Synthesis, structural and spectral characterization of a novel NLO crystal N,N′-diphenylguanidinium picrate: diacetone solvate

Accepted Manuscript Synthesis, structural and spectral characterization of a novel NLO crystal N,N’diphenylguanidinium picrate: diacetone solvate

T. Shanmugavadivu, M. Dhandapani, S. Naveen, N.K. Lokanath PII:

S0022-2860(17)30597-5

DOI:

10.1016/j.molstruc.2017.05.015

Reference:

MOLSTR 23756

To appear in:

Journal of Molecular Structure

Received Date:

22 February 2017

Revised Date:

04 May 2017

Accepted Date:

04 May 2017

Please cite this article as: T. Shanmugavadivu, M. Dhandapani, S. Naveen, N.K. Lokanath, Synthesis, structural and spectral characterization of a novel NLO crystal N,N’-diphenylguanidinium picrate: diacetone solvate, Journal of Molecular Structure (2017), doi: 10.1016/j.molstruc. 2017.05.015

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ACCEPTED MANUSCRIPT Graphical abstract

ACCEPTED MANUSCRIPT Highlights 

DPGPD crystal belongs to monoclinic system with Cc space group



UV-Visible spectroscopy confirms charge transfer



DPGPD crystal is stable up to 172 ᵒC



SHG efficiency is 0.6 times greater than KDP



First order hyperpolarizability is 6.6 times greater than KDP

ACCEPTED MANUSCRIPT Synthesis,

structural

and

spectral

characterization

of

a

novel

NLO

crystal

N,N’-diphenylguanidinium picrate : diacetone solvate T. Shanmugavadivua , M. Dhandapania,*, S. Naveen b, N. K. Lokanathc,# a

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

College of Arts and Science, Coimbatore-641020, Tamil Nadu, India b

Institution of Excellence, University of Mysore, Mysuru-570023, India

c*

Department of Studies in Physics, University of Mysore, Mysuru-570023, India

Corresponding

authors'

Email:

*[email protected],

#[email protected]

mysore.ac.in Abstract An organic NLO active material N,N’-diphenylguanidinium picrate: diacetone solvate (C13H14N3+. C6H2N3O7-. 2C3H6O) (DPGPD) was synthesized and single crystals were grown by slow evaporation-solution growth technique at room temperature. DPGPD crystallizes in monoclinic crystal system with noncentrosymmetric space group, Cc confirmed by single crystal X-ray diffraction analysis. The presence of various functional groups was identified from FT-IR spectral analysis and the proton transfer during the formation of compound was confirmed by NMR spectroscopic techniques. The thermal stability was investigated by TG/DTA analyses. Optical transmittance was measured by UV-Vis-NIR spectroscopy and band gap energy was calculated. Photoluminescence spectrum was used to explore its applicability towards laser diodes. Dielectric property of the material was ascertained at different temperatures and it is found that the grown crystal has higher dielectric constant in low frequencies. Photoconductivity study revealed that DPGPD exhibits positive photoconductivity. SHG property was found to be 0.6 times higher than that of KDP.

ACCEPTED MANUSCRIPT Keywords: Single crystal X-ray diffraction; UV-NIR; Dielectrics; Thermal analysis; Photoluminescence; Hyperpolarizability. 1. Introduction The versatility of NLO materials in various applications such as fibre optic communication, laser engineering, terahertz generation [1], wireless optical computing and optoelectronics [2,3] have ushered enormous activity in this research area for the past couple of decades [4-6]. Second order non-linear optical susceptibilities are greatly enriched in organic crystals due to the presence of extended π-electron delocalization and charge transfer process which enhance the essential asymmetric polarizability. Noncentrosymmetry is an essential criterion for molecules having second harmonic generation (SHG) which is achieved by a noncentrosymmetric spatial charge distribution under an external electric field. The quest for newer organic molecules with enhanced dipole moment and a chiral structure is still alive. Picric acid forms many proton transfer compounds through electrostatic or hydrogen bonding interaction [7-9], due to the presence of active π and ionic bonds and high acidic character. A shrewd combination of a picric acid (Lewis acid) with a number of Lewis bases like amines has yielded numerous NLO active crystals with excellent emission of green radiation of 532 nm, useful for frequency doubling at 1064 nm [10,11]. Guanidine is an organosuperbase possessing three nitrogen atoms in which two are primary while the other one is imine nitrogen. Guanidine compounds can be easily protonated at the imine site and the presence of three electron donor nitrogen sites routes the formation of effective hydrogen bonds in the solid state structure. Hydrogen bonding interactions lead to improvised molecular hyperpolarizability and also proper molecular orientation in the crystal structure enabling high frequency conversion efficiency. The presence of Y-aromaticity in guanidine is a superior property which adds extraordinary basicity and stability to guanidines. Due to these facts, guanidinium compounds are the subject of chemical research for their role in the optoelectronic and photonic devices [12-14].

