Metallophthalocyanines bearing four 3-(pyrrol-1-yl)phenoxy units as photosensitizer for dye-sensitized solar cells

Accepted Manuscript Metallophthalocyanines bearing four 3-(pyrrol-1-yl)phenoxy units as photosensitizer for dye-sensitized solar cells Merve Pamukçu Polat, H. Yasemin Yenilmez, Atıf Koca, Ahmet Altındal, Zehra Altuntaş Bayır PII:

S0143-7208(18)30321-8

DOI:

10.1016/j.dyepig.2018.04.019

Reference:

DYPI 6680

To appear in:

Dyes and Pigments

Received Date: 9 February 2018 Revised Date:

15 March 2018

Accepted Date: 10 April 2018

Please cite this article as: Polat MervePamukç, Yenilmez HY, Koca Atı, Altındal A, Bayır ZehraAltuntaş, Metallophthalocyanines bearing four 3-(pyrrol-1-yl)phenoxy units as photosensitizer for dye-sensitized solar cells, Dyes and Pigments (2018), doi: 10.1016/j.dyepig.2018.04.019. 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.

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Graphical Abstract

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Metallophthalocyanines bearing four 3-(pyrrol-1-yl)phenoxy

2

units as photosensitizer for dye-sensitized solar cells

3

Merve Pamukçu Polat,a H. Yasemin Yenilmez,a Atıf Koca,b Ahmet Altındal,c Zehra Altuntaş

4

Bayıra*

5

a

6

Maslak, Istanbul, Turkey

7

b

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Turkey

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c

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Department of Chemistry, Faculty of Science and Letters, Istanbul Technical University, 34469

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Department of Chemical Engineering, Engineering Faculty, Marmara University, İstanbul,

Department of Physics, Faculty of Science and Letters, Yıldız Technical University, 34220

10

Esenler, Istanbul, Turkey

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*

Corresponding author: Zehra Altuntaş Bayır ([email protected])

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12 Abstract

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In this article, the synthesis of non-peripheral metallophthalocyanines (cobalt, zinc, and

15

manganese) bearing four 3-(pyrrol-1-yl)phenoxy units was reported. The new compounds have

16

been characterized using UV-Vis, FT-IR, 1H NMR, and mass spectroscopic data. Aggregation

17

behaviors of phthalocyanines were investigated in concentrations ranging from 14 × 10−6 to 2 ×

18

10−6 M. Electrochemical measurements gave well illustrated redox activities of MnClPc and

19

CoPc. Electrochemical and spectroelectrochemical studies showed that MnClPc gives two metal-

20

based reduction processes in addition to the one ring-based reduction and one ring-based

21

oxidation process. Distinct color differences between the electrogenerated MnClPc species were

22

observed during in situ spectroelectrochemical measurements. The potential of these compounds

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as photosensitizers and dependence of the photovoltaic performance on the thickness of

2

photoanode layer were investigated. For this purpose, DSSC devices were fabricated with the

3

structure of FTO/TiO2:4-6/Electrolyte/Pt/FTO and characterized under AM 1.5 illuminations. By

4

using 6 as dye a photovoltaic conversion efficiency of 2.44 % with short circuit current density

5

of 7.17 mA cm-2 and open circuit voltage of 0.68 V was observed.

6

Keywords:

7

spectroelectrochemistry, DSSC

8

1. Introduction

9

Phthalocyanine derivatives (Pcs) are planar compounds in which four isoindole are connected to

10

each other by aza bridges [1]. They are similar to the compound found in nature, such as

11

porphyrins and chlorins [2]. The Pcs are not found in the nature; they are chemically synthesized

12

in laboratory. Phthalocyanines have extraordinary applications and the number is ever increasing

13

rapidly in recent years. The key applications include PDT, eletrochromism, chemical sensors,

14

optical limiting devices, dyes and pigments [3-6].

15

Renewable energy is becoming increasingly important as fossil fuels in the world are depleted in

16

the near future. Solar cell that convert electricity from solar energy to electricity are a good

17

alternative. A typical solar cell thus needs at least three key components: a light-absorber (dye), a

18

hole-transport agent, and an electron-transport agent. The first requirement is the harvesting of a

19

significant fraction of the solar spectrum. Roughly half the total energy of sunlight appears at

20

wavelengths below 700 nm, a region typically covered well by the porphyrin and phthalocyanine

21

families. Dye sensitized solar cells (DSSCs) have been attracted by scientific and industrial

22

circles since they were introduced in 1991 by O’Regan and Grätzel [7]. Among the photovoltaic

23

device, dye-sensitized solar cells (DSSCs) appear the most promising alternative to traditional

pyrrole,

photosensitizer,

electrochemistry,

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non-peripheral,

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Phthalocyanine,

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silicon based devices because of their low production cost, and high conversion efficiency [3, 8].

2

The function of dye sensitized solar cells (DSSCs) is based upon photoinduced electron injection

3

from the molecular excited state of a given organic dye (Pc) into the conduction band of a

4

nanocrystalline metal oxide film (TiO2). In practice, polypyridylruthenium complexes are widely

5

used as dye molecules in DSSC [9]. However, the main drawback of these complexes is their

6

lack of absorption in the red region of the visible solar spectrum [10].

7

Phthalocyanine (Pc) derivatives are also suitable DSSC sensitizers because of their intense

8

absorption in the red to NIR, light-harvesting ability, low-cost, and extraordinary thermal as well

9

as photochemical stability [11-13]. It is necessary to absorb about 700 nm in order to use the

10

phthalocyanines. Their high molar extinction coefficients (over 100.000 M-1cm-1) allows an

11

efficient photon harvesting. In addition, redox features of phthalocyanines allow sensitization of

12

the wide band gap semiconductors like titania. Nevertheless, the power conversion efficiency of

13

phthalocyanine dyes in DSSCs is generally low.

14

The most commonly used method is that a starting material (phthalonitrile, 1,3-

15

diiminoisoindoline, o-cyanobenzamide, phthalimide or phthalic anhydride) is heated in a high-

16

boiling solvent with/without a metal salt [14]. The largest disadvantage of Pcs is their low

17

solubility in organic solvents. The peripheral or non-peripheral substitution on the Pc ring

18

increases the solubility. Long chain alkyl, phenoxy, alkoxy or alkylthio substituents are mostly

19

used [15-17]. Pyrrole, which has many derivatives in nature, is an important class of heterocycles

20

[18]. The studies about having pyrrole-substituted phthalocyanines are rare [19]. In this study,

21

the synthesis, characterization, and structural investigation of Co(II), Zn(II), and Mn(Cl) Pcs

22

containing 4-(pyrrol-1-yl)phenoxy groups are described. Furthermore, the electrochemical,

23

spectroelectrochemical, and solar cell properties of the phthalocyanines were investigated.

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2. Experimental

2

2.1. Materials and equipments

3

The analyses of the compounds were made with the facilities of our university. 3-

4

nitrophthalonitrile (1) and 4-(pyrrol-1-yl)phenol (2) was obtained from Sigma Aldrich.

