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Dyes and Pigments 99 (2013) 90e98

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Dyes and Pigments

journal homepage: www.elsevier .com/locate/dyepig

The synthesis of novel unmetallated and metallated phthalocyaninesincluding (E)-4-(3-cinnamoylphenoxy) groups at the peripheralpositions and photophysicochemical properties of their zincphthalocyanine derivatives

Asiye Nas a, Nuran Kahriman a, Halit Kantekin a,*, Nurettin Yaylı a, Mahmut Durmus b

aDepartment of Chemistry, Karadeniz Technical University, 61080 Trabzon, TurkeybGebze Institute of Technology, Department of Chemistry, PO Box 141, Gebze 41400, Kocaeli, Turkey

a r t i c l e i n f o

Article history:Received 4 March 2013Received in revised form10 April 2013Accepted 15 April 2013Available online 23 April 2013

Keywords:Microwave processingChalconeMetallophthalocyaninePhotophysicalPhotochemicalSinglet oxygen

* Corresponding author. Tel.: þ90 462 377 25 89; fE-mail address: halit@ktu.edu.tr (H. Kantekin).

0143-7208/$ e see front matter � 2013 Published byhttp://dx.doi.org/10.1016/j.dyepig.2013.04.014

a b s t r a c t

This paper reports on the synthesis and characterization of new peripherally tetra-substituted metal-free(4), nickel(II) (5), zinc(II) (6), cobalt(II) (7), copper(II) (8), lead(II) (9) and octa-substituted zinc(II) (12)phthalocyanines containing (E)-4-(3-cinnamoylphenoxy) groups for the first time. Synthesized com-pounds have been characterized by electronic absorption, FT-IR, 1H NMR, 13C NMR, elemental analysis,mass spectra and thermogravimetric analysis. The photophysical (fluorescence quantum yields andlifetimes) and photochemical (singlet oxygen generation and photodegradation under light irradiation)properties of zinc phthalocyanine derivatives (6 and 12) were investigated in dimethylsulfoxide. Thefluorescence quenching behavior of zinc phthalocyanine derivatives (6 and 12) by 1,4-benzoquinone wasalso examined in same solution.

� 2013 Published by Elsevier Ltd.

1. Introduction

Phthalocyanines were incidentally discovered in London byBraun and Tcherniac in 1907 and were first used by Professor Lin-stead at the Imperial College of Science and Technology in 1933 [1].

Since their first synthesis early in the last century, phthalocya-nines, both a class of organic compounds and also called as blueegreen products later, have been of great interest to chemists, physi-cists and industrial scientists. Because of this great and increasinginterest, phthalocyanines are continuously produced with incre-mental quantity, variety and functionality year after year. Theseproductions have brought about outstanding achievement andspectacular changes in the way we think and work for scientificinnovation. In literature, well-oriented and documented phthalocy-anine researches have continuously increased, broadened and citedto serve several purposes by researchers. These innovative worksensure the producing brand new knowledge, the efficient use ofsources and thus they contribute to current economic development.

ax: þ90 462 325 31 96.

Elsevier Ltd.

The phthalocyanine macrocycle was assumed to exhibit aro-matic behavior like porphyrin macrocycle, because of its planarconjugated array of 18-p electrons, as predicted by Huckel’s theoryof aromaticity, published only a few years previously [2].

The large number of appreciable applications of phthalocya-nines arises from their aforementioned unique 18-p electron con-jugated system, which makes them present high thermal andchemical stability and noteworthy photoelectric properties [3,4].Other applications of these blue-green compounds have beenintensively investigated, such as solar cells [5e7], LangmuireBlodgett films [8,9], liquid crystals [10e12], optical applications[13,14], semiconductor materials [15,16] in addition to particularlytreatment of cancer by photodynamic therapy (PDT) [17e20].

Photodynamic therapy (PDT) is a sophisticated innovativetreatment that uses special form of light-activated drugs, called asphotosensitizing/photosensitizer agents, accompanied by light todetect and destroy cancer cells [21]. Metallophthalocyanines havealso been introduced as photosensitizers for PDTof cancer in recentyears since diamagnetic central metals, such as Zn or Mg enhancephototoxicity of phthalocyanines [22,23]. Compared with conven-tional treatments, the extraordinary advantage of PDT is that it can

A. Nas et al. / Dyes and Pigments 99 (2013) 90e98 91

destroy cancer cells and treat symptomatic tissues selectively anddoes not harm the normal surrounding tissues severely [24].

A significant characteristic disadvantage of phthalocyanines istheir nominal solubility in most known solvents or aqueous media.Introduction of peripheral substituents on the ring increases thesolubility dramatically. The presence of bulky or long chain alkylsubstituents into the peripheral or non-peripheral positions of thephthalocyanines increases solubility in non-polar solvents [25,26].

The main purpose of this study is to synthesize and characterizesymmetrical tetra-substituted metal-free (4) and metal-lophthalocyanines [Ni(II) (5), Zn(II) (6), Co(II) (7), Cu(II) (8), Pb(II)(9) and octa-substituted Zn(II) (12)]. Furthermore, we examined thethermal stability of novel phthalocyanines using by thermogravi-metric analysis (TGA). The synthesized compounds have very goodsolubility in common organic solvents such as chloroform,dichloromethane, THF, DMSO, DMF and pyridine. The photo-physical and photochemical properties of the zinc phthalocyaninederivatives (6 and 12) were investigated in this study. The desig-nations of these properties are very useful for the determination ofthe PDT activity of photosensitizer compounds. Only zinc phtha-locyanine derivatives (6 and 12) were studied for this purpose inthis study because the phthalocyanines containing zinc atoms intheir cavity are most suitable among the phthalocyanine de-rivatives due to the d10 electronic configuration of zinc atoms.

