Tri-nuclear phthalocyanine complexes carrying N/O donor ligands as hydrogen peroxide catalysts, and their bleaching activity measurements by an online spectrophotometric method

Article abstract of DOI:10.1080/00958972.2017.1360490

A phthalocyanine (4) with four salicylhydrazone ligating groups that are directly linked through oxygen bridges to the macrocyclic core has been synthesized by condensation of tetrakis(4-formylphenoxy)phthalocyaninato zinc(II) (3) with salicylhydrazine. Salicylhydrazine was crystallized in methanol during the synthetic procedure. The crystal structure has triclinic space group P-1 with a?=?5.8292(6) ?, b?=?7.3039(7) ?, c?=?17.9798(18) ?, α?=?84.272(8)°, β?=?89.184(8)°, γ?=?81.469(8)°, and Z?=?4. Intramolecular O–H?O and intermolecular O–H?O, N–H?N, N–H?O hydrogen bonds were determined in the crystal structure. In addition, there is a weak C–H?π interaction. Complexation on the periphery to yield tri-nuclear Zn(II)Pcs (5–7) was performed through the reaction of a Schiff base-substituted phthalocyanine (4) with MnCl₂·4H₂O, CoCl₂·6H₂O, or Ni(OAc)₂ salts. Fourier transform infrared, ¹H NMR, ¹³C NMR, UV–Vis, ICP-OES (inductively coupled plasma optical emission spectroscopy), mass spectroscopies, and elemental analyses were applied to characterize the prepared compounds. Bleach catalyst activity of the prepared phthalocyanine complexes (5–7) was examined by the degradation of morin and curcumin, respectively. The catalysts had better activity for color removing in solutions at ambient temperature than to that of tetraacetylethylenediamine (TAED).

Full text of DOI:10.1080/00958972.2017.1360490

Journal of Coordination Chemistry
ISSN: 0095-8972 (Print) 1029-0389 (Online) Journal homepage: http://www.tandfonline.com/loi/gcoo20
Tri-nuclear phthalocyanine complexes carrying N/
O donor ligands as hydrogen peroxide catalysts,
and their bleaching activity measurements by an
online spectrophotometric method
Pinar Sen, Necmi Dege & S.Zeki Yildiz
To cite this article: Pinar Sen, Necmi Dege & S.Zeki Yildiz (2017): Tri-nuclear phthalocyanine
complexes carrying N/O donor ligands as hydrogen peroxide catalysts, and their bleaching activity
measurements by an online spectrophotometric method, Journal of Coordination Chemistry, DOI:
10.1080/00958972.2017.1360490
To link to this article: http://dx.doi.org/10.1080/00958972.2017.1360490
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Date: 29 July 2017, At: 07:38

Publisher: Taylor & Francis
Journal: Journal of Coordination Chemistry
DOI: http://doi.org/10.1080/00958972.2017.1360490
Tri-nuclear phthalocyanine complexes carrying N/O donor ligands as
hydrogen peroxide catalysts, and their bleaching activity measurements by an
online spectrophotometric method
PINAR SEN†, NECMI DEGE‡ andS. ZEKI YILDIZ*†
†Sakarya University, Faculty of Arts and Sciences, Department of Chemistry, 54187, Sakarya, Turkey
‡Ondokuz Mayıs University, Faculty of Arts and Sciences, Department of Physics, 55139 Samsun, Turkey
A phthalocyanine (4) with four salicylhydrazone ligating groups that are directly linked through
oxygen bridges to the macrocyclic core has been synthesized by condensation oftetrakis(4-
formylphenoxy)phthalocyaninato zinc(II) (3)with salicylhydrazine.Salicylhydrazine was
crystallized in methanol during the synthetic procedure. The crystal structure has triclinic space
group P-1 with a = 5.8292(6) Å, b = 7.3039(7) Å, c = 17.9798(18) Å, α = 84.272(8)°, β =
89.184(8)°, γ = 81.469(8)° and Z = 4. Intramolecular O–H···O and intermolecular O–H···O, N–
H···N, N–H···O hydrogen bonds were determined in the crystal structure. In addition, there is a
weak C–H···π interaction. Complexation on the periphery to yield tri-nuclear Zn(II)Pcs (5-7)
was performed through the reaction of a Schiff base-substituted phthalocyanine (4) with
MnCl2·4H2O, CoCl2·6H2O or Ni(OAc)2 salts. Fourier transform infrared, 1H-NMR, 13C-NMR,
UV–visible, ICP-OES (inductively coupled plasma optical emission spectroscopy), mass
spectroscopies and elemental analyseswere applied to characterize the prepared compounds.
Bleach catalyst activity of the prepared phthalocyanine complexes (5-7) were examined by the
degradation of morin and curcumin,respectively. The catalysts had better activity for color
removing in solutions at ambient temperature than to that of tetraacetylethylenediamine (TAED).
Keywords: Synthesis; Metallo phthalocyanine; Schiff base metal complex; X-Ray
crystallography;Bleach catalyst
*Corresponding author. Email: szy@sakarya.edu.tr
1

1. Introduction
Phthalocyanines have become commercially and technologically important materials due to their
remarkable fetaures [1]. Their optical, electronic and structural properties enable us to use them
for applications such as material science, non-linear optics and liquid crystals [2]. Moreover,
phthalocyanines containing d-block metals of the periodic table are widely used as efficient
catalysts in the catalytic oxidations of olefins, alcohols, aromatics and some other compounds
[3, 4].
Oxidation reactions are of importance in the chemical industry. Hydrogen peroxide is the
most widely used oxidant [5]. Especially the textile industry uses hydrogen peroxide as a
bleaching agent.H2O2 bleaching is traditionally carried out under alkaline conditions (pH 10.5-
12) at close to the boiling temperature of washing solution. This process requires high energy
consumption and long reaction times and also could cause fiber damage.
Reduction of energy and water consumption in the textile industry has become important.
Thus, bleach activator systems such as tetraacetylethylenediamine(TAED) and
nonanoyloxybenzene sulfonate (NOBS) were developed and applied in many textile works and
laundry detergents [6]. These activators yield peracids in the presence of H2O2. The generated
peracids are more effective than hydrogen peroxide at lower temperature (at about 40°C) due to
being kinetically more powerful bleaching species [7].Efforts have been made to develop new
and more eco-friendly systems by replacing the activators with catalysts. This bleach process
would decrease the temperature to ambient conditions, shorten treatment period and allow low
chemical concentration [8]. Catalyst technology is also green chemistry and reduces
environmental pollution.
Coordination compounds of salen, saltren, terpyridine-type ligands and triazole
derivatives have been synthesized and tested as bleach catalysts in terms of activating hydrogen
peroxide [9]. Transition metal complexes of hydrazones including N/O donor ligands have
received considerable attention. The interest for hydrazone derivatives in coordination chemistry
arises from their ligational behavior, chelating capability, interesting electrical as well as
magnetic properties [10]. The hydrazone Schiff bases have additional donor sites such as C=O.
The additional donor sites make them more flexible and versatile. These ligands can react with
metals both as neutral or monoanionic ligands and tend to form highly stable complexes with
transition metals. Some complexes have important material properties. Hence, coordination
2

