Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 124 (2014) 603–610
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Synthesis, growth, crystal structure, spectral, thermal, mechanical and optical studies of stilbazolium derivative single crystal: 2-[2-(4-Diethylamino-phenyl)-vinyl]-1-methyl-pyridinium naphthalene-2-sulfonate (DESNS) K. Senthil, S. Kalainathan ⇑, A. Ruban Kumar Centre for Crystal Growth, School of Advanced Sciences, VIT University, Vellore 632 014, Tamil Nadu, India
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
DESNS single crystals with size of
15 10 9 mm3 were firstly grown by slow evaporation method. The crystal structure of DESNS for the first time in the literature. UV–Vis–NIR spectral analysis shows that grown crystal has good transparency window from 476 to 1100 nm. TG/DTA studies show that the compound is stable up to its melting point at 226 °C. Mechanical studies establish that the crystal is belongs to the soft material category.
a r t i c l e
i n f o
Article history: Received 5 November 2013 Received in revised form 24 December 2013 Accepted 8 January 2014 Available online 23 January 2014 Keywords: Organic compounds Crystal structure Single crystal growth Slow evaporation X-ray diffraction Micro-hardness
a b s t r a c t Single crystals of organic optical material, 2-[2-(4-Diethylamino-phenyl)-vinyl]-1-methyl-pyridinium naphthalene-2-sulfonate (DESNS) (15 10 9 mm3) were grown by a slow evaporation technique at room temperature using methanol–acetonitrile (1:1) mixed solvent. The molecular structure of the grown crystal was confirmed by single crystal X-ray diffraction studies, and it belongs to orthorhombic system with space group Pbca and the unit cell dimentions are a = 11.5148(3) Å, b = 15.4352(4) Å, c = 27.2187(7) Å, Z = 8. The crystallinity of the title crystals was confirmed from the powder XRD pattern. The presence of functional groups of the title crystal was confirmed from the FTIR spectral studies. The transparent range and cut off wavelength of the grown crystal was studied by the UV–Vis–NIR spectroscopic analysis. The mechanical properties and thermal behavior of the grown crystals were studied from Vickers microhardness test and TG/DTA. Ó 2014 Elsevier B.V. All rights reserved.
1. Introduction During the last three decades, the stilbazolium salts and many of the derivatives have been investigated for their large second ⇑ Corresponding author. Tel.: +91 416 2202350; fax: +91 416 2243092. E-mail address: [email protected] (S. Kalainathan). http://dx.doi.org/10.1016/j.saa.2014.01.064 1386-1425/Ó 2014 Elsevier B.V. All rights reserved.
order nonlinear optical responses [1]. In recent progress, a lot of attention has been given to polar organic crystals because of their various potential applications including nonlinear optical applications, laser frequency conversion, optical power limiting devices, optical storage technology, electro-optics, THz-wave generation and electric-field detection [2–4]. Organic p-conjugated systems are interesting because they exhibit large molecular quadratic
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hyperpolarizabilities, scope for altering the properties by changing electron donor and electron acceptor moieties at their two ends [5]. The formation of the carbon-carbon bridge (C@C) with p-conjugation chromospheres of an organic molecule of such materials, many reactions have been reported, such as Knoevenagel condensation, Suzuki coupling reaction, Wittig-Homer Emmons condensations among them particularly Knoevenagel condensation reaction most favorable and easy method for to form a carbon–carbon double bond [6–9]. However, the presence of styryl pyridinium compounds is being mainly used as antibacterial drugs, herbicides, environmental disinfection, disinfection in hospital environments and food industry due to their low toxicity to humans and animals [10–12]. The design of NLO chromophore crystals has an electron withdrawing group that bear an electron donating group interacting through the p-conjugated system with parallel alignment in the crystal structure [13]. In the recent years many efforts have been made to wide investigation by different research groups in the development of DSNS (4-N,N-dimethylamino-40 -N0 -methyl-stilbazolium naphthalene-2-sulfonate) and its derivatives crystals for their high and fast nonlinearity properties with 50% higher powder second harmonic generation (SHG) efficiency than that of the DAST crystal (4-N,N-dimethylamino-40 -N0 -methyl-stilbazolium tosylate) at a 1907 nm [14,15]. In this series, this is a derivative in the stilbazolium family and one of the new organic materials. This is the first article on the crystallization of DESNS. So far, we have extended our report in synthesis, growth, crystal structure, spectral, thermal, and mechanical study were also carried for DESNS single crystals.
2. Experimental procedure 2.1. Material synthesis and crystal growth DESNS compound was synthesized by the Knoevenagel condensation of 1, 2-dimethylpyridinium iodide, which was prepared from 2-picoline, iodomethane and p-diethylaminobenzaldehyde in the presence of piperidine as a catalyst. The overall synthesis process and molecular structures are shown in scheme 1. 1, 2-Dimethylpyridinium iodide 1 1, 2-Dimethylpyridinium Iodide 1 was prepared by equimolar ratio of 2-Picoline (2 ml, 20 mmol) and iodomethane (1.3 ml, 20 mmol) in acetone (30 ml). The mixtures were refluxed for 4 h and cooled to ambient temperature. The resulting white precipitates were collected by filtration, dried and melting point was found to be 155 °C. 2-[(E)-4-(diethyl amino) styryl]-1-methyl-pyridinium iodide 2 The title material (2) was synthesized according to the previously reported method [16]. To a solution of 1 (2.35 g 10 mmol) in hot methanol (30 ml), 4-diethylamino benzaldehyde (1.8 g 10 mmol), and piperidine (0.98 ml, 10 mmol) were added. Then the mixture solution was refluxed for 6 h under a dry nitrogen atmosphere. Once the reaction was complete, the purple precipitate was filtered off and washed with ether for removal of unreacted starting materials. The title compound 2 was purified by successive recrystallized from methanol (m.p. 256 °C).
Scheme 1. Synthesis of DESNS.
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2-[2-(4-Diethylamino-phenyl)-vinyl]-1-methyl-pyridinium naphthalene-2-sulfonate (DESNS) 3 Compound 2 (3.9g10 mmol) was dissolved in equal volume of methanol-acetonitrile (40 ml) mixed solvent by heating and simultaneously, naphthalene-2-sulfonate (2.3 g 10 mmol) was dissolved in 20 ml of equal ratio of methanol-Millipore water by heating. The two hot solutions were mixed and further heated for 2 h at 80 °C and then mixer was cooled to ambient temperature. The resulting red color precipitate was filtered off and dried at 120 °C for 3 h to get free of water. The purity of DESNS was achieved by repeated recrystallization first from water, and then from methanol for removal of unreacted materials (m.p. 226 °C). Single crystal of title compounds was grown using slow evaporation technique. Initially, several organic solvents in pure and mixed forms solvents were investigated to know the growth habit of a title crystal, solvent such as methanol, ethanol, acetonitrile, chloroform, methanol– water, methanol–chloroform, and methanol–acetonitrile were dried. Finally, only in the combination of methanol–acetonitrile mixed solvent system was found to be suitable for the crystal formation was observed. A saturated solution of DESNS material was prepared at room temperature in methanol–acetonitrile (1:1) mixed solvent, and then solution was stirred continuously to obtain homogeneous medium by using a magnetic stirrer, and filtered the saturated solution into the beaker using Whatman filter paper with porosity 0.1 lm. After that beaker was tightly covered with aluminum foil, and then with few holes to control evaporation rate of the mixed solvent. Small transparent seed crystals were obtained over in a period of 3 days through spontaneous nucleation. After around 40 days, bulk size of DESNS single crystal with dimension up to 15 10 9 mm3 (Fig. 1) was harvested by defect free seed crystal applied to the saturated solution. 2.2. Characterization studies The grown crystal structure was investigated by single crystal X-ray diffraction analysis using a Bruker Kappa APEX II diffractometer (Mo Ka = 0.71073 Å). The structure was solved and full matrix least squares refinement by direct methods using SHELXS97 programs [17]. The plots of molecular graphics were created with the PLATON software [18]. The powder X-ray diffraction analysis were carried out by using BRUKER X-Ray diffractometer with the Cu Ka radiation (k = 1.5406 Å) in the range of 10–50°, in steps of 0.02°. The FT-IR spectrum was recorded using SHIMADZU IRAFFINITY instrument in the wavelength range of 400–4000 cm1 using the KBr pellet technique. Proton NMR spectrum was recorded
using BRUKER instrument operating with 400 MHz, and DMSO d6 was used as solvent at room temperature. The optical studies of DESNS crystal were carried out by using ELICO SL 218 double beam UV–Vis–NIR spectrometer in the wavelength region of 190–1100 nm. Thermal stability studies were carried out with TG/DTA instrument SBT Q600 apparatus in a nitrogen atmosphere. The mechanical behavior of DESNS single crystal was tested by employing MH-112 Micro-hardness instrument with Vickers indenter at room temperature.
