Synthesis characterization and antibacterial activity of Cr (III), Co (III), Fe (II), Cu (II), Ni (III) complexes of 4-(2-(((2-hydroxy-5-nitrophenyl) diazenyl) (phenyl) methylene) hydrazinyl) benzene sulfonic acid based formazan dyes and their applications on leather

Article abstract of DOI:10.1016/j.dyepig.2017.08.058

A novel series of un-metallized and metal complexes formazan dye (12–17) have been synthesized in an aqueous system, without using Buffers, with cost-effectiveness and improved fastness properties. The synthetic methodology involved the synthesis of 4-(2-(((2-hydroxy-5-nitrophenyl) diazenyl) (phenyl) methylene) hydrazinyl) benzene sulfonic acid followed by diazotization of 4-nitroamisnophenol which further coupled with coupler reagent i.e. 4-[(2Z)-2-benzylidenehydrazinyl] benzene sulfonic acid. Multichromic metal complexes of 4-(2-(((2-hydroxy-5-nitrophenyl) diazenyl) (phenyl) methylene) hydrazinyl) benzene sulfonic acid (1:1 and 2:1) were synthesized with the salts of Chromium, Iron, Cobalt, Copper and Nickel. Newly synthesized metal complexes were characterized by Ultraviolet–visible (UV–Vis), Fourier transforms infrared (FT-IR), Proton nuclear magnetic resonance (¹H NMR), C¹³-nuclear magnetic resonance (¹³C NMR), powder X-ray crystallography (XRD) and elemental analysis. Their performance as colorant material for different fastness properties like light fastness, wash fastness, perspiration fastness were evaluated on leather fabric and were shown to possess good fastness properties 3–5, 4–5, 3–5, and 4–5 respectively. The synthesized formazan dyes were also demonstrated the high percentage value of exhaustion and fixation on leather ranging from 91–97% and 90–98% respectively. The synthesized un-metallized and metal complex formazan dyes were ranged in color from Blue, violet, Green, Brown to Red. Antibacterial activity of synthesized formazan dyes was determined in solution by agar well diffusion method and on leather using the dyed leather fabric with synthesized dyes as model system. Maximum antibacterial activity in solution with ZOIs (19 ± 0.05 mm, 25 ± 0.07 mm, 23 ± 0.09 mm, 27 ± 0.03 mm) and significant % reduction in bacterial growth on leather (56 ± 0.03%, 65 ± 0.07%, 70 ± 0.05%, and 72 ± 0.08%) was demonstrated by chromium complex (15) against E. coli, S. aureus, Klebsiella and B. subtilis respectively.

Full text of DOI:10.1016/j.dyepig.2017.08.058

Accepted Manuscript
Synthesis characterization and antibacterial activity of Cr (III), Co (III), Fe (II), Cu (II),
Ni (III) complexes of 4-(2-(((2-hydroxy-5-nitrophenyl) diazenyl) (phenyl) methylene)
hydrazinyl) benzene sulfonic acid based formazan dyes and their applications on
leather
Shakeel Ahmad Khan, Sammia Shahid, Sadia Kanwal, Ghulam Husaain
PII:
S0143-7208(17)31116-6
10.1016/j.dyepig.2017.08.058
DYPI 6220
DOI:
Reference:
To appear in: Dyes and Pigments
Received Date: 13 May 2017
Revised Date: 15 August 2017
Accepted Date: 25 August 2017
Please cite this article as: Khan SA, Shahid S, Kanwal S, Husaain G, Synthesis characterization
and antibacterial activity of Cr (III), Co (III), Fe (II), Cu (II), Ni (III) complexes of 4-(2-(((2-hydroxy-5-
nitrophenyl) diazenyl) (phenyl) methylene) hydrazinyl) benzene sulfonic acid based formazan dyes and
their applications on leather, Dyes and Pigments (2017), doi: 10.1016/j.dyepig.2017.08.058.
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ACCEPTED MANUSCRIPT
Synthesis Characterization and Antibacterial Activity of Cr (III), Co (III), Fe (II), Cu (II),
Ni (III) Complexes of 4-(2-(((2-hydroxy-5-nitrophenyl) diazenyl) (phenyl) methylene)
hydrazinyl) benzene sulfonic acid based Formazan Dyes and their Applications on Leather
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Shakeel Ahmad Khan *, Sammia Shahid , Sadia Kanwal , Ghulam Husaain
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Department of Chemistry, School of Science, University of Management & Technology,
Lahore-54770, Pakistan
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Department of Biochemistry, University of Agriculture, Faisalabad-38000, Pakistan
Institute of Chemistry, University of Punjab, Lahore-54000, Pakistan
*
For correspondence: Email: Shakilahmad56@gmail.com; Tel: +92-3441865064
Graphical Abstract:
Keywords: Aromatic amine; hydrazine; formazan complexes; fastness properties; leather
application; antibacterial activity

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Synthesis Characterization and Antibacterial Activity of Cr (III), Co (III), Fe (II), Cu (II),
Ni (III) Complexes of 4-(2-(((2-hydroxy-5-nitrophenyl) diazenyl) (phenyl) methylene)
hydrazinyl) benzene sulfonic acid based Formazan Dyes and their Applications on Leather
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Shakeel Ahmad Khan *, Sammia Shahid , Sadia Kanwal , Ghulam Husaain
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Department of Chemistry, School of Science, University of Management & Technology,
Lahore-54770, Pakistan
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Department of Biochemistry, University of Agriculture, Faisalabad-38000, Pakistan
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Institute of Chemistry, University of Punjab, Lahore-54000, Pakistan
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For correspondence: Email: Shakilahmad56@gmail.com; Tel: +92-3441865064
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Abstract: A novel series of un-metallized and metal complexes formazan dye (12-17) have been
synthesized in an aqueous system, without using Buffers, with cost-effectiveness and improved
fastness properties. The synthetict methodology involved the synthesis of 4-(2-(((2-hydroxy-5-
nitrophenyl) diazenyl) (phenyl) methylene) hydrazinyl) benzene sulfonic acid followed by
diazotization of 4-nitroamisnophenol which further coupled with coupler reagent i.e. 4-[(2Z)-2-
benzylidenehydrazinyl] benzene sulfonic acid. Multichromic metal complexes of 4-(2-(((2-
hydroxy-5-nitrophenyl) diazenyl) (phenyl) methylene) hydrazinyl) benzene sulfonic acid (1:1
and 2:1) were synthesized with the salts of Chromium, Iron, Cobalt, Copper and Nickel. Newly
synthesized metal complexes were characterized by Ultraviolet-visible (UV-Vis), Fourier
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transforms infrared (FT-IR), Proton nuclear magnetic resonance ( H-NMR), C -nuclear
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magnetic resonance ( C-NMR), powder X-ray crystallography (XRD) and elemental analysis.
