Role of Anions in Inducing Noncentrosymmetry in 4

Growth and characterization of dexterous nonlinear optical material: Dimethyl amino pyridinium 4-nitrophenolate 4-nitrophenol (DMAPNP). M. Saravanan...
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CRYSTAL GROWTH & DESIGN 2006 VOL. 6, NO. 6 1285-1290

Articles Role of Anions in Inducing Noncentrosymmetry in 4-Dimethylaminopyridinium Salts for Quadratic Nonlinear Optics S. Manivannan,† S. Dhanuskodi,*,† K. Kirschbaum,‡ and S. K. Tiwari§ Department of Physics, Bharathidasan UniVersity, Tiruchirappalli 620 024, India, Department of Chemistry, UniVersity of Toledo, Toledo, Ohio 43606, and Laser Physics DiVision, Centre for AdVanced Technology, Indore 452 013, India ReceiVed June 10, 2005; ReVised Manuscript ReceiVed October 2, 2005

ABSTRACT: A novel organic nonlinear optical material 4-dimethylaminopyridinium L-tartrate dihydrate (DMAPT‚2H2O) (C11H16N2O6‚2H2O) was synthesized and characterized by CHN elemental analysis, FT-NMR, FT-IR, and FT-Raman spectral studies. Single crystals of average dimensions 15 × 2 × 2 mm3 were grown by the solvent evaporation method from an aqueous solution at pH 3.60 at constant temperature (30 °C). The crystal structure was solved by the single-crystal X-ray diffraction method and belongs to the orthorhombic, noncentrosymmetric space group P212121 with unit cell dimensions of a ) 7.2903(5) Å, b ) 11.7980(7) Å, c ) 16.2981(10) Å, and Z ) 4. Thermogravimetry (TG) and differential thermal analysis (DTA) showed that the compound decomposes at 75 °C. The optical transmittance window was found to be 310-1100 nm. The Kurtz and Perry powder test illustrates the phase matching property of DMAPT‚2H2O, and the powder second harmonic generation efficiency is 1.13 times greater than that of KDP. The laser induced surface damage threshold for the grown crystal was measured as 9.72 GW/cm2 with a Nd:YAG laser assembly. 1. Introduction The nonlinear optical response of a material is ultimately governed by the optical characteristics of molecular chromophores, the frequencies of the input radiation, and the overall special organization that can be imposed upon large ensembles of these constituents.1-4 The challenge faced by researchers in this emerging field is the identification of new types of functional materials by rational construction of molecular assemblies exhibiting nonlinear optical effects. An added difficulty of this task is the fulfilment of secondary requirements such as thermal, mechanical, and chemical stabilities in addition to the ease of growth in the case of single crystals.5 Researchers follow various strategies to bring out suitable materials such as formation of metal complexes and salts or introduction of steric effects and hydrogen-bonding interactions.6 Among these, the formation of salts plays a vital role, owing to the ease of growth, synthetic flexibility anchored into various organic and inorganic host subnetworks. The main role of the subnetwork is to induce noncentrosymmetry in the bulk and to enhance thermal and mechanical stability through H-bonding interactions.7,8 Based on this, 4-dimethylaminopyridinium dihydrogen phosphate (DMAPDP), 4-dimethylaminopyridinium chloride dihy* Corresponding author. Telephone: +91 431 2407057. Fax: +91 431 2407045. e-mail: [email protected]. † Bharathidasan University. ‡ University of Toledo. § Centre for Advanced Technology.