5

2.2. Synthesis

6

2.2.1. 3-(4-pyrrol-1-yl)phenoxyphthalonitrile (3)

7

3-Nitrophthalonitrile (1) (0.59 g, 3.00 mmol) was dissolved in 20 mL of dry DMF and 4-(pyrrol-

8

1-yl)phenol (2) (0.58 g, 3.65 mmol) was added. After stirring for 15 min, 1.06 g of finely ground

9

anhydrous K2CO3 (7.69 mmol) was added in small portions over 2 h with efficient stirring. The

10

mixture was stirred under a nitrogen stream for 48 h. Then the mixture was poured into a crushed

11

ice-water mixture. The resulting yellowish solid was collected by filtration and washed with

12

water and cold methanol. Yield: 0.79 g, (92%), mp 169°C. FT-IR ν (cm−1): 3081 (aromatic C–

13

H), 2228 (C≡N), 1577, 1514, 1464, 1268, 1204, 1070, 855, 799, 725. 1H NMR (DMSO-d6): δ,

14

ppm 7.84 (s, 2H), 7.71-7.69 (d, 2H), 7.39 (s, 2H), 7.35-7.34 (d, 2H), 7.32-7.30 (d,1H), 6.28 (s,

15

2H). 13C NMR (500 MHz; DMSO-d6): δ ppm 160.50 (aromatic C), 151.57 (aromatic C), 138.10

16

(aromatic C), 136.49 (aromatic C), 128.63 (aromatic C), 122.26 (aromatic C), 121.88 (aromatic

17

C), 121.67 (aromatic C), 119.60 (aromatic C), 116.34 (C≡N), 116.10 (C≡N), 113.86 (aromatic

18

C), 111.12 (aromatic C), 105.44 (aromatic C).

19

2.2.2. Synthesis of metallo-phthalocyanines

20

The phthalonitrile derivative 3 (0.150 g, 0.530 mmol) and 0.16 mmol of the metal salt (CoCl2:

21

0.021 g; Zn(OAc)2: 0.029 g; MnCl2: 0.020 g) were heated in 2-dimethylaminoethanol (2 mL) at

22

145°C under N2. After stirring for 24 hours, the suspension was cooled and then added dropwise

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to methanol (50 mL). The precipitate was washed several times with methanol and acetone to

2

remove the unreacted materials. The product is purified by different methods.

3

1,8(11),15(18),22(25)-Tetrakis [4-(pyrrol-1-yl)phenoxy] phthalocyaninatocobalt(II)(4): The blue

4

product was chromatographed over silicagel with methanol as eluent to remove impurities. The

5

column was then eluted with ethyl acetate. Yield: 0.033 g (21%). IR νmax/cm-1: 3016 (C-H,

6

aromatic), 1738, 1509, 1478, 1231 (C-O-C), 1068, 718. UV–vis (THF, c = 6×10-6 mol dm-3),

7

λmax, nm (log e): 323 (4.89), 678 (5.21). MS (ESI-TOF): 1200.29 [M]+. For C72H44CoN12O4

8

Anal. calc.: C, 72.06; H, 3.70; N, 14.01%. Found: C, 72.25; H, 3.60; N, 13.84 %.

9

1,8(11),15(18),22(25)-Tetrakis [4-(pyrrol-1-yl)phenoxy] phthalocyaninatozinc(II) (5): The green

10

product was purified by chromatography on silica gel using first methanol and then ethyl acetate

11

as eluent. Yield: 0.039 g (25%). IR νmax/cm-1: 3060 (C-H, aromatic), 1512, 1481, 1242 (C-O-C),

12

1116, 724. 1H NMR (DMSO-d6): δ, ppm 9.07-7.20 (m, 36H), 6.24-6.18 (d, 8H). UV–vis (THF, c

13

= 6×10-6 mol dm-3), λmax, nm (log e): 343 (4.86), 692 (5.46). For C72H44ZnN12O4 Anal. calc.: C,

14

71.67; H, 3.68; N, 13.93%. Found: C, 71.77; H, 3.43; N, 13.96 %.

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1,8(11),15(18),22(25)-Tetrakis

[4-(pyrrol-1-yl)phenoxy]

phthalocyaninato(chloro)-

17

manganese(III) (6): The brown product was chromatographed over silicagel with methanol and

18

then THF as eluent. Yield: 0.024 g (15%). IR νmax/cm-1: 3016 (C-H, aromatic), 1738, 1508, 1230

19

(C-O-C), 1114, 1068, 718. UV–vis (THF, c = 6×10-6 mol dm-3), λmax, nm (log e): 350 (4.69), 505

20

(4.01), 742 (4.98). MS (ESI-TOF): 1231.27 [M]+, 1195.30 [M-Cl]+. For C72H44MnClN12O4 Anal.

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calc.: C, 70.22; H, 3.60; N, 13.65%. Found: C, 70.43; H, 3.72; N, 13.50 %.

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2.3. Electrochemical and in situ spectroelectrochemical measurements

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The cyclic voltammetry (CV), square wave voltammetry (SWV), controlled potential coulometry

2

(CPC) and in situ spectroelectrochemical (SEC) measurements were performed by following

3

procedure given in the published paper [20]. For electrochemical measurements, a potentiostat

4

(GAMRY Instruments, Reference 600 Potentiostat/Galvanostat/ZRA) utilizing a three-electrode

5

cell configuration at 25°C was used with a glassy carbon working electrode (GCE) with a surface

6

area of 0.071 cm2 (diameter of the electrodes are 3 mm), a Pt wire counter electrode and a

7

pseudo--silver|silver chloride (Ag|AgCl) reference electrode. An OceanOptics QE65000 diode

8

array spectrophotometer was used for SEC measurements with a Pt gauze-working electrode by

9

utilizing a three-electrode configuration of thin-layer quartz spectroelectrochemical cell.

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2.4. Fabrication and characterization of DSSCs

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As working electrode, nanoporous TiO2 paste coated fluorine-doped tin oxide (FTO) conducting

12

glasses were used. After standard surface cleaning procedure, the surface of the FTO substrates

13

was covered with a nanocrystalline TiO2 paste with various thickness ranging from 4 to 10 µm.

14

The TiO2 paste was prepared as described [21]. Briefly, the mixture of 1.2 g TiO2 nano powder,

15

10 mL ethanol, 5 mL terpineol and 6 mL ethyl celluloses in absolute ethanol was concentrated at

16

60°C for 24 h and then applied onto FTO by doctor blade. After annealing at 440 °C for 20 min,

17

the TiO2 coated electrodes were immersed in acetone containing 15 mg 4, 5 or 6 for 20 h at room

18

temperature to obtain dye-sensitized TiO2 photoanode. The DSSCs were formed by clipping the

19

TiO2 photoanode and Pt counter electrode, a drop of electrolyte containing 0.6 M 1-butyl-3-

20

methylimidazolium iodide, 0.3 M lithium iodide, 0.07 M iodine and 0.6 M tert-butylpyridine in a

21

mixture of acetonitrile:valeronitrile (85:15). The DSSC devices were characterized by means of

22

current-voltage (I-V) measurements under simulated solar light (AM1.5G, 100 mW cm−2

23

irradiance).

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3. Results and discussion

2

3.1. Synthesis and characterization

3

Preparation of the intended phthalocyanine requires the synthesis of dinitrile as the first step. 3-

4

(4-pyrrol-1-yl)phenoxyphthalonitrile

5

nitrophthalonitrile and 4-(pyrrol-1-yl)phenol in DMF (Scheme 1). In nucleophilic aromatic

6

displacement reaction, potassium carbonate was used as a base [22]. Cyclotetramerization of the

7

dinitrile derivatives (3) to the corresponding metallo-phthalocyanines (4-6) was accomplished in

8

the presence of anhydrous metal salts in 2-dimethylaminoethanol (Scheme 1). Spectral data (FT-

9

IR, UV-Vis, 1H NMR, 13C NMR and MALDI-TOF) and elemental analyses for the synthesized

by

the

reaction

between

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prepared

3-

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was

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(3)

compounds are consistent with the the predicted structure. NO 2

NC

HO

+

N

NC

i

N

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O

NC

NC

3

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N

N

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ii

O

O

N

N

N

N

M N

N

N N

O

O

N

N

4 5 6 M Co Zn MnCl

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Scheme 1. Synthesis of the phthalonitrile derivative (3) and the corresponding phthalocyanines

13

4–6.

14

(dimethylamino)ethanol, 145 °C, 24h.

(i)

K2CO3,

DMF,

rt.

