Interpretation of structural, spectral and nonlinear optical properties of a new semiorganic crystal: Rubidium bis(2-methyllactato) borate monohydrate

Journal Pre-proof Interpretation of structural, spectral and nonlinear optical properties of a new semiorganic crystal: Rubidium bis(2-methyllactato) borate monohydrate Gokila G, Aarthi R, Ramachandra Raja C

PII:

S0030-4026(20)30158-3

DOI:

https://doi.org/10.1016/j.ijleo.2020.164324

Reference:

IJLEO 164324

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Optik

Received Date:

19 December 2019

Accepted Date:

27 January 2020

Please cite this article as: G G, R A, C RR, Interpretation of structural, spectral and nonlinear optical properties of a new semiorganic crystal: Rubidium bis(2-methyllactato) borate monohydrate, Optik (2020), doi: https://doi.org/10.1016/j.ijleo.2020.164324

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Interpretation of structural, spectral and nonlinear optical properties of a new semiorganic crystal: Rubidium bis(2-methyllactato) borate monohydrate Gokila. G, Aarthi. R and Ramachandra Raja. C*

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Government Arts College (Autonomous), Kumbakonam 612002, Tamilnadu, India

Abstract

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Rubidium bis (2-methyllactato) borate monohydrate (RbMB) was developed by adopting slow solvent evaporation technique. Good crystalline nature of RbMB is confirmed by powder X-ray

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diffraction analysis. The optical transparency window is observed from 190 nm to 1100 nm. FTIR and FT-Raman spectral analysis endorses the formation of RbMB crystal. Thermal stability of RbMB extends upto 134 0C. Molecular structure of RbMB crystal is interpreted

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through the observed chemical shifts through 1H NMR and 13C NMR spectroscopy. The intermolecular interactions between organic and inorganic moieties are well established. These

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intermolecular interactions and electron delocalization enhances the third order nonlinear susceptibility (χ3) value and is found as 3.75354. X10--6 esu. The self-defocusing and reverse saturable absorption nature gives negative non-linear refractive index (n2) and positive nonlinear

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absorption co-efficient (β). This made RbMB a suitable candidate for using in Q-switching, optical pulse shorteners and optical energy limiters applications. Keywords: Crystal growth; Crystal structure; NMR spectroscopy; Z-scan analysis

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1.Introduction The fast developments in the field of optoelectronics and photonics creates a demand in developing new and better nonlinear optical (NLO) crystals. These crystals finds greater applications in various fields [1-5]. The structure property relationship is the most important factor to develop an efficient NLO crystal. Combining the organic materials nonlinear optical efficiency and inorganic materials physical stability by choosing a proper precursor results in the formation of favourable semiorganic NLO crystal. Based on this view, authors made an attempt to develop 2-methyllactic acid based crystals. Four new 2-methyllactic acid based crystals were

developed and the solved structures were reported by the authors [6-9]. Among the structures reported, Rubidium bis(2-methyllactato)borate monohydrate crystal is characterized using various characterization techniques and the structure-property relationship is reported in this article. The crystal structure consists of one 2-methyllacato borate anion, one rubidium cation and a water molecule. O-Rb…O and O-H…O hydrogen bonded intermolecular interactions

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present in the RbMB structure ensures enhanced (3).

Figure 1: Molecular structure of RbMB crystal [6]

2.Materials and methods RbMB was prepared by reacting 2-methyllactic acid, boric acid and rubidium carbonate in 4:2:1 molar ratio by using deionized water as solvent. The mixture is stirred well and filtered to remove impurities. The filtered solution is kept closed in a beaker using perforated paper and left

to stand at room temperature. Good quality RbMB crystals were harvested over a period of fifty days.

3.Results and discussion

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3.1 Structural analysis The structure of RbMB was solved and reported by the authors [6]. It crystallizes in

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monoclinic system with a centrosymmetric space group P21/n. The molecular structure of RbMB crystal is shown in fig.1.