Their performance as colorant material for different fastness properties like light fastness, wash
fastness, perspiration fastness were evaluated on leather fabric and were shown to possess good
fastness properties 3-5, 4-5, 3-5, and 4-5 respectively. The synthesized formazan dyes were also
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demonstrated the high percentage value of exhaustion and fixation on leather ranging from 91-
97% and 90-98% respectively. The synthesized un-metallized and metal complex formazan dyes
were ranged in color from Blue, violet, Green, Brown to Red. Antibacterial activity of
synthesized formazan dyes was determined in solution by agar well diffusion method and on
leather using the dyed leather fabric with synthesized dyes as model system. Maximum
antibacterial activity in solution with ZOIs (19±0.05 mm, 25±0.07 mm, 23±0.09 mm, 27±0.03
mm) and significant % reduction in bacterial growth on leather (56±0.03%, 65±0.07%,
70±0.05%, and 72±0.08%) was demonstrated by chromium complex (15) against E. coli, S.
aureus, Klebsiella and B. subtilis respectively.
Keywords: Formazan dyes; diazotization; coupling reaction; metal complex; fastness;
antibacterial activity
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1. Introduction
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Formazan dyes bear a formal resemblance to azo dyes, since they contain an azo group, but have
sufficient structural dissimilarities to be considered as a separate class [1]. Formazan/tetrazolium
and their derived metal complexes are colored compounds. They impart color due to π-π*
transitions of π electrons in formazan skeleton. Formazan Skeleton is (-N=N–C=N–NH-) [2].
Formazans are polydentate ligands with donor atoms so that’s why they have the ability to form
complexes with metal atoms. Metal complex formazan is derived from non-metal complex
formazan by treating it with metal salts such as FeSO .7H O, CrCl .6H O, and CuSO .5H O, etc.
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Formazans and their metal complex are ranging in color from red to orange as well as blue color.
Their color depending upon the structure either which type of chromospheres and auxochromes
are attached to color imparting molecule [3]. Metal complexes of tetradentate formazan were
first employed as dyes for the dyeing of wool by Ciba in 1947 [4]. Since then many metal
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complexes of tetradentate formazans have been reported and they have become an important dye
type, especially in the areas of reactive and acid dyes although other applications have also been
reported [5,6]. In addition to studies on their end-uses, investigations have been made with
respect to synthetic methods, as well as on the relationships between applications, colors
properties and chemical constitutions of the dyes [4]. Numerous literature associated to
formazans dyes are available. That literature shows their synthesis, structural properties,
photochromic transitions, tautomer formation, redox potentials [7,8] as well as the synthesis of
crown formazans are discussed [9,10]. Thermogravimetric analyses, dissociation and stability
constants, formation constants and electrochemical behaviors of Metal–complexes formazan
were evaluated [11,12]. Formazan/tetrazolium used in Brucella ring test in milk for the
recognition of the presence of Brucella species. Brucellosis is a bacterial infection that spreads
from animals to people most often via unpasteurized milk, cheese, and other dairy products [13].
Blue tetrazolium/formazan systems are used to exhibit enzymes activity in normal and neoplastic
tissues. But it was found that it has 10 times more noxious effects in vivo (mice) than mono
tetrazolium/formazan system itself [14]. Formazan/tetrazolium system is relatively useful in the
determination of the effect of anti-cancer drugs [15,16]. However, Kebler and Furusaki states
that tetrazolium cannot act to do so every time, since the age of the cell and medium, both are
also important and take into matter. Formazan dyes have become important reactive dyes for
cotton. Formazan dyes are also castoff in analytical chemistry due to their high color strength of
numerous of their derived metal complexes [17]. As a result of their fast and intense color
reaction, formazans can be used for the spectroscopic determination of a variety of metal ions
[18]. The aims of this research work were involved too (i) synthesize formazan dyes and their
metal complex, (ii) Characterization of formazan and their metal complex dyes, (iii)
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Performance evaluation of formazan and their metal complex dyes on leather with respect to
their color imparting properties.
2. Experimental Work
This research work was accompanied in the research laboratory of Department of Chemistry,
University of Management and Technology, Lahore Pakistan and in Research and Development
Lab in Shafi Reso-Chem, Lahore Pakistan. All chemicals employed in this research work were
procured from Fluka Chemische (Switzerland) as well as from BASF (Germany).
2.1 Physical measurement
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Infrared spectra’s were obtained in the range of 450-4000 cm by using Agilent Cary 630,
Agilent Technologies, USA, FTIR spectrophotometer. Electronic absorption spectra’s of
compound (Dye 12-17) were obtained in water in the range of 200-800 nm by using UV-visible
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spectrophotometer = Spectra Flash SF 550, Data color Inc., USA. H -NMR spectra’s were
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recorded in a CDCl solvent by using NMR Bruker DPX 400-Operating at 300/75- C MHz
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spectrophotometer. Powder X-ray diff raction analysis was performed by PANalytical X’Pert
diffractometer PRO instrument with Cu–Kα radiation (wavelength 0.154 nm) operating at 40 kV
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and 30 mA. Measurements were scanned for diff raction angles (2θ) ranging from 20 to 90 with
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a step size of 0.02 and a time per step of 1 s. The elemental analysis of the compounds (C, H, N,
S) was carried out using Flash EA 1112 elemental analyzer. Melting Points were recorded using
Melting Point apparatus, Gallenkamp, UK. pH of the reaction and compounds was monitored
with Portable pH Meter Model PHB4. Application of dyes was done on leather by using Leather
Dying Drum Machine = Jiangsu Lianyungang Leather Machinery Factory China, Model# R-350-
6. Light Fastness properties were evaluated by using Xenon Fad-o-meter Model# XF-15N,
Shimudzu Corporation Kyoto Japan. In this study, the progress of the entire reactions was
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supervised by TLC, which was performed on 2 × 5 cm aluminum sheets preloaded with silica gel
60F254 to a thickness of 0.25 mm (Merck). The chromatograms were visualized under
ultraviolet light (254-366 nm) or iodine vapors.
2.3 General procedure for the synthesis of 4-[(2Z)-2-benzylidenehydrazinyl] benzene
sulfonic acid (5)
Synthesis of 4-[(2Z)-2-benzylidenehydrazinyl] benzene sulfonic acid which act as coupler
reagent, comprises of the conversion of 4-aminobenzenesulphonic acid (1) to diazonium salt (2)
which on reduction yielded 4-hydrazinylbenzenesulfonic acid (3) which further react with
benzaldehyde to form required product [19].
