Synthesis and Spectral Characterization of Novel ...

Fibers and Polymers 2016, Vol.17, No.5, 729-737 DOI 10.1007/s12221-016-5362-x

ISSN 1229-9197 (print version) ISSN 1875-0052 (electronic version)

Synthesis and Spectral Characterization of Novel Azomethine Disperse Dyes Derived from Pyrazolone Moiety and Their Dyeing Performance on Polyester Fabrics Mohamed A. El-Borai*, Hala F. Rizk, Gad B. El-Hefnawy, Seham A. Ibrahim, Samy S. Aser, and Hatem F. El-Sayed Department of Chemistry, Faculty of Science, Tanta University, Tanta 31527, Egypt (Received May 12, 2015; Revised January 29, 2016; Accepted April 11, 2016) Abstract: A series of new azomethine dyes based on pyrazolone system have been synthesized via different routes. The solvatochromism for the dyes was evaluated with respect to spectroscopic properties in various solvents. The dyes were applied as disperse dyes on polyester fabrics and gave shade poor to excellent light fastness, washing, perspiration, sublimation, and rubbing fastness properties. Also the position of color in CIELAB coordinates (L*, a*, b*) and K/S value were investigated. Keywords: Pyrazole-5-one, Pyrazole-4,5-diones, Azomethine dyes, Dyeing parameters, Fastness properties

SHIMADZO UV-3101PC spectrophotometer using 1.0 cm quartz cell. The 1H-NMR spectra were recorded on a Bruker AC spectrometer (300 MHz) at 25 oC in DMSO-d6 with TMS as an internal standard. Chemical shifts are reported in ppm and expressed as δ values. Mass spectra were measured on a Finnigan MAT 8222 EX mass spectrometer at 70 eV. Microanalysis was performed on a Perkin-Elmer 2400 Elemental Analyzer at Microanalytical center at Cairo University. Reaction progress was monitored by thin layer chromatography (TLC) using benzene/acetone (2/1 by volume) as eluent. 1,3-disubstituted-1H-pyrazol-5(4H)-ones 1a-l [1622], 1,3-disubstituted-1H-pyrazole-4,5-diones derivatives 2a-l [23-25], 4-benzylidene-1,3-diaryl-1H-pyrazol-5(4H)-one 3a-l [26-28], and 4-phenylazo-1,3-diaryl-1H-pyrazol-5(4H)-one 4a-l [29,30] were synthesized based on literature procedures. Actually, by trying methods A, B, and C we found that method A is the best one, which gave the highest mentioned yield in the experimental section.

Introduction The chemistry of pyrazolone derivatives has received much attention, because of their interesting structural properties and applications to diverse areas. For example, pyrazolin-5-ones are very important class of heterocycles, due to their potential pharmacological and biological applications [1-9]. Moreover, such heterocycles are extensively involved in the manufacture of commercial dyes, such as photographic dyes and textile dyes [10,11]. Azomethine dyes derived from pyrazolone are commonly used in color photography; usually these dyes are magenta in hue [12-15]. Herein we report the synthesis and dying properties for a series of novel azomethine dyes 1a-l derived from 1,3disubstituted-1H-pyrazol-5(4H)-ones with the hope that such dyes can be used in a commercial scale. To the best of our knowledge, there are only few examples of azomethine dyes that have been used for dyeing textiles with brightness color and good fastness.

Dyeing, Adsorption, and Fastness Determination Dyeing Procedure All applications and fastness properties of dye stuffs have been performed at Misr Spinning and Weaving Company, Central Q.C. Laboratories, Mehalla El-Kubra, Egypt. The synthesized dyes were applied to polyester fabrics and the dyeing procedures were carried out according to the reported procedures [31,33]. A dispersion of the dye was produced by dissolving the appropriate amount of dye (100 mg) in water (100 ml) and added dropwise with stirring to the dye bath (liquor ration 20:1) containing Setamol WS (1 %; sodium salt of a condensation product of naphthalene sulfonic acid and formaldehyde) as anionic dispersing agent of BASF. The pH of the dyebath was adjusted to 5.5 using aqueous acetic acid and the wetted-out polyester fabrics (5 g) were added. Dyeing was performed by raising the dye bath

Experimental Materials Commercially available polyester fabrics were used for dyeing. Chemicals and solvents were obtained from SigmaAldrich and were used without further purification. Apparatus Melting points were recorded on a Gallenkamp melting point apparatus and are reported uncorrected. The infrared spectra were recorded on a Perkin-Elmer FTIR 1430 pectrophotometer using KBr disk technique. Ultravioletvisible (UV-vis) absorption spectra were recorded on a *Corresponding author: [email protected] 729