compounds of aroylhydrazone derivatives have been synthesized and used in biological,
pharmacological, clinical and analytical applications [11-13]. They have also found wide
applications as catalysts in oxidation reactions [14-16].
These results prompted us to investigate Mn(III), Co(III) and Ni(II) complexes
ofaroylhydrazones which were directly linked through oxygen bridges to a zinc-phthalocyanine
coreas a new class of bleach catalyst for laundry cleaning applications. No such complex
structures have been obtained as catalysts to date on the Pc ring and published except studies
performed by our group [17,18].We evaluated the performance of the prepared catalysts on
bleach oxidation at room temperature in the presence of morin/H2O2as hydrophilic dye and
curcumin/H2O2 as hydrophobic dye combinations by online spectrophotometric method [19]. We
observed that the change of the metal in the hydrazone complex led to different catalytic activity
for morin and curcumin oxidation. When compared to the commercial tetra-acetyl
ethylenediamine (TAED), we obtained more effective bleaching performance in solution in a
short time by applying the newly prepared bleach catalysts.
2. Experimental
2.1. Chemicals and instruments
Salicylhydrazide has been obtained by reaction of methylsalicylate and hydrazine hydrate
according to the published literature [20]. The following chemicals were obtained from Sigma-
Aldrich:methanol, ethanol, diethylether, n-pentanol, ZnCl2,MnCl2·4H2O, CoCl2·6H2O,
Ni(CH3COO)2, FeCl3·6H2O, LiCl, morin hydrate, curcumin, potassium hydroxide (KOH), acetic
acid, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), THF, chloroform, DMF, DMSO. Hydrogen
peroxide was used as industrial grade (50%). All other reagents and solvents were reagent grade
quality and obtained from commercial suppliers. All solvents were stored over molecular sieves
(4A°) after drying and purifying as described by Perrin and Armarego [21]. All reactions were
carried out in an inert atmosphere unless otherwise stated. Oxygen free inert atmosphere was
supplied by argon purging through a dual-bank vacuum-gas manifold system. Deionized water
was generated from MILLIPORE ultra-pure water supply system. Thin-layer chromatography
(TLC) was performed using silica gel 60-HF254 as an adsorbent. Melting points were determined
using a Barnstad-Electrothermal 9200 apparatus and are uncorrected. Electronic spectra were
recorded on a Shimadzu UV-2600 Pc-spectrophotometer with quartz cell of 1 cm. Infrared
3

spectra were recorded on a Perkin Elmer Spectrum two FT-IR spectrophotometer equipped with
Perkin Elmer UATR-TWO diamond ATR and corrected by applying the atr-correction function
of Perkin Elmer Spectrum software. For Maldi-TOF spectra, the experiments were carried out
using a Bruker micrOTOF (Germany) in Gebze Institute of Technology. The compounds were
ionized in the positive electro-spray ionization ion source (ESI+) of the mass spectrometer. The
elemental compositions of the samples were analyzed by an element analyzer (Flash 2000,
Thermo Scientific). Compounds 5-7 were digested using HNO3 at 170°C for 1 h. The
manganese, cobalt and nickel contents of 5-7 in the digested mixture were determined using an
external standard with a Spectro Arcos inductively coupled plasma optical emission
spectroscopy (ICP-OES) instrument (Spectro, Kleve, Germany).
2.2. Synthesis
2.2.1. 4-[4-(1,3-Dioxolan-2-yl)phenoxy]phthalonitrile (1).The preparation of 1has been
performed in two steps. 4-Nitrophthalonitrile was reacted with p-hydroxybenzaldehyde to give
the 4-(4-formylphenoxy) phthalonitrile within 96% yield. In the second step,4-(4-(1,3-dioxolan-
2-yl)phenoxy) phthalonitrile was obtained for protecting the aldehyde group with ethylene glycol
by applying our previously published literature procedure [22,23].
2.2.2. Tetrakis[4-(1,3-dioxolan-2-yl)phenoxy]phthalocyaninato zinc(II) (2).In a standard
Schlenk tube, 4-(4-(1,3-dioxolan-2-yl)phenoxy) phthalonitrile (1)(1 g, 3.42
mmol),ZnCl2(0.117 g, 0.855 mmol) and DBU (couple drops) were mixed in n-pentanol (2.5 mL).
The reaction mixture was purged at room temperature to provide inert atmosphere and heated to
140°C for 18 h. After cooling to room temperature, the reaction mixture was precipitated by
adding 30 mL methanol/water mixture(1/1, v/v). The precipitate was collected by centrifugation,
washed several times with ethanol and water to dissolve any organic impurity and unreacted
metal salt, and thendried in an oven at 80°C. Further purification of the phthalocyanine was
performed by size exclusion chromatography on Bio-beads gel (SX-1). For the chromatographic
purification, the crude product was put onto the column and eluted with CHCl3 and the collected
phases were concentrated on a rotary evaporator and re-precipitated with methanol. The desired
pure ZnPc (2) was obtained as a green solid. Yield:85% (0.9 g), m.p: >250 °C. FT-IR (PIKE
MIRacleTM ATR) max/cm-1: 3061 (Ar, C-H), 2956, 2881 (Aliph., C-H), 1601-1506 (Ar., C=C),
4