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Scheme 1: Synthesis of 4-[(2Z)-2-benzylidenehydrazinyl] benzene sulfonic acid (5)
2.3.1 Diazotization of 4-[(2Z)-2-benzylidenehydrazinyl]
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Technical grade 4-aminobenzenesulphonic acid (1) corresponding to 173g (1mole) of 100 per
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cent purity added in 1500 ml water in 3 L beaker and also added 65 g of Na CO then given a
mixing for complete dissolution. Then the solution is filtered off to remove undissolved particles
and impurities. Then the made ice jacketed around the beaker to attain temperature 0-5°C. Then
during continuous agitation, the addition of 400 ml of HCl was made gradually. Then the ice
flakes about 100 g added to the solution to maintain temperature 0-5°C, and the addition of
Sodium nitrite solution i.e. 73 g of NaNO in 150 ml water was done dropwise in 15 minutes at
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temperature 0-5°C. Then the congo-iodo paper was checked which was positive by giving blue
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coloration. Then the reaction mixture allowed for 1:30 hr for reaction completion. Afterward,
diazonium salt filtered off with filtration unit associated with vacuum pump [20]. Scheme 1
showed the synthesis of diazonium salt (2) of 4-aminobenzenesulphonic acid (1).
2.3.2 Reduction of diazonium salt (2) of 4-aminobenzenesulphonic acid (1)
To a beaker of 3 L, 565 g of crystalline Na SO .7H O had been added in 830 ml water and made
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a clear solution of it. Solution of Sodium sulfite cooled in an ice bath to attain 0-5°C
temperature. At that temperature moist paste of diazonium salt (2) added in one hour. Then the
orange coloration appears in solution without turbidity. Then the stirring made continuously for 1
hour. Afterwards, the reaction solution was heated to boil-age with continuous stirring and 664
concentrated HCl was added in half an hour. The solution color lightens and finally very light
yellow color appeared at the end of reaction. Reaction mixture cooled down over a period of
overnight. Precipitate formation takes place and these are filtered off with sanction unit, washing
of precipitates was done with cold water. Precipitates of 4-hydrazinylbenzenesulfonic acid (3)
dried in an electric oven at 100°C. Purification was done by employing the method as described
by [19]. % age yield= 96% of the theoretical amount. Scheme 1 was represented the synthesis of
4-hydrazinylbenzenesulfonic acid (3).
2.3.3 Synthesis of 4-[(2Z)-2-benzylidenehydrazinyl] benzene sulfonic acid (5)
To a beaker of 3 L, quantity 198.75 g (1mole) of 4-hydrazinylbenzenesulfonic acid (3) weighed
on analytical balance by considering it 95% pure and dissolved it by the addition of 2508 ml of
water as well as 99.99 ml of NaOH added to attain pH~10, heated with continuous stirring for 30
minute at 45°C. Afterwards, cool down and filter it to remove impure and undissolved materials.
Solution was shifted in 3 liter reactor and heated to 55-60°C. Condensation reaction was done by
the drop-wise addition of benzaldehyde (4) 106.2 g (1mole) in 30 minute at 55°C with
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continuous stirring. Stirring plus heating continue till complete reaction. Reaction completed in 3
hour. Then the precipitation achieved by acidification as well as salting out process at pH~2.5 at
room temperature which is done by employing the 25 ml HCl and 20% of NaCl of the total
volume of the solution. After, filtration was done through filtration unit at ambient temperature.
Filtered cake was dried in electric oven at 60°C. % age yield was 97% of the theoretical amount.
4-[(2Z)-2-benzylidenehydrazinyl] benzene sulfonic acid (5) was that coupler reagent which was
employed for the synthesis of formazan dyes by the azo coupling reaction. This product (5) was
purified by following the method as described by [20,21]. Scheme 1 exhibited the synthesis of 4-
[(2Z)-2-benzylidenehydrazinyl] benzene sulfonic acid (5).
2.4 General Procedure for the Synthesis of formazan dyes (12-17)
In this research work, first 4-[(2Z)-2-benzylidenehydrazinyl] benzene sulfonic acid (5) were
synthesized (Scheme 1) which act as coupler reagent. In second step, 4-(2-(((2-hydroxy-5-
nitrophenyl) diazenyl) (phenyl) methylene) hydrazinyl) benzene sulfonic acid (12) were
synthesized which was un-metallized formazan dye. Further un-metallized formazan dye (12)
was converted to metal complexes with the salts of Fe, Cu, Cr, Ni and Co and their
characterization was done by using different spectroscopic techniques. The syntheses of each
formazan dye of this series were given in the scheme 2.
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Scheme 2: Synthesis of un-metallized formazan dyes (12), metal complexes of Fe (13), Cu (14),
Cr (15), Ni (16) and Co (17)
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2.4.1 Synthesis of 4-(2-(((2-hydroxy-5-nitrophenyl) diazenyl) (phenyl) methylene)
hydrazinyl) benzene sulfonic acid (12)
To a 500 ml beaker, 150 ml water added along with 15.41g (0.1mole) on 100% pure basis of 4-
nitroaminophenol (10) on continuous stirring with multiple agitators. Then 40 ml of HCl was
added allowed for 15 minutes for complete dissolution. After that solution is filtered off by
employing suction unit to remove impurity. Then the solution beaker jacketed with ice and 30 g
of ice flakes was also added to attain the temperature 10ºC. Afterward, a solution of NaNO2
/water (7.4/l5ml) added in 4 portions. Positivity of Congo red paper for HCl and Iodo paper for
NaNO checked. Then the reaction solution was stirred for 1hr at 15-17 ºC. Congo-iodo= +ve
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the addition of 5g of Sulfamic acid (H NSO ). Again purification of diazo (11) was done by the
filtration process. Diazonium salt (11) is ready for the further process. This diazonium salt of 4-
nitroaminophenol (11) was coupled with 28.48g (0.1mole) on 97% percent pure basis of 276.31g
of 4-[(2Z)-2-benzylidenehydrazinyl] benzene sulfonic acid (5) that was achieved by dissolving
(5) in 400 ml H O at highly alkaline pH~10-11 at temperature 15-17 ºC. Alkaline pH was
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achieved by the addition of 35g of Na CO . The addition of diazonium salt (11) to coupler
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reagent (5) was done in 1hour. The reaction took 2 hours for its completion. The dye (12) was
brought to room temperature; pH was reduced up to 4.5 by HCl and 15% NaCl of the total
volume of dye was also added for salting out purposes. The dye (12) was filtered and dried at 60-
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70 C till constant weight. The obtained yield was 85% over theoretical calculation. The reaction
for the synthesis of formazan dye 12 is presented in scheme 2.
2.4.2 Synthesis of [4-(2-(((2-hydroxy-5-nitrophenyl) diazenyl) (phenyl) methylene)
hydrazinyl) benzene sulfonic acid] iron II complex (1:1) (13)
For the synthesis of dye (13), un-metallized formazan dye [4-(2-(((2-hydroxy-5-nitrophenyl)
diazenyl) (phenyl) methylene) hydrazinyl) benzene sulfonic acid] (12) of 0.1 mole was prepared
according to the method as described in scheme 2. Dye (12) was acting as tridentate ligand. Its
metallization with iron was achieved by treating it with equimolar (0.1mole) concentration i.e.
