Synthesis, structural, photoluminescence, thermal, mechanical, dielectric, nonlinear optical and laser damage threshold studies of 2,3-dimethylquinoxalinium-4-chlorobenzenesulphonate

Accepted Manuscript Synthesis, structural, photoluminescence, thermal, mechanical, dielectric, nonlinear optical and laser damage threshold studies of 2,3-dimethylquinoxalinium4-chlorobenzenesulphonate M. Rajkumar, M. Dhanalakshmi, M. Sekar, A. Chandramohan, V. Murugesan PII: DOI: Reference:

S0167-577X(19)30281-2 https://doi.org/10.1016/j.matlet.2019.02.057 MLBLUE 25762

To appear in:

Materials Letters

Received Date: Revised Date: Accepted Date:

30 December 2018 7 February 2019 9 February 2019

Please cite this article as: M. Rajkumar, M. Dhanalakshmi, M. Sekar, A. Chandramohan, V. Murugesan, Synthesis, structural, photoluminescence, thermal, mechanical, dielectric, nonlinear optical and laser damage threshold studies of 2,3-dimethylquinoxalinium- 4-chlorobenzenesulphonate, Materials Letters (2019), doi: https://doi.org/10.1016/ j.matlet.2019.02.057

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Synthesis, structural, photoluminescence, thermal, mechanical, dielectric, nonlinear optical and laser damage threshold studies of 2,3-dimethylquinoxalinium- 4-chlorobenzenesulphonate M. Rajkumar a, M. Dhanalakshmi a, M. Sekar b, A. Chandramohan b and V. Murugesan a * a

Department of Chemistry, Pachamuthu College of Arts and Science for Women, Dharmapuri- 636

701, Tamil Nadu, India. b

Post-Graduate and Research Department of Chemistry, Sri Ramakrishna Mission Vidyalaya

College of Arts and Science, Coimbatore-641 020, Tamil Nadu, India. Abstract 2,3-dimethylquinoxaline-4-chlorobenzenesulphonate

(DMQPCS)

was

synthesized

successfully and grown as single crystals from 1:1 MeOH and water solvent mixture using slow evaporation method. Single crystal XRD analysis confirms that the molecular salt crystallizes in orthorhombic system with non-centrosymmetric space group, Pca21 and the crystal is stabilized by N+-H...O, O-H...O, N-H...O and C-H...O hydrogen bonding interactions. The presence of expected functional groups and the molecular structure were identified by FT-IR and NMR spectroscopic studies. Lower cut-off wavelength, % transmittance and optical band-gap value were determined by UV-Vis-NIR spectral analysis. The photoluminescence studies confirm green emission radiation. The thermal and mechanical behaviour were analyzed by TG-DTA analyses and Vickers microhardness tester, respectively. The SHG efficiency and Laser damage threshold were measured using an Nd:YAG laser of wavelength 1064 nm. Variation of the dielectric response of the grown crystal was studied at different temperatures. Keywords: Crystal structure, Organic, Optical materials and properties, Thermal properties, FTIR, X-ray techniques *Corresponding author Tel.: +918012214802 E-mail address: [email protected] (V. Murugesan) 1. Introduction The synthesis of organic materials through molecular engineering approach with large nonlinear optical properties has attracted with primary interest in the possibilities for reversibly

switching NLO systems due to potential applications such as information processing, telecommunication, 3D optical data storage and numerous opto-electronics [1]. Moreover, Organic crystals are exceptionally promising for photoinduced nonlinear optical effects [2]. In the search of new NLO materials with better thermal, optical and mechanical properties, many researchers have focused on the small organic molecules having a large dipole moment and a chiral structure which can be achieved through the hydrogen bond [3, 4]. Hydrogen bonding plays an important role in the organization of supramolecules from the organic acid and base containing the hydrogen bonding sites [5]. The intramolecular and intermolecular hydrogen bonds are the driving forces for the construction of the complex self-assembled structures generated by N-containing bronsted bases and the acidic components [6, 7]. Organic acids belong to one of the most prevalent functional compounds in crystal engineering because they possess the nice hydrogen bond donor and acceptor with a geometry that self-associates by supramolecular homosynthons of dimer or catemer [8-10]. Based on these backgrounds,