2. Experimental

2.1. Materials

All reagents and solvents were dried and purified as describedby Perrin and Armarego prior to use [27]. (E)-1-(3-hydroxyphenyl)-3-phenylprop-2-en-1-one (1) [28], 4-nitro phthalonitrile (2) [29]and 4,5-dichlorophthalonitrile (10) [30] were prepared and puri-fied according to the literatures. All other reagents and solventswere reagent grade quality and were obtained from commercialsuppliers.

The photophysical and photochemical parameters were sup-plied as supplementary information.

2.2. Synthesis

2.2.1. (E)-4-(3-cinnamoylphenoxy)phthalonitrile (3)Compound 1 ((E)-1-(3-hydroxyphenyl)-3-phenylprop-2-en-1-

one) (2.40 g, 10.7 mmol) and compound 2 (4-nitro phthalonitrile)(1.85 g, 10.7 mmol) were dissolved in dry DMF (30 mL) under anitrogen atmosphere at 50 �C. After 15 min of stirring, finelyground anhydrous K2CO3 (5.9 g, 42.8 mmol) was added portion-wise over a period of 2 h. Thereafter, the reaction mixture left tostir under N2 atmosphere at this temperature for 5 days. Themixture was cooled to the room temperature and poured into ice-water (100 mL) and stirred for 30 min. The yellow product wasfiltered off and recrystallized from ethanol. Yield: 1.5 g (40%), m.p.:115e118 �C. Calcd. for C23H14N2O2: C 78.84%, H 4.03%, N 8.00%.Found: C 78.80%, H 4.12, N 8.04%. FT-IR nmax/cm�1 (KBr pellet):3068 (AreH), 2967e2912 (Aliph. CeH), 2231 (C^N), 1664 (C]O),1596, 1578, 1483, 1308, 1281, 1249, 1087, 955, 765, 688. 1H NMR(CDCl3) (d: ppm): 7.98e6.86 (ArH, 14H, m). 13C NMR (CDCl3) (d:ppm): 189.19, 161.54, 154.31, 146.25, 135.89, 135.74, 134.67, 131.29,130.94, 128.89, 128.25, 126.42, 125.55, 125.19, 122.07, 120.66,119.75, 117.71, 115.66, 115.22, 109.48. MS (ESþ), m/z: Calc.: 350.37;Found: 351.19 [MþH]þ.

2.2.2. Metal-free phthalocyanine (4)The mixture of (E)-4-(3-cinnamoylphenoxy)phthalonitrile (3)

(0.2 g, 0.5708 mmol), and two drops of 1,8-diazabicyclo[5.4.0]

undec-7-ene (DBU) in 3 mL of dry n-pentanol was heated at 160 �Cin a sealed tube and stirred for 24 h under a nitrogen atmosphere.The crude product was precipitated by the addition of 20 mL ofethanol and refluxed with ethanol, and then treated with severaltimes hot ethanol, distilled water, methanol and diethyl ether. Afterdrying under vacuum, this compound was purified by preparativethin layer chromatography (TLC) using chloroform-methanol (92:8)solvent system as eluent. Yield: 48 mg (24%), m.p.: 365e434 �C(decomposition). Calcd. for C92H58N8O8.H2O: C 77.73%, H 4.25%, N7.88%. Found: C 77.27%, H 4.88%, N 7.55%. FT-IR nmax/cm�1 (KBrpellet): 3054 (AreH), 2924e2851 (Aliph. CeH), 1728 (C]O), 1604,1577, 1476, 1358, 1241, 1033, 942, 821, 761. 1H NMR (CDCl3) (d:ppm): 7.70e6.97 (ArH, 56H, m). 13C NMR (CDCl3) (d: ppm): 188.16,167.45, 160.27, 154.15, 140.41, 136.12, 134.92, 133.33, 131.19, 129.25,128.82, 127.16, 125.05, 125.67, 122.88, 121.68, 119.21, 118.97, 113.07,108.73, 106.05. UVeVis (CHCl3): l, nm (log 3): 707 (5.20), 674 (5.20),644 (5.07), 617 (4.94), 389 (5.20). MS (ESþ), m/z: Calc.: 1403.52;Found: 1427.44 [MþNaþH]þ.

2.2.3. General procedures for metallophthalocyanine derivatives(5e9)

Compound 3 ((E)-4-(3-cinnamoylphenoxy)phthalonitrile)(0.2 g, 0.5708 mmol) was irradiated with anhydrous metal salt(NiCl2 (18.6 mg, 0.1427 mmol), Zn(CH3COO)2 (26 mg, 0.1427 mmol),CoCl2 (18.6 mg, 0.1427 mmol), CuCl2 (19.2 mg, 0.1427 mmol), PbO(32 mg, 0.1427 mmol)) in the presence of two drops of DBU in 2 mLof 2-(dimethylamino)ethanol in a microwave oven at 175 �C,350 W, for a few minutes. After cooling, 20 mL of ethanol wasadded to this mixture and stirred overnight. This mixture wasfiltered off, refluxedwith ethanol. Then it was washed several timeswith hot ethanol, distilled water and diethyl ether. After dryingunder vacuum over P2O5, it was purified by preparative thin layerchromatography (TLC) using chloroform: methanol solvent system(97:3 for compound 5, 95:5 for compound 6, 96:4 for compound 7,95:5 for compound 8 and 97:3 for compound 9) as eluent.