drate (DMAPCl‚2H2O), and 4-dimethylaminopyridinium bromide dihydrate (DMAPBr‚2H2O) were synthesized. The synthesized materials were used for the Kurtz and Perry powder second harmonic generation (SHG) test revealing a centrosymmetric arrangements of these molecules. It was found that the anions play a major role in the formation of salts in inducing the noncentrosymmetry in the crystal, since the molecular symmetry in 4-dimethylaminopyridine (DMAP) needs suitable anionic subnetworks for the noncentrosymmetric arrangements. One of the ways to achieve this is to introduce a chiral center in the anionic host, for which L-tartaric acid was chosen, so 4-dimethylaminopyridinium L-tartrate dihydrate (DMAPT‚ 2H2O) was successfully synthesized for the first time. In this paper, we report the synthesis, structural, thermal, and optical properties of DMAPT‚2H2O. Further, the syntheses of DMAPDP, DMAPCl‚2H2O, and DMAPBr‚2H2O are also briefly presented. 2. Experimental Section 2.1. Synthesis and Crystal Growth of DMAPT‚2H2O. DMAP is a weak Brønsted base that gains a proton in acidic aqueous solution and forms the salt of the respective acid. DMAPT‚2H2O was synthesized from the readily available organic materials DMAP and L-tartaric acid. The reaction was carried out in water at 65 °C by mixing DMAP and L-tartaric acid in an equimolar ratio. The mixture was stirred well for 2 h, and a clear solution was obtained. Then the solution was kept at 45 °C in a water bath, resulting in a white microcrystalline organic salt. The synthesized material was then purified by repeated recrys-

10.1021/cg050262i CCC: $33.50 © 2006 American Chemical Society Published on Web 04/13/2006

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Figure 1. Solubility curve for DMAPT‚2H2O in water. Figure 3. Laser induced surface damage threshold for DMAPT‚2H2O. analysis observed (calculated for C7H13N2PO4): %C ) 38.36 (38.19), %H ) 5.95 (5.95), %N ) 12.32 (12.72).

3. Material Characterization

Figure 2. Grown single crystals of DMAPT‚2H2O. tallization in triple-distilled water. The recrystallized compound was used for single-crystal growth by the solvent evaporation technique. The solubility of DMAPT‚2H2O in triple-distilled water was determined in the temperature range 25-55 °C and is illustrated in Figure 1. The positive temperature gradient in the solubility curve is favorable for crystal growth; hence the single crystals were grown from aqueous solution at 30 °C using a constant-temperature bath having a control accuracy of (0.01 °C. The pH of the solution was kept at 3.60, and needle-shaped transparent single crystals (Figure 2) of average dimensions 15 × 2 × 2 mm3 were obtained after a typical growth period of 10 days. 2.2. Synthesis of DMAPCl‚2H2O, DMAPBr‚2H2O, and DMAPDP. DMAPCl‚2H2O was prepared by reacting DMAP with HCl in the molar ratio 1:1.5. The reaction was carried out at 60 °C in aqueous solution for 3 h. On cooling crystalline powder was isolated. 1 H NMR (D2O, δ from TMS): 7.88 (d, 2H), 6.75 (d, 2H), 3.11 (s, 6H), 4.75 (s, H2O). 13C NMR (D2O, ppm) 156.451, 143.307, 106.33, 40.268. FT-IR:3455, 2949, 1645, 1065 cm-1. Elemental analysis observed (calculated for C7H11N2Cl‚2H2O): %C ) 42.77 (43.19), %H ) 7.89 (7.76), %N ) 15.82 (14.39). DMAPBr‚2H2O was synthesized from DMAP reacting with HBr in an equimolar ratio for 5 h at 60 °C in aqueous solution. On cooling, crystalline precipitation was found and isolated. 1H NMR (D2O, δ from TMS): 7.89 (d, 2H), 6.58 (d, 2H), 2.94 (s, 6H), 4.75 (s, H2O). 13C NMR (D2O, ppm): 157.78, 145.301, 108.333, 40.208. FT-IR: 3450, 2936, 1647, 1063 cm-1. Elemental analysis observed (calculated for C7H11N2Br‚2H2O): %C ) 36.04 (35.16), %H ) 7.11 (6.32), %N ) 12.27 (11.72). In a similar way, DMAPDP was obtained by reacting DMAP and orthophosphoric acid in an equimolar ratio. 1H NMR (D2O, δ from TMS): 7.95 (d, 2H), 6.85 (d, 2H), 3.17 (s, 6H). 13C NMR (D2O, ppm):140.867, 109.507, 42.051. FT-IR: 3386, 2943, 1646, 1086, 539, 448 cm-1. Elemental