3. Result and discussion 3.1. Single crystal X-ray diffraction analysis The new structure of DESNS crystal was determined from single crystal XRD analysis. From the single crystal XRD studies, it shows that DESNS belongs to the centrosymmetry crystal structure with orthorhombic crystal system and space group Pbca. Single crystal data and further details of the crystallography data collection and structural refinement results are summarized in Table 1. Selected lengths bond angles which are given in Tables 2 and 3. The asymmetric unit of the title compound (Fig. 2(a)) consists of a 2-[4-(diethyl amino) styryl]-1-methylpyridinium (C18 H23 N2+) cation, and a naphthalene sulfonate (C10 H7 O3 S) anion molecule. The packing of the molecule shows partly viewed along the a-axis as shown in (Fig. 2(b)). The 2-[4-(diethylamino) styryl]-1-methylpyridinium cation exists in an E configuration with respect to the C6@C7 double bond [1.334(2) Å]. The cation is slightly twisted, with the dihedral angle between the C1AC5/N1 pyridinium and C8AC13 benzene rings being 10.59 (6)°, and it possess trans configuration, which can be confirmed from the torsional angle C5AC6AC7AC8, 179.61(16)°. The cation and anion are inclined to each other which indicated by the dihedral angles between the C17AC22 sulfonated substituted benzene ring of anion and pyridinium and C8AC13 benzene rings of cation being 54.90 (10) and 59.90 (10)°, respectively. The two ethyl groups of diethylamino moiety are slightly twisted from the mean plane of the attached C8AC13 ring as indicated by the torsion angles C16AN2AC11A C12 = 5.21(3)° and C14AN2AC11AC10 = 9.1(3)°. In the crystal
Table 1 Crystal data structure refinement for 2-[2-(4-Diethylamino-phenyl)-vinyl]-1-methylpyridinium naphthalene-2-sulfonate (DESNS). Empirical formula Formula weight Temperature Wavelength Crystal system, space group Unit cell dimentions
Fig. 1. Photograph of DESNS crystal grown by slow evaporation.
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Volume Z, Calculated density Absorption coefficient F (0 0 0) Crystal size Theta range for data collection Limiting indices Reflections collected/unique Completeness to theta = 25.00 Absorption correction Max. and min. transmission Refinement method Data/restraints/parameters Goodness-of-fit on F2 Final R indices [I > 2sigma (I)] R indices (all data) Largest diff. peak and hole
C28H30N2O3S 474.60 298(2) K 0.71073 Å Orthorhombic, Pbca a = 11.5148(3) Å a = 90° b = 15.4352(4) Å b = 90° c = 27.2187(7) Å c = 90° 4837.7(2) Å3 8, 1.303 Mg/m3 0.167 mm1 2016 0.20 0.18 0.15 mm 2.3229.36° 15 6 h 6 12, 21 6 k 6 18, 37 6 l 6 37 34372/6492 [R (int) = 0.0331] 99.8% None 0.9754 and 0.9674 Full-matrix least-squares on F2 6492/0/310 1.002 R1 = 0.0472, wR2 = 0.1039 R1 = 0.0969, wR2 = 0.1236 0.256 and 0.266 e Å3
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Table 2 Bond lengths [Å] for DESNS. Atoms
Length
Atoms
Length
Atoms
Length
Atoms
Length
Atoms
Length
C(1)AC(2) C(1)AN(1) C(1)AH(1) C(2)AC(3) C(2)AH(2) C(3)AC(4) C(3)AH(3) C(4)AC(5) C(4)AH(4) C(5)AN(1) C(5)AC(6) C(6)AC(7) C(6)AH(6) C(7)AC(8) C(7)AH(7) C(8)AC(9) C(8)AC(13)
1.347(3) 1.353(2) 0.9300 1.380(3) 0.9300 1.363(3) 0.9300 1.393(2) 0.9300 1.363(2) 1.442(2) 1.334(2) 0.9300 1.445(2) 0.9300 1.395(2) 1.401(2)
C(1)AC(2) C(1)AN(1) C(1)AH(1) C(2)AC(3) C(2)AH(2) C(3)AC(4) C(3)AH(3) C(4)AC(5) C(4)AH(4) C(5)AN(1) C(5)AC(6) C(6)AC(7) C(6)AH(6) C(7)AC(8) C(7)AH(7) C(8)AC(9) C(8)AC(13)
1.347(3) 1.353(2) 0.9300 1.380(3) 0.9300 1.363(3) 0.9300 1.393(2) 0.9300 1.363(2) 1.442(2) 1.334(2) 0.9300 1.445(2) 0.9300 1.395(2) 1.401(2)
C(9)AC(10) C(9)AH(9) C(10)AC(11) C(10)AH(10) C(11)AN(2) C(11)AC(12) C(12)AC(13) C(12)AH(12) C(13)AH(13) C(14)AN(2) C(14)AC(15) C(14)AH(14A) C(14)AH(14B) C(15)AH(15A) C(15)AH(15B) C(15)AH(15C) C(16)AN(2)
1.366(2) 0.9300 1.406(2) 0.9300 1.365(2) 1.411(2) 1.365(2) 0.9300 0.9300 1.465(3) 1.502(3) 0.9700 0.9700 0.9600 0.9600 0.9600 1.464(2)
C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17)
1.501(3) 0.9700 0.9700 0.9600 0.9600 0.9600 1.473(2) 0.9600 0.9600 0.9600 1.361(2) 1.413(2) 1.7783(17) 1.354(3) 0.9300 1.417(2)
C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17)
0.9300 1.416(3) 1.417(2) 1.360(3) 0.9300 1.397(3) 0.9300 1.361(3) 0.9300 1.413(2) 0.9300 1.416(2) 0.9300 1.4454(13) 1.4446(13) 1.4423(13)
Table 3 Bond angles (°) for DESNS. Atoms
Angles
Atoms
Angles
Atoms
Angles
C(2)AC(1)AN(1) C(2)AC(1)AH(1) N(1)AC(1)AH(1) C(1)AC(2)AC(3) C(1)AC(2)AH(2) C(3)AC(2)AH(2) C(4)AC(3)AC(2) C(4)AC(3)AH(3) C(2)AC(3)AH(3) C(3)AC(4)AC(5) C(3)AC(4)AH(4) C(5)AC(4)AH(4) N(1)AC(5)AC(4) N(1)AC(5)AC(6) C(4)AC(5)AC(6) C(7)AC(6)AC(5) C(7)AC(6)AH(6) C(5)AC(6)AH(6) C(6)AC(7)AC(8) C(6)AC(7)AH(7) C(8)AC(7)AH(7) C(9)AC(8)AC(13) C(9)AC(8)AC(7) C(13)AC(8)AC(7) C(10)AC(9)AC(8) C(10)AC(9)AH(9) C(8)AC(9)AH(9) C(9)AC(10)AC(11) C(9)AC(10)AH(10) C(11)AC(10)AH(10) N(2)AC(11)AC(10) N(2)AC(11)AC(12) C(10)AC(11)AC(12) C(13)AC(12)AC(11) C(13)AC(12)AH(12) C(11)AC(12)AH(12) C(12)AC(13)AC(8)
121.61(18) 119.2 119.2 118.79(17) 120.6 120.6 119.65(18) 120.2 120.2 121.48(18) 119.3 119.3 116.83(15) 119.11(15) 124.06(16) 124.41(16) 117.8 117.8 126.79(16) 116.6 116.6 116.59(15) 120.20(15) 123.19(16) 122.25(16) 118.9 118.9 121.35(16) 119.3 119.3 121.73(16) 121.85(15) 116.42(15) 121.59(16) 119.2 119.2 121.79(16)
C(12)AC(13)AH(13) C(8)AC(13)AH(13) N(2)AC(14)AC(15) N(2)AC(14)AH(14A) C(15)AC(14)AH(14A) N(2)AC(14)AH(14B) C(15)AC(14)AH(14B) H(14A)AC(14)AH(14B) C(14)AC(15)AH(15A) C(14)AC(15)AH(15B) H(15A)AC(15)AH(15B) C(14)AC(15)AH(15C) H(15A)AC(15)AH(15C) H(15B)AC(15)AH(15C) N(2)AC(16)AC(17) N(2)AC(16)AH(16A) C(17)AC(16)AH(16A) N(2)AC(16)AH(16B) C(17)AC(16)AH(16B) H(16A)AC(16)AH(16B) C(16)AC(17)AH(17A) C(16)AC(17)AH(17B) H(17A)AC(17)AH(17B) C(16)AC(17)AH(17C) H(17A)AC(17)AH(17C) H(17B)AC(17)AH(17C) N(1)AC(18)AH(18A) N(1)AC(18)AH(18B) H(18A)AC(18)AH(18B) N(1)AC(18)AH(18C) H(18A)AC(18)AH(18C) H(18B)AC(18)AH(18C) C(28)AC(19)AC(20) C(28)AC(19)AS(1) C(20)AC(19)AS(1) C(21)AC(20)AC(19) C(21)AC(20)AH(20)
119.1 119.1 113.05(17) 109 109 109 109 107.8 109.5 109.5 109.5 109.5 109.5 109.5 112.81(16) 109 109 109 109 107.8 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 120.01(16) 121.62(12) 118.36(13) 120.31(16) 119.8
