The novel mesityloxy substituted metallo-phthalocyanine dyes with long fluorescence lifetimes and high singlet oxygen quantum yields

Article abstract of DOI:10.1016/j.jphotochem.2015.09.009

The synthesis of novel peripheral or non-peripheral tetra-mesityloxy substituted metal-free, zinc and indium phthalocyanines, which are highly soluble in organic solvents, has been achieved. The phthalocyanines have been characterized by UV-vis, IR, MALDI

Full text of DOI:10.1016/j.jphotochem.2015.09.009

Accepted Manuscript
Title: The novel mesityloxy substituted
metallo-phthalocyanine dyes with long fluorescence lifetimes
and high singlet oxygen quantum yields
¨
Author: Ekrem Gurel Mehmet Pis¸kin Selc¸uk Altun Zafer
Odabas¸ Mahmut Durmus¸
PII:
S1010-6030(15)00352-4
DOI:
Reference:
http://dx.doi.org/doi:10.1016/j.jphotochem.2015.09.009
JPC 10009
To appear in:
Journal of Photochemistry and Photobiology A: Chemistry
Received date:
Revised date:
Accepted date:
5-6-2015
5-9-2015
9-9-2015
¨
Please cite this article as: Ekrem Gurel, Mehmet Pis¸kin, Selc¸uk Altun,
Zafer Odabas¸, Mahmut Durmus¸, The novel mesityloxy substituted metallo-
phthalocyanine dyes with long fluorescence lifetimes and high singlet oxygen
quantum yields, Journal of Photochemistry and Photobiology A: Chemistry
http://dx.doi.org/10.1016/j.jphotochem.2015.09.009
This is a PDF file of an unedited manuscript that has been accepted for publication.
As a service to our customers we are providing this early version of the manuscript.
The manuscript will undergo copyediting, typesetting, and review of the resulting proof
before it is published in its final form. Please note that during the production process
errors may be discovered which could affect the content, and all legal disclaimers that
apply to the journal pertain.

The novel mesityloxy substituted metallo-phthalocyanine dyes with long
fluorescence lifetimes and high singlet oxygen quantum yields
Ekrem Gürela, Mehmet Pişkinb, Selçuk Altuna, Zafer Odabaşa* zodabas@marmara.edu.tr,
Mahmut Durmuşc*
aMarmara University, Department of Chemistry, Kadıköy, 34722, Istanbul, Turkey
bÇanakkale Onsekiz Mart University, Vocational School of Technical Sciences, Department of Food
Technology, Çanakkale, 17100, Turkey
cGebze Technical University, Department of Chemistry, P.O. Box 141, Gebze, 41400,
Kocaeli, Turkey
*Corresponding authors: Tel: +90 216 347 96 41, Fax: +90 216 347 87 83.
1

Graphical Abstract
2

Highlights
1. Synthesis and characterization of alpha and beta substituted phthalocyanines.
2. Study of photophysical and photochemical properties of these compounds.
3. The effects of the substituent positions and metal differences in phthalocyanine.
4. Investigation of spectroscopic properties of the novel phthalocyanines.
3

ABSTRACT
The synthesis of novel peripheral or non-peripheral tetra-substituted metal-free, zinc and
indium phthalocyanines, which are highly soluble in organic solvents, has been achieved. The
complexes have been characterized by UV–Vis, IR, MALDI-TOF Mass spectroscopies and
elemental analysis. On their spectroscopic, photochemical and photophysical properties, the
effects of the substituent position and the variety of central metal ions in phthalocyanine
cavity are also investigated. Photodegradation, singlet oxygen and fluorescence quantum
yields, and fluorescence lifetimes in dimethylformamide for the phthalocyanines are
described. These properties of the compounds are very useful for photodynamic therapy
applications and their high singlet oxygen quantum yields are very important for Type II
mechanisms. The phthalocyanines can be appropriate candidates as Type II photosensitizers.
KEYWORDS:
Trimethylphenoxy;
phthalocyanine;
mesityloxy;
photophysical;
photochemical; photosensitizers.
4

1. INTRODUCTION
Synthetic porphyrin analogues called phthalocyanines (Pcs) are widely used as dyes and
pigments [1-3]. Pc compounds show a two-dimensional aromatic system due to delocalized
18π electronic system in the Pc core and this system is structurally similar to the aza-[18]-
annulene series. The particular electronic delocalization of 18π system gives rise to
outstanding electronic, unconventional physical and chemical properties, which make them
valuable in different applications and technology [4]. There are a number of scientific
documents about Pcs and their applications that discuss the developments in these interesting
fields [5-7]. Pcs are used in a wide variety of applications. More recently, Pcs have been
found to be useful in a number of areas outside their traditional uses as dyes; they have been
also used technological applications as sensing elements in gas and chemical sensors [8-10],
electrocatalysts [11], electrochromic display devices [12], information storage systems [13],
optical switching and limiting devices [14], molecular solar cells [15,16], nonlinear optical
materials [17], light-emitting devices [18,19], organic field effect transistors [20], a colour ink
[21] and marker [22], and the photosensitizers for photodynamic therapy [23,24]. To increase
the utility of Pcs in applications, Pc compounds can be derived by multiple modifications in
the macrocyclic core, through the introduction of different metal atoms, as well as the
functionalization with a variety of groups in the peripheral and non-peripheral position on the
Pc skeleton [25,26].
The unsubstituted Pcs can present solubility problems and aggregation behaviour for
some applications [27,28]. Hence many research activities focused on synthesizing of soluble
Pcs by adding different functional groups to the molecule [29-31]. In addition to the
solubility, chemical and physical properties of the Pcs in organic solvents also depend on the
substituents on the Pc ring. Methylphenoxy or methoxyphenoxy groups on Pc skeleton
increase Pc solubility in common solvents and it is known that phenolic compounds have
5

