Synthesis, structural, growth, optical, electrical, thermal and third order nonlinear optical properties of a novel organic single crystal: p -Toluidinium malonate

Journal Pre-proof Synthesis, structural, growth, optical, electrical, thermal and third order nonlinear optical properties of a novel organic single crystal: p -Toluidinium malonate

S. Suresh, V. Jaisankar, G. Vinitha, R. Mohan Kumar PII:

S0022-2860(19)31366-3

DOI:

https://doi.org/10.1016/j.molstruc.2019.127257

Reference:

MOLSTR 127257

To appear in:

Journal of Molecular Structure

Received Date:

16 April 2019

Accepted Date:

18 October 2019

Please cite this article as: S. Suresh, V. Jaisankar, G. Vinitha, R. Mohan Kumar, Synthesis, structural, growth, optical, electrical, thermal and third order nonlinear optical properties of a novel organic single crystal: p -Toluidinium malonate, Journal of Molecular Structure (2019), https://doi.org /10.1016/j.molstruc.2019.127257

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Synthesis, structural, growth, optical, electrical, thermal and third order nonlinear optical properties of a novel organic single crystal: p -Toluidinium malonate S. Suresha, V. Jaisankarb G. Vinithac, R. Mohan Kumar a* a Department b Department c Department

of Physics, Presidency College, Chennai-600 005, India

of Chemistry, Presidency College, Chennai-600 005, India

of Physics, School of Advanced Sciences, VIT, Chennai- 600 127, India

Abstract Novel organic nonlinear optical material; p-Toluidinium malonate (PTM) was grown from aqueous solution by slow evaporation technique. The lattice parameters were evaluated from single crystal X-ray diffraction analysis and found that crystal system belongs to monoclinic with centrosymmetric space group P21/c. The solid state parameters; valence electrons, Plasma energy, Penn gap and Fermi energy were evaluated theoretically. These estimated values are used to calculate the electronic polarizability of PTM crystal. The functional groups exist in the compound were identified using FT-IR and FT-RAMAN spectroscopy. PTM crystal showed transmittance in the entire visible region with lower cut off wavelength of 311 nm and band gap energy of 3.8 eV. The photoluminescence spectrum was recorded to explore the emission and thermal behavior of PTM crystal by employing TG/DTA analysis. Dielectric measurement was carried out on the grown crystal at different temperatures to evaluate electrical properties. The third-order nonlinear optical parameters were estimated by Z-scan technique using 532 nm diode pumped CW Nd:YAG Laser. Key words: Molecular structure; Crystal growth; Spectral analysis; Nonlinear optical material; Z-scan studies

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*Corresponding author: Dr. R. Mohan Kumar Associate Professor Department of Physics Presidency College, Chennai- 600 005 Tel: 9444600670 Email: [email protected]

1. Introduction Nonlinear optical crystals are the vital materials in the development of laser science and technology for the change in frequency of laser beam and modulation. NLO materials with high optical nonlinearities is an important task because of their practical applications in optical devices, high speed information processing, waveguide fabrication, optical storage and optical communications, switching and signal processing devices [1-2]. In centrosymmetric crystals, the intermolecular level control in organic synthesis has inspired many researchers for the growth of third-order nonlinear optical (TONLO) materials. In fact, many molecular organic compounds have been made to possess large molecular hyperpolarizabilities. The analysis of monoclinic susceptibility χ(3) is very significant because it is a four photon process which is responsible for the nonlinear effects such as self-focusing, self-phase modulation, four wave mixing process, Raman scattering and others. The third-order nonlinear optical properties of a crystal can be performed by the Z-scan technique. This technique is an efficient tool for ascertaining the nonlinear optical effect. It is extensively used in the characterization of optical nonlinearity, because it provides not only the magnitude but also the sign of the real and imaginary parts of the third-order nonlinear susceptibility [3-4]. Fundamentally, this method consists of translating a sample through the focus of a Gaussian beam and monitoring the alterations in the far field intensity pattern. When the intensity of the incident laser beam is adequate to induce nonlinearity in the sample, it can either

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converge (self-focusing) or diverge (self-defocusing) the beam, depending on the type of that nonlinearity [5-6]. p-Toluidine is an interesting compound which is an aryl amine whose chemical structure is similar to aniline except that a methyl group is substituted onto the benzene ring. The toluidine is used as dye and as component accelerators in cyanoacrylate glues. As a diagnostic adjunct in the detection of asymptomatic oral Squamous Carcinoma, toluidine blue is used to reduce the false negatives but the toluidine compounds are suspected to be carcinogenic [7]. To find a compound which has similar structure and properties, but less carcinogenic with the same application potential was the inclination to use toluidine for the synthesis. p-Toluidine contains proton acceptor amino (NH2) group, the zwitterions, which creates a strong hydrogen bond in the form of ammonia (NH3). Due to the weak base character of aniline complex, p-Toluidine (C7H9N) accepts the proton by forming p-Toluidinium cation (C7H10N+) to enchance the NLO properties. The p-Toluidine based crystals; p-Toluidinium L-Tartrate [8], 4-methylanilinium-3-carboxy 4hydroxybenzenesulphonate [9], p-Toluidinium picrate [10], 4-methylanilinium p-toluenesulfonate [11] have been reported. The malonic acid, a dicarboxylic acid with structure (C3H4O4) has –OH hydroxyl group as a proton donor and creates the bond in the form of (C3H3O4–) a malonate anion. The organic compounds such as L-Histidine malonate [12], L-phenylalanine malonate [13] have been synthesized and its properties have been studied. In the present investigation, p-Toluidinium malonate structure was reported for the first time (CCDC reference: 1882756). The PTM crystal was grown by slow solvent evaporation method and its properties were analyzed. The vibration spectral, optical, electrical, thermal, third-order susceptibility of PTM crystals were studied for the first time and the obtained results were elaborately discussed to show its suitability in nonlinear optical devices.