27.80g of FeSO .7H O at slightly acidic pH~6.50 at elevated temperature i.e. 65-70ºC. Slightly
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acidic pH achieved with the addition of HCl in dye (12) then heated it for 65-70ºC. At required
temperature, addition of FeSO .7H O was done in 30 minute. Afterwards, reaction mixture was
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heated for 3 hour for the completion of metallization and final product was dye 13 i.e. [4-(2-(((2-
hydroxy-5-nitrophenyl) diazenyl) (phenyl) methylene) hydrazinyl) benzene sulfonic acid] iron II
complex (1:1). The dye (13) was brought to room temperature; pH was reduced up to 4.5 by HCl
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and 15% NaCl of total volume of dye was also added for salting out purposes. The dye (13) was
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filtered and dried at 60-70 C till constant weight. The obtained yield was 90% over theoretical
calculation. The reaction for the synthesis of formazan dye (13) is presented in scheme 2.
2.4.3 Synthesis of [4-(2-(((2-hydroxy-5-nitrophenyl) diazenyl) (phenyl) methylene)
hydrazinyl) benzene sulfonic acid] copper II complex (1:1) (14)
For the synthesis of dye (14), un-metallized formazan dye [4-(2-(((2-hydroxy-5-nitrophenyl)
diazenyl) (phenyl) methylene) hydrazinyl) benzene sulfonic acid] (12) of 0.1 mole was prepared
according to the method as described in scheme 2. Dye (12) was acting as tridentate ligand. Its
metallization with copper was achieved by treating it with equimolar (0.1mole) concentration i.e.
24.9685g of CuSO .5H O at slightly acidic pH~6.50 at elevated temperature i.e. 65-70ºC.
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Slightly acidic pH achieved with the addition of HCl in dye (12) then heated it for 65-70ºC. At
required temperature, addition of CuSO .5H O was done in 30 minute. Afterwards, reaction
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mixture was heated for 3 hour for the completion of metallization and final product was dye 14
i.e. [4-(2-(((2-hydroxy-5-nitrophenyl) diazenyl) (phenyl) methylene) hydrazinyl) benzene
sulfonic acid] copper II complex (1:1). The dye (14) was brought to room temperature; pH was
reduced up to 4.5 by HCl and 15% NaCl of total volume of dye was also added for salting out
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purposes. The dye (14) was filtered and dried at 60-70 C till constant weight. The obtained yield
was 89% over theoretical calculation. The reaction for the synthesis of formazan dye 14 is
presented in scheme 2.
2.4.4 Synthesis of Bis-[4-(2-(((2-hydroxy-5-nitrophenyl) diazenyl) (phenyl) methylene)
hydrazinyl) benzene sulfonic acid] chromium III complex (2:1) (15)
For the synthesis of dye (15), un-metallized formazan dye [4-(2-(((2-hydroxy-5-nitrophenyl)
diazenyl) (phenyl) methylene) hydrazinyl) benzene sulfonic acid] (12) of 0.1 mole was prepared
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according to the method as described in scheme 2. Dye (12) was acting as tridentate ligand. Its
metallization with chromium as 2:1 complex was achieved by treating it with 0.05 mole
concentration i.e. 13.32 g of 26.64 g of CrCl .6H O at slightly acidic pH~6.70 at elevated
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temperature i.e. 90-100ºC. Slightly acidic pH achieved with the addition of HCl in dye (12) then
heated it for 90-100ºC. At required temperature, addition of CrCl .6H O was done in 30 minute.
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Afterwards, reaction mixture was heated for 5 hour for the completion of metallization and final
product was dye 15 i.e. Bis-[4-(2-(((2-hydroxy-5-nitrophenyl) diazenyl) (phenyl) methylene)
hydrazinyl) benzene sulfonic acid] chromium III complex (2:1). The dye (15) was brought to
room temperature; pH was reduced up to 1.5 by HCl and 20% NaCl of total volume of dye was
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weight. The obtained yield was 91% over theoretical calculation. The reaction for the synthesis
of formazan dye (15) is presented in scheme 2.
2.4.5 Synthesis of [4-(2-(((2-hydroxy-5-nitrophenyl) diazenyl) (phenyl) methylene)
hydrazinyl) benzene sulfonic acid] nickel II complex (1:1) (16)
For the synthesis of dye (16), un-metallized formazan dye [4-(2-(((2-hydroxy-5-nitrophenyl)
diazenyl) (phenyl) methylene) hydrazinyl) benzene sulfonic acid] (12) of 0.1 mole was prepared
according to the method as described in scheme 2. Dye (12) was acting as tridentate ligand. Its
metallization with copper was achieved by treating it with equimolar (0.1mole) concentration i.e.
28.086g of NiSO .7H O at slightly acidic pH~6.50 at elevated temperature (65-70ºC). Slightly
4
2
acidic pH achieved with the addition of HCl in dye (12) then heated it for 65-70ºC. At required
temperature, addition of NiSO .7H O was done in 30 minute. Afterwards, reaction mixture was
4
2
heated for 3 hour for the completion of metallization and final product was dye (16) i.e. [4-(2-
(((2-hydroxy-5-nitrophenyl) diazenyl) (phenyl) methylene) hydrazinyl) benzene sulfonic acid]
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nickel II complex (1:1). The dye (16) was brought to room temperature; pH was reduced up to
3.5 by HCl and 15% NaCl of total volume of dye was also added for salting out purposes. The
o
dye (16) was filtered and dried at 60-70 C till constant weight. The obtained yield was 87% over
theoretical calculation. The reaction for the synthesis of formazan dye (16) is presented in
scheme 2.
2.4.6 Synthesis of [4-(2-(((2-hydroxy-5-nitrophenyl) diazenyl) (phenyl) methylene)
hydrazinyl) benzene sulfonic acid] cobalt III complex (1:1) (17)
For the synthesis of dye (17), un-metallized formazan dye [4-(2-(((2-hydroxy-5-nitrophenyl)
diazenyl) (phenyl) methylene) hydrazinyl) benzene sulfonic acid] (12) of 0.1 mole was prepared
according to the method as described in scheme 2. Dye (12) was acting as tridentate ligand. Its
metallization with copper was achieved by treating it with equimolar (0.1mole) concentration i.e.
24.91g of (CH COO.4H O) at slightly acidic pH~6.50 at elevated temperature i.e. 65-70ºC.
3
2
Slightly acidic pH achieved with the addition of HCl in dye (12) then heated it for 65-70ºC. At
required temperature, addition of NiSO .7H O was done in 30 minute. Afterwards, reaction
4
2
mixture was heated for 3 hour for the completion of metallization and final product was dye (17)
i.e. [4-(2-(((2-hydroxy-5-nitrophenyl) diazenyl) (phenyl) methylene) hydrazinyl) benzene
sulfonic acid] cobalt III complex (1:1). The dye (17) was brought to room temperature; pH was
reduced up to 2.5 by HCl and 15% NaCl of total volume of dye was also added for salting out
o
purposes. The dye (17) was filtered and dried at 60-70 C till constant weight. The obtained yield
was 88% over theoretical calculation. The reaction for the synthesis of formazan dye (17) is
presented in scheme 2.