C(19)AC(20)AH(20) C(20)AC(21)AC(22) C(20)AC(21)AH(21) C(22)AC(21)AH(21) C(23)AC(22)AC(21) C(23)AC(22)AC(27) C(21)AC(22)AC(27) C(24)AC(23)AC(22) C(24)AC(23)AH(23) C(22)AC(23)AH(23) C(23)AC(24)AC(25) C(23)AC(24)AH(24) C(25)AC(24)AH(24) C(26)AC(25)AC(24) C(26)AC(25)AH(25) C(24)AC(25)AH(25) C(25)AC(26)AC(27) C(25)AC(26)AH(26) C(27)AC(26)AH(26) C(28)AC(27)AC(26) C(28)AC(27)AC(22) C(26)AC(27)AC(22) C(19)AC(28)AC(27) C(19)AC(28)AH(28) C(27)AC(28)AH(28) C(1)AN(1)AC(5) C(1)AN(1)AC(18) C(5)AN(1)AC(18) C(11)AN(2)AC(14) C(11)AN(2)AC(16) C(14)AN(2)AC(16) O(3)AS(1)AO(2) O(3)AS(1)AO(1) O(2)AS(1)AO(1) O(3)AS(1)AC(19) O(2)AS(1)AC(19) O(1)AS(1)AC(19)
119.8 121.15(16) 119.4 119.4 122.20(16) 119.07(17) 118.73(16) 120.30(19) 119.9 119.9 120.60(19) 119.7 119.7 120.86(19) 119.6 119.6 120.34(18) 119.8 119.8 122.50(15) 118.66(15) 118.83(16) 121.13(15) 119.4 119.4 121.57(15) 117.77(16) 120.66(14) 122.42(15) 121.77(16) 115.78(15) 112.70(8) 113.71(9) 112.78(8) 104.82(8) 105.69(8) 106.23(8)
packing, O atom of the sulfonate group is involved in weak CAH O hydrogen bond interactions. The cation is linked to the anion by weak CAH O interaction. The bond lengths and angles in this structure are in normal ranges and comparable with a related structure [19,20]. The crystallographic data of DESNS has been deposited with the Cambridge Crystallographic Data Centre [CCDC 966408]. Copies of the data can be obtained free of Charge at from the Cambridge
Crystallographic datacentre or www.ccdc.cam.ac.uk/data request/ cif. 3.2. Morphology The morphology of the DESNS has been simulated by the WinXMorph program [21], where the data obtained from the single crystal study (cif formate) were used as input in the WinXMorph
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crystal was measured experimentally by the floatation technique [22]. In this analysis, CCl4 was used for this measurement and the measured density can be calculated using the relation q = m0 qsolvent/(m0–m0 ) ..........(2), where m0 is the mass of the DESNS crystal in the air, m0 is the mass when the DESNS single crystal was immersed in CCl4 and qsolvent is the density of the solvent (CCl4). The experimentally calculated value is in good agreement with theoretically found value. The obtained density values are given below:
Theoritical : 1:303 g=cc: Experimental : 1:306 g=cc:
3.4. Powder X-ray diffraction analysis The powder X-ray diffraction pattern was carried out to identify the single phase nature of the crystal and reflection planes. Fig. 4 depicts the recorded powder diffractogram of the DESNS crystal. Powder refinement software was used for investigation of powder XRD pattern. From the diffraction data, the well-defined Bragg peaks obtained at specific 2h angles shows the good crystalline perfection of the DESNS crystal. 3.5. Fourier transform infrared spectroscopic analysis Fig. 2. (a) The molecular structure showing 30% probability displacement ellipsoids and the atom-numbering scheme. (b) Packing of the molecule shows partly viewed along the a-axis.
The density of pure DESNS crystals was calculated from a single crystal XRD data using the equation q = M Z/NA a b c..........(1), where M is the molecular weight of DESNS crystal, Z is the number of the molecule per unit cell; NA is the Avogadro’s number, and a, b and c are the cell parameters of DESNS crystal. The density of pure DESNS crystal was found to be 1.303 g/cc. The density of DESNS
The characteristic vibrations modes of molecules and functional groups present in the DESNS crystal were confirmed by using FT-IR spectrum is shows in Fig. 5. The vibration frequencies observed between 500 and 700 cm1 are due to the out of a plane bending of the ring CAH bonds and frequencies between 1100 and 1200 cm1 are corresponds to the plane ring conformation modes [23]. The peak at 3032 cm1 is ascribe to the CAH stretching mode. The peak at 2929.87 cm1 is due to the alkyl CAH stretch. The peaks that are observed at 1502.55–1591.27 cm1 is attributed to the aromatic ring vibrations. The sharp peak at 1629.85 cm1 is assigned for C@C stretch in the DESNS compound. The absorption peak at 1330.88 cm1 is ascribe to the CAN stretching mode. The peaks at 1153.43 and 1178.5 cm1 are pertaining to the S@O stretch modes of sulfonate group [24]. The absorption band at 962.48 cm1 establishes the 1, 2 substituted pyridinium ring. The observed peak at 813.96 cm1 is due to the para-substituted aromatic ring vibrations mode. Thus, this FT-IR transmission
Fig. 3. Morphology of DESNS crystal.
Fig. 4. Powder XRD diffraction of DESNS.
program. The grown crystals have well developed morphology with several habit faces are shown in Fig. 3. The result indicated that the growth rate is found to be greater along the a-axis. 3.3. Density measurements
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7.517 ppm, and 7.707 ppm is due to the four hydrogens of the naphthalene ring (m, 4HAC10 H7 SO3 + CH). The multiplet at 7.524 ppm is corresponding to the two hydrogens of the naphthalene ring (m, 2HAC10 H7 SO3). The singlet at 8.151 ppm is ascribing to the first place hydrogen of the naphthalene ring (C10 H7 SO3) [15]. Thus, the formation the title compound was confirmed by proton NMR spectral analysis. 3.7. Optical transmittance studies
Fig. 5. FTIR spectrum of DESNS.
spectrum confirms the overall molecular structure of the DESNS compound.
3.6. 1H NMR spectral analysis It is an important tool for the study of electronic structure and identification of particular nuclei present in the molecules. In the proton NMR spectrum (Fig. 6) of DESNS, the triplet peak at 1.129 ppm is due to the six hydrogens of C6H6ANA(CH2CH3)2. The quartet at 3.450 ppm is due to the four hydrogens of C6H6ANA(CH2CH3)2. The dissolving solvent DMSO-d6 may contain a small quantity of water it shows a chemical shift at 3.361 ppm. The singlet around 4.278 ppm is due to the three hydrogens of pyridinium NACH3. The doublets at 7.29 ppm and 7.732 ppm are due to the two olefinic hydrogens (CH@CH). The doublets at 7.654 ppm and 7.657 ppm are attributed to the four hydrogens of the NA(CH2CH3)2AC6H4 aromatic ring. The doublet at 8.443 ppm and 7.729 ppm is assigned to the third and fifth place hydrogens of the pyridinium ring. The doublet and triplet peak observed at 8.745 ppm, and 8.313 ppm is assigned to the six and fourth position hydrogen of the pyridinium ring. The multiplet found at
Fig. 6. 1H NMR spectrum of DESNS.
