Accepted Manuscript Synthesis, crystal growth and physiochemical characterization of new organic crystal: L-ornithinium dipicrate (LODP) S. Balaprabhakaran, J. Chandrasekaran, B. Babu, R. Thirumurugan, K. Anitha PII: DOI: Reference:
S1386-1425(14)01442-5 http://dx.doi.org/10.1016/j.saa.2014.09.084 SAA 12760
To appear in:
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy
Received Date: Revised Date: Accepted Date:
24 July 2014 14 September 2014 19 September 2014
Please cite this article as: S. Balaprabhakaran, J. Chandrasekaran, B. Babu, R. Thirumurugan, K. Anitha, Synthesis, crystal growth and physiochemical characterization of new organic crystal: L-ornithinium dipicrate (LODP), Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy (2014), doi: http://dx.doi.org/10.1016/j.saa. 2014.09.084
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Synthesis, crystal growth and physiochemical characterization of new organic crystal: L-ornithinium dipicrate (LODP) S. Balaprabhakaran1, J. Chandrasekaran*1, B. Babu1, R. Thirumurugan2, K. Anitha2 1
Department of Physics, Sri Ramakrishna Mission Vidyalaya College of Arts and Science,
Coimbatore - 641 020, Tamil Nadu, India. 2
Department of Physics, School of Physics, Madurai Kamaraj University, Madurai-625021,
Tamil Nadu, India *Corresponding author: Ph: +91-422-2692461, Fax: +91-422-2692676 E-mail address: [email protected] _____________________________________________________________________________ Abstract L-ornithinium dipicrate (LODP) has been synthesized and good quality single crystals were grown by slow evaporation method at room temperature. Single crystal XRD confirms that the grown crystal belongs to the monoclinic system with the noncentrosymmetric space group P21. Powder X-ray diffraction study confirms the crystalline nature of the compound. FTIR spectral
analysis
confirms
the
functional
group
in
the
synthesized
compound.
Thermogravimetric and differential thermal analyses reveal the thermal stability of the crystal. The optical absorption spectrum shows the absence of absorption between 475 nm and 800 nm. The dielectric measurements were carried out to estimate the dielectric parameters of the grown crystal in the frequency range from 50Hz to 5MHz at various temperatures. The second harmonic property has been investigated by Kurtz- Perry powder technique. The relative SHG efficiency of LODP is found to be 14.57 times greater than that of the reference material KDP. Keywords: Crystal growth, nonlinear optics, X-ray diffraction, dielectric materials, thermal analysis. _ Introduction In recent years, the various classes of organic nonlinear optical materials have been investigated worldwide and also it is preferred in many applications such as optical communications, optical switching and information storage and photonics technology [1, 2]. Due to their low cost, high nonlinearity, low dielectric constant, high flexibility, high optical
1
damage threshold and ultrafast response. Organic crystals are of special interest compared to inorganic crystals. [3-8]. Amino acids are popularly referred as the building blocks of protein. Amino acid family crystals are of great interest due to their rich nonlinear optical properties. Its specific features such as Zwitterionic nature, weak Vander Waals, hydrogen bonds and wide transmittance in the visible and UV-spectral region make them an ideal candidate for NLO applications [9, 10]. Amino acids contain protonated amino group (NH+) and deprotonated carboxylic acid group (COO-);owing to its asymmetric carbon atom most of the amino acids crystallize in a noncentrosymmetric space group [11]. The picrates are convenient for identification and quantitative analysis of organic compounds. Also it is used in human therapy such as treatment of burns, antiseptic and astringent agent. The bonding of these picrate complexes depends on the nature of the donor-acceptor system [12, 13]. Due to its Zwitterionic nature, an amino acid nonlinear optical property is increased when mixed with organic acids. Picrates are attractive candidates for the formation of salts with various organic bases. Due to this formation of the conjugated base, picrate, the value of molecular hyperpolarizability improved because of the proton transfer. Previously some of the picrate of amino acids such as diglycine picrate, L-alanine L-alaninium picrate, L-isoleucinium picrate, L-leucine L-leucinium picrate, DL-phenylalanine DL-phenylalaninium picrate and DL-methionine DL-methioninium picrate, L-asparaginium picrate, L-histidinium dipicrate dihydrate, L-tryptophanium picrate and L-Valinium Picrate were reported [14-28]. On the basis of these facts, in the present communication for the first time we describe the synthesis and characterization of Lornithinium dipicrate crystal. The grown crystals were characterized by various characterization techniques
such
as
single
crystals
XRD,
powder
XRD,
FTIR,
UV,
Dielectric,
photoconductivity, TG/DTA and powder SHG studies and the results were discussed.
Experimental Crystal growth LODP was synthesized by taking L-ornithine and picric acid in an equimolar ratio of 1:1. L-ornithine and picric acid were dissolved separately in water and acetone, stirred well for about 20minutes using a magnetic stirrer. Then, these solutions were mixed together and stirred for about one hour. The saturated solution was filtered twice using whatmann filter paper and transferred to crystallizing vessel. Top of the vessel was covered with thin plastic sheet and to 2
facilitate the slow evaporation, a few holes were made on it. For the slow evaporation of the solvent, the beaker was kept undisturbed at room temperature. Well defined yellow coloured crystals with good transparency appeared in the growth period of 15 days. The photograph of the grown crystal is shown in Fig. 1.