potential related health benefits as antioxidants and they have also become apparent potential
in therapeutic in the treatment of the diseases such as liver cirrhosis, cancer, diabetes, aging
etc. in recent times [32-35]. In previous study [36], methylphenoxy group as both a bioactive
compound and antioxidant and Pc as photosensitizers for photodynamic therapy (PDT) were
combined to produce soluble, nonaggregated and bifunctional new Pc complexes. The study
revealed that the novel Pcs can be potential Type II photosensitizers for PDT in chemotherapy
We wondered how substitution position of methyl group on phenoxy skeleton affect
photophysical and photochemical properties as compared with 2,4,6-trimethylphenoxy
(mesityloxy) substituted Pcs derivaties. Hence, in this study, 3- and 4-
mesityloxyphthalonitrile (1 and 2), which are starting materials for target Pcs, have been
obtained by the reaction of 2,4,6-trimethylphenol with 3- or 4-nitrophthalonitrile and novel
soluble and non-aggregated metal-free (7 and 8), zinc (5 and 6) and indium Pc (3 and 4)
compounds have been synthesized by using 1 and 2.
It is worth noting that each Pc product obtained was a mixture of four regioisomers of
C4h, D2h, C2V and Cs symmetry with similar physical and chemical properties. While it is
theoretically possible to separate these isomers due to their different geometries, it has been
accomplished only for very specific Pcs by use of specially designed HPLC columns [37].
Thus, singlet oxygen generation by the Pcs and their usability as photosensitizer dyes for PDT
in cancer treatment have been investigated (Scheme 1). The effects of different isomer
substituent position and the nature of the central metal ions in the Pc on these properties are
also studied and compared with the counterparts in our previous literature [36].
2. EXPERIMENTAL
The materials, equipments, photophysical and photochemical formulas and parameters
used are supplied as supplementary information.
6

2.1. Synthesis
2.1.1. General procedure for the phthalonitrile syntheses
3-/or 4-nitrophthalonitrile (3.50 g, 20 mmol), 2,4,6-trimethylphenol (2.78 g, 21.40 mmol)
and anhydrous K2CO3 (14 g, 100 mmol) were added in 35 mL dimethylsulfoxide (DMSO).
The mixture was stirred at 45ο C for 36 hours under inert atmosphere. Then the reaction
mixture was poured into cold water. The light yellow ppt was filtered off and washed using
cold water and dried in room temperature. The crude products were purified by column
chromatography using silica gel eluting with CHCl3.
3-(mesityloxy)phthalonitrile (1): Solubility: dichloromethane (DCM), CHCl3,
ο
tetrahydrofuran (THF), DMSO and dimethylformamide (DMF). Mp: 160 C. Yield: 4.45 g
(84.30%). Anal. calculated for C17H14N2O C, 77.84%; H, 5.38%; N, 10.68%; found C,
77.65%; H, 5.54%; N, 10.83%. IR (ATR) max / cm-1: 728, 774, 795, 802, 854, 908, 986(CC
str.), 1035(CC str.), 1125, 1138, 1173, 1196, 1269(CO str.), 1312(CO str.), 1453(CH
bend.), 1480(CH bend.), 1575(C=C str.), 1596(C=C str.), 2226(C≡N str.), 2853(>CH2 str.),
2920(>CH2 str.), 3032(=CH str.), 3084(=CH str.). H-NMR (CDCl3): , ppm 2.08 (s, 6H),
2.32 (s, 3H), 6.95 (s, 2H), 6.76 (dd, J = 8.67 Hz, J = 2.36 Hz, 1H), 7.4 (dd, J = 7.56 Hz, J =
2.05 Hz, 1H), 7.5 (t, J = 8.50 Hz, J = 7.85 Hz, 1H) [22].
4-(mesityloxy)phthalonitrile (2): Solubility: DCM, CHCl3, THF, DMSO and DMF. Mp:
ο
155 C. Yield: 4.24 g (80.12%). Anal. calculated for C17H14N2O C, 77.84%; H, 5.38%; N,
10.68%; found C, 78.02%; H, 5.43%; N, 10.52%. IR (ATR) max / cm-1: 756, 772, 807, 842,
856, 870, 947, 958, 1037(CC str.), 1086(CC str.), 1136, 1163, 1196, 1244(CO str.),
1277(CO str.), 1317(CO str.), 1379, 1478(CH bend.), 1575(C=C str.), 1591(C=C str.),
1
2228(C≡N str.), 2855(>CH2 str.), 2917(>CH2 str.), 3083(=CH str.). H-NMR (CHCl3-d): ,
7

ppm 2.04 (s, 6H), 2.32 (s, 3H), 6.95 (s, 2H), 7.12 (d, J = 2.15 Hz, 1H), 7.11 (dd, J = 7.25 Hz,
J = 2.52 Hz, 1H), 7.70 (d, J = 9.15 Hz, 1H).
2.1.2. Synthesis of metallo-phthalocyanines (General procedure)
Compounds 1 or 2 (0.20 g, 0.76 mmol), 0.45 mmol zinc acetate dihydrate or indium
acetate and 0.30 mL of DMF mixture was heated at 360o C in a reaction tube for 17 minutes
under inert atmosphere. The new green mixture was precipitated by adding solution. The
precipitate was filtered and washed with acetic acid, water and methanol (except InPcs 3 and
4, they were washed only by methanol.) for 12 hours in the Soxhlet apparatus. The new
products were purified by silica jel column chromatography with CHCl3.
1(4),8(11),15(18),22(25)-Tetrakis-(2,4,6-trimethylphenoxy)phthalocyaninatoindium (III)
acetate (3): Solubility: CHCl3, DCM, toluene, THF, DMSO and DMF. Mp>300 οC. Yield: 30
mg (15.00 %). Calculated for C70H59InN8O6 : C, 68.74%; H, 4.86%; N, 9.16%; found C,
68.45%; H, 5.14%; N, 9.35 %. IR (ATR) max / cm-1: 741, 773, 851, 877, 1005(CC str.),
1075(CC str.), 1119(CN str.), 1196(CN str.), 1245(CO str.), 1326(CO str.), 1410(CH
bend.), 1473(CH bend.), 1584(C=C str.), 1603(C=C str.), 1670(C=N str.), 1731(axial C=O),
2847(>CH2 str.), 2917(>CH2 str.), 2953(>CH2 str.), 3046(=CH str.), 3073(=CH str.). UV–
Vis (DMF, 1.0x10-5M): max (nm) (log ε): 325 (4.63), 647 (4.43), 720 (5.16). MALDI-TOF-
MS: Calc.: 1223.08, found: 1162.40 [M-OAc]+, 1180.41 [M-OAc+H2O]+, 1198.29 [M-
OAc+2H2O]+, 1216.25 [M-OAc+3H2O]+. 1H-NMR (600MHz, DMSO-d6, ppm): δ=9.20-8.77
(m, 4H), 8.18-7.89 (m, 4H), 7.29-6.82 (m, 8H), 6.90-6.54 (m, 4H), 2.37 (s, 12H), 2.19 (s,
24H), 1.23 (s, 3H). 13C-NMR (600MHz, DMSO-d6, ppm): δ=177.52, 169.15, 167.80, 162.82,
155.47, 154.51, 153.32, 149.08, 148.01, 137.24, 135.68, 135.47, 135.11, 133.45, 130.35,
130.28, 129.03, 128.93, 127.45, 119.58, 118.08, 116.52, 115.40, 114.75, 24.68, 20.96, 16.10.
8