2.2.3.1. Nickel(II) phthalocyanine (5). Yield: 37 mg (18%), m.p.:335e415 �C (decomposition). Calcd. for C92H56N8NiO8: C 75.68%, H3.87%, N 7.67%. Found: C 75.26%, H 3.20%, N 7.93%. FT-IR nmax/cm�1

(KBr pellet): 3060 (AreH), 2917e2846 (Aliph. CeH), 1663 (C]O),1578, 1472, 1434, 1307, 1240, 1088, 1059, 952, 877, 761, 699. 1H NMR(CDCl3) (d: ppm): 8.03e6.87 (ArH, 56H, m). 13C NMR (CDCl3) (d:ppm): 189.17, 161.29, 159.45, 154.33, 147.95, 133.80, 134.29, 131.36,130.79, 128.93, 124.43, 123.92, 121.80, 120.73, 119.46, 117.79, 106.16.UVeVis (CHCl3): l, nm (log 3): 676 (5.24), 632 (5.10), 395 (5.20). MS(ESþ), m/z: Calc.: 1460.20; Found: 1499.12 [MþK]þ.

2.2.3.2. Zinc(II) phthalocyanine (6). Yield: 56 mg (27%), m.p.: 331e406 �C (decomposition). Calcd. for C92H56N8O8Zn: C 75.33%, H3.85%, N 7.64%. Found: C 74.44%, H 3.96%, N 6.97%. FT-IR nmax/cm�1

(KBr pellet): 3054 (AreH), 2921e2846 (Aliph. CeH), 1662 (C]O),1575, 1479,1392,1241,1087,1043, 947, 759, 686. 1H NMR (CDCl3) (d:ppm): 7.78e6.92 (ArH, 56H, m). 13C NMR (CDCl3) (d: ppm): 187.65,160.13, 159.76, 155.27, 148.36, 134.83, 132.74, 130.85, 129.09, 128.82,124.05, 122.54, 120.86, 118.64, 114.26, 110.42, 105.00. UVeVis(CHCl3): l, nm (log 3): 683 (5.22), 616 (4.67), 325 (5.18). MS (ESþ),m/z: Calc.: 1466.90; Found: 1466.03 [M]þ.

2.2.3.3. Cobalt(II) phthalocyanine (7). Yield: 33 mg (16%), m.p.:295e400 �C (decomposition). Calcd. for C92H56CoN8O8: C 75.66%, H3.86%, N 7.67%. Found: C 74.91%, H 4.12%, N 7.47%. FT-IR nmax/cm�1

(KBr pellet): 3061 (AreH), 2923e2851 (Aliph. CeH), 1663 (C]O),1597, 1577, 1474, 1331, 1242, 1092, 956, 761, 688. UVeVis (CHCl3): l,nm (log 3): 675 (5.25), 615 (4.94), 402 (5.13). MS (ESþ), m/z: Calc.:1460.44; Found: 1483.72 [MþNa]þ.

A. Nas et al. / Dyes and Pigments 99 (2013) 90e9892

2.2.3.4. Copper(II) phthalocyanine (8). Yield: 50 mg (24%), m.p.:327e366 �C (decomposition). Calcd. for C92H56CuN8O8: C 75.42%, H3.85%, N 7.65%. Found: C 75.53%, H 4.07%, N 7.22%. FT-IR nmax/cm�1

(KBr pellet): 3060 (AreH), 2987e2922 (Aliph. CeH), 1663 (C]O),1597, 1476, 1331, 1242, 1039, 952, 760, 688. UVeVis (CHCl3): l, nm(log 3): 685 (5.19), 631 (5.00), 412 (5.08). MS (ESþ), m/z: Calc.:1465.05; Found: 1465.15 [M]þ.

2.2.3.5. Lead(II) phthalocyanine (9). Yield: 46 mg (20%), m.p.: 341e395 �C (decomposition). Calcd. for C92H56N8O8Pb: C 68.69%, H3.51%, N 6.97%. Found: C 68.59%, H 3.42%, N 6.83%. FT-IR nmax/cm�1

(KBr pellet): 3042 (AreH), 2994e2918 (Aliph. CeH), 1707 (C]O),1612, 1512, 1425, 1247, 1175, 1114, 1033, 942, 821, 741. 1H NMR(CDCl3) (d: ppm): 7.95e6.93 (ArH, 56H, m). 13C NMR (CDCl3) (d:ppm): 188.64, 162.14, 158.27, 156.39, 149.93, 136.52, 133.26, 130.18,128.64, 127.10, 126.45, 120.66, 119.26, 115.47, 109.36, 106.27. UVeVis(CHCl3): l, nm (log 3): 720 (5.22), 648 (4.61), 400 (4.97). MS (ESþ),m/z: Calc.: 1608.71; Found: 1608.84 [M]þ.