Results and Discussion X- Ray Diffraction Analysis The single crystal X-ray diffraction data of the title compound were collected at 293 K with graphite–monochromated Mo Kα radiation (λ = 0.071073 nm), and used Enraf–Nonius CAD-4 diffractometer with the ω-2θ scan mode. A suitable sample of size 0.26 mm x 0.21 mm x 0.18 mm was chosen and mounted on the goniometer. Lattice parameters were collected from least-squares fit of 25 reflections. A total of 11500 (5188 independent Rint = 0.0320) reflections were measured. Cell refinement and data reduction were carried out using CAD-4 EXPRESS [29] and XCAD4 [30]. The structures were solved by direct methods procedure using SHELXS97 [31] and refined by full-matrix least-squares on F2 using SHELXL -97 program [31]. All non-hydrogen atoms were anisotropically refined. The hydrogen atom positions were fixed at geometrically calculated distances to allow riding on the parent atoms to which they are attached. ORTEP diagram of LODP crystal is depicted in Fig. 2.The crystal data and details pertaining to data collection and the structure refinement are given in Table 1. The relevant bond lengths, bond angles and torsion angles are listed in Table 2. The selected hydrogen bond geometries are given in Table 3.The molecular graphics were prepared by using the ORTEP [32].The X-ray diffraction study reveals that the grown LODP crystal belongs to the monoclinic system with the noncentrosymmetric space group P21. The lattice parameter values are found to be a= 9.67 (1) Å, b = 5.26 (2) Å, c= 12.07(3) Å. Crystallographic data for the title compound is given in Table 1. The L-ornithinium dipicrate crystal structure comprises of crystallographically independent two picrate anions and one ornithinedication. Protonation occurs at the two possible amine sites in the ornithine molecule at atom N8 and N9 respectively which leads to the formation of cation and the two picrate anions have been formed by loss of one H atom at the hydroxyl group in the picric acid at atom O1A and O1B respectively, it is confirmed by the variations of the hydroxyl C__O bond distances (d (C1A__O1A) =1.256(6) Å, d (C1B__O1B) =1.256(6) Å). The ornithine residue consists of two planar groups, viz. the carboxyl group and 3
the aliphatic side chain. The plane of the aliphatic chain forms a dihedral angle of 72.17(3) ° with the carboxyl plane. The backbone conformation angle (O8__C7__C8__N8) indicates a gauge conformation [30.73 °]. The other angles,
(N8__C8__C9__C10), (C8__C9__C10__C11) and
(C9__C10__C11__N9) have fully extended trans-trans conformations [177.32 (2) °, -179.35(5) ° and 176.23(3) °] respectively. During the crystallization process, the removal of phenolic H atom from the picric acid leads to a shortening of the C1A-O1A = 1.256(6) Å and C2B-O2B = 1.256(6) Å bond lengths. These bond length values are intermediate between the typical singlebond and double-bond values, implying that the negative charge located on the phenolate O atom is delocalized. Both aromatic rings in picrate anions are good approximation with planar, maximum deviation from the least-square plane calculated by the six ring atoms is 0.008(1) Å in the anion A and 0.018(2) Å in anion B. The three nitro groups of the picrate anion A deviate from the benzene plane by 36.00(3) ° (N1A), 2.88(3) ° (N2A) and 12.42(3) ° (N3A) and in anion B the twist angles are 44.22(3) ° (N1B), 7.44(3) ° (N2B) and 27.35(3) ° (N3B) respectively. The hydrogen atoms H1 of N9 and H12 of N8 in the amine groups of the ornithinium cation forms a strong N__H…O hydrogen bonds with hydroxyl group O1A and O1B atoms of the picrate A and B anions respectively. The hydrogen atom H13 of O9 in the carboxyl group of the ornithinium cation forms a strong O__H…O intermolecular hydrogen bonds with the nitro group of O7A and O7B atoms of the picrate A and B anions respectively. Cation is linked to anion through N9__H1…O1B and O9__H13…O7B intermolecular hydrogen bonds, which leads to the formation of ring R 14. The crystal structure is stabilized by the strong N__H…O, O__H…O and weak intermolecular hydrogen bonds and also the O__H…O intramolecular hydrogen bonds. Powder X-ray diffraction study was carried out by employing JEOL-JDX 8030 X-ray diffractometer with Nickel filtered CuKα (λ=1.5405 Å) radition. The grown LODP crystal was finely powdered and it has been subjected to powder XRD analysis. Narrow peaks indicate the good crystallinity of the material. All reflections are observed and indexed at room temperature. The powder XRD pattern of the grown LODP crystal is shown in Fig. 3. The well defined Bragg’s peaks at specific 2θ angles confirmed the perfect crystalline nature of LODP single crystal.
4
FTIR Analysis FTIR spectrum of LODP crystal was recorded using PerkinElmer spectrometer in the range of 4000-400cm-1by employing KBr pellet method. The result of the room temperature FTIR spectrum of LODP crystal is shown in Fig. 4. NH3+ symmetric and asymmetric stretching vibrations were observed at 3248 and 2967 cm-1. The broad band in IR spectrum at 2967 cm-1 corresponds to OH stretching vibration. The absorptions at 1562 and 1323 cm-1 confirms the asymmetrical and symmetrical stretching vibrations of NO2 group. The carbonyl absorption at 1762cm-1 confirms the COOH and COO- groups of the compound. The strong absorption peaks at 1627cm-1 indicates the presence of primary amino group. The presence of the peak at 1414cm-1 corresponds to the symmetric stretching vibration of carboxyl group. The absorption bands at 1316 cm-1 is due to NO3 asymmetric stretching deformation. The C-N stretching vibration is identified by the absorption peak at 1084 cm-1. C-C stretching vibration is observed at 922cm-1. Absorption peaks at 1619, 1543 and 1422 cm-1 reveals the presence of aromatic C=C stretching vibration. Peak at 1162 cm-1 is assigned to the C-O stretching vibrations of picric acid. The absorption band at 478cm-1 is due to COO- rocking vibration. C-H out of plane bending vibration was observed at 787 cm-1. The presence of the above bands confirms the formation of picrate salt of L-ornithine.
UV- Visible Spectral Analysis The optical absorption spectrum of the grown LODP crystal was recorded using Perkin Elmer Lambda 35 UV –Vis spectrophotometer in the wavelength range from200 nm to 800nm. The recorded spectrum is shown in Fig. 5. The spectrum exhibits the strong absorption peak at 355 nm. The absorption peak at 355 nm is assigned to π to π* transition of the compound, which is attributed to the charge transfer of the compound [13]. Absence of absorption between 475 nm and 800 nm is an advantage, as it is the key requirement for materials possessing SHG properties. As a result, it can be used as a potential candidate for the SHG device applications in the visible region [23].
Thermal Analysis To study the thermal stability of the grown crystal TG/DTA analysis were carried out using STA 1500 thermal analyzer from room temperature to 800°C in nitrogen atmosphere at a 5
heating rate of 20°C/min. Recorded TG/DTA spectrum is shown in Fig. 6. From the figure it is clear that there is no weight loss between room temperature to 210°C and hence the crystal rejects the solvent molecules during the crystallization. TG spectrum shows that the title compound is stable up to 210°C. The major weight loss started from 205°C and ending at 244°C. In DTA there is a sharp endothermic at 211°C is assigned to melting point of the compound which are fit well with the TG spectrum. In DTA a sharp exothermic peak at 235°C is due to the major decomposition of the compound. With the temperature increasing above 300°C, volatile substances such as NO, NO2, CH4, NH3 and CO2molecules will be liberated [13]. Dielectric Analysis The dielectric properties of the materials are important to know the charge transport phenomena and the lattice dynamics in the crystals. The dielectric behavior of LODP single crystals was studied using HIOKI 3532-50 LCR Hi-TESTER in the frequency range from 50Hz-5MHz at various temperatures ranging from 303K to 363K. The grown LODP was cut into rectangular dimension and subjected to dielectric studies. To make electrical contacts opposite faces of the crystals were coated with electronic grade silver paint and the electrical contacts were obtained. The dielectric constant (εr) was calculated using the relation ε
Cd 1 ε A
where C is the capacitance, d is the thickness of the crystal, εo is the permittivity of free space, and A is the area of the crystal. Figs. 7 and 8show the variation of the dielectric constant (εr) and dielectric loss (tan δ) at different frequencies measured at different temperatures for the grown LODP single crystal. From the figure it is seen that the value of dielectric constant (εr) is found to increase with temperature. The dielectric studies furnishes a great deal of information regarding the dielectric constant that arises from the contribution of four polarizations namely electronic, ionic, space charge and orientation developed in the material when subjected to the electrical properties [33]. High value of dielectric constant at low frequencies and higher temperature can be attributed to the lower electrostatic binding strength which arises due to space charge polarization near the grain boundary interfaces [34].In concurrence with Miller rule, lower values of dielectric constant at higher frequencies are a suitable factor for the enhancement of SHG coefficient [35]. Low dielectric loss at high frequencies suggests that the
6
sample possesses enhanced optically good quality with lesser defects. In the present investigation dielectric constant and dielectric loss values were found to be low which makes it a suitable parameter for optoelectronics applications [36].