1468-1389 (Aliph., C-C), 1225 (Asym., Ar-O-Ar), 1076 (C-O-C), 1042 (Sym., Ar-O-Ar), 940,
742.1H-NMR (DMSO) δ (ppm): 8.73-8.60 (m, 4H, ArH), 8.24 (s, 4H, ArH), 7.74-7.62 (m, 12H,
ArH), 7.59-7.48 (m, 8H, ArH), 5.87-5,82 (m, 4H), 4.01 (d, 16H).UV–Vis (DMSO-1c10-5M):
λmax (nm) (log ε) 680 (5.04), 613 (4.33), 356 (4.67). MS (MALDI-TOF): m/z 1236 [M+1]+,
1464.69 [M+1+Matrix]+(in Supporting Information).Anal. Calc. for C68H48N8O12Zn (%): C,
66.16; H, 3.92; N, 9.08; O, 15.55. Found (%):C, 65.87; H, 4.02; N, 8.92.
2.2.3. Tetrakis(4-formylphenoxy)phthalocyaninato zinc(II) (3).The cleavage reaction of
2(800 mg, 0.648 mmol) was performed in acetic acid (~ 5 mL)/FeCl3 (catalytic amount) system
using THF (5 mL) to dissolve the phthalocyanine before adding cleavage reagents. The reaction
solution was stirred at room temperature for 1d. The resulting mixture was precipitated with
water and the precipitate was collected by centrifugation. The crude product was washed several
times with ethanol and water to remove organic impurity and acidic residue, respectively, and
then dried under vacuum. Further purification of the prepared phthalocyanine was performed by
size exclusion chromatography on Bio-beads gel (SX-1) using CHCl3 as the eluent. The desired
pure product 3 was yieldedas blue-green solid by precipitation with methanol after the collected
organic eluent phases were rotary evaporated to 1/3 volume. Yield: 70% (480 mg), m.p: > 250
°C. FT-IR (PIKE MIRacleTM ATR) max/cm-1: 3064-3036 (Ar., C-H), 2828-2734 (O=C-H),
1696 (C=O), 1594-1502 (Ar., C=C), 1468-1394 (Aliph., C-C), 1229 (Asym., Ar-O-Ar), 1044
(Sym., Ar-O-Ar), 943, 827, 744.1H-NMR (DMSO) δ (ppm): 10.00-9.89 (d, 4H, CHO), 8.69 (s,
4H, ArH), 8.42-8.30 (m, 4H, ArH), 8.03 (d, 8H, ArH), 7.80 (s, 4H, ArH), 7.61 (d, 8H, ArH).13C-
NMR:192.27, 192.11, 163.27, 156.82, 156.59, 152.14, 152.01, 151.86, 151.72, 151.57, 151.33,
140.09, 134.64, 132.92, 132.78, 132.45, 132.40, 132.28, 131.71, 124.69, 122.08, 119.10, 118.84,
113.37, 113.22. UV–Vis (DMSO-1×10-5M): λmax (nm) (log ε) 678 (5.24), 612 (4.52), 355 (4.86).
MS (MALDI-TOF): m/z 1057.91 [M]+, 952.68 [M-OR]+(in Supporting Information).Anal. Calc.
for C60H32N8O8Zn (%): C, 68.09; H, 3.05; N, 10.59; O, 12.09. Found (%): C, 68.60; H, 3.17; N,
9.52.
2.2.4. Tetrakis [4-(salicylhydrazone)phenoxy]phthalocyaninato zinc(II) (4).A solution of
salicylhydrazine (126 mg, 0.83 mmol) in dry THF (10 mL) was added to a solution of tetrakis(4-
formylphenoxy)phthalocyaninato zinc(II) (3)(300 mg, 0.188 mmol) in THF (10 mL) and the
5

mixture was heated to 70°C for 12h. After cooling to room temperature, the reaction mixture was
evaporated to 1/10 of the initial volume. Then the crude product was precipitated by adding
methanol, collected by filtration and washed successively with coldmethanol and ethanol to
remove unreacted starting materials. After drying in vacuo, pure product was obtained as green
solid, Yield: 87% (395 mg), m.p: > 250 °C. FT-IR (PIKE MIRacleTM ATR)max/cm-1: 3218
(N-H), 3062-2230 (O-H….N), 3033 (Ar., C-H), 1640 (-C=O), 1597 (-C=N), 1504 (Ar., C=C),
1487-1394 (C-C), 1231 (Asym., Ar-O-Ar), 1161 (C-O), 1088 (C-N), 1044 (Sym., Ar-O-Ar), 944
(N-N), 745.1H-NMR (DMSO) δ (ppm): 12.58 (d, 4H), 12.13 (s, 4H), 9.04-8.86 (m, 8H, ArH,
CH=N), 8.58 (s, 4H), 8.24 (s, 4H), 7.81 (d, 12H), 7.42 (s, 4H), 7.34 (s, 8H), 7.05 (d, 4H), 6.81 (s,
4H).13C-NMR: 165.54, 159.89, 159.64, 157.98, 151.81, 148.93, 139.92, 134.48, 133.85, 130.20,
129.19, 124.53, 121.38, 120.12, 119.58, 117.96, 116.41, 112.54, 111.95.UV–Vis (DMSO-
1×10-5 M): λmax(nm) (log ε) 680 (5.31), 614 (4.62), 332 (5.14).MS (MALDI-TOF): m/z 1594.18
[M]+(in Supporting Information).Anal. Calc. for C88H56N16O12Zn (%): C, 66.27; H, 3.54; N,
14.05; O, 12.04. Found (%): C, 66.90; H, 3.94; N, 14.08.
2.2.5. Bis[bis((salicylhydrazone)phenoxy)manganese(III)]phthalocyaninatozinc(II)
(5).Compound 4(100 mg, 0.07 mmol) and KOH (15 mg, 0.3 mmol)were added to dry DMF (10
mL). After stirring for 20 min under inert atmosphere, MnCl2·4H2O (37 mg, 0.14 mmol) was
added and the final mixture was heated at 100°C for 8 h and then allowed to cool to room
temperature under inert atmosphere. Next, LiCl (9 mg, 0.2 mmoL) was added and the suspension
was heated to 100 °C again for 1 h with air bubbling. The progress of the reaction was monitored
by TLC.The reaction mixture was cooled to room temperature and precipitated by adding
diethylether (15 mL). The precipitate was collected by centrifugation, washed several times with
ethanol, THF and water to dissolve organic impurity and unreacted metal salt, and dried in an
oven at 80 °C.Yield: 45% (49 mg), m.p: > 250 °C.FT-IR (PIKE MIRacleTM ATR) max/cm-1:
3333 (Ar., OH), 3064 (Ar., C-H), 2923, 2848 (Aliph, C-H), 1654 (-C=N-N=C-), 1594 (Ar.,
C=C), 1486-1388 (C-C), 1228 (Asym., Ar-O-Ar), 1154 (Ph., C-O), 1085 (-N=C-O-), 1043
(Sym., Ar-O-Ar), 942 (N-N), 745.UV–Vis (DMSO-1×10-5M): λmax (nm) (log ε) 678 (5.32), 613
(4.67), 499 (3.52), 352 (5.05)MS (MALDI-TOF): m/z 1725.13 [M-C14H10N2O3-
Cl+Matriks+H2O]+, 1483.12 [M-C14H10N2O3-Cl]+, 1255.17 [M-C21H15Cl2N3O5-Mn]+(in
Supporting Information).Anal. Calc. for C88H52Cl2Mn2N16O12Zn (%): C, 59.66; H, 2.96; Cl,
6

