Synthesis and characterization of novel monoazo naphthalimide disperse dyes containing carboxylic acid group with high heat fastness properties

Article abstract of DOI:10.1002/jccs.200800194

A group of novel monoazo disperse dyes containing carboxylic acid-1,8-naphthalimide group has been synthesized. All intermediates and dyes were purified by recrystalization and the column chromatography method. The purified products were characterized by ¹H NMR, ¹³C NMR, FTIR, DSC, UV-VIS and Elemental Analysis. Spectrophotometric investigations of the synthesized dyes in different solvents were carried out in order to obtain their absorption maxima, molar extinction coefficients and solvatochromic effects. The absorption maxima of the synthesized dyes in acetone varied (513-549 nm) and the molar extinction coefficient was (17405-38939 l/mol cm). By changing the media from chloroform to DMF, the solvatochromism effect for all dyes increased. Dispersion of the synthesized dyes was prepared in water containing dispersing agent and applied to polyester fabrics. The dyed fabrics showed that all of the synthesized dyes were suitable for coloring polyester fibers, producing deep red to bluish red with very good fastness properties.

Full text of DOI:10.1002/jccs.200800194

1300
Journal of the Chinese Chemical Society, 2008, 55, 1300-1307
Synthesis and Characterization of Novel Monoazo Naphthalimide Disperse
Dyes Containing Carboxylic Acid Group with High Heat Fastness
Properties
Moosa Sadeghi Kiakhani,a Kamaladin Gharanjig,b* Mokhtar Arami,a
Javad Mokhtaric and Niyaz Mohammad Mahmoodib
aAmirkabir University of Technology, Textile Engineering Department, Tehran, Iran
bInstitute for Colorants, Paint and Coatings, Department of Organic Colorants, Tehran, Iran
cUniversity of Guilan, Department of Textile Engineering, Rasht, Iran
A group of novel monoazo disperse dyes containing carboxylic acid-1,8-naphthalimide group has
been synthesized. All intermediates and dyes were purified by recrystalization and the column chromatog-
raphy method. The purified products were characterized by 1H NMR, 13C NMR, FTIR, DSC, UV-VIS and
Elemental Analysis. Spectrophotometric investigations of the synthesized dyes in different solvents were
carried out in order to obtain their absorption maxima, molar extinction coefficients and solvatochromic
effects. The absorption maxima of the synthesized dyes in acetone varied (513-549 nm) and the molar ex-
tinction coefficient was (17405-38939 l/mol cm). By changing the media from chloroform to DMF, the
solvatochromism effect for all dyes increased. Dispersion of the synthesized dyes was prepared in water
containing dispersing agent and applied to polyester fabrics. The dyed fabrics showed that all of the syn-
thesized dyes were suitable for coloring polyester fibers, producing deep red to bluish red with very good
fastness properties.
Keywords: Disperse dyes; Naphthalimide; Heat fastness; Azo dyes; 4-Aminobutyric acid;
Synthesis.
INTRODUCTION
The early disperse dyes for the dyeing of cellulose ac-
erties. Apart from the mentioned properties the presence of
the amide functional group in these dyes resulted in their
lower volatility.
etate fibers were developed around 1923 and were subse-
quently used for the dyeing of nylon and polyester fibers.1
The importance of disperse dyes can be shown by their
high rate multi-million pound (£) businesses.2 Over 90% of
disperse dye usage is for the coloration of polyester and its
blends.2,3 Generally, the dyeing of polyester fibers is per-
formed at high temperatures (130 °C) or the thermosol
method (180-220 °C).1 Therefore, the disperse dyes must
be stable towards heat and sublimation. In recent years re-
search for finding disperse dyes with high heat fastness
properties have gained the attention of dye chemists.4 In
this respect, different groups of high heat fastness thienyl-
azo disperse dyes incorporating ester functions were syn-
thesized.4,5 These dyes have high molecular weight and in-
creased polarity which are derived from ester-based cou-
pling components exhibiting high fastness to dry heat prop-
The syntheses of several series of anthraquinone dis-
perse dyes containing carboxyl group were investigated.6
These dyes showed good sublimation and fastness proper-
ties on polyester fibers.
4-Amino-N-substituted-1,8-aphthalimide is a useful
intermediate for the synthesis of monoazo disperse dyes.