2(3),9(10),16(17),23(24)-Tetrakis-(2,4,6-trimethylphenoxy)phthalocyaninatoindium
ο
(III) acetate (4): Solubility: CHCl3, DCM, toluene, THF, DMF and DMSO. Mp>300 C.
Yield: 100.00 mg (50.04%). Calculated for C70H59InN8O6 : C, 68.74%; H, 4.86%; N, 9.16%;
found C, 68.67%; H, 5.02%; N, 9.27 %. IR (ATR) max / cm-1: 705, 744, 824, 852, 942,
1043(CC str.), 1086(CC str.), 1114(CN str.), 1189(CN str.), 1218, 1267(CO str.), 1334,
1473(CH bend.), 1604(C=C str.), 1676(C=N str.), 1740(axial C=O), 2847(>CH2 str.),
2920(>CH2 str.), 2947(>CH2 str.), 3060(=CH str.), 3012(=CH str.). UV–Vis (DMF, 1x10-
5M): max (nm) (log ε): 356 (4.76), 627 (4.30), 696 (5.01). MALDI-TOF-MS: Calc.: 1223.08,
1
found: 1162.59 [M-OAc]+, 1180.51 [M-OAc+H2O]+, 1198.42 [M-OAc+2H2O]+. H-NMR
(600MHz, DMSO-d6, ppm): δ=8.50-7.45 (m, 4H), 7.18-7.02 (m, 16H), 2.28 (s, 24H), 2.02 (s,
12H), 1.23 (s, 3H).
1(4),8(11),15(18),22(25)-Tetrakis-(2,4,6-trimethylphenoxy)phthalocyaninatozinc(II) (5):
ο
Solubility: CHCl3, DCM, toluene, THF, DMF and DMSO. Mp>300 C. Yield: 48 mg (24.00
%). Anal calculated for C68H56ZnN8O4: C, 73.28%; H, 5.06%; N, 10.05%; found C, 73.10%;
H, 5.19%; N, 10.18 %. IR (ATR) max / cm-1: 765, 802, 850, 877, 1000(CC str.), 1080(CC
str.), 1112(CN str.), 1196(CN str.), 1242(CO str.), 1312(CO str.), 1474(CH bend.),
1586(C=C str.), 1658(C=N str.), 2853(>CH2 str.), 2915(>CH2 str.), 2953(>CH2 str.),
3000(=CH str.), 3053(=CH str.). UV–Vis (DMF, 1x10-5M) max (nm) (log ε): 318 (4.61),
1
628 (4.51), 701 (5.28). MALDI-TOF-MS: Calc.: 1113.61, found: 1113.16 [M]+. H-NMR
(600MHz, DMSO-d6, ppm): δ=9.13-8.81 (m, 4H), 8.10-7.92 (m, 4H), 7.20-6.94 (m, 8H),
6.62-6.43 (m, 4H), 2.40 (s, 12H), 2.02 (s, 24H). 13C-NMR (600MHz, DMSO-d6, ppm):
δ=169.19, 167.80, 162.83, 155.30, 155.08, 154.54, 153.17, 150.12, 148.00, 137.23, 135.68,
135.47, 135.00, 133.64, 131.17, 130.28, 129.26, 129.22, 125.43, 119.58, 118.03, 116.51,
114.38, 31.22, 20.97.
9

2(3),9(10),16(17),23(24)-Tetrakis-(2,4,6-trimethylphenoxy)phthalocyaninatozinc(II) (6):
ο
Solubility: CHCl3, DCM, toluene, THF, DMF and DMSO. Mp>300 C. Yield: 37.80 mg
(18.90%). Anal calculated for C68H56ZnN8O4: C, 73.28%; H, 5.06%; N, 10.05%; found C,
73.42%; H, 5.16%; N, 10.21%. IR (ATR) λmax/ cm-1: 705, 743, 771, 821, 853, 941, 1043(CC
str.), 1091(CC str.), 1115(CN str.), 1140(CN str.), 1266(CO str.), 1336(CO str.),
1470(CH bend.), 1606(C=C str.), 1656(C=N str.), 2847(>CH2 str.), 2919(>CH2 str.),
2960(>CH2 str.), 3038(=CH str.). UV–Vis (DMF, 1x10-5M): max (nm) (log ε): 355 (4.80),
1
615 (4.43), 682 (5.18). MALDI-TOF-MS: Calc.: 1113.61, found: 1113.30 [M]+. H-NMR
(600MHz, DMSO-d6, ppm): δ=8.90-7.88 (m, 8H), 7.80-7.10 (m, 12H), 2.47-2.25 (m, 36H).
2.1.3. Synthesis of metal-free phthalocyanines (General procedure)
The mixture of compounds 1 or 2 (0.20 g, 0.76 mmol), 0.30 mL DMF and 0.25 mL 1,8-
diazabicyclo[5.4.0]undec-7-ene (DBU) was heated at 350ο C for 15 minutes under inert
atmosphere in a reaction tube. The new green product was dissolved in 3 mL DMF. The
reaction mixture was precipitated with 70% CH3COOH aqueous solution. The solid product
in the mixture was filtered off and transferred into the Soxhlet apparatus then purified by
washing with hot acetic acid, water and methanol for 12 hours. The new products were
purified by silica jel column chromatography with CHCl3.
1(4),8(11),15(18),22(25)-Tetrakis-(2,4,6-trimethylphenoxy)phthalocyanine (7): solubility:
CHCl3, DCM, toluene, THF and DMF. Mp>300ο C. Yield: 12.90 mg (6.50%). Anal calculated
for C68H58N8O4: C, 77.69%; H, 5.56%; N, 10.66%; found C, 77.50%; H, 5.64%; N, 10.53%.
IR (ATR) max / cm-1: 744, 801, 853, 868, 959, 1021(CC str.), 1077(CC str.), 1107(CN
str.), 1198(CN str.), 1224(CO str.), 1332(CO str.), 1474(CH bend.), 1586(C=C str.),
1596(C=C str.), 1681(C=N str.), 2855(>CH2 str.), 2919(>CH2 str.), 3007(=CH str.),
3053(=CH str.), 3280(NH str.). UV–Vis (DMF, 1.0x10-5M): λmax (nm) (log ε): 317 (4.57),
630 (4.28), 697 (4.96), 722 (4.78). MALDI-TOF-MS: Calc.: 1051.24, found: m/z 1051.45
10