3.1. General Methods. FT-IR spectra were recorded on a Jasco FT-IR 460 plus spectrometer following the KBr pellet technique at 300 K in the range 400-4000 cm-1. FT-Raman spectra were recorded using a Bruker RFS 100/S spectrometer with a powder sample at 300 K in the range 400-4000 cm-1. 13C and 1H NMR spectra were obtained with a Bruker 200 MHz NMR spectrometer at 300 K. Thermogravimetric (TG) and differential thermal analyses (DTA) were carried out using a Seiko instrument between the temperatures 40-800 °C at a heating rate of 20 °C/min in an atmosphere of air. The DMAPT‚ 2H2O sample weighing 5.936 mg was taken for measurements, and an inert substance, R-alumina (5.936 mg), was kept as reference material. The UV-vis spectra were recorded in aqueous solution using a Schimadzu UV-vis spectrophotometer in the range 200-1100 nm. The quadratic nonlinear optical (NLO) property of DMAPT‚2H2O was confirmed, and the SHG efficiency in the powdered form was measured following the Kurtz and Perry powder method.9 The synthesized crystalline powder sample was graded using standard sieves (Aimil instrumentation test sieves) for particle sizes in the range 300 µm. The detailed experimental setup for this measurement has been reported by Manivannan et al.10 The single-shot laser induced surface damage threshold of the grown crystal DMAPT‚2H2O was measured using a Q-switched Nd:YAG laser (1064 nm, 18 ns, 1 Hz) developed by the Centre for Advanced Technology (CAT), Indore, India. The laser beam was focused to a spot size of 123 µm. The combination of a polarizer and the transmission filters serves to adjust the input intensity to the required level. A photodiode was used to identify the pulse-to-pulse variation of the laser beam. The crystal was placed on a rotating mount and kept slightly away from the focal spot of the beam. The laser was made incident on the (001) plane and the scattered second harmonic signal from the crystal was collected using a collecting lens and monitored by a monochromator, photomultiplier tube (PMT), and CRO assembly. During experiments to measure oneon-one (P1) damage resistance values, the laser was operated by a remote control. The occurrence of damage (or otherwise)

Synthesis and Optical Properties of DMAPT‚2H2O

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Table 1. Crystal Data and Structure Refinement for DMAPT‚2H2O empirical formula formula weight temperature wavelength crystal system, space group unit cell dimensions volume Z, calculated density absorption coefficient F(000) crystal size θ range for data collection limiting indices reflections collected/unique completeness to θ refinement method data/restraints/parameters goodness of fit on F2 final R indices [I > 2σ(I)] R indices (all data) absolute structure parameter largest diffraction peak and hole

C11H20N2O8 308.29 120(2) K 0.710 73 Å orthorhombic, P212121 a ) 7.2903(5) Å b ) 11.7980(7) Å c ) 16.2981(10) Å 1401.82(15) Å3 4, 1.461 g/cm3 0.125 mm-1 656 0.40 × 0.38 × 0.32 mm3 2.13-28.30° -9 e h e 9, -15 e k e 14, -15 e l e 21 11118/3482 [R(int) ) 0.0378] 28.30 (99.9%) full-matrix least squares on F2 3482/0/270 1.181 R1 ) 0.050, wR2 ) 0.101 R1 ) 0.057, wR2 ) 0.103 0.3(12) 0.305 and -0.295 e‚Å-3

was monitored on the CRO, and irrespective of whether the damage had occurred, the sample was moved to a new site. The distance between the two sites was so kept at least 5 times the spot size on the crystal surface. Thus, the possible cumulative effect was avoided, which will reduce the actual damage resistance value of the crystal. By plotting the SHG output (mV) against energy (mJ) of the incident beam (Figure 3), the power density for surface damage threshold was calculated. The experiment was repeated for many samples of the same crystal, and the average was taken for calculations. 3.2. X-ray Crystal Structure Determination. The unit cell parameters and the crystal structure were determined from the single-crystal X-ray diffraction data obtained with a three-circle Bruker platform diffractometer (graphite-monochromated, Mo KR ) 0.710 73 Å). The data were collected at 120 K using an Oxford Cryostream 600 low-temperature device. The data were integrated using SAINT 6.45A;11 correction for absorption and decay was applied using SADABS.12 All calculations were performed using SHELXTL 6.10.13 The structure was solved by direct methods, and full-matrix least-squares refinements were performed on F2 using all unique reflections. All non-hydrogen atoms were refined with anisotropic atomic displacement parameters, and hydrogen atoms were refined with isotropic displacement factors. Drawings of the molecular structure and the packing diagram were obtained using DIAMOND 3.0c.14 The crystal data, experimental conditions, and structural refinement parameters are presented in Table 1. CCDC 271648 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/data_request/cif, by e-mailing [email protected], or by contacting The Cambridge Crystallographic Data Centre, 12, Union Road, Cambridge CB2 1EZ, UK (fax: +44 1223 336033). 4. Results and Discussion Among the four synthesized salts, DMAPT‚2H2O and DMAPDP are stable and the rest are hygroscopic. The morphology of DMAPT‚2H2O was identified by the single-crystal X-ray diffraction method and is shown in Figure 4. The indices of the major growth facets are shown, and the length of the crystal is found to lie along the a-axis. It is observed that the growth