2.2.4. 4,5-Bis(3-cinnamoylphenoxy)phthalonitrile (11)Compound 1 ((E)-1-(3-hydroxyphenyl)-3-phenylprop-2-en-1-

one) (1.0 g, 4.46 mmol) and compound 10 (4,5-dichlorophthalonitrile) (0.44 g, 2.23 mmol) were dissolved in dry DMF(15 mL) under N2 atmosphere. After 15 min of stirring, finelyground anhydrous K2CO3 (0.92 g, 6.69 mmol) was added portion-wise over a period of 2 h. Thereafter, the reactionmixture left to stirunder N2 atmosphere at this temperature for 5 days. The mixturewas poured into ice-water (100 mL) and stirred for 30 min. Theyellow precipitate was filtered off, washed with distilled water,recrystallized from ethanol. Yield: 0.6 g (47%), m.p.: 121e124 �C.Calcd. for C38H24N2O4: C 79.71%, H 4.22%, N 4.89%. Found: C 79.42%,H 3.96%, N 4.35%. FT-IR nmax/cm�1 (KBr pellet): 3063e3025 (AreH),2942e2925 (Aliph. CeH), 2233 (C^N), 1666 (C]O), 1574, 1449,1398,1233,1075, 980, 761, 688. 1H NMR (CDCl3) (d: ppm): 7.91e7.27(ArH, 24H, m). 13C NMR (CDCl3) (d: ppm): 188.94, 154.65, 151.28,145.99,140.59,134.46,130.96,130.85,128.64,128.29,127.59,123.74,123.14, 121.16, 119.04, 114.72, 111.35. MS (ESþ), m/z: Calc.: 572.62;Found: 573.45 [MþH]þ.

2.2.5. Zinc(II) phthalocyanine (12)The mixture of 4,5-bis(3-cinnamoylphenoxy)phthalonitrile (11)

(0.3 g, 0.5239 mmol), anhydrous zinc acetate (24 mg, 0.1309 mmol)and two drops of DBU in 3 mL of dry n-pentanol was heated andstirred at 160 �C in a sealed glass tube for 24 h under a nitrogenatmosphere. The resulting green suspension was cooled to theroom temperature and the crude product was precipitated by theaddition of 20 mL of ethanol, filtered off, refluxed with ethanol, andthen washed several times with hot ethanol, distilled water anddiethyl ether. After drying under vacuum, this compound was pu-rified by preparative thin layer chromatography (TLC) usingchloroform-methanol (93:7) solvent system as eluent. Yield: 75 mg(24%), m.p.: 389e411 �C (decomposition). Calcd. for C152H96N8O16Zn: C 77.49%, H 4.11%, N 4.76%. Found: C 77.27%, H 4.58%, N 4.55%.FT-IR nmax/cm�1 (KBr pellet): 3054e3027 (AreH), 2918e2846(Aliph. CeH), 1663 (C]O), 1596, 1575, 1435, 1331, 1279, 1029, 760,687, 565. 1H NMR (DMSO-d6) (d: ppm): 7.81e7.43 (ArH, 96 H, m).13C NMR (DMSO-d6) (d: ppm): 187.32,156.38,150.93,147.66,139.83,135.33, 130.22, 129.71, 127.96, 126.21, 125.73, 121.53, 120.55, 119.31.UVeVis (CHCl3): l, nm (log 3): 690 (5.26), 626 (4.67), 323 (5.20). MS(ESþ), m/z: Calc.: 2355.87; Found: 2394.78 [Mþ K]þ.

3. Results and discussion

The synthetic route depicted in Scheme 1 is the formation of thephthalonitrile derivative 3. This nucleophilic aromatic nitro

displacement of (E)-1-(3-hydroxyphenyl)-3-phenylprop-2-en-1-one (1) [28] with 4-nitro phthalonitrile (2) [29] was accom-plished in dry DMF and anhydrous K2CO3 as a strong base at 50 �Cunder a nitrogen atmosphere. This phthalonitrile derivative (3) wasobtained in moderate yields (40%) and was characterized bymiscellaneous characterization methods (e.g. NMR, FT-IR, massspectral data, elemental analysis and thermal analysis). In the FT-IRspectrum, the formation of compound 3 was clearly confirmed bythe disappearance of the eOH band at 3214 cm�1 and appearanceof the sharp peak for the eC^N vibration at 2231 cm�1. The 1HNMR spectrum of compound 3was recorded in CDCl3 (Fig. S1). Thechemical shift of eOH proton in precursor compound 1 atd¼ 9.84 ppm disappeared after the formation of dinitrile com-pound 3. Aromatic protons of (E)-4-(3-cinnamoylphenoxy)phtha-lonitrile (3) were observed at between 7.98 and 6.86 ppm. 13C NMRspectrum of this compound obviously specified the presence ofdinitrile carbon atoms with peaks at d¼ 115.66 and 115.22 ppm. Inthe mass spectrum of compound 3, the expected molecular ionpeak was observed at m/z: 351.19 [MþH]þ (Fig. S2). The elementalanalysis results of compound 3 were in accordance with its calcu-lated results.

Peripherally tetra-substituted metal-free phthalocyanine (4)was prepared by cyclotetramerization of (E)-4-(3-cinnamoylphenoxy) substituted phthalonitrile derivative (3). The reactionwas carried out at 160 �C for 24 h under a nitrogen atmosphere andgave yields of about 24%. In the FT-IR spectrum of compound 4, thesharp band for the eC^N groups of phthalonitrile derivative (3) ataround 2231 cm�1 disappeared after conversion into metal-freephthalocyanine (4). In the 1H NMR spectrum of this compound,the inner core proton signals could not be observed because of thestrong aggregation [31]. In the 1H NMR spectrum of compound 4,aromatic proton signals were observed at between 7.70 and6.97 ppm. In the mass spectrum of compound 4, the molecular ionpeak was observed at m/z: 1427.44 [MþNaþH]þ. The elementalanalysis results of compound 4 were in accordance with its calcu-lated results with one mole water.