ACCEPTED MANUSCRIPT The combination of N, N’-diphenylguanidine and nitro aromatics would result not only in intensive hydrogen bonding in the structure but also, would increase the molecular hyperpolarizability together with charge transfer interaction which provides the ground state charge asymmetry of the molecule required for second-order nonlinearity. A thorough literature survey of picric acid, guanidine and their combinations shows that still synthesis and characterization of a number of combinations of picric acid with guanidine derivatives are left out. In this paper, we report the synthesis, spectral, thermal, dielectric and photoconductivity characterization of a new and novel organic NLO active N,N’-diphenylguanidinium picrate : diacetone solvate (DPGPD) along with computational calculations. 2. Experimental details Equimolar methanolic solutions of picric acid (Analytical grade-Sigma Aldrich) and N,N’diphenylguanidine (Analytical grade-TCI chemicals) were mixed and the resulting solution was stirred well at room temperature for 6 hours. A yellow colour precipitate was obtained after evaporation of the solvent. The precipitate was repeatedly recrystallized in acetone. Transparent and yellow coloured single crystals of N,N’-diphenylguanidinium picrate : diacetone solvate (DPGPD) (Fig.1(a)) were harvested after 20 days by slow evaporation-solution growth technique. The chemical reaction is shown below.

ACCEPTED MANUSCRIPT The crystal structure of DPGPD was established by single crystal X-ray diffraction (SXRD) analysis. The X-ray intensity data were collected at a temperature of 296 K on a Bruker Proteum2 CCD diffractometer equipped with an X-ray generator operating at 45 kV and 10 mA, using CuKα radiation of wavelength 1.54178 Å. A complete data set was processed using SAINT PLUS [15]. The structure was solved by direct methods and refined by full-matrix least squares method on F2 using SHELXS and SHELXL programs [16]. All the non-hydrogen atoms were revealed in the first difference Fourier map itself. All the hydrogen atoms were positioned geometrically (C–H = 0.93 Å, O–H = 0.82 Å) and refined using a riding model with Uiso(H) = 1.2 Ueq and 1.5 Ueq (O). The geometrical calculations were carried out using the program PLATON [17]. The molecular and packing diagrams were generated using the software MERCURY [18]. Crystallographic data of the structure have been deposited with the Cambridge crystallographic data centre (CCDC NO: 1524285). The UV-Vis absorption-solution spectrum of DPGPD (in acetone) was recorded in the spectral region 200-800 nm using JASCO V-770 spectrophotometer. The optical transmittance spectrum was recorded using UV-vis-NIR (JASCO (V-570) spectrophotometer in the region of 200-1200 nm using a solid sample. The FT-IR spectrum was recorded in the region of 4000-400 cm-1 by using SHIMAZDU IR Affinity-I FT-IR spectrophotometer. Both 1H and

13C

Nuclear

magnetic resonance (NMR) spectroscopic measurements were performed in a Bruker 400 MHz spectrometer at 20 oC using DMSO-d6 as solvent. Thermal stability of DPGPD crystal was carried out under nitrogen atmosphere at a heating rate of 10o C/min by using TG/DTA: SDT Q600 V20.9 Build 20 analyzer. Dielectric study was carried out at different temperatures by using Hioki 353250 LCR meter in the frequency range of 50Hz - 5MHz. Photoconductivity studies were undertaken at room temperature using Keithley (6517B) electrometer. Halogen lamp (100-W) containing iodine vapour and tungsten filament was used as a source. The NLO property of the material was assessed by Q switched high energy Nd:YAG laser Quanta Ray Model Lab-170-10. Optimization was carried out by DFT/B3LYP/6-311G(d,p) level of basis set using Gaussian 09 program [19].

