Synthesis and Characterization of New Azo Compounds Linked to 1,8-Naphthalimide as New Fluorescent Dispersed Dyes for Cotton Fibers

New Azo compounds containing of 1,8-naphthalimide moiety had been synthesized from 1,8-naphthalic anhydride by reaction with p-phenylenediamine or benzidine to give 1,8-naphthalimide derivatives [1 or 2], which converted into its diazonium salt derivatives that undergo to coupling reaction with different substituted phenol in alkaline media to produce azo compounds derivatives [3-6]. The prepared compounds had been characterized by measuring some of physical properties (melting point), FTIR, 1HNMR and 13CNMR. Also, absorption spectra (UV-Vis spectrophotometry), fluorescence spectra (Fluorescence spectrophotometry) and quantum yield of prepared azo dyes [3 - 6] had been studied in four different solvents of different polarities (EtOH, dioxane, CHCl3 and DMSO). Also, the photo stability of the dyes [3 - 6] was studied by exposing to the ultraviolet light at room temperature for three hours. Thermal stability of dyes (3 & 4) was studied by TGA / DTG. The prepared dyes [3 - 6] were used for the dyeing of raw cotton dyeing at high temperatures and studying their fastness properties such as washing fastness using standard soap (SDS) and rubbing fastness (wet and dry) under controlled conditions of pressure, speed and moisture.


INTRODUCTION
As azo compounds are colored because they have chromophore and auxochrome groups, easy to prepare, chemically stable and have a large diversity of colors available as compared to natural dyes. So, they are playing an important role for many years in industries of dyes and pigments. At least 3,000 azo dyes are synthesized in the past and used

EXPERIMENTAL INSTRUMENTS
All chemicals used are supplied from BDH, Merck, Fluka and Sigma Aldrich. Melting points had been measured using SMP3 melting point apparatus and left uncorrected. FTIR spectra had been studied on SHIMAZU FTIR-8400 spectrophotometer by using KBr disc in the (4000-600) cm -1 spectrum range. 1 HNMR and 13 CNMR spectra had been recorded on ECA 500 MHz by using TMS as reference and DMSO-d 6 as a solvent. Thermal analysis was obtained in a nitrogen atmosphere using a type TGA-50, Shimadzu. UV-VIS spectra were recorded by Shimadzuspectrophotometer. Fluorescence spectra were measured by RF-1501, Shimadzo. TLC was performed for all prepared compounds. 8 1,8-Naphthalic anhydride (5g, 0.025mol) was dissolved in (20ml) DMSO by heating. Then, (0.025mol) pphenylenediamine or benzidine were added to the reaction mixture and refluxed for (18-22 hrs). At last, the reaction mixture poured onto iced water and the solid precipitate was filtered and recrystallized from acetic acid. The compounds [1-2] physical properties listed in the Table 1.