Photoconductivity Photoconductivity studies of LODP were carried out using a Keithley 6517B electrometer. The applied electric field was increased from 10 to 100 V/cm. All the measurements were taken at room temperature. The sample was protected from all the illuminations and the corresponding dark current was recorded. For photocurrent measurements a 100W halogen lamp containing iodine vapour and tungston filament was used as a radiation source.The photocurrent was recorded for the same applied input voltage. Fig.9shows the variation of photocurrent and dark current as function of applied electric field. It is observed from the plot that both dark and photo current linearly increased with increase in applied voltage. But the dark current is always greater than that of photo current. Hence, it can be concluded that grown LOAP exhibits negative photoconductivity. It may be owing to the reduction of charge carriers in the presence of radiation [37]. Further it can be elucidated by Stockmann’s model. According to this model a two level scheme is proposed to explain negative photoconductivity. The upper energy level is situated between the Fermi level and the conduction band, whereas the other one is located close to the valence band. The second state has high capture cross sections for electrons and holes. Also this state can capture electrons from the conduction band and holes from the valance band. The lower level has high capture cross sections for electrons from the conduction band and holes from the valence band. As a result, when the sample is exposed to radiation, the recombination of electrons and holes take place, thus resulting in decrease in the number of mobile charge carriers, giving rise to negative photoconductivity.
Powder SHG Analysis The SHG conversion efficiency of LODP was measured using modified Kurtz and Perry powder SHG technique [38]. A Q-switched mode locked Nd:YAG laser with an input power of 5 mJ and pulse width of 8ns with a repetition rate of 10Hz was used. The grown LODP crystals 7
were powdered into uniform particle size of 120-150 nm and packed in a micro capillary tube and exposed to laser radiation. Powdered KDP crystals with the same particle size were used as a reference for SHG. The second harmonic signal generated in the sample was collected by the lens and detected by the monochromator, which is coupled with the photomultiplier tube. The second harmonic signal of 656 mV was obtained for LODP while KDP gave an SHG signal 45 mV for the same input beam energy. The relative SHG efficiency of LODP was found to be 14.57 times greater than that of KDP crystals.
Conclusion Single crystals of LODP were successfully grown from solution growth technique at room temperature. The grown crystal structure was confirmed from the single crystal XRD analysis and the title compound belongs to the monoclinic system with noncentrosymmetric space group P21. In UV absorption spectrum maximum absorption was observed at 355 nm. The functional groups of the LODP crystals were identified by the FTIR analysis. TG/DTA reveals the crystal is thermally stable up to 210°C. The dielectric study reveals the low dielectric constant and dielectric loss at high frequency region. The photoconductivity study exhibits the negative photoconductivity nature of the grown crystal. Powder SHG efficiency of the title compound was found to be 14.57 times greater than KDP. Thus, the optical, thermal, electrical and powder SHG studies support the suitability of the L-ornithinium dipicrate crystals for NLO applications.
Acknowledgments The authors gratefully acknowledge the financial support from the DST, Government of India, for the major research project (SB/EMEQ-293/2013). One of the authors, B. Babu thanks the UGC Networking Resource Centre, School of Chemistry, University of Hyderabad, India, for awarding Visiting Research Fellowship.
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FIGURE CAPTIONS Fig. 1. As grown crystals of L-ornithinium dipicrate. Fig. 2. ORTEP diagram of L-ornithinium dipicrate. Fig. 3. Powder XRD spectrum of L-ornithinium dipicrate. Fig. 4. FTIR spectrum of L-ornithinium dipicrate. Fig. 5. UV absorption spectrum of L-ornithinium dipicrate. Fig. 6. TG/DTA spectrum of L-ornithinium dipicrate. Fig. 7. Dielectric constant Vs Log f. Fig. 8. Dielectric loss Vs Log f. Fig. 9. Photoconductivity response of L-ornithinium dipicrate. Table 1. Crystal data and structure refinement for L-ornithinium dipicrate. Table 2. Bond lengths [Å] and angles [°] for L-ornithinium dipicrate. Table 3. Selected hydrogen bond geometries for L-ornithinium dipicrate (Å and °)
Fig. 1. As grown crystals of L-ornithinium dipicrate.
Fig. 2. ORTEP diagram of L-ornithinium dipicrate.
Fig. 3. Powder XRD spectrum of L-ornithinium dipicrate.
Fig. 4. FTIR spectrum of L-ornithinium dipicrate.
Fig. 5. UV absorption spectrum of L-ornithinium dipicrate.
100.0 40.00 235.9Cel 38.36uV
90.0
30.00 80.0
70.0 20.00 99.7%
10.00
50.0
40.0 0.00 30.0
-10.00
20.0 211.1Cel -13.80uV
10.0
-20.00
100.0
200.0
300.0
400.0 Temp Cel
500.0
600.0
700.0
Fig. 6. TG/DTA spectrum of L-ornithinium dipicrate.
0.0 800.0
TG %
DTA uV
60.0
Fig. 7. Dielectric constant Vs Log f.
Fig. 8. Dielectric loss Vs Log f.
Fig. 9. Photoconductivity response of L-ornithinium dipicrate.