(ii)

Metal

salts

(CoCl2,

Zn(CH3COO)2,

MnCl2),

2-

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In the FT-IR spectrum of the dinitrile compound, the appearance of an absorption band at 2228

2

cm-1 (C≡N) confirms the formation of the product [23, 24]. In the 1H NMR spectrum of the

3

dinitrile (3), the aromatic protons appear at 7.84 (s), 7.71-7.69 (d), 7.39 (s), 7.35-7.34 (d), 7.32-

4

7.30 (d), and 6.28 (s). In the 13C NMR spectrum of the compound 3, the aromatic carbon atoms

5

were observed between 105.44 and 160.50 ppm. The nitrile carbon atoms for 3 were observed at

6

116.34 and 116.10 ppm. After converting to phthalocyanine derivatives, the C≡N peak is

7

disappearing in the FT-IR spectrum. The FT-IR spectra of the metallo-phthalocyanines (4–6) are

8

very similar to each other. Aromatic CH and C-O-C vibrations were observed about 3060–3016

9

and 1242–1231 cm-1, respectively. In the 1H NMR spectrum of 5, 36 aromatic protons at 9.07–

10

7.20 ppm and 8 aromatic protons at 6.24-6.18 ppm were observed. Mass spectra of the cobalt and

11

manganese phthalocyanines support the structures.

12

The UV-vis spectrum is used as an important characterization method for phthalocyanines [25].

13

The π conjugated system caused two strong absorptions in the UV-vis region to phthalocyanine

14

compounds due to its delocalized electronic structure throughout the ring. The UV–vis spectrum

15

of CoPc (4) and ZnPc (5) in THF exhibited a typical B-band at 323, 343 nm and a Q band at 678,

16

692 nm, respectively. The UV–vis spectrum of manganese phthalocyanine (6) in THF exhibited

17

the B band at 350 nm and the intense Q band at 742 nm. Furthermore, MnClPc (6) shows an

18

absorption at 505 nm, which was interpreted as a charge transfer absorption (phthalocyanine →

19

metal, LMCT) [26].

20

The absorption maxima of metallo-phthalocyanines shifts to the longer wavelength in the order

21

of cobalt (Co), zinc (Zn) and manganese (Mn) as the central metal [26]. The Q band absorption

22

of the new phthalocyanines is shifted by 14-25 nm to longer wavelengths in comparison to the

23

peripheral-substituted phthalocyanines [27]. In this study, the aggregation behavior of the

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phthalocyanine derivatives (4-6) were examined at different concentrations in THF [28]. The

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metallo-phthalocyanines did not show any aggregation in THF (Figure 1). The Beer– Lambert

3

law was obeyed for the phthalocyanines at concentrations ranging from 14 × 10−6 to 2 × 10−6 M.

4

Only a decrease of the intensity was observed in the band. No new band formation has been

5

observed belonging to aggregation.

0.6 0.4 0.2 0 300

Absorbance

3.5 3

1.60E-05

500 600 Wavelength / nm

700

2.5 2

4.5 4 3.5 y = 284502x R² = 0,9921 3 2.5 2 1.5 1 0.5 0 0.00E+00 4.00E-06 8.00E-06 1.20E-05 Concentration /M

A B C D E F G

1.60E-05

1.5

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0

300

400

500 600 700 Wavelength / nm

A B C D E F G

800

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Absorbance

4.00E-06 8.00E-06 1.20E-05 Concentration /M

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400

y = 59042x R² = 0.987

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Absorbance

0.8

0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0.00E+00

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800

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2 1.6

1.8

1.4 Absorbance

1.2

1.6

y = 97770x R² = 0,9696

0.6 0.4

1.2

A B C D E F G

0.2 0 0.00E+00

1

4.00E-06 8.00E-06 1.20E-05 Concentration /M

1.60E-05

0.8 0.6 0.4 0.2 0 400

500 600 Wavelength / nm

700

800

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Absorbance

1.4

1 0.8

Fig. 1. Aggregation behavior of 4-6 in THF at different concentrations: 14 × 10−6 (A), 12 × 10−6 (B), 10 × 10−6 (C), 8 × 10−6 (D), 6 × 10−6 (E), 4 × 10−6 (F), and 2 × 10−6 (G) M.

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Molecular structure of the dye molecule and the thicknesess of the photoanode (TiO2 in DSSC

6

devices) are two determining factors for achieving high performance DSSC. A number of DSSC

7

devices with different TiO2 thickness using the Pcs 4–6 as dye were fabricated. The photovoltaic

8

performance of the dye molecules in DSSCs was investigated by measuring J-V characteristics.

9

Figure 2 compares the photovoltaic behavior of the compounds with structure of FTO/TiO2 (8

10

µm):4, 5 or 6/Electrolyte/Pt/FTO under AM 1.5 illumination conditions. From the measured J-V

11

characteristics, short-circuit current density (JSC), open circuit voltage (VOC), fill factor (FF) and

12

photovoltaic conversion efficiency (η) were obtained, which are the basic performance

13

parameters. Here η, as usual, is defined as

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3.2 Photovoltaic performances

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η=

VOC × JSC × FF × 100 Pin

(1)

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where, Pin is defined as the energy of incident sunlight. Analysis of the data presented in Figure 2

16

and comparing the J-V characteristics of the devices, indicate the that the most improved

17

photovoltaic

conversion

efficiency

was

obtained

with

the

structure

of

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FTO/TiO2:6/Electrolyte/Pt/FTO and the order of the observed photo-voltaic conversion

2

efficiency values for the devices investigated is as follows: 6 > 4 > 5.

3

The photovoltaic conversion efficiency of 6 based device is 2.44%, with an open circuit voltage

4

of 0.68 V and short circuit current density of 7.17 mA/cm2. As can be seen from the Figure 2, the

5

main drawback with 4 and 5 based DSSC devices are their low open-circuit voltages and short

6

circuit current density. Figure 2 also shows that the dependence of the open circuit voltage on the

7

kind of central atom is relatively weak for 4 and 5 based devices. On the other hand, short circuit

8

current, which is another important efficiency determining parameter for DSSC, exhibits strong

9

dependence on the central metal atom. The obtained results illustrate the importance of

10

understanding the predominance of central metal atom in dye molecule. Actually, it is not an

11

easy task to conclude the effect of the central metal atom of dye molecule on the device

12

performance, especially the short circuit current density of the DSSC device since the

13

interactions can take place in various ways.

14

In a DSSC, two determining factors are the exciton dissociation and injection of charges to the

15

conduction band of the TiO2 from the lowest unoccupied molecular orbital (LUMO) energy level

16

of the photo-excited dye. The effectively collection of the injected electrons by the anode and

17

cathode material are the other two determining factor for photo-conversion efficiency and

18

therefore, the short circuit current. The LUMO energy and the highest occupied molecular

19

(HOMO) energy levels of dye molecule have great significance for further improvement in JSC.

20

In this respect, the dye molecule used should fulfill some basic requirements such as, its LUMO

21

level should be more negative than the conduction band energy of the photoanode and HOMO

22

level more positive than the redox potential of the electrolyte used [29]. In addition, high

23

extinction coefficients and absorption in the visible region of the electromagnetic spectrum are

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also important for improved JSC. The large coverage of the absorption spectrum lead to more

2

photogeneration of charge carriers and enhanced short-circuit current. The observed high short-

3

circuit current density for 6 based devices can be attributed to the red shift in its absorption

4

spectra. As mentioned above, the open circuit voltage of the 4 and 5 based devices is relatively

5

less sensitive to the kind of central metal atom. It is expected that the open circuit voltage in a

6

DSSC device depends on the difference between the quasi-Fermi level of the electrons in

7

photoanode and the redox potential of electrolyte [30]. The same electrolyte was used in all

8

devices, therefore the observed higher open circuit voltage value 6 sensitized DSSC as compared

9

to 4 and 5 can be related to better injection of electrons into the conduction band of photoanode

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from the excited dye of 6.