1
[M]+. H-NMR (600MHz, DMSO-d6, ppm): δ=8.90-8.62 (m, 4H), 8.01-7.81 (m, 4H), 7.41-
6.73 (m, 12H), 2.42 (s, 24H), 1.21 (s, 12H).
2(3),9(10),16(17),23(24)-Tetrakis-(2,4,6-trimethylphenoxy)phthalocyanine (8): solubility:
CHCl3, DCM, toluene, THF and DMF. Mp>300ο C. Yield: 35.00 mg (17.50%). Anal
calculated for C68H58N8O4: C, 77.69%; H, 5.56%; N, 10.66%; found C, 77.79%; H, 5.66%; N,
10.83%. IR (ATR) max / cm-1: 695, 741, 819, 851, 924, 956, 1005(CC str.), 1091(CC str.),
1111(CN str.), 1158(CN str.), 1252(CO str.), 1337(CO str.), 1425(CH bend.),
1466(CH bend.), 1614(C=C str.), 1682(C=N str.), 2854(>CH2 str.), 2918(>CH2 str.),
2953(>CH2 str.), 3011(=CH str.), 3073(=CH str.), 3290(NH str.). UV–Vis (DMF, 1.0x10-
5M): max(nm), (log ): 350 (4.34), 611 (4.05), 676 (4.50), 701 (4.25). MALDI-TOF-MS:
Calc.: 1051.24, found: m/z 1051.51 [M]+. 1H-NMR (600MHz, DMSO-d6, ppm): δ=8.01-7.92
(m, 4H), 7.74-7.65 (m, 4H), 7.27-7.17 (m, 4H), 7.11-6.93 (m, 8H), 2.39 (bs, 24H), 1.24 (s,
12H).
3. RESULTS AND DISCUSSION
3.1. Syntheses and characterization
3- and 4-(mesityloxy)phthalonitrile (1 and 2) have been obtained by the reaction of 2,4,6-
trimethylphenol with 3- or 4-nitrophthalonitrile. To synthesize the novel soluble and non-
aggregated zinc (5 and 6) and indium Pc (3 and 4) compounds, a mixture of compound 1 (or
2), zinc acetate dihydrate (or indium acetate) and DBU in absolute DMF was heated at
approximately 350o C for 15 minutes. The compound 5 (or 10) was obtained as a green
product. Pcs 7 and 8 were also synthesized at the same condition without using any salts
(Scheme 1). The compounds 1 and 7 were synthesised according to the BASF Patent [22].
1
The elemental analysis, IR, UV–Vis, H-NMR and MALDI-TOF mass spectroscopic data
confirmed the proposed structures of all new compounds.
11

In the IR spectra of starting materials, the disappearance of the NO2 peak nearby 1350
cm-1, the appearance of new vibration peaks at 1269 and 1277 cm-1 belonging to Ar−O−Ar
and strong −C≡N peaks at 2226 and 2228 cm-1 indicated the formation of 1 and 2,
respectively. The −C≡N peaks of 1 and 2 disappeared after reduction to Pcs (3-8). The IR
spectra of the metal free-Pcs 7 and 8 showed a N−H stretching band peaks at 3280 and 3290
cm-1 due to the inner core. Other peaks were similar in most peaks (Table S1).
The UV-Vis absorption spectra of the Pcs showed a single (narrow) Q band for zinc and
indium Pcs (3–6) and split into two Q bands for H2Pcs (7 and 8) up to  1 x 10-5 mol dm-3 in
DMF as typical of metallo and metal-free Pcs [38, 39]. The UV-Vis spectra of the
unsubstituted, non-peripherally (3) and peripherally (4) mesityloxy substituted In(OAc)Pcs
showed characteristic absorption in the Q band region at 683, 720 and 696 nm in DMF,
respectively (Table 1). The splitting Q bands of metal-free Pcs, at 722 and 697 nm for 7, 701
and 676 nm for 8 indicated the structure with non-degenerate D2h symmetry of them. Red-
shifted 24 nm between 3 and 4; 19 nm between 5 and 6 and 20 nm between 7 and 8 in DMF
(Fig. 1a-1c) were typical of non-peripheral substituted Pcs due to their linear combination of
the atomic orbitals (LCAO) coefficients at the non-peripheral positions of the highest
occupied molecular orbital (HOMO) being greater than those at the peripheral positions as
explained in the literature [40, 41]. The Q bands of the indium metallo-Pcs 3 and 4 were more
red-shifted than those of zinc metallo-Pcs 5 and 6 in DMF because of bigger atomic radius of
indium atom (Fig. 1a-1b).
The [M-OAc]+ peaks of the In(OAc)Pcs (3 and 4), the molecular ion peaks [M]+ of ZnPcs
(5 and 6) and H2Pcs (7 and 8) were identified easily with 2,5-dihydroxybenzoic acid (DHB)
MALDI matrix by using MALDI-TOF mass spectrometry. The molecular ion peaks (5-8)
were observed at 1113.16, 1113.30, 1051.45 and 1051.51 Da, respectively. The [M-OAc]+
peaks of the In(OAc)Pcs (3 and 4) were observed at 1162.40 and 1162.59 Da, respectively.
12