4.00; Mn, 6.20; N, 12.65; O, 10.84; Zn, 3.69. Found (%):C, 59.32; H, 2.78; N,12.28; Zn, 3.38;
Mn, 6.32 (ICP-OES).
2.2.6. Bis[bis((salicylhydrazone)phenoxy)cobalt(III)]phthalocyaninatozinc(II)
(6).Compound 4(100 mg, 0.07 mmol) and KOH (15 mg, 0.3 mmol)were added to dry DMF (10
mL). After stirring for 10 min under argon, CoCl2·4H2O (33 mg, 0.14 mmol)was added and the
final mixture was heated to 100°C for 8 h and then allowed to cool to room temperature under
inert atmosphere. Next, LiCl (9 mg, 0.2 mmoL) was added and the suspension was heated to
100°C again for 1 h with air bubbling. The progress of the reaction was monitored by TLC. The
reaction mixture was precipitated by adding diethylether (15 mL). The precipitate was collected
by centrifugation, washed several times with ethanol, THF and water to dissolve organic
impurity and unreacted metal salt, and dried in an oven at 80°C.Yield: 46% (51 mg), m.p: >
250°C. FT-IR (PIKE MIRacleTM ATR) max/cm-1: 3326 (Ar., OH), 3057 (Ar., C-H), 2924,2851
(Alif., C-H), 1655 (-C=N-N=C-), 1592 (Ar., C=C), 1485-1385 (C-C), 1228 (Asym., Ar-O-Ar),
1157 (Ph., C-O), 1087 (-N=C-O-), 1042 (Sym., Ar-O-Ar), 942 (N-N), 745. UV–Vis (DMSO-
1×10-5M): λmax (nm) (log ε) 678 (4.92), 615 (4.42), 335 (4.88). MS (MALDI-TOF): m/z 1783.43
[M]+, 1554.15 [M-C7H5NO2-CoCl2+Na+H2O]+, 1306.12 [M-C21H15Cl2CoN3O5+2Na]+ (in
Supporting Information).Anal. Calc. for C88H52Cl2Co2N16O12Zn (%): C, 59.39; H, 2.95; Cl, 3.98;
Co, 6.62; N, 12.59; O, 10.79; Zn, 3.67. Found (%): C, 59.14; H, 2.65; N, 12.38; Zn, 3.39; Co,
6.82(ICP-OES).
2.2.7. Bis[bis((salicylhydrazone)phenoxy)nickel(II)]phthalocyaninatozinc(II) (7).
Compound 4(100 mg, 0.07 mmol) and KOH (15 mg, 0.3 mmol)were added to dry DMF (10
mL). After stirring for 10 min under inert atmosphere, Ni(OAc)2 (25 mg, 0,14 mmol)was added
and the final mixture was heated to 100°C for 8 h and then allowed to cool to room temperature.
The reaction mixture was precipitated by adding diethylether (15 mL). The precipitate was
collected by centrifugation, washed several times with ethanol, THF and water to dissolve
organic impurity and metal salt, respectively. The resulting green product was dried in an oven at
80°C. Yield: 55% (52 mg), m.p: > 250°C. FT-IR (PIKE MIRacleTM ATR)max/cm-1: 3267 (Ar.,
OH), 3062 (Ar., C-H), 2927, 2873 (Aliph., C-H), 1651 (-C=N-N=C-), 1593,1531 (Ar., C=C),
1485-1373 (C-C), 1230 (Asym., Ar-O-Ar), 1161 (Ph., C-O), 1091 (-N=C-O-), 1041 (Sym., Ar-
7

O-Ar), 945 (N-N), 744.UV–Vis (DMSO-1×10-5M): λmax (nm) (log ε) 675 (4.33), 639 (4.32), 345
(4.59). MS (MALDI-TOF): m/z 1653.54 [M-C7H5NO2+2Na+2H2O]+, 1617.56 [M-
C7H5NO2+2Na]+, 1595.62 [M-C7H5NO2+Na]+, 1463.09 [M-C14H10N2O4-Ni+3Na+H2O]+ (in
Supporting Information). Anal. Calc. for C88H52Ni2N16O12Zn (%): C, 61.87; H, 3.07; Ni, 6.87; N,
13.12; O, 11.24; Zn, 3.83. Found (%): C, 61.14; H, 2.85; N, 12.98; Zn, 3.22; Ni, 6.24 (ICP-OES).
2.3. X-ray crystal structure determination
A suitable single crystalwithdimensions 0.44 × 0.28 × 0.13 mmwas chosen for the
crystallographic study and then carefully mounted on a goniometer of a STOE IPDS II
diffractometer. Data collection of C7H8N2O2 was performed with a STOE IPDS II single crystal
X-ray diffractometer using graphite monochromated Mo Kα radiation ( = 0.71073 Å) at room
temperature (296 K). Details of the data collection conditions and parameters of refinement are
given in table 1. Cell parameters were obtained by using X-AREA [24] and data reduction was
achieved with X-RED32 [24] software.The maximum peaks and deepest hole observed in the
final Δρ map were 0.29 and −0.19 e Å-3, respectively. The scattering factors were taken from
SHELXL-97 [25]. The molecular graphics were done using ORTEP-3 for Windows [26]. All
non-hydrogen atoms were refined anisotropically. All hydrogens bonded to carbons were
positioned geometrically and refined as a riding model with C–H = 0.93 Å and Uiso(H) =
1.2Ueq(C), while the hydrogen bonded to the N was located in a difference Fourier map and
refined isotropically [N–H = 0.84(4) Å].The coordinates of the hydrogens of the hydroxyl group
were determined from a difference Fourier map and refined isotropically subject to a restraint of
O–H = 0.82(4) Å.The general-purpose crystallographic tool PLATON [27] was used for
structure analysis.WinGX [28] was used to prepare the data for publication. Details of the data
collection conditions and the parameters of refinement are given in table 1.CCDC 1473714
contains supplementary crystallographic data (excluding structure factors). These data can be
obtained free of charge via http://www.ccdc.cam.ac.uk/deposit [or from the Cambridge
Crystallographic Data Center (CCDC), 12 Union Road, Cambridge CB2 1EZ, UK; Fax:
+44(0)1223 336033; E-mail:deposit@ccdc.cam.ac.uk].
8