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2.5 Dyeing method for assessment of color shade development on leather
Assessment of color shade development of un-metallized formazan dye (12) and metal complex
formazan dyes (13-17) was done by the application of dyes at 2% dyeing on goat leather fabric
by using the standard method as described by [21,22]. Dye solution (250 ml, 1.0 g dye equivalent
to 2% of goat crust weight) was taken in a dyeing drum. The pH of the dye-bath was adjusted to
5.5 by adding acetic acid solution (5.0 ml. 10% w/v) solution. The total volume of the dye-bath
was adjusted to 500 ml by adding the required amount of water. The leather pieces of 50 g of
goat crust were introduced into the dye-bath with continuous stirring at 24 rpm. The contents of
º
the dye-bath were stirred for 1 hour at room temperature (30 C) and then the temperature was
º
gradually raised to 50-55 C over a period of 35 minutes and maintained for 1 hour. The dye-bath
was kept rotating during the process of dyeing; formic acid 5.0 ml was added and pH adjusted to
3.6 and run the drum for half hour more till dye fixed on leather. After this, the dye liquor was
taken in 500 ml volumetric flask. The fabric was washed with cold water and the combined
solution of dye liquor and washings was then further diluted to 500 ml with water. From this
diluted solution, 2.0 ml was further diluted to 100 ml with water and the absorbance of this
solution was measured to find out the exhaustion of dye on leather sheet. The dyed leather piece
was piled up overnight to dry; provided the chukrum and toggle and finally, mounted on shade
card. A weighed amount of leather piece was stirred in boiling acidified pyridine which dissolves
the unfixed dye from fabric and from the absorbance of this solution percentage fixation was
determined.
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2.6 Valuation of fastness properties on leather
Valuation of fastness properties like color change, staining on adjacent fiber, light, wash and
perspiration for the synthesized un-metallized formazan dyes and metal complex formazan dyes
series (12-17) was checked by the application of 2% dye on Goat leather as per standard methods
described by [23].
2.7 Antibacterial activity
The antibacterial activity of each type of synthesized formazan dyes (12-17) was examined in
solution [24] as well as on substrate against different bacterial strains i.e. Staphylococcus aureus
(ATCC 25923), Bacillus subtilis (ATCC 9637), Klebsiella (ATCC 10031) and Escherichia coli
(ATCC 25922). The antibacterial effect of synthesized formazan dyes (12-17) on agar plates was
studied by known agar well diffusion method as described by [25,26]. These bacterial strains
were obtained from Pakistan Chemical Scientific Industrial Research (PCSIR) laboratories
complex, Lahore, Pakistan. Cefradine was used as a standard antibiotic drug (positive control)
for each type of bacterial species.
2.7.1 Antibacterial activity of synthesized formazan dyes (12-17) in solution
In the first step, sample solutions with 1M strength of each type of synthesized formazan dyes
(12-17) and standard drug were prepared with distilled water separately in 1L volumetric flask
[27]. In the second step, solution of nutrient agar was prepared in 1L volumetric flask by
dissolving 28 g nutrient agar in 1000 mL distilled water with continuous stirring to dissolve well
and to make the solution uniform; then mouth of flask was covered with yarn to preserve the
culture media. Then sterilized it in an autoclave at 120-121 °C and maintains pressure at 15 LD/
sq inch for 20-25 min and then cooled that solution. This medium used for the growth of the
bacterial strains for the preparation of inoculum [28].
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In the third step, slants of each frozen bacteria that were already present in the stock slants of
bacterial culture were taken and a loop full of culture or frozen bacteria was added to the
sterilized nutrient agar in the test tube and preserved for future use. After that, bacterial strains
(S. aureus, B. subtilis, Klebsiella and E. coli) from stock slants were taken and added into four
conical flasks in which nutrient agar (25 ml) was already added. These four cultures of four
different bacteria were incubated at 37 °C for 24 hours in a shaker. These cultures used as
inoculum [29].
In the fourth step, freshly prepared molten nutrient agar (200 mL) was poured in 28 sterilized
petri dishes as a basal layer. After that 1 mL inoculum of each bacterial strain (S. aureus, B.
subtilis, Klebsiella and E. coli) was added in 28 petri dishes. Then put lids on the dishes and
allowed them to cool and solidify. The solidify agar core 2 mm in diameter was bored at three
peripheral positions by sterilized hollow iron rod. After that holes were filled with the already
prepared samples and standard drug. Then the petri dishes were allowed to place for 1 hour and
after that incubated the dishes in incubator at 37 °C for 24 hours in order to complete the reaction
for bioactivity. After the completion of incubation period the diameters of the clear zones were
measured and recorded [30].
2.7.2 Antibacterial activity of synthesized formazan dyes (12-17) on substrate (Leather
fiber)
In the next set of experiments, the antibacterial activity of leather specimens dyed with
synthesized formazan dyes (12-17) and standard drug (Cefradine) was determined and leather
fabric was dyed as per following the methods described in the dyeing method section. The 1
2
inch each fabric specimens (dyed and standard) were introduced separately in the 200 mL
nutrient agar inoculated with the different bacterial strains i.e. S. aureus, B. subtilis, Klebsiella
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and E. coli and incubated at 37 °C overnight (16 h). The same set of experiment was also
repeated for the undyed leather fabric as done with dyed leather fabric [31]. The % reduction of
bacterial growth by synthesized formazan dyes (12-17) and standard drug (Cefradine) was
expressed as follows:
R= B-A/A×l00
where R= % reduction in bacterial population; B= absorbance (660 nm) of the media inoculated
with bacterial strains and undyed fabric; A= absorbance (660 nm) of the media inoculated with
bacterial strains and dyed fabric.
3
35 3. Results and Discussion
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45
In current research work, un-metallized formazan dyes (12) and metal complex formazan dyes
(13-17) were synthesized by employing different metal salts of Fe, Cu, Co, Ni, and Cr.
Synthesized formazan dyes had been characterized by UV-visible spectroscopy, IR spectroscopy,
1
13
H-NMR, C-NMR, powder XRD as well as by elemental analysis. Performance evaluation of
these dyes was checked on leather by employing leather processing drums.
3.1 Spectral Studies
3.1.1. 4-(2-(((2-hydroxy-5-nitrophenyl) diazenyl) (phenyl) methylene) hydrazinyl) benzene
sulfonic acid (12).