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2. Experimental 2.1 Material used for crystal p-Toluidinium malonate single crystal was synthesized by taking p-Toluidine (LOBA 99%) and malonic acid (LOBA 99%) and dissolved in water at room temperature the reaction scheme shown in Fig.1. 2.2 Synthesis of single crystal p-Toluidinium malonate single crystal was synthesized by slow solvent evaporation technique. p-Toluidine (2.67g) and malonic acid (2.60g) were taken in equimolar ratio and dissolved in 50 ml of double distilled water. The solution was stirred for 6 h at room temperature (303 K) to get homogeneous mixture of saturated solution. The resulting solution was filtered by using high quality filter paper to remove the suspended impurities. The filtrate was then collected and kept aside unperturbed in an atmosphere which will be most suitable for the growth of single crystals. Good optical quality single crystal of size about 19 × 10× 2 mm3 was obtained in 39 days time period. The photograph of as grown p-Toluidinium malonate crystal is shown in Fig.2. 2.3 Characterization p-Toluidinium malonate (PTM) single crystal was subjected to various characterization techniques for its suitability in device fabrications. BRUKER KAPPA APEX II CCD single crystal X-ray diffractometer with MoKα radiation (λ = 0.71073 Å) was used to determine the crystal structure and cell dimension. The crystal structure was solved by direct methods using SHELXS2014 structure solution program and refined by the full-matrix least-squares method on F2 using the SHELXL-2014 program package [14]. The crystal data collection, data reduction, and empirical absorption corrections were also carried out using APEX2, SAINT and SADABS programmes [15]. The FT-IR spectrum was performed using Perkin Elmer FT-IR

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Spectrophotometer through KBr pellet technique (1.0 cm-1 resolution) in the wave number range 4000-400 cm-1 and the FT-RAMAN spectrum was performed by using Bruker: RFS 27 FT-RAMAN Spectrometer (2.0 cm-1 resolution) in the wave number range 50-4000 cm-1 respectively. UV-Visible transmittance spectrum was recorded using T90+ UV/Visible spectrometer in the wavelength region 200-800 nm. The thermal stability of the grown PTM crystal was studied by Thermo gravimetric and differential thermal analysis using Simultaneous STA-600 Perkin Elmer thermal analyzer. TG/DTA measurement was carried out in nitrogen atmosphere at the temperature range 50-800 °C. The photoluminescence spectrum of PTM crystal was recorded using Cary Eclipse Fluorescence Spectrometer with a Xenon arc lamp source. Third-order nonlinear optical properties of PTM was studied using a 532 nm Diode-Pumped Continuous Wave (CW) Nd:YAG laser (Coherent Compass TM 215M-50). 3. Results and Discussion 3.1 Single crystal X-ray diffraction analysis Single crystal X-ray diffraction intensity data was collected for the PTM compound at room temperature using BRUKER KAPPA APEX II CCD single crystal X-ray diffractometer with MoKα radiation (λ = 0.71073 Å) at T= 295 K. The crystal structure was solved by the direct method and refined by the full matrix least-squares technique on F2 employing the SHELXL 97 program package [16]. The crystallographic data of PTM crystal is listed in Table 1. The asymmetric unit of the title compound comprises of a p-Toluidinium cation and a malonate anion as shown in the ORTEP diagram (Fig.3). The packing diagram of p-Toluidinium malonate is shown in Fig.4. The molecular formula of the grown crystal is (C10H13NO4). The PTM crystallized in monoclinic crystal system with space group P21/c which is a centrosymmetric. The calculated

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cell parameters are a = 12.996(3) Å, b = 9.2813(19) Å, c = 8.665 (2) Å, α = γ = 90°, β = 105.503(7)° and volume V = 1007.1(4) Å3. In the PTM crystal structure, intra as well as intermolecular hydrogen bonds could be observed. p-Toluidinium (C7H10N+) cation and malonate (C3H3O4−) anion comprises the asymmetric unit. The cation is protonated at N atom of aniline group and anion is deprotonated at O atom of one of the carboxyl group. In the asymmetric unit, an N–H…O hydrogen bond links the anion and cation. In the crystal structure, inter-ionic N–H…O and O–H…O hydrogen bonds link the anions and cations into infinite two dimensional network along (0 0 1) plane. The intermolecular N–H…O hydrogen bond’s interaction links the molecules into an infinite one-dimensional ribbon structure along the a-axis (Fig.4.) The bond lengths, bond angles and torsion angles are given in Tables 2 and 3, respectively. The hydrogen bond interaction involved in the PTM crystal is shown in Table 4. 3.2 Polarizability analysis Solid state parameters are important to estimate the electronic polarizability of the material. The high frequency dielectric constant value of PTM crystal was used to calculate the electronic parameters like valence electron plasma energy, Penn gap, Fermi energy and electronic polarizability. Single crystal structure and lattice parameter values of p-Toluidinium malonate were estimated using single crystal X-ray diffractometer. The molecular weight M = 280.34g, total number of valance electrons Z = 102, the density of the grown crystal ρ = 1.23g and dielectric constant ɛ∞ = 28.33 at 3MHz were estimated. The valence electron plasma energy (  p ) was calculated using the following relation [17],