Beside the [M-OAc]+ peaks of the In(OAc)Pcs (3 and 4), three and two moles of water adduct
were also seen, respectively (Fig. S1-S6).
1
The H-NMR spectra of 1 and 2 exhibited a singlet methyl (–CH3) proton signals at 
2.08, 2.32 and 2.04, 2.32 ppm, respectively. The peaks between 6.76-7.50 ppm for 1 or
1
between 7.12-7.70 ppm for 2 in the H-NMR spectra indicated the aromatic protons for the
trimethylbenzene and pthalonitrile rings (Fig. S7 and S8).
1H-NMR and 13C-NMR spectra of the Pcs were also obtained. and the proton and carbon
atom numbers of the Pcs were matched the desired compounds in the spectra of the Pcs (d6-
1
dimethylsulfoxide). The suitable H-NMR and 13C-NMR spectra of ones were shown in
Fig.S9-S16).
3.2. Aggregation studies
In this study, the aggregation behaviours of mesityloxy substituted Pcs were examined in
DMF, THF, toluene, chloroform and DCM to select more suitable solvents for investigation
of photophysical and photochemical properties of these Pcs (Fig. 2 for Pc 8 and Fig. S17 for
Pc 7). The Pcs (3-8) did not show any aggregation behaviours in the solvents but DMF was
preferred because this solvent can be used for biological applications and it has any toxic
effect in small amount [42-46]. In addition, the aggregation behaviours of the Pcs in the
concentrations ranging from 1.2×10−5 to 2×10−6 M in DMF were studied and Lambert–Beer
law was obeyed (Fig. 3 for 3 and Fig. S18 for unsubstituted In(OAc)Pc).
An extra peak at 753 nm in CHCl3 and DCM solutions was occured for the non-
peripherally substituted ZnPc 5 (Fig. 4a) and a small shoulder at 727 nm in DCM for the
peripherally substituted ZnPc 6 (Fig. 4b). These peaks could be protonation of the
nitrogen atoms on the Pc core instead of J-type aggregation because DCM and chloroform
contain small amounts of acidic impurities (generally HCl) [47-49]. Additionally, The
13

absorption intensity of this extra peaks increased by adding trifluoroacetic acid and
decreased by adding potassium carbonate (Fig. S19 for 5 and Fig. S20 for 6 in DCM) as in
the literature [47-49]. This result also verified the protonation of inner nitrogen atoms in
the Pcs in DCM and chloroform asidic solvents.
3.3. Fluorescence spectra
The fluorescence emission, absorption and excitation spectra of peripherally
mesityloxy substituted In(OAc)Pc 4, ZnPc 6 and H2Pc 8 in DMF were given as examples in
Figure 5a-5c, respectively. These spectra of unsubstituted In(OAc)Pc in DMF were also
given in supplementary information (Fig. S21). The fluorescence emission of the
In(OAc)Pcs 3 and 4 were observed less intense than other studied ZnPcs and H2Pcs (5-8) in
DMF due to the heavy metal atom effect of the indium ion. The observed Stokes shifts were
within the region for Pcs complexes. All Pcs (3-8) showed similar fluorescence
behaviours in DMF (Fig. 5) and their fluorescence emission peaks were listed in Table 1.
While the Stokes shifts of In(OAc)Pcs (3-4) in this study were lower compared to
counterparts in the literature [36], Stokes shifts of ZnPcs and H2Pcs (5-9) were higher than
counterparts in the literature [36].
3.4. Fluorescence Studies
The fluorescence quantum yields (ΦF) of Pcs 3, 4, 5, 6, 7 and 8 in DMF were given in
Table 2. The ΦF values of indium Pcs were much lower than Zinc and metald free Pcs (5-8)
because indium is the heavy metal and causes quenching of the fluorescence (Table 2). Heavy
metals enhances intersystem crossing (through spin orbit coupling) and increases the number
of the triplet state species [50]. Furthermore, it seems that there is more pronounced channel
of intersystem crossing as both complexes 3 and 4 have very high  values.
14

The ΦF values of mesityloxy substituted ZnPcs are higher than that of unsubstituted
ZnPc in DMF and it may occur due to the presence of mesityloxy groups on the Pcs skeleton
and so their fluorescence quenching decrease. Moreover, the ΦF values for the peripherally
substituted Pcs (4, 6 and 8) were higher than the corresponding non-peripherally substituted
derivatives (3, 5 and 7) due to the effect of substituent position on the Pc ring. The ΦF values
of Pcs (3-8) were found higher than counterparts in the literature [36]. The fluorescence
lifetimes (τF) of the Pcs were determined by using a time correlated single photon counting
(TCSPC) and the obtained results were supplied in Table 2 (Fig. 6 for ZnPc 6 and Fig. S22 for
unsubstituted In(OAc)Pc). Two fluorescence lifetimes for the Pcs were observed in DMF.
The average fluorescence lifetimes of Pcs in DMF were given in Table 2 [51-53]. The bi-
exponential decay could be attributed to the quenched (shorter) and unquenched (longer) Pc
lifetimes The quenched lifetimes are due to the small amounts of aggregates which are non-
fluorescent but quench the fluorescence of the monomers.
The τF values were higher for In(OAc)Pc 3 and 4 and ZnPc 5 and 6 than counterpart
unsubstituted In(OAc)Pc and unsubstituted ZnPc suggesting less quenching by the
substituents (Table 2). The metal free Pcs 7 and 8 showed shorter fluorescence lifetimes than
ZnPcs in DMF. These results show the metal effects of Pcs on their fluorescence properties.
On the other hand, the fluorescence lifetimes of the non-peripherally substituted Pcs (3, 5 and
7) were shorter than those of peripherally substituted Pcs (4, 6 and 8). While τF values of
InOAcPc 4, ZnPcs 5, 6, H2Pcs 7, 8 were found moderately longer than counterparts in the
literature [36], τF value of non-peripherally substituted InOAcPc 3 was found slightly shorter
than counterpart in the literature [36]. The natural radiative life time (τ0) values of
unsubstituted In(OAc)Pc and the substituted In(OAc)Pcs (3 and 4) were quite longer than
those of the ZnPcs (5 and 6) and H2Pcs (7 and 8) in DMF. The τ0 values of 5 and 6 were also
longer than those of metal-free counterparts due to the presence of zinc metal in the cavity of
15

