Synthesis, characterization and determination of third-order optical nonlinearity by cw z-scan technique of novel thiobarbituric acid derivative dyes

Materials Letters 144 (2015) 131–134

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Synthesis, characterization and determination of third-order optical nonlinearity by cw z-scan technique of novel thiobarbituric acid derivative dyes M.A.N. Razvi a,n, Ahmed H. Bakry a, S.M. Afzal a,d, Salman A Khan b, Abdullah M. Asiri b,c a

Physics Department, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia Chemistry Department, Faculty of Science, King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia c Center of Excellence for Advanced Materials Research (CEAMR), King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia d Physics Department, Aligarh Muslim University, Aligarh 202002, India b

art ic l e i nf o

a b s t r a c t

Article history: Received 24 November 2014 Accepted 10 January 2015 Available online 19 January 2015

Donor acceptor chromophores were prepared by Knovenagel reaction of 1,3-diethyl-2-thiobarbituric acid with corresponding aldehydes in ethanol using pyridine as catalyst. The structures of newly synthesized compounds were evaluated by FT-IR, 1H NMR, 13C NMR, MS spectroscopy and purity of the compounds were confirmed by elemental analyses. The nonlinear refractive index n2 and nonlinear absorption coefficient β are measured for these dyes using the closed and open aperture z-scan technique with a cw He–Ne laser at 632.8 nm. These values are found to be high and linearly dependent on the concentration. & 2015 Elsevier B.V. All rights reserved.

Keywords: Optical materials and properties Organic Spectroscopy

1. Introduction There has been a demand for nonlinear optical media with large nonlinearities. Organic dyes have been found to be suitable for these applications [1–6]. Knovenagel reaction is one of the most important and easiest reactions for the formation of donor acceptor chromophores followed by a dehydration reaction to a carbonyl group by the nucleophilic addition of an active hydrogen molecule [7]. These chromophores are being used in optical limiting [8], optical switching [9], electronic devices [10], polymer coating [11], and nonlinear optical media [12]. In this paper we describe the synthesis of two such chromophores. We also report their characterization by optical and mass spectrometry techniques. The z-scan technique [13] is employed to study the nonlinear refractive index and nonlinear absorption coefficient of T1 and T2 dyes. Z-scan measurements are carried out at four different concentrations. The nonlinear refractive index and absorption coefficient are measured for these dyes. The thirdorder susceptibility is estimated from these measurements.

2. Experimental Chemicals and reagents: Thiobarbituric acid, 9-ethyl-9H-carbazole-3-carbaldehyde and 3,4-dimethoxy benzaldehhde were acqun

Corresponding author. Tel.: +966 12 6952000x64286; fax: +966 12 6951106. E-mail address: [email protected] (M.A.N. Razvi).

http://dx.doi.org/10.1016/j.matlet.2015.01.036 0167-577X/& 2015 Elsevier B.V. All rights reserved.

ired from Acros Organic. All solvents and reagents (A.R.) were acquired commercially and utilized with no additional purification, excluding dimethylformamide (DMF), ethanol and methanol. Apparatus: Thomas Hoover capillary melting apparatus was used to record the melting points of the synthesized compounds without any correction. Nicolet Magna 520 FT-IR spectrometer was utilized to record the FT-IR spectra. Brucker DPX 600 MHz spectrometer with tetramethyl silane as internal standard at room temperature was used to perform the 1H NMR and 13C NMR experiments in CDCl3. Shimadzu UV-160A spectrophotometer was utilized to gain the UV–vis electronic absorption data and by using a 10 mm quartz cell absorption spectra were collected. By using Shimadzu RF 5300 spectrofluorphotometer having a quartz cell of rectangular shape with dimensions 0.2 cm
1 cm for minimizing the reabsorption. General procedure for the synthesis of thiobarbituric acid derivatives: A mixture of the appropriate aldehyde (0.011 mol) and 1,3diethyl-2-thiobarbituric acid (0.011 mol) in absolute ethanol (25 mL) of few drop of pyridine was refluxed at 80 1C for with continuous stirring. The reactions were monitored through TLC using solvent system ethyl acetate: benzene (2:8), when the reaction was found to be complete, then reaction mixture was cooled in an ice bath and the product thus formed was filtered washed with water and recrystallized by distilled ethanol and chloroform (Fig. 1). 1,3-Diethyl-5-(9-ethyl-9 H-carbazol-3-ylmethylene)-2-thioxo-dihydro-pyrimidine-4,6-dione: (T1): Yellow color solid (Chloroform); Yield: 96.91%; m.p. 220 1C; EI-MS m/z (rel. int. %): 407 (78) [Mþ1] þ ; IR

