# Spectroscopic Characterization, NLO Properties and DFT Study of Amino Acid Single Crystals of Glycine Nickel Chloride

A Shiny Febena, M Victor Antony Raj, J Madhavan

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A Shiny Febena, M Victor Antony Raj, J Madhavan. Spectroscopic Characterization, NLO Properties and DFT Study of Amino Acid Single Crystals of Glycine Nickel Chloride. Mechanics, Materials Science & Engineering Journal, 2017, 10.2412/mmse.48.92.693. hal-01500542

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# Spectroscopic Characterization, NLO Properties and DFT Study of Amino Acid Single Crystals of Glycine Nickel Chloride

A. Shiny Febena¹, a, M. Victor Antony Raj¹, J. Madhavan¹

1 – Department of Physics, Loyola College, Chennai, India

a – [shinyfebena@gmail.com](mailto:shinyfebena@gmail.com)

<figure><img src="image_2.png" /></figure>

DOI 10.2412/mmse.48.92.693 provided by [Seo4U.link](https://seo4U.link)

**Keywords.** DFT, HOMO-LUMO, TG-DTA, SHG, Kurtz and Perry powder.

**ABSTRACT.** Semi Organic nonlinear optical single crystal of Glycine Nickel Chloride was successfully grown by the Slow Evaporation Solution Growth Technique (SEST). Formation of the crystalline compound, the cell parameters and the non-centrosymmetric nature was confirmed by single crystal X-ray diffraction studies. Structural confirmation was done by identifying the vibrational modes using FT-IR spectroscopic studies. The quantum chemical analyses were performed by density functional theory (DFT) using B3LYP/6-31G (d, p) basis set. The calculated first order hyperpolarizability of GNC is $0.233 \times 10^{-30}$ e.s.u. The HOMO and LUMO energies show that charge transfer occurs within molecule. The thermal behavior was analyzed by simultaneous TG-DTA studies. The UV-visible studies were employed to examine the high optical transparency and influential optical constants for tailoring materials suitability for optoelectronics applications. The second harmonic generation (SHG) measured by the Kurtz and Perry powder technique was found to be 3.2 times that of KDP. The result suggests Glycine Nickel Chloride as a promising candidate for optical devices applications.

**Introduction.** Advanced optoelectronic technology requires nonlinear optical (NLO) materials for frequency conversion, optical modulation and optical switching [1, 2]. Efforts have been made on the amino acid mixed organic and inorganic complexes for suitable device applications. The intense charge transfer between metal and ligands causes NLO nature and good transparency in visible region and high resistance to optical damage [3, 4]. In the present work, glycine with nickel chloride formed a non-centro symmetric glycine nickel dichloride dihydrate crystals.

**Experimental Details**

**Synthesis and Solubility of GNC.** High purity Glycine and Nickel (II) chloride were used for growing single crystals of GNC. The synthesized salt was purified by repeated crystallization process. Fig. 1 shows the solubility curve of GNC. Supersaturated solution of GNC was prepared in accordance with the solubility data. A few drops of $H_2O_2$ were added to the mother solution as antimicrobial substance. Good optical grade crystals of dimension up to 9 x 2 x 4 mm³ were harvested. Fig. 2 shows the photograph of as grown GNC single crystal.
<figure><img src="image_3.png" /><figcaption>Fig. 1. The solubility curve.</figcaption></figure>

<figure><img src="image_4.png" /><figcaption>Fig. 2. Photograph of as grown crystal.</figcaption></figure>

## Results and Discussion.

**X-ray diffraction analysis.** Among the grown crystals of GNCwell-shaped, transparent, single crystal was selected and it was subjected to single crystal XRD analysis usingENRAF NONIUS CAD4 X-ray diffractometer with MoKα radiation at room temperature. From the analysis data it was observed that the crystal belongs to monoclinic crystal system having non-centrosymmetry with P21 space group. The details of crystal parameters are summarized in Table 1. XRD pattern of GNC is shown in Fig. 3. Theoretically Simulated XRD pattern of GNC single crystal with indexed peak is given in Fig. 4. Both the patterns coincide well.