These dyes have been considered for dyeing of polyester fi-
bers.7-9 Diazotization of 4-amino-N-alkyl-1,8-naphthal-
imides and coupling to aryl amines gives red to bluish red
disperse dyes. The synthesized dyes have a very good af-
finity to polyester fibers with good color fastness proper-
ties and excellent sublimation fastness.
Several simple monoazo disperse dyes containing
acetylamino, carbamyl, phthalimide and naphthalimide
were synthesized and their dyeing properties on polyester
* Corresponding author. Tel: +98 21 22944184; Fax: +98 21 22947537; E-mail: gharanjig163@yahoo.com (K. Gharanjig);
mahmoodi@icrc.ac.ir (N. M. Mahmoodi)

Azonaphthalimide Dyes Containing Carboxylic Acid
J. Chin. Chem. Soc., Vol. 55, No. 6, 2008 1301
fibers were investigated.10-12 The results showed that
naphthalimide derivatives tended to undergo association in
the crystalline state, so they had good thermal stability.10
In our previous work, the synthesis of novel monoazo
N-ester-1,8-naphthalimide disperse dyes was reported.11
The N-ester group of disperse dyes caused an increase in
the dyeing capability, but these dyes do not have good heat
fastness at high temperatures (> 180 °C). Therefore, we de-
cided to substitute the N-ester group with the carboxylic
group. Our literature surveys showed that dyes with a naph-
thalimide base having a carboxylic functional group had
not been reported. Thus, in the present study, a series of
novel monoazo disperse dyes have been synthesized using
4-(4-amino-1,8-naphthalimido) butanoic acid as a diazo
component and N,N-diethylaniline, N,N-diethyl-m-tolu-
idine, N-ethyl-n-(2-hydroxy-ethyl) aniline and 3-(N,N-
diethylamino) acetanilide as the coupling components.
Acenaphthene was nitrated and treated using different unit
processes such as oxidation, imidation, reduction, diazo-
tization and finally coupled with selected amines. These
processes are represented in Figs. 1 and 2. The intermedi-
ates and dyes were purified and characterized by analytical
methods (1H NMR, 13C NMR, FTIR, DSC, UV-VIS and El-
emental Analysis). The spectrophotometric properties of
the synthesized dyes in various solvents were examined.
These dyes were applied to polyester fibers and their dye-
ing properties were investigated.
toluidine, N-ethyl-n-(2-hydroxyethyl)-aniline, 3-(N,N-di-
ethylamino) acetanilide were purchased from Aldrich and
used without further purification. Melting points were de-
termined by DSC (using a Perkin Elmer model Pyris). The
1H NMR and 13C NMR spectra were obtained on a Brucker
DRE AVANCE-500 MHz. FTIR absorption spectra were
recorded on a Nicolet 470/670/870. UV-VIS absorptions
were measured in a Cecil 9200 double beam spectropho-
tometer.
The colorimetric properties of the dyeing (D65 illu-
mination, 10° observer) were obtained using a gratig Mcbeth
7000A spectrophotometer.
Synthesis of intermediates
Synthesis of 4-nitronaphthalic anhydride
5-Nitroacenaphthene and 4-nitronaphthalic anhy-
dride were synthesized following the method of Okazaki et
al.13
EXPERIMENTAL
Materials and apparatus
Fig. 2. The chemical structure of dyes.
Acenaphthene, N,N-diethylaniline, N,N-diethyl-m-
Fig. 1. The synthesis procedure of intermediates.

1302 J. Chin. Chem. Soc., Vol. 55, No. 6, 2008
Kiakhani et al.
Synthesis of 4-(4-nitro-1,8-naphthalimido) butanoic
acid
Dyeing
A paste composed of crude dye (0.5 g), dispersing
agent (Lyoprint EV, Ciba Co., 1 g) and 20 mL water was
prepared by grinding the mixture with a ball mill. The mix-
ture was milled for 20 hours and diluted with addition of
water to 100 mL. Polyester fibers (1 g) were pretreated with
a nonionic detergent (Lotensol, Hansa Co., 5 g/l) at 80 °C
for 20 min prior to being used for the dyeing. Dyeing was
carried out in a Rotadyer apparatus using a liquor ratio
(L.R.) of 50:1, pH = 4-5 (acetic acid) with an appropriate
amount of dye to produce the standard depth. Dyeing was
performed by raising the dye bath temperature from 30 °C
to 90 °C at 2 °C/min, followed by 90 °C to 130 °C at 1
°C/min, holding at this temperature for 60 min and cooling
to 70 °C at 3 °C/min. The dyed fabrics were reduction
cleared using 2 g/l sodium hydrosulphite, 1 g/l sodium hy-
droxide and 1 g/l detergent for 20 min at 50 °C, then thor-
oughly rinsed with cold water.