Figure 4. Single-crystal morphology of DMAPT‚2H2O. Table 2. Infrared and Raman Spectral Band Assignments of DMAPT‚2H2O at Room Temperature exptl wavenumber (cm-1) and intensitya FT-IR FT-Raman 3319 (s) 3104 (m) 3066 (m) 2940 (m) 1644 (s) 1563 (s) 1404 (s) 1336 (m) 1305 (s) 1263 (s) 1215 (s) 1134 (m) 1067 (m) 903 (w) 819 (m) 743 (w)

2941 (w) 1641 (w) 1556 (w) 1448 (w) 1309 (w) 1252 (w) 1211 (w) 1053 (s) 891 (m) 751 (s)

vibration modeb and bond types ν(N-H) H bonded ν(C-H) or ν(O-H) H bonded ν(C-H) ν(C-H)/ν(O-H) δ(N-H) ν(CdC)/ν(COO-) ν(COO-) ν(COO-) δ(C-H) δ(C-H) δ(C-H) ν(C-O)/δ(C-H) ν(C-O) ν(C-C) π(C-H) π(C-H)

a

(s), strong; (m), medium; (w), weak. b ν, stretching; δ, bending (or) deformation in-plane; π, bending out-of-plane.

rate along the a-direction (which is the shortest crystallographic axis) is higher than that along the other axes. The CHN percentage composition was established by elemental analysis and the elements observed (calculated) are %C ) 44.71 (42.86), %H ) 7.39 (5.23), and %N ) 9.24 (9.09). The tentative assignments of FT-IR and FT-Raman (Table 2) are based on comparison with the FT-IR spectra of tartaric acid and DMAP. 13C NMR spectroscopy reveals for each of the five chemically nonequivalent carbon atoms sharp peaks except for the infrequent coincidence of dimethyl carbons with the DMSO (solvent) carbons; no impurities were detected. The low-intensity peak at δ ) 175.0 ppm is originated by the carbon atoms of the carboxylate groups, while the small peak at δ ) 156.9 ppm accounts for the ipso carbon attached to the dimethylamino group. Aromatic carbon atoms cause the medium peaks at δ ) 138.61 and 106.64 ppm. The chiral carbon atoms in the tartrate anion give rise to a large peak at δ ) 72.45 ppm. The 1H NMR spectrum recorded in D2O shows only the signals originated by the DMAP protons; carboxylic and hydroxyl protons of tartrate do not cause any resonance signal due to rapid exchange interactions. The two doublets at δ ) 7.87, 7.91 and 6.75, 6.78 ppm are originated by the DMAP ring protons. The presence of dimethyl group gives rise to a signal at δ ) 3.09 ppm. The signal δ ) 4.75 ppm is due to the water molecules in the synthesized salt.15 Physical and chemical properties of DMAPT‚2H2O and its reaction products as a function of temperature were studied by TG and DTA. The material is stable up to 75 °C, at which the decomposition starts. A weight loss around 12% between 75-180 °C is attributed to the loss of lattice water molecules (2H2O). Because the loss is seen to occur in two different stages, the water molecules should be located in the lattice with different bonding forces. The differential thermogram shows similar results of the dehydration. A sharp endothermic peak at 189 °C corresponds to the melting point. The sharpness of the peak confirms the good crystallinity of the synthesized material. A

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Figure 7. Molecular structure of DMAPT‚2H2O.

