Synthesis and Evaluation of Changes Induced by Solvent and Substituent in Electronic Absorption Spectra of New Azo Disperse Dyes Containig Barbiturate Ring

Hamidian, Hooshang; Zahedian, Najmeh; Ghazanfari, Dadkhoda; Fozooni, Samieh

doi:https://doi.org/10.1155/2013/276413

Journal of Spectroscopy

On this page

Abstract Introduction Experimental Results and Discussion Conclusions References Copyright Related Articles

Research Article | Open Access

Volume 2013 | Article ID 276413 | https://doi.org/10.1155/2013/276413

Synthesis and Evaluation of Changes Induced by Solvent and Substituent in Electronic Absorption Spectra of New Azo Disperse Dyes Containig Barbiturate Ring

Hooshang Hamidian,¹Najmeh Zahedian,²Dadkhoda Ghazanfari,²and Samieh Fozooni³

Academic Editor: Damien Boyer

Received29 Jun 2012

Revised14 Sept 2012

Accepted17 Sept 2012

Published01 Nov 2012

Abstract

Six azo disperse dyes were prepared by diazotizing 4-amino hippuric acid and coupled with barbituric acid and 2-thiobarbituric acid. Then, the products were reacted with aromatic aldehyde, sodium acetate, and acetic anhydride, and oxazolone derivatives were formed. Characterization of the dyes was carried out by using UV-Vis, FT-IR, ¹H NMR and ¹³C NMR, and mass spectroscopic techniques. The solvatochromic behavior of azo disperse dyes was evaluated in various solvents. The effects of substituents of aromatic aldehyde, barbiturate, and thiobarbiturate ring on the color of dyes were investigated.

1. Introduction

It is well known that azo compounds are the most widely class of industrial synthesized organic dyes due to their versatile application in various fields, such as dyeing textilefiber, biological-pharmacological activities, and advanced application in organic synthesis [1–3]. Many heterocyclic compounds are used extensively in disperse dye chemistry for textile or nontextile applications. These dyes are now marketed to produce a full range of dispersed dyestuffs without the use of colorants based on heteroaromatic diazo components. Most of the heterocyclic dyes are derived from the diazo components consisting of five-membered rings containing one or more nitrogen heteroatoms, with the rings being fused into another aromatic ring [4].

The azo dyes containing heterocyclic rings result in brighter and often deeper shades than their benzene analogs. On the other hand, they are very important in applications such as disperse dyes for polyester fibers, reprography, functional dye and nonlinear optical systems, photodynamic therapy, and lasers [5–10].

Barbituric acid (pyrimidine 2,4,6(1H,3H,5H)-trione) is widely used in the manufacturing of plastics, pigments, dyes, polymers, and the Vitamin B₂ (riboflavin) synthesis [11–14]. Barbiturates are a class of drugs that are utilized as anesthetics and sleeping agents and are used for the treatment of anxiety, epilepsy, and other psychiatric disorders and possess effects on the motor and sensory functions [15]. 2-Thiobarbituric acid is also used in the 2-thioxo-2,3-dihydro-4,6(1H,5H)-pyrimidinedione pharmacological and analytical fields [16, 17]. Therefore, several studies have been published on the synthesis and spectral properties of several azo barbituric acids so far [18–22]. We report the synthesis of a series of new azo dyes based on barbituric acid (Scheme 1).

The visible absorption spectra in various solvents of these dyes and effects of substituents of aromatic aldehyde, barbiturate, and thiobarbiturate ring on the color of dyes were also discussed.

2. Experimental

2.1. Materials and Apparatus

The chemicals used for the synthesis of the compounds were obtained from Merk Chemical Company and used without further purification.