2.4. Catalytic bleaching
Bleaching process was performed by using an online specrophotometric method to monitor the
oxidation of Morin and curcumin dyes [19]. The method used in this study enables in situ
following the spectral changes and the determination of the amount of dye bleaching as a
percentage. Experiments were carried out in an amber-colored reaction vessel placed on a
magnetic stirrer with addition of the required amount of carbonate buffer solution (pH 10.5), 80
mM morin/curcumin, 10 μM catalyst and 10 mM hydrogen peroxide. The temperature of
solutions was maintained at 25 C with a programmable water bath. A peristaltic pump was used
to transfer the solution mixture from the reaction vessel to the flow cell placed in the sample
compartment of the UV–Vis spectrophotometer. The initial absorbance of morin and curcumin in
buffer solution was measured. Bleaching of morin and curcumin was followed as the decrease in
absorbances at 411 and 467 nm, respectively. The bleaching reaction was initiated by adding
H2O2 into the reaction mixture together with the catalyst. The continuous circulation of the
mixture was provided between the reaction vessel and UV–Vis spectrophotometer by the
peristaltic pump. The scanning-kinetic measurement program of the software was run for 5 min
intervals monitoring the spectral changes through 45 min. The determined bleaching percentage
and absorbance changes from the measurements were graphed as a function of time. The amount
of decolorization of morin and curcumin was expressed as the dye bleaching percentage and
calculated by Eq. (1) [19]:
퐴0 ‒ 퐴푡
(1)
% 퐃퐲퐞 퐁퐥퐞퐚퐜퐡퐢퐧퐠 =
퐱 ퟏퟎퟎ
퐴0
where A0 and At are the absorbance of morin and curcumin at time 0 and time t, respectively.
3. Results and discussion
3.1. Synthesis and spectroscopic characterization
Scheme 1 shows the synthetic route for the target phthalocyanines 2-7.
Cyclotetramerization of the phthalonitrile derivative 1 to the peripherally tetra-acetal
group substituted zinc(II) phthalocyanine 2 was accomplished in n-pentanol in the presence of
anhydrous ZnCl2and DBU. The purification of 2 was performed by size exclusion
9

chromatography on Bio-beads gel (SX-1) by eluting with chloroform. The synthesis of the
aldehyde substituted phthalocyanine 3 was achieved by applying acetal de-protection method to
ZnPc 2in acetic acid/FeCl3protection system. This cleavage reaction was conducted at room
temperature by dissolving of the corresponding phthalocyanine (2) in THF before adding de-
protection agents. The preparation of salicylhydrazone substituted ZnPc 4as Schiff base
derivative was performed in THF at reflux by using ZnPc 3 and salicylhydrazine. The
complexation of the salicylhydrazone groups on the periphery positions of phthalocyanine 4 to
give trinuclear-Pcs was carried out with MnCl2·4H2O for 5, CoCl2·6H2O for 6 and
Ni(CH3COO)2 for 7 in DMF under basic conditions as shown in scheme 1. After complexation,
LiCl was added to the reaction mixtures individually to complete the manganese and cobalt
coordinations with Cl- following oxidation of Mn(II) and Co(II) to Mn(III) and Co(III).
Characterization of the products was carried out by FT-IR, 1H-NMR, 13C-NMR, melting
point, UV/Vis, ICP-OES, mass spectroscopy and elemental analysis. All the spectral data are in
accord with the proposed structures.
In the FT-IR spectrum, formation of acetal substituted ZnPc 2 starting from the
corresponding phthalonitrile 1 derivative was confirmed by disappearance of the -C≡N stretch at
2235 cm-1. The typical aliphatic –C-H vibrational bands at 2956 and 2888 cm-1 assigned to C-H
stretches of acetyl groups confirmed the formation of 2. The sharp peak at 1696 cm−1 in the FT-
IR spectrum of 3from the -C=O stretchof the aldehyde groups is indicative for the cleavage
reaction.The peaks at 2828-2734 cm-1, which are attributed as Fermi resonance, prove aldehyde
formation at Pc 3, as well. The formation of Schiff base substituted ZnPc 4 was confirmed by
disappearance of the formyl groups belonging to ZnPc 3 and appearance of -C=N stretch at 1597
cm-1. The hydrazones synthesized in this work may exist in keto or enol tautomeric forms in the
solid state. The presence of the -C=O stretch at 1640 cm-1 suggests that the ligand is in the keto
form in the solid state [29].The N-H vibration of amide nitrogen at 3218 cm-1 and the typical O-
H…O vibrations as a large distorted band at 3062-2230 cm-1 confirm that hydrogen bonding
occurred between the C=O and the phenolic -OH groups of the salicylhydrazone moieties as
shown in figure 1 [30].
FT-IR spectra of the metal complex-substituted phthalocyanines (5-7) showed that the
-C=O and N-H bands disappeared when compared to the free ligand (4). New bands at 1654 cm-1
for 5, 1655 cm-1 for 6and 1651 cm-1for 7are due to –C=N-N=C- stretching. This indicates that
10

the keto oxygens in the hydrazone groups enolize and deprotonate during complexation by the
base. This is also further confirmation for the coordination of the ligands through the azomethine
nitrogen and enolate oxygen [17].
The 1H-NMR data gave information about the proposed structures of 2-4.In the 1H-NMR
spectrum of 2, aromatic protons were at 8.92-7.48 ppm. The aliphatic protons of -OCH2CH2O-
bridge of acetal groups are 4.01 ppm as a doublet and the protons bonded to tertiary carbon at
5.87-5.82 ppm as multiplet which confirms that the phthalocyanine 2 consists of a mixture of
isomers.
In the 1H-NMR spectrum of 3, the presence of aldehyde protons at 10.00 ppm and 9.89
ppm as two different singlets and the absence of the -OCH2CH2O- peaks indicates the conversion
of acetal protection to the aldehyde; aromatic protons were at 8.69-7.61 ppm. In the 1H-NMR
spectrum of 4, the shift of aldehyde protons to 9.04-8.86 ppm as azomethine protons indicates
the Schiff base formation. NH and OH protons arising from the salicylhydrazone group were
also observed at 12.13ppm and 12.58 ppm, respectively.
No satisfactory 13C-NMR spectrum was obtained for 2 due to a resolution problem. In the
13C-NMR spectrum of 3, aldehyde carbons were observed at 192.27 and 192.11ppm and
aromatic carbons were observed at 163.27-113.22 ppm. In the 13C-NMR spectrum of 4, C=O and
CH=N group carbons belonging to the salicylhydrazone group determined at 165.54 ppm and
159.89 ppm, respectively, confirmed the imine formation and supported the proposed structure.
1H-NMR and 13C-NMR spectra of manganese(III), cobalt(III) and nickel(II)
salicylhydrazone complex substituted phthalocyanines (5-7) were not obtained due to solubility
problems and paramagnetism.
Phthalocyanines show typical electronic spectra with two absorption regions,one in the
UV region at about 300-350 nm (B-band) and the other in the visible area at 600-700 nm (Q-
band). The Q-band is attributed to π-π* transition from the highest occupied molecular orbital
(HOMO) to the lowest unoccupied molecular orbital (LUMO) of the Pc ring. The B-band arises
from the deeper π levels to the LUMO [31].
The comparative electronic absorption spectra of the target products were examined in
DMSO due to good solubility.
The UV-Vis spectra of 2-6 showed intense Q-absorption bands at 680, 678, 680, 678, 678
nm and B bands at 356, 355, 332, 352, 335 nm, respectively. The UV-Vis spectra of 2-6 showed
11

