Potassium Lithium Hydrogen Phthalate Mixed Crystals

Potassium Lithium total heat Phthalate Mixed Crystals3. RESULTS AND countersignSECTION 3.1Synthesis, growth, structure and characterization of thousand lithium heat content phthalate abstruse crystals*In the present work, we answer for the growth and structure of a new coalesce crystal C16H16KLiO11 (PLHP), which cryst whollyizes in a non-centrosymmetric station free radical P21 and SHG-active. The grown crystals were subjected to various characterization studies which are briefly described below. Here it is established that by synthesising the combine crystal in a different bridle-path with a controlled concentration of additive, one can make nonlinearity at the macro level by allowing the specimen to crystallise in a polar property group. The main objective of the investigation is to design a noncentrosymmetric structure by attempting a different course of synthesis, leading to NLO activity. Steering to noncentrosymmetry from centrosymmetry is made possible by changing the growth conditions.3.1.1. Crystal growthThe mixed crystal PLHP was synthesized from an sedimentary solution containing equimolar quantities of AR grade potassium hydrogen phthalate (KHP) and lithium blowate (Li2CO3) in slightlyacidic conditions using de-ionized water. After successive recrystallization, the mixed crystals were grown by the slow dehydration solution growth technique. The crystallization took place within 20-25 d and the crystals were harvested. Photographs of as- grown crystals are shown in Fig. 3.1.1.Fig. 3.1.1. Photographs of mixed crystal PLHP 3.1.2. FT-IRThe FT-IR spectrum of the as-grown specimen is shown in Fig.3.1.2. An absorption band in the region 500-900 cm-1 corresponds to the C-H out of plane deformations of rosyolent(p) ring. The C=O stretching frequency appeared at 1670 cm-1. The characteristic vibrational patterns of KHP104, lithium hydrogen phthalate (LiHP) 22 and PLHP are given(p) in submit 3.1.2. A slight shift of some of the characterist ic vibrational frequencies could be due to the stress development because of Li internalization. Fig. 3.1.2. FTIR spectrum of mixed crystal PLHPTable 3.1.2. FT-IR frequencies of some acid phthalate crystals (cm-1)aRef 105 bRef 22 c Present study3.1.3. TGA/DTAThermal studies reveal the righteousness of the material. The TGA curve shows a star stage weight outlet at 150o C due to loss of water molecule. In DTA, the broad end oppositemic peak at 420C, is dueto de report. The residual mass detect from thermogram at 600C is 50%. (Fig. 3.1.3).3.1.4. SEM / EDSThe SEM micrographs give information about the uprise morphology and it is employ to check the imperfections105. The SEM pictures of PLHP at different magnifications are shown in Fig. 3.1.4.1. It shows highest surface roughness in a main office like structure, due to defect centers and crystal voids. The bitch of Li and K in the PLHP crystal radiator grille is confirmed by energy dispersive spectroscopy (EDS) (Fig. 3.1.4.2) .Fig. 3.1.4.2. EDS spectrum of PLHP3.1.5. AAS and CHN analysisAtomic absorption spectroscopic studies were carried out to quantify Li (20.6 ppm) and K (21. ppm ) in the sample. Also, CHN elemental analysis was performed to estimate the quantity of carbon and hydrogen present in PLHP. The elemental composition found was C 42.93%, H 3.29%. The calculated composition was C 44.63%, H 3.7%.3.1.6. UV-visibleThe UV-visible spectrum of the mixed crystal PLHP reveals high transmittance in the visible region and the debase cut-off wave length is observed at 300 nm. Incorporation of foreign surface ion into the KHP crystal grillwork does not destroy the optical transmission of potassium hydrogen phthalate. The concentration of an absorbing species can be determined using the Kubelka-Munk equation106 correlating reflectance and concentration,F(R) = (1-R)2 / 2R = / s=Ac / swhere F(R) is Kubelka-Munk function, R is the reflectance of the crystal, is absorption coefficient, s is scattering c oefficient, A is absorbance and c is concentration of the absorbing species. The direct band-gap energy of the specimen is estimated as 4.05 eV, from the Tauc plan F(R)h2 versus h (eV) (Fig. 3.1.6).Fig. 3.1.6. Tauc plot (Direct Band gap energy)3.1.7 roentgen ray diffraction analysisThe powder XRD pattern of PLHP shows that the sample is of a single phase without a detectable impurity. Narrow peaks indicate the good crystallinity of the material. At room temperature all the observed reflections were indexed. The indexed powder XRD pattern is shown in Fig. 3.1.7.1. Peak positions in powder XRD match with simulated XRD patterns from single crystal X-ray diffraction. The relative intensity variations could be due to the preferred orientation of the sample employ for diffractogram measurement. Also, the mosaic spread of powder and single crystal patterns may differ, resulting in intensity variations. The structure of PLHP is elucidated and the ORTEP is given as Fig. 3.1.7.2. Three-dim ensional expression of intra molecular hydrogen stick toing interactions is displayed in Fig. 3.1.7.3. The chemical formula C16H16KLiO11 confirms the presence of K and Li in the crystalline matrix, well supported by energy dispersive X-ray spectroscopy (EDS) and atomic absorption spectroscopy (AAS). The specimen crystallizes in the monoclinic crystal system with the noncentrosymmetric property group P21. The crystallographic parameters of PLHP, KHP, LiKP and LiHP are listed in Table 3.1.7.1.Fig.3.1.7.1. Experimental (red) and simulated (blue) powder XRD patterns Fig.3.1.7.2. ORTEP of PLHPFig.3.1.7.3. Three dimensional view of intramolecular hydrogen attach interactions (OHO)Table 