Figure 5. Optical transmittance of DMAPT‚2H2O.

Table 3. Selected Bond Lengths [Å] and Angles [deg] for DMAPT‚2H2O O(1)-C(8) O(2)-C(8) O(3)-C(9) O(3)-H(30) O(4)-C(10) O(4)-H(40) O(5)-C(11) O(6)-C(11) O(6)-H(60)

Figure 6. Particle size dependence of the SHG output of DMAPT‚ 2H2O.

major weight loss (88%) starts around 200 °C and ends at 800 °C, at which the material is completely decomposed. From the UV-vis spectrum (Figure 5), no remarkable absorption was found in the entire visible region of the spectrum, and the lower cutoff wavelength occurs at 310 nm. The transmittance window (310-1100 nm) is sufficient for the generation of second harmonic light from the Nd:YAG laser (λ ) 1064 nm). The second-order NLO property of DMAPT‚2H2O was studied following the Kurtz and Perry powder technique. The intensity of the SHG output as a function of particle size was measured and is plotted in Figure 6. From the figure it is noted that the SHG output increases with respect to the range of particle sizes (r), since all the particles in the laser beam are effectively phase matched while the number of particles in the light path decreases inversely with r. As r becomes larger than the average coherence length, the SHG output reaches saturation, indicating the phase matchable character of DMAPT‚2H2O. This is because some particles in the light path should have the correct orientation for phase matching, whereas, for a nonphase matchable crystalline powder material, the second harmonic intensity shows an increase with particle size up to the average coherence length, followed by a slow decrease with increasing average particle size. The results are compared with pulverized KDP, and the average powder SHG efficiency was found to be 1.13 times greater than that of KDP. Further, the laser induced

C(9)-O(3)-H(30) C(10)-O(4)-H(40) C(11)-O(6)-H(60) H(71O)-O(7)-H(720) H(81O)-O(8)-H(820) C(1)-N(1)-C(5) C(1)-N(1)-H(1N) C(5)-N(1)-H(1N) C(3)-N(2)-C(7) C(3)-N(2)-C(6) C(7)-N(2)-C(6) N(2)-C(6)-H(63) H(61)-C(6)-H(63) H(62)-C(6)-H(63) N(2)-C(7)-H(71) N(2)-C(7)-H(72) H(71)-C(7)-H(72) N(2)-C(7)-H(73) H(71)-C(7)-H(73)

Bond Lengths (Å) 1.238(2) N(1)-H(1N) 1.267(2) N(2)-C(7) 1.414(3) N(2)-C(6) 0.77(3) C(8)-C(9) 1.418(3) C(9)-C(10) 0.74(5) C(9)-H(9) 1.221(2) C(10)-C(11) 1.292(2) C(10)-H(10) 1.01(3) Bond Angles (deg) 110(2) H(72)-C(7)-H(73) 109(4) O(1)-C(8)-O(2) 113.5(18) O(1)-C(8)-C(9) 105(3) O(2)-C(8)-C(9) 112(3) O(3)-C(9)-C(10) 121.0(2) O(3)-C(9)-C(8) 119(3) C(10)-C(9)-C(8) 121(3) O(3)-C(9)-H(9) 121.54(19) C(10)-C(9)-H(9) 122.00(18) C(8)-C(9)-H(9) 116.34(19) O(4)-C(10)-C(11) 110.5(17) O(4)-C(10)-C(9) 99(3) C(11)-C(10)-C(9) 96(2) O(4)-C(10)-H(10) 114(2) C(11)-C(10)-H(10) 107(2) C(9)-C(10)-H(10) 115(3) O(5)-C(11)-O(6) 113(2) O(5)-C(11)-C(10) 100(3) O(6)-C(11)-C(10)

0.97(5) 1.463(3) 1.467(3) 1.537(3) 1.529(3) 0.89(2) 1.526(3) 0.95(2)