no splitting on the Q-bands which indicated that they were metallophthalocyanines with D4h
symmetry as expected (figure 2) [32].
Phthalocyanine compounds form aggregates (dimer and high order oligomers) in solution
due to π-π stacking, hydrogen bonding, donor-acceptor interactions and axial ligand–metal
coordinations [33]. High aggregation tendency of phthalocyanine compounds often cause low
solubility in many solvents. It also affects their spectroscopic properties, dramatically. This is
easily observed by the value of the Q-bands shifting to higher energy and broadening [34]. The
spectral data for 5-7 showed that the Q-band absorption was affected by the nature of metal
ionscoordinated to the substituents. Difference in metal ions lead to aggregation causing a
decrease in the molar absorption coefficient [35]. Also, an apparent difference between the Q-
band absorption of nickel-complex substituted ZnPc (7) and 2-6 is seen from rather broad
absorbances in the higher energy side of the spectrum. This might be because of the higher
planarity of the molecule and lower tendency of the solvents to axial coordination [36]. DMSO is
a strong coordinating solvent with a high donor number that is able to coordinate to most metals
through either the sulfur or the oxygen, and it normally prevents aggregation as seen in UV-Vis
spectra of 2-6 [37]. However, this is not the case in this work for 7. Another potential mode of
interaction is through axial coordination of salicylhydrazone unit to the Ni(II) center of the
complex. As a result of the propensity of Ni(II) to form octahedral complexes with metal–ligand
interaction, there was self-assembly at 10−5 M concentration in the spectrum of 7(figure 2) [38].
The mass spectra of 2-7were recorded by the MALDI-TOF mass spectrometer for
confirming the proposed structure. Mainly molecular ion and matrix (Dithranol) adduct peaks of
2 were observed at m/z: 1236 [M+1]+ and 1464.69 [M+Matrix]+. For 3and4, Dithranol (DIT) was
also used as matrix and molecular ion peaks were observed and easily identified asm/z: 1057.91
[M]+ and 1594.18 [M]+, respectively. In the mass spectrum of 5 obtained using DIT as matrix,
one of the fragment ion peaks was observed at m/z: 1725.13 [M-C14H10N2O3-
Cl+Matriks+H2O]+.For the cobalt-complex substituted ZnPc (6) α-cyano-4-hydroxycinnamic
acid (CHCA) was used as matrix and molecular ion peak was observed at m/z: 1783.43 [M]+;
2,5-dihydroxybenzoic acid (DHB) was used as matrix for 7and the observed peak at m/z 1463is
the base peak of spectrum and belongs to a fragment ion. For the metal complex substituted Pcs
(5-7), other fragment ion peaks in the spectra were determined, tabulated and given in
Supporting Information.
12

The elemental analysis results for the synthesized phthalocyanines (2-7) were consistent
with the calculated values given in the Experimental section.
ICP-OES measurements were done for the determination of the quantities of Mn(III),
Co(III) and Ni(II) ions included in Pc structures 5-7. The theoretical percentage by weight of
manganese content in 5 is 6.20, cobalt in 6 is 6.62 and nickel in 7 is 6.87. From the experiments,
the percentages by weight of Mn(III), Co(III) and Ni(II) were obtained as 6.32, 6.82 and 6.24,
respectively. Thus, the ICP-OES measurements provide additional support to the proposed
structures of 5-7.
3.2. Description of the crystal structure
The ORTEP diagram of 2-hydroxybenzohydrazide, C7H8N2O2, with thermal ellipsoids drawn at
a 50% probability is shown in figure1.The geometric parameters and hydrogen bonding are given
in tables 2 and 3, respectively. Figure1 shows the atom-numbering scheme and 50% probability
displacement ellipsoids of non-hydrogen atoms and two intramolecular (O–H···O) hydrogen
bonds. The asymmetric unit of‘C7H8N2O2’contains phenyl rings, hydroxide and acetohydrazide
groups (figure 1).
The dihedral angles between phenyl rings for each molecule are 72.22(12)°for ring 1
(C2-C7)/ring 2 (C9-C14). The aromatic C–C distances for 2-hydroxybenzohydrazide are
1.367(6) to 1.427(5) Å. The maximum deviation of the phenyl ring1 and phenyl ring2 from
planarity is 0.008(3) Å for C5 and 0.012(4) Å for C11,respectively. The rings are planar. The
aromatic C–C distances for phenyl ring1 and phenyl ring2 are 1.366(6) to 1.413(5) Å and
1.353(7) to 1.394(6) Å, respectively. The C1–O1 [1.254(4) Å] bond has double bond character,
while the C3–O2 [1.356(5) Å] bond has single bond character (table 2). Observed bond lengths
are in agreement with previously reported values by Zhang [39], Kargar [40] and Mikenda et al.
[41].
The crystal packing of 1 is stabilized by two intramolecular [(O2–
H15···O1),(O4H4B···O3)] hydrogen bonds and four intermolecular [(N2–H2···N1),(N1–
H1A···O2), (N4H4C···N3), (N3–H3B···O3)] hydrogen bonds with geometric parameters
1.79(3) Å, 2.517(5) Å, 146(5)° and 1.80(3) Å, 2.551(5) Å, 149° and 2.21(4) Å, 2.957(5) Å, 146°
and 2.38(3) Å, 3.166(6) Å, 156(4)° and 2.25(3) Å, 2.983(6) Å, 144(5)°,2.31(4) Å, 3.034(5) Å,
143(5)°, respectively (table 3 and figure 3).The molecules are further linked through other
13