Z  p  28.8 p M

1

2  

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where Z = ((13 x Zc) + (16 x ZH) + (2 x ZN) + (3 x ZO) + (1 x Zs)) = 102 is the total number of valence electrons. The plasma energy in terms of Penn gap and Fermi energy [18] is given by

Ep 

 p 1

   12

where  p is the valence electron Plasmon energy and the Fermi energy 𝐸𝐹 [19] is given by 𝐸𝐹 = 0.2924 (ħ𝜔𝑃)4/3 Polarizability (α) can be obtained using the relation [20]    2    p  S o  M    0.396  10  24  2   p  2 S o  3E p    

where So is a constant for the material and it is given by

 Ep So  1    4 E f

 1  Ep      3  4 E f 

2

The calculated value of ‘α’ agrees well that of Clausius-Mossotti equation, which is given by,



3M 4N a 

  1       2 

The polarizability is highly sensitive to the band gap [21], where NA is the Avogadro number. The dielectric constant of material is a very important parameter for calculating the physical or

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electronic properties of materials. These values of PTM are compared with the values of standard KDP material [22] and listed in Table 5. 3.3. FT-IR and FT-Raman spectral analysis Infrared spectroscopy has proved as a potential tool for the confirmation of protonation and hydrogen bonding interaction and it is also to identify the presence of functional groups in the organic compounds [23]. Both FT-IR and FT-Raman spectra were recorded in the range 400-4000 cm-1 and depicted in Figures 5 and 6. NH3 vibration The peaks observed at 3443 and 3349 cm-1 in the higher frequency region are associated with asymmetric and symmetric stretching vibrations of N-H in the amino (NH3+) group of p-Toluidinium in IR spectrum. The symmetric N-H bending vibration (NH3+) peak observed at 1500 cm-1 in IR spectrum. C-H vibration The C-H stretching vibration of aromatic ring peak observed at 3075 and 3026 cm-1 in Raman spectrum. The aromatic ring C-H in-plane bending vibration peak noted at 1035 cm-1 in IR spectrum. The aromatic ring C-H out-of-plane bending vibration peaks noted at 809 cm-1 in IR spectrum and 826 cm-1 in Raman spectrum. CH3 vibration The presence of methyl groups (CH3) confirmed through the asymmetric stretching vibrations of C-H at 2910 and 2917 cm-1 in IR and Raman spectrum respectively. The methyl C-H symmetric stretching vibration (CH3) peak observed at 2630 cm-1 for IR spectrum. The methyl C-H asymmetric and symmetric bending vibration (CH3) peaks observed at 1450 and 1391 cm-1 in Raman spectrum respectively [24].

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C=O and C=C vibration The C=O stretching vibration of carbonyl group observed at 1619 cm-1 in Raman spectrum. The C=C stretching vibration confirmed the presence of aromatic ring peak observed at 1593 cm-1 in IR spectrum. C-O Stretching and O-H bending vibration The peak observed at 1222 cm-1 corresponds to the C-O stretching vibration in Infrared spectrum and the peak noticed at 1212 cm-1 in Raman spectrum. The O-H in-plane-bending and out-of-plane bending vibrations peaks observed at 1321 and 915 cm-1 in Raman spectrum. CH2 vibration The twisting vibration of CH2 group assigned at 1367 cm-1 in Infrared spectrum. The Infrared band at 689 cm-1 and the corresponding Raman band at 688 cm-1 are due to the wagging of CH2 group of malonate ion [25]. The comparative assignments for the peaks obtained in FT-IR and FT-Raman spectra are given in Table 6. For a centrosymmetric material, an exact match in wave numbers between Infrared and Raman spectra has been observed. In the vibrational spectra of p-Toluidinium malonate crystal, there is an excellent matching between vibrational bands of Infrared and Raman spectra. 3.4 Optical studies Optical

transmission

spectrum

of

p-Toluidinium

malonate

crystal

recorded

using

T90+ UV/VIS spectrometer in the wavelength range 200-800 nm is shown in Fig. 7. The PTM single crystal showed maximum transparency of 66 % in the entire visible region with the cut-off wavelength of 311 nm. The spectrum indicates that the crystal has wide optical

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transmission window, which is a desired property for NLO activity. The absorption coefficient (α) can be determined from the transmission spectrum based on the relation,  

2.3026 1 log   t T

Where T is the transmittance and t is the thickness of the crystal. The optical band gap was estimated from the transmission spectrum and the optical absorption coefficient (α) near the absorption edge was calculated using the relation, (αhν)2 = A (Eg – hν) Where Eg is optical band gap of the crystal and A is a constant. The variation of (αhν)2 with ‘hν’ in the fundamental absorption region was plotted as shown in Fig.8. The band gap of PTM crystal estimated by extrapolation of the linear part of the graph is 3.8 eV. The band gap and transmittance in the entire visible region enables the crystal suitable for optoelectronic and photonic applications [26]. 3.5 TG/DTA Thermal analysis The thermo gravimetric analysis (TGA) and differential thermal analysis (DTA) are very important tools to find the thermal stability and melting point. TG/DTA analysis was performed in the nitrogen atmosphere with a heating rate of 20 ºC /min in the temperature range 50-800 ºC. The powdered sample weighing 2.44 mg was used for this investigation and the thermogram is depicted in Fig.9. From TG curve, it was observed that the substance is stable and there is no weight loss up to 131 °C in the TGA trace. Initial major weight loss occurred at 171.2 °C with elimination of 26.42 %. The second stage weight loss noticed at 385.3 °C experiences a weight loss about 47.39 %. The third stage decomposition at the temperature 693.2 °C incurred a weight loss about 20.38 %. The DTA curve showed two endothermic dips occurring at 165 ºC and 379 ºC.