The optical transmittance range and the transparency cut off wavelength of single crystal are most significant optical parameters for laser frequency applications [25]. The absorption spectrum of DESNS in solid phases (2 mm thickness) is shown in Fig. 7. The spectrum gives two peaks, one at 275 nm is corresponds to n–p transition and another one maximum absorption peak value was found to be at 476 nm, which is corresponds to the extended system (donor-diethylamino to acceptor-pyridinium) involves a p–p transition through the conjugated system which causes the molecule absorb light in the visible range. The major absorption peak of the title compound in the visible region is good agreement with the stilbazolium chromophore with the unsaturated bond. Absence of absorption in the region between 476 and 1100 nm for this crystal suggests it is an essential requirement for optoelectronics applications. Two optical band gaps are calculated for these two transitions. The band gap corresponds to p–p transition is 2.50 eV, and n–p transition is 5.60 eV. As a result of wide band gap, the grown crystal has the large transmittance window in the UV–Vis–NIR region. 3.8. Thermal analysis Thermal stability was identified for the grown DESNS crystal by the thermo gravimetric analysis (TG/DTA) using the model NETZSCH STA 409 PL Luxx in a nitrogen atmosphere at a heating rate of 10 K/min in the temperature range room temperature to 500 °C. The resulting TG/DTA curves are shown in Fig. 8. The DTA curve shows one endothermic peak noticed at 226 °C which is assigned to the melting point of the crystal and also indicates that there is no phase transition before this temperature and a good degree crystallinity of the material. From the DTA curve, two exothermic peaks observed at 303 and 327 °C, which is attributed to the
Fig. 7. UV–Vis NIR spectrum of DESNS crystal.
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609
Fig. 8. TGA/DTA curve of DESNS.
complete decomposition stilbazolium ion from DESNS material. A very broad endothermic peak observed at 452 °C which is indicating total change in the physical state of the crystal. The TG curve shows that there are three stages of weight loss at three different temperatures. The first decomposition takes place at 226 °C this may be due to the removal of water and solvents. In the second stage, the major mass loss of 54.3% is observed in between 226 and 285 °C and third stage around 19% of the material decomposes in between 285 and 365 °C, which may be due to the SO3 group evolving out from DESNS. Finally, the residual mass remains at 499.4 °C are only 9.6%. Thus, these analyses indicate that the stability of the material could be used for the laser applications and fabrication of any optical devices below its melting point. 3.9. Mechanical studies The mechanical behavior of grown single crystal is strongly related to the molecular structure and material composition of the crystalline solids. Micro-hardness has been carried on crack free and optically clear surface of the grown crystal plate was subjected to indentation test. The statistical indentations were taken for different loads ranging from 10 to 100 g was used for making an indentation with a constant indentation time of 10 s in all cases at room temperature. The intended impression mark was the square shape when viewed under an optical microscope. The Vickers’s hardness number Hv of the crystal was calculated using the standard expression: 2
Hv ¼ 1:8544 ðP=d Þ kg=mm2 ;
Fig. 9. Variation of Hv (Vickers hardness) with load (P).
ð3Þ
where Hv is the Vickner hardness number in kg/mm2, P is the intender load in kg, and d is the average diagonal length of the indentation impression in mm. It is very clear from the Fig. 9 shows that Hv number increases up to 100 g, and then cracking occurs to develop further increase in applied load. This may be due to the internal stresses released during within the indentation. The relation between load and diagonal length of the indentation can be calculated from the Meyers law. P = kdn [26].
Log P ¼ log k þ n log d;
ð4Þ
where log k is the material constant and ‘n’ is the Meyer’s number or work hardening coefficient. The graph is plotted for log P versus log d (Fig. 10) yields a straight lie and its slope value give the value of n. The estimated value of ‘n’ for DESNS was found to be 2.70. According to Onitch Meyer’s index ‘n’ should lie between 1 and
Fig. 10. Graph between log d and log P.
1.6 for harder materials, and it is more than 1.6 for softer materials [27]. Thus, DESNS crystal suggests that the soft material category.
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4. Conclusion The stilbazolium derivative 2-[2-(4-Diethylamino-phenyl)-vinyl]-1-methyl-pyridinium naphthalene-2-sulfonate was synthesized and single crystal of DESNS has been grown by the slow evaporation technique at room temperature. The identity of the crystal structure was confirmed using single crystal X-ray diffraction technique, and the crystals belong to the orthorhombic system with Pbca space group. The density of DESNS crystals measured to be in agreement with theoretically calculated values. Powder X-ray diffraction studies reveal the good crystalline nature of the material. The modes of vibrations of the functional group were confirmed using FTIR spectral analysis. Proton NMR spectroscopic analysis confirms the formation of the grown crystal. The UV–Vis absorption study shows that DESNS has wide transparency in the entire Vis–NIR region. Thermal behavior of DESNS was studied by using TG/DTA analysis reveals that the purity of the sample and thermally stable up to the melting point. Vickers’s microhardness measurement proves that DESNS comes under the soft category of materials. Acknowledgements The authors are grateful to the management, Vellore Institute of Technology (VIT), Vellore for their constant encouragement and support and the Defence Research and Development Organization (DRDO), Govt. Of India for providing financial assistance under the Grant of Project Ref. No. ERIP/ER/1103929M/01/1402, is hereby duly acknowledged. References [1] Liang Li, Huijuan Cui, Zhou Yang, Xutang Tao, Xinsong Lin, Ning Ye, Ning Ye, Huai Yang, CrystEngComm 14 (2012) 1031. [2] Pumsak Ruanwas, Tawanrat Kobkeatthawin, Suchada Chantrapromma, HoongKun Fun, Reji Philip, N. Smijesh, Mahesh Padaki, Arun M. Isloor, Synth. Met. 160 (2010) 819–824.
[3] Jianhong Yin, Liang Li, Zhou Yang, Mojca Jazbinsek, Xutang Tao, Peter Günter, Huai Yang, Dyes Pigments 94 (2012) 120–126. [4] L.R. Dalton, P.A. Sullivan, Chem. Rev. 110 (2010) 25. [5] Peter Hrobarik, Ivica Sigmundova, Pavol Zahradnık, Peter Kasak, Vladimir Arion, Edith Franz, Koen Clays, J. Phys. Chem. C 114 (2010) 22289–22302. [6] O.P. Kwon, B. Ruiz, A. Choubey, L. Mutter, A. Schneider, M. Jazbinsek, P. Gunter, Chem. Mater. 18 (2006) 4049. [7] V. Alain, S. Redoglia, M. Blanchard-Desce, S. Lebus, K. Lukaszuk, R. Wortmann, U. Gubler, Ch. Bosshard, P. Gunter, Chem. Phys. 24 (1999) 51. [8] H. Kang, A. Facchetti, C.L. Stern, A.L. Rheingold, W.S. Kassel, T.J. Marks, Org. Lett. 7 (2005) 3721. [9] Eun-Young Choi, Mojca Jazbinsek, Jae-Hyeok Jeong, O-Pil Kwon, CrystEngComm 14 (2011) 1045. [10] T. Maeda, Y. Manabe, M. Yamamoto, M. Yoshida, K. Okazaki, H. Nagamune, H. Kourai, Chem. Pharm. Bull. 47 (1999) 1020–1023. [11] J. Pernak, J. Kalewska, H. Ksycifiska, J. Cybulski, Eur. J. Med. Chem. 36 (2001) 899–907. [12] Kullapa Chanawanno, Suchada Chantrapromma, Theerasak Anantapong, Akkharawit kanjana-Opas, Hoong-Kun Fun, Eur. J. Med. Chem. 45 (2010) 4199–4208. [13] Jean-Daniel Compain, Pierre Mialane, Anne Dolbecq, Jerome Marrot, Anna Proust, Keitaro Nakatani, Pei Yu, Francis Secheresse, Inorg. Chem. 48 (2009) 6222–6228. [14] L. Li, H. Cui, Z. Yang, X. Tao, X. Lin, N. Ye, H. Yang, CrystEngComm 14 (2012) 1031. [15] Blanca Ruiz, Zhou Yang, Volker Gramlich, Mojaca Jazbinsek, Peter Gunter, J. Mater. Chem. 16 (2006) 2839–2842. [16] Narissara Kaewmanee, Kullapa Chanawanno, Suchad Chantraprommaa, Hoong-Kun Fun, Acta Cryst. E66 (2010) o2639–o2640. [17] G.M. Sheldrick, Acta Cryst. A64 (2008) 112–122. [18] A.L. Spek, Acta Cryst. D 65 (2009) 148–155. [19] Suchada Chantrapromma, Narissara Kaewmanee, Nawong Boonnak, Teerasak Anantapong, Hoong-Kun Fun, Acta Cryst. E68 (2012) o2728–o2729. [20] M. Krishnakumar, S. Sudhahar, A. Silambarasan, G. Chakkaravarthi, R. Mohankumar, Acta Cryst. E68 (2012) o3268. [21] W. Kaminsky, J. Appl. Crystallogr. 40 (2007) 382. [22] A.F. Ioffe, Phys. Status Solidi A 116 (1989) 457. [23] J. Jerald Vijay, N. Melikechib, Tina Thomas, R. Gunaseelan, M. Antony Arockiaraja, P. Sagayaraj, J. Cryst. Growth 338 (2012) 170–176. [24] K. Jagannathan, S. Kalainathan, T. Gnanasekaran, V. Vijayan, G. Bhagavanarayana, Cryst. Growth Des. 7 (2007) 859–863. [25] C. Alosious Gonsago, Helen Merina Albert, R. Umamahe swari, A. Joseph Arul Pragasam, Indian J. Sci. Technol. 5 (2012) 3. [26] K. Jagannathan, S. Kalainathan, T. Gnanasekaran, Mater. Lett. 61 (2007) 4485– 4488. [27] E.M. Onitsch, Microskope 95 (1950) 12.