3 g (0.02 mol) of 4-nitro-1,8-naphthalic anhydride
was dissolved in 70 mL absolute ethanol with stirring and
heating. 1.92 g (0.03 mol) 4-aminobutyric acid was added,
and the mixture was refluxed until TLC showed no 4-ni-
tro-1,8-naphthalic anhydride remained. This reaction was
completed in 2 hours. The mixture was then poured into
water. The precipitated solid was filtered off and recrystal-
lized by ethanol.
Synthesis of 4-(4-amino-1,8-naphthalimido) butanoic
acid
A mixture of 5.904 g (18 mmol) 4-(4-nitro-1,8-naph-
thalimido) butanoic acid and 20.31 g (90 mmol) stannous
chloride in 90 mL ethanol was refluxed for 1 hour with 22.5
mL hydrochloric acid till the reaction completed. The mix-
ture was poured into 200 mL water and the precipitated
solid was filtered off. The crude product was purified by
column chromatography (eluent: ethylacetate/hexane =
2/1).
RESULTS AND DISCUSSION
Synthesis of dyes
Diazotisation of 4-(4-amino-1,8-naphthalimido)
butanoic acid
Synthesis of intermediates and dyes
4-Nitro-1,8-naphthalic anhydride was reacted with
4-aminobutyric acid in absolute ethanol media under reflux
conditions. For monitoring the accomplishment of the reac-
tion, TLC techniques on silica gel 60 were used, and it was
completed in 2 hours. The time required for completion of
the imidation reaction for 4-nitro-1,8-naphthalic anhydride
with 4-amino-butyric acid is less than the imidation of 4-ni-
tro-1,8-naphthalic anhydride with alkyl glycinates.11 This
can be attributed to the amino acids being more active than
the alkyl glycinates in the nucleophilic displacement reac-
tion in which the attacking group is amine. 4-(4-Amino-
1,8-naphthalimido) butanoic acid was synthesized by the
reaction of 4-(4-nitro-1,8-naphthalimido) butanoic acid
with stannous chloride (II) in hydrochloric acid as a reduc-
ing agent and ethanol as a solvent. Purification of product
was carried out by column chromatography on silica gel G
(60-120) using an acetone and toluene mixture (with ratio
2/1) as an eluent. The physical and chemical properties of
the abovementioned intermediates such as the yields (Y%),
melting points and the form and color of crystals are sum-
marized in Table 1. The FTIR, 1H NMR spectra and ele-
mental analysis of intermediates are given in Table 2.
To prepare diazonium salt, 4-(4-amino-1,8-naphthal-
0.365 g (5.3 mmol) of sodium nitrite was added
slowly to 2.32 mL of concentrated sulphuric acid (98%) at
below 10 °C. The temperature of the reaction rose to 65 °C,
where no color change occurred. The solution was then
cooled to 5 °C and 1.57 g (5.3 mmol) of the powder of 4-
(4-amino-1,8-naphthalimido) butanoic acid was added slowly
to the solution for 45 min. The reaction mixture was stirred
for 3 hours.
Coupling
N,N-diethylaniline, N,N-diethyl-m-toluidine, 3-(N,N-
diethylamino) acetanilide, and N-ethyl-n-(2-hydroxyethyl)
aniline have been used as coupling components. Separately,
5.3 mmol of each coupling component was dissolved in 1
mL acetic acid. Then the clear diazonium salt solution was
added to these solutions. The reaction mixture was stirred
for 1 hour at below 10 °C. Then the pH of the solution was
maintained between 4 and 5 by adding drop-wise sodium
acetate solution. Stirring was continued for 3 hours at be-
low 10 °C. The dyes were filtered off, washed with hot wa-
ter and dried. The crude products were purified with pre-
parative TLC on silica gel (solvents: ethyl acetate / hexane
= 2/1 and 4/1).