730

Fibers and Polymers 2016, Vol.17, No.5

temperature to 130 oC at a rate of 3 oC/min, holding at this temperature for 60 min and rapid cooling to 50 oC. The dyed fabrics was rinsed with cold water and reduction cleared (1 g dm-3 sodium hydroxide, 1 g dm-3 sodium hydrosulfite), 10 min, 80 oC. The samples were rinsed with hot and cold water and finally air-dried. Fastness Determination Color fastness to light, washing, perspiration, and rubbing of the prepared dyes on polyester fabrics were studied using the standard method for the assessment color fastness of textile (the grey scale) [34]. The results obtained are recorded in Table 2. Fastness to Washing The test was assessed using a Launder-O-Meter sponsored by the American Association of Textile Chemists and Colorists (A.A.T.C.C.). A test specimen (10 cm×4 cm) of the dyed fabrics is taken and a samples (5 cm×4 cm) of the white cotton and polyester fabrics were placed in the container of the washing machine, with the necessary amount of the soap solution (5 g/l) previously heated to 50 oC. The specimen was rinsed twice in cold water for 10 min and squeezed, and then the composite specimen is opened out and dried in air. The color alteration of the uncovered portion of the specimen and the staining of both undyed fabrics was assessed using the international grey scale (Table 2). Fastness to Perspiration The test specimen (6 cm×6 cm) was placed between 2 species of undyed fabrics (cotton and polyester) and sewed along one side to form the test specimen. Testing fabrics were immersed into a solution of pH 4 at room temperature for 30 min. The solution was poured off and the sample was placed between two plastic plates (7.5 cm×6.5 cm) under a force of about 4.5 kg. The plates containing the composite samples were kept in an oven at 37 oC for 4 h. The specimen was then separated from the un-dyed samples. Colors alteration of dyed material and staining of the undyed samples were assessed using the international grey scale (Table 2). Fastness to Rubbing Test assessment was made according to the grey scale using a crockmeter of Atlas electronic type. Dyed fabrics to be tested were placed on the base of the crockmeter. A square of white testing cloth was mount over the end of the finger which protects downward on the specimen sliding back, and force to make ten complete turns of the crank at the rate of one turn per second. For wet rubbing test, the testing squares were thoroughly wet in distilled water and squeezed between filter papers through hand wringer under standard conditions. The rest of the procedure is similar to that used in dry rubbing test (Table 2). Fastness to Light The specimen of the dyed textiles were exposed, in a well ventilated exposure chamber to light from a xenon arc, along with dyed wool standards. The air temperature in the chamber was maintained at 30 oC. The effective humidity

Mohamed A. El-Borai et al.

was maintained at 45±5 %. The variation of light intensity over the area covered by specimen and standards should not exceed 20 %. The samples and standards were exposed simultaneously under the same conditions for the same time. The samples were viewed in the light from a day-light fluorescent lamp and given a degree in comparison with the relative to Blue scale (1-8) standards of A.A.T.C.C. (Table 2). Equilibrium Studies Five gram of polyester sample was dyed with dye concentrations (100 mg) in 100 ml water at 130 oC and pH 5.5 for 60 min. The quantities of dye adsorbed on polyester samples were estimated using the following equation. qe = ( C0 – Ce )V/W where qe is the quantity of dye adsorbed on polyester samples (mg/g) at equilibrium, C0 is the initial concentrations (1 mg), and Ce is equilibrium dye concentrations (mg/l), V is the volume of dye bath, and W is the weight of polyester sample (5 g). The percentage of adsorption of the synthesized dyes on polyester fabrics was 78-85 %. Color Assessment The colorimetric parameters of the dyed polyester fabrics were measured using a reflectance spectrophotometer (Gretag-Macbeth CE 7000a), equipped with a D65/10 o source and barium sulfate as standard blank, and three repeated measurements average settings. The assessment of color-dyed fabrics was made in terms of tristimulus colorimetry. General Procedure for the Synthesis of 4-(4-(dialkylamino) phenylimino-1,3-diaryl-1H-pyrazol-5(4H)-ones 5a-l Method A A solution of N,N-dialkyl-4-phenylenediamine (1.0 mmol) in ethanol (25 ml) was added dropwise over 15 min to a solution of 1a-l (1.0 mmol) in ethanol (5 ml) and sodium carbonate solution (10 %, 1 ml) with stirring. The reaction mixture was stirred at 0 oC for 20 min and then refluxed for 2 h. The reaction mixture was cooled to room temperature and the colored solid was filtered, washed with methanol, and crystallized from ethanol to give dyes 5a-l. Method B A solution of N,N-dialkyl-4-phenylenediamine (1.0 mmol) in ethanol (5 ml) was added gradually to a solution of 2a-l (1.0 mmol) in ethanol (5 ml). The reaction mixture was stirred at room temperature for one hour and then refluxed for 2 h. The mixture was cooled to room temperature and the colored solid was filtered, washed with methanol, and crystallized from ethanol to give compounds 5a-l. Method C A solution of silver nitrate (4 g, 2.4 mmol) in water