in

this

paper

the

crystal

structure

of

2,3-dimethylquinoxaline-4-

chlorobenzenesulphonate was reported and thermal, mechanical and optical properties are presented. 2. Experimental details 2,3-dimethylquinoxaline-4-chlorobenzenesulphonate

was

synthesized

by

mixing

a

stoichiometry ratio of methanolic solution of 2,3-dimethylquinoxaline (DMQ) and 4-chloro benzenesulphonic acid (PCS). The resulting solution was refluxed for 3 hours to form a colourless precipitate, filtered off and washed with Millipore water to remove the suspended impurities. After a normal growth period of 15 days, single crystals were harvested from MeOH and water solvent mixture (1:1). The crystal structure was established from the single crystal X-ray diffraction data obtained with a Bruker Kappa Apex-II diffractometer (Graphitemono-chromated, MoKα radiation (λ=0.71073 Aº). Other characterisations, UV-Vis-NIR (200-1250 nm), FTIR (4000-400 cm-1), 1H and

13

C NMR (Bruker AV III 500 MHz), TG/DTA (SDT Q600 V20.9 Build 20), Hardness

measurements (HMV SHIMADZU, make: HMV-2T), LDT ( QUANTA RAY Model LAB – 170 10, λ = 1064 nm, f = 15 cm, τ = 6 ns, Repetition rate: 10 Hz, energy per pulse: 1.5 mJ-3 J) and NLO

(Nd:YAG laser, 1064 nm wavelength, 6 ns pulse width with 10 Hz pulse rate and 0.5 μW energy per pulse) properties were also carried out for the title crystal. 3. Results and discussion UV-Visible (Fig.1(a)) spectrum shows two bands at 382 nm and 324 nm corresponding to nπ* and π-π* transitions of DMQPCS crystal, respectively. From UV-vis-NIR spectrum (Fig.1 (b)), the cut-off wavelength was found to be 390 nm, and % transmittance was 70 in visible-NIR regions. The optical band-gap value was found to be 3.52 eV using Tauc's plot. Hence, the absence of absorption in the region between 390 and 1100 declared that the crystal could be exploited for various optical applications. The florescence spectrum (Fig1(c)) exhibits a broad band at 429 nm in the emission spectrum of the material. The results indicate that the material has a blue fluorescence emission. The broadness of the band is due to the presence of various hydrogen bonds in the title material. As shown in Fig.1 (d), the absorption band at 3028 cm-1 is a result of the N+-H stretching vibration. The aromatic C-H stretching mode is observed at 2930 cm-1. The absorption bands obtained at 2944 and 2821 cm-1 are assigned to C-H stretching vibrations [11]. The aromatic ring C=C stretching vibrations are appeared at 1646, 1578 and 1530 cm-1. The asymmetric and symmetric deformation modes of CH3 group bring forth bands at 1467 and 1385 cm-1, respectively [11]. The asymmetric stretching vibrations of SO3- group appear at 1240 cm-1 and the corresponding symmetric vibration appears at 1145 cm-1 [12]. From the single crystal X-ray diffraction analysis (CCDC 1895406), the molecular salt crystallizes in orthorhombic system with non-centrosymmetric space groups, Pca21. The unit cell parameters are a=22.819(2) Å, b=7.8718(6) Å, c=17.7747(17) Å, α=β=γ=90°, and volume V=3192.9(5) Å3. The crystallographic data of DMQPCS crystal are listed in Table 1. The proton of the 4-chlorobenzenesulphonic acid was transferred to the N atom of 2,3-dimethylquinoxaline thereby formation of charge assisted N+-H...O hydrogen bonding interaction. The S-O band distances are 1.421(3), 1.426(4) and 1.450(4) for S(1)-O(1), S(1)-O(3) and S(1)-O(2), respectively which confirm the deprotonation of

the SO3H group. The asymmetric unit

comprises

two 2, 3-

dimethylquinoxalinium cation and two 4-chlorobenzenesulphonate anion as shown in the ORTEP

diagram (Fig. 2(a)). In the crystal, the packing of DMQPCS (Fig.2(c)) is stabilized predominantly by O-H...O and C-H...O hydrogen bonds. TG/DTA analyses (Fig.2 (b)) reveal that the material exhibits single sharp weight loss starting at 265 °C and below this temperature no significant weight loss is observed. From the DTA curve, the first sharp endothermic dip shows the melting point is 265 °C followed by decomposition of the material. The sharpness of endothermic dip indicates the good crystalline nature of DMQPCS crystal [13]. Before melting, no phase transition or decomposition was observed in the DTA curve. P