Pcs 5 and 6. While τ0 values of InOAcPcs (3-4) were shorter than counterparts in the literature
[36], τ0 values of ZnPcs and H2Pcs (5-8) were longer than counterparts in the literature [36].
Especially, τ0 values of H2Pcs (7 and 8) were very longer when compared to counterparts in
the literature [36]. The rate constants for fluorescence (kF) values of In(OAc)Pcs 3 and 4 were
quite lower than those of Pcs (5-8) due to heavy metal atom effect of indium atom as above.
While kF values of InOAcPcs (3-4) were higher than counterparts in the literature [36], kF
values of ZnPcs and H2Pcs (5-8) were lower than counterparts in the literature [36].
Especially, kF values of H2Pcs (7 and 8) were highly lower than counterparts in the literature
[36].
3.5. Singlet oxygen quantum yields (ΦΔ)
The quantity of ΦΔ determines the capability of the compounds as photosensitizers in
photodynamic therapy (PDT) applications. The ΦΔ values were determined in DMF using the
chemical method and 1,3-diphenylisobenzofuran (DPBF) was used as a quencher. The
diminution of DPBF absorbance at 417 nm was monitored using UV-Vis spectrophotometer
(Fig. 7 for 4, 6 and 8 as examples and Fig. S23 for unsubstituted In(OAc)Pc). The Q band
intensities of new Pcs were no changed and the Pcs were not degraded during singlet oxygen
studies. The  values of the indium Pcs were higher than zinc and metal free Pcs in DMF as
expected due to large atoms in the Pc cavity. The similar results were observed in the
literature [54-60] bearing similar substituent like phenoxy groups. The  values of the
H2Pcs 7 and 8 were lower than other metallo-Pcs in DMF. All the metallo-Pcs have good
singlet oxygen quantum yields (ΦΔ) so they may be used as photosensitizers in applications of
PDT (Table 2). The  values of Pcs (3-8) were found lower than counterparts in the
literature [36]. Study of substituent position effect showed that the  values of alpha-
substituted Pcs (3, 5 and 7) were higher than beta-substituted Pcs (4, 6 and 8) in DMF.
16

3.6. Photodegradation quantum yields (Φd)
The UV-Vis spectral changes for mesityloxy substituted Pcs (3-8) during light irradiation
in DMF were measured and given in Figure 8 for 4, 6 and 8 as examples and Fig. S23 for
unsubstituted In(OAc)Pc. The intensities of the B and Q bands were observed to be only
decreasing and the shapes of the spectra were not deteriorated under light irradiation. The Φd
values of the Pcs were similar with the metallo-Pc derivatives with different substituents as in
the literature [61]. Stable Pc compounds show Φd values as low as 10-6 and these values for
unstable Pcs in the order of 10-3 were reported [61]. The formed singlet oxygen under
photodegradation condition is believed to be a decisive species that is responsible for the
photodegradation of Pcs [62]. The photodegradation quantum yield values of the Pcs (3-8) in
DMF were presented in Table 2. The substituted Pcs (3-8) were less stable to degradation than
unsubstituted In(OAc)Pc and ZnPc in DMF due to electron-donating ability of the
mesityloxy groups. While the peripherally substituted H2Pc 8 was the most stable, the non-
peripherally substituted ZnPc 5 was the least stable among the studied Pcs. It seems that
indium, zinc metals in the Pc cavity and 2,4,6-trimethylphenoxy groups on the Pc skeleton
increase their Φd values and decrease their stability under light irradiation during the
photodegradation studies. InOAcPcs (3-4) and H2Pcs (7-8) were more stable than counterparts
in the literature [36]. While the peripherally substituted ZnPc (5) was less stable than
counterpart in the literature [36], non-peripherally substituted ZnPc (4) was more stable than
counterpart in the literature [36].
4. CONCLUSIONS
In our study, the syntheses of tetra non-peripherally and peripherally mesityloxy
substituted In(OAc)Pcs, ZnPcs and H2Pcs were described and the compounds were
characterized by spectroscopic techniques, such as MALDI-TOF, IR and UV–Vis and
17

fluorescence spectral data and elemental analysis results. The photophysical and
photochemical properties of the mesityloxy substituted phthalocyanines in DMF were
examined for comparison of the effects of the substituent positions on the Pc framework and
nature of metals in Pc cavity. All metallo and metal free-Pcs (3-8) showed high solubility in
common solvents (such as chloroform, DCM, toluene, THF, DMSO and DMF). The
fluorescence properties of these phthalocyanines were affected significantly by the change of
the central metal. The fluorescence quantum yields and average life time yields of Pcs (3-8)
have good found compared to counterparts in the literature [36]. The indium metallo Pcs
showed very low fluorescence emission due to the larger indium metal ion in the Pc cavity.
The excitation spectra of zinc and metal-free phthalocyanines were similar to absorption
spectra and both spectra were mirror images of their fluorescent spectra. The mesityloxy
substituted indium and zinc phthalocyanines (3-6) gave good singlet oxygen quantum yields,
especially the non-peripherally substituted indium phthalocyanine 3 showed the highest value
in DMF. The value of singlet oxygen quantum yields ranged from 0.20 (for 8) to 0.86 (for 3)
in DMF indicates of the potential of these compounds as photosensitizers for photodynamic
therapy applications. The substitution of the Pc framework with mesityloxy group as a
substituent decreases the photostability of the Pcs in DMF. The photochemical properties of
2,3,6-trimethylphenoxy substituted Pcs are better than the novel synthesized 2,4,6-
trimethylphenoxy substituted counterparts Pc (3-8). These results show that isomer groups on
substituent effect on photophysical and photochemical properties.
ACKNOWLEDGMENTS
We are thankful to Marmara University, The Commission of Scientific Research
Projects (BAPKO) (Project No: FEN-C-YLP-041213-0459)
18

