Diphenyl ( 4 ′-( Aryldiazenyl ) biphenyl-4-ylamino ) ( pyridin-3-yl ) methylphosphonates as Azo Disperse Dyes for Dyeing Polyester Fabrics

Diphenyl (4′-aminobiphenyl-4-ylamino)(pyridin-3-yl)methylphosphonate (1) was synthesized in 88% yield from reaction of pyridine-3-carboxaldehyde with benzidine and triphenylphosphite in the presence of titanium tetrachloride as a catalyst. Diazotization of 1 gave the corresponding diazonium salt 2 which was coupled with several hydroxyl or amino compounds to give the corresponding azo dyes 3–8 in 82–88% yields aer crystallization. e dyes produced were applied to polyesters as disperse dyes and their fastness properties were elevated.

e growth of the spinning and weaving industry prompted researchers to develop synthetic dyes to satisfy different industrial demands [18].e most important class of synthetic dyes is azo dyes that form along with pigments the largest group of synthetic colorants that play prominent role in various applications.

Experimental
Melting point determinations were performed by the open capillary method using an Electrothermal MEL-TEMP II apparatus and are reported uncorrected.IR spectra were recorded on a Perkin-Elmer 1430 Spectrophotometer using KBr disc technique. 1H NMR spectra were recorded on a Bruker AC400 spectrometer operating at 400 MHz.e spectra were recorded in DMSO- 6 .Chemical shis  are reported in parts per million (ppm) relative to TMS and coupling constants  are in Hz and have been rounded to the nearest whole number.Assignments of signals are based on integration values and expected chemical shi values and have not been rigorously con�rmed.EI mass spectra were recorded at energy 70 eV with a 7070 EQ mass spectrometer.Microanalyses were performed by analytical service at both the Universities of Tanta and Cairo, Egypt.Analytical thin layer chromatography (TLC) was performed on EM silica gel F 254 sheet (0.2 mm) with chloroform/acetone (5 : 2 by volume) as a developing eluent.e spots were detected with UV Lamp Model UV GL-58.Reagents and solvents were used from commercial sources without puri�cation.

General Procedure for the Synthesis of Compounds 3-8.
A cold (0 ∘ C) solution of sodium nitrate (0.76 g, 11 mmol) in H 2 O (10 mL) was added gradually to a cold (0 ∘ C) suspension of 1 (5.07 g, 10 mmol) in conc.HCl (5 mL).e diazonium salt 2 thus obtained was added with continuous stirring to a cold (0 ∘ C) solution of coupler (10 mmol) in aqueous NaOH solution (10%, 15 mL).e mixture was stirred at 0 ∘ C for 30 min and the dye obtained was �ltered, washed with H 2 O, dried, and crystallized from ethanol to give products 3-8.

Dyeing
Procedure.e fabric was dyed with dye (2%; calculated by weight of the fabric) and Avolan IS (1%; Bayer AG, Germany) as dispersing agent, kept at a liquor ratio of 20 : 1. e process was started at 60 ∘ C; the temperature was then raised to 130 ∘ C over 30 min and maintained there for 1 h.Aer cooling, the fabric was removed and then treated with a solution of NaHSO 4 (2%), NaOH (2%), and the dispersing agent Avolan IS (0.1%) at 70 ∘ C for 30 min.Finally, the fabric was rinsed and dried at 60 ∘ C.

Fastness to Washing.
A specimen of dyed polyester fabric was stitched between two pieces of undyed cotton fabric, all of equal length, and then washed at 50 ∘ C for 30 min.
Fastness to Perspiration.e samples were prepared by stitching a piece of dyed polyester fabric between two pieces of undyed cotton fabric, all of equal length, and then immersed in the acid or alkaline solution for 30 min.e acid solution (pH = 3.5) contained sodium chloride (10 g/L), lactic acid (1 g/L), disodium orthophosphate (1 g/L) and histidine monohydrochloride (0.25 g/L).e alkaline solution (pH = 8) contained sodium chloride (10 g/L), NH 4 Cl (4 g/L), disodium orthophosphate (1 g/L), and histidine monohydrochloride (0.25 g/L).
Fastness to Rubbing.e dyed polyester fabric was placed on the base of the Crockmeter, so that it rested �at on the abrasive cloth with its long dimension in the direction of rubbing.A square of white testing cloth was allowed to slide on the tested fabric back and forth twenty times by making ten complete turns of the crank according to the international standard procedure.For the wet rubbing test, the testing squares were thoroughly immersed in distilled water.e remaining procedure was the same as in the dry test.
Fastness to Sublimation.Sublimation fastness was measured with an iron tester (Yasuda no.138).e samples were prepared by stitching a piece of dyed polyester fabric between two pieces of undyed polyester, all of equal length, and then treated at 180 ∘ C and 210 ∘ C each for 1 min.
e structures of diazo dyes 3-8 were con�rmed by various spectroscopic techniques including IR, 1 H NMR and mass spectral data and their purities were con�rmed by elemental analyses.e IR spectra of 3-8 are characterized by the presence of absorption bands within the 3494-3332 cm −1 region corresponding to the stretching vibrations of the NH and/or OH groups.e absorption bands at the 1582-1490 cm −1 region are due to the symmetric stretching (3), ( 4), ( 6), ( 5), ( 7), vibrations of the azo group.e bands with the 1327-1299 and 896-884 cm −1 regions are due to the stretching vibrations of the P=O and P-O-C groups, respectively.e 1 H NMR, spectra showed a characteristic CH doublet signal in the 6.95-5.65 ppm region.ey also showed an exchangeable singlet signal that resonated in the 9.09-8.80ppm region due to the NH proton.e structures of diazo dyes 3-8 were con�rmed further by mass spectral data.e electron impact mass spectra indicated the presence of molecular ion peaks in all cases.Moreover, the elemental analyses of 3-8 were consistent with the suggested structures and con�rm the purities of the products (see Section 2 for details).

Dyeing of Polyester Fabrics and Dyeing
Properties.Most in�uences that can a�ect fastness are light, washing, heat, perspiration, and atmospheric pollution.Conditions of such tests are chosen to correspond closely to the treatments employed in manufacture and of ordinary use conditions [40].Results are given aer usual matching of the tested samples against standard reference (the greyscale) [40].e results obtained are shown in Table 1.e results revealed that azo dyes 3-8 have good fastness properties.

Conclusions
A set of six useful disperse dyes 3-8 were synthesised by azo coupling.e dyes were investigated for their dyeing characteristics on polyester and showed good washing, perspiration, rubbing, sublimation and light fastness.e remarkable degree of brightness aer washings is indicative of good penetration and the excellent affinity of these dyes for the fabric due to the accumulation of polar groups.