Table 1. Crystal data and structure refinement for L-ornithinium dipicrate. Empirical formula
C17 H18 N8 O16
Formula weight
590.39
Temperature
293(2) K
Wavelength
0.71073 Å
Crystal system, space group
Monoclinic, P21
Unit cell dimensions
a = 7.391(4) Å b = 14.072(7) Å, β = 104.65(3) ° c = 11.709(6) Å
Volume
1178.2(1) Å3
Z, Calculated density
2, 1.664 Mgm-3
Absorption coefficient
0.150 mm-1
F(000)
608
θ range for data collection
1.80 to 28.42 °
Limiting indices
-9≤h≤9, -18≤k≤18, -15≤l≤15
Reflections collected / unique
11500 / 5188 [R (int) = 0.0320]
Completeness to θ = 28.42
99.6 %
Refinement method
Full-matrix least-squares on F2
Data / restraints / parameters
5188 / 1 / 443
Goodness-of-fit on F2
1.025
Final R indices [I>2σ (I)]
R1 = 0.0349, wR2 = 0.0885
R indices (all data)
R1 = 0.0406, wR2 = 0.0929
Largest diff. peak and hole
0.228 and -0.208 e.Å-3
CCDC No
1007643
Table 2. Bond lengths [Å] and angles [°] for L-ornithinium dipicrate. _____________________________________________________________ O(1B)-C(1B) O(1A)-C(1A) O(3A)-N(1A) O(7A)-N(3A) O(6B)-N(3B) O(7B)-N(3B) O(2B)-N(1B) N(3A)-O(6A) N(3A)-C(6A) O(8)-C(7) O(9)-C(7) N(3B)-C(6B) O(2A)-N(1A) N(8)-C(8) O(3B)-N(1B) C(2B)-C(3B) C(2B)-C(1B) C(2B)-N(1B) O(5A)-N(2A) N(9)-C(11) N(2A)-O(4A) N(2A)-C(4A) C(2A)-C(3A) C(2A)-C(1A) C(2A)-N(1A) O(5B)-N(2B) C(8)-C(9) C(8)-C(7) C(3A)-C(4A) C(6A)-C(5A) C(6A)-C(1A) C(11)-C(10) C(1B)-C(6B) C(4A)-C(5A) C(6B)-C(5B) C(9)-C(10) N(2B)-O(4B) N(2B)-C(4B) C(5B)-C(4B) C(4B)-C(3B) O(6A)-N(3A)-O(7A) O(6A)-N(3A)-C(6A) O(7A)-N(3A)-C(6A) O(6B)-N(3B)-O(7B) O(6B)-N(3B)-C(6B) O(7B)-N(3B)-C(6B) C(3B)-C(2B)-C(1B) C(3B)-C(2B)-N(1B) C(1B)-C(2B)-N(1B) O(4A)-N(2A)-O(5A)
1.256(6) 1.256(6) 1.215(4) 1.232(6) 1.217(4) 1.236(6) 1.229(5) 1.222(5) 1.451(5) 1.182(4) 1.302(6) 1.451(6) 1.222(5) 1.499(8) 1.212(4) 1.370(7) 1.449(6) 1.462(6) 1.219(5) 1.487(8) 1.207(4) 1.455(7) 1.370(7) 1.443(5) 1.459(6) 1.214(4) 1.522(7) 1.528(6) 1.387(6) 1.382(7) 1.449(6) 1.515(7) 1.443(5) 1.377(5) 1.382(7) 1.525(8) 1.221(5) 1.447(7) 1.380(6) 1.387(5) 122.11(3) 118.60(2) 119.29(4) 122.98(4) 118.47(2) 118.54(3) 125.05(3) 116.04(3) 118.91(2) 123.44(3)
O(4A)-N(2A)-C(4A) 117.47(4) O(5A)-N(2A)-C(4A) 119.09(2) C(3A)-C(2A)-C(1A) 124.98(3) C(3A)-C(2A)-N(1A) 116.95(3) C(1A)-C(2A)-N(1A) 118.04(2) O(3A)-N(1A)-O(2A) 123.60(4) O(3A)-N(1A)-C(2A) 117.93(2) O(2A)-N(1A)-C(2A) 118.40(3) N(8)-C(8)-C(9) 107.54(2) N(8)-C(8)-C(7) 106.82(2) C(9)-C(8)-C(7) 111.32(2) C(2A)-C(3A)-C(4A) 118.15(3) O(3B)-N(1B)-O(2B) 124.11(4) O(3B)-N(1B)-C(2B) 118.13(2) O(2B)-N(1B)-C(2B) 117.70(3) C(5A)-C(6A)-C(1A) 123.35(3) C(5A)-C(6A)-N(3A) 116.67(3) C(1A)-C(6A)-N(3A) 119.97(2) N(9)-C(11)-C(10) 111.71(2) O(1B)-C(1B)-C(6B) 125.17(3) O(1B)-C(1B)-C(2B) 122.61(4) C(6B)-C(1B)-C(2B) 112.14(2) C(5A)-C(4A)-C(3A) 121.40(2) C(5A)-C(4A)-N(2A) 118.81(3) C(3A)-C(4A)-N(2A) 119.79(3) C(5B)-C(6B)-C(1B) 124.40(3) C(5B)-C(6B)-N(3B) 114.76(3) C(1B)-C(6B)-N(3B) 120.83(2) C(8)-C(9)-C(10) 114.93(2) O(5B)-N(2B)-O(4B) 123.28(2) O(5B)-N(2B)-C(4B) 118.66(3) O(4B)-N(2B)-C(4B) 118.04(3) C(11)-C(10)-C(9) 108.50(2) O(1A)-C(1A)-C(2A) 122.61(4) O(1A)-C(1A)-C(6A) 125.17(3) C(2A)-C(1A)-C(6A) 112.14(2) C(4A)-C(5A)-C(6A) 119.26(3) C(4B)-C(5B)-C(6B) 119.03(3) C(5B)-C(4B)-C(3B) 121.40(2) C(5B)-C(4B)-N(2B) 118.81(3) C(3B)-C(4B)-N(2B) 119.79(3) O(8)-C(7)-O(9) 124.22(4) O(8)-C(7)-C(8) 123.21(4) O(9)-C(7)-C(8) 112.55(3) C(2B)-C(3B)-C(4B) 118.60(3) _____________________________________________________________
Table 3. Selected hydrogen bond geometries for L-ornithinium dipicrate (Å and °) D _H … A d (D_H) (Å) d (H…A) (Å) … N9-H1 O1B (i) 0.899(4) 1.890(6) N9-H1…O2B (i) 0.899(4) 2.359(8) N8-H12…O1A (ii) 0.878(4) 1.954(6) N9_H2…O1A (iii) 0.886(5) 1.924(6) N9-H2…O7A (iii) 0.879(3) 2.669(3) N8-H10…O1B (iv) 0.985(3) 2.025(7) N8-H10…O7B (iv) 0.985(3) 2.332(7) N9-H14…O6B (v) 0.929(4) 2.432(9) N8-H11…O2B (vi) 0.905(4) 2.215(8) O9-H13…O7A (vii) 0.864(4) 2.055(7) Symmetry transformations used to generate equivalent atoms: i. x, y, z ii. x+1,+y,+z-1 iii. x,+y,+z-1 iv. x+1,+y,+z v. -x+1,+y+1/2,-z vi. -x+2,+y-1/2,-z vii. -x+1,+y-1/2,-z+1
d (D…A) (Å) 2.768(9) 2.827(2) 2.782(9) 2.791(8) 3.115(2) 2.926(9) 3.069(2) 3.034(2) 3.071(2) 2.867(2)
< (DHA) (°) 164.93(4) 112.41(4) 156.65(4) 168.70(3) 112.69(4) 151.12(3) 130.94(4) 122.57(2) 157.63(3) 156.11(4)
Graphical Abstract
Highlights: New organic single crystals of L-ornithinium dipicrate was grown by slow evaporation Thermal studies shows the compound is stable up to 2100 C Powder SHG efficiency was 14.57 greater than that of standard KDP
S1386-1425(14)01442-5 http://dx.doi.org/10.1016/j.saa.2014.09.084 SAA 12760
To appear in:
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy
Received Date: Revised Date: Accepted Date:
24 July 2014 14 September 2014 19 September 2014
Please cite this article as: S. Balaprabhakaran, J. Chandrasekaran, B. Babu, R. Thirumurugan, K. Anitha, Synthesis, crystal growth and physiochemical characterization of new organic crystal: L-ornithinium dipicrate (LODP), Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy (2014), doi: http://dx.doi.org/10.1016/j.saa. 2014.09.084
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Synthesis, crystal growth and physiochemical characterization of new organic crystal: L-ornithinium dipicrate (LODP) S. Balaprabhakaran1, J. Chandrasekaran*1, B. Babu1, R. Thirumurugan2, K. Anitha2 1
Department of Physics, Sri Ramakrishna Mission Vidyalaya College of Arts and Science,
Coimbatore - 641 020, Tamil Nadu, India. 2
Department of Physics, School of Physics, Madurai Kamaraj University, Madurai-625021,
Tamil Nadu, India *Corresponding author: Ph: +91-422-2692461, Fax: +91-422-2692676 E-mail address: [email protected] _____________________________________________________________________________ Abstract L-ornithinium dipicrate (LODP) has been synthesized and good quality single crystals were grown by slow evaporation method at room temperature. Single crystal XRD confirms that the grown crystal belongs to the monoclinic system with the noncentrosymmetric space group P21. Powder X-ray diffraction study confirms the crystalline nature of the compound. FTIR spectral
analysis
confirms
the
functional
group
in
the
synthesized
compound.