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Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa
Synthesis, growth, crystal structure, spectral, thermal, mechanical and optical studies of stilbazolium derivative single crystal: 2-[2-(4-Diethylamino-phenyl)-vinyl]-1-methyl-pyridinium naphthalene-2-sulfonate (DESNS) K. Senthil, S. Kalainathan ⇑, A. Ruban Kumar Centre for Crystal Growth, School of Advanced Sciences, VIT University, Vellore 632 014, Tamil Nadu, India
h i g h l i g h t s
g r a p h i c a l a b s t r a c t
DESNS single crystals with size of
15 10 9 mm3 were firstly grown by slow evaporation method. The crystal structure of DESNS for the first time in the literature. UV–Vis–NIR spectral analysis shows that grown crystal has good transparency window from 476 to 1100 nm. TG/DTA studies show that the compound is stable up to its melting point at 226 °C. Mechanical studies establish that the crystal is belongs to the soft material category.
a r t i c l e
i n f o
Article history: Received 5 November 2013 Received in revised form 24 December 2013 Accepted 8 January 2014 Available online 23 January 2014 Keywords: Organic compounds Crystal structure Single crystal growth Slow evaporation X-ray diffraction Micro-hardness
a b s t r a c t Single crystals of organic optical material, 2-[2-(4-Diethylamino-phenyl)-vinyl]-1-methyl-pyridinium naphthalene-2-sulfonate (DESNS) (15 10 9 mm3) were grown by a slow evaporation technique at room temperature using methanol–acetonitrile (1:1) mixed solvent. The molecular structure of the grown crystal was confirmed by single crystal X-ray diffraction studies, and it belongs to orthorhombic system with space group Pbca and the unit cell dimentions are a = 11.5148(3) Å, b = 15.4352(4) Å, c = 27.2187(7) Å, Z = 8. The crystallinity of the title crystals was confirmed from the powder XRD pattern. The presence of functional groups of the title crystal was confirmed from the FTIR spectral studies. The transparent range and cut off wavelength of the grown crystal was studied by the UV–Vis–NIR spectroscopic analysis. The mechanical properties and thermal behavior of the grown crystals were studied from Vickers microhardness test and TG/DTA. Ó 2014 Elsevier B.V. All rights reserved.
1. Introduction During the last three decades, the stilbazolium salts and many of the derivatives have been investigated for their large second ⇑ Corresponding author. Tel.: +91 416 2202350; fax: +91 416 2243092. E-mail address: [email protected] (S. Kalainathan). http://dx.doi.org/10.1016/j.saa.2014.01.064 1386-1425/Ó 2014 Elsevier B.V. All rights reserved.
order nonlinear optical responses [1]. In recent progress, a lot of attention has been given to polar organic crystals because of their various potential applications including nonlinear optical applications, laser frequency conversion, optical power limiting devices, optical storage technology, electro-optics, THz-wave generation and electric-field detection [2–4]. Organic p-conjugated systems are interesting because they exhibit large molecular quadratic
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hyperpolarizabilities, scope for altering the properties by changing electron donor and electron acceptor moieties at their two ends [5]. The formation of the carbon-carbon bridge (C@C) with p-conjugation chromospheres of an organic molecule of such materials, many reactions have been reported, such as Knoevenagel condensation, Suzuki coupling reaction, Wittig-Homer Emmons condensations among them particularly Knoevenagel condensation reaction most favorable and easy method for to form a carbon–carbon double bond [6–9]. However, the presence of styryl pyridinium compounds is being mainly used as antibacterial drugs, herbicides, environmental disinfection, disinfection in hospital environments and food industry due to their low toxicity to humans and animals [10–12]. The design of NLO chromophore crystals has an electron withdrawing group that bear an electron donating group interacting through the p-conjugated system with parallel alignment in the crystal structure [13]. In the recent years many efforts have been made to wide investigation by different research groups in the development of DSNS (4-N,N-dimethylamino-40 -N0 -methyl-stilbazolium naphthalene-2-sulfonate) and its derivatives crystals for their high and fast nonlinearity properties with 50% higher powder second harmonic generation (SHG) efficiency than that of the DAST crystal (4-N,N-dimethylamino-40 -N0 -methyl-stilbazolium tosylate) at a 1907 nm [14,15]. In this series, this is a derivative in the stilbazolium family and one of the new organic materials. This is the first article on the crystallization of DESNS. So far, we have extended our report in synthesis, growth, crystal structure, spectral, thermal, and mechanical study were also carried for DESNS single crystals.
2. Experimental procedure 2.1. Material synthesis and crystal growth DESNS compound was synthesized by the Knoevenagel condensation of 1, 2-dimethylpyridinium iodide, which was prepared from 2-picoline, iodomethane and p-diethylaminobenzaldehyde in the presence of piperidine as a catalyst. The overall synthesis process and molecular structures are shown in scheme 1. 1, 2-Dimethylpyridinium iodide 1 1, 2-Dimethylpyridinium Iodide 1 was prepared by equimolar ratio of 2-Picoline (2 ml, 20 mmol) and iodomethane (1.3 ml, 20 mmol) in acetone (30 ml). The mixtures were refluxed for 4 h and cooled to ambient temperature. The resulting white precipitates were collected by filtration, dried and melting point was found to be 155 °C. 2-[(E)-4-(diethyl amino) styryl]-1-methyl-pyridinium iodide 2 The title material (2) was synthesized according to the previously reported method [16]. To a solution of 1 (2.35 g 10 mmol) in hot methanol (30 ml), 4-diethylamino benzaldehyde (1.8 g 10 mmol), and piperidine (0.98 ml, 10 mmol) were added. Then the mixture solution was refluxed for 6 h under a dry nitrogen atmosphere. Once the reaction was complete, the purple precipitate was filtered off and washed with ether for removal of unreacted starting materials. The title compound 2 was purified by successive recrystallized from methanol (m.p. 256 °C).
Scheme 1. Synthesis of DESNS.