NH···O hydrogen bonds forming undulating two-dimensional networks parallel to the bc plane.
These networks are finally linked via an NH···O hydrogen bond to form a three-dimensional
structure (figure3). In addition, there is a weak intermolecular CH···π interaction. The basic
intermolecular association patterns consist of closed six-membered hydrogen bonded dimers
which are connected via NH···NH2 hydrogen bonds.
3.3. Bleach performance
Bleaching agentsare active in many cleaning products, including standard domestic powder
detergents for laundry. The main functions of a bleach system are to provide whiter
clothes,removing stains such as tea, coffee, red wine or fruit from fabric types. Oxygen-based
bleaching agents involve hydrogen peroxide. Bleach systems work through oxidation reactions
of hydrogen peroxide as powerful oxidizing agents witha chromophore group causing colorful
substrates to degrade into colorless or water-soluble products.
In Europe peroxide-based bleach systems contain bleach activators such as TAED and
NOBS for decreasing the washing temperatures [42]. A major and continuing trend in washing
conditions in Europe is the lowering of wash temperatures to gain energy saving and avoid the
deformation of fabrics.
We have developed new bleach catalysts which could replace the activators. We
performed comparative bleaching experiments with these catalysts in the hydrogen peroxide
system with the known commercial activators. The procedure of bleaching experiments was
derived from literature as described previously for phthalocyanine complexes [17,43].
The experiments were carried out at constant temperature (25°C) with 10 µM catalyst,
80 µM morin/curcumin and 10 mM H2O2 in 10 mM buffer solution (100 mL) by using deionized
water at pH 10.5 to provide basic detergent conditions.
Morin, a polyphenolic chromophore belonging to flavonoids, and curcumin as an oil-
based food stain model marker were chosen as hydrophilic and hydrophobic dyes, respectively.
Their bleachings were examined in solution. The applied bleach process condition is presented in
figure 4. The proposed colorless water-soluble degradation products for morin dye are
2,4-dihydroxybenzoic acid and 2,4,6-trihydroxybenzoic acid as seen in our recent study [17].
Curcumin is hydrolyzed to feruloyl methane and ferulic acid at the pH of washing solutions [44].
14

The mechanism of the bleaching is based on the activation of hydrogen peroxide to
-
produce perhydroxyl anion (HO2 ). Because of alkali medium, H+ is neutralized and then rapid
-
complex formation with metal ions of the complex substituents occurs with the produced HO2 . It
is known that the nature of metal ions has significant influence on the catalytic activities. We
carried out studies with Zn(II) as the central metal and Mn(III), Co(III) and Ni(II) ions as the
coordinating metals to the substituents.The catalytic reactions on the complex substituents
Mn(III)Cl (5), Co(III)Cl (6) and Ni(II) (7) of ZnPc complexes carry out by coordination of the
active oxidative intermediate (OOH-) (Eq.2), generated from H2O2, to the metal ion of the
substituents to form M-OOH peroxo complex in a similar way to porphyrin-Fe(III) complexes as
illustrated in Eq.3 [45].
OH-
H2O2
M + OOH-
H+ + OOH-
H2O + OOH-(2)
M – OOH + dyeoxidized dye(3)
The effect of oxidant (H2O2) with commercial TAED, tri-nucleating Pc compounds (5-7)
and without using catalyst or activator on bleach performance are shown by the decrease in
absorbance of morin dye at 411 nm and curcumin dye at 467 nm, as shown in figure5 and
figure 6. The absorbance of the morin or curcumin dye in buffer solution decreased by addition
of hydrogen peroxide/catalyst combination with increase of reaction time. These changes in
absorption monitoring in UV-Vis spectroscopy indicate the oxidative degradation of
morin/curcumin.
As shown in figures5 and 6, the absorptions at 411 nm for morin and 467 nm for
curcumin in the visible region exhibit a rapid decrease and nearly disappear by 45 min for 5and
6. For Ni(II) complex substituted ZnPc (7), the Ni(II) ion has also tendency to form higher
agregate species,causing decreasing solubilityand is therefore less active than the other
complexes [15]. The decolorization of curcumin occurs more quicklythan morin for all the
prepared catalysts due to destruction of the long conjugated π systems [46].
The bleaching activity of the prepared phthalocyanine complexes was examined, and the
catalyst activities were determined in terms of decoloration percentage of dye and bleaching
15

speed. Mn(III) as environmentally friendly, Co(III) as the most active and Ni(II) have been
chosen as active metal centers, and all measurements were performed comparatively. When the
UV-Vis spectral changes of morin/curcumin at bleach experiments were evaluated, the
Co(III)Cl-complex substituted Pc (6) wasthe most efficient oxidative catalyst as a function of
total bleaching percentage with 93.13% for morin and 93.11% for curcumin. From the obtained
results the order of the catalyst activity was Co(III) complex > Mn(III) complex > Ni(II)
complex as the function of the total bleaching percentage for both curcumin and morin.
The performances of the prepared catalysts were also characterized by bleaching speed.
In Co(III)Cl-complex substituted Pc(6), bleaching of morin and curcumin were completed after
adding hydrogen peroxide/catalyst combinationat 15 min and 45 min, respectively; the Co(III)
complex catalyzed substrate was the fastest bleaching.
Mn(III) complexes could exist as µ-oxo dimer forms under basic conditions which is
indispensable for laundry applications. These Mn(III) species, which reduce the catalytic
activities, have to cleavage before formation of the active form of the catalysts [47].
The lowest activity was observed on Ni(II)-complex substituted Pc (7). Differences in
catalytic ability have also been attributed to the relative capacity of the metal complexes to form
octahedral complex binding perhydroxyl anion (HOO-) reversibly [48]. Selected results were
plotted as percentage of bleaching and change in absorbance versus time (figure7).
The results related with the percentages of decolorations and the completion time of the
bleaching are tabulated in table 4.
The activity of H2O2 alone as oxidant and TAED used in detergent formulations as bleach
activator were also tested. No apparent absorbance change was observed upon addition of
H2O2to morin solution and little change observed upon addition to curcumin solution. The
obtained bleaching results of 5-7 were compared with commercial TAED used for bleach
activator in detergent formulations. The catalysts had more bleaching efficiency, even though
200 fold TAED was used. The results of the activity of the catalysts, TAED and H2O2 are shown
comparativelyin figure 8.
4. Conclusion
On-line spectrophotometric system is very useful for in situ monitoring of spectral changes
during oxidation reactions between catalyst/oxidant combinations and dye. This method was
16

applied on decolorization of morin and curcumin from aqueous solution. This study describes
new salicylhydrazone metal complex substituted phthalocyanine derivatives as bleach catalysts
for laundry applications. We have investigated the catalytic activity of the prepared complexes
activating hydrogen peroxide.The results showed that the prepared phthalocyanine catalysts have
very high bleach activity. Adding a very small amount of a suitable catalyst resulted in
significantly improved bleaching effect.
Coordination of the metals to the Schiff base unit of Pc ligand (4) led to differences in
catalytic activity. The salicylhydrazone cobalt-complex substituted Pc (6) has fairly high bleach
percentage and degradation speed.The generation of perhydroxyl adducted (M–OOH)
intermediate via the central transition metal ions influences the rate of reaction and bleach
percentage.
When compared to the commercial TAED or H2O2 alone, we obtained more effective
bleaching in a short time by applying the prepared complexes as bleach catalysts. The order of
the catalytic activity was determined as Co(III) complex (6) > Mn(III) complex (5) > Ni(II)
complex (7) > TAED > H2O2 as a function of bleaching percentage. Taking into account the high
bleachingactivity of Pc-Schiff base complexes, the prepared functionalmolecules could be
possible bleach catalysts for laundry detergentapplications.
Acknowledgement
This work was supported by Ministry of Science, Industry and Technology of Turkey (SANTEZ
project no. 0182.STZ.2013-1) and Research Fund of Sakarya University (project no. 2014-02-04
007 and2015-50-02-036). We also thank Prof. M.S. Dundar and Celal Caner from analytical
research laboratory for their assistance related with the ICP-OS analysis.
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19