Thermogravimetric and differential thermal analyses reveal the thermal stability of the crystal. The optical absorption spectrum shows the absence of absorption between 475 nm and 800 nm. The dielectric measurements were carried out to estimate the dielectric parameters of the grown crystal in the frequency range from 50Hz to 5MHz at various temperatures. The second harmonic property has been investigated by Kurtz- Perry powder technique. The relative SHG efficiency of LODP is found to be 14.57 times greater than that of the reference material KDP. Keywords: Crystal growth, nonlinear optics, X-ray diffraction, dielectric materials, thermal analysis. _ Introduction In recent years, the various classes of organic nonlinear optical materials have been investigated worldwide and also it is preferred in many applications such as optical communications, optical switching and information storage and photonics technology [1, 2]. Due to their low cost, high nonlinearity, low dielectric constant, high flexibility, high optical
1
damage threshold and ultrafast response. Organic crystals are of special interest compared to inorganic crystals. [3-8]. Amino acids are popularly referred as the building blocks of protein. Amino acid family crystals are of great interest due to their rich nonlinear optical properties. Its specific features such as Zwitterionic nature, weak Vander Waals, hydrogen bonds and wide transmittance in the visible and UV-spectral region make them an ideal candidate for NLO applications [9, 10]. Amino acids contain protonated amino group (NH+) and deprotonated carboxylic acid group (COO-);owing to its asymmetric carbon atom most of the amino acids crystallize in a noncentrosymmetric space group [11]. The picrates are convenient for identification and quantitative analysis of organic compounds. Also it is used in human therapy such as treatment of burns, antiseptic and astringent agent. The bonding of these picrate complexes depends on the nature of the donor-acceptor system [12, 13]. Due to its Zwitterionic nature, an amino acid nonlinear optical property is increased when mixed with organic acids. Picrates are attractive candidates for the formation of salts with various organic bases. Due to this formation of the conjugated base, picrate, the value of molecular hyperpolarizability improved because of the proton transfer. Previously some of the picrate of amino acids such as diglycine picrate, L-alanine L-alaninium picrate, L-isoleucinium picrate, L-leucine L-leucinium picrate, DL-phenylalanine DL-phenylalaninium picrate and DL-methionine DL-methioninium picrate, L-asparaginium picrate, L-histidinium dipicrate dihydrate, L-tryptophanium picrate and L-Valinium Picrate were reported [14-28]. On the basis of these facts, in the present communication for the first time we describe the synthesis and characterization of Lornithinium dipicrate crystal. The grown crystals were characterized by various characterization techniques
such
as
single
crystals
XRD,
powder
XRD,
FTIR,
UV,
Dielectric,
photoconductivity, TG/DTA and powder SHG studies and the results were discussed.
Experimental Crystal growth LODP was synthesized by taking L-ornithine and picric acid in an equimolar ratio of 1:1. L-ornithine and picric acid were dissolved separately in water and acetone, stirred well for about 20minutes using a magnetic stirrer. Then, these solutions were mixed together and stirred for about one hour. The saturated solution was filtered twice using whatmann filter paper and transferred to crystallizing vessel. Top of the vessel was covered with thin plastic sheet and to 2
facilitate the slow evaporation, a few holes were made on it. For the slow evaporation of the solvent, the beaker was kept undisturbed at room temperature. Well defined yellow coloured crystals with good transparency appeared in the growth period of 15 days. The photograph of the grown crystal is shown in Fig. 1.