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XPERT-PRO powder X-ray diffractometer with Cukα radiation (λ =1.5418 A0) is employed to record the Powder XRD pattern of RbMB crystal and is displayed in fig.2. The observed sharp

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intense peaks establishes the good crystalline quality of RbMB. Rietvelt index software package is employed to index the diffraction pattern. The lattice parameters were calculated using

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the reported values

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Rietveld unit cell package and is presented in table 1. The calculated values matches well with

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011

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022 014

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Intensity

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460

346

335

206

025 116

132

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031 130

011 020 022 044

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2 theta(Degree)

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Figure:2 Powder XRD pattern of RbMB crystal

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Table:1 Lattice parameter of RbMB crystal

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Lattice parameters a(Å) b(Å) c(Å) β0 V(Å3)

Single Crystal XRD

Powder XRD

8.3075 10.448 15.5630 92.202 1349.92

8.31269 10.44124 15.55962 92.195 1349.50

3.2 Linear transmission analysis Linear optical transmission bandwidth of RbMB crystal is recorded uisng PERKIN ELMER Lambda 35 UV-Vis-NIR Spectrophotometer and is depicted in fig.3. The cutoff wavelength is observed at 190 nm and it is transparent throughout the region tested. The wide transmission

bandwidth of RbMB gives more applications in optoelectronic field. Since, it is transparent in entire visible region it can generate all wavelengths between 190 to 1100 nm by frequency mixing process. Also, this crystal is suitable to produce third harmonic of Nd:YAG wavelength

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1064 nm by frequency tripling process.

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Transmittance(%)

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190nm 0

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600

800

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wavelength (cm )

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Figure 3: Linear transmission Spectrum of RbMB crystal

3.3 Vibrational analysis Figure 4 and 5 displays the FTIR and FTRaman spectra of RbMB crystal. The peak noticed in FTIR spectrum at 3579 cm-1 and 3488 cm-1 is attributed to the stretching vibrations of OH. This

confirms the presence of water molecule in crystal structure. The vibrations of functional groups such as C=O, COO-, B-O were observed and presented in the table 2. Observed vibrations endorses the formation of RbMB molecule and is presented in table 2. Vibrational assignments were made using the literature [10-17].

Table 2: Vibrational spectral assignments of RbMB crystal Wavenumber (cm-1)

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IR

Assignments Raman

OH stretching vibration

1716

1733

1681,1653,1591,1548

1455

CH3 stretching vibration C=O stretching vibration

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2900 - 2700

COO- stretching vibration

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3290 - 2660

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3579, 3488

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1332,1216,1196,979,931,888, 1342,1215,1188,1011,978,934,880, B-O stretching vibration 779,696 772,705 610

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448,428

B-O bending vibration

593

C=O bend

426

C=O out of plane bending

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592,475

614

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60

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Transmittanace(%)

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500

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1500

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2500

3000

3500

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Wavenumber(cm )

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Figure:4. FTIR Spectrum of RbMB crystal

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Raman intensity

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Wavenumber(cm )

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Figure:5. FT-Raman Spectrum of RbMB crystal

3.4 Thermal Analysis

The TGA-DSC plots of the RbMB is given in fig.6. The crushed sample of grown crystal with initial mass of 8.393 mg was used for thermal analysis. The initial weight loss observed between 134 0C and 151 0C is due to the liberation of crystal water. The weight losses observed between

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the temperature ranges 151 0C - 362 0C, 362 0C – 515 0C are due to the decomposition of 2methyllactic acid group and borate group respectively. The endothermic peaks are in agreement with the decomposition behavior.

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Heat flow(mW)

TG DSC

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Weight(%)

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Temperature (degree celcius)

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3.5 NMR Spectral analysis

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Figure 6: TGA/DSC curve of RbMB crystal

Bruker 300MHZ (ultrashield)TM instrument is employed to record 1H and

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C NMR Spectra of

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RbMB crystal and is depicted in fig. 7 and 8 respectively. The DMSO is the solvent used. Figure 7 shows 1H NMR spectrum, the signal observed at 1.156 ppm and 1.153 ppm is attributed to the CH3 protons and is shifted towards lower ppm when compared with CH3 protons signal of pure 2-methyllactic acid (1.497 ppm) [18]. O-Rb…O intermolecular interactions (fig.1) creates more electron density near CH3 protons results in shielding effect and this results in shifting of signal

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towards lower ppm. The signals observed at 2.507 ppm and 3.379 ppm is attributed to DMSO solvent and water.