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Fig. 2. J–V characteristics of the DSSC devices with the structure of FTO/TiO2 (8 µm):4-

13

6/Electrolyte/Pt/FTO.

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1 2

Table 1 The effect of the thickness of the photoanode layer on photovoltaic performance of

3

the FTO/TiO2: 6/Electrolyte/Pt/FTO device Jsc (mA cm-2)

Voc (V)

Pmax (mW)

FF

η (%)

4

3.92

0.65

1.37

0.54

1.38

5

4.35

0.66

1.49

0.52

1.49

6

4.86

0.66

1.43

0.44

1.44

7

5.43

0.66

1.66

8

7.17

0.68

2.44

9

6.74

0.67

2.36

0.50

2.36

10

6.26

0.68

2.16

0.44

2.18

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Thickness (µm)

1.67

0.57

2.44

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0.46

The effect of the thickness of the photoanode on the performance of the devices, the thickness of

5

the TiO2 photoanode was varied from 4 to 10 µm. Figure 3 compares the J-V characteristics of 6

6

based cells prepared using different thicknesses of TiO2 photoanode. The obtained photovoltaic

7

performance parameters of the investigated devices are tabulated in Table 1 for numerical

8

comparison. An investigation of Figure 3 and Table 1 indicates that the JSC value for 4 µm TiO2

9

photoanode is 3.92 mA cm-2 and VOC is 0.65 V, corresponding to an overall photovoltaic

10

conversion efficiency of 1.37%. It is also clear from the same table that the JSC value increases

11

with further increase of photoanode layer thickness and reaches to 7.17 mA cm-2 for 8 µm

12

thickness of TiO2 layer. It was observed that further increase in photoanode thickness from 8 µm

13

to 9 µm results in a decrease in short-circuit current density. It should be noted here that the

14

values of the open circuit voltage is unaffected from the thickness of the photoanode layer. These

15

findings are consistent with the literature. Recently, Shin et al. [31] concluded that the charge

16

transfer resistance at the phototoanode:dye/electrolyte interface decreases with increasing

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phototoanode thickness. The decrease in charge transfer resistance at the interface facilitates the

2

transport process for the injected electrons in the photoanode layer and results in improvement of

3

JSC. It was reported in previous studies that the thickness of the photoanode layers have a strong

4

effect on the short circuit current of a DSSC, but less on open circuit voltage.

5

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Fig. 3. The effect of the thickness of the photoanode layer on the J-V characteristics of 6 based

7

DSSC device.

8

Another reasonable explanation for the increase in short circuit current with the increasing

9

photoanode layer thickness can be given as follows; with the increase of TiO2 layer, more dye

10

molecules adsorbed/absorbed by the TiO2, which increases the number of the absorbed photon

11

and lead to an improvement of the electron injection into the conduction band of TiO2.

12

However, it was also reported that the increase in photoanode layer thickness leads to the

13

increase in recombination rate, arising from low drift mobility of electrons in the photoanode

14

layer which leads to a drop in the conversion efficiency.

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3.3. Electrochemical and Spectroelectrochemical Measurements

2

MPcs having redox active metal centers were used as functional materials in various

3

technological applications, such as electrocatalytic, electrosensing and electrochromic fields.

4

Most of the application areas of MPcs depends on their electrochemical properties. Therefore

5

electrochemical characterizations of ClMnIIIPc and CoIIPc were performed in detail with CV,

6

SWV and in situ spectroelectrochemistry. Both ClMnIIIPc and CoIIPc illustrated well defined

7

redox responses, which are in harmony with the reported MPcs [19, 32-37]. CV, SWV and SEC

8

responses of the complexes are analyzed and the results are tabulated in Table 2. ClMnIIIPc and

9

CoIIPc gave metal based reduction processes before the Pc based processes due to the locations

10

of the empty d orbitals of the metal centers between HOMO and LUMO of Pc ring. In order to

11

illustrate the solvent effects, electrochemical analyses were performed in DCM (nonpolar) and

12

DMSO (polar). Figure 4 shows the CV and SWV responses of ClMnIIIPc in DCM/TBAP on

13

GCE working electrode. ClMnIIIPc illustrates three reductions, Red1 at -0.05 V, Red2 at -0.57 V

14

and Red3 at -1.40 V and one oxidation at Ox1 at 1.10 V. Reduction processes are

15

electrochemically and chemically reversible with respect to ratio of anodic to cathodic peak

16

currents (Ip,a/Ip,c), peak to peak potential separations (∆Ep). While MPcs having redox inactive

17

metal centers generally give the first reduction process after -0.60 V, this process is observed at

18

0.05 V due to reduction of MnIII center of ClMnIIIPc to ClMnII. The second reduction of the

19

complex can easily be assigned to the metal based reduction, when compared with the

20

electrochemical responses of MnPcs in the literature. The half-wave potentials (E1/2) of the redox

21

processes and difference between first oxidation and reduction processes (∆E1/2) are in harmony

22

with the redox responses of MnPcs reported in the literature [32, 37]. The slight shifting of the

23

redox processes may be resulted from the feature of the substituents of the complex. Detailed

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assignments of the redox processes were performed with in situ spectroelectrochemistry

2

discussed below. ClMnIIIPc illustrates similar CV and SWV responses in DCM/TBAP with those

3

in DMSO/TBAP as shown in Figure 5. Although same redox processes are observed, due to the

4

different polarity of the solvents, ClMnIIIPc aggregates in DCM and the redox processes shift

5

slightly. Thus, redox peaks are split due to the electron transfer reactions of monomeric and

6

aggregated species. Reversibility of the redox processes decreases in DCM due to the

7

aggregation of the complex.

8

Table 2 Voltammetric data of the complexes. All data were given versus Ag/AgCl.

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1

9

a c b Redox processes E1/2 (V) ∆Ep (mV) Ip,a/Ip,c d∆E1/2 [Cl-MnIIIPc2-]/ [Cl-MnIIIPc1-]1+ 1.10 III 2II 2- 11.15 [Cl-Mn Pc ] / [Cl-Mn Pc ] -0.05 68 0.97 II 2- 1I 2- 2-0.57 75 0.90 (in DMSO) [Cl-Mn Pc ] / [Cl-Mn Pc ] I 2- 2I 3- 3[Cl-Mn Pc ] / [Cl-Mn Pc ] -1.40 72 0.86 III 2III 1- 1+ 1.07 67 0.93 [Cl-Mn Pc ]/ [Cl-Mn Pc ] Cl-MnPc III 2II 2- 11.07 [Cl-Mn Pc ] / [Cl-Mn Pc ] 0.00 69 0.93 II 2- 1I 2- 2[Cl-Mn Pc ] / [Cl-Mn Pc ] -0.94 75 0.62 (in DCM) I 2- 2I 3- 3[Cl-Mn Pc ] / [Cl-Mn Pc ] -1.37 97 0.54 III 2- 1+ III 1- 2+ 1.00 [ Co Pc ] / [Co Pc ] CoPc II 2III 2- 1+ [Co Pc ] / [Co Pc ] 0.28 (0.54) 98 0.42 0.64 II 2I 2- 1[Co Pc ] / [Co Pc ] -0.36 (-0.46) 85 0.56 (in DMSO) [CoIPc2-]1-/ [CoIPc3-]2-1.24 96 0.53 I 3- 2I 4- 3[Co Pc ] / [Co Pc ] -1.87 III 2- 1+ III 1- 2+ [ Co Pc ] / [Co Pc ] 1.04 100 0.44 CoPc II 2III 2- 1+ [Co Pc ] / [Co Pc ] 0.69 230 0.24 0.85 II 2I 2- 1[Co Pc ] / [Co Pc ] -0.16 (-0.32) 120 0.79 (in DCM) [CoIPc2-]1-/ [CoIPc3-]2-1.31 160 0.43 I 3- 2I 4- 3[Co Pc ] / [Co Pc ] a :E1/2 values (Epa+Epc)/2) were recorded at 0.100 Vs-1 scan rate. b: ∆Ep= Epa-Epc. c:Ip,a/Ip,c for

10

reduction ,Ip,c/Ip,a for oxidation processes. d:∆E1/2 = E1/2 (first oxidation)- E1/2 (first reduction).