The formation of Ni(II) (5), Zn(II) (6), Co(II) (7), Cu(II) (8), Pb(II)(9) metallophthalocyanines were accomplished with a percentyield of 18, 27, 16, 24, and 20%, respectively. Metallophthalocyanines (5e9) were obtained from phthalonitrile derivative (3) inpresence of the anhydrous NiCl2, Zn(CH3COO)2, CoCl2, CuCl2 andPbO in 2-(dimethylamino)ethanol (DMAE) using microwave irra-diation in the range of 6e9 min (Scheme 1). In the FT-IR spectra ofmetallophthalocyanines (5e9), the eC^N stretching band ofphthalonitrile derivative (3) at around 2231 cm�1 disappeared afterconversion. The 1H NMR spectra of these compounds were almostidentical as expected. In the mass spectra of compounds 5e9,observed peaks at m/z: 1499.12 [Mþ K]þ, 1466.03 [M]þ, 1483.72[MþNa]þ, 1465.15 [M]þ and 1608.84 [M]þ, support the proposedformula of these novel phthalocyanines, respectively. Theelemental analysis results of compounds 5e9 were in accordancewith their calculated results.

The synthetic route depicted in Scheme 2 is the formation of thephthalonitrile derivative 11. This nucleophilic aromatic substitutionof (E)-1-(3-hydroxyphenyl)-3-phenylprop-2-en-1-one (1) [28]with 4,5-dichlorophthalonitrile (10) [30] was accomplished in thepresence of anhydrous K2CO3 as strong base in dry DMF at 50 �Cunder a nitrogen atmosphere with the yield of 47% after recrys-tallization from ethanol. This phthalonitrile derivative (11) wascharacterized by several characterization methods such as NMR,FT-IR, mass spectral data and elemental analysis in addition tothermal analysis. In the FT-IR spectrum, the formation of compound11 was clearly confirmed by the disappearance of the eOH band at3214 cm�1 and appearance of eC^N band at 2233 cm1. In the 1HNMR spectrum of 11, the chemical shift of eOH proton in precursor

O

CN

CNO

OHO

CN

CNO2N

dry DMF

50 oC

N NN

N

N N N

N

O

O

O

O

i. for 4160 0CDBU

(1)(2) (3)

ii.f or 5-9175 0C, 350 WDMAE, MW

MO

O

O

O

Metal 2H Ni Zn Co Cu Pb Compound 4 5 6 7 8 9

Scheme 1. Synthesis route of peripherally tetra-substituted metal-free (4) and metallophthalocyanines (5e9). i: n-Pentanol, DBU, 160 �C; ii: DMAE, 175 �C, 350 W.

A. Nas et al. / Dyes and Pigments 99 (2013) 90e98 93

compound 1 at d¼ 9.84 ppm disappeared after the formation ofdinitrile compound 11. The 1H NMR spectrum of compound 11 wasrecorded in CDCl3. Aromatic protons were observed between 7.91and 7.27 ppm. 13C NMR spectrum of this compound clearly indi-cated the presence of dinitrile carbon atoms with peaks at 114.72and 111.35 ppm. In the mass spectrum, compound 3 the expectedmolecular ion peak was observed at m/z: 573.45 [MþH]þ. Theelemental analysis results of compound 11were in accordancewithits calculated results.

Cyclotetramerization of phthalonitrile derivative (11) into octa-substituted zinc(II) phthalocyanine (12) was carried out in aSchlenk tube in the presence of the anhydrous Zn(CH3COO)2 in dryn-pentanol and 2e3 drops of DBU at 160 �C for 24 h under a ni-trogen atmosphere with a percent yield of 24% (Scheme 2). Adiagnostic feature of the octa-substituted zinc(II) phthalocyanine(12) formation from the phthalonitrile derivative (11) was disap-pearance of the sharp band for eC^N groups of compound 11 at2233 cm�1 in the FT-IR spectrum. The 1H NMR spectrum of thiscompound was almost identical as expected. 1H NMR spectrum of12 showed new signals at d¼ 7.81e7.43 ppm belonging to aromaticprotons. In the mass spectrum of compound 12, the molecular ion

peak was observed at m/z: 2394.78 [MþK]þ. The elemental anal-ysis result of compound 12 was in accordance with its calculatedresult.

The electronic absorption spectra of metal-free (4) and metal-lophthalocyanines (5e9,12) in chloroform at room temperature aredepicted in Figs. 1e3. The spectra of metallophthalocyanine com-plexes consist of an intense absorption band in the visible regiontraditionally near 670 nm called the Q band and generally a weakerband near 340 nm called the Soret or B band, both being p/p*

transitions. Unmetallated Pcs exhibits D2h symmetry. Metallationwhich maintains the planarity of the molecule increases the sym-metry to D4h [32]. The introduction of a metal ion inside the cavityresults slightly blue shift wavelength of the Q band due to theintroduction of a metal ion reduces electron density. It has beendemonstrated that the more electronegative metal ion in thephthalocyanine cavity causes the more blue shift for the wave-length of Q band of phthalocyanines [32]. For compound 4, splittedQ band was observed at 674 and 707 nmwith the shoulders at 644and 617 nm as a result of D2h symmetry. The Soret band (B band)remained at 389 nm (Fig. 1). In the UVeVis absorption spectra ofnickel(II) 5, zinc(II) 6, cobalt(II) 7, copper(II) 8, lead(II) 9 and octa-

Scheme 2. Synthesis route of peripherally octa-substituted Zn(II) phthalocyanine (12). iii: n-Pentanol, DBU, 160 �C.