Azonaphthalimide Dyes Containing Carboxylic Acid
Table 1. The characteristics of intermediates
J. Chin. Chem. Soc., Vol. 55, No. 6, 2008 1303
Reaction Conditions
Product
Intermediates
Reaction
Solvent
Time (hrs.)
mp (°C)
182.23
Y (%)
Form
Color
4-(4-Nitro-1,8-
naphthalimido)
butanoic acid
Imidation
Ethanol
2
91.46
needle
orange
4-(4-Amino-1,8-
naphthalimido)
butanoic acid
Reduction
Ethanol
1
158.84
96.82
needle
orange
Table 2. The FTIR, 1H NMR and Elemental Analysis of Intermediates
Intermediates
FTIR, 1H MNR and Elemental Analysis
1H NMR (acetone): d 1.2 (2H, p, J = 6.9, NCH2CH2CH2COOH); 2.4-
2.5 (2H, t, J =7.2 Hz, NCH2CH2CH2COOH); 4.2 (2H, t, J = 6.9 Hz,
NCH2CH2CH2COOH); 8.1 (1H, 6-H); 8.5 (1H, d, J = 7.9 Hz, 3-H); 8.7
(2H, 2-H, 5-H); 8.7-8.8 (1H, 7-H); 10.4 (1H, s, OH).
FTIR (KBr) n (cm-1): 2500-3600 (OH, carboxylic acid); 3074 (C-H str.
Ar); 1709 (C=O str, carboxylic acid); 1673, 1661 (C=O str. Carbonyl);
1585 (C=C str. Ar.), 1342, 1535 (NO2).
4-(4-Nitro-1,8-naphthalimido)
butanoic acid
Anal Calcd for C16H12N2O6: C, 58.5%; H, 3.6%; N, 8.5%; found: C,
59.0%; H, 3.6%; N, 8.3%.
1H NMR (acetone): d 1.2 (2H, p, J = 6.9, NCH2CH2CH2COOH); 2.4
(2H, t, J = 7.2 Hz, NCH2CH2CH2COOH); 4.1-4.2 (2H, t, J = 6.9 Hz,
NCH2CH2CH2COOH); 6.9 (2H, s, NH2); 6.9-7.0 (1H, d, J = 8.2 Hz, 2-
H); 7.6 (1H, t, J = 7.4 Hz, 6-H); 8.2-8.3 (1H, d, J = 8.3 Hz, 5-H); 8.4-
8.5 (2H, 2-H, 7-H); 10.4 (1H, s, OH).
FTIR (KBr) n (cm-1): 2500-3600 (OH str. carboxylic acid); 3361 (NH2
str.); 2929 (C-H str. Aliphatic); 1713 (C=O str. carboxylic acid); 1674,
1639 (C=O str. Carbonyl); 1580 (C=C str. Ar.).
4-(4-Amino-1,8-naphthalimido)
butanoic acid
Anal Calcd for C12H12N2O4: C, 64.4%; H, 4.6%; N, 9.3%; found: C,
64.8%; H, 5.1%; N, 9.6%.
imido) butanoic acid was reacted with nitrosyl sulfuric
acid. This reaction was completed in 3 hours. The obtained
diazonium salts were reacted with various coupling com-
ponents such as N,N-diethylaniline, N,N-diethyl-m-tolu-
idine, 3-(N,N-diethylamino) acetanilide and N-ethyl-n-(2-
hydroxyethyl)aniline in diluted acid media (pH = 4-5) (Fig.
2). Analytical data of the synthesized dyes (the yields
tron donating at suitable positions in the coupling compo-
nents affects the absorption characteristics of the dyes.
Bathochromic shift can be obtained by enhancing the elec-
tron donor properties of the couplers. Data in Table 3 show
that the presence of a methyl or acetyl group in the 3-posi-
tion of N,N-diethyl-m-toluidine and 3-(N,N-diethylami-
no)acetanilide related to N,N-diethylaniline caused a
bathochromic effect (~ 14-24 nm) in dyes 2 and 3.
The bathochromic shift of the NHCOCH3 group is
particularly large. It can be attributed to the stronger elec-
tron donor property of the –NHCOCH3 group.14
(Y%), DSC, FTIR, Elemental Analysis, 1H MNR and 13
C
NMR spectra) are shown in Tables 3 and 4.
Electronic absorption spectra
The spectrophotometric properties of the synthesized
dyes were recorded in acetone and are listed in Table 3.
Their absorption maxima were in the range of 511-545.5
nm. The colour of the synthesized dyes is influenced by re-
placing the coupling components. The introduction of elec-
The presence of an ethoxyamino group in benzene
ring dye 4 caused a hypsochromic shift relative to the N,N-
diethylamino group in dye 1.