The Vicker's hardness value was calculated using the expression,Hv = 1.8544 (d2 ) Kg/mm2 , where, P is the load applied in kilograms (kg) and d is the average diagonal length in mm. The plot of load versus hardness number (Fig.3 (a)) shows that Hv increases with the increase of applied load exhibiting reverse indentation size effect. The relation between log P and log d is depicted in Fig.3(b). Using Meyer index, the work hardening coefficient (n) was found to be 2.80. According to Onitsch [14], the grown crystal falls under soft material category. The dielectric constant and loss were carried out as a function of frequency varying from 50 Hz to 5 MHz at room temperature. The dielectric constant was calculated using the following formula εr =

Cp d εo A

, Where, Cp is the measured

parallel capacitance, d is the thickness of the crystal, A is the electrode area, ε r dielectric constant and εₒ is the vacuum permittivity (8.85 x 10-12 F/m). From Fig.3(c) and (d), the dielectric constant and loss are high in the lower frequency region and further, the dielectric constant decreases with increasing frequency. The low value at the higher frequency region may be caused by the inability of the dipoles to comply with the external field. Hence, very low values of dielectric constant and dielectric loss at high frequencies suggest enhanced optical quality with lesser defects. Thus, the crystal could be useful for optoelectronic applications and NLO devices. The SHG efficiency of DMQPCS was examined using Kurtz and Perry technique [15] with Q-switched Nd: YAG laser, energy of 6.35 mJ/pulse at 1064 nm with a repetition rate of 10 Hz and pulse width of 8 ns. The emission of green radiation at 534 nm from the DMQPCS confirms the second harmonic generation in the crystal. The obtained SHG efficiency of was 1.42 times that of the

KDP crystal. The utility of NLO crystal depends not only on the linear and nonlinear optical properties, but also largely on its surface quality providing the ability to withstand high power intensities [16]. The laser damage threshold of grown DMQPCS crystal was measured using a Qswitched pulsed Nd:YAG (1064 nm) laser operating in transverse mode and pulse width of 10 ns in the frequency rate of 10 Hz. The energy density was calculated using the expression, Power density (Pd) = E/τπr2 GW cm2, where E is the input energy density (mJ), τ is the pulse width (ns), and r is the area of the circular spot (mm). The calculated laser damage threshold value of DMQPCS was found to be 1.24 GW cm2. Thus, the title crystal could be useful for high power laser applications. 4. Conclusions 2,3-dimethylquinoxalinium-4-chlorobenzenesulphonate was synthesized and grown into single crystals by slow solvent evaporation solution growth method. The crystal structure was confirmed by FT-IR and NMR spectral analysis, and single crystal X-ray diffraction analysis. Further, the single crystal X-ray diffraction analysis data indicated that the strength and directionality of the N+-H...O, O-H...O and C-H...O hydrogen bonds between 4-chlorobenzenesulphonate ion and 2,3-dimethylquinoxalinium ion are enforced to bring about the formation of binary organic salt crystal. UV-Vis-NIR spectrum showed highly transparent in Visible-NIR regions with cut-off wavelength found to be 390 nm. The calculated value of band-gap energy of the grown crystal was found to be 3.52 eV. Further, the photoluminescence showed blue emission radiation. TG-DTA studies indicated that the compound is thermally stable up to its melting point 265°C. Dielectric measurement of DMQPCS revealed the low dielectric constant and loss at higher frequencies. The Vicker's hardness studies indicated that the material belongs to soft material category. The SHG conversion efficiency of the crystal was found to be 1.42 times that of KDP material. The laser damage threshold was calculated to be 1.24 GW/cm2. The higher value of surface laser damage threshold of DMQPCS crystal suggested that the crystal could be useful material in laser frequency conversion. Hence, good transparency, good thermal and mechanical stabilities, high SHG efficiency and laser damage threshold of title crystal indicated that it is a promising candidate for NLO device applications.