Reddish Brown (Solid). Yield (85%). Melting Point (390ºC). λmax in nm (log
ε
): λmax1 470
-1
υ
(0.470), λmax2 340 (0.687). FTIR (KBr, Cm ) max: 1500 (C=N, str), 1358 (N=N, str), 1600
3
46
(aromatic C
=
3
C), 750 (CN=NC, str), 3410 (N-H, str), 1130 (Ar-OH, str), 1420 (SO H, str), 1335
1
3
3
3
47
48
49
(Ar-NO2, str). H-NMR (CDCl
3
, 400 MHz)
H), 6.50-7.60 (m 12H, Ar-H). C-NMR (CDCl
109.8, 117.6, 125.4, 126.3, 127.3, 128.8, 131, 134.7, 139.2, 140.5, 146.8, 164.1 (Aromatic
δ: 5.35, (s 1H, Aromatic-OH), 1.14, (s 1H, N-H),
13
11.28 (s 1H, SO
3
3
, 75 MHz) δ: 155 (C=N), 102,
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15 5 6
carbons). Anal. Calc. for C19H N O S (MW: 441.417 g/mol): C, 51.7; H, 3.43; O, 21.75; N,
15.87; S, 7.26% and Found: C, 51.3; H, 3.3; O, 21.55; N, 15.65; S, 7.21%.
3.1.2. [4-(2-(((2-hydroxy-5-nitrophenyl) diazenyl) (phenyl) methylene) hydrazinyl) benzene
sulfonic acid] iron II complex (1:1) (13).
Reddish Brown (Solid). Yield (90%). Melting Point (450ºC). λmax in nm (log
ε
): λmax1 380
(0.950), λmax2 280 (1.05). FTIR (KBr, Cm ) max: 1540 (C=N, str), 1440 (N=N, str), 1580
(aromatic C C), 830 (CN=NC, str), 1385 (SO H, str), 1360 (Ar-NO str), 680 (Metal-O, str),
3410 (O-H, str). H-NMR (CDCl , 400 MHz)
-1
υ
3
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=
3
2,
1
3
3
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δ: 11.10 (s 1H, SO H), 6.70-8.20 (m 12H, Ar-H).
3
3
1
3
C-NMR (CDCl , 75 MHz) δ: 155.2 (C=N), 111.5, 116.5, 117.6, 125.4, 127.3, 127.7, 128.8,
3
131.0, 134.7, 137.0, 139.2, 149.3, 150.5, 159.5, (Aromatic carbons). Anal. Calc. for
C H FeN O S (MW: 549.292 g/mol): C, 41.54; H, 3.49, O, 26.21; N, 12.75; S, 5.84; Fe,
19
19
5
9
10.17%. Found: C, 41.30; H, 3.35; O, 26.15; N, 12.6; S, 5.56; Fe, 10.05%.
3.1.3. [4-(2-(((2-hydroxy-5-nitrophenyl) diazenyl) (phenyl) methylene) hydrazinyl) benzene
sulfonic acid] copper II complex (1:1) (14).
Greyish Black (Solid), Yield (89%), Melting Point (420ºC). λmax in nm (log ε λmax1 340 (0.758),
):
λmax2 218 (0.90). FTIR (KBr, Cm ) max: 1499 (C=N, str), 1305 (N=N, str), 1595 (aromatic
C=C), 840 (CN=NC, str), 1290 (SO H, str), 1395 (Ar-NO str), 610 (Metal-O, str), 3490 (O-H,
-1
υ
3
66
3
2,
1
13
3
3
3
3
3
67
68
69
70
71
str). H-NMR (CDCl , 400 MHz) δ: 11.20 (s 1H, SO H), 6.85-8.55 (m 12H, Ar-H). C-NMR
3 3
(CDCl , 75 MHz)
δ
: 155.2 (C=N), 116.8, 117.6, 125.2, 125.4, 126.3, 127.3, 128.8, 131.0, 131.8,
3
134.7, 139.2, 140.5, 150.5, 155.2, 164.7 (Aromatic carbons). Anal. Calc. for C19
H
5 9
19CuN O S
(MW: 556.932 g/mol): C, 40.97; H, 3.44; O, 25.85; N, 12.57; S, 5.76; Cu, 11.41% and Found: C,
40.81; H, 3.39; O, 25.71, N, 12.41; S, 5.61; Cu, 11.29%.
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3.1.4. Bis-[4-(2-(((2-hydroxy-5-nitrophenyl) diazenyl) (phenyl) methylene) hydrazinyl)
benzene sulfonic acid] chromium III complex (2:1) (15).
Greyish Brown (Solid), Yield (91%), Melting Point (460ºC). λmax in nm (log ε): λmax1 360 (0.85),
-1
υ
λmax2 219 (0.92). FTIR (KBr, Cm ) max: 1520 (C=N, str), 1470 (N=N, str), 1605 (aromatic
1
3
76
C
=
C), 850 (CN=NC, str), 1410 (SO
3
H, str), 1345 (Ar-NO2, str), 640 (Metal-O, str). H-NMR
1
3
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3
3
3
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3
77
78
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80
81
82
83
84
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(CDCl
3
, 400 MHz)
3 3
δ: 11.35 (s 1H, SO H), 6.65-7.92 (m 24H, Ar-H). C-NMR (CDCl , 75
MHz)
δ
: 155.2 (C=N), 149.5 (C=N), 116.8, 117.6, 127.3, 125.2, 126.3, 127.6, 131.8, 132.1,
133.8, 133.4, 135.6, 137.8, 139.2, 140.5, 150.5, 164.7 (Aromatic carbons). Anal. Calc. for
C H CrN O S (MW: 930.799 g/mol): C, 49.03; H, 2.82; O, 20.63; N, 15.05; S, 6.89; Cr,
38
26
10 12 2
5.59% and Found: C, 48.95; H, 2.75; O, 20.45; N, 15.01; S, 6.69; Cr, 5.47%.
3.1.5. [4-(2-(((2-hydroxy-5-nitrophenyl) diazenyl) (phenyl) methylene) hydrazinyl) benzene
sulfonic acid] nickel II complex (1:1) (16).
Greenish Brown (Solid), Yield (87%), Melting Point (435ºC). λmax in nm (log
ε
): λmax1 370
max2 320 (1.25). FTIR (KBr, Cm ) max: 1505 (C=N, str), 1370 (N=N, str), 1615
(aromatic C C), 855 (CN=NC, str), 1320 (SO H, str), 1340 (Ar-NO str), 635 (Metal-O, str),
3450 (O-H, str). H-NMR (CDCl , 400 MHz)
-1
υ
(1.55),
λ
3
86
=
3
2,
1
3
3
3
3
3
3
3
87
88
89
90
91
92
93
δ: 11.28 (s 1H, SO H), 6.90-8.66 (m 12H, Ar-H).