Synthesis, Characterization of Azomethine Disperse Dyes

(50 ml) was poured slowly into a vigorously stirred solution of sodium chloride (3.7 g, 6.5 mmol) and gelatin (0.3 g) in water (20 ml). To the resulting aqueous dispersion of silver chloride was added a solution of sodium carbonate (0.3 g) in water (20 ml) followed by a solution of 3a-l (6.0 mmol) and/ or 4-phenylazo-1,3-diaryl-1H-pyrazol-5(4H)-one 4a-l (6.0 mmol) in ethyl acetate (20 ml). A solution of N,N-dialkyl-4phenylenediamine (7.0 mmol; from reaction of N,N-dialkyl4-phenylenediamine using freshly precipitated of silver chloride) in water (20 ml) with stirring, over a period of one hour. The ethyl acetate solution of the dyes were separated, washed twice with water (2×10 ml), and evaporated to dryness. The resulting crude dyes were crystallized from ethanol to give dyes 5a-l. 4-(4-(Diethylamino)phenylimino)-1,3-diphenyl-1H-pyrazol5(4H)-one (5a) Obtained as dark purple crystal. Yield=81 %; mp 220222 oC. 1H-NMR (DMSO-d6, δ ppm): 3.12 (s, 6H, CH3), 7.11-8.67 (m, 14H, Ar-H). Anal. for C23H20N4O (368.43), calculated: C, 74.98; H, 5.47; N, 15.21; found: C, 74.13; H 5.03; N, 15.87. FT-IR (KBr, cm-1): 1600 (CH=N), 1670 (C=O), 2940 (Aliph-H), 3050 (Ar-H). Mass: m/e: 368 (M+). 4-(4-(Dimethylamino)phenylimino)-1-phenyl-3-(pyridin3-yl)-1H-pyrazol-5(4H)-one (5b) Obtained as red violet crystal. Yield=76 %. Mp.: 250252 oC. 1H-NMR (DMSO-d6, δ ppm): 3.23 (s, 6H, CH3), 7.24-9.23 (m, 13H, Ar-H). Anal. calculated for C21H18N5O (356.40), C, 70.77; H, 5.09; N, 19.65; O, 4.49; found: C, 70.25; H, 4.69; N, 19.22. FT-IR (KBr, cm-1):1550 (CH=N), 1680 (C=O), 2900 (Aliph-H), 3025 (Ar-H). Mass: m/e:356 (M+). 4-(4-(Dimethylamino)phenylimino)-1-(4-nitrophenyl)-3phenyl-1H-pyrazol-5(4H)-one (5c) Obtained as pink crystal. Yield=9 %. mp.: 210-212 oC. 1HNMR (DMSO-d6, δ ppm):3.24 (s, 6H, CH3), 7.19-8.75 (m, 13H, Ar-H). Anal. for C23H19N5O3 (413.42), calculated: C, 66.82; H, 4.63; N, 16.94; found: Calcd: C, 66.37; H 5.11; N, 16.21. FT-IR (KBr, cm-1): 1535 (CH=N), 1600 (C=O), 2940 (Aliph-H), 3100 (Ar-H). Mass: m/e:413 (M+). 4-(4-(Dimethylamino)phenylimino)-1-(2,4-dinitrophenyl)-3phenyl-1H-pyrazol-5(4H)-one (5d) Obtained as red violet crystal. Yield=80 %. mp.: 236-238 oC. 1 H-NMR (DMSO-d6, δ ppm):3.19 (s, 6H, CH3), 7.32-8.79 (m, 12H, Ar-H). Anal. for C23H18N6O5 (458.426), calculated: C, 60.26; H, 3.96; N, 18.33; found C, 60.89; H, 3.32; N, 18.87. FT-IR (KBr, cm-1): 1595 (CH=N), 1670 (C=O), 2980 (AliphH), 3020 (Ar-H). Mass: m/e:458 (M+). 4-(4-(Dimethylamino)phenylimino)-1-(2,4-dinitrophenyl)3-(pyridin-3-yl)-1H-pyrazol-5(4H)-one (5e) Obtained as pale red violet crystal. Yield=83 %. mp.: 175177 oC. 1H-NMR (DMSO-d6, δ ppm):3.31 (s, 6H, CH3), 7.24-9.23 (m, 11H, Ar-H). Anal. for C22H17N7O5 (459.413), calculated: C, 57.52; H, 3.73; N, 21.34; O, 17.41; found: C, 57.96; H, 3.22; N, 21.87. FT-IR (KBr, cm-1): 1520 (CH=N),