Table 1. Crystallographic data and refinement parameters for C7H8N2O2.
Crystal data
Chemical formula
Mr
C7H8N2O2
152.15
Crystal system, space group
Temperature (K)
a, b, c (Å)
Triclinic, P-1
296
5.8292(6), 7.3039(7), 17.9798(18)
α, β, γ (°)
84.272(8), 89.184(8), 81.469(8)
V (Å3)
753.26(13)
Z
4
Radiation type
µ (mm−1)
Mo Kα
0.10
Crystal size (mm)
0.44 × 0.28 × 0.13
Data collection
Diffractometer
Absorption correction
Tmin, Tmax
STOE IPDS 2 diffractometer
Integration
0.962, 0.988
No. of measured, independent
7131, 3152, 1586
andobserved [I> 2σ(I)] reflections
Rint
0.053
0.630
(sin θ/λ)max (Å−1)
Refinement
R[F2 > 2σ(F2)], wR(F2), S
0.070, 0.281, 1.15
H-atom treatment
H atoms treated by a mixture of
independent and constrained refinement
Δρmax, Δρmin (e Å-3)
0.29, −0.19
20

Table 2. Selected bond lengths (Å) and angles (°) forC7H8N2O2.
Bond lengths (Å)
O1—C1
O2—C3
C1—N2
C1—C2
N2—N1
1.254(4)
1.356(5)
1.325(5)
1.474(6)
1.404(5)
O3—C8
C8—N4
C8—C9
O4—C14
N4—N3
1.248(5)
1.316(5)
1.495(6)
1.360(5)
1.413(5)
Bond angles (°)
O1—C1—C2
N2—C1—C2
C7—C2—C3
C1—N2—N1
120.7(4)
119.0(3)
117.3(4)
122.2(3)
O3—C8—N4
O3—C8—C9
N4—C8—C9
120.2(4)
120.9(4)
118.8(4)
Torsion angles (°)
O1—C1—C2—C7
N2—C1—C2—C7
O1—C1—C2—C3
N2—C1—C2—C3
O1—C1—N2—N1
C2—C1—N2—N1
O3—C8—C9—C14
−176.6(4)
3.8(6)
5.1(5)
−174.5(4)
2.8(6)
−177.6(4)
5.8(6)
N4—C8—C9—C14
O3—C8—C9—C10
N4—C8—C9—C10
O3—C8—N4—N3
C9—C8—N4—N3
C10—C9—C14—O4
C8—C9—C14—O4
−175.3(4)
−175.2(4)
3.6(6)
−0.6(7)
−179.5(4)
−179.2(4)
−0.2(7)
21

Table 3. Hydrogen-bond geometries (Å, °) forC7H8N2O2.
D—H···A
D—H
H···A
D···A
D—H···A
O2—H15···O1
N2—H2···N1i
N1—H1A···O2ii
O4—H4B···O3
N4—H4C···N3iii
N3—H3B···O3iv
C4—H4···Cgv
0.828(19)
0.85(2)
1.79(3)
2.21(4)
2.38(3)
1.80(3)
2.25(3)
2.31(4)
2.78
2.517(5)
2.957(5)
3.166(6)
2.551(5)
2.983(6)
3.034(5)
3.571(5)
146(5)
146(6)
156(4)
149(4)
144(5)
143(5)
143
0.843(19)
0.833(19)
0.855(19)
0.85(2)
0.93
Symmetry codes: (i) −x+1, −y, −z; (ii) −x, −y+1, −z; (iii) −x+2, −y+1, −z+1;
(iv) −x+2, −y, −z+1; (v) 1+x, y, z
22

Table 4. The results of decoloration of morin and curcumin under homogeneous conditions.
Morin
Curcumin
The
The
completion
time of the
bleaching
(min)
completion
time of the
bleaching
(min)
Catalyst
Bleach %
(45 min)
Bleach %
(45 min)
5
25
15
-
82.36
93.13
24.45
4.94
-
88.12
93.11
81.85
47.64
83.32
6
45
-
7
H2O2
-
-
TAED=Catx200
-
72.82
-
23

Graphical abstract
OH
OH
OH
OCH3
OH
N
N
HO
HO
N
N
O
O
O
HO
H3CO
O
N
N
N
N
N
Zn
N
N
M
M
BLEACHED
N
HO
O
OH
O
N
O
O
O
HO
M: Mn(III)Cl
Co(III)Cl
Ni(II)
N
N
N
OH
OH
OH OH
H2O2
+
color stains
Colorless degradation products
24

O
O
O
O
O
O
O
O
O
O
O
O
N
Zn
N
N
Zn
N
O
NC
NC
N
N
N
N
N
N
N
N
ii
i
N
N
N
N
1
O
O
O
O
3
O
O
2
O
O
O
O
iii
HO
O
N
N
O
NH
OH
N
O
M
OH
O
X
N
N
O
N
O
HN
O
N
N
N
Zn
N
N
HO
N
N
O
M
iv
O
N
N
N
N
Zn
N
N
N
N
N
N
X
OH
NH
N
O
O
O
O
HO
O
N
4
O
N
N
N
HN
OH
OH
5-M: Mn(III), X: Cl
6-M: Co(III), X:Cl
7-M: Ni(II), X:-
O
Scheme 1. Synthesis route: (i) n-pentanol, ZnCl2, DBU. (ii) THF, acetic acid, FeCl3·6H2O. (iii)
salicylhydrazide, THF, reflux (iv) DMF, KOH, MnCl2·4H2O for 5, CoCl2·6H2O for 6, Ni(OAc)2
for 7.
25

Figure1. ORTEP plot of C7H8N2O2. The molecular structure shows the atom-numbering scheme
and 50% probability displacement ellipsoids of non-hydrogen atoms. The intramolecular
hydrogen bond is shown as a dashed line.
26

Figure 2. Absorption spectra of 2-7 in DMSO(concentration 1×10−5 mol.L−1).
27

.
Figure 3.Crystal-packing diagram of C7H8N2O2along the b axis. Hydrogen bonds are shown as
dashed lines.
28

MeO
HO
HO
OH
O
O
HO
O
or
OH
HO
OH
O
MeO
Curcumin
Morin
10 mM Buffer Solution
80 µM Dye,
10 mM H2O2,
25 oC,
pH:10.5
10 µM Catalyst
Degredation products
Figure 4. Conditions for bleaching of morin and curcumin.
29