ACCEPTED MANUSCRIPT 3. Results and discussion 3.1 Single crystal X-ray diffraction analysis The summary of crystallographic data and refinement parameters are given in Table 1 and ORTEP is shown in Fig. 1(b). From SXRD analysis, it is inferred that DPGPD crystallizes into a monoclinic system with noncentrosymmetric space group Cc. The cell parameters are a=22.64 Å, b=5.79 Å, c=22.57 Å and α = 90ᵒ, β = 113ᵒ, γ = 90ᵒ with eight formula units per unit cell (Z). The asymmetric unit of DPGPD contains one diphenylguanidinium cation (DPG), one picrate anion with two molecules of acetone solvate which are held together by N-H…O hydrogen bond interactions. ORTEP clearly shows that the formation of DPGPD through proton transfer from picric acid to diphenylguanidine in which the imine site is protonated. When viewed down ‘b’ axis (Fig. 2), it is observed that the cations and anions are arranged in alternate layers where the solvent molecules are entrapped within this layer which act as a bridge between cations and anions through N-H…O and C-H…O hydrogen bonds. The –NH group of the cation forms bifurcated N-H…O hydrogen bonds with picrate anion. Thus the N10-H10 and N9-H9B act as a bifurcated hydrogen bond donors and form hydrogen bonds with D…A distance of 2.772 Å and an angle of 143ᵒ (Table 2) forming a 𝑅12[6] ring motif. Each layer is connected with adjacent layer through C2-H2…O24 association with C-O distance of 3.290 Å which forms a 1D corrugated sheets along the (001) direction (Fig. 2). The acetone molecule builds a hydrogen bonding network through N-H…O and C-H…O interactions which are parallel and perpendicular to ‘b’ axis. The methyl group hydrogens of the acetone are involved in C-H…O interactions with –NO2 group of the picrate anion, namely, C36-H36A…O27, C36-H36B…O27, C36-H36C…O31 which propagate a 1D chain along the diagonal direction of the ab plane. The Csp2-O bond length in picrate anion is in between a normal C-O single bond (1.43 Å) and a C=O double bond (1.21 Å) which is the consequence of π-orbital delocalization confirming the loss of the phenolic proton. Remarkable changes in C-O bond length and C-C-C angles are

ACCEPTED MANUSCRIPT observed due to the N+-H…O- hydrogen bonding interactions. The central carbon atom C8 in CN3 fragment of the cation has a planar geometry with Csp2 hybridisation, since the sum of N-C-N valence angles around C8 is exactly 360ᵒ. The two phenyl rings are distorted by 65.06ᵒ and 76.50ᵒ with respect to guanidinium core due to repulsion between the π-electron cloud of the phenyl ring and the Y-delocalized π-electron cloud of the guanidinium unit. In the cation, the phenyl rings are in syn-anti conformation [20] with respect to guanidine unit and it is evident from the torsion values of C3-N7-C8-N9 (0.38ᵒ), C11-N10-C8-N9 (177.18ᵒ). The C-N bond lengths C8-N10 (1.341 Å), C8-N9 (1.329 Å) and C8-N7 (1.334 Å) (Table 3) of guanidine unit lie between normal C-N single (1.47Å) and double bond (1.28 Å) length values, which clearly show the partial double bond nature of all C-N bonds around the central carbon (C8) atom due to protonation of guanidine core. This produces Y-type conjugation in CN3 fragment of the guanidine unit leading to Yaromaticity [21]. 3.2 Vibrational analysis The FT-IR spectrum of DPGPD is given in Fig. 3(a). Generally N-H stretching vibrational wave numbers occur in the region 3500-3300cm-1 [22]. The strong bands at 3459 and 3363 cm-1 are attributed to aromatic N-H and aliphatic N-H stretching vibrations in DPGPD respectively. The observed weak band at 1495 cm-1 is due to aromatic N-H bending vibration confirming the fact that bending requires less energy than stretching [22]. NH2+ stretching vibrations of secondary amines salts absorb strongly in the region 3000-2700 cm-1 and their bending vibrational modes are observed at 1620-1560 cm-1 [23]. In DPGPD, the observed band at 3184 and 1602 cm-1 are assigned for NH2+ stretching and bending modes respectively. Owing to N-H+…O- hydrogen bonding interaction between DPG cation and picrate anion, the blue shifting in NH2+ stretching vibration observed. It is also evident from the shortening of N-H bond lengths (0.86 Å) from normal N-H value (1.01 Å). The NH2+ rocking deformation mode brings about two bands observed at 1157 and 1073 cm-1 [24]. Guanidine absorbs strongly at 1685-1580 cm-1 due to stretching vibrations of C=N group [24]. The band at 1635 cm-1 is due to stretching vibration of