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CHO O N N N

T1

3h

O

N

S

S EtOH N

N Pyridine

O

O

CHO O N

O

S

O

N O

2h

O

O

T2

6

Absorbance

5

T1

4 3 2

T2

1 0 200

300

400

500

600

700

Wavelength [nm] Fig. 1. Synthesis of chromophores (T1 and T2) and their absorption spectrum.

(KBr) vmax cm  1; 3104 (C–H aromatic), 2974 (C–H aliphatic), 1694 (CQO), 1625 (CQC), 1195 (CQS), 1163 (C–N); 1H NMR (600 MHz, CDCl3)δ: 8.20 (d, H1, J¼7.8 Hz), 8.57 (d, H2, J¼7.2 Hz), 8.77 (s, H3), 7.47 (d, H4, J¼9.6 Hz), 7.55 (dd, H5, J¼7.2 Hz), 7.36 (dd, H6, J¼7.2 Hz), 7.47 (d, H7, J¼9.6 Hz), 8.42 (s, H8), 4.65 (t, CH3–CH2–N, J¼7.2 Hz), 1.47 (q, CH3–CH2–N, J¼5.4 Hz); 13 C NMR (CDCl3) δ: 191.88, 178.97, 161.88, 159.13, 143.77, 140.64, 134.43, 130.48, 128.44, 126.72, 124.30, 121.08, 120.84, 113.57, 109.32, 108.64, 77.23, 58.50, 44,17, 38.07, 18.44, 13.91, 12.54; Anal. calc. for C23H23N3O2S: C, 68.12, H, 5.72, N, 10.36; Found: C, 68.06, H, 5.65, N, 10.24. 5-(3,4-Dimethoxy-benzylidene)-1,3-diethyl-2-thioxo-dihydropyrimidine-4,6-dione: (T2): Orange color solid (Chloroform); Yield: 76.91%; m.p. 186 1C; EI-MS m/z (rel. int. %): 349 (62) [Mþ 1] þ .; IR (KBr) vmax cm  1: 2974 (C–H aromatic), 2926 (C–H aliphatic), 1687 (CQO), 1656 (CQC), 1242 (C–O), 1173 (CQS), 1157 (C–N); 1H – NMR (CDCl3) δ: 8.34 (d, H1, J¼ 9.0 Hz), 7.85 (d, H2, J¼ 6.6 Hz), 7.26 (s, H3), 7.49 (s, H4), 4.60 (t, CH3–CH2–N, J¼ 7.2 Hz), 1.33 (q, CH3– CH2–N, J ¼ 6.6 Hz); 3.98 (s, 2
CH3–O); 13C NMR (CDCl3) δ: 178.78, 162.23, 159.82, 159.41, 154.55, 145.18, 139.78, 121.73, 111.36, 110.96, 109.93, 77.26, 43.97, 43.42, 40.18, 18.44, 12.61; Anal. calc. for C17H20N2O4S: C, 58.60, H, 5.79, N, 8.04; Found: C, 58.54, H, 5.72, N, 7.96. Nonlinear measurements: A solution of concentration 1 mM of the dye was prepared by dissolving it in chloroform. The sample

Fig. 2. Schematic of the experimental setup for the z-scan measurements. Aperture is fully open for the open-aperture scans.