The authors claimed no conflict of interest

Reference [1] Ts. Kolev, I.V. Kityk, J. Ebothe, B. Sahraoui , Chem Phys Lett .443 (2007)309-312. [2] V. Krishnakumar, R. Nagalakshmi, S. Manohar, M. Piasecki, I.V. Kityk, P. Bragiel, Phys. B: Condens. Matter 405 (2010) 839 [3] M. Gulam Mohamed, J. Madhavan, M. Vimalan, P. Sagayaraj, Arch. Appl. Sci. Res. 2 (2010) 323. [4] R. Nagalakshmi, V. Krishnakumarb, N. Sudharsana, A. Wojciechowski, M. Piasecki, I.V. Kityk, Michael Belsley, Dmitry Isakov, Physica B 406 (2011) 4019-4026 [5] M. Khurram, N. Qureshi, M.D. Smith, Chem. Commun. 48 (2006) 5006-5008. [6] R. Shukla, S.V. Lindeman, R. Rathore, Chem. Commun. 36 (2007) 3717. [7] C.Q. Wan, X.D. Chen, T.C.W. Mak, CrystEngComm 10 (2008) 475. [8] S. Aitipamula, A. Nangia, Chem. Eur. J. 11 (2005) 6727-6742. [9] K.K. Arora, V.R. Pedireddi, J. Org. Chem. 68 (2003) 9177-9185. [10] B.R. Bhogala, A. Nangia, Cryst. Growth Des. 3 (2003) 547-554. [11] M. Rajkumar, P. Muthuraja, M. Dhandapani, A. Chandramohan, J. Mol. Struct.1153 (2018) 192-201 [12] A. Silambarasan, M. Krishna Kumar, A. Thirunavukkarasu, I. Md Zahid, R. Mohan Kumar, P.R. Umarani, Spectrochim. Acta Mol. Biomol. Spectrosc. 142 (2015) 101-109. [13] A. Sher Gill, S. Kalainathan, J Phys Chem Solids 72 (2011) 961-967. [14] E.M. Onitsch, U ber die Mikroharte der Metalle, Mikroscopia 2 (1947) 131. [15] S. K. Kurtz and T. T. Perry, J. Appl. Phys., 39 (1968) 3798-3815. [16] I.V. Kityk, B. Marciniak, A. Mefleh, J. Phys. D: Appl. Phys. 34 (2001) 1-4.

Fig.1(a)Optical absorption, (b)optical transmittance, (c) Photoluminescence and (d) FT-IR spectra of DMQPCS crystal

Fig.2(a) ORTEP diagram, (b) TG/DTA thermogram and (c) Packing diagram of DMQPCS crystal

Fig.3(a) Hardness profile for respective load P, (b) log d versus log P, (c) Dielectric constant versus log f and (d) dielectric loss of DMQPCS crystal

Table 1. Crystal data and structure refinement of DMQPCS crystal Empirical formula

C16 H15 Cl N2 O3 S

Formula weight

350.81

Temperature

293(2) K

Wavelength

0.71073 Å

Crystal system, space group

Orthorhombic, Pca21

Unit cell dimensions

a = 22.819(2) Å α=90˚ b = 7.8718(6) Å β =90˚ c = 17.7747(17) Å γ=90˚

Volume

3192.9(5) A˚3

Z, Calculated density

8, 2.070 Mg/m3

Absorption coefficient

1.437 mm-1

F(000)

1980

Theta range for data collection 2.91 to 26.37 deg. Completeness to theta = 26.37

99.90%

Refinement method

Full-matrix least-squares on F

Data / restraints / parameters

5212 / 1 / 419

Goodness-of-fit on F^2

1.016

Final R indices [I>2sigma(I)]

R1 = 0.0619, wR2 = 0.0883

R indices (all data)

R1 = 0.1213, wR2 = 0.1099

Absolute structure parameter

-0.04(8)

Largest diff. peak and hole

0.278 and -0.222 e.A-3

Limiting indices

-18<=h<=28, -8<=k<=9, -22<=l<=15

Graphical abstract

Highlights  An organic DMQPCS crystal was grown by the slow evaporation method.

 The title crystal system is orthorhombic with space group of Pna21.  SHG efficiency of crystal is 1.42 times that of KDP crystal.  Laser damage threshold energy is found to be 1.24 GW/cm2.  The grown crystal belongs to soft material category.