The spectrophotometric measurements of the absorp-
tion maxima of dyes in DMF and acetone showed that the

1304 J. Chin. Chem. Soc., Vol. 55, No. 6, 2008
Kiakhani et al.
Table 3. The characteristics of dyes
Product
mp (°C)
Chloroform
Acetone
DMF
Dye
Y (%)
Form
Color
lmax (nm)
lmax (nm) e (l/mol.cm) lmax (nm)
1
2
3
4
148.32
149.79
194.19
139.23
82
85
73
85
needle
needle
needle
needle
red
522
534
525
539
549
513
23774.7
29887.9
38939.1
17405.2
536
549
558
523
bluish-red
bluish-red
red
545.5
511
Table 4. The 1H NMR, 13C NMR, FTIR, and Elemental Analysis of dyes
Dye
1H NMR, 13C NMR, FTIR, and Elemental Analysis
1H NMR (DMSO): d 1.2 (6H, t, J = 7.0 Hz, CH3); 1.2-1.9 (2H, p, J = 6.9 Hz, NCH2CH2CH2COOH); 2.4
(2H, t, J = 7.2 Hz, NCH2CH2CH2COOH); 3.5-3.6 (4H, q, J = 7.0 Hz, CH2CH3); 4.1 (2H, t, J = 6.9 Hz,
NCH2CH2CH2COOH); 6.9 (2H, 3¢-H, 5¢-H); 6.6-7.9 (4H, 6-H, 6¢-H, 2¢-H, 5-H); 8.5-8.6 (2H, 2-H, 7-H);
9.2 (1H, 3-H); 10.4 (1H, s, OH);
13C NMR (acetone): d (ppm) 12.63 (2C), 26.10, 32.03, 41.29, 43.96 (2C), 107.49, 112.11 (2C), 116.31
(2C), 121.32, 121.59, 128.23, 131.13, 135.29, 139.13, 139.29, 139.76, 149.05, 153.47, 163.31 (2C),
181.21.
1
FTIR (KBr) n (cm-1): 3442 (OH str. carboxylic acid); 2958 (C-H str. Aliphatic); 1735 (C=O str. carboxylic
acid); 1690, 1657 (C=O str. Carbonyl); 1586 (N=N); 1584 (C=C str. Ar.).
Anal Calcd for C26H26N4O4: C, 68.12%; H, 5.67%; N, 12.22%; found: C, 68.3%; H, 5.3%; N, 12.5%.
1H NMR (DMSO): d 1.2 (6H, t, J = 7.0 Hz, CH3); 1.9 (2H, p, J = 6.9 Hz, NCH2CH2CH2COOH); 2.4 (2H,
t, J = 7.1 Hz, NCH2CH2CH2COOH); 2.7 (3H, s, Ph-CH3); 3.5 (4H, q, J = 7.0 Hz, CH2CH3); 4.1 (2H, t, J =
6.9 Hz, NCH2CH2CH2COOH); 6.7 (2H, d, 3¢-H, 5¢-H); 7.9-8.0 (3H, 6-H, 6¢-H, 5-H); 8.5-8.6 (2H, 2-H, 7-
H); 9.3 (1H, 3-H); 10.3 (1H, s, OH);
13C NMR (CD3COCD3): d (ppm) 12.49 (2C), 16.96, 28.83, 32.87, 40.05, 46.73 (2C), 108.89, 110.19,
115.80, 119.24 (2C), 120.19 (2C), 120.93, 124.02, 126.88, 130.21, 134.61, 138.44, 139.23, 143.14,
156.33, 163.92 (2C), 186.17.
2
FTIR (KBr) n (cm-1): 3452 (OH str. carboxylic acid); 2924 (C-H str. Aliphatic); 1735 (C=O str. carboxylic
acid); 1689, 1652 (C=O str. Carbonyl); 1585 (N=N); 1580 (C=C str. Ar.).
Anal Calcd for C27H28N4O4: C, 68.64%; H, 5.93%; N, 11.86%; found: C, 68.2%; H, 6.1%; N, 11.7%.