REFERENCES
[1]
[2]
C.C. Leznoff, A.B.P. Lever, Phthalocyanines Properties and Applications, vols. 1–4,
Wiley-VCH, Weinheim, Germany, 1989–1996.
N.B. McKeown, Phthalocyanine Materials: Synthesis, Structure and Function,
Chemistry of Solid State Materials, vol. 32, Cambridge University Press, London,
1998.
[3]
[4]
[5]
K. Kadish, K.M Smith, R. Guilard (Eds), The Porphyrin Handbook, vols. 16–20,
California Academic Press, 2003.
K. Kadish, K.M Smith, R. Guilard (Eds), The Porphyrin Handbook, vol. 15, chapter
97, California Academic Press, Boston, 2003.
A.S. Abd-El-Aziz, C.E. Carraher, C.U. Pittman, J.E. Sheats, M. Zeldin,
Macromolecules containing metal and metal-like elements, New York, John Wiley &
Sons, Inc, (2003–2007).
[6]
T. Yamamoto, H. Fukumoto, T. Koizumi, J. Inorg. Organomet. Polym. Mater. 19
(2009) 3.
[7]
[8]
[9]
W.Y. Wong, C.L. Ho, Coord. Chem. Rev. 250 (2006) 2627–2690.
B. Çeken, M. Kandaz, A. Koca, J. Coord. Chem. 65 (2012) 3383–3394.
X. Liu, C. Qi, T. Bing, X. Cheng, D. Shangguan, Anal. Chem. 81 (2009) 3699–3704.
[10] S. Altun, A. Altındal, A.R. Özkaya, M. Bulut, Ö. Bekaroğlu, Tetrahedron Lett. 49
(2008) 4483–4486.
[11] X. Chen, X. Hu, L. An, N. Zhang, D. Xia, X. Zuo, X. Wang. Electrocatalysis 5 (2014)
68–74.
[12] M.L. Rodriguez-Mendez, J.A. De Saja, J. Porphyrins Phthalocyanines 13 (2009) 606–
615.
[13] K. Lian, R. Li, H. Wang, J. Zhang, D. Gamota, Mater. Sci. Eng. B 167 (2010) 12–6.
19

[14] C.B. Yao, Y.D. Zhang, D.T. Chen, H.T. Yin, C.Q. Yu, J. Li, P. Yuan, Opt. Laser
Technol. 47 (2013) 228–231.
[15] T. Ikeuchi, H. Nomoto, N. Masaki, M.J. Griffith, S. Mori, M. Kimura, Chem.
Commun. 50 (2014) 1941–1943.
[16] M. Kimura, H. Nomoto, H. Suzuki, T. Ikeuchi, H. Matsuzaki, T.N. Murakami, A.
Furube, N. Masaki, M.J. Griffith, S. Mori, Chem. Eur. J. 19 (2013) 7496–7502.
[17] M.M. Ayhan, A. Singh, C. Hirel, A.G. Gürek, V. Ahsen, E. Jeanneau, I. Ledoux-Rak,
J. Zyss, C. Andraud, Y. Bretonniere, J. Am. Chem. Soc. 134 (2012) 3655–3658.
[18] Z.B. Deng, Z.Y. Lu, Y.L. Chen, Y.H. Yin, Y. Zou, J. Xiao, Y.S. Wang, Solid-State
Electron 89 (2013) 22–25.
[19] K. Narayan, S. Varadharajaperumal, G.M. Rao, M.M. Varma, T. Srinivas, Curr. Appl.
Phys. 13 (2013) 18–25.
[20] Y. Shi, X.Y. Li, Org. Electron 15 (2014) 286–293.
[21] H. Kobayashi, Y. Kondou, Y. Yabuki, K. Yagi, From PCT Int Appl 2013; WO
2013132718 A1: 20130912.
[22] T. Gessner, S. Ebert, R. Sens, M. Konnemann, W. Ahlers, C. Wamvakaris Use of aryl-
or alkyloxy-substituted phthalocyanines as marking substances for liquids. From PCT
Int. Appl. 2007; WO 2007/04685 A1: 2007104685.
[23] M. Durmuş, V. Ahsen, J. Inorg. Biochem. 104 (2010) 297–309.
[24] S. Swavey, M. Tran, in L.M. Davids (Ed.), Recent Advances In The Biology, Therapy
and Management of Melanoma, Porphyrin and Phthalocyanine Photosensitizers as
PDT Agents: A New Modality for the Treatment of Melanoma, In Tech, Rijeka,
Croatia, 2013, pp. 253–282.
[25] M. Pişkin, M. Durmuş, M. Bulut, Spectrochim. Acta Part A 97 (2012) 502–511.
[26] R. Bayrak, H.T. Akçay, M. Pişkin, M. Durmuş, Dyes Pigm. 95 (2012) 330–337.
20

[27] S. Vagin, M. Hanack, Eur. J. Org. Chem. 14 (2003) 2661–2669.
[28] M.V. Martinez-Diaz, G.D.L. Torre, T. Torres, Chem. Commun. 46 (2010) 7090–7108.
[29] F.J.M. Hoeben, M.J. Pouderoijen, A.P.H.J. Schenning, E.W. Meijer, Org. Biomol.
Chem. 4 (2006) 4460–4462.
[30] A. Aktaş, M. Pişkin, M. Durmuş, H. Kantekin, J Lumin 145 (2014) 899–906.
[31] M. Pişkin, M. Durmuş, M. Bulut, J. Photochem. Photobiol. A 223 (2011) 37–49.
[32]
J.M. Penarrieta, T. Salluca, L. Tejeda, J.A. Alvarado, B. Bergenstahl, J. Food Compos.
Anal. 24 (2011) 580–587.
[33] M.A. Soobrattee, V.S. Neergheen, A. Luximon-Ramma, O.I. Aruoma, T. Bahorun,
Mutat. Res. 579 (2005) 200–213.
[34] I. Dalle-Donne, R. Rossi, R. Colombo, A. Giustarini Milzani, Clin. Chem. 52 (2006)
601.
[35] B. Halliwell, The Lancet. 344 (1994) 721–738.
[36] E. Gürel, M. Pişkin, S. Altun, Z. Odabaş and M. Durmuş, Dalton Trans. 44 (2015)
6202–6211.
[37] Z. Chen, C. Zhong, Z. Zhang, Z. Li, L. Niu, Y. Bin and F. Zhang, J. Phys. Chem. B,
112 (2008) 7389–7394.
[38] M.J. Stillman, T. Nyokong, in: C.C. Leznoff, A.B.P. Lever (Eds.). Phthalocyanines:
Properties and Applications, vol. 1, Chapter 3, VCH Publishers, New York, 1989.
[39] T. Nyokong, in:J. Jiang, D.M.P. Mingos (Eds.), Structure and Bonding, Functional
Phthalocyanine Molecular Materials, Electronic spectral and electrochemical
behaviour of near infrared absorbing metallophthalocyanines, vol.135, Springer, New
York, 2010, pp. 45–87.
[40] A.B. Anderson, T.L. Gorden, M.E. Kenney, J. Am. Chem. Soc. 107 (1985) 192–195.
[41] M. Konami, M. Hatano, A. Tajiri, Chem. Phys. Lett. 166 (1990) 605–618.
21