ACCEPTED MANUSCRIPT C=N group of guanidinium moiety of DPGP. Normally the C-N stretching of aromatic secondary amine and aliphatic amine compounds are observed in the region 1350-1250 cm-1 and 1250-1000 cm-1 [22]. The bands at 1315 and 1073 cm-1 are attributed to aromatic and aliphatic C-N stretching vibration respectively. The higher frequency of C-N absorption in aromatic C-N compared to aliphatic C-N mainly due to resonance, which increases the double bond character between the aromatic ring and the nitrogen atom. The phenolic C-O stretching frequency is normally observed in the region 1260-1000 cm-1 [22]. In DPGPD, it is observed at 1256 cm-1. The aromatic C-H stretching and bending vibrations are expected in the region 3100-3000 cm-1 and 900-600 cm-1 respectively [23].The observed band at 3060 cm-1 can be assigned to the aromatic C-H stretching. In the spectrum, the bands noticed at 698, 838 and 884 cm-1 belong to the C-H out-of-plane modes and the bands at 1256, 1157, 1073 and 1034 cm-1 for C-H in-plane modes and the skeletal vibrations involving C-C/C=C are observed at 1602 and 1495 cm-1. The NO2 asymmetric and symmetric stretching vibrations appear normally at 1554 and 1358 cm-1 respectively. The bands at 838 and 637 cm-1 are attributed to C-N stretching and CNO bending of picrate moiety respectively. Acetone shows a strong band in the region of 1720-1708 cm-1 for C=O stretching absorption [22]. In the spectrum, the absorption band at 1635 cm-1 is ascribed for C=O stretching vibration of carbonyl group in acetone. Owing to the intermolecular N-H…O hydrogen bonding between cation and carbonyl group of the solvent, considerable red shift in C=O absorption frequency is observed. The bands at 2927 and 2860 cm-1 are assigned for asymmetric and symmetric stretching vibrations of methyl group and their out-of-plane and in-plane bending modes are noticed at 1433 and 1358 cm-1 respectively. The C-CO-C skeletal vibration for acetone is observed at 1315 cm-1. 3.3 1H and 13C NMR spectral analyzes The 1H and

13C

NMR spectra are shown in Fig. 3(b) and Fig. 3(c) respectively. The 1H

NMR (DMSO-d6) spectrum exhibits five different signals. An intense singlet signal observed at δ 8.611 (s, 2H) is due to protons H20, H22 of the picrate moiety. A cluster of signals at the region δ 7-8 ppm, indicate the presence of two aromatic rings in the compound. The signal at δ 7.43 (d, 4H)

ACCEPTED MANUSCRIPT is owing to identical ortho protons (H2, H4, H12 and H16) of the two phenyl rings in the DPG cation. Similarly the signal at δ 7.32 (t, 4H) is attributed to equivalent meta protons (H1, H5, H13 and H15) and δ 7.26 (t, 2H) due to similar para protons (H6 and H14) of the two phenyl rings of cationic moiety. The weak signal at δ 3.38 (s, 2H) is due to –NH protons. The imino protons lack any signal due to their labile nature [25]. The 13C NMR spectrum shows nine distinct 13C signals which clearly prove the formation of the compound. The signal at δ 160.84 ppm indicates the presence of guanidine carbon (C8). The peak appeared at δ 153.65 (C18) indicates the carbon which is attached to the oxygen atom in the picrate moiety. The other signals at δ 141.82 (C21), δ 136.20 (C17 and C19), δ 129.53 (C20 and C22), δ 124.30 (C6 and C14), δ 123.82 (C2, C4, C12 and C16), δ 126 (C3 and C11), δ 125.23 (C1, C5, C13 and C15) are attributed to two phenyl ring carbons of the DPG cationic moiety. 3.4 UV-VIS-NIR spectral study For electro-optic devices, crystals should be free from the defects such as scattering and absorption in the NIR region [26]. The UV-Vis-NIR spectrum is shown in Fig. 4(a). From the UV-Vis-NIR spectrum, it is inferred that the DPGPD has a wide transmittance of 80% with lower cut-off wavelength at 450 nm which indicates the defect free crystalline nature of DPGPD. The crystal shows transmittance window in the region of 450-1200 nm, which is a necessary condition for the generation of second harmonic light (532 nm) from Nd:YAG laser (1064nm). The optical parameter absorption coefficient (α) was calculated by using the well known relation, α = (2.303/t) x log (1/T) where T is the transmittance of the sample and d is the thickness. The band gap of the sample is related with absorption coefficient which is given by the following relation: (αhν) = A(hν-Eg) ½