The solvents used were of spectroscopic grade. IR spectra were determined using a Bruker tensor 27 Fourier Transform-infrared (FT-IR) spectrophotometer on a KBr disc. Nuclear magnetic resonance (¹H NMR) spectra were recorded on a Bruker-Spectrospin 400 Shimadzu QP-1100EX in dimethylsulphoxide (DMSO); chemical shifts were given in ppm. The microanalyses for C, H, and N were performed on perkin-elmer elemental analyzer. Ultraviolet-visible (UV-vis) absorption spectra were recorded on an Perkin Elmer spectrophotometer at the wavelength of maximum absorption in a range of solvents, that is, dimethylsulphoxide (DMSO), dimethylformamide (DMF), and ethanol, at same concentrations .

2.2. Synthesis and Characterization

2.2.1. Preparation of Azo Dyes

NaNO₂ (70 mg, 1 mmol) was added to concentrated HCl (3.0 mL) with external cooling. The suspension was heated to 60°C and again cooled to 0–5°C.

To a cooled basic solution of 4-Amino hippuric acid (1.94 g, 0.01 mol) in sodium carbonate (2.5%, 20 mL) the prepared diazonium solution was added drop-wise and the mixture was stirred for 50 min at reaction pH 7 (neutralized with sodium acetate). The precipitated product was filtered and purified by recrystallization from DMF/water .

(1) 2-[(4-{2-[2,4,6-trioxotetrahydro)-5(2H)-pyrimidinyliden]hydrazino} benzoyl) amino] acetic acid (3a). Yellow solid, yield 89%, m.p. 289–291°C; IR (KBr): 3423, 3264, 1750, 1710, 1654 cm⁻¹; ¹H NMR (ppm): 12.33 (broad, 2H, NH and OH), 11.23 (s, 2H, 2NH), 8.36 (d, 2H, Ar-H), 7.63 (d, 2H, Ar-H), 6.41 (t, 1H, NH), 3.93 (d, 2H, CH₂); ¹³C NMR (ppm): 172.7, 168.0, 163.0, 154.1, 142.1, 131.3, 123.5, 119.1, 115.1, 38.1; Anal. Calcd for C₁₃H₁₁N₅O₆: C, 46.85; H, 3.30; N, 21.02. Found: C, 47.01; H, 3.18; N, 20.95.

(2) 2-[(4-{2-[4,6-dioxo-2-thioxotetrahydro)-5(2H)-pyrimidinyliden]hydrazino} benzoyl) amino] acetic acid (3b). Orange solid, yield 81%, m.p. 306–308°C; IR (KBr): 3424, 3252, 1703, 1653 cm⁻¹; ¹H NMR (ppm): 12.38 (broad, 2H, NH and OH), 11.49 (s, 2H, 2NH), 8.42 (d, 2H, Ar-H), 7.67 (d, 2H, Ar-H), 6.41 (t, 1H, NH), 3.92 (d, 2H, CH₂); ¹³C NMR (ppm): 178.2, 171.9, 167.8, 154.3, 143.1, 131.9, 122.9, 122.1, 115.0, 38.1; Anal. Calcd for C₁₃H₁₁N₅O₅S: C, 44.70; H, 3.15; N, 20.06. Found: C, 44.48; H, 2.94; N, 19.89.

2.2.2. General Synthesis of Azo Dyes Containing Barbiturate Ring (4a–4f)

A general preparative procedure is described below for the preparation of all dyes. 2-[(4-{2-[2,4,6-trioxotetrahydro)-5(2H)-pyrimidinyliden]hydrazino} benzoyl) amino] acetic acid or 2-[(4-{2-[4,6-dioxo-2-thioxotetrahydro)-5(2H)-pyrimidinyliden]hydrazino} benzoyl) amino] acetic acid (3.35 g or 3.50 g, 0.01 mole) was refluxed in a mixture of sodium acetate (1.50 g), acetic anhydride (15 mL) and aromatic aldehydes (0.03 mole) for 6 h. The precipitated products were filtered off, washed with ethanol several times, dried, and recrystallized from dimethylformamide and water.

