Preparation, analytical Studies and application of a New Azodye Derived from Pharmaceutical Materials (Procaine Hydrochloride & Salicylic acid)

Procaine hydrochloride was used as an aromatic amine, and salicylic acid (5-[2-(diethylamino)-4-benzoateazo]-2-hydroxybenzoic acid) was used to make a new azodye derived from pharmaceutical materials ( PS ).C.H.N., H1-NMR, I.R., and visible spectroscopic techniques have also been used to characterize dye. At different pH values ( 2 - 12 ), the electronic spectra of this azo dye was investigated in terms of acid-base properties, which included defining isobestic points and determining protonation and ionization constants. The effect of different polarities of solvents on the electronic spectra was the subject of another study. The dye has been used in a variety of applications, including as an indicator for strong acid with strong base and for nitrite determination.


Introduction
Azo compounds are commonly used as dyes because of their numerous uses in fields such as synthetic fabrics, material coloring, biomedical research, and organic synthesis [1][2].Azo compounds are often used as markers of biomedical research.Furthermore, azo dyes have been documented to have a wide range of biological applications, including antineoplastics, antidiabetics, antiseptics, antiinflammatory, and other chemotherapeutic agents [3][4][5][6].Since most azo dyes have acid-base properties and have fixed isobestic points (which reflect the number of equilibriums in such an azo dye), they are used as acid-base indicators [7] and some can also be used as metallochromicindicators.Azo compounds are commonly used as dyes because of their numerous uses in fields such as synthetic fabrics, material coloring, biomedical research, and organic synthesis [8][9][10][11][12].Azo compounds are often used as markers of biomedical research.Furthermore, azo dyes have been documented to have a wide range of biological applications, including antineoplastics, antidiabetics, antiseptics, antiinflammatory, and other chemotherapeutic agents [13][14][15][16][17].Since most azo dyes have acid-base properties and have fixed isobestic points (which reflect the number of equilibriums in such an azo dye), they are used as acid-base indicators [18] and some can also be used as metallochromic indicators. To the spectrophotometric determination of nitrite, the azo dye was used by forming daizonium salt. Such as p-nitroaniline in acidic medium with frusemide at λmax.680nm [19], and also the azo dye formed form coupling of 2-thioparbutric acid with diazonium salt of p-aminobenzoic acid at λmax.420nm [20] and the diazonium salt of luminal with 4-hydroxycumarine [21].

Experimental
The reagents and solvents were all of the reagent-grade variety. TLC was used to monitor the reaction's progress on a silica gel-coated plate, and spots were visible under UV light. The FT.IR- shimadzu was used to record infrared spectra (in KBr pellets). Melting points were measured using a melting point apparatus, element analysis (C.H.N.) was performed using a Perkin element 2400 element analyzer, and UV/V absorption spectra were reported using a Perkin Elmer Lampda EZ 210 UV/V Spectrophotometer. PH-Meter was used to take the readings (H. Jurgons Co. Bremen,L.Puls Munchen15).

Preparation of azodye
The azo dyes reagentsPS were made by dissolving 0.004 mole of procaine hydrochloride in 1.4 ml concentrated HCl, 20 ml distilled water, and then adding a drop-by-drop solution of ( 0.304 g sodium nitrite in 20 ml distilled water ) to form diazonium salt at a temperature of less than 5 o C. To the above diazonium salt, add an alkaline solution containing 0.004 mole of salicylic acid in 1.2 percent v/w NaOH.Adding dilute HCl to the prepared dye to convert it from sodium salt to hydrogen type.Recrystallization from metanol was used to purify the dye [23].  Mix equal volumes of cold P and N solutions at 5° C, then add an equal volume of S solution and calculate the absorbance in the 320-600 nm range.

Results and discussion
The compounds were prepared in good yield. The compounds are stable in air and light. Elemental Analysis data and physical properties of compounds are summarized in table (1) 3.1. Infrared radiation Table 1 shows the spectral data of azo dye PS .The (N-H) and (O-H) bands in the IR spectrum of free ligand are responsible for the medium band about 3234 cm -1 . There is a high intensity band in the range of 1300-1270cm-1 due to (C=N) in the novel azo dye. In the azo spectrum, the azo (-N=N-) group can be seen at 1427.32s cm-1, the bands at 1664 cm-1 for (C=O), the bands around 1309 cm-1 observed due to C-N stretching . Figure.

Spectra of 1 H-NMR
In deuterated dimethyl sulfoxide solutions with tetramethylsaline as an internal norm, 1H-NMR spectra of the prepared azo dye PS were obtained. The DMSO solvent caused a peak at 2.5 ppm in the spectra. Figures (3) show the 1H NMR data.    The spectrum had three bands, the first of which was at 360 nm and was in the pH range (3-8) due to dye protonation.In the pH range, the second and third bands (440 and 460 nm,) of high intensity (8)(9)(10)(11)(12).At 390 nm, the spectrum also revealed an isobestic point (a wavelength with constant absorbance despite changes in pH value medium).  (Table 2). From Absorbance-PH curve and by the aid of half-height method [ 25 ] , the PK values were obtained by this relation : PK = PH ( at A1/2 ) where ; A1/2 = ( AL+ Amin. ) / 2 And AL and Amin are limiting and minimum absorbances respectively.    Figure 7 depicts the spectrum of the azo dye PS (concentration 4x10-5 M) in various polarity solvents (Acetone , chloroform , ether , DMF , DMSO, ethyl acetate , water , ethanol , methanol and 1,4dioxane ).In all solvents, the dye has only one band, as shown in Fig.7. When polar solvents (ether, methanol, chloroform, and ethanol) are compared to non-polar solvents (benzene) at 350 nm, there is a small blue change at 340 nm. The broad red shift at 380 nm in comparison to solvents (DMF and DMSO) was due to hydrogen bonding between dye molecules (solute) and solvent molecules, as shown in Fig.8. The dielectric function of solvents and the maximum wavelength of dye PS in various solvents are shown in Table 3.   Figure. 8 ) , the linearity of all solvents which means the dielectric constant that affected except for the DMF and DMSO gave deviation from the linearity because of hydrogen bonding between dye molecules ( solute ) and solvent molecules.     Where ε, a, S, R 2 , S.D. and DL are molar absorptivity coefficient, specific absorptive, Sandel sensitivity, standard deviation and detected limit respectively. Titration of strong acid (HCl) with strong base (NaOH) uses the azo dye as an acid-base indicator. The base was titrated spectrophotometrically with standard HCl using the new azo dye PS as an indicator (Fig. 12) after HCl and NaOH were standardized to be 0.0917 N and 0.0961 N, respectively. The relative error for obtaining the best PS concentration was discovered (Table 5).   Figure. (12) Revealed that the concen.of PS in the range of (0.00001-0.00003 M) The best concn. Was 0.00003M of PS, which resulted in more jumbling (that means more sensitivity) When the concn. Is greater than 0.00003, the titration fails due to minor dissuasions of dye PS at high concentrations.