ACCEPTED MANUSCRIPT where Eg is the optical band gap and A is a constant. The optical band gap was evaluated [27] by extrapolating the linear portion of (αhν)2 in the photon energy axis (Fig. 4(b)). The band gap energy of DPGPD is 3.9 eV, which is in good agreement with the other reported diphenylguanidinium compounds [25]. The same band gap energy calculated from DFT calculation is 3.7 eV (Fig. 4(c)). The wide energy band gap indicates that the crystal has large transparency in the visible and IR region which is an essential condition for electro-optic applications. 3.5 UV-Visible absorption study The UV-Visible absorption spectroscopy is used to analyse the charge transfer phenomena in organic compounds. The UV-Vis spectrum of DPGPD is shown in Fig. 5(a). The absorption maximum of DPGPD crystal is observed at 260 nm which is attributed to n→π* transition. Then the optical absorption edge of DPGPD is red shifted to 377 nm is the clear vindication of charger transfer from the highest occupied molecular orbital (HOMO) of the donor to the vacant unoccupied molecular orbital (LUMO) of the acceptor. Thus the absorption peak at 377 nm is assigned for π→π* transition which is the charger transfer band. It is also to be noted that the absence of absorption between 500-900 nm proves DPGPD can be used as a SHG material in the visible region above 500 nm. 3.6 Photoluminescence study Photoluminescence (PL) spectral analysis finds application in lighting technologies. Normally photoluminescence phenomenon is anticipated from aromatic molecules and conjugated systems due to high degree of resonance stability. DPGPD crystal contains picrate anion with delocalized π-electrons in the aromatic ring exhibiting a large number of energy states between ground and excited states which are responsible for its luminescence spectrum. The emission spectrum of DPGPD was recorded by exciting it at 370 nm and is shown in Fig. 5(b). The emission peaks at 418 and 487 nm indicate that DPGPD has violet [28] and blue fluorescence.

ACCEPTED MANUSCRIPT 3.7 Dielectric studies Low dielectric constant materials are robustly applicable in microelectronic industries due their lower power consumption, and their ability in reducing the crosstalk between nearby interconnects [29]. The dielectric constant of the material is directly proportional to the polarization of the different constituents (atoms or ions) of the solids and interrelated with electrooptic property of the material. The dielectric constant was calculated using the formula,

𝜀r =

𝐶𝑑

,

εo A

where C is the capacitance, d is the thickness of the sample, A is the cross-sectional area of the crystal and 𝜀o is the free space permittivity (8.854 x 10-12 F m-1). From Fig. 6(a) and 6(b), it is clear that both the dielectric constant and dielectric loss are decreasing with increase in frequency and it has higher value at low frequency. In the high frequency region both parameters fairly remain constant. The higher value of dielectric constant at low frequency is mainly attributed to space charge polarization, orientational, ionic and electronic polarization mechanisms of molecular dipoles and the low value at higher frequencies is owing to loss of space charge polarizations [30]. The dielectric constant increases with increase in temperature and its value is found to be 275 at 393 K. The DPGPD crystal exhibits large ionic and electronic polarization due to occurrence of enormous N-H…O and C-H…O interactions. Increase in temperature leads to diminishing of the hydrogen bonding interactions, which is responsible for higher dielectric constant value at high temperature. The low value of dielectric loss suggests that the DPGPD crystal possesses enhanced optical quality with lower power consumption. Low dielectric constant of the material reduces the RC delay, and thus permits a higher bandwidth in the terahertz (1012 Hz) region. The low value of dielectric loss at high frequency clearly suggests that DPGPD can be used for storing large