A. Nas et al. / Dyes and Pigments 99 (2013) 90e9894

substituted zinc(II) (12) phthalocyanines. The intense Q absorptionsat lmax: 676, 683, 675, 685, 720, and 690 nm with weaker absorp-tions at lmax: 632, 616, 615, 631, 648, and 626 nm were observed,respectively in the UVeVis absorption spectra (Figs. 1e3). Besides,the UVeVis spectra of 5, 6, 7, 8, 9 and 12 in chloroform were alsoobserved the intense B absorptions at lmax: 395, 325, 402, 412, 400,and 323 nm, respectively as expected.

Aggregation is very important for the determination of the PDTactivity of the photosensitizers. The aggregation behaviors of thetetra- and octa-substituted zinc phthalocyanines (6 and 12) werestudied and compared in DMSO. While the tetra-substituted zincphthalocyanine (6) did not form aggregates, the octa-substitutedcounterpart (12) showed a little aggregation in this solvent. Theaggregation behavior of tetra-substituted zinc phthalocyanine (6)

Q Band

B Band

0.5

1

1.5

2

0 200 300 400 500 600 700 800

10

-5

ε / d

m3

mo

l-1

cm

-1

λ ( nm )

Fig. 3. UVeVis spectra of compounds 6 ( ) and 12 ( ) in chloroform.

1.6

Q Band

B Band

0.5

1

1.5

2

0 200 300 400 500 600 700 800

10

-5

ε / d

m3 m

ol-

1 c

m-1

λ ( nm )

Fig. 1. UVeVis spectra of compounds 4 ( ) and 5 ( ) in chloroform.

A. Nas et al. / Dyes and Pigments 99 (2013) 90e98 95

was also determined at the increasing of the concentration. TheBeereLambert law was obeyed for this complex at concentrationsranging from 1.2�10�5 to 2.0�10�6 M. The tetra-substitutedphthalocyanine complex (6) did not exhibit aggregation at stud-ied concentrations ranging in DMSO (Fig. 4).

The fluorescence behaviors of the tetra- and octa-substitutedzinc phthalocyanines (6 and 12) were examined in DMSO at roomtemperature. The UVeVis absorption, fluorescence emission andexcitation spectra of these phthalocyanines were given in Fig. 5 fortetra-substituted phthalocyanine (6) as an example. The fluores-cence excitation and emission maximum bands were observed atlex¼ 680 and lem¼ 688 nm for compound 6 and lex¼ 681 andlem¼ 687 nm for compound 12. The observed Stokes shift isapproximately 8 nm for both compounds which is typical formetallophthalocyanines. The fluorescence emission bands werered-shifted at approximately 8 nm compared to unsubstituted zincphthalocyanine (lem¼ 680 nm) due to the substitution of thephthalocyanine framework with (E)-(3-cinnamoylphenoxy) groupsin DMSO. The excitation spectra of the studied zinc phthalocyaninecompounds (6 and 12) were similar to absorption spectra of thesecompounds and these spectra were mirror images of the emissionspectra of these compounds in DMSO (Fig. 5 as an example forcompound 6). This suggests that the nuclear configurations of theground and excited states of these compounds are similar and notaffected by excitation study.

The fluorescence quantum yield (FF) values of the studied tetra-and octa-substituted zinc phthalocyanines (6 and 12) were studiedand compared in DMSO. The FF value of tetra-substituted zinc

Q Band

B Band

0.5

1

1.5

2

0 200 300 400 500 600 700 800

λ ( nm )

10

-5

ε / d

m3 m

ol-

1 c

m-1

Fig. 2. UVeVis spectra of compounds 7 ( ), 8 ( ) and 9 ( ) in chloroform.

phthalocyanine (6) (FF¼ 0.15) is higher than octa-substituted zincphthalocyanine (12) (FF¼ 0.035). It can be attributed the aggre-gation of the octa-substituted zinc phthalocyanine (12) in DMSO. Itis known that the aggregation (especially H-type aggregation forphthalocyanine compounds) is lower the photoactivity such asfluorescence behavior of the molecules. The substitution of the (E)-(3-cinnamoylphenoxy) groups on the phthalocyanine frameworkalso decreased the FF values (the FF value of the unsubstituted zincphthalocyanine is 0.20 in DMSO [33]). Especially a great decreasingwas observed for octa-substituted zinc phthalocyanine due to bothsubstitution and aggregation effects. The fluorescence lifetime (sF),the natural radiative lifetime (s0) and the rate constants for fluo-rescence (kF) values were also measured and compared in DMSO.The sF value of octa-substituted zinc phthalocyanine (12)(sF¼ 0.602 ns) is lower than sF value of tetra-substituted zincphthalocyanine (6) (sF¼ 1.499 ns) due to the aggregation of theocta-substituted zinc phthalocyanine (12) compound in DMSOagain. While the sF value of compound 6 is higher, the sF value ofcompound 12 is lower than the sF value unsubstituted zincphthalocyanine (sF¼ 1.22 ns in DMSO [34]) due to the aggregationeffect again. The s0 value of tetra-substituted zinc phthalocyanine(6) (s0¼ 9.99 ns) is lower than the s0 value of octa-substituted zincphthalocyanine (12) (s0¼17.20 ns) and both studied compoundsshow higher s0 values compared to unsubstituted zinc phthalocy-anine (s0¼ 6.80 ns [34]) in DMSO. The kF values of the both studied