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The first endothermic dip observed at 165 ºC is attributed to the melting point of the compound which is in good agreement with the capillary melting point apparatus. It was followed by another endothermic dip at 379 ºC. Both these endothermic dips matched with the decomposition in the TGA trace. Therefore, it was established that this material could be applied to NLO applications. 3.6 Dielectric studies The dielectric measurement of the materials provides information about electrical properties that determines its suitability for device application [27]. The crystal of 2.4 mm thickness was subjected to dielectric studies at different temperatures for different frequencies ranging from 50 to 5MHz. The dielectric constant was calculated using the following relation, εr = Cpd /εoA Where, Cp is the measured parallel capacitance, d is thickness of the crystal, A is the electrode area, εr is the dielectric constant and εₒ is the vacuum permittivity (8.85 x 10-12 F/m). Figures 10 & 11 illustrate the relationship between dielectric constant and dielectric loss with respect to applied frequencies at different temperatures. From these results, it is clear that both the dielectric constant and loss decrease with increasing frequency at different temperatures and remain constant at higher frequencies. The high value dielectric constant at low frequencies owes to the presence of all the four polarizations such as space charge, orientation, ionic and electronic polarizations at higher frequencies [28]. The high value dielectric loss at low frequencies is due to the oscillation of dipoles at higher frequencies, all the polarizations are not operative. So no energy has spent to rotate dipoles, hence dielectric loss is high. Moreover, as the temperature increases, dipoles are responded to the applied electric field, so that the dielectric constant gets increased. Additionally, the low dielectric constant and dielectric loss at higher frequencies clearly reveals

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that the title crystal possesses high optical quality and has low defects which are most important and desirable property of the crystalline materials for nonlinear optical applications [29]. 3.7 Z-scan studies Third order nonlinear optical characteristics of PTM can be accomplished by means of the process of Z-scan. This approach facilitates the concurrent measurement of magnitude as well as sign of the nonlinear refractive index (n2) and nonlinear absorption (β) using the open and closed configuration of Z-scan. In the present investigation, Nd-YAG laser was adopted to assess the third order nonlinearity of PTM. From the obtained data of Z-scan, the difference between the normalized valley and peak transmittance (ΔTp-v) can be evaluated by using the relation, ∆Tp-v= 0.406 (1- S) 0.25 |∆ϕ0| where ‫׀‬‫ ׀‬signifies the on-axis phase shift at the focus and S denotes the aperture linear transmittance, which is estimated using the relation, S = 1- exp (- 2ra2 / ωa2) ra indicates the aperture radius and ωa represents the radius at the aperture. The on-axis phase shift ‫׀‬‫ ׀‬is given by, Δ‫׀‬‫ = ׀‬k n2 Leff I0 Leff = (1- e-αL) / α, L stands for the length of the used sample, Io denotes the laser intensity at focus z = 0, α indicates the linear absorption coefficient and k is the wave number (k = 2π /λ) The nonlinear absorption is reckoned by utilizing the data obtained from the open aperture Z-scan and it is given by,

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β=

2 2 ∆T I0Leff

ΔT is the maximum value of the open aperture normalized transmittance obtained from the Z-scan plot. The nonlinear absorption coefficient (β) exhibited a negative value for saturation absorption and positive in the case of two photon absorption. The real and imaginary part of nonlinear optical susceptibility (χ3) were evaluated from the experimentally determined ‘n2’and ‘β’ values. Re

χ3 (esu)

=

Im χ3(esu) =

10 ―4 (εoC2n2on2) π 10 ―2 (𝜀𝑜𝐶2𝑛2𝑜𝜆𝛽) 4 π2

(cm2/W) (cm/W)

where, ε0 denotes the vacuum permittivity and c represents the velocity of light in vacuum. The absolute third order nonlinear optical susceptibility χ(3) is given by

χ(3) = (Reχ(3))² + (Imχ(3))² It is observed that the closed aperture Z-scan curve of PTM discloses the peak to valley configuration as well as it is an evidence for negative nonlinearity as illustrated in Fig.12. This is also represented as self-defocusing effect which takes place due to the dependence of refractive index with temperature and finds application in the domain of fabricating optical sensors [30-31]. The open aperture configuration of Z-scan is displayed in Fig.13. The nonlinear absorption coefficient (β) is found to be 0.03 x 10- 4cm/W and it signifies the process of saturable absorption and it is widely used for the application of optical power limiting process. The data obtained in this way reflects purely the effect of nonlinear refraction. The experimental measurement of n2 and β allows one to determine the third order nonlinear optical susceptibility χ(3). The determined values of nonlinear parameters n2, β and χ(3) of PTM are -7.40 × 10-8 cm2/W,

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0.03 × 10-4 cm/W and 9.84 × 10-6 esu respectively. It indicates that PTM exhibits negative nonlinear optical properties. Both β and n2 contribute to the third order nonlinearity of the sample. The nonlinear absorption can be attributed to saturation absorption process, while the nonlinear refraction leads to self-defocusing in the compound. The Z-scan data precisely illustrates that PTM shows the third order nonlinear optical characteristics and enumerated in Table 7. Hence this material is suitable for nonlinear optical applications such as the protection of human eyes and photo sensors.