731

1610 (C=O), 2930 (Aliph-H), 3100 (Ar-H). Mass: m/e:459 (M+). 4-(4-(Dimethylamino)phenylimino)-3-(pyridin-3-yl)-1(2,4,6-trichlorophenyl)-1H-pyrazol-5(4H)-one (5f) Obtained as pink crystal. Yield=68 %. mp.: 125-127 oC. 1 H-NMR (DMSO-d6, δ ppm): 2.99 (s, 6H, CH3), 7.24-9.25 (m, 10H, Ar-H). Anal. for C22H16Cl3N5O (472.75), calculated: C, 55.89; H, 3.41; Cl, 22.50; N, 14.81; found: C, 55.31; H, 3.93; Cl, 22.11; N, 14.41. FT-IR (KBr, cm-1): 1550 (CH=N), 1620 (C=O), 2930 (Aliph-H), 3060 (Ar-H). Mass: m/e:474 (M+) 4-(4-(Diethylamino)phenylimino)-1,3-diphenyl-1H-pyrazol5(4H)-one (5g) Obtained as red violet crystal. Yield=77 %. mp.:120-122 oC. 1 H-NMR (DMSO-d6, δ ppm):1.52 (t, J=7.0 Hz, 3H, CH3), 3.38 (q, J=7.0 Hz, 3H, CH2), 7.56-8.21 (m, 14H, Ar-H). Anal. for C25H24N4O (396.48), calculated: C, 75.73; H, 6.10; N, 14.13; found: C, 75.41; H, 6.62; N, 14.62. FT-IR (KBr, cm-1): 1600 (CH=N-), 1640 (C=O), 2970 (Aliph-H), 3055 (Ar-H). Mass: m/e:396 (M+). 4-(4-(Diethylamino)phenylimino)-1-phenyl-3-(pyridin-3yl)-1H-pyrazol-5(4H)-one (5h) Obtained as violet crystal. Yield =82 %. mp.:150-153 oC. 1 H-NMR (DMSO-d6, δ ppm): 1.87 (t, J=7.0 Hz, 3H, CH3), 3.41 (q, J=7.0 Hz, 3H, CH2), 7.98-9.45 (m, 13H, Ar-H). Anal. for C24H23N5O (397.47) calculated: C, 72.52; H, 5.83; N, 17.62; found: C, 72.96; H, 5.61; N, 17.99. FT-IR (KBr, cm-1): 1500 (CH=N-), 1610 (C=O), 2960 (Aliph-H), 3050 (Ar-H). Mass: m/e:397 (M+). 4-(4-(Diethylamino)phenylimino)-1-(2,4-dinitrophenyl)3-phenyl-1H-pyrazol-5(4H)-one (5i) Obtained as dark purple crystal. Yield=70 %. mp.:130132 oC. 1H-NMR (DMSO-d6, δ ppm):1.47 (t, J=7.0 Hz, 3H, CH3), 3.51 (q, J=7.0 Hz, 3H, CH2), 7.39-8.41 (m, 12H, Ar-H Anal. for C25H22N6O5 (486.47) calculated: C, 61.72; H, 4.56; N, 17.28; found: C, 61.29; H, 4.94; N, 17.76. FT-IR (KBr, cm-1): 1600 (CH=N-), 1690 (C=O), 2990 (Aliph-H), 3055 (Ar-H). Mass: m/e:486 (M+). 4-(4-(Diethylamino)phenylimino)-1-(4-nitrophenyl)-3(pyridin-3-yl)-1H-pyrazol-5(4H)-one(5j) Obtained as red violet crystal. Yield=69 %. mp.:190192 oC. 1H NMR (DMSO-d6, δ ppm):1.52 (t, J=7.0 Hz, 3H, CH3), 3.29 (q, J=7.0 Hz, 3H, CH2), 7.31-9.19 (m, 12H, ArH). Anal. for C24H22N6O3 (442.47) calculated: C, 65.15; H, 5.01; N, 18.99; found: C, 65.78; H, 5.43; N, 18.47. FT-IR (KBr, cm-1): 1525 (CH=N-), 1620 (C=O), 2990 (Aliph-H), 3090 (Ar-H). Mass: m/e:442 (M+). 4-(4-(Diethylamino)phenylimino)-1-(2,4-dinitrophenyl)3-(pyridin-3-yl)-1H-pyrazol-5(4H)-one (5k) Obtained as red violet crystal. Yield=80 %. mp.:145-147 oC. 1 H-NMR (DMSO-d6, δ ppm):1.43 (t, J=7.0 Hz, 3H, CH3), 3.47 (q, J=7.0 Hz, 3H, CH2), 7.84-9.42 (m, 11H, Ar-H). Anal. for C24H21N7O5 (487.46) calculated: C, 59.13; H, 4.34; N, 20.11; found: C, 59.82; H, 4.94; N, 20.58. FT-IR (KBr,

732


cm-1): 1525 (CH=N-), 1610 (C=O), 2990 (Aliph-H), 3055 (Ar-H). Mass: m/e:487 (M+). 4-(4-(Diethylamino)phenylimino)-3-(pyridin-3-yl)-1-(2,4,6trichlorophenyl)-1H-pyrazol-5(4H)-one (5l) Obtained as violet crystal. Yield=78 %. mp.:110-112 oC. 1 H-NMR (DMSO-d6, δ ppm):1.64 (t, J=7.0 Hz, 3H, CH3), 3.29 (q, J=7.0 Hz, 3H, CH2), 7.56-8.21 (m, 10H, Ar-H). Anal. for C24H20Cl3N5O (500.80) calculated: C, 57.56; H, 4.03; Cl, 21.24; N, 13.98; found: C, 58.21; H, 4.68; Cl, 21.86; N, 13.58. FT-IR (KBr, cm-1): 1550 (CH=N-), 1625 (C=O), 2990 (Aliph-H), 3070 (Ar-H). Mass: m/e:502 (M+).