In 13C NMR spectrum (fig. 8), methyl group carbon (C3, C4, C7 and C8) signals are

observed at 27.28 ppm and 27.17 ppm. The chemical shift observed at 75.53 ppm is due to C1 and C5 carbon atoms of RbMB (fig.1) and for the same it is appeared at 72.33 ppm in pure 2-methyllactic acid [19]. The electronegative groups O1-B1 and O4-B1 near C1 and C5 pulls the electrons towards itself from C6 and C2 results in the occurrence of deshielding effect results in

shifting of signal towards higher ppm. The signal observed at 181.86 ppm is assigned to C2 and

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C6 carbons.

Figure 7: 1H NMR Spectrum of RbMB crystal

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Figure 8:

NMR Spectrum of RbMB crystal

3.6 Z-Scan analysis

Third order NLO parameters of RbMB crystal was predicted using is Z-Scan technique and calculated using the formula found in the literature [20]. He-Ne laser (632.8 nm) with 20 mW of

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intensity using a lens with a focal length of 7.5 cm is used to record the closed and open aperture trace of RbMB crystal and is depicted in fig.9 and 10. The closed aperture trace (fig.9) shows pre-focal peak followed by the post focal valley establishes self-defocussing behaviour of RbMB crystal and gives negative n2 = -2.21378X10-10 cm2/W. This made RbMB a suitable candidate in several photonic applications [21]. The open aperture trace of RbMB (fig.10) shows the minimum transmittance near the focus (Z=0) and it pronounces the reverse saturable absorption behavior of RbMB results in positive β = 1.3260X10-3 cm/W. This made RbMB a suitable

candidate for optical limiting applications [22,23]. χ3 value depends prominently on the intermolecular interactions and electron delocalization in the molecular structure. In RbMB crystal structure 2-methyllactato borate anion is linked to rubidium cation and water molecule through O-Rb…O and O-H…O hydrogen bonded intermolecular interactions [24]. These interactions promotes charge transfer between anion and cation which in turn enhances the molecular hyperpolarization. The presence of unpaired electron in the carboxylate group promotes electron delocalization which results in enhanced χ3 value of RbMB and is 3.75354.

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X10--6 esu. The χ3 values of some reported crystals were given in table 3.

Third order susceptibility (χ3)

RbMB

3.7. X10--6 esu

LMBNA

3.8 X10-13 esu

KDNB

3.0 X10-8 esu

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4BPTS

References

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Crystal

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Table: 3 Comparison of χ3 value of RbMB crystal with some third order nonlinear optical crystals

Present work [25] [26] [27]

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Normalized Transmittance

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Figure 9: Closed aperture traces of RbMB crystal

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4. Conclusion

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Figure 10: Open aperture traces of RbMB crystal

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RbMB crystal was grown through slow solvent evaporation technique. Indexed PXRD pattern establishes the good crystalline nature of RbMB. Linear optical transmission bandwidth is observed from 190 nm to 1100 nm. Vibrations of functional groups were observed and assigned and it clearly establishes the formation of RbMB molecule. Thermal stability of the crystal extends upto 134 0C. The molecular structure of RbMB is established through 13C and 1H

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NMR spectroscopy. The O-Rb---O and the influence of B-O groups over organic moiety is established through observed chemical shifts and in turn endorses the formation of RbMB crystal. The enhanced χ3 value of RbMB ensures the presence of O-Rb…O and O-H…O hydrogen bonded intermolecular interactions in the crystal structure.

Conflict of interest We wish to confirm that there are no known conflicts of interest associated with this publication and there has been no significant financial support for this work that could have influenced its outcome.

Funding: No funding was received for this work.