0

0.4

0.8

1.2

300 400 500 600 700 800

Wavelength (nm)

Ab

so

rb

an

ce

1.20E-05

1.00E-05

8.00E-06

6.00E-06

4.00E-06

2.00E-06

y = 117700x + 0.0026R2 = 0.9924

0

0.4

0.8

1.2

1.6

0.00E+00 4.00E-06 8.00E-06 1.20E-05

Concentration (M)

Ab

so

rb

an

ce

Fig. 4. UVeVis absorption spectra of compound 6 in DMSO at different concentration.(Inset: plot of absorbance versus concentration.)

0

100

200

300

400

500

660 680 700 720 740 760 780 800

Wavelength (nm)

In

ten

sity (a.u

.)

[BQ]=0

[BQ]=saturated

Fig. 7. Fluorescence emission spectral changes of compound 6 at concentration of1.00� 10�5 M on addition of different concentrations of BQ in DMSO. [BQ]¼ 0, 0.008,0.016, 0.024, 0.032 and 0.040 M.

0

200

400

600

800

1000

500 550 600 650 700 750 800

Wavelength (nm)

In

ten

sity (a.u

.)

0

0.4

0.8

1.2

1.6

Ab

so

rp

tio

n

Absorption

Excitation

Emission

Fig. 5. UVeVis absorption, fluorescence emission and excitation spectra of compound6 in DMSO. Excitation wavelength¼ 650 nm.

A. Nas et al. / Dyes and Pigments 99 (2013) 90e9896

zinc phthalocyanines (6 and 12) (kF¼ 1.00�108 s�1 for compound6 and kF¼ 0.58� 108 s�1 for compound 12) were found lower thanunsubstituted zinc phthalocyanine (kF¼ 1.47�108 s�1 [34]).

The production of the singlet oxygen by the photosensitizercompounds is very important for PDT applications because formedsinglet oxygen is killed the tumor cells. The generated singlet ox-ygen amount should be determined for target photosensitizercompounds. The amount of the generated singlet oxygen is quan-tified as singlet oxygen quantumyield (FD). In this study, the singletoxygen quantumyield values of the tetra- and octa-substituted zincphthalocyanines (6 and 12) were determined in DMSO by chemicalmethod using diphenylisobenzofuran (DPBF) as a singlet oxygenquencher. The decreasing of the absorbances of DPBF at 417 nmunder the appropriate light irradiation at five seconds intervals wasmonitored using UVeVis spectrometer. Any changes did notobserve in the Q band intensities of the studied phthalocyaninesduring the FD determinations (Fig. 6, using compound 12 as anexample), indicating that the studied phthalocyanine compoundswere not degraded under light irradiation (30 V) during singletoxygen determinations. The FD value of the tetra-substituted zincphthalocyanine (6) (FD¼ 0.66) is almost same with the FD value ofunsubstituted zinc phthalocyanine (FD¼ 0.67 [35]). But the FD

value of the octa-substituted zinc phthalocyanine (12) (FD¼ 0.53)is lower than the FD value of unsubstituted zinc phthalocyanine

0

0.2

0.4

0.6

0.8

350 450 550 650 750

Wavelength (nm)

Ab

so

rb

an

ce

0 sec5 sec10 sec15 sec20 sec25 sec

y = -0.0073x + 0.6162R2 = 0.9984

00.20.40.60.8

-5 5 15 25

Time (sec)

DP

BF

A

bs

orb

an

ce

Fig. 6. UVeVis spectral changes during the singlet oxygen quantum yield determi-nation for compound 12 in DMSO at a concentration of 1�10�5 M. (Inset: plot of DPBFabsorbance versus time.)

(FD¼ 0.67) suggesting that the aggregation behavior of octa-substituted compound in DMSO.

The identification of the photodegradation behavior of themolecules under light irradiation is especially important for PDTapplications, because we have to known the out of body time of themolecules after PDT activation. The degradation of the moleculesunder light irradiation is generally defined as photodegradationquantum yield (Fd). The photodegradation properties of the tetra-and octa-substituted zinc phthalocyanines (6 and 12) under lightirradiation (100 V) were studied and the Fd values of these com-pounds were determined in DMSO. The Fd values of studied tetra-and octa-substituted zinc phthalocyanines are almost similar butcompound 6 shows slightly lower Fd value (Fd¼ 2.15�10�5) thancompound 12 (Fd¼ 2.33�10�5). The Fd values of both studied zincphthalocyanines are slightly lower than unsubstituted zinc phtha-locyanine (Fd¼ 2.61�10�5 [34]) in DMSO. The studied zincphthalocyanine compounds (6 and 12) showed moderate stabilityunder light irradiation because the stable phthalocyanine com-pounds show Fd values as low as 10�6 and the unstable phthalo-cyanine compounds show Fd values approximately order of 10�3

according to the literature [36].The quenching of fluorescence behaviors of the tetra- and octa-

substituted zinc phthalocyanine compounds containing (E)-(3-cinnamoylphenoxy) groups were determined reducing of the fluo-rescence emission spectra of these compoundsby the additionof 1,4-benzoquinone (BQ) in DMSO. The quenching between zinc phtha-locyanines and BQ was found to obey SterneVolmer kinetics, whichis consistent with diffusion-controlled bimolecular reactions. Fig. 7