Results and Discussion X- Ray Diffraction Analysis The single crystal X-ray diffraction data of the title compound were collected at 293 K with graphite–monochromated Mo Kα radiation (λ = 0.071073 nm), and used Enraf–Nonius CAD-4 diffractometer with the ω-2θ scan mode. A suitable sample of size 0.26 mm x 0.21 mm x 0.18 mm was chosen and mounted on the goniometer. Lattice parameters were collected from least-squares fit of 25 reflections. A total of 11500 (5188 independent Rint = 0.0320) reflections were measured. Cell refinement and data reduction were carried out using CAD-4 EXPRESS [29] and XCAD4 [30]. The structures were solved by direct methods procedure using SHELXS97 [31] and refined by full-matrix least-squares on F2 using SHELXL -97 program [31]. All non-hydrogen atoms were anisotropically refined. The hydrogen atom positions were fixed at geometrically calculated distances to allow riding on the parent atoms to which they are attached. ORTEP diagram of LODP crystal is depicted in Fig. 2.The crystal data and details pertaining to data collection and the structure refinement are given in Table 1. The relevant bond lengths, bond angles and torsion angles are listed in Table 2. The selected hydrogen bond geometries are given in Table 3.The molecular graphics were prepared by using the ORTEP [32].The X-ray diffraction study reveals that the grown LODP crystal belongs to the monoclinic system with the noncentrosymmetric space group P21. The lattice parameter values are found to be a= 9.67 (1) Å, b = 5.26 (2) Å, c= 12.07(3) Å. Crystallographic data for the title compound is given in Table 1. The L-ornithinium dipicrate crystal structure comprises of crystallographically independent two picrate anions and one ornithinedication. Protonation occurs at the two possible amine sites in the ornithine molecule at atom N8 and N9 respectively which leads to the formation of cation and the two picrate anions have been formed by loss of one H atom at the hydroxyl group in the picric acid at atom O1A and O1B respectively, it is confirmed by the variations of the hydroxyl C__O bond distances (d (C1A__O1A) =1.256(6) Å, d (C1B__O1B) =1.256(6) Å). The ornithine residue consists of two planar groups, viz. the carboxyl group and 3
the aliphatic side chain. The plane of the aliphatic chain forms a dihedral angle of 72.17(3) ° with the carboxyl plane. The backbone conformation angle (O8__C7__C8__N8) indicates a gauge conformation [30.73 °]. The other angles,
(N8__C8__C9__C10), (C8__C9__C10__C11) and
(C9__C10__C11__N9) have fully extended trans-trans conformations [177.32 (2) °, -179.35(5) ° and 176.23(3) °] respectively. During the crystallization process, the removal of phenolic H atom from the picric acid leads to a shortening of the C1A-O1A = 1.256(6) Å and C2B-O2B = 1.256(6) Å bond lengths. These bond length values are intermediate between the typical singlebond and double-bond values, implying that the negative charge located on the phenolate O atom is delocalized. Both aromatic rings in picrate anions are good approximation with planar, maximum deviation from the least-square plane calculated by the six ring atoms is 0.008(1) Å in the anion A and 0.018(2) Å in anion B. The three nitro groups of the picrate anion A deviate from the benzene plane by 36.00(3) ° (N1A), 2.88(3) ° (N2A) and 12.42(3) ° (N3A) and in anion B the twist angles are 44.22(3) ° (N1B), 7.44(3) ° (N2B) and 27.35(3) ° (N3B) respectively. The hydrogen atoms H1 of N9 and H12 of N8 in the amine groups of the ornithinium cation forms a strong N__H…O hydrogen bonds with hydroxyl group O1A and O1B atoms of the picrate A and B anions respectively. The hydrogen atom H13 of O9 in the carboxyl group of the ornithinium cation forms a strong O__H…O intermolecular hydrogen bonds with the nitro group of O7A and O7B atoms of the picrate A and B anions respectively. Cation is linked to anion through N9__H1…O1B and O9__H13…O7B intermolecular hydrogen bonds, which leads to the formation of ring R 14. The crystal structure is stabilized by the strong N__H…O, O__H…O and weak intermolecular hydrogen bonds and also the O__H…O intramolecular hydrogen bonds. Powder X-ray diffraction study was carried out by employing JEOL-JDX 8030 X-ray diffractometer with Nickel filtered CuKα (λ=1.5405 Å) radition. The grown LODP crystal was finely powdered and it has been subjected to powder XRD analysis. Narrow peaks indicate the good crystallinity of the material. All reflections are observed and indexed at room temperature. The powder XRD pattern of the grown LODP crystal is shown in Fig. 3. The well defined Bragg’s peaks at specific 2θ angles confirmed the perfect crystalline nature of LODP single crystal.
4
FTIR Analysis FTIR spectrum of LODP crystal was recorded using PerkinElmer spectrometer in the range of 4000-400cm-1by employing KBr pellet method. The result of the room temperature FTIR spectrum of LODP crystal is shown in Fig. 4. NH3+ symmetric and asymmetric stretching vibrations were observed at 3248 and 2967 cm-1. The broad band in IR spectrum at 2967 cm-1 corresponds to OH stretching vibration. The absorptions at 1562 and 1323 cm-1 confirms the asymmetrical and symmetrical stretching vibrations of NO2 group. The carbonyl absorption at 1762cm-1 confirms the COOH and COO- groups of the compound. The strong absorption peaks at 1627cm-1 indicates the presence of primary amino group. The presence of the peak at 1414cm-1 corresponds to the symmetric stretching vibration of carboxyl group. The absorption bands at 1316 cm-1 is due to NO3 asymmetric stretching deformation. The C-N stretching vibration is identified by the absorption peak at 1084 cm-1. C-C stretching vibration is observed at 922cm-1. Absorption peaks at 1619, 1543 and 1422 cm-1 reveals the presence of aromatic C=C stretching vibration. Peak at 1162 cm-1 is assigned to the C-O stretching vibrations of picric acid. The absorption band at 478cm-1 is due to COO- rocking vibration. C-H out of plane bending vibration was observed at 787 cm-1. The presence of the above bands confirms the formation of picrate salt of L-ornithine.
UV- Visible Spectral Analysis The optical absorption spectrum of the grown LODP crystal was recorded using Perkin Elmer Lambda 35 UV –Vis spectrophotometer in the wavelength range from200 nm to 800nm. The recorded spectrum is shown in Fig. 5. The spectrum exhibits the strong absorption peak at 355 nm. The absorption peak at 355 nm is assigned to π to π* transition of the compound, which is attributed to the charge transfer of the compound [13]. Absence of absorption between 475 nm and 800 nm is an advantage, as it is the key requirement for materials possessing SHG properties. As a result, it can be used as a potential candidate for the SHG device applications in the visible region [23].
Thermal Analysis To study the thermal stability of the grown crystal TG/DTA analysis were carried out using STA 1500 thermal analyzer from room temperature to 800°C in nitrogen atmosphere at a 5
heating rate of 20°C/min. Recorded TG/DTA spectrum is shown in Fig. 6. From the figure it is clear that there is no weight loss between room temperature to 210°C and hence the crystal rejects the solvent molecules during the crystallization. TG spectrum shows that the title compound is stable up to 210°C. The major weight loss started from 205°C and ending at 244°C. In DTA there is a sharp endothermic at 211°C is assigned to melting point of the compound which are fit well with the TG spectrum. In DTA a sharp exothermic peak at 235°C is due to the major decomposition of the compound. With the temperature increasing above 300°C, volatile substances such as NO, NO2, CH4, NH3 and CO2molecules will be liberated [13]. Dielectric Analysis The dielectric properties of the materials are important to know the charge transport phenomena and the lattice dynamics in the crystals. The dielectric behavior of LODP single crystals was studied using HIOKI 3532-50 LCR Hi-TESTER in the frequency range from 50Hz-5MHz at various temperatures ranging from 303K to 363K. The grown LODP was cut into rectangular dimension and subjected to dielectric studies. To make electrical contacts opposite faces of the crystals were coated with electronic grade silver paint and the electrical contacts were obtained. The dielectric constant (εr) was calculated using the relation ε
Cd 1 ε A
where C is the capacitance, d is the thickness of the crystal, εo is the permittivity of free space, and A is the area of the crystal. Figs. 7 and 8show the variation of the dielectric constant (εr) and dielectric loss (tan δ) at different frequencies measured at different temperatures for the grown LODP single crystal. From the figure it is seen that the value of dielectric constant (εr) is found to increase with temperature. The dielectric studies furnishes a great deal of information regarding the dielectric constant that arises from the contribution of four polarizations namely electronic, ionic, space charge and orientation developed in the material when subjected to the electrical properties [33]. High value of dielectric constant at low frequencies and higher temperature can be attributed to the lower electrostatic binding strength which arises due to space charge polarization near the grain boundary interfaces [34].In concurrence with Miller rule, lower values of dielectric constant at higher frequencies are a suitable factor for the enhancement of SHG coefficient [35]. Low dielectric loss at high frequencies suggests that the
6
sample possesses enhanced optically good quality with lesser defects. In the present investigation dielectric constant and dielectric loss values were found to be low which makes it a suitable parameter for optoelectronics applications [36].