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Complexes Cl-MnPc

11

e

:Epc values of the aggregated species recorded at 0.100 Vs-1 scan rate.

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10

15

(b)

(a)

Oxd1

10

0

Red1

-10

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Red1 0

Red2

-20

-1

-30

25 mVs -1 50 mVs -1 100 mVs -1 250 mVs -1 500 mVs

Red3

-5

-1

25 mVs -1 50 mVs -1 100 mVs -1 250 mVs -1 500 mVs

-10 -15

-40 -2.0

-1.5

-1.0

-0.5

0.0

-0.5

0.5

1.0

1.5

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(c)

(d)

15

15

Oxd1

Red1

10

10

5

5

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0.5

E (V) vs. Ag/AgCl

E (V) vs. Ag/AgCl 20

0.0

SC

I (µA)

5

0

Red2

-15

-5

Red1

-10

-20 -1.5

EP

Red3

-1.0

-0.5

1

AC C

E (V) vs. Ag/AgCl

0.0

-15 0.5

-0.5

0.0

0.5

1.0

E (V) vs. Ag/AgCl

2

Fig. 4. (a and b) CVs of ClMnIIIPc (5.0 x10-4 mol.dm-3) recorded at various scan rates and (c

3

and d) SWVs of ClMnIIIPc recorded at 0.100 Vs-1 scan rate on a GCE working electrode in

4

DCM/TBAP electrolyte.

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(b)

(a) 15

Oxd1

0

-1

25 mVs -1 50 mVs -1 100 mVs -1 250 mVs -1 500 mVs

Red3

-1

25 mVs -1 50 mVs -1 100 mVs -1 250 mVs -1 500 mVs

-15 -2.0

-1.5

-1.0

-0.5

0.0

0.5

-0.5

E (V) vs. Ag/AgCl

SC

-15

RI PT

Red1 Red2

Red1

I (µA)

I (µA)

0

0.0

0.5

20

M AN U

20

(c)

(d)

Oxd1

Red1

15

I (µA)

I (µA)

10

Red3

Red2

-20 -2.0

-1.5

TE D

-10

-15

-1.0

-0.5

Red1

0.0

0.5

1.0

-20 -0.5

0.0

0.5

1.0

E (V) vs. Ag/AgCl

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E (V) vs. Ag/AgCl

1

1.0

E (V) vs. Ag/AgCl

2

Fig. 5. (a and b) CVs of ClMnIIIPc (5.0 x10-4 mol.dm-3) recorded at various scan rates and (c

3

and d) SWVs of ClMnIIIPc recorded at 0.100 Vs-1 scan rate on a GCE working electrode in

4

DMSO/TBAP electrolyte.

5 6

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Figure 6 shows CV and SWV responses of CoIIPc in DMSO/TBAP. Due to the different redox

2

activity of the CoII center of the complex, CoIIPc shows different CV and SWV responses from

3

those of ClMnIIIPc. While two metal based reduction reactions are observed with ClMnIIIPc, one

4

metal based reduction and one metal based oxidation are observed with CoIIPc. Moreover, one

5

Pc-based reduction and one Pc-based oxidation are also observed as shown in Figure 6. The

6

redox processes of CoIIPc are generally quasi-reversible, and especially metal based redox

7

processes split due to the aggregation of the complex. Similarly, CoIIPc illustrated more

8

irreversible electron transfer reactions in DCM (Figure 7) and aggregation of the complex is

9

more dominant in DCM than DMSO.

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1

50

(a)

I (µA)

25

0

-25

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Red1

-50 -2.0

Red2

-1.5

-1.0

-0.5

-1

25 mVs -1 50 mVs -1 100 mVs -1 250 mVs -1 500 mVs

0.0

0.5

1.0

1.5

E (V) vs. Ag/AgCl

45 30

(b)

I (µA)

EP

15

0

Red3

Red2

Red1

Oxd1

Oxd2

0.5

1.0

AC C

-15 -30

-45 -2.5

10

-2.0

-1.5

-1.0

-0.5

0.0

1.5

E (V) vs. Ag/AgCl

11

Fig. 6. (a) CVs of CoIIPc (5.0 x10-4 mol.dm-3) recorded at various scan rates and (b) SWVs of

12

CoIIPc recorded at 0.100 Vs-1 scan rate on a GCE working electrode in DMSO/TBAP

13

electrolyte.

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45

(b)

(a)

Oxd2

15 30

Oxd1

Red1 -1

25 mVs -1 50 mVs -1 100 mVs -1 250 mVs -1 500 mVs

-30

Red2 -45 -2.0

-1.5

-1.0

-0.5

0

-1

25 mVs -1 50 mVs -1 100 mVs -1 250 mVs -1 500 mVs

-15

0.0

0.0

0.5

(c)

20

(d)

15

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Red2

I (µA)

I (µA)

10

0

1.0

1.5

E (V) vs. Ag/AgCl

E (V) vs. Ag/AgCl

SC

-15

15

RI PT

I (µA)

I (µA)

0

Red1

Oxd2

Oxd1

5 0

-5

-15

-10

-1.5

-1.0

-0.5

0.0

0.0

0.5

1.0

1.5

E (V) vs. Ag/AgCl

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E (V) vs. Ag/AgCl

1

Fig. 7. (a and b) CVs of CoIIPc (5.0 x10-4 mol.dm-3) recorded at various scan rates and (c and d)

3

SWVs of CoIIPc recorded at 0.100 Vs-1 scan rate on a GCE working electrode in DCM/TBAP

4

electrolyte.

5

Redox mechanism of the complexes and spectral responses and colors of the electrogenerated

6

species were determined with SEC measurements. Especially assignments of the first reduction

7

and first oxidation processes depends on the electrolytes. Thus, it is important to analyze these

8

processes in order to define an accurate mechanism. Figure 8 shows in-situ UV–vis spectral

9

changes of CoIIPc observed during the first reduction and first oxidation processes in DMSO

10

electrolyte. Neutral CoPc illustrates the Q band at 676 nm and the B band at 370 nm. Under -

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0.60 V applied potential (Red1), the Q band shifts from 676 nm to 711 nm and a new band

2

increases at 470 nm. These spectral changes are characteristic for a metal based reduction

3

reaction, thus, Red1 process is easily attributed to [CoIIPc−2]/[CoIPc−2]1- reaction (Figure 8a) [38-

4

40]. Especially the band at 470 nm is characteristic band for CoI oxidation state of the metal

5

center of CoPc complexes. Figure 8b illustrates the spectral changes observed during the

6

oxidation of CoPc at 0.75 V. The shifting of the Q band toward the longer wavelengths is a

7

characteristic spectral change for the formation of CoIII oxidation state for the metal center of the

8

complex. Therefore, Odx1 process is easily assigned to oxidation of [CoIIPc−2] to [CoIIIPc−2]1+

9

species.

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300 400 500 600 700 800 900 1000

300 400 500 600 700 800 900 1000

Wavelength /nm

AC C

Wavelength /nm

(b)

Absorbance

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Absorbance

(a)

10 11

Fig. 8. In situ UV-Vis spectral changes of CoPc in DMSO / TBAP. a) Eapp =-0.60 V b) Eapp =

12

0.75 V.

13

In-situ UV–vis spectral changes of MnPc were also recorded in DMSO/TBAP (Figure 9). Under

14

open circuit potential MnPc represents the Q band at 750 nm and the B band at 394 nm.