(1) 5-{2-[4-(4-benzyl-5-oxo-2,5-dihydro-1,3-oxazol-2-yl)-2,5-cyclohexadienyliden]hydrazono}-2,4,6(1H,3H,5H)-pyrimidinetrione (4a). Yellow solid, yield 32%, m.p. 326-327°C; IR (cm⁻¹): 3343 and 3265 (N–H), 1754 (C=O, oxazolone ring), 1710 and 1653 (C=O, barbiturate ring); ¹H NMR (ppm): 11.56 (s, 1H, NH), 11.33 (s, 1H, NH), 7.41–8.85 (m, 9H, Ar-H and CH=C), 4.15 (s, 2H, CH₂); ¹³C NMR (ppm): 171.8, 169.2, 166.1, 162.4, 160.2, 150.2, 144.1, 135.7, 131.4, 131.1, 130.1, 129.4, 126.9, 119.2, 116.5, 21.0; MS: m/z (%) (70 ev EL) 403 (M⁺), 257 (0.75), 211 (3), 105 (22), 57 (88), 43 (100). Anal. Calcd for C₂₀H₁₃N₅O₅: C, 59.55; H, 3.22; N, 17.40. Found: C, 59.71; H, 3.46; N, 17.05.

(2) 5-(2-{4-[4-(4-chlorobenzyl)-5-oxo-2,5-dihydro-1,3-oxazol-2-yl]-2,5-cyclohexadienyliden}hydrazono)-2,4,6(1H,3H,5H)-pyrimidinetrione (4b). Orange solid, yield 48%, m.p. 325–328°C; IR (cm⁻¹): 3343 and 3264 (N–H), 1753 (C=O, oxazolone ring), 1710 and 1652 (C=O, barbiturate ring); ¹H NMR (ppm): 11.57 (s, 1H, NH), 11.33 (s, 1H, NH), 7.63–8.85 (m, 8H, Ar-H and CH=C), 3.92 (s, 2H, CH₂); ¹³C NMR (ppm): 171.8, 169.1, 167.1, 162.4, 160.2, 150.2, 145.1, 131.5, 131.1, 129.4, 128.9, 128.3, 120.5, 117.1, 116.6, 21.5; MS: m/z (%) (70 ev EL) 437 (M⁺), 257 (29.6), 171 (26.97), 105 (90), 85 (64), 43 (100). Anal. Calcd for C₂₀H₁₂ClN₅O₅: C, 54.86; H, 2.74; N, 16.00. Found: C, 55.08; H, 2.94; N, 15.88.

(3) 5-(2-{4-[4-(4-fluorobenzyl)-5-oxo-2,5-dihydro-1,3-oxazol-2-yl]-2,5-cyclohexadienyliden}hydrazono)-2,4,6(1H,3H,5H)-pyrimidinetrione (4c). Yellow solid, yield 61%, m.p. 334-335°C; IR (cm⁻¹): 3342 and 3265 (N–H), 1753 (C=O, oxazolone ring), 1710 and 1655 (C=O, barbiturate ring); ¹H NMR (ppm): 11.55 (s, 1H, NH), 11.33 (s, 1H, NH), 7.24–8.85 (m, 8H, Ar-H and CH=C), 3.91 (s, 2H, CH₂); ¹³C NMR (ppm): 171.8, 169.1, 166.1, 162.5, 160.2, 150.2, 144.1, 132.2, 131.5, 131.1, 130.2, 129.4, 129.3, 119.3, 116.1, 21.0; MS: m/z (%) (70 ev EL) 421 (M⁺), 393 (1.66), 313 (14.58), 247 (3.33), 135 (80), 109 (35.42), 57 (91.66), 43 (100). Anal. Calcd for C₂₀H₁₁₂ FN₅O₅: C, 57.01; H, 2.85; N, 16.63. Found: C, 56.79; H, 3.03; N, 16.47.