**Computational Details and Molecular Geometry.** The optimized molecular structure of GNC and corresponding vibrational harmonic frequencies were calculated using Beckee-3-Lee-Yag-Parr (B3LYP) combined with 6-31 G(d, p) basis set [5]. The optimized molecular structure of the isolated GNC molecule is calculated using Density Functional Theory at B3LYP/6-31 level is shown in Fig. 5.

**Vibrational assignments.** It is found that GNC molecule has 19 moieties and is in stable conformation with C1 symmetry then exhibits 51 normal modes of vibrations. The normal modes of GNC is distributed amongst the symmetry species as

$$ \Gamma_{3N-6} = 35A' \text{ (in-plane)} + 16A'' \text{ (out-of-plane)} \text{ respectively.} $$

<figure><img src="image_5.png" /><figcaption>Fig. 3. XRD spectrum of GNC.</figcaption></figure>
<figure><img src="image_6.png" /><figcaption>Fig. 4. Theoretically simulated XRD pattern.</figcaption></figure>

<table><caption>Table 1. Crystal parameters of GNC.</caption><thead><tr><th>Empirical Formula</th><th>C<sub>2</sub>H<sub>9</sub>C<sub>12</sub>NNiO<sub>4</sub></th><th colspan="2">Unit cell dimensions</th></tr></thead><tbody><tr><td>Formula weight</td><td>240.71</td><td>a = 8.183 Å</td><td>α = γ=90°</td></tr><tr><td>Wave length</td><td>0.71073 nm</td><td>b = 5.480 Å</td><td>β=90.97°</td></tr><tr><td>Crystal system, Space group</td><td>Monoclinic P2<sub>1</sub></td><td>c = 8.315 Å</td><td></td></tr></tbody></table>

<figure><img src="image_7.png" /><figcaption>Fig. 5. Atomic numbering system.</figcaption></figure>

<figure><img src="image_8.png" /><figcaption>Fig. 6. Experimental FT-IR.</figcaption></figure>

**FT-IR Analysis.** The FT-IR spectrum was recorded in the range 500 cm⁻¹ to 4000 cm⁻¹, using KBr pellet technique on IFS 66V FT-IR Spectrometer. Recorded FT-IR spectrum is shown in Fig. 6.

**C-N vibrations.** The stretching vibration bands of C-N ring occur in the region 1600 cm⁻¹-1500 cm⁻¹[6]. The theoretical and experimental peaks appear at 1500 cm⁻¹ and 1496 cm⁻¹ respectively.

**NH₂ vibrations.** The NH₂ asymmetric stretching vibrations [7] give rise to a strong band in the region 3390±60 cm⁻¹ and the symmetric NH₂ stretching is observed as weak band in the region 3210±60 cm⁻¹. The theoretical asymmetric stretching appears at 3359 cm⁻¹ and 3422 cm⁻¹ and the experimental value coincides well at 3378 cm⁻¹.

**C-Cl vibrations.** The band at 366 and 367cm⁻¹ is assigned for C-Cl in-plane bending for FT-IR 144 cm⁻¹ and 142 cm⁻¹ is for out-of-plane bending vibrations for FT-IR [8]. The vibrational assignments of fundamental modes of GNC by DFT methods are reported in Table 2.

**Hyperpolarizability.** In the second-order NLO materials design Molecular hyperpolarizability β is an important key factor [9, 10]. The calculated first order hyperpolarizability of GNC is 0.233 x 10⁻³⁰ e.s.u.
**HOMO and LUMO analysis.** The HOMO–LUMO energy gap of GNC is calculated at B3LYP/6-31G (d, p) levels are shown in Fig. 7.