15

Moreover, a small band is observed at 511 nm (Figure 9a). Especially the red shifted Q band at

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the band at 511 nm are characteristic bands for Cl-MnIIIPc species [41, 42]. During the first

2

reduction reaction, observation of a new band at 694 nm is characteristic spectral changes for the

3

reduction of [Cl1--MnIIIPc−2] to [Cl1--MnIIPc−2]1-. Spectral changes given in Figure 9b are

4

characteristic changes for the formation of MnI from reduction of MnII. Especially shifting of the

5

band at 694 nm to 681 nm and observation of new band at 435 nm are characteristic changes for

6

the formation of MnI. As shown in this figure, the isosbestic points at around 675 and 790 nm

7

change continuously. Changing of the isosbestic points during an electron transfer process

8

illustrates the formation of more than one type reduced forms. These reduced forms of the

9

complexes may be [Cl1--MnIPc−2]2- and [MnIPc−2]1-. It can be concluded that after the second

10

reduction reaction, axial Cl1- ion was released and an equilibrium between [Cl1--MnIPc−2]2- and

11

[MnIPc−2]1- are formed. It is well documented than coordination number of central metal

12

decrease when the oxidation state of this metal ion decreases [41, 42]. Thus after second metal

13

based reduction reaction, releasing of axial Cl1- ion is proposed with respect to spectral changes

14

given in Figure 9b. During the oxidation reaction, cationic forms of [Cl1--MnIIIPc−2] decompose

15

under applied potential, therefore all bands of the complex decreases in intensity (Figure 9c). As

16

shown in the chromaticity diagram (Figure 9d), distinct color changes were observed during the

17

redox reactions. The orange color of the neutral [Cl1--MnIIIPc−2] species turn to light blue, purple

18

and then deep purple during the reduction reactions respectively. Due to the decomposition of

19

the complex orange color of the complex gets colorless after oxidation reaction.

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(a)

SC

300 400 500 600 700 800 900 1000

RI PT

Absorbance

Absorbance

(b)

300 400 500 600 700 800 900 1000

Wavelength /nm

Wavelength /nm

0.8

M AN U

(c)

0.7

y

Absorbance

0.6

(d)

520 nm

560 nm

500 nm

580 nm

0.5

600 nm

0.4

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0.3

300 400 500 600 700 800 900 1000

0.2 0.1 480 nm 380 nm

0.0 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

EP

Wavelength /nm 1

700 nm

x

Fig. 9. In situ UV-Vis spectral changes of MnPc in DMSO / TBAP. a) Eapp =-0.30 V b) Eapp = -

3

1.00 V, c) Eapp = 1.20 V, d) Chromaticity diagram (each symbol represents the color of electro-

4

generated species;

5

MnIIIPc1-]1+.

6

4. Conclusion

7

A series of non-peripheral metallophthalocyanines (4-6) bearing four 3-(pyrrol-1-yl)phenoxy

8

units synthesized as photosensitizer for dye-sensitized solar cells. The effect of the thickness of

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: [Cl1--MnIIIPc2-];

:[Cl1--MnIIPc2-]1-;

: [Cl1--MnIPc2-]2-;

: [Cl1--

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the photoanode layer on the photovoltaic performance of the 4-6 based devices was also

2

investigated. For this purpose, the thickness of the photoanode was varied gradually from 4 to 10

3

µm. Preliminary photovoltaic results showed that these phthalocyanine dyes are suitable as light-

4

harvesting sensitizers in DSSC application. The photovoltaic cell consisted of Pc 6 generated the

5

highest efficiency (2.44 %) among the dyes studied. The obtained results also showed that the

6

open circuit voltage is unaffected from the thickness of the photoanode layer. Electrochemical

7

and SEC analyses are in harmony with the proposed structure of the complexes. Metallization of

8

Pc ring with redox active CoII and MnIII enhances the redox activity of the complexes.

9

Observation of multi-electron redox processes at small potentials increase usability of these

10

complexes in different electrochemical technologies. Color changes during the redox reactions

11

are required properties for the usage of the complexes in display technologies.

12

Acknowledgements

13

This work is supported by TUBİTAK (Project no: 214Z104). Atıf Koca thanks Turkish Academy

14

of Sciences (TUBA) for their support.

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diphenylphenylsulfanyl substituents efficiently inhibit aggregation in phthalocyanines and

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Özgür N, Nar I, Gül A, Hamuryudan E. A new unsymmetrical phthalocyanine with a

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EP

Zimcik P, Malkova A, Hruba L, Miletin M, Novakova V. Bulky 2,6-

Koçan H, Burat AK. Synthesis and characterization of [7-(trifluoromethyl)-quinolin-4-

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Pawlowski G, Hanack M. A Convenient Synthesis of Octasubstituted Phthalocyanines.

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Synthesis 1980; 287–288.

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dyes for efficient dye-sensitized solar cells. J. Phys. Chem. B 2003; 107: 597-606.

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based on nanocrystalline TiO2 films surface treated with Al3+ Ions: photovoltage and electron

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transport studies. J. Phys. Chem. B 2005; 109: 18483-18490.

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effect on characteristic of a dye-sensitized solar cell by using electrochemical impedance

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Hara K, Sato T, Katoh R, Furube A, Ohga Y, Shinpo A. Molecular design of coumarin

SC

Alarcón H, Boschloo G, Mendoza P, Solis JL, Hagfeldt A. Dye-sensitized solar cells

M AN U

Shin I, Seo H, Son MK, Kim JK, Prabakar K, Kim HY. Analysis of TiO2 thickness

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spectroscopy. Curr. Appl. Phys. 2010; 10: S422–S424.

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spectroelectrochemical characterization of newly synthesized manganese, cobalt, iron and

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copper phthalocyanines. Electrochim. Acta 2013; 87: 554-566.

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octakis (hydroxyethylthio)-substituted phthalocyanines. J. Porphyrins Phthalocyanines 2000;

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crown ether functionalized coumarin substituted cobalt and copper phthalocyanines. J.

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electrochemical properties of phthalocyanine–fullerene hybrids. Chem. Eur. J. 2000; 6: 3600-

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3607.

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Arıcı M, Arıcan D, Uğur AL, Erdoğmuş A, Koca A. Electrochemical and

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Özkaya A, Hamuryudan E, Bayir Z, Bekaroğlu Ö. Electrochemical properties of

AC C

Esenpınar AA, Özkaya AR, Bulut M. Synthesis and electrochemical properties of

Gouloumis A, Liu SG, Sastre Á, Vázquez P, Echegoyen L, Torres T. Synthesis and

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Agboola B, Ozoemena KI, Nyokong T. Synthesis and electrochemical characterisation

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of benzylmercapto and dodecylmercapto tetra substituted cobalt, iron, and zinc

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phthalocyanines complexes. Electrochim. Acta 2006; 51: 4379-4387.

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thiophene-appended cobalt, manganese and zinc phthalocyanine complexes. Electrochim.

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Acta 2005; 50: 5427-5434.

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situ spectroelectrochemistry of partly halogenated coumarin phthalonitrile and corresponding

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metal-free, cobalt and zinc phthalocyanines. Polyhedron 2009; 28: 3788-3796.

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Obirai J, Nyokong T. Synthesis, electrochemical and electrocatalytic behaviour of

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Alemdar A, Özkaya AR, Bulut M. Synthesis, spectroscopy, electrochemistry and in

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Macrocyclic Metal Complexes. Springer; 2016, pp. 135-200.

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spectroelectrochemistry of mononuclear and binuclear cobalt phthalocyanines. Inorg. Chem.

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phthalocyanine in nonaqueous media. Chinese J. Anal. Chem. 1999; 27: 1026-1028.

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spectroelectrochemistry of a novel manganese phthalocyanine substituted with hexynyl

19

groups. Inorg. Chem. Commun. 2011; 14: 330-332.