was placed in a 1 mm quartz cuvette for the z-scan measurements. A schematic of the experimental setup is shown in Fig. 2. A 15 mW cw He–Ne laser operating at 632.8 nm was used for these measurements. A lens (L1) of focal length 5 cm is used to focus the laser beam at the sample and an iris aperture (S¼0.077) is placed far away from the focus for the closed aperture scans. Another lens (L2) is used behind the aperture to focus the transmitted light onto a 5 mm2 area avalanche photodiode; and a beam attenuator is used to ensure linearity of the photodiode signal with light intensity. Open aperture measurements are done by opening the iris fully. The dye cell was moved on a computer controlled scanning stage with a step-size of 0.1 mm and the

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CLOSED APERTURE Z-SCAN OF DYE T2 1.3

-3

-2

-1

0

1

2

3

4

133

OPEN APERTURE Z-SCAN FOR DYE T2 1.3

1.2

1.2

1.1

1.1

1.0

1.0

0.9

0.9

0.8

0.8

Normalized Transmittance

Normalized Transmittance

1.04 1.02 1.00 0.98 0.96 0.94 0.92 0.90

0.7

0.88

0.7 -3

-2

-1

0

1

2

3

-10

4

-8

-6

-4

Z/ZR

-2

0

2

4

6

8

10

Z/ZR

Fig. 3. (a) Closed aperture z-scan for the dye T2 at concentrations 1 mM, 0.75 mM, 0.5 mM with cw He–Ne laser at 632.8 nm and 10 mW power. Dots are the experimental points and the solid lines are the theoretical fit. (b) Open aperture z-scan for the dye T2 at concentration 1 mM. Red line is the fit through the data points. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)

Table 1 Nonlinear optical parameters of the novel chromophores. Concentration (mM)

Dye T1 n2 (10

1 0.75 0.5 0.25

7

 0.424  0.307  0.242  0.136

Dye T2 2

cm /W)

β (10

3

 0.890  0.620  0.560  0.530

cm/W)

(3)

χ

(10

2.256 1.633 1.289 0.733

photodiode signal was digitized by an analog to digital converter and recorded on the computer. The z-scans shown are an average of three scans to reduce noise. Normalized transmittance of the dye was found by dividing averaged data with the solvent transmittance data recorded under the same conditions. Linear absorption of the sample is measured with a UV–visible spectrophotometer and the spectra are shown in Fig. 1(inset).

3. Results and discussion Chemistry: The synthesis of chromophore derivatives are straight forward and the compounds were isolated in good yield. The derivatives were synthesized by using the literature procedure [14]. The obtained compounds are stable in the solid state as well as in the solution. The structure of all the compounds presented in experimental section was established by comparing spectral data FT-IR, 1H NMR, 13C NMR, EI-MS spectra and purity of the compounds further confirmed by the elemental analysis. Assignments of select characteristic IR band positions provide significant indication for the formation of the chromophore derivatives. The compounds showed intense bands at 1625 and 1656 cm  1 due to v (CQC) stretch, which confirms the formation of donor accepter chromophores. Further confirmation was obtained from the 1H NMR spectra, which provide diagnostic tools for the positional elucidation of the protons. Assignments of the signals are based on the chemical shifts and intensity patterns. The aromatic protons of chromophore T1 and T2 are shown as s,d and dd in the range ppm for the compounds. A

6

esu)

n2 (10  7 cm2/W)

β (10  3 cm/W)

χ(3) (10  6 esu)

 1.571  1.536  1.366  1.121

1.667 1.587 1.326 1.008

8.326 8.140 7.238 5.939

Singlet due to QC–H proton in the compounds T1 and T2 was observed at δ 8.42 and 7.44 respectively. The appearance of singlet, doublet, and multiplets at δ 7.26–8.77 was due to aromatic protons in compounds T1 and T2. 13C NMR (CDCl3) spectra of chromophore were recorded in CDCl3 and spectral signals are in good agreement with the probable structures. Details of 13C –NMR spectra of all compounds are given in the experimental section. Finally characteristic peaks were observed in the mass spectra of compound T1 and T2 by the molecular ion peak. The mass spectrum of compounds T1 and T2 show a molecular ion peak (M þ ) m/z 407 and 349. All the compounds give similar fragmentation pattern. Determination of nonlinear properties: As the sample moves through the beam focus (z¼0), self-focusing or defocusing modifies the detected beam intensity. For an open aperture z-scan pinhole is removed and transmitted beam falls on the detector without any limitation. As seen in Fig. 1, the linear absorption at 633 nm is negligible and thus the response of the dye at the laser wavelength is purely nonlinear far away from resonance. The z-scans for the closed and open aperture for the two chromophores T1 and T2 are shown in Fig. 3. The solid line in Fig. 3(a) and (b) is a theoretical fit for the functions [15]. A distinct negative nonlinearity has been observed for the samples. This is attributed to thermally induced variation in refractive index of the medium. The dyes T1 and T2 exhibited large nonlinear refractive index n2 of the order of  0.42
10  7 and  1.5
10  7 cm2/W respectively. Similarly the nonlinear absorption coefficient β also has large values of the order of  9
10  4 and þ1.6
10  3. One must note the opposite sign of the nonlinear absorption coefficient of the two dyes. The measured values of the