Acknowledgments

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The authors thank the Sophisticated analytical instruments facility (SAIF), Indian

Institute of Technology (IITM),Chennai for providing single crystal XRD and FT-Raman

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spectral analysis. Authors gratefully acknowledge the instrumentation centre of St.Joseph’s college, Trichy for recording UV-Vis –NIR, FTIR and SASTRA university for providing

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powder XRD, TGA/DSC, NMR spectra. Also, the authors place a special thanks to Dr G.vinitha , VIT,Chennai for providing them with third order nonlinear testing facility for recording Z-scan

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measurement

References [1] J.N. Woodford, C.H. Wang and Y Jen Alex K, Chem. Phys. 271 (2001) 137. [2] O.P. Singh, Y.P. Singh, N. Singh and N.B. Singh, J. Crystal Growth 225 (2001) 470. [3] J.D. Bierlein, L.K. Cheng, Y. Wang and W. Tam, Appl. Phys. Lett. 56 (1990) 423.

of

[4] G.S. Bahra, P.A. Chaloner, L.M. Dutta, W. Healy and P.B. Hitchcock, J. Crystal Growth 225 (2001) 474. [5] L. Zhendong, W. Baichang and S. Genbo, J. Crystal Growth 178 (1997) 539.

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[6] G. Gokila, A. Thiruvalluvar and C. Ramachandra Raja, IUCrData (2019) 4, x190039

[7] G. Gokila, A. Thiruvalluvar and C. Ramachandra Raja, IUCrData (2019) 4, x190982.

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[8] G. Gokila, A. Thiruvalluvar and C. Ramachandra Raja, IUCrData (2019) 4, x190202.

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[9] G.Gokila, A. Thiruvalluvar and C.Ramachandra Raja, IUCR Data (2019) 4, x190593 [10] R.carballo,B.Covelo,E.Garcia-Martinez,E.M.Vaz Lopez,A.Castineiras,J.Niclos polyhedron 22, 1051 (2003)1051.

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[11] Izabella irsai,Alexandru lupan,Cornelia Majdik,Radu Silaghi-Dumitrescu STUDIA UBB CHEMIA,LXII,4,Tom 2, 495 (2017).

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[12] S.Stella Mary,S.Shahil Kirupavathy,P. Mythili,P. Srinivasan,T. Kanagasekar and R.Gopalakrishnan, Spectrochim. Acta A 71, 10 (2008). [13] Neeti Goel,Nidhi sinha,and Binary Kumar Materi, Res. Bulle. 48, 1632(2013). [14] S.Dhanuskodi,and K.Vasantha Spectrochim. Acta A 61, 1777(2005).

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[15] Roman Holomb,Wu Xu,Henrik Markusson,Patrik and Johansson,Per Jacobsson J.Phys.Chem A, 110, 11467 (2006). [16] S.Dhanuskodi,and P.A.Angeli Mary , J. Cryst. Growth 253, 424 (2003). [17] T.Balakrishnan,G.Bhagavannarayana,and K.Ramamurthi Spectrochim. Acta Part A 71, 578(2008). [18] https://sdbs.db.aist.go.jp/sdbs/cgi-bin/direct_frame_top.cgi [19] https://sdbs.db.aist.go.jp/sdbs/cgi-bin/direct_frame_top.cgi

[20] T. Thilak, M. B. Ahamed and G. Vinitha, Opt. Int. J. Light Electron Opt.,124, 4716 (2013). [21] Manikandan, T.C. SabariGirisun, R. Mohandoss, S. Dhanuskodi, and S. Manivannan, Opt. Spectrosc. 117, 469 (2014). [22] J. Wang and W. J. Blau, J. Opt. A: Pure Appl. Opt.,11, 024001 (2009). [23] Z. Henari, W. J. Balua, L. R. Milgrom, G. Yahyoglu, D. Philips and J. A. Lacey, Chem. Phys. Lett., 267, 229 (1997).

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[24] Chen Lei, Zhihua Yang, Bingbing Zhang, Ming-Hsein Lee, Qun Jing, Zhaohui Chen, XuChu Huang, Ying Wang, Shilie Pan and Muhammad Ramzan Saeed Ashraf Janjua Phys. Chem.16, 20089 (2014).

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[25] Zhihua sun,Tianliang chen,Ning-ning cai,Jing-wei chen,Lina Li,Yan Wang,Junhua Luo and Maochun Hong New J.Chem.,35, 2804 (2011).

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[26] P.Karuppasamy,V.Sivasubramani,M.Senthil pandiyan and P.Ramasamy Rsc Adv., 6 105 (2016).

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[27] K. Sivakumar, Saravana Kumar, R. Mohan Kumara, R. Kanagadurai, and S. Sagadevan, Mater. Res. Bull, 19, 937 (2016).