Results and Discussion The synthetic strategy for the preparation of azomethine dyes 5a-l is shown in Scheme 1. 4-(4-(Dialkylamino) phenylimino-1,3-diaryl-1H-pyrazol-5(4H)-ones 5a-l were synthesized from reaction of 1,3-diaryl-1H-pyrazol-5(4H)ones 1a-l and N,N-dialkyl-4-nitrosoanilines in the presence of sodium carbonate solution in ethanol under reflux condition. They could be also produced from reaction of 1,3disubstituted-1H-pyrazole-4,5-diones 2a-l and N,N-dialkyl4-phenylenediamine in ethanol. Moreover, dyes 5a-l were synthesized from reaction of 4-benzylidene-1,3-diaryl-1Hpyrazol-5(4H)-ones 3a-l or 4-phenylazo-1,3-diaryl-1H-pyrazol-


5(4H)-ones 4a-l with N,N-dialkyl-4-phenylenediamine in the presence of silver nitrate as inorganic oxidant and gelatin. The dyes were purified by crystallization from ethanol, and their purity was examined by thin-layer chromatography (TLC). The structures of dyes 5a-l were confirmed by various spectroscopic techniques including FT-IR, UV-Vis, 1H-NMR, and mass spectrometry along with elemental analyses. The IR spectra of dyes 5a-l showed characteristic absorption peaks due to stretching frequency of the azomethine group in the region of 1500-1600 cm-1 and the stretching frequency of the carbonyl group at 1610-1690 cm-1 region. Furthermore, the 1H-NMR spectra of compounds 5a-f showed the presence of singlet signals attributed to CH3 protons within the region of 2.99-3.31 ppm and multiplets at δ 7.11-9.25 ppm region corresponding to aromatic protons. Also the 1H-NMR spectra of azomethine dyes 5g-l showed the presence of ethyl groups that resonated as triplet signals that are attributed to the CH3 protons at δ 1.43-1.87 ppm and quartets that are attributed to the CH2 protons within the 3.29-3.51 ppm region. The structures of the synthesized dyes 5a-l were further confirmed by the use of mass spectra and showed the molecular ion peaks in all cases (see experimental section). The synthesized dyes 5a-l were applied to polyester fabrics as disperse dyes. The fastness and colorimetric

Scheme 1. Synthesis of 4-(4-(dialkylamino) phenylimino-1,3-diaryl-1H-pyrazol-5(4H)-ones 5a-l.



properties were measured. The results revealed that the dyes have poor to excellent fastness and moderate to very good affinity to polyester fabrics. The percentage of dye adsorbed on polyester samples were estimated using Langmuir equation [35]. The percentage

733

of adsorption of the synthesized dyes on polyester fabrics is 78-85 %. The solvatochromic behavior of the dyes in various solvents such as methanol, DMF, benzene, and 1,2-dichloroethane was studied. The substituent and acid effects on the visible

Table 1. Visible absorption spectra in various solvents for compounds 5a-l

No

Color

T*

5a

Dark purple

28.7

5b

Red violet

22.0

5c

Pink

19.1

5d

Red violet

41.1

5e

Red violet

22.8

5f

Pink

63.0

5g

Red violet

59.9

5h

Violet

22.7

5i

Dark purple

32.4

5j

Red violet

18.1

5k

Red violet

33.2

5l

Violet

63.2

Absorption λmax (nm) (benzene)

ε

239 445 514 235 448 521 234 440 510 234 410 539 332 408 551 330 446 535 266 447 520 235 448 526 239 411 523 236 414 588 320 414 522 239 412 540

100000 7856 11838 68754 10631 205833 83333 17063 12346 6760 13958 16543 6648 17446 5770 26613 25680 59160 8765 8734 16091 12762 5692 8331 100000 17160 13452 8333 24120 1900 6020 22110 1197 41666 95666 46916

T* : Tetrahedral angle of N**-N*-C=C.

Absorption λmax (nm) (1,2-dichloroethane) 260 446 527 274 451 552 270 421 560 266 447 530 254 417 564 260 440 545 266 447 534 269 443 543 261 420 569 260 440 530 263 440 543 261 423 550

ε

Absorption λmax (nm) (MeOH)

ε

Absorption λmax (nm) (DMF)

ε

27971 10750 20318 9076 17496 512104 7981 7837 44248 10278 9442 13820 9200 22742 133711 15353 5843 13383 23621 38855 12510 45890 46680 96980 23621 38855 14022 6736 8953 22036 1045 9290 96980 8195 9841 6337

335 449 546 274 451 552 329 445 537 299 429 564 265 416 574 266 444 563 275 449 547 349 445 558 264 424 578 307 437 557 276 446 548 279 451 550

3227 2276 4891 49076 17496 51210 25996 132970 93595 15180 24137 11042 31690 37862 12528 32276 7710 21358 30470 10053 25996 45990 26158 53244 45990 37420 11042 15787 19121 4891 19391 27863 51313 15430 6216 17516

307 449 545 299 454 550 331 445 549 349 442 558 275 415 542 307 448 565 315 448 548 350 441 556 281 424 576 289 445 567 339 450 576 317 446 548