21

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Nevin WA, Hempstead MR, Liu W, Leznoff CC, Lever A. Electrochemistry and

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Liu Y, Lin XQ. Electrochemistry and spectroelectrochemistry study of manganese

Quinton D, Antunes E, Griveau S, Nyokong T, Bedioui F. Cyclic voltammetry and

AC C

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Koca A. Spectroelectrochemistry of Phthalocyanines, Electrochemistry of N4

ACCEPTED MANUSCRIPT Table 1 The effect of the thickness of the photoanode layer on photovoltaic performance of the FTO/TiO2: 6/Electrolyte/Pt/FTO device Jsc (mA cm-2)

Voc (V)

Pmax (mW)

FF

η (%)

4

3.92

0.65

1.37

0.54

1.38

5

4.35

0.66

1.49

0.52

1.49

6

4.86

0.66

1.43

0.44

1.44

7

5.43

0.66

1.66

0.46

1.67

8

7.17

0.68

2.44

0.57

2.44

9

6.74

0.67

2.36

0.50

2.36

10

6.26

0.44

2.18

SC

M AN U 0.68

TE D EP AC C

RI PT

Thickness (µm)

2.16

ACCEPTED MANUSCRIPT Table 2 Voltammetric data of the complexes. All data were given versus Ag/AgCl. a c b Redox processes E1/2 (V) ∆Ep (mV) Ip,a/Ip,c d∆E1/2 [Cl-MnIIIPc2-]/ [Cl-MnIIIPc1-]1+ 1.10 III 2II 2- 11.15 [Cl-Mn Pc ] / [Cl-Mn Pc ] -0.05 68 0.97 II 2- 1I 2- 2-0.57 75 0.90 (in DMSO) [Cl-Mn Pc ] / [Cl-Mn Pc ] I 2- 2I 3- 3[Cl-Mn Pc ] / [Cl-Mn Pc ] -1.40 72 0.86 III 2III 1- 1+ [Cl-Mn Pc ]/ [Cl-Mn Pc ] 1.07 67 0.93 Cl-MnPc III 2II 2- 11.07 [Cl-Mn Pc ] / [Cl-Mn Pc ] 0.00 69 0.93 II 2- 1I 2- 2[Cl-Mn Pc ] / [Cl-Mn Pc ] -0.94 75 0.62 (in DCM) I 2- 2I 3- 3[Cl-Mn Pc ] / [Cl-Mn Pc ] -1.37 97 0.54 III 2- 1+ III 1- 2+ [ Co Pc ] / [Co Pc ] 1.00 CoPc II 2III 2- 1+ [Co Pc ] / [Co Pc ] 0.28 (0.54) 98 0.42 0.64 II 2I 2- 1[Co Pc ] / [Co Pc ] -0.36 (-0.46) 85 0.56 (in DMSO) [CoIPc2-]1-/ [CoIPc3-]2-1.24 96 0.53 I 3- 2I 4- 3-1.87 [Co Pc ] / [Co Pc ] III 2- 1+ III 1- 2+ [ Co Pc ] / [Co Pc ] 1.04 100 0.44 CoPc II 2III 2- 1+ [Co Pc ] / [Co Pc ] 0.69 230 0.24 0.85 II 2I 2- 1-0.16 (-0.32) 120 0.79 [Co Pc ] / [Co Pc ] (in DCM) [CoIPc2-]1-/ [CoIPc3-]2-1.31 160 0.43 I 3- 2I 4- 3[Co Pc ] / [Co Pc ] a :E1/2 values (Epa+Epc)/2) were recorded at 0.100 Vs-1 scan rate. b: ∆Ep= Epa-Epc. c:Ip,a/Ip,c for

TE D

M AN U

SC

RI PT

Complexes Cl-MnPc

:Epc values of the aggregated species recorded at 0.100 Vs-1 scan rate.

AC C

e

EP

reduction ,Ip,c/Ip,a for oxidation processes. d:∆E1/2 = E1/2 (first oxidation)- E1/2 (first reduction).

ACCEPTED MANUSCRIPT Scheme and Figure Captions: Scheme 1. Synthesis of the phthalonitrile derivative (3) and the corresponding phthalocyanines 4–6. (i) K2CO3, DMF, rt. (ii) Metal salts (CoCl2, Zn(CH3COO)2, MnCl2), 2(dimethylamino)ethanol, 145 °C, 24h.

RI PT

Fig. 1. Aggregation behavior of 4-6 in THF at different concentrations: 14 × 10−6 (A), 12 × 10−6 (B), 10 × 10−6 (C), 8 × 10−6 (D), 6 × 10−6 (E), 4 × 10−6 (F), and 2 × 10−6 (G) M.

Fig. 2. J–V characteristics of the DSSC devices with the structure of FTO/TiO2 (8 µm):4-

SC

6/Electrolyte/Pt/FTO.i

Fig. 3. The effect of the thickness of the photoanode layer on the J-V characteristics of 6

M AN U

based DSSC device.

Fig. 4. (a and b) CVs of ClMnIIIPc (5.0 x10-4 mol.dm-3) recorded at various scan rates and (c and d) SWVs of ClMnIIIPc recorded at 0.100 Vs-1 scan rate on a GCE working electrode in DCM/TBAP electrolyte.

TE D

Fig. 5. (a and b) CVs of ClMnIIIPc (5.0 x10-4 mol.dm-3) recorded at various scan rates and (c and d) SWVs of ClMnIIIPc recorded at 0.100 Vs-1 scan rate on a GCE working electrode in

EP

DMSO/TBAP electrolyte.

Fig. 6. (a) CVs of CoIIPc (5.0 x10-4 mol.dm-3) recorded at various scan rates and (b) SWVs of

AC C

CoIIPc recorded at 0.100 Vs-1 scan rate on a GCE working electrode in DMSO/TBAP electrolyte.

Fig. 7. (a and b) CVs of CoIIPc (5.0 x10-4 mol.dm-3) recorded at various scan rates and (c and d) SWVs of CoIIPc recorded at 0.100 Vs-1 scan rate on a GCE working electrode in DCM/TBAP electrolyte. Fig. 8. In situ UV-Vis spectral changes of CoPc in DMSO / TBAP. a) Eapp =-0.60 V b) Eapp = 0.75 V.

ACCEPTED MANUSCRIPT Fig. 9. In situ UV-Vis spectral changes of MnPc in DMSO / TBAP. a) Eapp =-0.30 V b) Eapp = -1.00 V, c) Eapp = 1.20 V, d) Chromaticity diagram (each symbol represents the color of : [Cl1--MnIIIPc2-];

electro-generated species;

:[Cl1--MnIIPc2-]1-;

: [Cl1--MnIPc2-]2-;

AC C

EP

TE D

M AN U

SC

RI PT

[Cl1--MnIIIPc1-]1+.

:

ACCEPTED MANUSCRIPT NO 2 NC +

HO

N

NC

i

N

O

NC

RI PT

NC

3

ii

N

SC

N

O

N

N

N

M AN U

O

N

N

M N

N

N

O

N

O

N

TE D

4 5 6 M Co Zn MnCl

Scheme 1. Synthesis of the phthalonitrile derivative (3) and the corresponding phthalocyanines 4–6. (i) K2CO3, DMF, rt. (ii) Metal salts (CoCl2, Zn(CH3COO)2, MnCl2), 2-

AC C

EP

(dimethylamino)ethanol, 145 °C, 24h.