$$ \text{HOMO energy (B3LYP)} = -0.272\text{a.u.} $$

$$ \text{LUMO energy (B3LYP)} = -0.046\text{ a.u.} $$

$$ \text{HOMO-LUMO energy gap (B3LYP)} = 0.226\text{ a.u.} $$

<table><caption>Table 2. Selected Experimental and Calculated B3LYP/6-31 G (d, p) level of vibrational frequencies of GNC.</caption><thead><tr><th rowspan="2">No.</th><th colspan="2">Frequency cm<sup>-1</sup></th><th rowspan="2">Spectroscopic assignment</th></tr><tr><th>B3LYP</th><th>Expt.</th></tr></thead><tbody><tr><td>1.</td><td>515.9829</td><td>516</td><td>COO<sup>-</sup> d+CCl st</td></tr><tr><td>2.</td><td>655.1160</td><td>661</td><td>COO<sup>-</sup> d +NH opd</td></tr><tr><td>3.</td><td>691.5787</td><td>674</td><td>NH opd+NH<sub>2</sub> wag</td></tr><tr><td>4.</td><td>875.2665</td><td>887</td><td>CH<sub>3</sub> opb</td></tr><tr><td>5.</td><td>953.3112</td><td>913</td><td>C=O opd</td></tr><tr><td>6.</td><td>1099.547</td><td>1029</td><td>OH ipb</td></tr><tr><td>7.</td><td>1165.119</td><td>1113</td><td>II CH ipd</td></tr><tr><td>8.</td><td>1265.0148</td><td>1254</td><td>COO<sup>-</sup> st&b</td></tr><tr><td>9.</td><td>1456.8423</td><td>1447</td><td>COO<sup>-</sup> sym st</td></tr><tr><td>10.</td><td>1500.4299</td><td>1496</td><td>NH<sub>3</sub><sup>+</sup> sym d+CN st</td></tr><tr><td>11.</td><td>1633.7591</td><td>1622</td><td>NH<sub>3</sub><sup>+</sup> asy d</td></tr><tr><td>12.</td><td>2314.5824</td><td>2029</td><td>CH vib(IR)</td></tr><tr><td>13.</td><td>3359.1695</td><td>3373</td><td>NH<sub>3</sub><sup>+</sup> asy st</td></tr></tbody></table>

**SHG efficiency studies.** A Q-switched Nd: YAG laser beam of 1064nm wavelength with 6.5mJ input power, 8ns pulse width was used. SHG was confirmed by the emission of green light. Using reference material as potassium dihydrogen phosphate (KDP), the output of SHG signal was compared and found that the SHG conversion efficiency of GNC is 3.2 times that of KDP.

<figure><img src="image_9.png" /><figcaption>Fig. 7. HOMO – LUMO plot of GNC at B3LYP/6-31 G (d, p).</figcaption></figure>
**Optical absorption spectrum.** The optical absorption spectral analysis of GNC was recorded between 190nm and 1100nm. It is evident that GNC crystal has UV cut off at 236 nm. The recorded absorption spectrum is shown in Fig. 8.A graph to estimate the direct band gap valuehas been plotted between photon energy and (αhv)² where α is the absorption coefficient and hv is the energy of the incident photon. From the Fig. 9, the band gap energy is found to be 3.27 eV.

**Thermo gravimetric analysis.** The weight loss was observed in four steps. In the first stage the weight loss starts at 44.4°C and completes at 175°C this may be due to adsorption of water molecules as the loss is recorded as 8.47%. On further heating, the second mass loss starts at 175°C and ends at 375°C. The maximum weight loss of 48.89% is observed in this stage. The third and fourth stage extends from 375°C to 910 °C with a total weight loss of 25.86%. The DTA curve shows sharp endothermic peaks which are in good agreement with TGA trace. TGA and DTA graphs are shown in Fig. 10.

<figure><img src="image_10.png" /><figcaption>Fig. 10. TGA and DTA curve of GNC crystal.</figcaption></figure>

**Summary.** In this work, report on the preparation, growth, and the characterization of Single crystal of an aminoacid based nonlinear optical material GNC have been reported. XRD data indicates the monoclinic structure of GNC.FT-IR analysis confirmed the functional groups. The UV-Vis spectrum reveals minimum absorption in the entire visible region. Thermal stability with high power efficiency exhibits the potential of GNC in the field of laser and opto-electronic device fabrications.

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Cite the paper

A. Shiny Febena, M. Victor Antony Raj, J. Madhavan, (2017). *Spectroscopic Characterization, NLO Properties and DFT Study of Amino Acid Single Crystals of Glycine Nickel Chloride*. *Mechanics, Materials Science & Engineering*, Vol 9. doi 10.2412/mmse.48.92.693