4. Conclusion p-Toluidinium malonate organic molecular salt was synthesized and crystals were grown by slow solvent evaporation solution growth technique at ambient temperature. p-Toludinium (C7H10N+) cation and malonate (C3H3O4−) anion in the asymmetric unit. The cation protonated at N atom of aniline group and anion deprotonated at O atom of the carboxyl group. In the crystal structure of ionic N–H…O and O–H…O hydrogen bonds link the anions and cations into infinite two dimensional network along (0 0 1) plane. The presence of functional groups was confirmed by FT-IR and FT-Raman spectral analysis. The optical properties were studied by UV-visible transmittance spectral analysis. TG/DTA traces indicate that the PTM crystal is thermally stable up to 131 ºC without any phase transition. The dielectric constant and dielectric loss of PTM crystal ascertained the dielectric behaviour which is a pre-requisite for optoelectronic device applications. The open and closed Z-scan curves show that PTM crystal has saturable absorption and self-defocusing nature. Hence, the PTM crystal can be used to make devices for laser, photonic and optoelectronic applications.

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Supporting information Crystallographic data (excluding structure factors) for the structural analysis has been deposited with the Cambridge Crystallographic Data Centre, No. CCDC-1882756. Copies of this information may be obtained free of charge from: The Director, CCDC, 12 Union Road, Cambridge CB2 1EZ, UK. Fax: +441223 336e033, E mail: [email protected], or http:// www.ccdc.cam.ac.uk. Acknowledgements One of the authors, S. Suresh would like to thank, Dr. R. Ravanan, Principal, Presidency College, Chennai-05, for providing FT-IR as a National Facility under Project No.SR / FST / College-098/ 2012(c). The authors also thank SAIF, IIT Madras, Chennai-36, for crystal data collection and FT-RAMAN measurements.

References [1] L. Jiang, H. Dong, W. Hu, Organic single crystal field-effect transistors: Advances and Perspectives, J. Mater. Chem. 20 (2010) 4994-5007. [2] T. Kaino, Waveguide fabrication using organic nonlinear optical materials, J. Opt. A, Pure Appl. Opt. 2 (2000) R1-R7. [3] M. Sheik-Bahae, A. A. Said, E. W. Van Stryland, High sensitivity single beam n2 measurements, Opt. Lett. 14 (1989) 955-957. [4] M. Sheik-Bahae, A. A. Said, T. Wei, D. J. Hagan, E.W. Van Stryland, Sensitive measurement of optical nonlinearities using single beam, IEEE J. Quantum Electron. 26 (1990) 760-769.

Journal Pre-proof

[5] R. A. Ganeev, I. A. Kulagin, A. I. Ryasnyansky, R. Tugushev, T. Usmanov, Characterization of nonlinear optical parameters of KDP, LiNbO3 and BBO crystals, Opt. Commun. 229 (2004) 403-412. [6] T. C. Sabari Girisun, S. Dhanuskodi, Linear and nonlinear optical properties of tris thiourea zinc sulphate single crystals, Cryst. Res. Technol. 44 (2009) 1297-1302. [7] A. Masbher, Reevaluation of Toluidine Blue Application as a Diagnostic Adjunct in the Detection of Asymptomatic Oral Squamous Carcinoma: A Continuing Prospective Study of Oral Cancer III, Cancer 46 (1980) 758-756. [8] S. Suresh, S. Reena Devi, B. M. Sornamurthy, M. Arivanandhan, R. Mohan Kumara, Growth, structural and optical studies of a novel nonlinear optical material: p-Toluidinium L-Tartrate, J. Opt. 185 (2019) 651-656. [9] M. Rajkumar, P. Muthuraja, M. Dhandapani, A. Chandramohan, Supramolecular network through N-H...O, O-H...O and C-H...O hydrogen bonding interaction and density functional theory studies of 4-methylanilinium-3-carboxy-4-hydroxybenzenesulphonate crystal, J. Mol. Struct. 1153 (2018) 192-201. [10] K. Muthu, S. Meenakshisundaram, Crystal growth, structure and characterization of p-Toluidinium picrate, J. Cryst. Growth, 352 (2012) 163-166. [11] G. Shanmugam, S. Brahadeeswaran, Spectroscopic, thermal and mechanical studies on 4-methlanilinium p-toluenesulfonate a new organic NLO single crystal, Spectrochim Acta A. 95 (2012) 177-183.

[12] K. Ramya, N. T. Saraswathi, C. Ramachandra Raja, Growth and characterization of an organic nonlinear optical material: L-Histidine malonate, J. Opt and Laser Tech. 84 (2016) 102-106. [13] M. Prakash, D. Geetha, M. Lydia Caroline, P. S. Ramesh, Crystal growth, structural, optical, dielectric and thermal studies of an amino acid based organic NLO material: L-phenylalanine L-phenylalaninium malonate, Spectrochim Acta A. 83 (2011) 461-466.