14920 7422 21400 38440 17400 50600 4887 3625 9700 37833 21716 44333 32883 44200 14666 14920 7422 21400 8440 5800 15320 45400 26060 53040 14555 20566 5922 23800 7400 21200 15850 10550 23975 10200 7220 18162

734


absorption maxima of the dyes were also considered. UV-Vis Spectroscopic Analysis of Dyes 5a-l The electronic absorption spectra of compounds 5a-5l were recorded in four different solvents that represent three categories of organic solvents; methanol (polar protic solvent), DMF (dipolar aprotic solvent), benzene (non polar solvent), and 1,2-dichloro ethane (a polar aprotic solvent). Generally, variation in color of dyes results from the alteration in coupling components. The convenient method for measuring the color of dyes is by studying the absorption spectral of their solutions. The visible absorption maxima for the synthesized dyes were measured, listed in Table 1, and represented in Figures 1-4. The spectra of different compounds in methanol are represented in (Figure 1(a) and 1(b)) and showed three absorption bands in the wavelength regions of λ=265-335 nm (λmax A), λ=416-451 nm (λmax B), and λ=537-578 nm (λmax C). According to the literature data [36,37]; the π-π* and n-π* transitions of the carbonyl group of pyrazolone ring lies at λ=265-380 nm and 208 nm, respectively. The π-π* transition

Figure 1. (a) Absorption spectra of dyes 5a-f in MeOH (1×10-5 M) and (b) absorption spectra of dyes 5g-l in MeOH (1×10-5 M).


of C=N of pyrazolone at around λ=300 nm. Also, the different π-π* transitions of aromatic aryl absorbed in the region of λ=200-280 nm. So the first absorption band (λmax A) in the UV and the boarder of the visible region is composed of different overlapping π-π* and n-π* transitions of pyrazolone, pyridyl ring, and aryl group in the investigated dyes. The visible broad bands (λmax B) and (λmax C) that appear in the range of λ=416-451 and λ=537-578 nm, respectively, can be assigned to two different charge transfer bands. The band B appears in the range of λ=416-451 nm due to migration of the lone pair of electron of N1 on pyrazolone ring to antibonding π electron of the phenyl or aryl group attached N1 (aπ), l→aπ transition [38]. This band disappeared in the acid medium pH 1 (Figure 2(a) and 2(b)) and has a high extinction coefficient rather than n-π* transitions. The position of this band is affected mainly by four factors: 1. The important factor is the non-coplanarity of the aryl or phenyl group attached to N1 of pyrazolone. We have calculated the tetrahedral angle N2-N1-C=C using a Mopac

Figure 2. (a) Absorption spectra of dye 5a in various solvents and acidic buffer (1×10-5 M) and (b) absorption spectra of dye 5g in various solvents and acidic buffer (1× 10-5 M).


Figure 3. Optimized molecular structure for compound 5a.

Figure 4. Optimized molecular structure for compound 5g.

and AMI theory (Table 1). It appears from the Table that the tetrahedral angle increases the probability of such transition increases εmax for 5g>εmax for 5a where the tetrahedral angle in 5g (59.9 o)>tetrahedral angle in 5a (28.7 o) (Figures 3 and 4). With increasing the non-coplanarity of the phenyl ring until the plane of phenyl ring become perpendicular to the plane of pyrazolone, a great interaction is permitted between the lone pair of electron on nitrogen atom and a π system of


735

the phenyl ring, affecting the position of this transition (λmax B). Thus, as seen in the Table 1, 5a, 5l, 5i, and 5h that has a phenyl group attached to N1 are red shifted compared with the other compounds that carry aryl group attached to N1 of pyrazolone. 2. The inductive and mesomeric effects of the C=O group of pyrazolone decrease the charge on N1. 3. The field effect of N2 and the substituent at position 3 of pyrazolone ring. 4. The substituent in aryl ring attached to N1 since the extinction coefficient can be regards as a rough value to the probability of the electronic transition. We found that, in methanol as a solvent, compounds 5a, 5f, and 5l have low probability of transition compared to the others, but the energy gap between ground and excited states is smaller (red shift). The band (λmax C) is due to the migration of the lone pair of electron from NMe2 groups as a donor center to the carbonyl group of the pyrazolone moiety as an acceptor center (Scheme 2). In the acid medium of pH 1, the charge transfer band (λmax C) disappeared due to the protonation of NMe2 groups which prevent this charge transfer as well as from the sensitivity of its λmax owing to the type of substituent, whereas the band for NMe2 group gave a red shift in all solvents, that is the case for compounds 5a, 5g, 5h, and 5b where N1 carry phenyl groups. This is also correct for compounds 5f and 5l in low polarity solvents (benzene and 1,2-dichloroethane). For compounds (5a-5f) and (5g-5l) that differ in NMe2 and NEt2 groups, the difference in inductive effect does not appear clearly on the position of the charge transfer band because the substituent on aryl group on the N1 affects the electron density on carbonyl group of pyrazolone. It can be seen from Table 1 that for solvatochromism behavior of the dyes 5a, 5k, and 5i, the band (λmax C) exhibits an apparent shift towards longer wavelength in different solvents in order of benzene < 1,2-dichloroethan < DMF < MeOH. For compounds 5j, 5k, and 5l the sequences follow the order of benzene < 1,2-dichloroethan < MeOH < DMF. This shift does not agree with the change of polarity of organic solvents. Therefore, the solvatochromism is a result of combination of several solvent characteristics such as acidity, basicity,

Scheme 2. Resonance structure of 4-(4-(dialkylamino) phenylimino-1,3-diaryl-1H-pyrazol-5(4H)-ones 5a-l.