1

1.2

1.4

1.6

1.8

2

0 0.005 0.01 0.015 0.02 0.025 0.03 0.035 0.04 0.045

[BQ]

Io

/I

6

12

Fig. 8. SterneVolmer plots for BQ quenching of compounds 6 and 12 in DMSO. [MPc]1.00� 10�5 M in DMSO. [BQ]¼ 0, 0.008, 0.016, 0.024, 0.032 and 0.040 M.

Table 1Decomposition temperature of the novel phthalocyanines.

Compound M Initial decompositiontemperature in �C

Main decompositiontemperature in �C

4 2H 365.1 434.35 Ni 335.6 415.36 Zn 331.0 406.67 Co 295.4 400.38 Cu 327.4 366.19 Pb 341.5 395.512 Zn 389.0 411.3

A. Nas et al. / Dyes and Pigments 99 (2013) 90e98 97

shows the reducing of the emission spectra for compound 6 due tothe quenching by BQ in DMSO as an example. The slope of the plotsshown in Fig. 8 for studied phthalocyanines gave SterneVolmerconstant (KSV) values. The KSV value of the tetra-substituted zincphthalocyanine complex (6) (KSV¼ 19.00 M�1) is higher thanthe octa-substituted zinc phthalocyanine complex (12)(KSV¼ 8.43 M�1) in DMSO. It could be attributed to the formation ofthe more aggregated species for the octa-substituted complex (12)compared to tetra-substituted complex (6). The substitution of thephthalocyanine framework with (E)-(3-cinnamoylphenoxy) groupsdecreased thequenchingof thephthalocyanine compoundswith BQ.As a result, the KSV values of both studied complex are lower thanunsubstituted ZnPc (KSV¼ 31.90 M�1 [34]) in DMSO. The obtainedbimolecular quenching constant (kq) values for both studied zincphthalocyanine compounds (6 and 12) (kq¼ 1.26�1010

M�1 s�1 for compound 6 and kq¼ 1.40�1010 M�1 s�1 for compound12 in DMSO) are lower than unsubstituted zinc(II) phthalocyanine(kq¼ 2.61�1010 M�1 s�1 [34]). When compared to kq values be-tween the studied tetra- and octa-substituted zinc phthalocyanines,the octa-substituted compound has slightly higher value than tetra-substituted counterpart. The bimolecular quenching rate constantsof both studied zinc phthalocyanine compounds (6 and 12) wereobtained tobe close to thediffusion-controlled limits,w1010 M�1 s�1.

The thermal behaviors of the metallophthalocyanines were alsoexamined using the thermogravimetry/differential thermal anal-ysis (TG/DTA), as well as their photophysicochemical properties.The thermogravimetric data for newly synthesized compounds (4e9, 12) showed exceptional thermal stability. However, the obtainednovel phthalocyanines (4e9, 12) were not stable above 295 �C(Fig. S3). The initial and main decomposition temperatures weregiven in Table 1. The initial decomposition temperatures decreasedin the order of 12> 4> 9> 5> 6> 8> 7.

4. Conclusions

In summary, the synthesis of novel peripherally tetra-substituted metal-free (4) and metallophthalocyanines (5e9) andocta-substituted zinc(II) phthalocyanine (12) were described forthe first time and the characterization of these novel compoundswere achieved by various characterization methods (e.g. NMR, FT-IR, mass spectroscopy, elemental analysis in addition to thermalanalysis). Thermal analysis indicated that metal-free (4), Ni(II) (5),Zn(II) (6), Co(II) (7), Cu(II) (8), Pb(II) (9) and octa-substituted Zn(II)(12) showed good thermal stability and the most stable one is octa-substituted zinc(II) phthalocyanine (12). Moreover, these newcompounds have high solubility in some organic solvents (e.g.chloroform, pyridine, DMSO, DMF, dichloromethane). Thephotophysical and photochemical properties of studied zincphthalocyanines were investigated in DMSO due to determinationof the appropriateness of these compounds for PDT applicationssuch as cancer treatment. Only zinc phthalocyanines were used forthis purpose because the zinc phthalocyanine derivatives are mostsuitable compounds among the other studied phthalocyanines. The

photophysical and photochemical properties of octa-substitutedzinc phthalocyanine (12) are lower compared to the tetra-substituted zinc phthalocyanine (6) due to the formation of theaggregates for former compound in DMSO but it can be still enoughfor PDT applications. On the other hand, the tetra-substituted zincphthalocyanine compound showed higher photochemical andphotophysical properties especially high singlet oxygen generationand this compound is a good candidate for PDT applications ac-cording to the obtained values.

Acknowledgment

This study was supported by the Research Fund of KaradenizTechnical University, Project no: 2010.111.002.1 (Trabzon-Turkey).

Appendix A. Supplementary data

Supplementary data related to this article can be found at http://dx.doi.org/10.1016/j.dyepig.2013.04.014.

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