(4) 5-(2-{4-[5-oxo-4-[1-phenylmethylidene]-1,3-oxazol-2(5H)-yl]phenyl}hydrazono)-2-thioxodihydro-4,6(1H,5H)-pyrimidinedione (4d). Orange solid, yield 73%, m.p. 322–325°C; IR (cm⁻¹): 3316 and 3262 (N–H), 1792 (C=O, oxazolone ring), 1689 (C=O, thiobarbiturate ring); ¹H NMR (ppm): 14.2 (s, 1H, N–H), 12.36 (s, 1H, NH pyrimidine), 12.47 (s, 1H, NH pyrimidine), 7.43–8.9 (m, 10H, Ar-H, CH=C); ¹³C NMR (ppm): 178.1, 171.5, 169.3, 166.1, 163.5, 161.1, 159.0, 144.0, 135.3, 131.5, 130.9, 126.9, 120.2, 117.1, 116.4, 115.3; MS: m/z (%) (70 ev EL) 419 (M⁺), 211 (4.16), 105 (91.66), 77 (68.3), 43 (100). Anal. Calcd for C₂₀H₁₃N₅O₄S: C, 57.28; H, 3.12; N, 16.71. Found: C, 57.41; H, 2.97; N, 16.58.

(5) 5-(2-{4-[4-[1-(4-chlorophenyl)methylidene]-5-oxo-1,3-oxazol-2(5H)-yl]phenyl}hydrazono)-2-thioxodihydro-4,6(1H,5H)-pyrimidinedione (4e). Dark red solid, yield 40%, m.p. 335-336°C; IR (cm⁻¹): 3342 and 3246 (N–H), 1792 (C=O, oxazolone ring), 1688 (C=O, thiobarbiturate ring); ¹H NMR (ppm): 14.14 (s, 1H, N–H), 12.50 (s, 1H, NH pyrimidine), 12.47 (s, 1H, NH pyrimidine), 7.51–8.50 (m, 9H, Ar-H, CH=C); ¹³C NMR (ppm): 178.0, 171.8, 169.1, 166.1, 162.4, 160.2, 158.6, 144.9, 134.8, 131.4, 131.1, 129.4, 119.2, 117.1, 116.6, 114.1; MS: m/z (%) (70 ev EL) 435 (M⁺), 297 (4.68), 271 (3.57), 158 (62.5), 139 (91.5), 111 (32.18), 43 (100). Anal. Calcd for C₂₀H₁₂ClN₅O₄S: C, 52.92; H, 2.65; N, 15.44. Found: C, 53.03; H, 2.69; N, 15.28.

(6) 5-(2-{4-[4-[1-(4-fluorophenyl)methylidene]-5-oxo-1,3-oxazol-2(5H)-yl]phenyl}hydrazono)-2-thioxodihydro-4,6(1H,5H)-pyrimidinedione (4f). Orange solid, yield 67%, m.p. 320–322°C; IR (cm⁻¹): 3323 and 3260 (N–H), 1791 (C=O, oxazolone ring), 1688 (C=O, thiobarbiturate ring); ¹H NMR (ppm): 14.2 (s, 1H, N–H), 12.63 (s, 1H, NH pyrimidine), 12.46 (s, 1H, NH pyrimidine), 7.23–8.85 (m, 9H, Ar-H and CH=C); ¹³C NMR (ppm): 178.1, 171.7, 169.1, 166.1, 164.3, 160.2, 158.7, 145.1, 131.5, 131.1, 129.4, 128.3, 120.4, 119.6, 117.1, 115.9; MS: m/z (%) (70 ev EL) 347 (M⁺), 393 (93.8), 378 (3.5), 336 (15.5), 296 (59.5), 280 (31.2), 135 (9.5), 43 (100). Anal. Calcd for C₂₀H₁₂FN₅O₄S: C, 54.92; H, 2.75; N, 16.02. Found: C, 55.10; H, 2.64; N, 15.91.

