 2H, CH@N), 8.48 (d, 2H, J = 8.6 Hz, ArHnaphth), 8.55 (d, 2H, J = 7.4 Hz, ArHnaphth). 13C NMR (CDCl3, 400 MHz) d: 13.66; 13.72; 31.22; 35.48; 39.72; 44.57; 59.43; 69.94; 70.40; 75.32; 104.91; 110.90; 120.75; 123.45; 126.14; 126.18; 126.23; 128.13; 128.87; 129.48; 129.73; 129.97; 131.28 131.94; 134.52; 149.63; 152.57; 155.51; 162.89; 164.12; 164.62; 168.42. Anal. Calcd for C72H70N8O12: C 69.77; H 5.69; N 9.04. Found: C 69.84; H 5.75; N 9.12 23. Singh, N.; Kaur, N.; McCaughan, B.; Callan, J. F. Tetrahedron Lett. 2010, 51, 3385– 3387. 24. Ocak, U.; Ocak, M.; Surowiec, K.; Liu, X.; Bartsch, R. A. Tetrahedron 2009, 65, 7038–7047. 25. Bourson, J.; Valeur, B. J. Phys. Chem. 1989, 93, 3871–3876. 26. Ocak, U.; Ocak, M.; Surowiec, K.; Bartsch, R. A.; Gorbunova, M. G.; Tu, C.; Surowiec, M. A. J. Incl. Phenom. Macrocyclic Chem. 2009, 63, 131–139. 27. Valeur, B. Molecular Fluorescence Principles and Applications; Wiley-VCH: 2001.