K. Senthil et al. / Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 124 (2014) 603–610
2-[2-(4-Diethylamino-phenyl)-vinyl]-1-methyl-pyridinium naphthalene-2-sulfonate (DESNS) 3 Compound 2 (3.9g10 mmol) was dissolved in equal volume of methanol-acetonitrile (40 ml) mixed solvent by heating and simultaneously, naphthalene-2-sulfonate (2.3 g 10 mmol) was dissolved in 20 ml of equal ratio of methanol-Millipore water by heating. The two hot solutions were mixed and further heated for 2 h at 80 °C and then mixer was cooled to ambient temperature. The resulting red color precipitate was filtered off and dried at 120 °C for 3 h to get free of water. The purity of DESNS was achieved by repeated recrystallization first from water, and then from methanol for removal of unreacted materials (m.p. 226 °C). Single crystal of title compounds was grown using slow evaporation technique. Initially, several organic solvents in pure and mixed forms solvents were investigated to know the growth habit of a title crystal, solvent such as methanol, ethanol, acetonitrile, chloroform, methanol– water, methanol–chloroform, and methanol–acetonitrile were dried. Finally, only in the combination of methanol–acetonitrile mixed solvent system was found to be suitable for the crystal formation was observed. A saturated solution of DESNS material was prepared at room temperature in methanol–acetonitrile (1:1) mixed solvent, and then solution was stirred continuously to obtain homogeneous medium by using a magnetic stirrer, and filtered the saturated solution into the beaker using Whatman filter paper with porosity 0.1 lm. After that beaker was tightly covered with aluminum foil, and then with few holes to control evaporation rate of the mixed solvent. Small transparent seed crystals were obtained over in a period of 3 days through spontaneous nucleation. After around 40 days, bulk size of DESNS single crystal with dimension up to 15 10 9 mm3 (Fig. 1) was harvested by defect free seed crystal applied to the saturated solution. 2.2. Characterization studies The grown crystal structure was investigated by single crystal X-ray diffraction analysis using a Bruker Kappa APEX II diffractometer (Mo Ka = 0.71073 Å). The structure was solved and full matrix least squares refinement by direct methods using SHELXS97 programs [17]. The plots of molecular graphics were created with the PLATON software [18]. The powder X-ray diffraction analysis were carried out by using BRUKER X-Ray diffractometer with the Cu Ka radiation (k = 1.5406 Å) in the range of 10–50°, in steps of 0.02°. The FT-IR spectrum was recorded using SHIMADZU IRAFFINITY instrument in the wavelength range of 400–4000 cm1 using the KBr pellet technique. Proton NMR spectrum was recorded
using BRUKER instrument operating with 400 MHz, and DMSO d6 was used as solvent at room temperature. The optical studies of DESNS crystal were carried out by using ELICO SL 218 double beam UV–Vis–NIR spectrometer in the wavelength region of 190–1100 nm. Thermal stability studies were carried out with TG/DTA instrument SBT Q600 apparatus in a nitrogen atmosphere. The mechanical behavior of DESNS single crystal was tested by employing MH-112 Micro-hardness instrument with Vickers indenter at room temperature.
3. Result and discussion 3.1. Single crystal X-ray diffraction analysis The new structure of DESNS crystal was determined from single crystal XRD analysis. From the single crystal XRD studies, it shows that DESNS belongs to the centrosymmetry crystal structure with orthorhombic crystal system and space group Pbca. Single crystal data and further details of the crystallography data collection and structural refinement results are summarized in Table 1. Selected lengths bond angles which are given in Tables 2 and 3. The asymmetric unit of the title compound (Fig. 2(a)) consists of a 2-[4-(diethyl amino) styryl]-1-methylpyridinium (C18 H23 N2+) cation, and a naphthalene sulfonate (C10 H7 O3 S) anion molecule. The packing of the molecule shows partly viewed along the a-axis as shown in (Fig. 2(b)). The 2-[4-(diethylamino) styryl]-1-methylpyridinium cation exists in an E configuration with respect to the C6@C7 double bond [1.334(2) Å]. The cation is slightly twisted, with the dihedral angle between the C1AC5/N1 pyridinium and C8AC13 benzene rings being 10.59 (6)°, and it possess trans configuration, which can be confirmed from the torsional angle C5AC6AC7AC8, 179.61(16)°. The cation and anion are inclined to each other which indicated by the dihedral angles between the C17AC22 sulfonated substituted benzene ring of anion and pyridinium and C8AC13 benzene rings of cation being 54.90 (10) and 59.90 (10)°, respectively. The two ethyl groups of diethylamino moiety are slightly twisted from the mean plane of the attached C8AC13 ring as indicated by the torsion angles C16AN2AC11A C12 = 5.21(3)° and C14AN2AC11AC10 = 9.1(3)°. In the crystal
Table 1 Crystal data structure refinement for 2-[2-(4-Diethylamino-phenyl)-vinyl]-1-methylpyridinium naphthalene-2-sulfonate (DESNS). Empirical formula Formula weight Temperature Wavelength Crystal system, space group Unit cell dimentions
Fig. 1. Photograph of DESNS crystal grown by slow evaporation.
605
Volume Z, Calculated density Absorption coefficient F (0 0 0) Crystal size Theta range for data collection Limiting indices Reflections collected/unique Completeness to theta = 25.00 Absorption correction Max. and min. transmission Refinement method Data/restraints/parameters Goodness-of-fit on F2 Final R indices [I > 2sigma (I)] R indices (all data) Largest diff. peak and hole
C28H30N2O3S 474.60 298(2) K 0.71073 Å Orthorhombic, Pbca a = 11.5148(3) Å a = 90° b = 15.4352(4) Å b = 90° c = 27.2187(7) Å c = 90° 4837.7(2) Å3 8, 1.303 Mg/m3 0.167 mm1 2016 0.20 0.18 0.15 mm 2.3229.36° 15 6 h 6 12, 21 6 k 6 18, 37 6 l 6 37 34372/6492 [R (int) = 0.0331] 99.8% None 0.9754 and 0.9674 Full-matrix least-squares on F2 6492/0/310 1.002 R1 = 0.0472, wR2 = 0.1039 R1 = 0.0969, wR2 = 0.1236 0.256 and 0.266 e Å3
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Table 2 Bond lengths [Å] for DESNS. Atoms
Length
Atoms
Length
Atoms
Length
Atoms
Length
Atoms
Length
C(1)AC(2) C(1)AN(1) C(1)AH(1) C(2)AC(3) C(2)AH(2) C(3)AC(4) C(3)AH(3) C(4)AC(5) C(4)AH(4) C(5)AN(1) C(5)AC(6) C(6)AC(7) C(6)AH(6) C(7)AC(8) C(7)AH(7) C(8)AC(9) C(8)AC(13)
1.347(3) 1.353(2) 0.9300 1.380(3) 0.9300 1.363(3) 0.9300 1.393(2) 0.9300 1.363(2) 1.442(2) 1.334(2) 0.9300 1.445(2) 0.9300 1.395(2) 1.401(2)
C(1)AC(2) C(1)AN(1) C(1)AH(1) C(2)AC(3) C(2)AH(2) C(3)AC(4) C(3)AH(3) C(4)AC(5) C(4)AH(4) C(5)AN(1) C(5)AC(6) C(6)AC(7) C(6)AH(6) C(7)AC(8) C(7)AH(7) C(8)AC(9) C(8)AC(13)
1.347(3) 1.353(2) 0.9300 1.380(3) 0.9300 1.363(3) 0.9300 1.393(2) 0.9300 1.363(2) 1.442(2) 1.334(2) 0.9300 1.445(2) 0.9300 1.395(2) 1.401(2)
C(9)AC(10) C(9)AH(9) C(10)AC(11) C(10)AH(10) C(11)AN(2) C(11)AC(12) C(12)AC(13) C(12)AH(12) C(13)AH(13) C(14)AN(2) C(14)AC(15) C(14)AH(14A) C(14)AH(14B) C(15)AH(15A) C(15)AH(15B) C(15)AH(15C) C(16)AN(2)