3. Results and Discussion

2-[(4-{2-[2,4,6-trioxotetrahydro)-5(2H)-pyrimidinyliden]hydrazino} benzoyl) amino] acetic acid (3a) and 2-[(4-{2-[4,6-dioxo-2-thioxotetrahydro)-5(2H)-pyrimidinyliden]hydrazino} benzoyl) amino] acetic acid (3b) were prepared by diazotization of 4-amino hippuric acid (1) in nitrosyl hydrochloric acid followed by coupling with barbituric acid and 2-thiobarbituric acid. Then oxazolone azo dyes (4a–4f) were synthesized by classical Erlenmeyer reaction, involving condensation of azo dye products with corresponding aldehydes in presence of acetic anhydride and sodium acetate under refluxing condition (Scheme 2).

3.1. The UV-Visible Spectra and Solvatochromic Studies of New Dyes

In order to study of solvent effects on spectral features of the dyes, we recorded their absorption spectra in three solvents with different polarity at a concentration 10⁻⁶ M in the range of 250–700 nm (Table 1), in which the solvents are arranged in the order of decreasing polarity. Also, refractive index , dielectric constant , and the solvatochromic parameters (, α, and β) were taken from the literature [23–25]. As shown in Table 1, the electronic absorption spectra of all studied compounds in different solvents exhibit maximum absorption band in the range of 390.51–425.12 nm which can be attributed to and/or electronic transitions of azo chromophores.

The dyes displayed a single main absorption peak without a shoulder in all solvents. The of all compounds were found to show a weak solvent dependency, denoting bathochromic effect (positive solvatochromism) in more polar solvents. The spectral shift is mainly due to solute-solvent interactions that give rise to a better stabilization of the orbital as compared to the orbital in polar solvents (Figure 1).

(a)

(b)

(c)

(d)

(e)

(f)

3.2. Substituent Effects

The absorption spectra of these azo dyes 4a–4f were recorded in various solvents at the concentration of 10⁻⁶, M, and the results are given in Table 1. We found that the electronic absorption of these azo dyes indicated a regular variation with the polarity of solvents, which did not change significantly. These dyes, apparently, did not exhibit a strong solvent dependence. The maximum absorption of these dyes shifted in the order: DMSO > DMF > Ethanol. The spectral shifts of dyes 4a–4f in various solvents are shown in Figure 1. The maximum absorption of dye 4a showed bathochromic shift in DMSO and DMF, with respect to the maximum absorption in ethanol (e.g., is 394.48 nm in DMSO, 393.04 nm in DMF, and 392.34 nm in ethanol). The same trends of absorption shifts in various solvents were observed for the entire series of dyes 4a–4f, as shown in Table 1. The substituent effects of the heterocyclic azo dyes 4a–4f were evaluated. The spectral shifts of dyes 4a–4f in solvents at a concentration of 10⁻⁶ are given in Table 2. We found that the dyes 4a–4f did not exhibit a strong solvent dependence to substituent effects on the phenyl ring but exhibited a strong solvent dependence to thiobarbiturate or barbiturate ring. Therefore dyes 4d–4f showed bathochromic shift in comparison with dyes a–c in all studied solvents as shown in Table 2.

4. Conclusions

In summary, we have synthesized six disperse azo dyes containing barbiturate and thiobarbiturate ring (4a–4f) in this paper. The structures of prepared dyes were confirmed by ¹H NMR, ¹³C NMR, mass spectroscopy, FT-IR, and UV-vis spectra. The electronic absorption spectra of disperse dyes were recorded in solvents with different physical-chemical properties. A large bathochromic shift (positive solvatochromism) of these compounds was observed upon increasing the solvent polarity and the dyes 4a–4f did not exhibit a strong solvent dependence to substituent effects on the phenyl ring but exhibited a strong solvent dependence to thiobarbiturate or barbiturate ring.

Acknowledgment

The authors are very grateful to Azad University of Kerman for providing financial support of this study.