1H NMR (DMSO): d 1.2 (6H t, J = 7.0 Hz, CH3); 2.0 (2H, p, J = 6.9 Hz, NCH2CH2CH2COOH); 2.3 (3H,
s, CH3); 2.0 (1H, s, OH); 2.4 (2H, t, J = 7.1 Hz, NCH2CH2CH2COOH); 3.5 (4H, q, J = 7.0 Hz, CH2CH3);
4.1 (2H, t, J = 6.9 Hz, NCH2CH2CH2COOH); 6.7 (1H, d, 5¢-H); 7.9 (1H, s, NH); 7.9-8.0 (2H, 6-H, 3¢-H);
8.2 (1H, d, 5-H); 8.5-8.6 (2H, 2-H, 7-H); 9.2 (1H, d, 3-H); 10.3 (1H, s, OH).
13C NMR (CD3COCD3): d (ppm) 11.45 (2C), 24.09, 26.96, 31.23, 41.89, 49.12 (2C), 106.13, 107.72,
108.32, 120.45, 120.99 (2C), 121.45, 123.42, 127.91, 131.02, 132.98, 135.79, 137.51, 140.12, 146.23,
154.91, 162.29 (2C), 168.14, 181.93.
3
FTIR (KBr) n (cm-1): 3438 (OH str. carboxylic acid); 2958 (C-H str. Aliphatic); 1729 (C=O str. carboxylic
acid); 1693, 1665 (C=O str. Carbonyl); 1585 (N=N); 1582 (C=C str. Ar.).
Anal Calcd for C28H29N5O5: C, 65.24%; H, 5.63%; N, 13.59%; found: C, 65.4%; H, 5.9%; N, 13.4%.
1H NMR (DMSO): d 1.2 (3H, t, J = 7.0 Hz, CH3); 1.2 (2H, t, J = 7.02 Hz, CH2CH2OH); 1.9-2.0 (2H, p, J
= 6.9 Hz, NCH2CH2CH2COOH); 2.4 (2H, t, J = 7.1 Hz, NCH2CH2CH2COOH); 3.5-3.6 (2H, p, J = 7.0 Hz,
CH2CH3); 4.2 (2H, t, J = 6.9 Hz, NCH2CH2CH2COOH); 7.0 (2H, 3¢-H, 5¢-H); 7.9-8.0 (4H, 6-H, 6¢-H, 5-H,
2¢-H); 8.5 (1H, d, 2-H); 8.6 (1H, d, 7-H); 9.2 (1H, d, 3-H); 10.3 (1H, s,OH).
13C NMR (CD3COCD3): d (ppm) 12.35, 27.62, 31.12, 40.67, 45.76, 54.39, 61.33, 108.02, 111.73 (2C),
114.98 (2C), 119.46 (2C), 120.79, 130.38, 132.53, 136.19, 136.78, 138.29, 140.31, 147.92, 158.47, 163.69
(2C), 185.10.
4
FTIR (KBr) n (cm-1): 2500-3600 (OH Str., carboxylic acid); 3457 (OH str. Alcohol); 2954 (C-H str.
Aliphatic); 1738 (C=O str. carboxylic acid); 1695, 1658 (C=O str. Carbonyl); 1599 (N=N); 1587 (C=C str.
Ar.).
Anal Calcd for C26H26N4O5: C, 65.24%; H, 5.63%; N, 13.59%; found: C, 65.4%; H, 5.4%; N, 13.6%.

Azonaphthalimide Dyes Containing Carboxylic Acid
J. Chin. Chem. Soc., Vol. 55, No. 6, 2008 1305
lowest Dlmax belonged to dye 3. Absorption maxima in Ta-
ble 1 revealed that the solvatochromism shifts between ace-
tone and DMF of the acetylamino derivatives relative to
methyl and unsubstituted N,N-diethylaniline derivatives
were smaller. This difference could be related to the weaker
solvatochromism of the acetylamino derivatives, despite
the fact that the acetylamino group of these dyes causes the
dyes to be bright and bathochromic as a result of intramo-
lecular hydrogen bonding.15
sized dyes with N-ester-1,8-naphthalimide disperse dyes
indicated that the presence of the carboxylic acid group
caused high heat fastness due to its more polar characteris-
tics.11
Dyeing and fastness properties
All dyes were applied to polyester fabric under high
temperature dyeing conditions with an appropriate amount
of dye to produce the standard depth. The concentrations of
dyes (1-4) to reach standard depth were 0.3% (omf) for
The lmax of dyes in chloroform, acetone and DMF
showed that there was a pronounced and a marked differ-
ence shift from less polar to more polar solvents. This be-
havior indicates that the polar excited states of the synthe-
sized dyes were stabilized by polarization interaction forces,
as the polariziability of the solvent was increased.16,17
Table 5. The colour fastnesses of dyes
Wash fastness
Heat fastness
210 °C
Light
Dye
Na
Ca
Change
fastness
1
2
3
4
2-3
3-4
4-5
2-3
2-3
3-4
4
3-4
4
4
4-5
4-5
5
4
Thermal stability of dyes
4-5
4-5
3-4
3-4
DSC analyses of the synthesized dyes are given in
Fig. 3. The results showed that there is no evidence of dye
destruction by increasing the temperature (250 °C). Thus,
they could be used for polyester dyeing at high tempera-
tures (130 °C) and the thermosol method (180-220 °C).