108(3) 126.65(18) 118.35(18) 114.97(18) 109.48(16) 112.08(17) 109.22(17) 109.1(14) 111.7(14) 105.2(14) 110.23(17) 109.94(16) 111.96(17) 111.5(13) 106.5(14) 106.6(13) 126.01(18) 118.72(18) 115.27(17)

surface damage threshold was measured as 9.72 GW/cm2. A direct comparison of the results becomes impossible as the testing conditions, such as wavelength and pulse widths, are different. It can easily be seen that longer pulses prevent any thermal relaxation, thereby reducing the damage resistance. However, it is compared with a few known inorganic NLO crystals [BBO (2.6 GW/cm2 at 1064 nm, 10 ns, 10 Hz), KDP (14.4 GW/cm2, 1064 nm, 12 ns), ADP (6.4GW/cm2, 1064 nm, 12 ns)] and organic 3-methyl-4-nitropyridine-1-oxide (POM) (10.5 GW/cm2, 1064 nm, 20 ns).16,17 From the single crystal structure analysis, it is found that DMAPT‚2H2O crystallizes in P212121, a noncentrosymmetric space group, with four formula units in the unit cell. A formula unit consists of one C7H11N2+ cation, one C4H5O6- anion, and two H2O molecules connected through an extensive H-bonding network. Since all hydrogen atoms could be located in the difference Fourier syntheses and isotropically refined, the protonation site could be unambiguously identified at the pyridine nitrogen N(1). The molecular structure is shown in Figure 7; significant bond parameters are presented in Table 3. Figures 8 and 9 illustrate the packing of the molecules in the solid-state structure. Tartrate and water molecules connect

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the neighboring water molecule and the protonated DMAP [O(7)-H(720)‚‚‚O(1)′, 1.88(3); N(1)-H(1N)‚‚‚O(1)′, 2.13(5) Å]. As shown in Figure 9, this protonated site of the cation is connected to the tartrate/water sheets through another bifurcated H-bond to one of the two water molecules (N(1)-H(1N)‚‚‚O(8), 2.22(5) Å) and to the carboxylate group of the tartrate (N(1)-H(1N)‚‚‚O(1)′, 2.13(5) Å). Also, the π-π stacking is observed in the structure. The Cg-Cg distance is noted as 4.2727(14) Å, the interplanar distance is 3.574 Å, and the angle is 30.14°. More importantly, it is noted that the chiral centers in the tartrate anion exert significant influences on the crystal packing (Figure 9) by forcing a noncentrosymmetric crystal lattice which is essential for second-order NLO. 5. Conclusion

Figure 8. Hydrogen-bonded tartrate/water sheet in DMAPT‚2H2O.

Figure 9. Crystal packing of DMAPT‚2H2O along the a-axis.

through H-bonds, forming zigzag sheets parallel to (001). The pyridinium molecules bond to these sheets in an almost perpendicular arrangement as evidenced by a dihedral angle of 86.7(1)° between the pyridinium molecule and the carbon skeleton of the tartrate ion. All O, O-H, and N-H groups are involved in the extensive hydrogen-bonding network giving rise to the relatively high density of 1.461 g/cm3. The hydrogen-bonding scheme of the tartrate/water sheets is complex and consists of several different unsymmetrical ring systems connected through O-H‚‚‚O or N-H‚‚‚O bonds. The two crystallographically independent water molecules are involved in three [O(7)-H(710)‚‚‚O(3)′′ (′′: -x - 1, y - 1/2, -z + 1/2), 1.97(3); O(7)-H(720)‚‚‚O(1)′ (′: -x, y - 1/2, -z + 1/2), 1.88(3); O(4)-H(40)‚‚‚O(7), 2.13(5) Å] and four [O(8)-H(810)‚‚‚O(4), 1.90(3); O(8)-H(820)‚‚‚O(5)′′′ (′′′: x + 1, y, z), 1.86(4); O(3)-H(30)‚‚‚O(8)IV (IV: -x, y + 1/2, -z + 1/2); 2.03(3); N(1)-H(1N)‚‚‚O(8), 2.22(5) Å] hydrogen bonds, respectively. Even considering only the intermolecular hydrogen bonds, we find both hydroxyl groups of the tartrate ion acting as donor and acceptor, simultaneously: O(3)-H(30)‚‚‚O(8)IV, 2.03(3); O(7)-H(710)‚‚‚O(3)′′, 1.97(3); O(4)-H(40)‚‚‚O(7), 2.13(5); O(8)-H(810)‚‚‚O(4), 1.90(3) Å. Further, one of the carboxylate oxygen atoms in the tartrate ion forms a bifurcated H-bond with