3
3
1
3
C-NMR (CDCl , 75 MHz) δ: 155.2 (C=N), 111.5, 116.56, 117.6, 125.4, 127.3, 127.7, 128.8,
3
131.0, 134.7, 137.0, 139.2, 149.3, 150.5, 159.5 (Aromatic carbons). Anal. Calc. for
C H NiN O S (MW: 552.140 g/mol): C, 41.33; H, 3.47; O, 26.08; N, 12.68; S, 5.81; Ni,
19
19
5
9
10.63% and Found: C, 41.19; H, 3.35; O, 25.95; N, 12.56; S, 5.79; Ni, 10.55%.
3.1.6. [4-(2-(((2-hydroxy-5-nitrophenyl) diazenyl) (phenyl) methylene) hydrazinyl) benzene
sulfonic acid] cobalt III complex (1:1) (17).
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Dark Brown (Solid), Yield (88%), Melting Point (410ºC).
λ
max in nm (log
ε
):
λmax2 225 (1.17). FTIR (KBr, Cm ) max: 1490 (C=N, str), 1330 (N=N, str), 1600 (aromatic
C=C), 810 (CN=NC, str), 1220 (SO H, str), 1300 (Ar-NO str), 630 (Metal-O, str), 3330 (O-H,
λmax1 345 (1.20),
-1
υ
3
96
3
2,
1
13
3
3
3
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
4
97
98
99
00
01
02
03
04
05
06
07
08
09
10
11
12
13
14
15
16
str). H-NMR (CDCl , 400 MHz) δ: 11.19 (s 1H, SO H), 6.95-8.70 (m 12H, Ar-H). C-NMR
3 3
(CDCl , 75 MHz)
δ
: 155.2 (C=N), 111.5, 116.5, 117.6, 125.4, 127.3, 127.7, 128.8, 131.0, 134.7,
3
137.0, 139.2, 149.3, 150.5, 159.5 (Aromatic carbons). Anal. Calc. for C19 S (MW:
H
5 9
19CoN O
552.380 g/mol): C, 41.31; H, 3.47; O, 26.07; N, 12.68; S, 5.68; Co, 10.67% and Found: C, 41.29;
H, 3.41; O, 25.93; N, 12.61; S, 5.71; Co, 10.59.
3.2 FTIR Spectral Studies
Functional groups can be simply recognized in IR spectroscopy. Consequently, IR spectroscopy
considered as valuable basis for attaining the structural information of compounds that have
-1
organic nature. IR spectra of dyes (12-17) exhibited a sharp peak at 1580-1615 cm that
-
1
designated the presence of C=C (Aromatic stretching), a small peak at 1490-1540 cm indicated
the existence of C=N (Stretching) that approves the formation of formazan dye as shown in
-1
figure 1 (a). A small peak observed at 1305-1480 cm , exhibiting the presence of N=N
-1
(Stretching). While a broad peak at 3410 cm showed the N-H stretching in dye 12 as depicted
-1
in figure 1 (a). A sharp peak observed at 750-855 cm depicted the existence of C-N=N-C
-
skeleton from which also affirmed the formation of formazan. A peak observed at 1220-1420 cm
1
-1
-1
, 1300-1395 cm , 1130 cm indicated the presence of -S OH, Ar-NO , and Ar-OH respectively.
3
2
-1
A sharp and broad peak observed at 3330-3490 cm for OH functional group and small peaks
-1
observed at 630-680 cm indicated the formation and presence of metal-oxygen bond in terms of
metal-ligand bond to form metal complex formazan dyes as shown in figure 1 (b). Before
metallization, IR peaks of N-H and Ar-OH only were observed in dye (12) that acts as ligand and
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these IR peaks disappear after metallization as in dyes (13-17) as shown in Table 4 and figure 1.
While IR peaks of M-O only observed after metallization of dye (12) with metal like Fe, Cu, Cr,
Ni, and Co in dyes (13-17). And IR peaks for OH only observed in dyes (13, 14, 16 and 17) as
these are (1:1) metal complexes of Fe, Cu, Ni and Co respectively while absent in dye (15) as
this is (2:1) metal complex of Cr. FTIR results of this research work founded to be in close
agreement with the [3].
4
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Fig. 1. IR spectra of (a) and (b) for the synthesized formazan dyes 12 and 13 respectively
1
3.3 H-NMR spectral Studies
1
The H-NMR data shows that the chemical shift (δ) value of formazan dye 13 shifted to lower
field as compared to formazan dye 12. As the chemical shift value (δ) 7.60 is for Ar-H in
formazan dye 12 which has been shifted to lower field in formazan dye 13 and has 8.20 chemical
shift (δ) values for Ar-H as shown in figure 2 (a) and (b). This is because of the fact that in
formazan dye 12, there is two electron donating group such as N-H and Ar-OH is attached to the
aromatic ring that shifting the chemical shift (δ) value to higher field. As electron donating
groups are responsible for shifting the chemical shift (δ) value to higher field while electron
withdrawing group are favorable for shifting to lower field. But in formazan dye 13, both Ar-H
and N-H groups are not present. Furthermore this behavior of shifting of chemical shift (δ) from
higher field to lower field has been also observed in other formazan dyes (14-17) in contrast to
formazan dye 12. This fact is clearly justifiable that except formazan dye 12, both electrons
donating group N-H and Ar-H are not present in the structure of other formazan dyes as
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represented figure 2. These results were found in accordance with the previously reported data
1
[3]. H-NMR studies also depicted and confirmed the formation of metal complexes with the
formazan dye 12 which also act as ligand. As these two functional groups, N-H and Ar-OH are
showing their chemical shift (δ) value in formazan dye 12 but not in others formazan dyes (13-
17). This fact clearly and justifiably has confirmed the formation of coordinate covalent bond
between ligand (Dye 12) and metals Fe, Cu, Cr, Ni, and Co in formazan dyes 13, 14, 15, 16, and
17 respectively.
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Fig. 2. H NMR spectra of synthesized formazan dye 12 (a) and 13 (b) measured in CDCl at
3
25ºC
3.4 UV-visible spectral studies
The absorption maxima of the dye 12 that act as ligand and its respective metal complex dyes 13,
14, 15, 16 and 17, were recorded in water. Distinguishing three peaks are observed in the
spectrum of UV-vis formazans. The value of
λ
max1 is specific for formazans framework. For that
max1. Formazan peak value of max1 is usually
reason this research work relates to the value
λ
λ
experimental at 410 nm to 500 nm and will probably be redirected to 350 nm 600 nm but
depending on the molecular structure of formazan. These peak absorption is because of the
π→π* and n→π*, electronic transition in the framework of the formazan. λmax2 values commonly
appear in 300–350 nm, that are found to be in accordance with the electronic transitions of -
N=N- group which is present in the formazan molecule. λmax3 values are sometimes experimental
in nm 270-300 which is derived from the n→π* transition of a -C= N-functional group which is
present in the dye molecules. The electronic absorption spectra were recorded in the H
2
O. All
dyes have same chromophoric functionalities but large change in the max has been seen on metal
λ
complexation in the form of their bathochromic and hypochromic shift. Results were showed that
λmax1 values of dyes (12-17) were observed at 470, 380, 340, 360, 370 and 345 nm respectively
and the value of λmax2 for the dyes (12-17) observed at the wavelength of 340, 280, 218, 219, 320,
225 nm respectively as shown in Figure 3. This was indicated that there was found a shift of
longer to shorter wavelength (Hypsochromic effect). As the metal act as Lewis acid and attract
the electron density from the ligands towards itself that lead to shorter wavelength from longer
wavelength. There was found a blue shift of 90 nm for the Fe metal complex dye 13 from its
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474
475
476
477
ligand (un-metallized dye 12) with the color change from reddish brown to dark bluish brown.