Journal Pre-proof

[14] G. M. Sheldrick, Crystal structure refinement with SHELXL, Acta Crystallogr. C 71 (2015) 3-8. [15] Bruker, APEX2, SAINT, XPREP, and SADABS. Bruker AXS Inc, Madison, Wiscosin, USA (2004). [16] G. M. Sheldrick, A short history of SHELX, Acta Cryst. A64 (2008) 112-122. [17] V. Kumar, B. S. R. Sastry, Heat of formation of ternary chalcopyrite semiconductors, J. Phys. Chem. Solids, 66 (2005) 99-102. [18] N. M. Ravindra, R. P. Bharadwaj, K. Sunil Kumar, V. K. Srivastava, Model based studies of some optical and electronic properties of narrow and wide gap materials, Infrared. Phys. 21 (1981) 369-381. [19] D. R. Penn, Wave-number-dependent dielectric function of semiconductors, Phys. Rev. 128 (1962) 2093-2097. [20] N. M. Ravindra, V. K. Srivastava, Properties of liquid lead mono sulfide, lead selenide and lead telluride, Infrared. Phys. 20 (1980) 399-418. [21] R. R. Reddy, Y. N. Ahammed, M. Ravi Kumar, Variation of magnetic susceptibility with electronic polarizability in compound semiconductors and alkali halides, J. Phys. Chem. Solids, 56 (1995) 825-829. [22] S. Sagadevan, A simple theoretical approach to analyze the second harmonic generation of single crystals, J. Opt. 126 (2015) 317-319. [23] M. Rajkumar, A. Chandramohan, Synthesis, growth, characterisation and laser damage threshold

studies

of

N,N-dimethylanilinium-3-carboxy-4-hydroxybenzenesulphonate

crystal: An efficient SHG material for electro-optic applications, Opt. Mater. 66 (2017) 261-270. [24] R. M. Silverstein, F. X. Webster, Spectrometric identification of organic compounds, John Wiley and Sons Publishers, Singapore, 2004.

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[25] V. Mathew, J. Joseph, S. Jacob, K. E. Abraham, Crystallization and spectroscopic studies of manganese malonate, Bull. Mater. Sci. 33 (2010) 433-437. [26] L. Guru Prasad, V. Krishnakumar, R. Nagalakshmi, S. Manohar, Physicochemical properties of highly efficient organic NLO crystal: 4-Aminobenzamide, Mater. Chem. Phys. 128 (2011) 90-95. [27] V. Sivasubramani, M. Senthil Pandian, K. Boopathi and P. Ramasamy, Crystal growth, structural, optical, thermal and dielectric studies of non-linear optical 2-amino-5 nitropyridinium nitrate (2A5NPN) single crystals, Mater. Res. Innovations, (2016) 1-9. [28] D. Xue, K. Kitamura, Dielectric characterization of the defect concentration in lithium niobate single crystals, Solid State Commun. 122 (2002) 537-541. [29] M. Saravanan, S. Abraham Rajasekar, Growth and characterization of benzaldehyde 4-nitro phenyl hydrazone (BPH) single crystal: A proficient second order nonlinear optical material, Opt. Mater. 54 (2016) 217-228. [30] P. Jayaprakash, P. Sangeetha, C. Rathika Thaya Kumari, M. Lydia Caroline, Investigation on the growth, spectral, lifetime, mechanical analysis and third-order nonlinear optical studies of L-Methionine admixtured D-Mandelic acid single crystal: a promising material for nonlinear optical applications, Physica B, 518 (2017) 1-38. [31] M. Nageshwari, P. Jayaprakash, C. Rathika Thaya Kumari, G. Vinitha, M. Lydia Caroline, Growth, spectral, linear and nonlinear optical characteristics of an efficient semiorganic ancentric crystal: L-Valinium L-Valine Chloride, Physica B, 511 (2017) 1-9.

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Figure Caption Fig.1 Material synthesis scheme of p-Toluidinium malonate Fig.2 Photograph of as grown p-Toluidinium malonate crystal Fig.3 ORTEP plot of the molecule with atom numbering scheme drawn at 30% probability ellipsoid level. Fig.4 Packing of PTM compound viewed along the a-axis. Fig.5 FT-IR spectrum of PTM crystal Fig.6 FT-Raman spectrum of PTM crystal Fig.7 UV-Vis transmission spectrum of PTM crystal Fig.8 Plot of (αhν)2 vs. photon energy of PTM crystal Fig.9 TGA and DTA curves of PTM crystal Fig.10 Plot of dielectric constant vs. log frequency of PTM crystal Fig. 11 Plot of dielectric loss vs. log frequency of PTM crystal Fig.12 Z-scan curve traced in closed aperture mode for PTM crystal Fig.13 Z-scan curve traced in open aperture mode for PTM crystal

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Table caption Table 1 Crystal data and structure refinement for PTM crystal Table 2 Bond lengths (Å) and angles (deg) for PTM crystal Table 3 Torsion angles (deg) for PTM crystal Table 4 Hydrogen bonds for PTM (Å and deg) crystal Table 5 Comparison of solid state parameters of PTM with KDP crystal Table 6 FT-IR and FT-Raman spectral assignment of PTM crystal Table 7 Estimation of third order nonlinear optical parameters of PTM crystal

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Conflict of Interest

The journal of Molecular Structure, Elsevier Publication is a scientific journal that publishes original papers and review articles on the design, synthesis, structural, characterization and applications of materials, suitable for various optical devices. This journal is more interested and fascinated for young researchers. The title “Synthesis, structural, growth, optical, electrical, thermal and third order nonlinear optical properties of a novel organic single crystal: p -Toluidinium malonate” a good NLO material related work and suitable for this journal.