ACCEPTED MANUSCRIPT quantity of charges with minimum energy dissipation and hence it will be useful in capacitor technology. 3.8 Photoconductivity study Photoconducting property of DPGPD crystal was examined in order to analyse its application in the field of nonlinear optics and photonic devices. When the electromagnetic radiation is absorbed by the material, an electrical conductivity is generated due to excitation of photo-induced electron from valence to conduction band which raises mobile charge carriers. The production of excess number of photo generated charge carriers lead to increase the photoconductivity of the material. The variation of photo current (Ip) and dark current (Id) with applied field in DPGPD is shown in Fig. 6(c). It is observed that both photo current and dark current increase linearly with respect to applied voltage. The graph shows that the photoconductivity is greater than the dark conductivity at any instance, which proves the crystal exhibits positive photoconductivity. This positive photoconductivity is attributed due to the increase in the number of charge carriers, production of intrinsic centres and lack of traps within the material. The photoconductivity behaviour of DPGPD explains its capability of converting the low energy sub picosecond laser pulses into high amplitude electric pulses. 3.9 Thermal analysis The thermogram of DPGPD is shown in Fig. 7. A single stage weight loss was observed due to major decomposition of the sample into volatile products. About 58.52% of weight loss occurred between 225 to 350 ᵒC, and decomposition continues up to 600 ᵒC. In DTA curve, an endothermic peak observed at 172 ᵒC is due to the melting point of the DPGPD. The exothermic peak at 291 ᵒC in DTA is due to the bulk degradation of the material. This observation matches with the decomposition observed in TG curve. Thus the thermal analysis study endorses the applicability of DPGPD for any optical device below 172 ᵒC.

ACCEPTED MANUSCRIPT 3.10 SHG study A Q-switched 8 ns Nd:YAG laser beam of wavelength 1064 nm, 8 mm diameter with 10 Hz repetition rate and the 6.3 mJ/pulse energy was used in Kurtz and Perry powder technique. The emission of green light radiation (532 nm) at fundamental wavelength of 1064 nm confirms the second harmonic generation property of DPGPD crystal. The SHG efficiency was found to be 0.6 times greater than that of KDP. It should be noted that the presence of intermolecular N-H+…Ohydrogen bonding networks between amino hydrogen atoms of diphenylguanidinium cation and oxygen atoms of picrate anions play an important role to achieve noncentrosymmetry, thereby enhancing the positive SHG [31]. Theoretically, the dipole moment (μ hyperpolarizability (β

Total)

tot)

and first order

of DPGPD are calculated as 13.2092 D and 6.176 x 10-30 esu and the

calculated first order hyperpolarizability of DPGPD is 6.6 times greater than that of KDP. Due to the presence of polarizable electron donor and acceptor groups, acentric nature and large first hyperpolarizability, DPGPD shows strong NLO response. 4. Conclusion A novel NLO active material DPGPD was synthesized and grown by slow evaporation technique. Single crystal XRD reveals that the grown crystal belongs to a monoclinic system with noncentrosymmetric space group Cc. The presence of acetone molecules in the crystal structure strengthens the intermolecular hydrogen bonding and substantiates noncentrosymmetry in the crystal. The absorption band at 377 nm in UV-Visible spectrum indicates charge transfer activity in DPGPD. Its lower cut-off wavelength (450 nm) and its blue emission strongly endorse its optical applications. The higher value of dielectric constant (275 at 393 K) with low frequency (1.69) and positive photoconductivity suggests its suitability towards electronic devices and sensors. Thermal analyses showed that the crystal is stable up to 172 ᵒC. Its SHG efficiency is found to be 0.6 times greater than that of KDP and theoretically first order hyperpolarizability (β Total)

is calculated as 6.176 x 10-30 esu. The hyperpolarizability of DPGPD is mainly due to the

ACCEPTED MANUSCRIPT much ease of electron delocalization from picrate to diphenylguanidinium moiety. These facts clearly attest that DPGPD can be a potential material for photonic and SHG devices applications. Acknowledgement M. Dhandapani expresses his gratitude to the University Grants Commission (UGC), New Delhi, India for the financial support (Major Research Project Grant No. F. No. 43-200/2014 (SR)). References [1] K. Akiyama, S. Okada, Y. Goto, H. Nakanishi, J. Cryst. Growth. 311 (2009) 953-955, http://dx.doi.org /10.1016/j. jcrysgro.2008.09.1. [2] D. S. Chemla, J. Zyss, Non-linear Optical properties of organic Molecules and Crystals, vol. 1, Academic Press, London, 1987. [3] Irena Matulková, Hana Solarˇová, Petr Šte ˇpnicˇka, Ivana Císarˇová, Tomáš Janda, Petr Neˇmecb,Ivan

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ACCEPTED MANUSCRIPT [28] P. Jayaprakash, M. Peer Mohamed, P. Krishnana, M. Nageshwari, G. Mani, M. Lydia Caroline, Physica B. 503 (2016) 25-31, http://dx.doi.org/10.1016/j.physb.2016.09.010. [29] P. Srinivasan, T. Kanagasekaran, N. Vijayan, G. Bhagavannarayana, R. Gopalakrishnan, P. Ramasamy, Opt. Mater. 30 (2007) 553–564, http://dx.doi.org/10.1016/j.optmat.2007.01.014. [30] K. V. Rao, A. Smakula, J. Appl. Phys. 36 (1965) 2031, http://dx.doi.org/10.1063/1.1713986. [31] G. Saravana Kumar, P. Murugakoothan, Spectrochim. Acta Part A. 131 (2014) 17-21, http://dx.doi.org/10.1016/j.saa.2014.04.059.