The same phenomenon has been seen in all metal complexes i.e. Cu (14), Cr (15) , Ni (16) and
Co (17) with the blues shift of 130, 110, 100 and 125 nm respectively with color change from
reddish brown to blue, bluish beige, greyish beige and greenish blue respectively.
4
78
79
4
Fig. 3. Combine UV-Visible spectrum of synthesized formazan dyes (12-17)
3.5 Elemental analysis
480
481
482
483
484
485
486
487
488
489
490
491
Elemental analysis mostly said to be CHNS analysis. It involves the estimation of the masses of
the fractions of C, H, N, heteroatoms i.e. halogens, sulfur etc. and also the masses of the
fractions of metal atoms present in a sample. This gives the most useful information which has
its most significance in determining the structure of an unidentified chemical compound. It also
involved in ascertaining the purity as well as structure of a compound that is being synthesized in
research work (Tezcan, 2008). It was evident from the elemental analysis results that there was
founded a close agreement between the calculated results of elemental analysis as well as
founded results of elemental analysis of synthesized formazan dyes (12-17). Spectral as well
elemental analysis data were also confirmed the formazan dyes structures that are presented in
scheme 2 for dyes (12-17).
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4
4
4
4
4
4
4
5
5
5
5
5
5
5
5
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5
5
5
5
5
5
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00
01
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14
3.6 XRD Analysis
Single crystals growth of dye 12 i.e. 4-(2-(((2-hydroxy-5-nitrophenyl) diazenyl) (phenyl)
methylene) hydrazinyl) benzene sulfonic acid which act as ligand from numerous solvents
including DMF, ethyl alcohol, chloroform etc. unsuccessful and was characterized by powder X-
ray diffraction. X-ray powder diff raction analysis of the dye 12 and its metal complexes i.e. dye
(13-17) was carried out to determine the nature of lattice parameters, crystal system and the cell
volume. XRD patterns in the XRD spectrum indicates the crystalline nature of dye 12 and its
metal complexes as presented in Figure 4. Indexing of the diff raction patterns was performed
using High Score Plus software. From the indexed data the unit cell parameters were calculated
and are listed in Table 1. Powder XRD patterns of the metal complexes i.e. dye (13-17) are
totally diff erent from the un-metallized dye 12, validating the formation of coordination
compounds. It is found that dye 12, dye 13, dye 14, dye 16 and dye 17 have monoclinic
structures while dye (15) has an orthorhombic structure. The crystal structures of similar type of
compounds were reported as monoclinic and orthorhombic [32,33,34,31]. Moreover, by means
of the di
the Scherrer equation (D = 0.9
di raction angle, and is the full width at half maximum of the diff
ff
raction data, the mean crystallite sizes of the complexes, D, were resulted according to
/ ( cos ), where is X-ray wavelength (1.5406 ˚A), is Bragg
raction peak) [36]. The
40–70 nm and the
λ
β
θ
λ
θ
ff
β
average crystallite sizes of all the synthesized dyes (12-17) were found to be
∼
values are given in Table 1.
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Table 1 XRD data of formazan dyes 12-17
Dye# Lattice Parameters
Volume Crystallite
Crystal
system
3
(
A )
size D
a (A)
b (A)
c (A)
β (º)
(
nm)
59
1
1
1
1
1
1
2
3
4
5
6
7
10.0310 16.8315 8.1010 100.0111 1172.6181
Monoclinic
Monoclinic
Monoclinic
Orthorhombic
Monoclinic
Monoclinic
12.1201 4.0100
9.9989
99.7202
89.99
489.86
69
13.9999 10.9870 8.7986
1399.91
41
13.8901 12.0120 9.9910 109.9990 1499.99
16.0101 7.1021 13.9999 111.2011 1420.20
17.0010 7.9898 15.0129 119.9982 1831.90
40
70
55
516
5
17
18
5
(a)
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5
19
20
5
(b)
5
21
22
5
(c)
523
524
525
526
527
Fig. 4. XRD patterns of synthesized formazan dye 12 (a), dye 13 (b) and dye 14 (c)
3.7 Assessment of color properties
3.7.1. Fastness properties
Valuation of color shade, as well as fastness properties i.e. color change, staining on adjacent
fibre, light, wash and perspiration for un-metallized formazan dye (12) and metal complex
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5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
5
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31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
formazan dyes series (13-17) was checked on goat leather fabric. The detailed properties are
described in Table 2. All the synthesized un-metalized formazan dye (12) and metal complex
formazan dyes of Fe (13), Cu (14), Cr (15), Ni (16) and cobalt (17) have good penetration on
leather and produced color shades of Brown, Beige, Blue, Red, Grey, Black with different tones
like Reddish, Greyish, Olive, Bluish and Greenish on leather. Results were demonstrated that the
synthesized series of formazan dyes (12) have average wash fastness (3-4) but metal complex
formazan dyes (13-17) exhibited the good fastness that was from 4-5, 4-5, 5, 4 and 4-5
respectively. Wash fastness is the resistance force that is exerted by dyed fabric to retain its color
during washing either with detergent and soap. Maximum wash fastness properties were
demonstrated by chromium complexes (15). Color change, staining on adjacent fiber, Light and
perspiration fastness properties were also found to be good to excellent that exhibited by these
synthesized un-metalized formazan dyes (12) and metal complex formazan dyes of Fe (13), Cu
(14), Cr (15), Ni (16) and Cobalt (17) as shown in Table 2. These properties depend upon the
physical as well as the chemical interaction of dyes with the applied substrate (leather). There
always found a direct relationship between these properties (Color change, Staining on adjacent
fibre, Wash, Light, and Penetration) with the physical and chemical interactions of dyes and
applied substrate [37]. As the more are the electrostatic interactions then rapid diffusion of dyes
takes place to the substrate underneath depth; more will be the penetration level and all dyes (12-
17) were shown the excellent penetration level [37]. As a result, the synthesized dyes have all
properties to be good enough at all tested level. Figure 5 showed the color shades that developed
on leather by the application of un-metallized formazan dye (12) and metal complex formazan
dyes (13-17).
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