1.366(2) 0.9300 1.406(2) 0.9300 1.365(2) 1.411(2) 1.365(2) 0.9300 0.9300 1.465(3) 1.502(3) 0.9700 0.9700 0.9600 0.9600 0.9600 1.464(2)
C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17)
1.501(3) 0.9700 0.9700 0.9600 0.9600 0.9600 1.473(2) 0.9600 0.9600 0.9600 1.361(2) 1.413(2) 1.7783(17) 1.354(3) 0.9300 1.417(2)
C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17) C(16)AC(17)
0.9300 1.416(3) 1.417(2) 1.360(3) 0.9300 1.397(3) 0.9300 1.361(3) 0.9300 1.413(2) 0.9300 1.416(2) 0.9300 1.4454(13) 1.4446(13) 1.4423(13)
Table 3 Bond angles (°) for DESNS. Atoms
Angles
Atoms
Angles
Atoms
Angles
C(2)AC(1)AN(1) C(2)AC(1)AH(1) N(1)AC(1)AH(1) C(1)AC(2)AC(3) C(1)AC(2)AH(2) C(3)AC(2)AH(2) C(4)AC(3)AC(2) C(4)AC(3)AH(3) C(2)AC(3)AH(3) C(3)AC(4)AC(5) C(3)AC(4)AH(4) C(5)AC(4)AH(4) N(1)AC(5)AC(4) N(1)AC(5)AC(6) C(4)AC(5)AC(6) C(7)AC(6)AC(5) C(7)AC(6)AH(6) C(5)AC(6)AH(6) C(6)AC(7)AC(8) C(6)AC(7)AH(7) C(8)AC(7)AH(7) C(9)AC(8)AC(13) C(9)AC(8)AC(7) C(13)AC(8)AC(7) C(10)AC(9)AC(8) C(10)AC(9)AH(9) C(8)AC(9)AH(9) C(9)AC(10)AC(11) C(9)AC(10)AH(10) C(11)AC(10)AH(10) N(2)AC(11)AC(10) N(2)AC(11)AC(12) C(10)AC(11)AC(12) C(13)AC(12)AC(11) C(13)AC(12)AH(12) C(11)AC(12)AH(12) C(12)AC(13)AC(8)
121.61(18) 119.2 119.2 118.79(17) 120.6 120.6 119.65(18) 120.2 120.2 121.48(18) 119.3 119.3 116.83(15) 119.11(15) 124.06(16) 124.41(16) 117.8 117.8 126.79(16) 116.6 116.6 116.59(15) 120.20(15) 123.19(16) 122.25(16) 118.9 118.9 121.35(16) 119.3 119.3 121.73(16) 121.85(15) 116.42(15) 121.59(16) 119.2 119.2 121.79(16)
C(12)AC(13)AH(13) C(8)AC(13)AH(13) N(2)AC(14)AC(15) N(2)AC(14)AH(14A) C(15)AC(14)AH(14A) N(2)AC(14)AH(14B) C(15)AC(14)AH(14B) H(14A)AC(14)AH(14B) C(14)AC(15)AH(15A) C(14)AC(15)AH(15B) H(15A)AC(15)AH(15B) C(14)AC(15)AH(15C) H(15A)AC(15)AH(15C) H(15B)AC(15)AH(15C) N(2)AC(16)AC(17) N(2)AC(16)AH(16A) C(17)AC(16)AH(16A) N(2)AC(16)AH(16B) C(17)AC(16)AH(16B) H(16A)AC(16)AH(16B) C(16)AC(17)AH(17A) C(16)AC(17)AH(17B) H(17A)AC(17)AH(17B) C(16)AC(17)AH(17C) H(17A)AC(17)AH(17C) H(17B)AC(17)AH(17C) N(1)AC(18)AH(18A) N(1)AC(18)AH(18B) H(18A)AC(18)AH(18B) N(1)AC(18)AH(18C) H(18A)AC(18)AH(18C) H(18B)AC(18)AH(18C) C(28)AC(19)AC(20) C(28)AC(19)AS(1) C(20)AC(19)AS(1) C(21)AC(20)AC(19) C(21)AC(20)AH(20)
119.1 119.1 113.05(17) 109 109 109 109 107.8 109.5 109.5 109.5 109.5 109.5 109.5 112.81(16) 109 109 109 109 107.8 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 109.5 120.01(16) 121.62(12) 118.36(13) 120.31(16) 119.8
C(19)AC(20)AH(20) C(20)AC(21)AC(22) C(20)AC(21)AH(21) C(22)AC(21)AH(21) C(23)AC(22)AC(21) C(23)AC(22)AC(27) C(21)AC(22)AC(27) C(24)AC(23)AC(22) C(24)AC(23)AH(23) C(22)AC(23)AH(23) C(23)AC(24)AC(25) C(23)AC(24)AH(24) C(25)AC(24)AH(24) C(26)AC(25)AC(24) C(26)AC(25)AH(25) C(24)AC(25)AH(25) C(25)AC(26)AC(27) C(25)AC(26)AH(26) C(27)AC(26)AH(26) C(28)AC(27)AC(26) C(28)AC(27)AC(22) C(26)AC(27)AC(22) C(19)AC(28)AC(27) C(19)AC(28)AH(28) C(27)AC(28)AH(28) C(1)AN(1)AC(5) C(1)AN(1)AC(18) C(5)AN(1)AC(18) C(11)AN(2)AC(14) C(11)AN(2)AC(16) C(14)AN(2)AC(16) O(3)AS(1)AO(2) O(3)AS(1)AO(1) O(2)AS(1)AO(1) O(3)AS(1)AC(19) O(2)AS(1)AC(19) O(1)AS(1)AC(19)
119.8 121.15(16) 119.4 119.4 122.20(16) 119.07(17) 118.73(16) 120.30(19) 119.9 119.9 120.60(19) 119.7 119.7 120.86(19) 119.6 119.6 120.34(18) 119.8 119.8 122.50(15) 118.66(15) 118.83(16) 121.13(15) 119.4 119.4 121.57(15) 117.77(16) 120.66(14) 122.42(15) 121.77(16) 115.78(15) 112.70(8) 113.71(9) 112.78(8) 104.82(8) 105.69(8) 106.23(8)
packing, O atom of the sulfonate group is involved in weak CAH O hydrogen bond interactions. The cation is linked to the anion by weak CAH O interaction. The bond lengths and angles in this structure are in normal ranges and comparable with a related structure [19,20]. The crystallographic data of DESNS has been deposited with the Cambridge Crystallographic Data Centre [CCDC 966408]. Copies of the data can be obtained free of Charge at from the Cambridge
Crystallographic datacentre or www.ccdc.cam.ac.uk/data request/ cif. 3.2. Morphology The morphology of the DESNS has been simulated by the WinXMorph program [21], where the data obtained from the single crystal study (cif formate) were used as input in the WinXMorph
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crystal was measured experimentally by the floatation technique [22]. In this analysis, CCl4 was used for this measurement and the measured density can be calculated using the relation q = m0 qsolvent/(m0–m0 ) ..........(2), where m0 is the mass of the DESNS crystal in the air, m0 is the mass when the DESNS single crystal was immersed in CCl4 and qsolvent is the density of the solvent (CCl4). The experimentally calculated value is in good agreement with theoretically found value. The obtained density values are given below:
Theoritical : 1:303 g=cc: Experimental : 1:306 g=cc:
3.4. Powder X-ray diffraction analysis The powder X-ray diffraction pattern was carried out to identify the single phase nature of the crystal and reflection planes. Fig. 4 depicts the recorded powder diffractogram of the DESNS crystal. Powder refinement software was used for investigation of powder XRD pattern. From the diffraction data, the well-defined Bragg peaks obtained at specific 2h angles shows the good crystalline perfection of the DESNS crystal. 3.5. Fourier transform infrared spectroscopic analysis Fig. 2. (a) The molecular structure showing 30% probability displacement ellipsoids and the atom-numbering scheme. (b) Packing of the molecule shows partly viewed along the a-axis.
The density of pure DESNS crystals was calculated from a single crystal XRD data using the equation q = M Z/NA a b c..........(1), where M is the molecular weight of DESNS crystal, Z is the number of the molecule per unit cell; NA is the Avogadro’s number, and a, b and c are the cell parameters of DESNS crystal. The density of pure DESNS crystal was found to be 1.303 g/cc. The density of DESNS
The characteristic vibrations modes of molecules and functional groups present in the DESNS crystal were confirmed by using FT-IR spectrum is shows in Fig. 5. The vibration frequencies observed between 500 and 700 cm1 are due to the out of a plane bending of the ring CAH bonds and frequencies between 1100 and 1200 cm1 are corresponds to the plane ring conformation modes [23]. The peak at 3032 cm1 is ascribe to the CAH stretching mode. The peak at 2929.87 cm1 is due to the alkyl CAH stretch. The peaks that are observed at 1502.55–1591.27 cm1 is attributed to the aromatic ring vibrations. The sharp peak at 1629.85 cm1 is assigned for C@C stretch in the DESNS compound. The absorption peak at 1330.88 cm1 is ascribe to the CAN stretching mode. The peaks at 1153.43 and 1178.5 cm1 are pertaining to the S@O stretch modes of sulfonate group [24]. The absorption band at 962.48 cm1 establishes the 1, 2 substituted pyridinium ring. The observed peak at 813.96 cm1 is due to the para-substituted aromatic ring vibrations mode. Thus, this FT-IR transmission
Fig. 3. Morphology of DESNS crystal.