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Fig. 1(a) Photograph of crystal DPGPD; (b) ORTEP of DPGPD

Fig. 2 N-H…O and C-H…O interactions viewed down ‘b’ and ‘a’ axis

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Fig. 3(a) FT-IR spectrum; (b) 1H NMR spectrum; (c) 13C NMR spectrum of DPGPD

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Fig.4(a) UV-Vis-NIR spectrum of DPGPD; (b) Plot of (αhν)2 versus photon energy; (c) HOMO-LUMO energy gap of DPGPD

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Fig.5(a) UV-Visible absorption spectrum; (b) Photoluminescence spectrum of DPGPD

Fig. 6 (a)Variation of dielectric constant and (b) dielectric loss with log frequency at different temperature; (c) Photoconductivity of DPGPD

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Fig. 7 TG/DTA thermogram of DPGPD

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Table 1 Crystal data and structure refinement details of DPGPD Chemical formula

C12.50H14N3O4.50

Mr

278.27

Crystal system, space group

Monoclinic, Cc

Temperature (K)

296

a, b, c (Å)

22.6439 (4), 5.7949 (1), 22.5798 (4)

 (°)

113.144 (1)

V (Å3)

2724.45 (8)

Z

8

Radiation type

Cu K

 (mm-1)

0.89

Crystal size (mm)

0.28 × 0.26 × 0.25

Absorption correction

Multi-scan SADABS

Tmin, Tmax

0.780, 0.801

No. of measured, independent and observed [I > 2(I)] reflections

9233, 4228, 4176

Rint

0.032

(sin /)max (Å-1)

0.584

R[F2 > 2(F2)], wR(F2), S

0.031, 0.082, 1.03

No. of reflections

4228

No. of parameters

365

No. of restraints

2

H-atom treatment

H atoms treated by a mixture of independent and constrained refinement

max, min (e Å-3)

0.37, -0.16

Absolute structure parameter

0.05 (12)

Table 2 Various hydrogen bonding interactions present in DPGPD crystal Donor - H…Acceptor N(7) - H(7)…O(34) N(9) - H(9A)…O(38) N(9) - H(9B)…O(28) N(9) - H(9B)…O(29) N(10) - H(10)…O(29)

D-H 0.86 0.86 0.86 0.86 0.86

H...A 2.02 2.08 2.47 2.03 2.04

D...A 2.8081(19) 2.882(2) 3.0705(18) 2.7732(17) 2.7728(17)

< D - H...A 152 154 127 143 143

ACCEPTED MANUSCRIPT N(10) - H(10)…O(32) C(36) - H(36B)…O(27) C(36) - H(36C)…O(31

0.86 0.96 0.96

2.39 2.47 2.47

3.046(2) 3.358(3) 3.373(3)

133 154 157

Table 3 SXRD Bond length and bond angle values of DPGPD Atoms

Bond length values (Å)

Atoms

Bond length values (Å)