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Figure 1

NH2

O HO

NH3

O

p-toluidine

O

OH

CH3

O

O OH

CH3 malonic acid

p-toluidinium malonate

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Figure 2

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Figure 3

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Figure 4

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Figure 5

102 100

96 94

4000

3500

3000

2500

2000

1500

Wavenumber (cm-1)

1000

689

809 1035

1367

84

1222

1593 1500

86

2630

88

2910

90

3443

92

3349

Transmittance (%)

98

500

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Figure 6

826

688 915

0.04

1321 1391 1212

2917

1619

3075 3026

0.06

Raman intensity

1450

0.08

0.02

0.00

4000

3500

3000

2500

2000

1500

Wave number (cm-1)

1000

500

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Figure 7

70

60

transmittance (%)

50

40

30

20

311 nm

10

0 300

400

500

600

700

Wavenumber (nm)

800

900

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Figure 8

-30

8.0x10

-30

6.0x10

(h)

2

-30

4.0x10

-30

2.0x10

0.0

Eg=3.8eV 1

2

3

Photonenergy (eV)

4

5

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Figure 9

Endo

100

-100

80

0

60

100

40

200

20

300

0 0

100

200

300

400

500

Temperature (C)

600

700

800

Weight (%)

Heat Flow (W.m-2)

-200

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Figure 10

Dielectric constant

100

313 K 333K 353 K

80

60

40

20 2.2

2.4

2.6

Log f

2.8

3.0

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Figure 11

Dielectic Loss

2.0

313K 333K 353K

1.5

1.0

0.5

0.0

2.0

2.2

2.4

Log f

2.6

2.8

3.0

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Figure 12

1.8

Closed aperture

Normalized tranmittance

1.6 1.4 1.2 1.0 0.8 0.6 0.4 0.2 0.0 -15

-10

-5

0

Z Position (mm)

5

10

15

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Figure 13

1.040

Open aperture Normalized transmittance

1.035 1.030 1.025 1.020 1.015 1.010 1.005 1.000 0.995 -15

-10

-5

0

Z Position (mm)

5

10

15

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Highlights

 Crystal structure of PTM is reported for the first time.  The grown crystal belongs to monoclinic system with space group P21/c.  UV-Vis spectral studies show that PTM crystal has wide transmittance range up to 311 nm with band gap value of 3.8 eV.  Dielectric constant and dielectric loss was measured as a function of temperature and frequency.  The crystal PTM exhibits negative nonlinear refractive index (self defocusing effect).

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Table 1

Parameters

Values

Empirical formula Formula weight Temperature Wavelength Crystal system Space group Unit cell dimensions

C10 H13 N O4 211.21 295(2) K 0.71073 Å Monoclinic P 21/c a = 12.996(3) Å α= 90° b = 9.2813(19) Å β= 105.503(7)° c= 8.665(2) Å γ = 90°

Volume Z Density (calculated) Absorption coefficient F (000) Crystal size Theta range for data collection Index ranges Reflections collected Independent reflections Completeness to theta = 25.000° Refinement method Data / restraints / parameters Goodness-of-fit on F2 Final R indices (I>2 sigma (I)) R indices (all data) Extinction coefficient Largest diff. peak and hole

1007.1(4) Å 4 3 1.393 Mg/m 0.108 mm-1 448 3 0.240 x 0.220 x 0.180 mm 2.732 to 25.000° -15<=h<=15, -11<=k<=10, -10<=l<=10 7352 1766 (R(int) = 0.0308) 99.9 % 2 Full-matrix least-squares on F 1766 / 1 / 141 1.053 R1 = 0.0406, wR2 = 0.0950 R1 = 0.0662, wR2 = 0.1117 n/a -3 0.206 and -0.193 e. Å

3

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Table 2 Bond angle

Values

Bond angle

Values

C(1)-C(2) C(1)-C(6) C(1)-C(7) C(2)-C(3) C(2)-H(2) C(3)-C(4) C(3)-H(3) C(4)-C(5) C(4)-N(1) C(5)-C(6) C(5)-H(5) C(6)-H(6) C(7)-H(7A) C(7)-H(7B) C(7)-H(7C) C(8)-O(1) C(8)-O(2) C(8)-C(9) C(9)-C(10) C(9)-H(9A) C(9)-H(9B) C(10)-O(4) C(10)-O(3) N(1)-H(1A) N(1)-H(1B) N(1)-H(1C) O(3)-H(3A) C(2)-C(1)-C(6) C(2)-C(1)-C(7) C(6)-C(1)-C(7) C(1)-C(2)-C(3) C(1)-C(2)-H(2)

1.366(3) 1.373(3) 1.513(3) 1.385(3) 0.9300 1.357(3) 0.9300 1.362(3) 1.459(2) 1.389(3) 0.9300 0.9300 0.9600 0.9600 0.9600 1.247(2) 1.265(2) 1.522(3) 1.501(3) 0.9700 0.9700 1.218(2) 1.308(2) 0.8900 0.8900 0.8900 0.868(10) 116.8(2) 120.0(2) 123.1(2) 122.1(2) 118.9