Fig. 4. Powder XRD diffraction of DESNS.
program. The grown crystals have well developed morphology with several habit faces are shown in Fig. 3. The result indicated that the growth rate is found to be greater along the a-axis. 3.3. Density measurements
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7.517 ppm, and 7.707 ppm is due to the four hydrogens of the naphthalene ring (m, 4HAC10 H7 SO3 + CH). The multiplet at 7.524 ppm is corresponding to the two hydrogens of the naphthalene ring (m, 2HAC10 H7 SO3). The singlet at 8.151 ppm is ascribing to the first place hydrogen of the naphthalene ring (C10 H7 SO3) [15]. Thus, the formation the title compound was confirmed by proton NMR spectral analysis. 3.7. Optical transmittance studies
Fig. 5. FTIR spectrum of DESNS.
spectrum confirms the overall molecular structure of the DESNS compound.
3.6. 1H NMR spectral analysis It is an important tool for the study of electronic structure and identification of particular nuclei present in the molecules. In the proton NMR spectrum (Fig. 6) of DESNS, the triplet peak at 1.129 ppm is due to the six hydrogens of C6H6ANA(CH2CH3)2. The quartet at 3.450 ppm is due to the four hydrogens of C6H6ANA(CH2CH3)2. The dissolving solvent DMSO-d6 may contain a small quantity of water it shows a chemical shift at 3.361 ppm. The singlet around 4.278 ppm is due to the three hydrogens of pyridinium NACH3. The doublets at 7.29 ppm and 7.732 ppm are due to the two olefinic hydrogens (CH@CH). The doublets at 7.654 ppm and 7.657 ppm are attributed to the four hydrogens of the NA(CH2CH3)2AC6H4 aromatic ring. The doublet at 8.443 ppm and 7.729 ppm is assigned to the third and fifth place hydrogens of the pyridinium ring. The doublet and triplet peak observed at 8.745 ppm, and 8.313 ppm is assigned to the six and fourth position hydrogen of the pyridinium ring. The multiplet found at
Fig. 6. 1H NMR spectrum of DESNS.
The optical transmittance range and the transparency cut off wavelength of single crystal are most significant optical parameters for laser frequency applications [25]. The absorption spectrum of DESNS in solid phases (2 mm thickness) is shown in Fig. 7. The spectrum gives two peaks, one at 275 nm is corresponds to n–p transition and another one maximum absorption peak value was found to be at 476 nm, which is corresponds to the extended system (donor-diethylamino to acceptor-pyridinium) involves a p–p transition through the conjugated system which causes the molecule absorb light in the visible range. The major absorption peak of the title compound in the visible region is good agreement with the stilbazolium chromophore with the unsaturated bond. Absence of absorption in the region between 476 and 1100 nm for this crystal suggests it is an essential requirement for optoelectronics applications. Two optical band gaps are calculated for these two transitions. The band gap corresponds to p–p transition is 2.50 eV, and n–p transition is 5.60 eV. As a result of wide band gap, the grown crystal has the large transmittance window in the UV–Vis–NIR region. 3.8. Thermal analysis Thermal stability was identified for the grown DESNS crystal by the thermo gravimetric analysis (TG/DTA) using the model NETZSCH STA 409 PL Luxx in a nitrogen atmosphere at a heating rate of 10 K/min in the temperature range room temperature to 500 °C. The resulting TG/DTA curves are shown in Fig. 8. The DTA curve shows one endothermic peak noticed at 226 °C which is assigned to the melting point of the crystal and also indicates that there is no phase transition before this temperature and a good degree crystallinity of the material. From the DTA curve, two exothermic peaks observed at 303 and 327 °C, which is attributed to the
Fig. 7. UV–Vis NIR spectrum of DESNS crystal.
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Fig. 8. TGA/DTA curve of DESNS.
complete decomposition stilbazolium ion from DESNS material. A very broad endothermic peak observed at 452 °C which is indicating total change in the physical state of the crystal. The TG curve shows that there are three stages of weight loss at three different temperatures. The first decomposition takes place at 226 °C this may be due to the removal of water and solvents. In the second stage, the major mass loss of 54.3% is observed in between 226 and 285 °C and third stage around 19% of the material decomposes in between 285 and 365 °C, which may be due to the SO3 group evolving out from DESNS. Finally, the residual mass remains at 499.4 °C are only 9.6%. Thus, these analyses indicate that the stability of the material could be used for the laser applications and fabrication of any optical devices below its melting point. 3.9. Mechanical studies The mechanical behavior of grown single crystal is strongly related to the molecular structure and material composition of the crystalline solids. Micro-hardness has been carried on crack free and optically clear surface of the grown crystal plate was subjected to indentation test. The statistical indentations were taken for different loads ranging from 10 to 100 g was used for making an indentation with a constant indentation time of 10 s in all cases at room temperature. The intended impression mark was the square shape when viewed under an optical microscope. The Vickers’s hardness number Hv of the crystal was calculated using the standard expression: 2
Hv ¼ 1:8544 ðP=d Þ kg=mm2 ;
Fig. 9. Variation of Hv (Vickers hardness) with load (P).
ð3Þ
where Hv is the Vickner hardness number in kg/mm2, P is the intender load in kg, and d is the average diagonal length of the indentation impression in mm. It is very clear from the Fig. 9 shows that Hv number increases up to 100 g, and then cracking occurs to develop further increase in applied load. This may be due to the internal stresses released during within the indentation. The relation between load and diagonal length of the indentation can be calculated from the Meyers law. P = kdn [26].
Log P ¼ log k þ n log d;
ð4Þ
where log k is the material constant and ‘n’ is the Meyer’s number or work hardening coefficient. The graph is plotted for log P versus log d (Fig. 10) yields a straight lie and its slope value give the value of n. The estimated value of ‘n’ for DESNS was found to be 2.70. According to Onitch Meyer’s index ‘n’ should lie between 1 and
Fig. 10. Graph between log d and log P.
1.6 for harder materials, and it is more than 1.6 for softer materials [27]. Thus, DESNS crystal suggests that the soft material category.
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4. Conclusion The stilbazolium derivative 2-[2-(4-Diethylamino-phenyl)-vinyl]-1-methyl-pyridinium naphthalene-2-sulfonate was synthesized and single crystal of DESNS has been grown by the slow evaporation technique at room temperature. The identity of the crystal structure was confirmed using single crystal X-ray diffraction technique, and the crystals belong to the orthorhombic system with Pbca space group. The density of DESNS crystals measured to be in agreement with theoretically calculated values. Powder X-ray diffraction studies reveal the good crystalline nature of the material. The modes of vibrations of the functional group were confirmed using FTIR spectral analysis. Proton NMR spectroscopic analysis confirms the formation of the grown crystal. The UV–Vis absorption study shows that DESNS has wide transparency in the entire Vis–NIR region. Thermal behavior of DESNS was studied by using TG/DTA analysis reveals that the purity of the sample and thermally stable up to the melting point. Vickers’s microhardness measurement proves that DESNS comes under the soft category of materials. Acknowledgements The authors are grateful to the management, Vellore Institute of Technology (VIT), Vellore for their constant encouragement and support and the Defence Research and Development Organization (DRDO), Govt. Of India for providing financial assistance under the Grant of Project Ref. No. ERIP/ER/1103929M/01/1402, is hereby duly acknowledged. References [1] Liang Li, Huijuan Cui, Zhou Yang, Xutang Tao, Xinsong Lin, Ning Ye, Ning Ye, Huai Yang, CrystEngComm 14 (2012) 1031. [2] Pumsak Ruanwas, Tawanrat Kobkeatthawin, Suchada Chantrapromma, HoongKun Fun, Reji Philip, N. Smijesh, Mahesh Padaki, Arun M. Isloor, Synth. Met. 160 (2010) 819–824.
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