3.1.7.1. Crystal data of LiHP, KHP, LiKP and PLHP crystalsThe alkali ions are linked to individually other by OHO hydrogen bonds through the process oxygen. The O atoms of the carboxylate group (in phthalate ions) namely O(1)-O(8) are connected to K1, while the lithium ions are connected with central metal ion via O(5)-O(6), O atoms of the water molecules. The K-O bond distances range from 2.8311 (19) to 3.207 (8) , which is higher than bond distances observed in potassium hydrogen phthalate monohydrate 2.305 (1) 2.597 (1) . The LiO bond distances lie in the range 1.956 (3)1.968 (3) . The aromatic C-C bond distances fall in the range 1.377 (3) 1.485 (2) . The four carboxy C-O distances are almost same and the values are close to that observed for potassium hydrogen phthalate monohydrate107 and sodium acid phthalate108. In LiKP, O(4)K(1) bond distance lies at 2.7491 whereas in our present study, the O(4)K(1) bond distance is 2.7671 . The selected bond angles and bond lengths are given in Table 3.1.7.2.Crystal packing with hydrogen hold fast interactions along the b-axis is given in Fig. 3.1.7.4. Strong intramolecular hydrogen bonding interactions are O(2)-H(2)O(11) and O(5)-H(5B)O(3) assembled with distances of 1.77 and 1.86 individually (Fig. 3.1.7.5). Weak intermolecular i nteractions are observed for O(7)-H(7B)O(10), O(7)-H(7B)O(11) and O(5)-H(5B)O(1), with bond distances of 2.41 (2), 2.46 (3) and 3.25 (4) respectively (Table 3.1.7.3.).Table 3.1.7.2. Selected bond lengths () and angles (o) of PLHPTable 3.1.7.3. Hydrogen bonds geometry for PLHP , oFig. 3.1.7.5. Three dimensional image of polyhedron withO-HO interactions3.1.8. SHG efficiencyIn order to confirm the influence of incorporation of lithium on the NLO properties of KHP the pure and mixed crystals were subjected to SHG test with an input radiation of 6.5 mJ/pulse. The outputs give the relative SHG efficiencies of the measurable specimens. As seen, the SHG activity of the mixed crystal is comparable with that of KHP (Fig. 3.1.8) and it is quite likely due to the facile charge transfer, not disturbed by Li-incorporation. Although many materials cod been identified that have higher molecular nonlinearities, the progression of second-order effects requires favourable alignment of the molecul e within the crystal109. It has been reported that the SHG can be greatly richen by altering the molecular alignment through inclusion complexation110. The mixed crystal PLHP grown from an aqueous solution containing equimolar quantities of reactants crystallize in a noncentrosymmetric space group P21 and SHG-active, whereas when Li is taken in unnecessary in the growth medium the formed mixed crystal LiKP crystallizes in a centrosymmetric space group P1 and hence SHG-inactive29. It is interesting to observe that the mixed crystal of KHP synthesized by a different route crystallises in a polar space group. By changing the growth conditions it is possible to attain noncentrosymmetry in preference to centrosymmetry, a required characteristic of an NLO material.Fig. 3.1.8. The comparative SHG oscilloscope traces of the powder samples of KHP (red) and PLHP (blue)3.1.9. Hirshfeld surface analysisThe Hirshfeld surfaces of PLHP have been demonstrated in Fig. 3.1.9.1 by showing dnorm, sh ape index, de and di. The Hirshfeld surface111-113 surrounding a molecule is defined by points where the contribution to the electron density from the molecule under consideration is equal to the contribution from all the other molecules. For each point on that isosurface, two distances are determined one is de representing the distance from the point to the nearby nucleus external to the surface and second one is di, representing the distance to the nearest nucleus internal to the surface. The normalized tie-in distance (dnorm) is based on both de and di. The surfaces are shown as transparent to allow visualization of the molecule around which they were calculated. The circular depressions (deep red) which are visible on the Hirshfeld surface are an indicator of hydrogen bonding contacts and other visible spots in Fig. 3.1.9.1a are due to OLi (3.6%), HO (14.5%), OH (15.9%), KO (2.0%) and LiO (3.5%) interactions. The short interactions represented by deep red spots in de surface ( Fig.3.1.9.1c) are OLi contacts (3.6%). The dominant OH (14.5%), LiO (3.5%) and HH (31.7%) interactions are viewed in di surface plots by the bright red area in Fig. 3.1.9.1d. The shape index indicates the shape of the electron density surface around the molecular interactions. The small range of area and light color on the surface represent a weaker and longish contact other than hydrogen bonds. The two-dimensional fingerprint plots114 of PLHP exemplify the strong evidence for the intermolecular interactions pattern. In the fingerprint region (Fig. 3.1.9.3), OH (15.9%) interactions are represented by a spike in the posterior area whereas the HO (14.5%) interactions are represented by a spike in the travel by left region. Hydrogen-hydrogen interactions HH (31.7%) are very high while compared to the other bonding interactions. Sharp curved spike at the bottom left area indicates the OLi (3.6%) and top left corner with curved spike indicates the LiO (3.5%). The finger print at the b ottom right area represents CH (11.7%) interactions and top right area represents HC (8.7%) interactions. The issuance of interactions in terms of percentage are represented in a pie chart in Fig. 3.1.9.2.Fig.3.1.9.1. Hirshfeld surface analysis of PLHP (a) dnorm(b) shape index (c) de (d) diFig. 3.1.9.2. Relative contribution of various intermolecular interactions in PLHP Fig. 3.1.9.3. Fingerprint plots of PLHP1