Solvent effect on the absorption spectra of some azo dyes with different head groups

Solvent effect on the absorption spectra of some azo dyes with different head groups

S. Hosseini, A. Ghanadzadeh, M. R. Yazdanbakhsh, F. Sayyadi

Department of chemistry, faculty of science, Guilan University, Rasht, Iran Hosseini_chemist2004@ yahoo.com

Introduction

Solvent effect plays an important role in photo-physical behavior of the absorption spectra of dyes. The solvent effect is closely related to the nature and degree of dye- solvent interactions. The solvent-dependent spectral shifts can arise from either non- specific or specific solute-solvent interaction. The photo-physical properties of the dyes are affected by the solvent nature as well as plority.

In the present work we investigated the effect of the isotropic and anisotropic solvations on the spectral behavior of some aromatic azo dyes. Aromatic azo dyes are the most widely used class of coloring materials due to their massive application in various fields of science and technology. A large amount of investigation has been carried out in recent years on the synthesis and spectroscopic properties of this group of dyes. The photo-physical and photo-chemical properties of this class of dyes make them suitable as optical sensors and advanced materials.

Key words: Azo dyes, solute-solvent interaction, Kamelt -Taft parameters

Experimental

All azo dyes (Fig.1) was synthesized and purified in our lab. All the solvents were purchased from Merck. The sample holder was a quartz spectrophotometer cell with a path length of (10mm). The absorption spectra in the visible region of the dyes dissolved.

The isotropic and anisotropic solvents were recorded by a Cary UV-Vis spectrophotometer (model 100).

CN N N NEt2

(a)

H N N NEt₂

(b)

Figure 1.Azodyes investigated

Result and discussion

Fig.2 (a-b) shows the absorption spectra of these azo dyes in different solvent. The polarity and hydrogen bonding properties of the isotropic solvents used in this work represented by the Kamlet-Taft parameters (a, þ, and n*). a is the scale of solvent hydrogen-bond donor ability. B is the scale of solvent hydrogen-bond acceptor and n* is a measure of solvent dipolarity/polarizability (see Table 1).

Table 1 Selected Kamlet-Taft’s Solvatochromic parameter

Solvent a þ v* ETN

DMSO 0.00 0.76 1.00 0.444

1,4 Dioxin 0.00 0.37 0.49 0.164

Toluene 0.00 0.11 0.49 0.099

Acetonitrile 0.19 0.46 0.66 0.460

Conclusion

We investigated some azo dyes in different isotropic solvents with different physical properties. It was observed that the maximum absorptions of the dyes were strongly affected by the solvent nature and properties.

absorption

(a) (a)

2 1.8

1.00E+00

9.00E-01

1.6 8.00E-01

1.4 7.00E-01

1.2 6.00E-01

1 0.8 0.6 0.4 0.2

0

350 400 450 500 550 600 650 700

λ(nm)

5.00E-01

4.00E-01

3.00E-01

2.00E-01

1.00E-01

0.00E+00

330 380 430 480 530 580

λ(nm )

absorption

References

1- A. jafari, A.Ghanadzadeh, H.Tajalli, M.Yeganeh, M.Moghadam, spectrochimica Acta (2006)

2- A. Ghanadzadeh, M. S. Zakerhamidi, H.Tajalli, j. Mol. Liq. 109/3 (2004) 143.

3- A. Ghanadzadeh, H.Tajalli, p.zirdel, j.shirdel, Spectrochimica Acta, 60A (2004) 2925

4- C. Reichardt, Solvents and Solvent Effects in Organic Chemistry Second Edition, VCH, 1988.