DMAPT‚2H2O only crystallizes in a noncentrosymmetric space group P212121, while the other salts show centrosymmetric arrangements in this series. The architecture of introducing asymmetry in the molecular level to break the centrosymmetry in the crystal through synthesis is noticeable in this new series. The crystal structure of DMAPT‚2H2O clearly illustrates the critical role played by the chiral centers prohibiting a centrosymmetric arrangement of the molecules, which implies the chiral group could be profitably used as a crystal design element in the fabrication of suitable molecular materials for quadratic NLO applications. The optical transmittance window in the whole visible and down to UV (310-1100 nm) region, the powder SHG efficiency (1.13 times greater than that of KDP), and the relatively large laser induced surface damage threshold (9.72 GW/cm2) are found to be added advantages of the organic DMAPT‚2H2O. Acknowledgment. The authors thank Prof. K. Panchanatheswaran (Department of Chemistry, Bharathidasan University, Tiruchirappalli) for his valuable suggestions. The authors acknowledge the College of Arts & Science at the University of Toledo and the Ohio Board of Regents for financial support of the crystallographic facilities at the University of Toledo. The authors are grateful to Dr. K. C. Rustagi and Dr. S. C. Mehendale (Laser Physics Division, Centre for Advanced Technology, Indore) for showing interest in this work. The authors are thankful to Prof. S. Umapathy (Department of Inorganic and Physical Chemistry, Indian Institute of Science, Bangalore) for his kind help with FT-Raman spectra. S.M. is thankful to the Council of Scientific and Industrial Research (CSIR), New Delhi, for the award of SRF (File No. 9/475(120)/ 2004-EMR-I dated June 28, 2004). References (1) Marcy, H. O.; Rosker, M. J.; Warren, L. F.; Cunningham, P. H.; Thomas, C. A.; DeLoach, L. A.; Velsko, S. P.; Ebbers, C. A.; Liao, J. H.; Kanatzidis, M. G. Opt. Lett. 1995, 20 (3), 252-254. (2) Dhanuskodi, S.; Vasantha, K. Cryst. Res. Technol. 2004, 39 (3), 259-265. (3) Comoretto, D.; Dellepiane, G.; Cuniberti, C.; Rossi, L.; Borghesi, A.; Le Moigne, J. Phys. ReV. B 1996, 53 (23), 15653-15659. (4) Becker, P. AdV. Mater. 1998, 10 (13), 979-992. (5) Chen, C.; Ye, N.; Lin, J.; Jiang, J.; Zeng, W.; Wu, B. AdV. Mater. 1999, 11 (13), 1071-1078. (6) Chemla, D. S.; Zyss, J. Nonlinear Optical Properties of Organic Molecules and Crystals; Academic Press: Orlando, 1987; Vols. 1 and 2. (7) Criado, A.; Dianez, M. J.; Garrido, S. P.; L Fernandes, I. M.; Belsley, M.; E. de Gomes, M. Acta Crystallogr., Sect. C 2000, 56, 888-889. (8) Zaccaro, J.; Salvestrini, J. P.; Ibanez, A.; Ney, P.; Fontana, M. D. J. Opt. Soc. Am. B 2000, 17 (3), 427-432.

1290 Crystal Growth & Design, Vol. 6, No. 6, 2006 (9) Kurtz, S. K.; Perry, T. T. J. Appl. Phys. 1968, 39, 3798-3813. (10) Manivannan, S.; Tiwari, S. K.; Dhanuskodi, S. Solid State Commun. 2004, 132, 123-127. (11) SAINT 6.45A; Bruker AXS Inc.: Madison, WI, 2003. (12) Sheldrick, G. M. SADABS; Universita¨t Go¨ttingen: Go¨ttingen, 1999. (13) Sheldrick, G. M.; SHELXTL, version 6.10; Bruker AXS Inc.: Madison, WI, 2000. (14) Brandenburg, K. DIAMOND 3.0c; Crystal Impact GbR, 2005.

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