References

A. A. Fadda, H. A. Etman, F. A. Amer, M. Barghout, and K. S. Mohamed, “Azo disperse dyes for synthetic fibres. I: 2-methyl- and 2-phenylquinazolone derivatives,” Journal of Chemical Technology and Biotechnology, vol. 61, no. 4, pp. 343–349, 1994.
View at: Publisher Site | Google Scholar
M. M. M. Raposo, A. M. R. C. Sousa, A. M. C. Fonseca, and G. Kirsch, “Thienylpyrrole azo dyes: synthesis, solvatochromic and electrochemical properties,” Tetrahedron, vol. 61, no. 34, pp. 8249–8256, 2005.
View at: Publisher Site | Google Scholar
M. R. Yazdanbakhsh, A. Ghanadzadeh, and E. Moradi, “Synthesis of some new azo dyes derived from 4-hydroxy coumarin and spectrometric determination of their acidic dissociation constants,” Journal of Molecular Liquids, vol. 136, no. 1-2, pp. 165–168, 2007.
View at: Publisher Site | Google Scholar
M. A. Weaver and L. Shuttleworth, “Heterocyclic diazo components,” Dyes and Pigments, vol. 3, no. 2-3, pp. 81–121, 1982.
View at: Google Scholar
L. C. Abbott, S. N. Batchelor, J. Oakes et al., “Experimental and computational studies of structure and bonding in parent and reduced forms of the azo dye orange II,” Journal of Physical Chemistry A, vol. 109, no. 12, pp. 2894–2905, 2005.
View at: Publisher Site | Google Scholar
M. M. M. Raposo, M. C. R. Castro, A. M. C. Fonseca, P. Schellenberg, and M. Belsley, “Design, synthesis, and characterization of the electrochemical, nonlinear optical properties, and theoretical studies of novel thienylpyrrole azo dyes bearing benzothiazole acceptor groups,” Tetrahedron, vol. 67, no. 29, pp. 5189–5198, 2011.
View at: Publisher Site | Google Scholar
P. C. Tsai and I. J. Wang, “A facile synthesis of some new pyrazolo[1,5-a]pyrimidine heterocyclic disazo dyes and an evaluation of their solvatochromic behaviour,” Dyes and Pigments, vol. 74, no. 3, pp. 578–584, 2007.
View at: Publisher Site | Google Scholar
H. R. Maradiya and V. S. Patel, “Synthesis and dyeing performance of some novel heterocyclic azo disperse dyes,” Journal of the Brazilian Chemical Society, vol. 12, no. 6, pp. 710–714, 2001.
View at: Google Scholar
A. C. Razus, L. Birzan, N. M. Surugiu, A. C. Corbu, and F. Chiraleu, “Syntheses of azulen-1-yl-benzothiazol-2-yl diazenes,” Dyes and Pigments, vol. 74, no. 1, pp. 26–33, 2007.
View at: Publisher Site | Google Scholar
J. A. Mielczarski, G. M. Atenas, and E. Mielczarski, “Role of iron surface oxidation layers in decomposition of azo-dye water pollutants in weak acidic solutions,” Applied Catalysis B, vol. 56, no. 4, pp. 289–303, 2005.
View at: Publisher Site | Google Scholar
D. Thetford, A. P. Chorlton, and J. Hardman, “Synthesis and properties of some polycyclic barbiturate pigments,” Dyes and Pigments, vol. 59, no. 2, pp. 185–191, 2003.
View at: Publisher Site | Google Scholar
A. V. Kulinich, N. A. Derevyanko, and A. A. Ishchenko, “Synthesis, structure, and solvatochromism of merocyanine dyes based on barbituric acid,” Russian Journal of General Chemistry, vol. 76, no. 9, pp. 1441–1457, 2006.
View at: Publisher Site | Google Scholar
A. Slączka and J. Lubczak, “Hydroxyalkylation of barbituric acid. IL synthesis of polyetherols with pyrimidine ring,” Journal of Applied Polymer Science, vol. 106, no. 6, pp. 4067–4074, 2007.