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nonlinear refractive index and the nonlinear absorption coefficient calculated from the standard formulae are shown in Table 1, along with the third order nonlinear susceptibility χ(3) calculated based on the standard equations [16,17].

4. Conclusions We have synthesized two new thiobarbituric acid derivatives dyes by the Knovenagel condensation reaction method. Structures of newly synthesized compounds were evaluated by FT-IR, 1H NMR, 13 C NMR, MS spectroscopy and elemental analyses. Nonlinear refractive index and nonlinear absorption coefficients of these novel dyes were studied by the z-scan technique with a continuous wave He–Ne laser at 633 nm. The values obtained are reasonably high among the category of such class of molecules exhibiting high nonlinear properties. This may be of use in developing photonic devices like optical limiters for eye and equipment safety.

Acknowledgment This Project was funded by the Saudi Basic Industries Corporation (SABIC), and the Deanship of Scientific Research (DSR), King Abdulaziz University, Jeddah, under Grant no. MS/15/331/1434.

The authors, therefore, acknowledge with thanks SABIC and DSR technical and financial support. References [1] Asiri AM, Khan SA. Mater Lett 2011;65:1749. [2] Asiri AM, Khan SA, Hallag SI. J New Mater Electron Syst 2011;14:251. [3] Asiri AM, Khan SA, Al-Amodi MS, Al-amary KA. Bull Korea Chem Soc 2012;33:1900–6. [4] El-Daly SA, Asiri AM, Obeid AY, Khan SA, Alamry KA, Hussien MA, et al. Opt Laser Technol 2013;45:605–12. [5] Khan SA, Asiri AM, Al-Thaqafy SH, Faidallah HM, El-Daly SA. Spectrochem Acta A 2014;133:141–8. [6] Asiri AM, Marwani HM, Alamry KA, Al-Amoudi MS, Khan SA, El-Daly SA. Int J Electrochem Sci 2014;9:799–809. [7] Khan SA, Razvi MAN, Bakry AH, Afzal SM, Asiri AM, El-Daly SA. Spectrochem Acta A 2015;137:1100–5. [8] Xie HQ, Liu ZH, Huang XD, Guo JS. Eur Polym J 2001;37:497–505. [9] Quist F, Velde CMLV, Didier D, Teshome A, Asselberghs I, Clays K, et al. Dyes Pigments 2009;81:203–10. [10] Leray A, Rouede D, Odin C, Grand Y, Mongin O, Desce MB. Opt Commun 2005;247:213–23. [11] Amalanathan M, Joe IH, Rastogi VK. J Mol Struct 2011;985:48–56. [12] Bonse J, Solis J, Urech L, Lippert T, Wokaun A. Appl Surf Sci 2007;253:7787–91. [13] Sutherland RL. Handbook of nonlinear optics. New York: Marcel Dekker Inc.; 1996. [14] Asiri AM, Marwani HM, Khan SA. J Saudi Chem Soc 2014;5:392–7. [15] Sheik-Bahae M, Said AA, Wei T, Hagan DJ, Van Stryland EW. IEEE J Quantum Electron 1990;26:760. [16] Mohammed Ali Qusay, Palanisamy PK. Optik 2005;116(515). [17] Geetha SK, Kumari SSP, Muneera CI. J Mater Sci Lett 2002;21:1339.