Photoconductivity Photoconductivity studies of LODP were carried out using a Keithley 6517B electrometer. The applied electric field was increased from 10 to 100 V/cm. All the measurements were taken at room temperature. The sample was protected from all the illuminations and the corresponding dark current was recorded. For photocurrent measurements a 100W halogen lamp containing iodine vapour and tungston filament was used as a radiation source.The photocurrent was recorded for the same applied input voltage. Fig.9shows the variation of photocurrent and dark current as function of applied electric field. It is observed from the plot that both dark and photo current linearly increased with increase in applied voltage. But the dark current is always greater than that of photo current. Hence, it can be concluded that grown LOAP exhibits negative photoconductivity. It may be owing to the reduction of charge carriers in the presence of radiation [37]. Further it can be elucidated by Stockmann’s model. According to this model a two level scheme is proposed to explain negative photoconductivity. The upper energy level is situated between the Fermi level and the conduction band, whereas the other one is located close to the valence band. The second state has high capture cross sections for electrons and holes. Also this state can capture electrons from the conduction band and holes from the valance band. The lower level has high capture cross sections for electrons from the conduction band and holes from the valence band. As a result, when the sample is exposed to radiation, the recombination of electrons and holes take place, thus resulting in decrease in the number of mobile charge carriers, giving rise to negative photoconductivity.
Powder SHG Analysis The SHG conversion efficiency of LODP was measured using modified Kurtz and Perry powder SHG technique [38]. A Q-switched mode locked Nd:YAG laser with an input power of 5 mJ and pulse width of 8ns with a repetition rate of 10Hz was used. The grown LODP crystals 7
were powdered into uniform particle size of 120-150 nm and packed in a micro capillary tube and exposed to laser radiation. Powdered KDP crystals with the same particle size were used as a reference for SHG. The second harmonic signal generated in the sample was collected by the lens and detected by the monochromator, which is coupled with the photomultiplier tube. The second harmonic signal of 656 mV was obtained for LODP while KDP gave an SHG signal 45 mV for the same input beam energy. The relative SHG efficiency of LODP was found to be 14.57 times greater than that of KDP crystals.
Conclusion Single crystals of LODP were successfully grown from solution growth technique at room temperature. The grown crystal structure was confirmed from the single crystal XRD analysis and the title compound belongs to the monoclinic system with noncentrosymmetric space group P21. In UV absorption spectrum maximum absorption was observed at 355 nm. The functional groups of the LODP crystals were identified by the FTIR analysis. TG/DTA reveals the crystal is thermally stable up to 210°C. The dielectric study reveals the low dielectric constant and dielectric loss at high frequency region. The photoconductivity study exhibits the negative photoconductivity nature of the grown crystal. Powder SHG efficiency of the title compound was found to be 14.57 times greater than KDP. Thus, the optical, thermal, electrical and powder SHG studies support the suitability of the L-ornithinium dipicrate crystals for NLO applications.
Acknowledgments The authors gratefully acknowledge the financial support from the DST, Government of India, for the major research project (SB/EMEQ-293/2013). One of the authors, B. Babu thanks the UGC Networking Resource Centre, School of Chemistry, University of Hyderabad, India, for awarding Visiting Research Fellowship.
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10
FIGURE CAPTIONS Fig. 1. As grown crystals of L-ornithinium dipicrate. Fig. 2. ORTEP diagram of L-ornithinium dipicrate. Fig. 3. Powder XRD spectrum of L-ornithinium dipicrate. Fig. 4. FTIR spectrum of L-ornithinium dipicrate. Fig. 5. UV absorption spectrum of L-ornithinium dipicrate. Fig. 6. TG/DTA spectrum of L-ornithinium dipicrate. Fig. 7. Dielectric constant Vs Log f. Fig. 8. Dielectric loss Vs Log f. Fig. 9. Photoconductivity response of L-ornithinium dipicrate. Table 1. Crystal data and structure refinement for L-ornithinium dipicrate. Table 2. Bond lengths [Å] and angles [°] for L-ornithinium dipicrate. Table 3. Selected hydrogen bond geometries for L-ornithinium dipicrate (Å and °)
Fig. 1. As grown crystals of L-ornithinium dipicrate.
Fig. 2. ORTEP diagram of L-ornithinium dipicrate.
Fig. 3. Powder XRD spectrum of L-ornithinium dipicrate.
Fig. 4. FTIR spectrum of L-ornithinium dipicrate.
Fig. 5. UV absorption spectrum of L-ornithinium dipicrate.
100.0 40.00 235.9Cel 38.36uV
90.0
30.00 80.0
70.0 20.00 99.7%
10.00
50.0
40.0 0.00 30.0
-10.00
20.0 211.1Cel -13.80uV
10.0
-20.00
100.0
200.0
300.0
400.0 Temp Cel
500.0
600.0
700.0
Fig. 6. TG/DTA spectrum of L-ornithinium dipicrate.
0.0 800.0
TG %
DTA uV
60.0
Fig. 7. Dielectric constant Vs Log f.
Fig. 8. Dielectric loss Vs Log f.
Fig. 9. Photoconductivity response of L-ornithinium dipicrate.