C1—C6

1.380

C18—O29

1.248

C1—C2

1.389

C18—C19

1.450

C1—H1

0.930

C19—C20

1.373

C2—C3

1.395

C19—N30

1.453

C2—H2

0.930

C20—C21

1.382

C3—C4

1.382

C20—H20

0.930

C3—N7

1.433

C21—C22

1.387

C4—C5

1.389

C21—N23

1.449

C4—H4

0.930

C22—H22

0.930

C5—C6

1.389

N23—O24

1.232

C5—H5

0.930

N23—O25

1.234

C6—H6

0.930

N26—O28

1.2243

N7—C8

1.334

N26—O27

1.2324

N7—H7

0.860

N30—O31

1.216

C8—N9

1.329

N30—O32

1.230

C8—N10

1.341

C33—O34

1.219

N9—H9A

0.860

C33—C35

1.486

N9—H9B

0.860

C33—C36

1.493

N10—C11

1.439

C35—H35A

0.960

N10—H10

0.860

C35—H35B

0.960

C11—C12

1.381

C35—H35C

0.960

C11—C16

1.386

C36—H36A

0.960

C12—C13

1.380

C36—H36B

0.960

C12—H12

0.930

C36—H36C

0.960

C13—C14

1.389

C37—O38

1.215

C13—H13

0.930

C37—C40

1.490

C14—C15

1.381

C37—C39

1.495

C14—H14

0.930

C39—H39A

0.960

C15—C16

1.385

C39—H39B

0.960

ACCEPTED MANUSCRIPT C15—H15

0.930

C39—H39C

0.960

C16—H16

0.930

C40—H40A

0.960

C17—C22

1.372

C40—H40B

0.960

C17—C18

1.451

C40—H40C

0.960

C17—N26

1.461

Atoms

Bond angle values (ᵒ)

Atoms

Bond angle values (ᵒ)

C6—C1—C2

120.3

C19—C18—C17

112.1

C6—C1—H1

119.9

C20—C19—C18

124.7

C2—C1—H1

119.9

C20—C19—N30

116.4

C1—C2—C3

119.2

C18—C19—N30

118.9

C1—C2—H2

120.4

C19—C20—C21

118.4

C3—C2—H2

120.4

C19—C20—H20

120.8

C4—C3—C2

120.7

C21—C20—H20

120.8

C4—C3—N7

120.8

C20—C21—C22

121.6

C2—C3—N7

118.4

C20—C21—N23

119.1

C3—C4—C5

119.5

C22—C21—N23

119.3

C3—C4—H4

120.2

C17—C22—C21

119.5

C5—C4—H4

120.2

C17—C22—H22

120.2

C6—C5—C4

120.0

C21—C22—H22

120.2

C6—C5—H5

120.0

O24—N23—O25

123.4

C4—C5—H5

120.0

O24—N23—C21

118.1

C1—C6—C5

120.2

O25—N23—C21

118.5

C1—C6—H6

119.9

O28—N26—O27

122.7

C5—C6—H6

119.9

O28—N26—C17

119.6

C8—N7—C3

124.1

O27—N26—C17

117.8

C8—N7—H7

117.9

O31—N30—O32

121.8

C3—N7—H7

117.9

O31—N30—C19

118.8

N9—C8—N7

121.5

O32—N30—C19

119.1

N9—C8—N10

118.8

O34—C33—C35

122.2

N7—C8—N10

119.7

O34—C33—C36

120.4

C8—N9—H9A

120.0

C35—C33—C36

117.4

C8—N9—H9B

120.0

C33—C35—H35A

109.5

H9A—N9—H9B

120.0

C33—C35—H35B

109.5

C8—N10—C11

122.9

H35A—C35—H35B

109.5

C8—N10—H10

118.6

C33—C35—H35C

109.5

ACCEPTED MANUSCRIPT C11—N10—H10

118.6

H35A—C35—H35C

109.5

C12—C11—C16

120.6

H35B—C35—H35C

109.5

C12—C11—N10

119.8

C33—C36—H36A

109.5

C16—C11—N10

119.7

C33—C36—H36B

109.5

C13—C12—C11

120.1

H36A—C36—H36B

109.5

C13—C12—H12

120.0

C33—C36—H36C

109.5

C11—C12—H12

120.0

H36A—C36—H36C

109.5

C12—C13—C14

119.8

H36B—C36—H36C

109.5

C12—C13—H13

120.1

O38—C37—C40

122.1

C14—C13—H13

120.1

O38—C37—C39

121.7

C15—C14—C13

119.8

C40—C37—C39

116.2

C15—C14—H14

120.1

C37—C39—H39A

109.5

C13—C14—H14

120.1

C37—C39—H39B

109.5

C14—C15—C16

120.6

H39A—C39—H39B

109.5

C14—C15—H15

119.7

C37—C39—H39C

109.5

C16—C15—H15

119.7

H39A—C39—H39C

109.5

C15—C16—C11

119.1

H39B—C39—H39C

109.5

C15—C16—H16

120.4

C37—C40—H40A

109.5

C11—C16—H16

120.4

C37—C40—H40B

109.5

C22—C17—C18

123.5

H40A—C40—H40B

109.5

C22—C17—N26

116.5

C37—C40—H40C

109.5

C18—C17—N26

120.1

H40A—C40—H40C

109.5

O29—C18—C19

123.1

H40B—C40—H40C

109.5

O29—C18—C17

124.7