Synthesis of N-(4-(sub-Aryldiazenyl)(phenyl or 1,1'biphenyl-4-yl))-1,8-naphthal-imide [3 -6] 9
Compound [1 or 2] (0.007 mol) was dissolved in (15 mL) of concentrated AcOH and (15 mL) of distilled water and the mixture was cooled in an ice bath until reach (0-5) °C. Then, NaNO 2 solution (0.47g, 0.007 mol) dissolved in (5mL) distilled water was added dropwise to the reaction mixture and stirred for (10 min.). Finally, the mixture was added carefully and very slowly to the solution of different substituted phenols (0.007 mol) dissolved in (60 mL) of (10%) NaOH at (0-5) °C and stirred for (30 min.). The colored product was filtered off and washed with cooled distilled water and dried by hot steam. The compounds [3 -6] physical properties are listed in Table 1. 10 x Cleaning of raw cotton: firstly, the raw was washed with hot water for half an hour and then washed with hot solution of 4% NaOH for another half an hour to clean, remove impurities and increase the pores size between the fibers. The bleaching process was done by hydrogen peroxide 30% for 10 minutes. Finally, the raw cotton left to dry on hot air steam. x Dyeing process: 0.3 g of a dye [3 -6] was dissolved in (10% NaOH in 15 mL Ethanol) and added to 40 mL of distilled water to form dyeing solution. Then, (10 gm) of cleaned cotton were immersed in dyeing solution and heated gradually until reach (60) °C and stirred for (10) min. Then, solution heated gradually until reach (90) °C and stirred for (30) min. Then, the dyed raw was dried by hot steam. x Fixation process: dyed raw was immersed in hot saturated solution of Alum and stirred for (30) min. Then, washed with hot tap water and dried by hot steam.  11 All details of FTIR Spectral data of compounds [1 & 2] are listed in Table 1. 1 H-NMR spectrum of compound [1] showed singlet signal of (-NH 2 ) protons at δ= (5.28) ppm and multi signals aromatic protons at δ= (6.95-8.56) ppm as the data listed in the Table 2. and shown in Figures 1. 13 CNMR spectrum data of compound [1] listed in the Table 3. and shown in Figures 2. 1 H-NMR spectrum of compound [2] showed singlet signal of (-NH 2 ) protons at δ= (5.31) ppm and multi signals aromatic protons at δ= (6.58-8.51) ppm as the data listed in the Table 2 and shown in Figure 3. 13 CNMR spectrum data of compound [2] listed in the Table 3. and shown in Figure 4. azo dyes [3][4][5][6] were prepared by coupling reactions of diazonium salts of compounds [1 & 2] with different substituted phenols. FTIR spectral data confirmed the formation of azo dyes [3-6 -3365) cm -1 and -3213) cm -1 due to occurring tautomerization phenomenon between OH and N=N groups as in Scheme 2. 12 Also, FTIR spectral data showed -1461) cm -1 2 ) stretching bands was disappeared from the spectrum. In addition, FTIR spectral data include appearance of (CH) aromatic bands at (3064-3053) cm -1 ,

Electronic spectra and solvents effect of azo dyes [3-6]
The electronic spectra of the azo dyes [3][4][5][6] were studied in four solvents of different polarities (Ethanol, Dioxane, DMSO and Chloroform) at a concentration of 1× 10 -5 mol. L -1 . In general, all azo dyes [3][4][5][6] in ethanol, DMSO and dioxane exhibited a two high intensity bands appeared in the region (270-333) nm were assigned to appeared in the region (345broad band was assigne -500) nm. 13 While in Chloroform, all azo dyes [3][4][5][6] were exhibited only one high intensity band appeared in region at (350-355) nm was assigned to omatic rings, C=O and N=N groups and other conjugated system because fluorescent compounds deviate from the Lambert-Bear law in some solvents due to the refraction process of emitted light that compensates for part of the absorbed light in the excitation process. The broad band at region (366-500) depend on molecule structure, the nature and polarity of the solvent used. 11 Table 4 and Figure 7 describes the maximum absorptions bands in different solvents of different polarities. . UV-Vis spectra of compounds [3][4][5][6] in different solvents

Fluorescent properties of azo dyes [3-6]
The photo physical properties of compounds [3][4][5][6] were investigated in different solvents (EtOH, dioxane, chloroform and DMSO) at a concentration of 1× 10 -5 mol. L -1 and room temperature. The irradiation was carried out for different fluorescent compounds measured by RF-1501, Shimadzo, Japan. Table 5 shows that the fluorescence is transitions, because such transitions exhibit shorter average lifetimes and because the deactivation prosses that compete with fluorescence are likely less to occur.
The most intense and the most useful fluorescence is found in compounds containing aromatic functional groups with low transition levels. Compounds containing azo dye structures and highly conjugation doublebond may also fluorescence, but the number of these is highly compared with the number in the aromatic systems.
Most unsubstituted aromatic hydrocarbons fluorescence in different solvents, the quantum efficiency usually increasing with the number of rings and their degree of condensation. On the other hand, substitution on the benzene ring causes shift in the wavelength of absorption maxima and changes in the fluorescence peaks. The quantum efficiency of fluorescence in most compounds of azo dyes decrease with increase in solvent viscosity and molecular weight such as: ethanol; dioxane and DMSO, this effect might be due to the decreased frequency of collisions and; the probability for deactivation by external conversion is very low. On the other hand, the fluorescence of azo dyes decreased by solvents containing heavy atoms i.e.: chloroform (containing chloride atom) as an example, due to increase in the rate of triplet formation, these leads to decrease of fluorescence and enhanced of phosphorescence.
In summary, the fluorescence i f =420-447 nm) because such transitions exhibit shorter average life times and the deactivation processes are less likely to occur, in addition to, it is found empirically that azo dyes as fluorescent molecules is particularly favored due to rigidity structures by the bridging i.e azo group. 14,15 The Relative fluorescent quantum yield of compounds [3][4][5][6] Table 5 and Figure 8 summarize the basic photo physical properties of azo dyes [3][4][5][6] in different solvents of different polarities