[42] A.M. Master, M.E. Rodriguez, M.E. Kenney, N.L. Oleinick, A.S. Gupta, J. Pharm.
Sci. 99 (2010) 2386–2398.
[43] S.C.H. Leung, P.C. Lo, D.K.P. Ng, W.K. Liu, K.P. Fung, W.P. Fong, Brit. J.
Pharmacol. 154 (2008) 4–12.
[44] Y.S. Li, S.I.A. Zaidi, M.A.J. Rodgers, H. Mukhtar, M.E. Kenney, N.L. Oleinick, J. He,
H.E. Larkin, B.D. Rihter, Photochem. Photobiol. 65 (1997) 581–586.
[45] R. Decreau, M.J. Richard, P.Verrando, M. Chanon, M. Julliard, J. Photochem.
Photobiol. B 48 (1999) 48–56.
[46] X.J. Jiang, P.C. Lo, Y.M. Tsang, S.L. Yeung, W.P. Fong, D.K.P. Ng, Chem. Eur. J. 16
(2010) 4777–4783.
[47] M. Çamur, M. Durmuş, M. Bulut, J. Photochem. Photobiol. A 222 (2011) 266–275.
[48] M. Durmuş, T. Nyokong, Polyhedron 26 (2007) 2767–2776.
[49] Z. Odabaş, E.B. Orman, M. Durmuş¸ F. Dumludağ, A.R. Özkaya, M. Bulut, Dyes
Pigm. 95 (2012) 540–552.
[50] M. Konami, M. Hatano, A. Tajiri, Chem. Phys. Lett. 166 (1990) 605–608.
[51] A. Tuhl , W. Chidawanayika, H.M. Ibrahim, N. Al-Awadi, C. Litwinski, T.
Nyokong, H. Behbehani, H. Manaa, S. Makhseed, J. Porphyrins Phthalocyanines 16
(2012) 163–174.
[52] P. Zimcik, V. Novakova, K. Kopecky, M. Miletin, R.Z.U. Kobak ,
E.
Svandrlikova, L. Váchová, K. Lang , Inorg. Chem. 51 (2012) 4215–4223.
[53] N. Kobayashi, H. Ogata, N. Nonaka, E.A. Luk'yanets, Chem. Eur. J. 9 (2003) 5123–
5134.
[54] M. Durmuş, T. Nyokong, Tetrahedron 63 (2007) 1385–1394.
[55] M. Durmuş, T. Nyokong, Spectrochim. Acta Part A 69 (2008) 1170–1177.
[56] V. Chauke, M. Durmuş, T. Nyokong, J. Photochem. Photobiol. A 192 (2007) 179–187.
22

[57] M. Pişkin, M. Durmuş, M. Bulut, Inorg. Chim. Acta 373 (2011) 107–116.
[58] A. Nas, Ü. Demirbaş, M. Pişkin, M. Durmuş, H. Kantekin, J. Lumin. 145 (2014) 635–
642.
[59] M. Pişkin, M. Durmuş, M. Bulut, J. Photochem. Photobiol. A 223 (2011) 37–49.
[60] E.N. Kaya, M. Durmuş, M. Bulut, J. Organomet. Chem. 774 (2014) 94–100.
[61] M. Durmuş, in: T. Nyokong, V. Ahsen (Eds.), Photosensitizers in Medicine,
Environment, and Security, Photochemical and Photophysical Characterization,
Springer, New York, 2012, pp.135-267.
[62] G. Schnurpfeil, A.K. Sobbi, W. Spiller, H. Kliesch, D. Wöhrle, J Porphyrins
Phthalocyanines 1 (1997) 159−167.
[63] Y. Zorlu, F. Dumoulin, M. Durmuş, V. Ahsen, Tetrahedron 66 (2010) 3248–3258.
[64] D.M. Maree, N. Kuznetsova, T. Nyokong, J. Photochem. Photobiol. A 140 (2001)
117–125.
[65] S. D’Souza, S. Moeno, T. Nyokong, Polyhedron 85 (2015) 476–481.
23

Figure Captions
Scheme 1. Synthesis of 2,4,6-trimethylphenoxy substituted phthalonitriles (1 and 2) and their
phthalocyanine derivatives (3-8). Reagents and conditions: (i) N2, K2CO3, DMSO, 50o C, 36
hrs. (ii) N2, DMF, DBU, 360o C, 20 min.; (iii) N2, Zn(CH3COO)2.2H2O or In(CH3COO)3,
DMF, 360o C, 20 min.
Fig. 1. Electronic absorption spectra of (a) In(OAc)Pc (unsubstituted In(OAc)Pc, 3 and 4),
(b) ZnPcs (5 and 6) and (c) H2Pcs (7 and 8) in DMF at 1.0x10−5 M.
Fig. 2. Electronic absorption spectra of H2Pc 8 in different solvents.
Fig. 3. Electronic absorption spectra of non-peripheral substituted In(OAc)Pc 3 in DMF at
different concentrations. (Inset: plots of absorbance versus concentration).
Fig. 4. Electronic absorption spectra of the ZnPcs 5 (a) and 6 (b) in different solvents.
Fig. 5. Absorption, excitation and emission spectra of the In(OAc)Pc 4 (a), ZnPc 6 (b) and
H2Pc 8 (c) in DMF. Excitation wavelength = 651 nm for 4, 651 nm for 6 and 641 nm for 8.
Fig. 6. Time correlated single photon counting (TCSPC) trace for ZnPc 6 in DMF with
residuals. Excitation wavelength = 651 nm.
Fig. 7. Typical spectral changes for the determination of singlet oxygen quantum yield of (a)
In(OAc)Pc 4, (b) ZnPc 6 and (c) H2Pc 8 in DMF. (Inset: plots of DPBF absorbance versus
time). Concentration = 1×10−5 M.
Fig. 8. Typical spectral changes for the determination of photodegradation quantum yields of
substituted (a) In(OAc)Pc 3, (b) ZnPc 5 and (c) H2Pc 7 in DMF. (Inset: plot of Q band
absorbance versus time). Concentration = 1×10−5 M.
24

Scheme 1.
25

Fig. 1
26

Fig. 2
27

Fig. 3
28

Fig. 4
29