736



Table 2. Fastness properties of dyes 5a-l on polyester fabricsa Dye. no

a

Color of dyes

Perspiration Acidic Alkali

Washing Change Stain

Rubbing

Light

Adsorption qe%

Dry

Wet

5a

4

4

4

4

3

3

1-2

78

5b

4

4

3

3

2

2

4-5

85

5c

4

2-3

4

4

1-2

4

2-3

82

5d

3-4

3

4

3

1-2

3

1-2

79

5e

4

4

4

4

1

3

5

81

5f

4

4

4

4

2

2

4

79

5g

3

4

4

4

4

4

4

83

5h

3

4

3

3

3

3

5

85

5i

3

4

4

4

4

3

5

84

5j

4

4

4

4

4

3

5

85

5k

3

4

4

3

4

3

4

80

5l

4

4

4

4

3

3

4

81

Rate for light fastness: 4-8 (acceptable), 1-3 (not acceptable); rate for different fastness: 3-5 (acceptable), 1-2 (not acceptable).

polarizability, and dipolarity. Dyeing Properties of the Synthesized Dyes Disperse mono azomethine dyes were applied on polyester fabrics. Their dyeing properties are shown in Table 2. These dyes gave a wide range of colors varying from pink to dark red violet shades on the fabrics. The variation in the shades of the dyed fabrics result from the nature of the substituent present on aryl group on N1 where the presence of electron withdrawing group on aryl group has a negative effect on the fastness properties because it decreases the hydrophobic character. The dyeing properties showed poor to good fastness to light and very good to excellent washing, perspiration, and rubbing fastnesses except 5c and 5d for dry rubbing fastness. Color Assessment The following CIELAB coordinates are measured. L* is lightness, a* represents the degree of redness (positive) and greenness (negative), and b* represents the degree of yellowness (positive) and blueness (negative). The measured K/S values given by the reflectance spectrometer are directly correlated with the dye concentration on the dyed substrate according to the Kubelka-Munk equation. The obtained results were depicted in Table 3. The color coordinates indicate that the dyes have good affinity to polyester fabrics with moderate to very good brightness and color depth. The color lightness value (L*) of the dyes 5a-l vary from (20.89-54.70). Dyes 5c, 5d, 5e, 5f, 5h, 5i, 5j, and 5l are lighter and duller compared with the other dyes. On the other hand, K/S values of the dyes 5a-l vary from 1.86 to 21.03. Dyes 5a, 5b, 5g, and 5k are

Table 3. Color of the dyes 5a-l on polyester fabrics Dyes no. 5a 5b 5c 5d 5e 5f 5g 5h 5i 5j 5k 5l

L* 20.89 25.90 37.23 54.70 41.66 37.40 26.70 40.40 34.40 43.30 28.70 43.30

a* 13.60 12.90 12.87 14.99 22.34 16.60 21.36 15.70 6.72 16.40 8.88 16.40

b* -12.50 -22.50 -19.60 -14.60 -18.40 -9.51 -18.40 -14.80 -18.90 -24.80 -14.40 -24.80

R% 2.31 3.25 7.04 18.00 8.54 6.97 2.27 8.50 6.30 9.30 4.40 9.30

K/S 20.75 14.44 6.18 1.86 4.95 6.17 21.03 4.90 6.72 4.42 10.38 4.42

characterized by higher K/S values compared with the other dyes indicating that the color strength on polyester fabrics is increased.

Conclusion In this work, we have synthesized a series of twelve azomethine dyes based on pyrazolone moiety. The solvatochromic behavior and substituent effects in four different solvents were evaluated. The results indicated that the absorption of these dyes was dependent on the polarity of solvents. The synthesized dyes were applied as disperse dyes for dyeing polyester fabrics. These dyes gave a wide range of colors varying from pink to dark red violet shades


on the fabrics. The light, washing, rubbing, and perspiration fastnesses of all patterns dyed with azomethine disperses dyes show poor to excellent fastness properties. Also, the color coordinates indicate that the dyes have good affinity with moderate to very good brightness and color depth to polyester fabrics.