Table 1. Crystal data and structure refinement for L-ornithinium dipicrate. Empirical formula
C17 H18 N8 O16
Formula weight
590.39
Temperature
293(2) K
Wavelength
0.71073 Å
Crystal system, space group
Monoclinic, P21
Unit cell dimensions
a = 7.391(4) Å b = 14.072(7) Å, β = 104.65(3) ° c = 11.709(6) Å
Volume
1178.2(1) Å3
Z, Calculated density
2, 1.664 Mgm-3
Absorption coefficient
0.150 mm-1
F(000)
608
θ range for data collection
1.80 to 28.42 °
Limiting indices
-9≤h≤9, -18≤k≤18, -15≤l≤15
Reflections collected / unique
11500 / 5188 [R (int) = 0.0320]
Completeness to θ = 28.42
99.6 %
Refinement method
Full-matrix least-squares on F2
Data / restraints / parameters
5188 / 1 / 443
Goodness-of-fit on F2
1.025
Final R indices [I>2σ (I)]
R1 = 0.0349, wR2 = 0.0885
R indices (all data)
R1 = 0.0406, wR2 = 0.0929
Largest diff. peak and hole
0.228 and -0.208 e.Å-3
CCDC No
1007643
Table 2. Bond lengths [Å] and angles [°] for L-ornithinium dipicrate. _____________________________________________________________ O(1B)-C(1B) O(1A)-C(1A) O(3A)-N(1A) O(7A)-N(3A) O(6B)-N(3B) O(7B)-N(3B) O(2B)-N(1B) N(3A)-O(6A) N(3A)-C(6A) O(8)-C(7) O(9)-C(7) N(3B)-C(6B) O(2A)-N(1A) N(8)-C(8) O(3B)-N(1B) C(2B)-C(3B) C(2B)-C(1B) C(2B)-N(1B) O(5A)-N(2A) N(9)-C(11) N(2A)-O(4A) N(2A)-C(4A) C(2A)-C(3A) C(2A)-C(1A) C(2A)-N(1A) O(5B)-N(2B) C(8)-C(9) C(8)-C(7) C(3A)-C(4A) C(6A)-C(5A) C(6A)-C(1A) C(11)-C(10) C(1B)-C(6B) C(4A)-C(5A) C(6B)-C(5B) C(9)-C(10) N(2B)-O(4B) N(2B)-C(4B) C(5B)-C(4B) C(4B)-C(3B) O(6A)-N(3A)-O(7A) O(6A)-N(3A)-C(6A) O(7A)-N(3A)-C(6A) O(6B)-N(3B)-O(7B) O(6B)-N(3B)-C(6B) O(7B)-N(3B)-C(6B) C(3B)-C(2B)-C(1B) C(3B)-C(2B)-N(1B) C(1B)-C(2B)-N(1B) O(4A)-N(2A)-O(5A)
1.256(6) 1.256(6) 1.215(4) 1.232(6) 1.217(4) 1.236(6) 1.229(5) 1.222(5) 1.451(5) 1.182(4) 1.302(6) 1.451(6) 1.222(5) 1.499(8) 1.212(4) 1.370(7) 1.449(6) 1.462(6) 1.219(5) 1.487(8) 1.207(4) 1.455(7) 1.370(7) 1.443(5) 1.459(6) 1.214(4) 1.522(7) 1.528(6) 1.387(6) 1.382(7) 1.449(6) 1.515(7) 1.443(5) 1.377(5) 1.382(7) 1.525(8) 1.221(5) 1.447(7) 1.380(6) 1.387(5) 122.11(3) 118.60(2) 119.29(4) 122.98(4) 118.47(2) 118.54(3) 125.05(3) 116.04(3) 118.91(2) 123.44(3)
O(4A)-N(2A)-C(4A) 117.47(4) O(5A)-N(2A)-C(4A) 119.09(2) C(3A)-C(2A)-C(1A) 124.98(3) C(3A)-C(2A)-N(1A) 116.95(3) C(1A)-C(2A)-N(1A) 118.04(2) O(3A)-N(1A)-O(2A) 123.60(4) O(3A)-N(1A)-C(2A) 117.93(2) O(2A)-N(1A)-C(2A) 118.40(3) N(8)-C(8)-C(9) 107.54(2) N(8)-C(8)-C(7) 106.82(2) C(9)-C(8)-C(7) 111.32(2) C(2A)-C(3A)-C(4A) 118.15(3) O(3B)-N(1B)-O(2B) 124.11(4) O(3B)-N(1B)-C(2B) 118.13(2) O(2B)-N(1B)-C(2B) 117.70(3) C(5A)-C(6A)-C(1A) 123.35(3) C(5A)-C(6A)-N(3A) 116.67(3) C(1A)-C(6A)-N(3A) 119.97(2) N(9)-C(11)-C(10) 111.71(2) O(1B)-C(1B)-C(6B) 125.17(3) O(1B)-C(1B)-C(2B) 122.61(4) C(6B)-C(1B)-C(2B) 112.14(2) C(5A)-C(4A)-C(3A) 121.40(2) C(5A)-C(4A)-N(2A) 118.81(3) C(3A)-C(4A)-N(2A) 119.79(3) C(5B)-C(6B)-C(1B) 124.40(3) C(5B)-C(6B)-N(3B) 114.76(3) C(1B)-C(6B)-N(3B) 120.83(2) C(8)-C(9)-C(10) 114.93(2) O(5B)-N(2B)-O(4B) 123.28(2) O(5B)-N(2B)-C(4B) 118.66(3) O(4B)-N(2B)-C(4B) 118.04(3) C(11)-C(10)-C(9) 108.50(2) O(1A)-C(1A)-C(2A) 122.61(4) O(1A)-C(1A)-C(6A) 125.17(3) C(2A)-C(1A)-C(6A) 112.14(2) C(4A)-C(5A)-C(6A) 119.26(3) C(4B)-C(5B)-C(6B) 119.03(3) C(5B)-C(4B)-C(3B) 121.40(2) C(5B)-C(4B)-N(2B) 118.81(3) C(3B)-C(4B)-N(2B) 119.79(3) O(8)-C(7)-O(9) 124.22(4) O(8)-C(7)-C(8) 123.21(4) O(9)-C(7)-C(8) 112.55(3) C(2B)-C(3B)-C(4B) 118.60(3) _____________________________________________________________
Table 3. Selected hydrogen bond geometries for L-ornithinium dipicrate (Å and °) D _H … A d (D_H) (Å) d (H…A) (Å) … N9-H1 O1B (i) 0.899(4) 1.890(6) N9-H1…O2B (i) 0.899(4) 2.359(8) N8-H12…O1A (ii) 0.878(4) 1.954(6) N9_H2…O1A (iii) 0.886(5) 1.924(6) N9-H2…O7A (iii) 0.879(3) 2.669(3) N8-H10…O1B (iv) 0.985(3) 2.025(7) N8-H10…O7B (iv) 0.985(3) 2.332(7) N9-H14…O6B (v) 0.929(4) 2.432(9) N8-H11…O2B (vi) 0.905(4) 2.215(8) O9-H13…O7A (vii) 0.864(4) 2.055(7) Symmetry transformations used to generate equivalent atoms: i. x, y, z ii. x+1,+y,+z-1 iii. x,+y,+z-1 iv. x+1,+y,+z v. -x+1,+y+1/2,-z vi. -x+2,+y-1/2,-z vii. -x+1,+y-1/2,-z+1
d (D…A) (Å) 2.768(9) 2.827(2) 2.782(9) 2.791(8) 3.115(2) 2.926(9) 3.069(2) 3.034(2) 3.071(2) 2.867(2)
< (DHA) (°) 164.93(4) 112.41(4) 156.65(4) 168.70(3) 112.69(4) 151.12(3) 130.94(4) 122.57(2) 157.63(3) 156.11(4)
Graphical Abstract
Highlights: New organic single crystals of L-ornithinium dipicrate was grown by slow evaporation Thermal studies shows the compound is stable up to 2100 C Powder SHG efficiency was 14.57 greater than that of standard KDP