The comparison of fastness properties of the synthe-
3
5
a: Staining, N: Nylon, C: Cotton
Wash fastness and Heat fastness: 1 to 5 shows poor to excellent
fastness, respectively.
Light fastness: 1 to 8 represents poor to ideal light fastness,
respectively.
Fig. 3. DSC analysis of the synthesized dyes.

1306 J. Chin. Chem. Soc., Vol. 55, No. 6, 2008
Kiakhani et al.
Table 6. The spectrophotometric data of the synthesized dyes in standard depth
Dye
C (%)
L*
a*
b*
c*
h*
(K/S)
1
2
3
4
0.3
0.3
0.3
0.7
37.911
33.880
30.975
40.530
41.120
37.537
31.372
44.327
-1.187
-17.982
-27.972
1.922
55.92
50.56
42.03
60.063
358.34
334.40
318.20
2.48
9.545
10.463
12.450
8.987
L*: lightness, a* and b*: chromaticity coordinate, c*: chroma, h*: hue angle and K/S:
absorbance of dyed fabrics
dyes 1-3 and 0.7% (omf) for dye 4, respectively. 0.5% Ace-
have moderate light fastness.
tic acid (pH = 4.5-5) and 0.5% wetting agent were added.
Dyed fabric was reduction cleared in an aqueous solution
containing 2 g/l of sodium hydrosulphite, 1 g/l of sodium
hydroxide and 1 g/l detergent for 20 min at 50 °C. The
treated polyester was then rinsed with hot and cold water.
The dyed fibers showed that all of the synthesized
dyes had good buildup and very good leveling properties
on polyester fibers.
The colorimetric data of the dyeing were determined
by a reflectance spectrophotometer (Table 6). The results
showed that dyes 1-4 provided dyeing of bright red to blu-
ish-red shades.
CONCLUSIONS
A series of novel monoazo disperse dyes based on
naphthalimide having a carboxylic acid group with various
coupling compounds were synthesized and characterized.
It was found that by changing the coupling components, the
bathochromic and hypsochromic properties of dyes varied,
which could be related to the structure of the replaced
groups. Introducing electron donor and acceptor groups in
the coupler has an influencing effect on the bathochromic
and hypsochromic properties of the dyes. The electronic
absorption spectra of the synthesized dyes in various sol-
vents showed that they gave red to bluish-red hues. The
synthesized dyes were applied on polyester fabrics and
gave acceptable buildup and fastness properties. It is worth
mentioning that, due to the presence of carboxylic acid on
the dye molecules they have the hydrolysis potential in al-
kali media, which makes these dyes environmentally friendly
compounds.
The comparison of buildup properties of the monoazo
N-carboxylic, N-ester- and N-alkyl -1,8-naphthalimide dis-
perse dyes showed that the N-carboxylic-1,8-naphthal-
imide disperse dyes have the lowest buildup values on
polyester fibers.11,18,19 This phenomenon can be attributed
to the presence of the more polar carboxylic acid group of
dye molecules and its low affinity onto the hydrophobic
polyester fiber.
Almost all of the synthesized dyes saturated at a con-
centration of 1-1.5% owf. The rate and degree of exhaus-
tion of all dyes were relatively good. However, Dyes 2 and
4 had maximum and minimum exhaustion rates, respec-
tively.
The wash fastness properties of dyed samples were
assessed according to ISO 105 C06C2S at 60 °C wash fast-
ness test protocol. The change in shade and the degree of
cross staining on cotton and nylon were investigated visu-
ally with grey scales, and the results are shown in Table 5.
Dyes 1 and 3 have the lowest (2-3) and the highest
fastnesses of dyed fabrics, respectively. The presence of
the carboxylic acid group on naphthalimide moiety was not
an influencing parameter in determining wash fastness per-
formance.20
Received May 29, 2008.
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