References 1. B. Peng, G. Liu, L. Liu, D. Jia, and K. Yu, J. Mol. Struct., 692, 217 (2004). 2. P. N. Dhol, T. E. Achary, and A. Nayak, J. Ind. Chem. Soc., 52, 196 (1975). 3. F. R. Souza, V. T. Souaza, V. Ratzalaff, L. P. Borges, M. R. Olivera, and H. G. Bonacorso, Eur. J. Pharmacol., 45, 141 (2002). 4. J. Singh and R. Tripathy, PCT Int. Appl., 138 (2001). 5. M. Arnost, A. Pierce, E. Haar, D. Lauffer, J. Madden, K. Tanner, and J. Green, Bioorg. Med. Chem. Lett., 20, 1661 (2010). 6. T. Arai, M. Nonogawa, K. Makino, N. Endo, H. Mori, T. Miyoshi, K. Yamashita, M. Sasada, M. Kakuyama, and K. Fukuda, J. Pharmacol. Exp. Ther., 324, 529 (2008). 7. R. R. Venkat, V. Vijaykumar, and N. Suchetha Kumari, Eur. J. Med. Chem., 44, 3852 (2009). 8. S. J. Ratnadeep, G. M. Priyanka, D. D. Santosh, K. D. Sanjay, and H. G. Charansingh, Bioorg. Med. Chem. Lett., 20, 3721 (2010). 9. X. L. Rena, B. Hua, and H. Z. Yang, Arkivoc, 15, 59 (2005). 10. K. K. Ramanaumar, A. G. Raghavendra, V. Srilalitha, G. S. Narayana, and L. K. Ravindranath, ScientiaIranica C, 19, 605 (2012). 11. H. F. Rizk, M. A. El-Borai, G. B. El-Hefnawy, and H. F. ElSayed, Chin. J. Chem., 27, 1359 (2009). 12. M. C. Godoy, M. R. Fighera, F. R. Souza, A, E. Flores, M. A. Rubin, M. R. Oliveira, N. Zanatta, M. A. P. Martin, H. G. Bonacorso, and C. F. Mello, Eur. J. Pharmacol., 496, 93 (2004). 13. S. Yokoyama, T. Sato, K. Kimura, N. Furutachi, and O. Takahashi, U. S. Patent, 5,026,867 (1991). 14. R. A. Clarke and N. J. Pitman, U. S. Patent, 4,092,104 (1978). 15. D. E. Machiele and N. Y. Rochester, U. S. Patent, 3,952,009 (1976).


737

16. G. H. Brown, B. Graham, P. W. Vettum, and A. Weissberger, J. Am. Chem. Soc., 73, 919 (1951). 17. M. A. Elborai, E. A. Aly, M. Fahmy, and A. A. Gaber, Delta J. Sci., 17, 110 (1993). 18. W. Hansel, Arch. Pharm., 309, 900 (1976). 19. W. G. Herkstroeter, J. Am. Chem. Soc., 95, 8686 (1973). 20. D. P. Maier, G. P. Happ, and T. H. Regan, Org. Mass Spectrom., 2, 1289 (1969). 21. N. G. Rossmann, B. Winnig, and W. Aeise, J. Prakt. Chem., 329, 767 (1987). 22. A. Sammour, T. Zimaity, and M. El Borai, J. Prakt. Chem., 314, 612 (1972). 23. A. Loria, Ger. Pat. 1,181,057 (1964); Chem.A bstr., 62, 2865e (1965). 24. A. I. M. Koraiem, J. Prakt. Chem., 5, 695 (1984). 25. H. F. Rizk, Bulg. Chem. Comm., 41, 241 (2009). 26. H. Wiley and S. Davies, J. Am. Chem. Soc., 76, 4931 (1954). 27. L. Koike and K. Okawa. J. Chem. Soc., 57, 56 (1954). 28. T. L. Jacobs and R. C. Elderfield, Heterocyclic. 5, 116 (1957). 29. G. B. Hefnawy, M. A. El-Borai, E. A. Aly, and A. A. Gaber, Indian J. Fiber Text. Res., 17, 87 (1992). 30. G. B. Hefnawy, M. A. El-Borai, E. A. Aly, and A. A. Gaber, Ind. J. Fiber Text. Res., 17, 160 (1992). 31. H. F. Rizk, M. A. EI-Badawi, S. A. Ibrahim, and M. A. ElBorai, Indian J. Org. Chem., 4, 115 (2007). 32. H. F. Rizk, M. A. EI-Badawi, S. A. Ibrahim, and M. A. ElBorai, J. Korean Chem. Soc., 154, 737 (2010). 33. H. F. Rizk, M. A. EI-Badawi, S. A. Ibrahim, and M. A. ElBorai, Arabian J. Chem., 4, 25 (2011). 34. Anonymous, “Standard Methods for the Determination of the Color Fastness of Textiles and Leather”, 5th Ed., The Society of Dyes and Colorists, Bradford, England, 1990. 35. M. Ghaharpour, A. Rashidi, and H. Tayebi, World Appl. Sci. J., 14, 1291 (2011). 36. J. Eluguero and R. Jacquier, Bull. Soc. Chim. France, 8, 2832 (1966). 37. S. B. Buyuktas, Synth. React. Inorg. Met-Org Chem., 24, 1179 (1994). 38. George G. Guilbault, “Fluorescence: Theory, Instrumentation and Practice”, p.207, Edward Arnold Ltd., NewYork, 1967.