Fluorescent nature of azo dyes
From data listed in Table 5 all the prepared compounds exhibited a kind of fluorescent light when scanned at variable wavelength. All investigated newly prepared compounds show a closely related fluorescent emission at a closely scanned wavelength which indicate that the main fluorescent molecular structure is the same or closely related structure. Some of the prepared compounds when tested on exampled bench manual experiment using solid state laser at (405 nm, 445 nm and 532 nm) which covers the violet-blue-green with different output power, indicate clearly that compounds [3][4][5][6] give a clear intense fluorescent glow when especially irradiated with a 445 nm power intense laser diode. Figure 9 represents the suggested fluorescence mechanism of investigated compounds [3][4][5][6] when they irradiated by solid state laser at (405 nm, 445 nm and 532 nm).  [3][4][5][6] Compound [4] as in Figure 10 shows a kind of obtained fluorescent emission, this is regarded as a new -450 nm can irradiate this acceptor fluorophore molecule e.g. a conventional chemiluminescence reaction of luminal-H 2 O 2 -Co ++ which gives an max 425 nm can irradiate internally or externally this acceptor fluorophore molecule. This really mean that since fluorescent lifetime is generally larger than chemiluminescence light.
Compound [3] shows qualitative behavior as in Figure 10 a deep yellow approaching orange region of electromagnetic wave while compound [6] might most probably follow the same pattern for compound [3] but it looks that the main molecule is giving the white fluorescent emission which indicate in all tested molecule skeleton structure is mainly responsible for the main white emission while the faint yellow coloration that appear in Figure 10 shows a higher frequency of emission if compared to compound [3] as the spectrum goes like this , whitish-blue…white…green…yellow-green…yellow…orange.
Irradiation with 532 nm green solid-state laser didn't show any fluorescent emission because the energy is not enough to excite the prepared compounds.   13 The dyestuffs [3][4][5][6] were applied to cotton according to the high temperature exhaust dyeing procedure and yellow to violate shades were obtained. All dyed patterns had good levelling properties. The exhaustion levels were good to excellent, indicating high color yields.

Thermal stability of azo dyes
In general, thermal analysis refers to a range of techniques in which a sample property is continuously measured by the programming of the sample using a predetermined temperature profile. Thermal gravimetric analysis (TGA) and differential scanning calorimetry (DSC) are among the most common thermal analysis techniques. 17 Thermal analysis plays a major role in the study of stability and structure of azo dyes, there for the applicability of azo dyes for special applications and determining their thermal stability are very important. Heat resistance at high temperatures is one of the main requirements of dyes that used in high temperature processes such as printing, dyeing, photocopying and in areas of high technology such as optical devices and lasers. 18 The thermal properties of two derivatives of prepared azo dyes [3 & 5] were studied by TGA/DTG instrumentation. As the information that shown in Table 6 and Figures 11 and 12, All tested compounds showed almost similar thermal stability, so they have similar structures. The small differences in thermal stability between them is due to difference in substituted groups. In general, all tested azo compounds [3 & 5] have very high thermal stability.

Wash fastness of the synthesized dyes
The wash fastness of the synthesized dyes on cotton fabrics was measured according to (ISO 105 C06 C2S) with standard soap (SDC). 20 The results showed that all dyes have very good wash fastness. These results indicated that the presence of different substituent groups in the dye molecule was not a decisive factor in determining wash fastness performance. As it can be seen from Table 8, there is no difference in wash fastness between dyes with different substituents.

Rubbing fastness of the synthesized dyes
To assess rubbing fastness, dyes are fastened in the crock-meter, which causes a piece of standard cloth (cotton fabric) to rub against the colored sample under controlled conditions of pressure, speed and moisture (for wet rubbing fastness) according to (ISO 105 X12:1993). 20 The color transferred to the white cloth is visually compared with a grey scale. The results are given in Table 8. In all cases, the dyed fabrics exhibited high wet and dry rubbing fastnesses. The rating of fastness to rubbing for all dyes on cotton fabrics was in the range of (5-6). . cotton before and after washing process and dyeing process by some of azo dyes