C(3)-C(2)-H(2) C(4)-C(3)-C(2) C(4)-C(3)-H(3) C(2)-C(3)-H(3) C(3)-C(4)-C(5) C(3)-C(4)-N(1) C(5)-C(4)-N(1) C(4)-C(5)-C(6) C(4)-C(5)-H(5) C(6)-C(5)-H(5) C(1)-C(6)-C(5) C(1)-C(6)-H(6) C(5)-C(6)-H(6) C(1)-C(7)-H(7A) C(1)-C(7)-H(7B) H(7A)-C(7)-H(7B) C(1)-C(7)-H(7C) H(7A)-C(7)-H(7C) H(7B)-C(7)-H(7C) O(1)-C(8)-O(2) O(1)-C(8)-C(9) O(2)-C(8)-C(9) C(10)-C(9)-C(8) C(10)-C(9)-H(9A) C(8)-C(9)-H(9A) C(10)-C(9)-H(9B) C(8)-C(9)-H(9B) H(9A)-C(9)-H(9B) O(4)-C(10)-O(3) O(4)-C(10)-C(9) O(3)-C(10)-C(9) C(4)-N(1)-H(1A)

118.9 119.6(2) 120.2 120.2 120.2(2) 120.01(18) 119.81(18) 119.3(2) 120.4 120.4 122.0(2) 119.0 119.0 109.5 109.5 109.5 109.5 109.5 109.5 125.19(18) 116.89(18) 117.92(16) 115.34(16) 108.4 108.4 108.4 108.4 107.5 123.91(18) 122.39(18) 113.70(16) 109.5

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Bond angle

Values

Bond angle

Values

C(4)-N(1)-H(1B) H(1A)-N(1)-H(1B) C(4)-N(1)-H(1C)

109.5 109.5 109.5

H(1A)-N(1)-H(1C) H(1B)-N(1)-H(1C) C(10)-O(3)-H(3A)

109.5 109.5 113.8(16)

Symmetry transformations used to generate equivalent atoms:

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Table 3

Torsion angle

Values

C(6)-C(1)-C(2)-C(3) C(7)-C(1)-C(2)-C(3) C(1)-C(2)-C(3)-C(4) C(2)-C(3)-C(4)-C(5) C(2)-C(3)-C(4)-N(1) C(3)-C(4)-C(5)-C(6) N(1)-C(4)-C(5)-C(6) C(2)-C(1)-C(6)-C(5) C(7)-C(1)-C(6)-C(5) C(4)-C(5)-C(6)-C(1) O(1)-C(8)-C(9)-C(10) O(2)-C(8)-C(9)-C(10) C(8)-C(9)-C(10)-O(4) C(8)-C(9)-C(10)-O(3)

2.1(4) -178.7(3) -0.5(5) -1.6(4) -179.9(2) 2.1(4) -179.6(2) -1.6(5) 179.2(3) -0.4(5) 173.92(16) -6.4(2) -107.8(2) 72.3(2)

Symmetry transformations used to generate equivalent atoms:

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Table 4

D-H...A

d(D-H)

d(H...A)

d(D...A)

<(DHA)

N(1)-H(1A)...O(4)#1 N(1)-H(1B)...O(1)#2 N(1)-H(1C)...O(1) N(1)-H(1C)...O(2)#3 N(1)-H(1C)...O(3)#3 O(3)-H(3A)...O(2)#4

0.89 0.89 0.89 0.89 0.89 0.868(10)

1.96 1.91 2.40 2.47 2.21 1.670(10)

2.846(2) 2.789(2) 3.041(2) 2.980(2) 2.871(2) 2.5350(19)

171.5 168.8 129.5 116.6 131.1 175(2)

Symmetry transformations used to generate equivalent atoms: #1 x,-y-1/2,z+1/2 #2 x,-y+1/2,z+1/2 #3 -x+1,-y,-z+2 #4 -x+1,y-1/2,-z+3/2

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Table 5

Parameters

PTM crystal

KDP crystal

Plasma energy (ħωp)

21.17 eV

17.28 eV

Penn gap (Ep)

3.92 eV

2.37 eV

Fermi energy (EF)

17.24 eV

12.02 eV

5.209 x10-23 cm3

2.21 x10-23 cm3

6.01 x10-23 cm3

2.14 x10-23 cm3

Electronic polarizability (using Penn analysis) Electronic polarizability (using Clausius-Mossotti equation)

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Table 6

Wave numbers (cm-1)

Assignment

FT-IR

FT-Raman

3443

-

Amino N-H asymmetric stretching vibration (NH3+)

3350

-

Amino N-H symmetric stretching vibration (NH3+)

-

3075,3026

Aromatic rings C-H medium stretching vibration

2910

2917

Methyl C-H asymmetric stretching vibration(CH3)

2630

-

Methyl C-H symmetric stretching vibration(CH3)

-

1619

C=O stretching vibration of carbonyl group

1593

-

C=C stretching vibration

1500

-

Symmetric N-H bending vibration (NH3+)

-

1450

Methyl C-H asymmetric bending vibration (CH3)

-

1391

Methyl C-H symmetric bending vibration (CH3)

1367

-

CH2 twisting vibration

-

1321

O-H in-plane bending vibration

1035

-

Aromatic ring C-H in-plane bending vibration

1222

1212

C-O stretching vibration

-

915

O-H out-of-plane bending vibration

809

826

Aromatic ring C-H out-of-plane bending vibration

689

688

CH2 wagging

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Table 7

Nonlinear Parameters

Values

Laser beam wavelength (λ)

532 nm

Lens focal length (f)

3.5 cm

Optical path distance (Z)

70 cm

Spot-size diameter in front of the aperture (ωa)

15 nm

Aperture radius (ra)

2 mm

Incident intensity at the focus (Z = 0)

4.35 Kw/Cm2

Nonlinear refractive index (n2)

-7.40 x 10-8 cm2/W

Nonlinear absorption coefficient (β)

0.03 x 10- 4 cm/W

Third order susceptibility (χ (3))

9.84 x10-6 esu