View at: Publisher Site | Google Scholar
M. Tishler, K. Pfister, R. D. Babson, K. Ladenburg, and A. J. Fleming, “The reaction between o-aminoazo compounds and barbituric acid. A new synthesis of riboflavin,” Journal of the American Chemical Society, vol. 69, no. 6, pp. 1487–1492, 1947.
View at: Google Scholar
J. L. Fillaut, J. Andriès, J. Perruchon et al., “Alkynyl ruthenium colorimetric sensors: optimizing the selectivity toward fluoride anion,” Inorganic Chemistry, vol. 46, no. 15, pp. 5922–5932, 2007.
View at: Publisher Site | Google Scholar
A. Dhasmana, J. P. Barthwal, B. R. Pandey, B. Ali, K. P. Bhargava, and S. S. Parmar, “Anticonvulsant activity and succinate dehydrogenase inhibitory property of new substituted thiobarbiturates,” Journal of Heterocyclic Chemistry, vol. 18, no. 3, pp. 635–637, 1981.
View at: Google Scholar
B. Morelli, “2-Thiobarbituric acid as a reagent for the determination of bismuth(III) by normal and derivative spectrophotometry,” The Analyst, vol. 107, no. 1272, pp. 282–287, 1982.
View at: Google Scholar
R. Gup, E. Giziroglu, and B. Kirkan, “Synthesis and spectroscopic properties of new azo-dyes and azo-metal complexes derived from barbituric acid and aminoquinoline,” Dyes and Pigments, vol. 73, no. 1, pp. 40–46, 2007.
View at: Publisher Site | Google Scholar
M. S. Masoud, E. A. Khalil, A. M. Hindawy, A. E. Ali, and E. F. Mohamed, “Spectroscopic studies on some azo compounds and their cobalt, copper and nickel complexes,” Spectrochimica Acta A, vol. 60, no. 12, pp. 2807–2817, 2004.
View at: Publisher Site | Google Scholar
A. H. Amrallah, N. A. Abdalla, and E. Y. El-Haty, “Mixed ligand complexes of benzimidazole and pyrimidine hydroxy azo dyes with some transition metals and glycine, DL-alanine or DL-leucine,” Talanta, vol. 46, no. 4, pp. 491–500, 1998.
View at: Publisher Site | Google Scholar
M. S. Masoud, S. A. Abou El-Enein, M. E. Ayad, and A. S. Goher, “Spectral and magnetic properties of phenylazo-6-aminouracil complexes,” Spectrochimica Acta A, vol. 60, no. 1-2, pp. 77–87, 2004.
View at: Publisher Site | Google Scholar
M. S. Masoud, G. B. Mohamed, Y. H. Abdul-Razek, A. E. Ali, and F. N. Khairy, “Studies on some thiazolylazo compounds and their cobalt, nickel, and copper complexes,” Spectroscopy Letters, vol. 35, no. 3, pp. 377–413, 2002.
View at: Publisher Site | Google Scholar
C. Reichardt, Solvents and Solvent Effects in Organic Chemistry, Wiley-VCH, Weinheim, Germany, 2003.
M. J. Kamlet, J. L. M. Abboud, M. H. Abraham, and R. W. Taft, “Linear solvation energy relationships. 23. A comprehensive collection of the solvatochromic parameters, π*, α, and β, and some methods for simplifying the generalized solvatochromic equation,” Journal of Organic Chemistry, vol. 48, no. 17, pp. 2877–2887, 1983.
View at: Google Scholar
D. R. Lide, Handbook of Chemistry and Physics, CRC Press, Boca Raton, Fla, USA, 76th edition, 1995.

Copyright

Copyright © 2013 Hooshang Hamidian et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

PDF Download Citation

Download other formats

Order printed copies

Views

2341

Downloads

2043

Citations