ACCEPTED MANUSCRIPT

Absorbance

1

0.6

y = 59042x R² = 0.987

4.00E-06 8.00E-06 1.20E-05 Concentration /M

A B C D E F G

1.60E-05

0.4 0.2 0

Absorbance

3.5

Absorbance

3 2.5 2

4.5 4 y = 284502x 3.5 R² = 0,9921 3 2.5 2 1.5 1 0.5 0 0.00E+00 4.00E-06 8.00E-06 1.20E-05 Concentration /M

1.5 1 0.5 0

2

700

800

400

A B C D E F G

1.60E-05

500 600 700 Wavelength / nm

TE D

300

500 600 Wavelength / nm

M AN U

4

400

SC

300

RI PT

Absorbance

0.8

0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.2 0.1 0 0.00E+00

800

900

1.6

1.8

1.4

Absorbance

1.2 1

EP

1.6

0.6 0.4

1.2

A B C D E F G

0.2 0 0.00E+00

1

4.00E-06 8.00E-06 1.20E-05 Concentration /M

1.60E-05

AC C

Absorbance

1.4

y = 97770x R² = 0,9696

0.8

0.8 0.6 0.4 0.2

0

300

400

500 600 Wavelength / nm

700

800

Fig. 1. Aggregation behavior of 4-6 in THF at different concentrations: 14 × 10−6 (A), 12 × 10−6 (B), 10 × 10−6 (C), 8 × 10−6 (D), 6 × 10−6 (E), 4 × 10−6 (F), and 2 × 10−6 (G) M.

M AN U

SC

RI PT

ACCEPTED MANUSCRIPT

Fig. 2. J–V characteristics of the DSSC devices with the structure of FTO/TiO2 (8 µm):4-

AC C

EP

TE D

6/Electrolyte/Pt/FTO.

Fig. 3. The effect of the thickness of the photoanode layer on the J-V characteristics of 6 based DSSC device.

ACCEPTED MANUSCRIPT 10

15

(a)

(b) Oxd1

10

0

Red1

-10

Red1 Red2

-20

-1

-30

25 mVs -1 50 mVs -1 100 mVs -1 250 mVs -1 500 mVs

Red3

-5

-1

25 mVs -1 50 mVs -1 100 mVs -1 250 mVs -1 500 mVs

-10 -15

-40 -2.0

-1.5

-1.0

-0.5

0.0

-0.5

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(c)

0.5

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(d)

15

15

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1.5

Oxd1

Red1

10

10

5

5

0

Red2

-15

TE D

I (µA)

0.0

E (V) vs. Ag/AgCl

E (V) vs. Ag/AgCl 20

RI PT

0

SC

I (µA)

5

-5

Red1

-10

Red3

-20

-15

-1.0

-0.5

0.0

EP

-1.5

AC C

E (V) vs. Ag/AgCl

0.5

-0.5

0.0

0.5

1.0

E (V) vs. Ag/AgCl

Fig. 4. (a and b) CVs of ClMnIIIPc (5.0 x10-4 mol.dm-3) recorded at various scan rates and (c and d) SWVs of ClMnIIIPc recorded at 0.100 Vs-1 scan rate on a GCE working electrode in DCM/TBAP electrolyte.

ACCEPTED MANUSCRIPT (b)

(a) 15

Oxd1

Red1

0

-1

25 mVs -1 50 mVs -1 100 mVs -1 250 mVs -1 500 mVs

Red3

-1

25 mVs -1 50 mVs -1 100 mVs -1 250 mVs -1 500 mVs

-15 -2.0

-1.5

-1.0

-0.5

0.0

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Red2 -15

Red1

I (µA)

I (µA)

0

0.5

-0.5

E (V) vs. Ag/AgCl

0.0

0.5

1.0

20

20

(c)

SC

E (V) vs. Ag/AgCl

(d)

Oxd1

M AN U

Red1

15

I (µA)

I (µA)

10

-10

-15

Red3

-20 -2.0

-1.5

-1.0

Red1

TE D

Red2

-0.5

0.0

1.0

-20 -0.5

0.0

0.5

1.0

E (V) vs. Ag/AgCl

EP

E (V) vs. Ag/AgCl

0.5

AC C

Fig. 5. (a and b) CVs of ClMnIIIPc (5.0 x10-4 mol.dm-3) recorded at various scan rates and (c and d) SWVs of ClMnIIIPc recorded at 0.100 Vs-1 scan rate on a GCE working electrode in DMSO/TBAP electrolyte.

ACCEPTED MANUSCRIPT 50

(a)

0 -1

Red1

-50 -2.0

Red2

-1.5

-1.0

-0.5

0.0

0.5

E (V) vs. Ag/AgCl 30

(b)

0

Red3

-15 -30 -2.0

-1.5

EP

-45 -2.5

Red2

Red1

TE D

I (µA)

15

1.0

M AN U

45

RI PT

-25

25 mVs -1 50 mVs -1 100 mVs -1 250 mVs -1 500 mVs

SC

I (µA)

25

-1.0

-0.5

0.0

1.5

Oxd1

Oxd2

0.5

1.0

1.5

AC C

E (V) vs. Ag/AgCl

Fig. 6. (a) CVs of CoIIPc (5.0 x10-4 mol.dm-3) recorded at various scan rates and (b) SWVs of CoIIPc recorded at 0.100 Vs-1 scan rate on a GCE working electrode in DMSO/TBAP electrolyte.

ACCEPTED MANUSCRIPT 45

(b)

(a)

Oxd2

15 30

Oxd1

I (µA)

Red1

-15

-1

25 mVs -1 50 mVs -1 100 mVs -1 250 mVs -1 500 mVs

-30

Red2 -45 -2.0

-1.5

-1.0

-0.5

15

0

-1

25 mVs -1 50 mVs -1 100 mVs -1 250 mVs -1 500 mVs

-15

0.0

0.0

(c)

20

(d)

15

1.5

I (µA)

5

M AN U

Red1

Oxd2

Oxd1

10

I (µA)

1.0

SC

15

Red2

0.5

E (V) vs. Ag/AgCl

E (V) vs. Ag/AgCl

0

RI PT

I (µA)

0

0

-5

-15

-10

-1.5

-1.0

-0.5

TE D

E (V) vs. Ag/AgCl

0.0

0.0

0.5

1.0

1.5

E (V) vs. Ag/AgCl

Fig. 7. (a and b) CVs of CoIIPc (5.0 x10-4 mol.dm-3) recorded at various scan rates and (c and

EP

d) SWVs of CoIIPc recorded at 0.100 Vs-1 scan rate on a GCE working electrode in

AC C

DCM/TBAP electrolyte.

ACCEPTED MANUSCRIPT

(a)

300 400 500 600 700 800 900 1000

300 400 500 600 700 800 900 1000

Wavelength /nm

SC

Wavelength /nm

RI PT

Absorbance

Absorbance

(b)

M AN U

Fig. 8. In situ UV-Vis spectral changes of CoPc in DMSO / TBAP. a) Eapp =-0.60 V b) Eapp =

AC C

EP

TE D

0.75 V.

ACCEPTED MANUSCRIPT

(a)

SC

300 400 500 600 700 800 900 1000

RI PT

Absorbance

Absorbance

(b)

300 400 500 600 700 800 900 1000

Wavelength /nm

Wavelength /nm

0.8

520 nm

M AN U

(c)

0.7

y

Absorbance

0.6

(d)

560 nm

500 nm

580 nm

0.5

600 nm

0.4

TE D

0.3

300 400 500 600 700 800 900 1000

0.2

700 nm

0.1 480 nm 380 nm

0.0 0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7

x

EP

Wavelength /nm

AC C

Fig. 9. In situ UV-Vis spectral changes of MnPc in DMSO / TBAP. a) Eapp =-0.30 V b) Eapp = -1.00 V, c) Eapp = 1.20 V, d) Chromaticity diagram (each symbol represents the color of electro-generated species; [Cl1--MnIIIPc1-]1+.

: [Cl1--MnIIIPc2-];

:[Cl1--MnIIPc2-]1-;

: [Cl1--MnIPc2-]2-;

:

ACCEPTED MANUSCRIPT Research highlights New Pcs with four pyrrol groups have been prepared. Electrochemical and spectroelectrochemical characterization of MPcs were performed.

AC C

EP

TE D

M AN U

SC

RI PT

Solar cell properties of the phthalocyanines were investigated.